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MICROBIOLOGY HANDBOOK DAIRY PRODUCTS Edited by Rhea Fernandes
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This edition first published 2008 by Leatherhead Publishing, a division of Leatherhead Food International Ltd Randalls Road, Leatherhead, Surrey KT22 7RY, UK URL: http://www.leatherheadfood.com and Royal Society of Chemistry Thomas Graham House, Science Park, Milton Road, Cambridge, CB4 0WF, UK URL: http://www.rsc.org Regstered Charity No. 207890
ISBN: 978-1-905224-62-3
A catalogue record of this book is available from the British Library
© 2009 Leatherhead Food International Ltd
The contents of this publication are copyright and reproduction in whole, or in part, is not permitted without the written consent of the Chief Executive of Leatherhead International Limited. Leatherhead International Limited uses every possible care in compiling, preparing and issuing the information herein given but accepts no liability whatsoever in connection with it.
All rights reserved Apart from any fair dealing for the purposes of research or private study, or criticism or review as permitted under the terms of the UK Copyright, Designs and Patents Act, 1988, this publication may not be reproduced, stored or transmitted, in any form or by any means, without the prior permission in writing of the Chief Executive of Leatherhead International Ltd, or in the case of reprographic reproduction only in accordance with the terms of the licences issued by the Copyright Licencing Agency in the UK, or in accordance with the terms of the licences issued by the appropriate Reproduction Rights Organization outside the UK. Enquiries concerning reproduction outside the terms stated here should be sent to Leatherhead International Ltd at the address printed on this page.
Printed and bound by Biddles Ltd., King’s Lynn
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FOREWORD The Microbiology Handbook series includes Dairy Products, Fish and Seafood, and Meat Products, published by Leatherhead Food International and RSC Publishing. They are designed to provide easy-to-use references to the microorganisms found in foods. Each book provides a brief overview of the processing factors that determine the nature and extent of microbial growth and survival in the product, potential hazards associated with the consumption of a range of products, and growth characteristics for key pathogens associated with the product. All handbooks also contain a review of the related legislation in Europe and UK, guides to HACCP, and a detailed list of contacts for various food authorities. The books are intended to act as a source of information for microbiologists and food scientists working in the food industry and responsible for food safety, both in the UK and elsewhere. Acknowledgements The contributions of all members of staff at Leatherhead Food International who were involved with writing and reviewing the previous editions of this book are thankfully acknowledged. In the production of this edition, I would like to especially thank Dr Peter Wareing, Training Manager at Leatherhead Food International, for his valuable input into the book. His vast experience of food industry, and in specific ‘food safety’, has been priceless. I would also like to acknowledge Victoria Emerton, team leader for the technical team at Leatherhead Food International, for her careful editing; Eugenia Choi in our regulatory team who provided the update on legislation; Catherine Hill in our publications department for typesetting; and Ann Pernet for indexing. Finally, I am grateful to my parents, (late) Gabriel and Ana Fernandes, for all their encouragement and support over the years.
Rhea Fernandes Leatherhead Food International
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CONTENTS
FOREWORD INTRODUCTION
v xi
1.
LIQUID MILK PRODUCTS 1.1 Definitions 1.2 Initial Microflora 1.3 Processing and its Effects on the Microflora 1.4 Other Methods of Treating Milk 1.5 Filling and Packaging 1.6 Spoilage 1.7 Pathogens: Growth and Survival 1.8 References
1 1 1 3 7 8 8 10 15
2.
CONCENTRATED AND DRIED MILK PRODUCTS 2.1 Definitions 2.2 Initial Microflora 2.3 Processing and its Effects on the Microflora 2.4 Spoilage 2.5 Pathogens: Growth and Survival 2.6 References
21 21 22 22 28 30 33
3.
CREAM 3.1 Definitions 3.2 Initial Microflora 3.3 Processing and its Effects on the Microflora 3.4 Processing of Other Creams 3.5 Spoilage 3.6 Pathogens: Growth and Survival 3.7 References
37 37 38 38 41 42 43 46
4.
BUTTER AND DAIRY SPREADS 4.1 Definitions 4.2 Initial Microflora 4.3 Processing and its Effects on the Microflora 4.4 Spoilage 4.5 Pathogens: Growth and Survival 4.6 References
49 49 49 50 55 56 57
5.
CHEESE 5.1 Definitions 5.2 Initial Microflora 5.3 Processing and its Effects on the Microflora 5.4 Processed Cheese 5.5 Value-added Cheese 5.6 Spoilage
61 61 62 62 67 67 67
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69 74
6.
FERMENTED MILKS 6.1 Definitions 6.2 Lactic Fermentations 6.3 Yeast - Lactic Fermentations 6.4 Mould - Lactic Fermentations 6.5 Initial Microflora 6.6 Processing and its Effects on the Microflora 6.7 Probiotic Products 6.8 Spoilage 6.9 Pathogens: Growth and Survival 6.10 Probiotic Products 6.11 References
77 77 77 80 80 81 81 84 85 86 89 89
7.
ICE CREAM AND RELATED PRODUCTS 7.1 Definitions 7.2 Initial Microflora 7.3 Processing and its Effects on the Microflora 7.4 Distribution 7.5 Spoilage 7.6 Pathogens: Growth and Survival 7.7 Toxins 7.8 References
91 91 92 92 98 98 99 101 101
8.
HACCP 8.1 Introduction 8.2 Definitions 8.3 Stages of a HACCP Study 8.4 Implementation and Review of the HACCP Plan 8.5 References
103 103 103 104 113 114
9.
EU FOOD HYGIENE LEGISLATION 117 9.1 Introduction 117 9.2 Legislative Structure 118 9.3 Regulation (EC) No. 852/2004 on the General Hygiene of Foodstuffs 119 9.4 Regulation (EC) No. 853/2004 Laying Down Specific Hygiene Rules for Food of Animal Origin 123 9.5 Regulation (EC) No. 854/2004 of the European Parliament and of the Council Laying Down Specific Rules for the Organisation of Official Controls on Products of Animal Origin Intended for Human Consumption 130 9.6 Regulation (EC) No. 2073/2005 on Microbiological Criteria for Foodstuffs 130 9.7 Food Hygiene (England) Regulations 2006, S.I. 2006 No. 14 (Hygiene requirements specific to the UK) 139 9.8 Guidance 141 9.9 References 141
10
PATHOGEN PROFILES 10.1 Bacillus cereus 10.2 Campylobacter spp. 10.3 Clostridium botulinum 10.4 Clostridium perfringens 10.5 Cronobacter (Enterobacter) sakazakii 10.6 Escherichia coli 0157 10.7 Listeria spp. 10.8 Salmonella spp.
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143 143 145 145 147 148 149 150 151
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10.9 Staphylococcus aureus 10.10 Yersinia enterocolitica 10.11 References
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152 154 155
CONTACTS
163
INDEX
167
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INTRODUCTION Milk and dairy products form a significant part of the human diet. They are rich sources of nutrients such as proteins, fats, vitamins and minerals; ironically, it is because of this that these products are susceptible to rapid microbial growth. In some instances, this microbial growth may be beneficial, while in others it is undesirable. Dairy products are vulnerable to spoilage or contamination with pathogens or microbial toxins; therefore, the microbiology of these products is of key interest to those in the dairy industry. The Microbiology Handbook- Dairy Products consists of the microbiology of seven different dairy product categories: liquid milk products; concentrated and dried milk; cream, butter and spreads; cheese; fermented milks; and ice cream and frozen desserts, as well as HACCP. The third edition of this handbook provides a thorough review of the entire book for currency of information. Key changes in this edition are the recent regulatory changes pertaining to food hygiene and microbiological criteria for foodstuffs, and an emerging pathogen Cronobacter sakazakii (formerly known as Enterobacter sakazakii). This change in name was implemented in 2008, therefore all references published prior to 2008 will refer to the organism as E. sakazakii. Further Reading McSweeney P.L.H. The microbiology of cheese ripening, in Cheese Problems Solved. Ed. McSweeney P.L.H. Cambridge, Woodhead Publishing Ltd. 2007, 117-32. Tamine A.Y., Robinson R.K. Microbiology of yoghurt and related starter cultures, in Yoghurt: Science and Technology. Eds. Tamine A.Y., Robinson R.K. Cambridge, Woodhead Publishing Ltd. 2007, 468-534. Deak T. Yeasts in specific types of foods, in Handbook of Food Spoilage Yeasts. Ed. Deak T. Boca Raton, CRC Press. 2007, 117-201. Hutkins R.W. Cultured dairy products, in Microbiology and Technology of Fermented Foods. Ed. Hutkins R.W. Oxford, Blackwell Publishing.2006, 107-44. International Commission on Microbiological Specifications for Foods. Milk and dairy products, in International Commission on Microbiological Specifications for Foods Microorganisms in Foods, Volume 6: Microbial Ecology of Food Commodities. International Commission on Microbiological Specifications for Foods. London, Plenum Publishers. 2005, 643-715.
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Walstra P., Wouters J.T.M., Geurts T.J. Dairy Science and Technology. Boca Raton, CRC Press. 2005. Frohlich-Wyder M.-T. Yeasts in dairy products, in Yeasts in Food: Beneficial and Detrimental Aspects. Eds. Boekhout T., Robert V. Cambridge, Woodhead Publishing Ltd. 2003, 209-37. Robinson R.K. Dairy Microbiology Handbook. New York, Wiley. 2002. Marth E.H., Steele J.L. Applied Dairy Microbiology. New York, Marcel Dekker. 2002. Fox P.F., Guinee T.P., Cogan T.M., McSweeney P.L.H. Pathogens and food-poisoning bacteria in cheese, in Fundamentals of Cheese Science. Eds. Fox P.F., Guinee T.P., Cogan T.M., McSweeney P.L.H. Gaithersburg, Aspen Publishers. 2000, 484-503. Fox P.F., Guinee T.P., Cogan T.M., McSweeney P.L.H. Microbiology of cheese ripening, in Fundamentals of Cheese Science. Eds. Fox P.F., Guinee T.P., Cogan T.M., McSweeney P.L.H. Gaithersburg, Aspen Publishers. 2000, 206-35. Fox P.F., Guinee T.P., Cogan T.M., McSweeney P.L.H. Bacteriology of cheese milk, in Fundamentals of Cheese Science. Eds. Fox P.F., Guinee T.P., Cogan T.M., McSweeney P.L.H. Gaithersburg, Aspen Publishers. 2000, 45-53. Teuber M. Fermented milk products, in The Microbiological Safety and Quality of Food, Volume 1. Eds. Lund B.M., Baird-Parker T.C., Gould G.W. Gaithersburg, Aspen Publishers. 2000, 535-89. Griffiths M.W. Milk and unfermented milk products, in The Microbiological Safety and Quality of Food, Volume 1. Eds. Lund B.M., Baird-Parker T.C., Gould G.W. Gaithersburg, Aspen Publishers. 2000, 507-34. Neaves P., Williams A.P. Microbiological surveillance and control in cheese manufacture, in Technology of Cheesemaking. Ed. Law B.A. Sheffield, Sheffield Academic Press. 1999, 251-80. Walstra P., Geurts T.J., Noomen A., Jellema A., van Boekel M.A.J.S. Microbiology of milk, in Dairy Technology: Principles of Milk Properties and Processes. Ed. Walstra P. New York, Marcel Dekker. 1999, 149-70. Rampling A. The microbiology of milk and milk products, in Topley and Wilson's Microbiology and Microbial Infections, Volume 2: Systematic Bacteriology. Eds. Balows A., Duerden B.I. London, Arnold Publishers. 1998, 367-93. International Dairy Federation, Jakobsen M., Narvhus J., Viljoen B.C. Yeasts in the Dairy Industry: Positive and Negative Aspects; Proceedings of a Symposium, Copenhagen, September 1996. IDF Special Issue No.9801. Brussels, International Dairy Federation. 1998. Early R. The Technology of Dairy Products. London, Blackie. 1998. Law B.A. Microbiology and Biochemistry of Cheese and Fermented Milk. London, Blackie. 1997. International Dairy Federation. The Significance of Pathogenic Microorganisms in Raw Milk. Brussels, International Dairy Federation. 1994. Varnam A.H., Sutherland J.P. Milk and Milk Products: Technology, Chemistry and Microbiology. London, Chapman and Hall. 1994. xii
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Fox P.F. Cheese: Chemistry, Physics and Microbiology, Volume 2: Major Cheese Groups. London, Chapman and Hall. 1993. Fox P.F. Cheese: Chemistry, Physics and Microbiology, Volume 1: General Aspects. London, Chapman and Hall. 1993. Vasavada P.C, Cousin M.A. Dairy microbiology and safety, in Dairy Science and Technology Handbook, Volume 2: Product Manufacturing. Ed. Hui Y.H. Weinheim, VCH Publishers. 1993, 301-426. White C.H., Bishop J.R., Morgan D.M. Microbiological methods for dairy products, in Standard Methods for the Examination of Dairy Products. Ed. Marshall R.T., American Public Health Association. Washington D.C, APHA. 1992, 287-308. Flowers R.S., Andrews W., Donnelly C.W., Koenig E. Pathogens in milk and milk products, in Standard Methods for the Examination of Dairy Products. Ed. Marshall R.T., American Public Health Association. Washington D.C., APHA. 1992, 103-212. Griffiths M.W., Stadhouders J., Driessen F.M. Bacillus cereus in liquid milk and other milk products, in Bacillus cereus in Milk and Milk Products. Ed. International Dairy Federation. Brussels, International Dairy Federation. 1992, 36-45. McPhillips J., Smith G.J., Feagan J.T., Snow N., Richards R.J. The microbiology of milk: a review of growth of bacteria in milk and methods of assessment, in Microbiology in Action. Ed. Murrell W.G. Letchworth, Research Studies Press Ltd. 1988, 275-91. Mabbitt L.A., Davies F.L., Law B.A., Marshal V.M. Microbiology of milk and milk products, in Essays in Agricultural and Food Microbiology. Ed. Norris J.R. Chichester, Wiley. 1987, 135-66.
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1. LIQUID MILK PRODUCTS
1.1
Definitions
Milk is a complex biological fluid secreted in the mammary glands of mammals. Its function is to meet the nutritional needs of neonates of the species from which the milk is derived. This section of the handbook refers mainly to bovine milk, but the milk of other species, such as sheep and goats, is used for human consumption. Typically, bovine milk is composed of approximately 87% water, 3.7 - 3.9% fat, 3.2 - 3.5% protein, 4.8 - 4.9% carbohydrate (principally lactose), and 0.7% ash. However, the exact composition of bovine milk varies with individual animals, with breed, and with the season, diet, and phase of lactation. Milk produced in the first few days post parturition is known as colostrum. Colostrum has a very high protein content, and is rich in immunoglobulin to help protect the newborn against infections. Colostrum is not generally allowed to enter the food supply in most countries. Fresh milk products here refers to liquid milk, which accounts for about half of the total dairy market in the UK. Liquid milk is largely heat treated in developed countries, but a small quantity of raw (unpasteurised) milk is still sold in the UK. Skimmed and semi-skimmed milk, which are defined by their fat content (0.5%, and 1.5 - 1.8%, respectively), are increasingly important products in the liquid milk market. 1.2
Initial Microflora
1.2.1
Contamination from the udder
Although milk produced from the mammary glands of healthy animals is initially sterile, microorganisms are able to enter the udder through the teat duct opening. Gram-positive cocci, streptococci, staphylococci and micrococci; lactic acid bacteria (LAB), Pseudomonas spp. and yeast are most frequently found in milk drawn aseptically from the udder; corynebacteria are also common. Where the mammary tissue becomes infected and inflamed; a condition known as mastitis, large numbers of microorganisms and somatic cells are usually shed into the milk. Mastitis is a very common disease in dairy cows, and may be present in a subclinical form, which can only be diagnosed by examining the milk for raised somatic cell counts. Many bacterial species are able to cause mastitis 1
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infection, but the most common are Staphylococcus aureus, Streptococcus agalactiae, Streptococcus uberis and Escherichia coli. These bacteria enter the udder by the teat duct, and Staph. aureus is able to colonise the duct itself. Although the organisms involved in mastitis are not usually able to grow in refrigerated milk, they are likely to survive, and their presence may be a cause of concern for health. Diseased cows may also shed other human pathogens in their milk, including Mycobacterium bovis, Brucella abortus, Coxiella burnetii, Listeria monocytogenes and salmonellae. Recently, concerns have also been raised over the presence of Mycobacterium avium var. paratuberculosis (MAP) (the causative organism of Johne's disease in cattle) in milk from infected animals. The outer surface of the udder is also a major source of microbial contamination in milk. The surface is likely to be contaminated with a variety of materials, including soil, bedding, faeces and residues of silage and other feeds. Many different microorganisms can be introduced by this means, notably salmonellae, Campylobacter spp., L. monocytogenes, psychrotrophic sporeformers, clostridia, and Enterobacteriaceae. Good animal husbandry and effective cleaning and disinfection of udders prior to milking are important in minimising contamination. 1.2.2
Other sources of contamination
Milking equipment and bulk storage tanks have been shown to make a significant contribution to the psychrotrophic microflora of raw milk if not adequately sanitised (1). Exposure to inadequately cleaned equipment and contaminated air are also sources of contamination (2). Milk residues on surfaces, and in joints and rubber seals can support the growth of psychrotrophic Gram-negative organisms such as Pseudomonas, Flavobacterium, Enterobacter, Cronobacter, Klebsiella, Acinetobacter, Aeromonas, Achromobacter and Alcaligenes, and Gram-positive organisms such as Corynebacterium, Microbacterium, Micrococcus and sporeforming Bacillus and Clostridium (3). These organisms are readily removed by effective cleaning and disinfection, but they may build up as biofilms in poorly cleaned equipment. Milk-stone, a mineral deposit, may also accumulate on inadequately cleaned surfaces, especially in hard water areas. Gram-positive cocci, some lactobacilli, and Bacillus spores can colonise this material and are then protected from cleaning and disinfection. Some of these organisms may survive pasteurisation and eventually cause spoilage (4). Other, less significant, sources of contamination include farm water supplies, farm workers and airborne microorganisms. 1.2.3
Natural antimicrobial factors
Raw milk contains a number of compounds that have some antimicrobial activity. Their purpose is to protect the udder from infection and also to protect neonates,
2
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but they may also have a role in the preservation of raw milk during storage and transport. Lactoperoxidase is an enzyme found in milk. It has no inherent antimicrobial activity, but, in the presence of hydrogen peroxide (usually of microbial origin), it oxidises thiocyanate to produce inhibitors such as hypothiocyanite. This is referred to as the lactoperoxidase system, and it has bactericidal activity against many Gram-negative spoilage organisms, and some bacteriostatic action against many pathogens. For this reason it has been investigated as a possible means of extending the life of stored milk (5) Lactoferrin is also found in milk and is a glycoprotein that binds iron so that it is not available to bacteria. The chelation of iron in the milk inhibits the growth of many bacteria. In addition to producing an iron-deficient environment, lactoferrin is thought to cause the release of anionic polysaccharide from the outer membrane of Gram-negative bacteria, thereby destabilising the membrane. Lysozyme acts on components of the bacterial cell wall, causing cell lysis. Gram-positive organisms are much more susceptible to lysozyme than Gramnegatives, although bacterial spores are generally resistant. Immunoglobulins of maternal origin are often present in milk, and colostrum is a particularly rich source. These proteins may inactivate pathogens in milk, but their significance in preservation is uncertain. 1.3
Processing and its Effects on the Microflora
1.3.1
Raw milk transport and storage
In developed countries, raw milk on the farm is usually cooled quickly and stored in refrigerated bulk tanks at 140 °C for 2 seconds or the equivalent) and are aseptically packaged.
3.2
Initial Microflora
The initial microflora are essentially those of the raw milk (influenced by microflora on the cow’s udder, milk-handling equipment, and storage conditions) from which the cream is made. 3.3
Processing and its Effect on the Microflora
The production of cream is outlined in Figure 3.1 on the following page. 3.3.1
Storage and transport of raw milk
Generally, the same comments apply to raw milk for cream production as for fresh milk products, and the milk should be of equivalent microbiological quality. It is important to ensure the milk is produced hygienically, as the heat that cream is subjected to kills vegetative cells but not spores. However, the high fat content of cream means that it is more susceptible to spoilage by extracellular lipases produced by psychrotrophic Pseudomonas spp. and other organisms in raw milk. These enzymes can survive heat treatment, and therefore it is preferable to minimise the refrigerated storage time of raw milk for fresh cream production, and process as soon as possible after collection.
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Fig. 3.1. Alternation sequence of operations to produce cream. Reproduced with permission fromWilbey R.A. Microbiology of Cream and Butter, in Dairy Microbiology Handbook: The Microbiology of Milk and Milk Products. Ed. Robinson R. New York, John Wiley & Sons, Inc. 2002, 123-74.
3.3.2
Separation
Separation is the concentration of the fat globules and their removal from the milk. Traditionally, this used to be done by skimming, but centrifugal separators are now used in commercial dairies. Centrifugal separators of the disc stack type are commonly used in modern operations. These consist of a series of conical steel discs within the bowl of the separator, rotated by a spindle. Milk is fed into the rotating bowl and passes into the disc stack through holes. The milk is accelerated and the less dense fat globules move inwards on the disc surface as the heavier serum phase moves outwards. Both phases are then collected in separate chambers. Solid particles of debris and somatic cells in the milk collect on the outer wall of the separator bowl and form a layer of slime. This slime may also contain some bacteria from the 39
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milk, particularly clumps or chains of cells. Although it is suggested that separation sometimes concentrates bacteria in the fat phase, however, there seems to be little evidence of a difference in the populations of the two phases (1). To minimise damage to fat globules, separation is ideally carried out at a temperature of 40 - 50 °C a temperature at which rapid microbial growth is possible. Therefore, higher temperatures (55 – 63 °C) are often recommended; viscous creams are generally produced using these high temperatures. Some separators used to produce high-fat creams (40% fat content) are able to operate at 5 °C, at which temperature significant growth will not occur. Standardisation of the cream for fat content is usually necessary after separation, since it is difficult to control the process sufficiently to achieve exactly the required level. Separators are therefore set to give a slightly higher than required fat content, and whole or skimmed milk is then added to give the correct value. Standardisation is often carried out at about 40 °C and there is therefore a risk of rapid microbial growth if the process is not carried out quickly. In larger modern dairies this problem can be overcome by partially automating the separation process, either by precise control of flow rates or by feedback control using accurate on-line determination of the fat content in the cream produced. 3.3.3
Homogenisation
The need to homogenise cream depends on the particular characteristics of the cream type produced. Half and single creams are usually homogenised to prevent fat separation and provide adequate viscosity. Double and whipping creams are not usually homogenised unless they are UHT-processed. Homogenisation may be carried out before or after heat treatment, but, from a microbiological point of view, homogenisation before heat treatment is preferred. Homogenisation after heat treatment helps to reduce problems with rancidity caused by lipases present in the milk, and some producers therefore choose this approach. UHT-treated cream is normally homogenised after heat treatment. 3.3.4
Heat treatment
Almost all cream sold in developed countries must be heat treated in some way to ensure a safe product. Minimum pasteurisation treatments are set out in the legislation of many countries and, in the UK, are the same as those applied to pasteurised milk (72 °C for 15 seconds, or 63 - 65 °C for 30 minutes). High-temperature, short time (HTST) processes are almost universally used in modern dairies, but higher temperatures than those used in HTST processing are often applied, both to achieve a longer shelf life, and to overcome the protective effect of the high fat content. For example, the International Dairy Federation (lDF) has recommended a process of 75 °C for 15 seconds for cream with a fat content of 18%, and 80 °C for 15 seconds for cream containing 35% or more fat. In the United States, dairy
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products containing more than 10% fat should receive a minimum heat treatment of 74.4 °C for 15 seconds. Cream may also be sterilised in containers either by batch or continuous rotary retorting at 110 - 120 °C for 10 - 20 minutes. For homogenised fat cream, heat treatments of 121 °C for 15 minuntes or 122 °C for 10 minutes are given. Containers must receive a heat treatment of not less than 108 °C for 45 minutes. Cans are sterilised at 116 - 121 °C for 30 minutes, but if the cream receives UHT treatment lower time-temperatures can be used (2). This process is only suitable for cream with a low fat content, since high-fat creams conduct heat poorly. UHT sterilisation processes are also applied, followed by aseptic filling into cartons in a process similar to that used for milk. A minimum process of 140 °C for 2 seconds is stipulated in the UK to render the cream free of both viable cells and spores, although some very heat-resistant bacterial spores may still survive this process. UHT processing is most suitable for single and half cream. The control of the process becomes increasingly difficult as the fat content rises. Another method for sterilisation is the Autothermal Thermophilic Aerobic Digester (ATAD) friction process where the milk is initially preheated to 70 °C and subsequently heated to 140 °C for 0.54 seconds. This process can be used for creams containing 12 and 33% fat (2). 3.3.5
Cooling and packaging
Pasteurised cream should be cooled as soon as possible after heat treatment to a temperature of 5 °C or less, to prevent growth of thermoduric organisms, and then be packaged quickly. Most cream for retail sale is now packed in plastic pots sealed with metal foil lids. This type of packaging generally carries very low levels of microbial contamination. However, as with pasteurised milk, the hygienic operation of the filling process is essential to prevent post-pasteurisation contamination. Bulk cream for catering is often packed in 'bag in box' containers, and bulk cream for manufacturing is usually transported in stainless steel tanks, which must be cleaned and sanitised effectively between uses. 3.4
Processing of Other Creams
3.4.1
Whipped cream
Whipped cream contains added sugar and stabilisers. The stabilised cream is then pasteurised and held at 5 °C for 24 hours. Compressed air or nitrogen is then introduced into the mix. This provides an excellent aerobic medium for microbial growth, thereby increasing the chances of spoilage in comparison with liquid cream (2).
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3.4.2
Frozen cream
Frozen cream is pasteurised at ≥ 75 °C for 15 seconds. It is then quickly cooled to 1 °C before being frozen in containers, as sheets or pellets, or by direct contact with liquid nitrogen. It is then stored at -18 to -26 °C (2). 3.4.3
Clotted creams
Clotted creams are traditionally made by putting milk in a pan 30 cm in diameter and 20 cm deep where it is held for 12 hours to allow the cream to rise. The pan is then put on a steamer until a layer of solidified cream is formed around the edge. Modern methods involve (a) heating double cream over a layer of skimmed or whole milk, in a large, shallow jacketed tray until a crust is formed or (b) heating a thin layer of high-fat cream (54 – 59 % milk fat) at 77 – 85 °C, to form a crust. The more severe heat treatments result in aerobic spore-formers being the predominant microflora. However, slow cooling and poor hygiene are more likely to lead to the growth of spoilage moulds, coliforms and other contaminants (2). 3.4.4
Cream-based desserts
Cream-based desserts typically undergo heat treatments above pasteurisation, in order to allow cooking of other ingredients such as starch. 3.5
Spoilage
The spoilage of cream is generally similar to that described for liquid milk products. However, because of the difference in purchasing patterns, cream is often required to have a longer shelf life than milk (up to 14 days for pasteurised cream), and containers may be opened and then used by the consumer over several days. The keys to obtaining sufficient shelf life are the microbiological quality of the raw milk, good hygiene in processing, and effective temperature control during distribution and storage. Cream usually receives more severe heat processes than milk, and the post-heat treatment microbial population therefore consists almost entirely of relatively heat-resistant species. Aerobic spore-forming bacteria survive pasteurisation, and psychrotrophic strains of Bacillus cereus may cause 'sweet curdling' and ‘bitty cream’. Other, more heat-resistant species, such as Bacillus licheniformis, Bacillus coagulans, and Bacillus subtilis, may survive sterilisation and even UHT processes, and may cause bitterness and thinning in sterilised creams (2). Bacillus pumilus and Bacillus sporothermophilus are now recognised as potential contaminants in cream, primarily carried over from raw milk. Under UHT conditions, B. sporothermophilus has D-values of 3.4 - 7.9 sec and z-values of 13.1 - 14.2 (2). Heat-resistant lipases produced by psychrotrophic bacteria
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growing in the raw milk may also survive high-temperature processing and cause spoilage in UHT cream. The keeping quality of cream is greatly affected by the introduction of postprocess contamination. Psychrotrophic bacteria such as pseudomonads may contaminate pasteurised cream during processing and are important spoilage organisms. The high fat content of cream means that lipolytic species, such as Pseudomonas fluorescens and Pseudomonas fragi, are a particular problem. A study of pasteurised double cream showed that pseudomonads were the predominant spoilage organisms (3). Psychrotrophic members of the Enterobacteriaceae are also sometimes involved. Yeasts and moulds are rarely implicated in the spoilage of cream. Few yeasts are able to ferment lactose, but species such as Candida lipolyticum and Geotrichum candidum may occasionally spoil bakers' whipping cream where sucrose has been added (4). If, however, other organisms hydrolyse lactose, then the yeast can grow rapidly to produce yeasty or fruity flavours and gas; Torula cremoris, Candida pseudotropicalis and Torulopsis sphaerica have been implicated with such defects (2). Where cream is stored at very low temperatures (0 - 1 °C) to prolong the shelf life, mould growth, usually Penicillium spp. may develop on the cream surface (4). Defective cans or leaking seams could cause spoilage of cream due to entry of bacteria from cooling water or other sources, e.g. a waterborne organism, for example Proteus, can cause bitterness and thinning, coliforms can produce gas, and lactococci could result in acid curdling (2). In the case of cream-based desserts, thermoduric organisms are most likely to be an issue due the more aggressive heat treatments that are used. In addition, the added sugar increases the range of contaminants that could grow in the product. Fruit conserves, if added, will lower the pH of the product thus favouring the growth of yeasts and moulds. With multi-component desserts, both individual components, and blends obtained from their mixing could be responsible for microbial spoilage (2). 3.6
Pathogens: Growth and Survival
In practice, to overcome the protective effect of the higher fat content, cream usually receives a more severe heat treatment than milk. This means that pathogens present in the raw cream are more likely to be destroyed. Unpasteurised cream carries a high risk from the presence of foodborne pathogens, as does raw milk, but the recent safety record of pasteurised cream is good. Although foodpoisoning outbreaks have been associated with cream, they are often linked to products filled with, or prepared with cream. In these cases, it is probable that poor hygiene during manufacture, and temperature abuse during storage have been important contributory factors.
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3.6.1
Salmonella spp.
Salmonellae will not survive the heat treatment applied to cream, and therefore their presence is likely to be due to post-pasteurisation contamination. The cells are likely to survive for extended periods in contaminated cream, but growth is not possible unless significant temperature abuse occurs. Storage at temperatures below 5 °C will prevent multiplication. Most of the relatively recent outbreaks recorded have been associated with foods prepared with cream. For example, in 1986 an outbreak of Salmonella typhimurium DT40 infection affecting 24 people in the UK was linked to consumption of cream-filled profiteroles (5). A much larger outbreak occurred in Navarra in Spain in 1991, and was reported to have affected approximately 1,000 people. The causative organism was Salmonella enteritidis, and the outbreak was associated with the consumption of contaminated confectionery custard and whipped cream (6). In 1992, an outbreak of S. enteritidis PT4 infection in Wales was associated with fresh cream cakes, and was found to be a result of contamination of the factory environment by the organism, and inadequate cleaning of the nozzles used to pipe cream into the cakes (7). More recently, in 1998, an outbreak of S. typhimurium DT104 infection affected 86 people in Lancashire. The outbreak was linked to inadequately pasteurised milk from a local dairy, but cream from the same dairy was also recalled (8). 3.6.2
Listeria monocytogenes
There has been some concern that L. monocytogenes might be able to survive cream pasteurisation processes and then grow during chilled storage. However, L. monocytogenes strain Scott A recorded a D-value of 6 seconds at 68.9 °C in raw cream with a fat content of 38%, indicating that pasteurisation is likely to be effective. The D-value increases to 7.8 sec in inoculated ‘sterile’ cream. Z-values were calculated as 6.8 °C and 7.1 °C, respectively (9). A later study, using two strains of L. monocytogenes suspended in different dairy products, including half and double cream, showed that, although heat resistance did vary, minimum pasteurisation processes would be adequate to eliminate the organism in all products. An investigation into the fate of several strains of L. monocytogenes in whipping cream at various storage temperatures recorded generation times of 29 - 46 hours at 4 °C. Populations of approximately 107 cells/ml were reached after incubation for 30 days, and, at 8 °C, hazardous levels were reached in only 8 days (10). This indicates that post-pasteurisation contamination of cream could be a potentially serious problem. The same post-process hygiene precautions should be applied for cream as for other high-risk chilled products. Despite this, although L. monocytogenes infection is reported to have been linked to cream on epidemiological evidence (4), such cases have not been confirmed by microbiological investigation.
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3.6.3
Yersinia spp.
Yersinia enterocolitica is a common contaminant of raw milk, although the majority of the strains isolated are not pathogenic to humans. The organism is heat-sensitive and does not survive pasteurisation, but is capable of psychrotrophic growth. Therefore, it is a potential hazard in cream if introduced as a post-pasteurisation contaminant. A survey of dairy products in Australia recorded an isolation of Y. enterocolitica from pasteurised cream (11), but the organism was not detected in cream sampled in the UK over the course of a 3-year survey to determine its incidence in foods (12). There have been no reported outbreaks of Y. enterocolitica infection associated with cream. 3.6.4
Staphylococcus aureus
Although Staph. aureus can often be isolated from raw milk, and is a common cause of mastitis in cows, it does not survive pasteurisation, and cases of staphylococcal food poisoning from pasteurised dairy products are now uncommon. It may be introduced into cream as a post-process contaminant, particularly from infected food handlers. However, it is incapable of growth below about 7 °C, and high numbers will only develop following significant temperature abuse. An investigation of growth and enterotoxin A production by Staph. aureus in whey cream showed that growth was limited and that enterotoxin was not produced at detectable levels (13). Despite this, between 1951 and 1970, six outbreaks of staphylococcal poisoning associated with cream were recorded in England and Wales (14). There have been few recent reports of outbreaks, following significant improvements in hygiene and temperature control. As with Salmonella, products prepared or filled with cream are now more likely to be implicated as vehicles of staphylococcal poisoning than cream itself, usually as a result of poor hygiene during handling and temperature abuse. 3.6.5
Bacillus cereus
B. cereus is common in milk, and its endospores are able to survive pasteurisation. Some strains are also psychrotrophic, and capable of growth in refrigerated dairy products. Nevertheless, there are very few reports of B. cereus food poisoning associated with dairy products. There have been a small number of outbreaks associated with the consumption of pasteurised cream. In 1975 cream found to contain 5xl06 cfu B. cereus caused illness in several people (15). In 1989, two members of the same family became ill after consuming fresh single cream that was later found to contain B. cereus at levels of 3x107/g (16).
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3.6.6
Verotoxigenic Escherichia coli (VTEC)
VTEC, particularly Escherichia coli O157, have been found in raw milk and have caused serious outbreaks of infection associated with consumption of raw or inadequately pasteurised dairy products. An outbreak of E. coli O157 infection was recorded in the UK in 1998, associated with consumption of raw cream from a small farm dairy. Seven cases were recorded, with four requiring admission to hospital (17). These organisms are destroyed by properly applied pasteurisation, but if any opportunities for cross-contamination between raw and pasteurised cream exist, recontamination could potentially occur. It is likely that E. coli O157 could survive for prolonged periods in cream, but growth in the absence of temperature abuse is improbable. In view of the potentially serious nature of infections caused by VTEC, and the low infective dose, it is important to ensure that such cross-contamination does not occur, since growth may not be required to cause infection. 3.6.7
Viruses
Viral hepatitis is the most likely viral infection to be associated with dairy products. In 1975 in Scotland, an outbreak of hepatitis A infection occurred associated with cream consumption. The cause of the outbreak was handling of the cream by an infected cook during preparation (18). 3.7
References
1. Griffiths M.W. Milk and unfermented milk products, in The Microbiological Safety and Quality of Food, Volume 1. Eds. Lund B.M., Baird-Parker T.C, Gould G.W. Gaithersburg, Aspen Publishers. 2000, 507-34. 2 Wilbey R.A. Microbiology of Cream and Butter, in Dairy Microbiology Handbook: The Microbiology of Milk and Milk Products. Ed. Robinson R. New York, John Wiley & Sons, Inc. 2002, 123-74. 3. Phillips J.D., Griffiths M.W., Muir D.D. Growth and associated enzyme activity of spoilage bacteria in pasteurised double cream. Journal of the Society of Dairy Technology, 1981, 34 (3), 113-8. 4. Varnam A.H., Sutherland J.P. Cream and cream-based products, in Milk and Milk Products: Technology, Chemistry and Microbiology. Eds. Varnam A.H., Sutherland J.P. London, Chapman and Hall. 1994, 183-223. 5. CDR. Communicable disease associated with milk and dairy products England and Wales 1985-86. CDR Weekly, 1987, 49, 3-4.
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CREAM 6. Sesma B., Moreno M., Eguaras J. Foodborne Salmonella enteritidis outbreak: A problem of hygiene or technology? An investigation by means of HACCP monitoring, in Foodborne Infections and Intoxications; Proceedings of the 3rd World Congress, Berlin, June 1992, Vo1.2. Eds. Food and Agriculture Organisation, World Health Organisation. Berlin, Institute of Veterinary Medicine. 1992, 1065-8. 7. Evans M.R., Tromans J.P., Dexter E.L.S., Ribeiro C.D., Gardner D. Consecutive Salmonella outbreaks traced to the same bakery. Epidemiology and Infection, 1996, 116 (2), 161-7. 8. Anon. Defective pasteurisation linked to outbreak of Salmonella typhimurium definitive phage type 104 infection in Lancashire. CDR Weekly, 1998, 8 (38), 335, 338. 9. Bradshaw J.G., Peeler J.T., Corwin J.J., Hunt J.M., Twedt R.M. Thermal resistance of Listeria monocytogenes in dairy products. Journal of Food Protection, 1987, 50 (7), 543-4, 556. 10. Rosenow E.M., Marth E.H. Growth of Listeria monocytogenes in skim, whole and chocolate milk, and in whipping cream during incubation at 4, 8, 13, 21 and 35 °C. Journal of Food Protection, 1987, 50 (6), 452-9, 63. 11. Hughes D. Isolation of Yersinia enterocolitica from milk at a dairy farm in Australia. Journal of Applied Bacteriology, 1979, 46 (1), 125-30. 12. Greenwood M.H., Hooper W.L. Yersinia spp. in foods and related environments. Food Microbiology, 1985, 2 (4), 263-9. 13. Halpin-Dohnalek M.I., Marth E.H. Growth and production of enterotoxin A by Staphylococcus aureus in cream. Journal of Dairy Science, 1989, 72 (9), 2266-75. 14. Ryser E.T. Public health concerns, in Applied Dairy Microbiology. Eds. Marth E.H., Steele J.L. New York, Marcel Dekker. 2001, 397-546. 15. Christiansson A. The toxicology of Bacillus cereus, in Bacillus cereus in Milk and Milk Products. Ed. International Dairy Federation. Brussels, IDF. 1992, 30-5. 16. Sockett P.N. Communicable disease associated with milk and dairy products: England and Wales 1987-89. CDR Weekly, 1991, 1 (Review 1), R9-R12. 17. Anon. Cases of Escherichia coli O157 infection associated with unpasteurised cream. CDR Weekly, 1998, 8 (43), 377. 18. Chaudhuri A.K.R., Cassie G., Silver M. Outbreak of foodborne type-A hepatitis in greater Glasgow. Lancet, 1975, 2 (7927), 223-5.
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4. BUTTER AND DAIRY SPREADS
4.1
Definitions
Butter is a water-in-oil emulsion typically consisting of at least 80% fat, 15 - 17% water, and 0.5 - 1% carbohydrate and protein. The two principal types of butter produced are sweet cream butter and ripened cream butter. The UK, Ireland, US, Australia and New Zealand prefer sweet cream butter (pH 6.4 - 6.5), which often contains 1.5 - 2.0% salt. In Europe, cultured (ripened cream), unsalted butter is favoured, in which lactic starter cultures are added to convert the lactose to lactic acid and produce flavour compounds, such as acetoin and diacetyl, from citrate. In many countries, salt and lactic cultures are the only permitted non-dairy additions to butter, although, in the UK and other countries, natural colouring agents, such as annatto, β-carotene and turmeric may be added. Reduced-fat dairy spreads have a milk fat content of about 50 - 60%. Low-fat dairy spreads contain 39 – 41% fat, and very low-fat spreads have 20% are water-in-oil emulsions. Crystallisation and working are essential to achieve the correct physical properties and texture for the end- product. As with butter, crystallisation is promoted by rapid cooling, which also inhibits the growth of any microorganisms that may have survived pasteurisation. Reduced- and low-fat spreads have much higher water contents than butter, and it is therefore not possible to achieve a small droplet size for the aqueous phase by working. Droplets can be much larger than 10 µm in diameter, and, in low-fat products, continuous water channels are likely. This also has the effect of diluting inhibitors, such as salt or acid, and the compartmentalisation effect described for butter is much reduced. These products are therefore much less resistant to microbial growth and spoilage, and effective hygiene procedures during manufacturing become critical. 4.3.3.4 Packaging These products may need to be packed in a filtered or sterile air environment to prevent airborne contamination. Very low fat products may also require that the packaging be decontaminated, and the resulting packing process becomes similar to an aseptic filling operation. Such products are usually packed in tubs with a heat-sealed foil laminate lid.
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4.4
Spoilage
4.4.1
Butter
4.4.1.1 Bacterial spoilage Modern hygienic manufacturing methods mean that bacterial spoilage of butter is much less common than in the past. However, defects caused by microorganisms do occasionally occur. Surface taints may develop as a result of growth of Shewanella putrefaciens (formerly Alteromonas putrefaciens), and Pseudomonas putrefaciens or Flavobacterium spp. Such spoilage may be apparent within 7 to 10 days of chilled storage. The surface layers are initially affected, but eventually spoilage is apparent throughout the product. A putrid or cheesy flavour develops due to the breakdown of protein (5). Rancidity, proteolytic activity and fruity odours may be caused by the growth of Pseudomonas fragi and, occasionally, Pseudomonas fluorescens (1). Black discoloration of butter is reported to be caused by Pseudomonas nigrificans (1), Pseudomonas mephitica is responsible for a skunk-like odour, and an organism formerly known as Lactococcus lactis var. maltigenes may be responsible for a 'malty' flavour defect linked to the formation of 3-methylbutanal (1, 6). Lipolytic spoilage of butter has been associated with the presence of Micrococcus (7). 4.4.1.2 Fungal spoilage Moulds are still important spoilage organisms for butter, and mould growth may produce surface discolorations and taints. A number of genera have been associated with spoiled butter, including Penicillium, Aspergillus, Cladosporium, Mucor, Geotrichum, Alternaria, and Rhizopus. Yeasts may also cause spoilage of butter. Lipolytic species such as Rhodotorula may grow on the surface at chill temperatures and may tolerate high salt concentrations. Other yeasts associated with spoilage include Candida lipolytica, Torulopsis, and Cryptococcus (7, 8). 4.4.2
Dairy spreads
There is little information on spoilage of spreads. In theory, the aqueous phase of some low-fat spreads would allow the growth of spoilage bacteria, such as pseudomonads, but in practice the majority of problems are the result of mould growth. Generally, the same genera are involved as for butter spoilage. Preservatives such as sorbic acid help to prevent mould growth, but some species, including Penicillium spp. and Trichoderma harzianum, are able to convert preservatives to other compounds, which may result in tainting. In low-fat spreads, very low levels of mould contamination may be sufficient to cause spoilage before the end of shelf life (5, 9). The yeast Yarrowia lipolytica and
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bacteria Bacillus polymyxa and E. faecium have also been reported to be important spoilage organisms in a low-fat dairy spread (1, 8). 4.5
Pathogens: Growth and Survival
4.5.1
Butter
Commercially produced butter is made from pasteurised cream, and that fact, plus its physicochemical characteristics, make it quite inhibitory to bacterial pathogens. It is therefore not surprising that there have been few recorded outbreaks of foodborne disease associated with commercial butter. 4.5.1.1 Staphylococcus aureus Outbreaks of staphylococcal food poisoning have been associated with butter. In one case, an outbreak involving 24 customers, recorded in the USA in 1970, was linked to whipped butter and to the butter from which the whipped butter was made. The presence of staphylococcal enterotoxin A was demonstrated in both butters. It appeared that the enterotoxin had formed in the cream used to make the butter and was carried over into the finished product (10). A second outbreak, affecting more than 100 customers of pancake houses, was also traced to commercially prepared whipped butter in 1977, and again toxin formation in the cream was suspected (11). Investigations into the survival of Staph. aureus in butter and whipped butter containing 1.5% salt showed that numbers decreased only slowly, especially in whipped butter. Reduction of the salt content to 0 - 1% allowed the population to increase by a factor of ten in 14 days at 23 °C. Therefore a combination of poor hygiene, low salt concentration (or inadequate salt dispersal), and temperature abuse could allow growth of Staph. aureus in stored butter (12). 4.5.1.2 Listeria monocytogenes L. monocytogenes has been shown to grow slowly in butter made from contaminated cream at 4 or 13 °C, and to survive for several months in frozen butter without any appreciable decrease in numbers (13). Listeria will not survive cream pasteurisation, but it is a very common environmental contaminant in dairy settings, and effective cleaning and hygiene procedures are necessary to prevent recontamination. Surveys of the incidence of Listeria in dairy products have not isolated it from butter (14, 15). However, despite this, an outbreak of listeriosis associated with butter was reported in a hospital in Finland in 1999. A total of 25 people were affected and six died. A strain of L. monocytogenes (serotype 3a) was isolated from packs of butter at the hospital, and from butter and environmental samples at a local dairy plant (16). Butter was also identified as the possible food vehicle in an outbreak 56
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of listeriosis, in the US in 1987; 11 pregnancy-associated cases occurred (17). More recently in 2003, 234 cases of listeriosis were reported from 4 clusters in the Humberside and Yorkshire areas of the UK. Environmental samples implicated butter as the cause of the incidence in one cluster (18). 4.5.1.3 Campylobacter In 1995, an outbreak of Campylobacter jejuni enteritis in the USA, which affected 30 people who had eaten in a local restaurant, was associated with garlic butter prepared on site. The survival of Campylobacter in butter, with and without garlic, was later investigated, and it was found that C. jejuni could survive in butter without garlic for 13 days at 5 °C (19). 4.5.1.4 Toxins The stability of aflatoxin M1 through butter production and storage has been investigated. Most of the toxin naturally present in the cream was removed with the buttermilk, with very little remaining in the butter. Chilled and frozen storage of the butter had little effect on the toxin (20). 4.5.2
Dairy spreads
There are very few reports of foodborne disease outbreaks associated with dairy spreads, and none associated with reduced- and low-fat products, although it has been suggested that some pathogens may be able to grow in some of these products. Inoculation experiments using two 'light butters' showed that L. monocytogenes and Yersinia enterocolitica were both capable of growth during refrigerated storage. Both pathogens were capable of more rapid growth than the indigenous microflora (21). An outbreak of food poisoning caused by Staphylococcus intermedius was reported in the USA in 1991. The outbreak affected over 265 people and was associated with consumption of contaminated butter-blend spread (22). It is likely that pasteurisation and the rigorous hygiene controls applied to the manufacture of these products, especially the low-fat varieties, is effective in preventing the entry of pathogens during processing. 4.6
References
1. Kornacki J., Flowers R., Bradley R. Jr. Microbiology of Butter and Related Products, in Applied Dairy Microbiology. Eds. Marth E., Steele J. New York, Marcel Dekker, Inc. 2001, 127–50. 2. The Bacteriology of Butter, in Dairy Bacteriology. Eds. Hammer B.W., Babel F.J. New York, Wiley & Sons. 1957.
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DAIRY PRODUCTS 3. International Dairy Federation. Continuous butter manufacture, in International Dairy Federation Bulletin 204. Ed International Dairy Federation. Brussels, International Dairy Federation. 1986, 1-36. 4. Lelieveld H.l.M., Mostert M.A. Hygienic aspects of the design of food plants, in Food Production, Preservation and Safety. Ed. Patel P. Chichester, UK, Ellis Horwood Ltd. 1992. 5. Oil- and fat-based foods, in International Commission on Microbiological Specifications for Foods Microorganisms in Foods, Volume 6: Microbial Ecology of Food Commodities. Ed. International Commission on Microbiological Specifications for Foods. London, Plenum Publishers. 2005, 480 - 521. 6. Jackson H.W., Morgan M.E. Identity and origin of the malty aroma substance from milk cultures of Streptococcus lactis var. maltigenes. Journal of Dairy Science, 1954, 37, 1316-24. 7. Boor K., Fromm H. Managing microbial spoilage in the dairy industry, in Food Spoilage Microorganisms. Ed. Blackburn C. de W. Cambridge, Woodhead Publishing Ltd. 2006, 171-93. 8. Varnam A.H., Sutherland J.P. Butter, margarine and spreads, in Milk and Milk Products: Technology, Chemistry and Microbiology. Eds. Varnam A.H., Sutherland J.P. London, Chapman and Hall. 1994, 224-74. 9. Van Zijl M.M., Klapwijk P.M. Yellow fat products (butter, margarine, dairy and nondairy spreads), in The Microbiological Safety and Quality of Food, Volume 1. Eds. Lund B.M., Baird-Parker T.C., Gould G.W. Gaithersburg, Aspen Publishers. 2000, 784-806. 10. Anon. Staphylococcal food poisoning traced to butter: Alabama. Morbidity Mortality. Weekly Report, 1970, 28, 129-30. 11. Anon. Presumed staphylococcal food poisoning associated with whipped butter. Morbididity and Mortality Weekly Report. 1977, 26 (32), 268. 12. Minor T.E., Marth E.H. Staphylococcus aureus and enterotoxin A in cream and butter. Journal of Dairy Science, 1972, 55 (10), 1410-4. 13. Olsen J.A., Yousef A.E., Marth E.H. Growth and survival of Listeria monocytogenes during making and storage of butter. Milchwissenschaft, 1988, 43 (8), 487-9. 14. Harvey J., Gilmour A. Occurrence of Listeria species in raw milk and dairy products produced in Northern Ireland. Journal of Applied Microbiology, 1992, 72 (2), 11925. 15. Massa S., Cesaroni D., Poda G., Trovatelli L.D. The incidence of Listeria spp. in soft cheeses, butter and raw milk in the province of Bologna. Journal of Applied Bacteriology, 1990, 68 (2), 153-6. 16. Lyytikainen O., Autio T., Maijala R., Ruutu P., Honkanen-Buzalski T., Miettinen M., Hatakka M., Mikkola J., Anttila V.-J., Johansson T., Rantala L., Aalto T., Korkeala H., Siitonen A. An outbreak of Listeria monocytogenes serotype 3a infections from butter in Finland. Journal of Infectious Diseases, 2000, 181, 1838-41.
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BUTTER AND DAIRY SPREADS 17. Mascola L., Chun L., Thomas J., Bibe W.F., Schwartz B., Salminen C., Heseltine P. A case-control study of a cluster of perinatal listeriosis identified by an active surveillance system in Los Angeles County. Proceedings of Society for Industrial Microbiology-Comprehensive Conference on Listeria monocytogenes, Rohnert Park, CA, 1998. 18. CDR. Listeria monocytogenes infections in England and Wales in 2004. Communicable Disease Report Weekly, 2004, 14 (37). 19. Zhao T., Doyle M.P., Berg D.E. Fate of Campylobacter jejuni in butter. Journal of Food Protection, 2000, 63 (1), 120-2. 20. Wiseman D.W., Marth E.H. Stability of aflatoxin M 1 during manufacture and storage of a butter-like spread, non-fat dried milk and dried buttermilk. Journal of Food Protection, 1983, 46 (7), 633-6. 21. Lanciotti R., Massa S., Guerzoni M.E., Fabio G.D. Light butter: natural microbial population and potential growth of Listeria monocytogenes and Yersinia enterocolitica. Letters in Applied Microbiology, 1992, 15 (6), 256-8. 22. Khambaty F.M., Bennett R.W., Shah D.B. Application of pulsed-field gel electrophoresis to the epidemiological characterisation of Staphylococcus intermedius implicated in a food-related outbreak. Epidemiology and Infection, 1994, 113 (1), 75-81.
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CHEESE
5. CHEESE
5.1
Definitions
Cheese is a stabilised curd of milk solids produced by casein coagulation and entrapment of milk fat in the coagulum. The water content is greatly reduced, in comparison with milk, by the separation and removal of whey from the curd. With the exception of some fresh cheeses, the curd is textured, salted, shaped, and pressed into moulds before storage and curing or ripening. There are said to be approximately 1,000 named cheeses throughout the world, each produced using a variation on the basic manufacturing process. Most of these varieties fit into one of three main categories according to their moisture content, and method and degree of ripening: 5.1.1
Soft cheese High moisture (55 - 80%) a) fresh, unripened (cottage cheese, Ricotta, Quarg, Fromage Blanc, Neufchâtel, Mozzarella) b) surface mould-ripened (Brie, Camembert)
5.1.2
Semi -soft / semi-hard cheese Moderate moisture (41 - 55%) a) surface smear ripened (Limburger, Munster, Tilsit) b) ripened by bacteria (Caerphilly, Lancashire, St Paulin) c) Blue-veined, internally mould ripened (Stilton, Roquefort, Gorgonzola)
5.1.3
Hard / Iow moisture cheese Low moisture (20 - 40%) a) ripened by bacteria, with eyes (Emmental, Gruyère) b) ripened by bacteria, no eyes (Cheddar, Edam, Cheshire) c) very hard (Grana (Parmesan), Asiago, Romano)
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5.2
Initial Microflora
Essentially the initial microflora correspond with those of the milk used to produce the cheese. 5.3
Processing and its Effects on Microflora
A diagram of the basic steps in the production of cheese is given in Figure 5.1, using Cheddar as an example.
Fig. 5.1. Production of cheese (e.g. Cheddar)
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5.3.1
Pasteurisation
Cheese may be made from raw milk, pasteurised milk, or milk that has undergone a sub-pasteurisation (thermisation) treatment. Pasteurisation destroys the vegetative cells of pathogens as well as many spoilage organisms, and some of the enzymes naturally present in the milk. It is argued that pasteurisation affects the ripening and flavour development of cheese, and that only raw milk cheeses develop a full and mature flavour. However, a recent study suggested that, if high quality milk was used, pasteurisation produced differences in texture, but flavour and aroma were little affected (1). A sub-pasteurisation (thermisation) process (typically 65 - 70 °C for 15 - 20 seconds), may be used to destroy many vegetative cells, but without inactivating some of the enzymes involved in flavour development. Milk for cheese may also be subjected to the bactofugation process (see Chapter 1 Liquid Milk Products), which may be used to substantially reduce the number of bacterial spores in the milk, and help to prevent later spoilage. The principal disadvantage of raw milk is the possible presence of pathogens, such as Staphylococcus, Listeria, Salmonella and verocytotoxigenic Escherichia coli (VTEC), all of which have caused outbreaks of infection associated with unpasteurised cheeses. Ideally, from a safety point of view, only pasteurised milk would be used to produce cheese. Despite this, there is a constant demand for unpasteurised cheese, which may be perceived as a superior product. The manufacture of unpasteurised cheeses must be very carefully managed, with the application of effective control measures. Pasteurised milk for cheese production has a bacterial flora consisting of thermoduric organisms that have survived pasteurisation, such as corynebacteria, micrococci, enterococci, spores of Bacillus and Clostridium, and postpasteurisation contaminants, including coliforms and psychrotrophic Gramnegative organisms. 5.3.2
Starter cultures
The acidification of milk is the key step in the making of cheese. Acidification is essential for the development of both flavour and texture; it promotes coagulation; and the reduction in pH inhibits the growth of pathogens and spoilage organisms. It is normally achieved by the fermentation of lactose by bacterial starter cultures to produce lactic acid, although some fresh cheeses, such as cottage cheese, may be acidified by the direct addition of acid, and do not require a starter. In the past, acidification was achieved by the development of the resident microflora of the milk, and this method is still used in some traditional, artisan cheeses. However, this process is difficult to control and tends to give a variable product that may suffer from taints and inconsistent flavours. Therefore, most cheese is now produced using a carefully selected starter, which gives predictable and desirable results. Lactococcus lactis, Streptococcus thermophilus, Lactobacillus helveticus and Lactobacillus delbrueckii are the primary species of starter bacteria used in cheese manufacture. The use of frozen, concentrated cultures that can be added 63
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directly to the cheese vat is becoming common, for reasons of convenience and to minimise the risk of contamination. For Cheddar, the starter is normally added at a concentration of 106 - 107 cells/ml. Some of the commonly used starter organisms used in specific cheeses are shown in Table 5.I. The choice of starter depends on the type of cheese being produced. The temperature of scalding, or cooking, of the curd is an important consideration. Below 30 °C, mesophilic starters, singly, or in combination, are used, such as L. lactis subsp. lactis, L. lactis subsp. cremoris, and Leuconostoc spp. Where scalding temperatures are higher (45 - 55 °C), as in Swiss cheeses and very hard cheeses, thermophilic starters (whose optimum growth temperature is 40 °C) are required, such as Str. thermophilus and L. delbrueckii subsp. bulgaricus. Other properties of starter cultures that are important include proteolytic activity, which is important in starter function and flavour development during ripening, and citrate metabolism, which is required for the production of the flavour compound diacetyl in some varieties. Sometimes, the rate of acid production by the starter is slower than expected. This 'starter failure' can result in a poor quality product and may also enable the growth of pathogens, particularly Staphylococcus aureus, before an inhibitory pH is achieved. The most common cause of starter failure is infection of the culture with a bacteriophage. This may be a serious economic problem, but is controlled by careful starter strain selection and the application of rigorous hygiene procedures to prevent contamination. In recent years, there has been much interest in the development of transconjugant starter strains with improved phage resistance. Starter failure may also be caused by the presence of antibiotic residues in the milk, usually as a result of their use to treat animals with mastitis. Therefore, it is normal practice to test all incoming milk for the presence of these residues. Sanitiser residues may also cause starter failure, particularly quaternary ammonium compounds. Other non-starter microorganisms are also essential for the manufacture of certain types of cheese. For example, Propionibacterium freudenreichii is used in the manufacture of some Swiss cheeses, such as Emmental and Gruyère, because it metabolises lactic acid to produce carbon dioxide and propionic acid. The gas is needed for the formation of the characteristic eyes in the cheese, and the propionic acid contributes towards the sweet, nutty flavour of these cheeses. Surface smearripened cheeses, such as Brie, Limburger and Munster are ripened using smearflora that consists of Brevibacterium linens, micrococci and yeast. B. linens produces an orange-red growth, and is strongly proteolytic contributing to typical odours and flavours in the cheese. Micrococcus spp., for example Micrococcus virans, Micrococcus caselyticus and Micrococcus freudenreichii, promote proteolysis during ripening and are responsible for the characteristic yellow to deep red colour of the cheese surface. Yeasts e.g. Geotrichum candidum, Candida spp. and Debaryomyces spp. contribute to flavour and colour development. Soft cheeses such as Brie and Camembert are ripened by the surface growth of mould spores (Penicillium camembertii and (or) Penicillium caseicolum), and blue-
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veined cheeses such as Stilton and Roquefort rely on inoculation of the body of the cheese with Penicillum roquefortii spores, plus aeration, to ripen. Recently there has been some interest in the addition of probiotic organisms to cheese, which are claimed to improve gastrointestinal health, to cheese. Probiotic strains of Lactobacillus acidophilus and Lactobacillus rhamnosus have been added to fresh cheeses, but most strains do not survive the ripening process in other varieties. 5.3.3
Curd formation
In curd cheeses, a coagulant is normally added to the acidified milk. For varieties such as Cheddar, this is done approximately 30 - 45 minutes after adding the starter, but in other cheeses acidification may be allowed to proceed further. TABLE 5.I Lactic acid bacteria (LAB) employed as starter cultures Bacteria
Examples of usage
L. lactis subsp. cremoris, L. lactis subsp. lactis Leuconostoc spp.
Soft, unripened cheese e.g. Cottage Quarg, cream cheese, Neufchâtel
Str. thermophilus, L. delbrueckii subsp. bulgaricus, L. helveticus
Soft, unripened cheese (rennetcoagulated) e.g. Mozzarella
L. lactis spp. cremoris P. camembertii, Yeasts
Surface mould-ripened cheese e.g. Brie, Camembert, Coulommier
L. lactis spp. cremoris, L. lactis subsp. lactis
Surface bacterial smear-ripened cheese e.g. Limburger
Str. thermophilus, L. delbrueckii subsp. bulgaricus
Pickled cheese e.g. Feta
L. lactis subsp. cremoris and L. lactis subsp. lactis or L. lactis subsp. cremoris alone
Hard-pressed cheese e.g. Cheddar, Cheshire, Dunlop, Derby, Double Gloucester, Leicester Semi-hard cheese e.g. Gouda, Edam Lancashire, Caerphilly
Str. thermophilus with L. delbrueckii subsp. lactis or bulgaricus
Hard cheese with eyes e.g. Emmental Gruyère Very hard cheese e.g. Parmesan, Asiago
L. lactis subsp. lactis Lactococcus lactis biovar diacetylactis
Blue-veined cheese e.g. Stilton, Danish Blue, Roquefort, Mycelia, Gammelost
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Traditionally, enzymic coagulation by rennet, made from the stomachs of young calves, was used. Recently, however, concerns about shortages of animal rennet, and increasing demand for vegetarian cheeses, have generated interest in microbial rennet. This may consist of acid proteinases produced by moulds such as Mucor miehei, or chymosin (the most important component of rennet) produced by fermentation using genetically modified bacteria. Rennet, in combination with acid from the starter, causes coagulation of the milk curd by precipitating casein as an aqueous gel. The curd is then allowed to set for a time depending on the cheese variety. For most hard or semi-hard cheeses, this would be approximately one hour. During this time, the curd becomes more rigid and its water-retaining capacity decreases for Cheddar, an acidity of about 0.1 - 0.2% is reached, at which point the curd is cut. Cutting the curd into small cubes leads to syneresis (expulsion of whey and contraction of curd). The mixture is then scalded or cooked at a temperature determined by the cheese variety (38 - 40 °C for Cheddar). This process helps to expel more whey and is important in producing the correct curd characteristics. When the acidity and curd firmness reach the correct level, the whey is separated from the curd. In Cheddar-type cheeses, the curd is then subjected to a process of compressing and stretching (cheddaring), which fuses the curd into a mat. Traditionally, this was done manually, by piling and turning slabs of curd, but the process is now mechanised in cheddaring towers. The starter bacteria continue to grow during this process, reaching a population of 108 - 109 cells /ml, and a final acidity of 0.6 - 0.7%. The curd is then milled, salted, moulded and pressed. Throughout this process, it should be noted that the temperature is maintained at a suitable level for starter growth. This temperature will also favour the growth of contaminating spoilage organisms. 5.3.4
Salting/brining
In the manufacture of Cheddar, salt is added to the milled curd before pressing (dry salting) at a concentration of 1.5 - 2% w/w. In other varieties, such as Gouda and Camembert, the moulded cheese is immersed in a concentrated brine. Some blue cheeses are salted by rubbing dry salt into the surface of the moulded cheese. Salting inhibits the growth of the starter culture and other microorganisms, contributes to the flavour, and affects texture. 5.3.5
Ripening
All but fresh cheeses require some degree of ripening for the full development of flavour and texture. During ripening, further moisture loss occurs, and a complex combination of microbial and enzymic reactions take place, involving milk enzymes, the coagulant, and proteases and peptidases from the starter culture and non-starter organisms, which remain viable although their growth is inhibited. Ripening conditions vary with cheese variety. Soft, high-moisture cheeses are
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ripened for relatively short periods, whereas hard, strongly flavoured cheeses may ripen for more than a year. Surface-ripened cheeses require quite a high humidity, but most hard cheeses must be kept in dry conditions to inhibit surface microbial growth. Temperature also varies, and Cheddar is normally ripened at approximately 10 °C. Blue-veined cheeses are made to have an open texture so that sufficient oxygen is present in the cheese to allow the growth of P. roquefortii throughout, but the process may be assisted by piercing the cheese with metal rods to improve gaseous exchange. 5.4
Processed Cheese
Processed cheeses are produced by milling and mixing naturally-produced cheeses until a plastic mass is formed, usually with additional ingredients such as cream, dry milk, whey, and emulsifying salts such as polyphosphates. The mass is then melted and heated at temperatures of 85 - 95 °C, or as high as 115 °C for several minutes. The molten cheese is then formed into slices or portions and packaged. Some products are processed at a sufficiently high temperature to render them ambient-stable if sufficient preservatives such as salt, lactic acid and potassium sorbate are present. 5.5
Value-added Cheese
Traditional cheese varieties are increasingly modified to create new products by the addition of ingredients such as herbs, nuts and dried fruits. Different varieties may also be processed and then combined to form layered products. The microbiology of these products can be complex, since both the microflora and environmental conditions are altered by the addition of new ingredients. The safety and stability of these cheeses must be carefully considered during development. 5.6
Spoilage
Microbial spoilage of cheese can be caused by both bacteria and fungi, but the type of spoilage depends very much on the characteristics of individual cheese varieties. Both visual and organoleptic defects may result, either on the surface of the cheese or internally. 5.6.1
Fungal spoilage
Although the growth of moulds on the surface or in the body of some cheese varieties is essential for ripening, mould growth is generally not desirable. Mould spoilage is usually unpleasant in appearance, and may result in musty taints and odours. Moulds are also responsible for liquefaction of the curd. There is also the
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possibility of mycotoxin production in some cases. Moulds commonly involved in cheese spoilage include members of the genera Penicillium, Aspergillus, Cladosporium, Mucor, Fusarium, Monilia and Alternaria (2). Effective hygiene is important in the control of mould spoilage in cheese, particularly in ripening rooms, and rigorous cleaning procedures are needed to prevent the accumulation of mould spores. Filtered sterile air supplies, or ultraviolet light treatment may also be used to control contamination. The use of vacuum and modifiedatmosphere packaging helps to prevent mould growth on pre-packed cheese, but growth may still occur in residual air pockets or in packs that are improperly sealed or become punctured. Where permitted, antifungal agents such as sorbic acid or natamycin may be incorporated into packaging. Yeasts may cause spoilage of fresh cheeses, such as cottage cheese, during storage, resulting in gas production and off-flavours and odours. Yeast may also proliferate on the surface of ripened cheeses, especially if the surface becomes wet, causing slime formation. Yeasts most frequently isolated from spoiled cheese include Candida spp., Yarrowia lipolytica, Pichia spp., Kluyveromyces marxianus, G. candidum and Debaryomyces hansenii (2 - 5). 5.6.2
Bacterial spoilage
In fresh cheeses with a sufficiently high pH, such as cottage cheese, bacterial spoilage may occur. This is likely to be caused by Gram-negative, psychrotrophic species, such as pseudomonads and some coliforms. These organisms may contaminate the product through water used to wash the curd. Pseudomonas spp., Alcaligenes spp., Achromobacter spp. and Flavobacterium spp. are the psychrotrophic bacteria of concern. Pseudomonas fluorescens, Pseudomonas fragi and Pseudomonas putida cause bitterness, putrefaction and a rancid odour, liquefaction, gelatinisation of curd, and slime and mucous formation on cheese surfaces. Alcaligenes viscolactis is responsible for ropiness and sliminess in cottage cheese, and Alcaligenes metacaligenes for ‘flat, flavourlessness’ in cottage cheese. Psychrotropic Bacillus spp. cause bitterness and proteolytic defects (6). Bacteria may also cause spoilage by the production of internal gas in the cheese, resulting in slits, small holes or blown packs. This may happen in fresh cheese, early in the ripening phase ('early blowing'), or well into the ripening stage ('late blowing'). Early blowing is usually caused by members of the Enterobacteriaceae, but other organisms, such as Bacillus spp., are sometimes involved. The problem can be effectively controlled by adequate hygiene and process control in manufacturing. Late blowing, which may occur after 10 days in varieties such as Gouda, or after several months in some Swiss cheeses, is caused by clostridia that are able to produce butyric acid from lactate. Late blowing sometimes also occurs in Cheddar. Species commonly involved are Clostridium butyricum, Clostridium tyrobutyricum and Clostridium sporogenes, spores of which survive pasteurisation and can be present in cheese milk. Contamination of milk with these organisms is 68
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often seasonal (C. tyrobutyricum is more prevalent in winter), and is related to the inclusion of silage in the diet of dairy cows. A very low level of contamination may be sufficient to cause late blowing. In some countries, nisin, a natural antimicrobial produced by strains of L. lactis, has been used successfully to control late blowing, by inhibiting the growth of clostridia. Small, irregular slits may also sometimes appear in 3- to 6-week-old Cheddar, and this 'intermediate blowing' is thought to be associated with the presence of non-starter gas-producing lactobacilli. 5.6.3
Discolouration
Yeast and enterococci have been found responsible for white spots on brine-salted cheeses (2). Surface mould growth by species such as Aspergillus niger, may cause discoloration of hard cheeses. Discoloration within the cheese is not common, but pigmented strains of certain lactobacilli have been linked with 'rusty spots' in some cheeses, and non-starter Propionibacterium spp. may cause brown or red spots in Swiss cheese (2, 7). P. fluorescens forms water-soluble pigments while other pseudomonads cause darkening and yellowing of curd. Yellow discolouration may be attributed to flavin pigment formation by Flavobacterium spp., and Bacillus spp. have been associated with dark pigment formation (6). 5.7
Pathogens: Growth and Survival
The safety record for cheese is relatively good considering the very large quantities that are consumed worldwide. However, there have been a number of serious outbreaks of foodborne disease associated with cheese, and these are well documented. The most serious outbreaks have been caused by Listeria monocytogenes, salmonellae and enteropathogenic Escherichia coli (EPEC). In recent years, a number of E.coli O157 outbreaks, linked to cheese, have been recorded. Cheeses made from raw milk are particularly at risk since they may become contaminated by pathogens initially present in the milk. Pathogens may also enter cheese during processing, if hygiene and process controls are inadequate. The characteristics of individual cheese varieties greatly influence the potential presence and survival of pathogens. Process and storage temperature, acid production by starter cultures and the addition of salt are all important. In general, soft and semi-soft cheeses with high water activities present fewer barriers to pathogen survival and growth than do hard cheeses. For example Listeria is able to multiply in soft, surface ripened cheeses, such as Brie and Camembert, but is unable to grow in properly made Cheddar, although it may survive for long periods.
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5.7.1
Listeria spp.
An outbreak of listeriosis in California, in 1985 involved 142 cases and resulted in 48 deaths. This outbreak was associated with Mexican-style cheese, and contributed greatly to the establishment of L. monocytogenes as a foodborne pathogen (9). The processing environment and equipment were found to be contaminated and the proper pasteurisation of the cheese milk was questioned (10 - 12). During the period 1983 - 1987 other serious outbreaks associated with soft cheeses, such as Vacherin Mont d'Or, in Switzerland, were reported. In 1995, an outbreak in France causing four deaths was linked to Brie de Meaux cheese made from raw milk (13), and in early 2000 a further outbreak in France was linked to soft cheese. The sale of illicitly produced or distributed fresh, unripened cheese made from raw milk has been associated with several listerial outbreaks as recently as 2003, in the Hispanic community. This outbreak resulted in one foetal death and the death of a neonate (14). These outbreaks illustrate the serious problems posed by L. monocytogenes in cheese production. L. monocytogenes is a psychrotrophic, fairly heat-tolerant pathogen, ubiquitous in the environment, and can also be found in raw milk. It may therefore enter the cheese process by a variety of routes, particularly in smaller, traditional operations where hygiene procedures may be poor. Surface-ripened cheeses are especially vulnerable to recontamination and growth of the organism. As the ripening process proceeds, the development of mould on the surface raises the pH from around 5.0 up to 6.0 - 7.0. This, combined with the high moisture content and temperature of the ripening rooms (8 - 12 °C), creates conditions in which rapid growth of L. monocytogenes is possible. Counts of 107 cfu/g have been demonstrated at the surface of Camembert after 56 days (15). The same process may occur during the ripening of blue-veined cheeses. Although growth of Listeria is much less likely to occur in other cheese varieties where there is no rise in pH during ripening, the organism may survive for long periods. For example, viable cells have been found in Cheddar cheese stored for 434 days (16), and raw-milk soft or semi-hard cheese that had undergone aging for approximately 60 days was implicated in an outbreak in Canada in 2002 (14). This casts some doubt on the recommendation to hold Cheddar and some other hard cheeses made from raw milk, at, or above, 1.7 °C for at least 60 days as a control for Listeria and other pathogens. For these reasons, it is essential that adequate hygiene procedures are practised during cheese manufacture and ripening to prevent environmental contamination with L. monocytogenes. Environmental testing for the organism is also recommended. This is equally true for cheese made from raw or pasteurised milk. In addition, control of the bacteriological quality of raw milk used to make cheese is important, and can help to reduce the incidence of Listeria in raw milk cheeses. End product testing is also widely practised with susceptible cheese varieties, but this can never be sufficient to assure the safety of the product. Surface-ripened soft cheeses made from raw milk are inherently hazardous products, although the amount of attention given to this problem has led to recent
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improvements. In 1996, a UK survey of raw milk soft cheeses showed only one of 72 samples tested contained L. monocytogenes (21), at a level of 1% (6), but it is possible that pathogens may adapt to acid conditions over time, and the effect of this adaptation on survival should be considered. There is also a trend towards the development of milder-flavoured products with significantly lower levels of acid. Pathogen survival in these products may be significantly enhanced. Indeed, the length of time over which viable Salmonella typhimurium cells could be recovered from inoculated fermented milk was found to increase at lower levels of acid production (7). The demand for fermented milk has lead to the manufacture of these products in unapproved premises; as was highlighted in March 2007 by a Food Alert issued by the Food Standards Agency. Therefore, it is not advisable to rely on low pH and acid production to ensure product safety; effective hygiene procedures to prevent pathogen contamination during processing are also necessary. 6.9.1
Listeria monocytogenes
It is generally considered that L. monocytogenes is unlikely to be able to grow in fermented milks, but survival in the finished product is possible. 86
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The behaviour of L. monocytogenes in fermented milks has recently been reviewed (8). It has been found that the organism may be able to grow in some buffered culture media used for the preparation of starters, and that contaminated starter cultures are a potential source of Listeria in the finished product. Studies with both cultured buttermilks and yoghurts inoculated with L. monocytogenes before fermentation showed that survival was influenced by starter culture type, fermentation temperature and final acidity. In some fermented buttermilks, viable cells could be recovered after twelve and a half weeks of refrigerated storage (9). Survival times in yoghurt have been found to be shorter, and, in general, the lower the pH of the finished product, the shorter the survival time. Survival of L. monocytogenes inoculated into yoghurt after fermentation (possibly a more realistic scenario) has also been investigated. Survival for up to 3 weeks was recorded, although the majority of the cells were inactivated in the first 12 days (10). A UK survey of 100 samples of retail and farm-produced yoghurts showed that all the samples were negative for L. monocytogenes (11). 6.9.2
Escherichia coli
In general, E.coli is rapidly inactivated by lactic fermentation; a study showed that rapid inactivation of E.coli occurred in 4 days at 7.2 °C when it was added to yoghurt samples (12). However, the unusual acid tolerance of verotoxigenic E.coli O157:H7 is of concern, and in 1991 an outbreak occurred in north-west England, associated with locally produced live yoghurt. The organism could not be isolated from the yoghurt or milk, but epidemiological evidence indicated a link (13). Recent studies have demonstrated that E.coli O157:H7 inoculated into commercial yoghurt and other fermented milks, survived for up to 12 days in yoghurt, and for several weeks in sour cream and cultured buttermilk and that the addition of sugar to cultured milk products enhances survival of E.coli O157:H7 (14). Studies have also shown that E.coli O157:H7 capable of producing colonic acid persist longer in yoghurt (15). Contamination of these products with the organism is therefore a potential health hazard, since the infective dose is thought to be low (16). 6.9.3
Staphylococcus aureus
Staph. aureus is very unlikely to grow in fermented milks; however, a case of staphylococcal food poisoning was reported in 1970. The cause was attributed to the high sugar content of the product, which favoured Staph. aureus growth and toxin formation, while inhibiting the starter culture (lactic acid) (12). Survival in inoculated sour cream, cultured buttermilk and yoghurt has also been shown. In sour cream inoculated at a level of 105 cells/g, viable cells could be recovered after 7 days, but this was not the case at lower inoculation rates (17). The survival of Staph. aureus during fermentation and subsequent storage has also been studied,
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with similar results. At high inoculation rates, viable cells survived through fermentation, but died out during chilled storage (18). 6.9.4
Clostridium botulinum
In 1989, there was a well-documented outbreak of botulism in the UK associated with hazelnut yoghurt. The contamination was not as a result of a problem with the manufacture of the yoghurt itself, but with underprocessed hazelnut purée, added as a flavouring. The purée had been prepared with artificial sweeteners instead of sugar. As a result, the raised water activity allowed C. botulinum spores to germinate and produce toxin (19). Although an unusual case, this incident emphasises the importance of controlling the microbiological quality of those ingredients added after fermentation. Proper application of HACCP principles to new product development processes should minimise the risk of problems like this occurring. 6.9.5
Yersinia/Aeromonas spp.
The ability of these organisms to grow at low temperatures suggests that their presence in fermented milks could be a hazard. The growth and survival of both organisms in yoghurt have been investigated. Aeromonas hydrophila was found to be completely inhibited after 5 days of refrigerated storage, but Yersinia enterocolitica could still be detected at the end of shelf life after 26 days (20). However, as with other pathogens, survival through fermentation and storage is probably dependent on the rate of acid production and the final pH. A later study determined survival times of only 5 days for Y. enterocolitica during chilled storage (21). 6.9.6
Bacillus cereus
Spore germination and growth of B. cereus in fermented milks are prevented by low pH. However, growth of B. cereus has been shown in yoghurt milk at 31 °C, although, as the pH dropped, the growth rate declined, and it ceased at pH 5.7. Although it is possible that high levels could be reached when initial acid production is slow, B. cereus is not normally considered a hazard in fermented milks (22). 6.9.7
Toxins
If the milk used to produce yoghurt and other fermented milks is contaminated with mycotoxins, probably through contaminated animal feed, it is possible that the finished product will also be contaminated. It has been shown that aflatoxins
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are stable during the manufacture of yoghurt and subsequent chilled storage for 21 days (23). Concern has also been expressed regarding mycotoxigenic moulds growing on the surface of yoghurt, following the isolation of the toxigenic species Penicillium frequentans as a contaminant in a commercial yoghurt sample (24). However, since mycotoxin production would be expected to coincide with visible growth, and visibly spoiled products are unlikely to be consumed, this does not seem to be a serious hazard. 6.10
Probiotic Products
Since many probiotic cultures used to ferment milk are slow acid producers, it may be that there is an increased opportunity for contaminating pathogens to grow to dangerous levels before the pH drops to inhibitory levels. For this reason, it becomes even more important to implement effective hygiene procedures to ensure that potential pathogens are not able to contaminate ingredients or the processing environment. Concern has also been expressed over the safety of some probiotic cultures, particularly strains of Enterococcus faecium, which may be an opportunistic pathogen, and display multiple antibiotic resistance. Therefore, considerable care must be exercised in the selection of probiotic organisms, to ensure that they do not present any discernible health risk to consumers. 6.11
References
1. Shin H.-S., Lee J.-H., Pestka J.J., Ustunol Z. Viability of bifidobacteria in commercial dairy products during refrigerated storage. Journal of Food Protection, 2000, 63 (3), 327-31. 2. Schillinger U. Isolation and identification of lactobacilli from novel-type probiotic and mild yoghurts and their stability during refrigerated storage. International Journal of Food Microbiology, 1999, 47 (1-2), 79-87. 3. Kosse D., Seiler H., Amann R., Ludwig W., Scherer S. Identification of yoghurtspoiling yeasts with 185 rRNA-targeted oligonucleotide probes. Systematic and Applied Microbiology, 1997, 20 (3), 468-80. 4. Fleet G.H. Yeasts in dairy products. A review. Journal of Applied Bacteriology, 1990, 68 (3), 199-211. 5. Filtenborg O., Frisvad J.C., Thrane U. Moulds in food spoilage. International Journal of Food Microbiology, 1996, 33 (1), 85-102. 6. Hobbs B.C. General aspects of food poisoning and food hygiene. Journal of the Society of Dairy Technology, 1972, 25 (1), 47-50. 7. Park H.S., Marth E.H. Behaviour of Salmonella typhimurium in skim milk during fermentation by lactic acid bacteria. Journal of Milk and Food Technology, 1972, 35 (8), 482-8.
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DAIRY PRODUCTS 8. Ryser LT. Incidence and behavior of Listeria monocytogenes in cheese and other fermented dairy products, in Listeria,Listeriosis and Food Safety. Eds. Ryser LT., Marth LH. New York, CRC Press. 2007, 405-502. 9. Schaack M.M., Marth E.H. Survival of Listeria monocytogenes in refrigerated cultured milks and yogurt. Journal of Food Protection, 1988, 51 (11), 848-52. 10. Choi H.K., Schaack M.M., March E.H. Survival of Listeria monocytogenes in cultured buttermilk and yoghurt. Milchwissenschaft, 1988, 43 (12), 790-2. 11. Kerr K.G., Rotowa N.A., Hawkey P.M. Listeria in yoghurt? Journal of Nutritional Medicine, 1992, 3 (1), 27-9. 12. International Commission on Microbiological Specifications for Foods. Milk and dairy products. (Microorganisms in milk and dairy products.), in Microorganisms in Foods 6: Microbial Ecology of Food Commodities. Ed. International Commission on Microbiological Specifications for Foods. New York, Kluwer Academic/Plenum Publishers. 2005, 643-715. 13. Morgan D., Newman C.P., Hutchinson D.N., Walker A.M., Rowe B., Majid F. Verotoxin producing Escherichia coli O157 infections associated with the consumption of yoghurt. Epidemiology and Infection, 1993, 111 (2), 181-7. 14. Chang J.H., Chou C.C., Li C.E. Growth and survival of Escherichia coli O157:H7 during the fermentation and storage of diluted cultured milk drink. Food Microbiology, 2000, 17 (6), 579-87. 15. Lee S.M., Chen J. Survival of Escherichia coli O157:H7 in set yoghurt as influenced by the production of an exopolysaccharide, colanic acid. Journal of Food Protection, 2004, 67 (2), 252-5. 16. Dineen S.S., Takeuchi K., Soudah J.E., Boor K.J. Persistence of Escherichia coli O157:H7 in dairy fermentation systems. Journal of Food Protection, 1998, 61 (12), 1602-8. 17. Minor T.E., Marth E.H. Fate of Staphylococcus aureus in cultured buttermilk, sour cream, and yoghurt during storage. Journal of Milk and Food Technology, 1972, 35 (5), 302-6. 18. Pazakova J., Turek P., Laciakova A. The survival of Staphylococcus aureus during the fermentation and storage of yoghurt. Journal of Applied Microbiology, 1997, 82 (5), 659-62. 19. O'Mahony M., Mitchell E., Gilbert R.J., Hutchinson D.M., Begg N.T., Rodhouse J.C, Morris J.E. An outbreak of food borne botulism associated with contaminated hazelnut yoghurt. Epidemiology and Infection, 1990, 104 (3), 389-95. 20. Aytac SA, Ozbas Z.Y. Survey of the growth and survival of Yersinia enterocolitica and Aeromonas hydrophila in yogurt. Milchwissenschaft, 1994, 49 (6), 322-5. 21. Bodnaruk P.W., Williams R.C, Golden D.A. Survival of Yersinia enterocolitica during fermentation and storage of yoghurt. Journal of Food Science, 1998, 63 (3), 535-7. 22. Robinson R.K., Tamime A.Y., Wszolek M. Microbiology of fermented milks, in Dairy Microbiology Handbook: The Microbiology of Milk and Milk Products. Ed. Robinson R.K. New York, John Wiley and Sons. 2002, 367-430.
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FERMENTED MILKS 23. Blanco J.L., Carrion B.A., Liria N., Diaz S., Garcia M.E., Dominguez L., Suarez G. Behaviour of aflatoxins during manufacture and storage of yoghurt. Milchwissenschaft, 1993, 48 (7), 385-7. 24. Garcia A.M., Fernandez G.S. Contaminating mycoflora in yoghurt: General aspects and special reference to the genus Penicillium. Journal of Food Protection, 1984, 47 (8), 629-36.
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7. ICE CREAM AND RELATED PRODUCTS
7.1
Definitions
Cream ices are frozen dairy desserts containing milk fats. Their composition is regulated by legislation in many countries, and varies considerably. In the United States, ice creams must typically contain fat levels of 10% or more (12% for “premium ice cream” and 14% for “super premium ice cream”). In the UK, ice creams must contain no less than 5% fat and 2.5% milk solids. Additional flavourings and ingredients such as nuts and chocolate are often added to create a range of ice cream varieties. Examples of such products include crème glacée, eiskrem, and crema di gelato. Ice cream must also meet minimum fat requirements, but may contain milk fat, vegetable fats, or non-dairy animal fats, Such products include mellorine (used in the US) Ijs (from the Netherlands) and glaces de consummation (Belgium). Countries like France and Germany, prohibit the use of non-dairy fat in ice cream. In the UK, non-dairy fat is permitted in ice cream, but ‘dairy ice cream’ is used to describe those products made exclusively from milk fat. Milk ices are made using milk, but without additional fat. They contain less fat than ice cream (3 - 5%), but higher levels of sugar and non-fat milk solids, e.g. glace au lait, milcheis, gelato al latte. Custards or French ice creams or French custard ice creams are similar to milk ices, but also contain at least 1.5% added egg yolk solids. Ices or water ices are made with fruit juices and/or pulp and water. They may also contain sugar, acid (for example, citric, malic or tartaric), stabilisers (e.g. gelatin, pectin), colour and flavour. These products may be frozen with or without agitation and the incorporation of air. ‘Ice lollies’ are water ices frozen without agitation. Examples of agitated products include ‘Frappe’ made in ‘slush’ conditions, and ‘punch’ made with alcoholic liquid instead of water. Sherbet is similar to water ice, but also contains small quantities of ice cream, liquid milk, milk fat and milk solids. Air is often incorporated into the product during freezing. Sorbets are also similar to water ices but have a high content of sugar, fruit and fruit juice. In addition, the product contains stabilisers and egg white, and has an overrun of 20% or less. Sorbets often contain exotic flavours. Mousse is a flavoured, frozen whipped cream, to which stabilisers are added to maintain texture. 93
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Cassatas are made in round moulds and have various flavoured layers of ice cream. They may also have fruit, liqueurs, chocolate, nuts or slices of sponge cake (sometimes soaked in liqueur). Splits are made on a stick; the core consisting of ice cream and the outer layer made of fruit water ice or chocolate with nuts and/ or biscuit crumbs. Frozen yoghurts are made by freezing a pasteurised mix of milk fat, milk solids non-fat (MSNF), sweeteners, stabilisers, and yoghurt (10 - 20%). They may be flavoured with fruit puree. Other types of ice creams beginning to enter the market or triggering research interest are ice creams with different fat contents, probiotic ice creams and novelties; Ice creams with different fat contents include reduced fat (25% less fat), lowfat (with no more than 3g of fat), and non-fat (less than 0.5g fat) Probiotic ice creams have been investigated, and studies have shown that ice creams could be used to deliver probiotic bacteria, without any change in sensory properties. Novelty products are generally defined as ‘unique single-serve portioncontrolled products’ made from ice cream with special flavours and confectionery. They may be shaped and enrobed in chocolate or water ice, and/or moulded onto a stick or available as cup items e.g. coated ice cream bars, ice cream cakes and logs. 7.2
Initial Microflora
The initial microflora of ice cream prior to pasteurisation is largely determined by the individual ingredients, milk, cream, dried milk, etc. Where flavourings and other ingredients, such as sugar, nuts, fruit and chocolate, are added, this is usually done after pasteurisation. Therefore, there is the potential for such additions to introduce a wide range of other organisms not usually found in dairy products. This must be carefully considered, as it is a potential source of pathogenic organisms. 7.3
Processing and its Effects on the Microflora
A schematic outline of ice cream production is shown in Figure 7.1.
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Fig. 7.1. Production of ice cream 7.3.1
Ingredients
7.3.1.1 Fresh whole milk Fresh whole milk is a good source of fat and non-fat milk solids (NFMS) for the manufacture of milk ices, but, for ice cream, both fat and NFMS levels must be increased by supplementation with other ingredients. It is important that fresh milk used for ice cream has been properly pasteurised, stored correctly to minimise the growth of psychrotrophs, and used quickly. 95
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7.3.1.2 Fresh cream Fresh cream is the best source of additional milk fat, but it is both costly and highly perishable. Alternatives include unsalted butter, sweet cream, and anhydrous milk fat (butter oil). Where non-dairy fats are permitted, partly hydrogenated vegetable oils are often used, particularly palm oil, palm kernel oil and coconut oil. Highly processed fats and oils are unlikely to carry significant microbial contamination, but butter may contain lipolytic bacteria such as Pseudomonas fragi, which may cause tainting. 7.3.1.3 Additional NFMS Additional NFMS (which include sugars, proteins and minerals) can be obtained using concentrated liquid skimmed milk, sweetened condensed milk, dried skimmed milk powder, whey powders and modified liquid whey concentrates. Sweetened condensed milk and whey powders may lead to the formation of large lactose crystals that may result in a ‘sandy’ texture defect. Spray-dried whole milk powders are sometimes used to add both NFMS and milk fat to ice cream, but these products are vulnerable to the development of off-flavours and rancidity. Skimmed milk powders may sometimes be contaminated by large numbers of Bacillus spores, including Bacillus cereus. This is undesirable, both from a public health point of view, and because psychrotrophic bacilli may be able to grow in the ice cream mix and cause eventual spoilage. Dried milk may serve as a source of Listeria monocytogenes, as these organisms are known to survive the spraydrying process. 7.3.1.4 Sugars Sugars are used to sweeten most ice creams, and this also increases the total solids content of the mix. Sucrose is most commonly added, but glucose syrups and dextrose powder are also used, sometimes in combination with sucrose. Few microbiological problems are anticipated with these ingredients, although syrups may support the growth of some osmophilic yeasts (Zygosaccharomyces, Candida, Pichia, Torula), and surface mould growth is also possible. Nowadays, fructose or artificial sweeteners are being used to manufacture diabetic ice cream; the safety and quality of the product may be compromised as the bacterial growth inhibitory effects of artificial sweeteners may not be as effective as those exerted by sugar. Bacteria present could grow before freezing. 7.3.1.5 Stabilisers Stabilisers are added to most ice cream mixes to increase viscosity and give the product the correct texture. A number of different stabilisers can be used, and the most commonly added to ice cream are alginates, carrageenan, carboxymethyl 96
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cellulose, and gums (locust bean, guar and xanthan). Emulsifiers are also added to give the ice cream a smooth texture by preventing the agglomeration of fat globules, and helping to produce smaller air cells during processing. Egg yolk was traditionally used for this purpose, only eggs that have been pasteurised should be used if eggs are added after heat treatment. Glyceryl monostearate, polyoxethylene glycol, and sorbitol esters are now more common, although not all of these are permitted in some countries. These materials should not present any significant microbiological problems, but should be obtained from a reputable source. 7.3.1.6 Colours and flavours Colours and flavours, such as vanilla and chocolate, are also incorporated into most ice cream formulations. Synthetic colours and flavours are now being replaced by natural or 'nature-identical' versions in response to consumer preference. Other value-added ingredients, such as nuts, chocolate chips, and fruit pieces, may also be added. Most flavours are added after pasteurisation, and their microbiological quality is therefore very important, as is the standard of hygiene used in the storage and handling of these ingredients. For example, fruits may support high levels of yeast populations, and nuts may be contaminated by xerophilic moulds, some of which could be mycotoxin producers. Some natural flavouring ingredients, such as coconut and raw spices, are possible sources of pathogens, including Salmonella, and should be heat-treated if possible. Air incorporated into the product must be processed (i.e. filtered) to ensure that it is not contaminated. 7.3.2
Mixing
The calculation of the mix formulation is dependent upon the type of product being manufactured, but it is also influenced by the type of freezing equipment used, and the need to obtain a finished product that has the correct fat to sugar, and solids to water ratios, to give an acceptable texture. Small manufacturers may mix each batch manually in the pasteurisation tank, but in larger operations, the addition of ingredients to each batch by weight or volume may be automated, and a number of batch blending tanks may be used to ensure a continuous flow of mix to the pasteuriser. The hydrated mix is likely to provide suitable conditions for rapid microbial growth, especially if some pre-heating is necessary to disperse dry ingredients. It may be necessary to hold the batch briefly to allow the stabiliser to hydrate, but pasteurisation should generally be carried out as quickly as possible. Excessive microbial growth before pasteurisation could cause tainting, and, in extreme cases, might compromise the effectiveness of the thermal process.
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7.3.3
Heat treatment
The heat treatment of ice cream mixes is often defined in national legislation, and varies slightly from country to country. The stipulated processes are usually based on those applied to milk, but are generally higher. This is to allow for the protective effect of the mix on microbial cells, which confers a higher heat resistance than would be the case in fresh milk. For example, it has been shown that the heat resistance of L. monocytogenes is increased by some of the ingredients used in ice cream mixes, particularly stabilisers. D-values at 54.4 °C for L. monocytogenes in ice cream mix were approximately four to six times those obtained in milk (1). The minimum recommended pasteurisation requirement for ice cream mixes in the UK are not less than 65.6 °C for at least 30 minutes, 71.1 °C for at least 10 minutes, or 79.4 °C for at least 15 seconds (2). Ice cream pasteurisation destroys most vegetative cells and is sufficiently severe to reduce microbial counts to 500/g or less. Most of the survivors are bacterial spores. A sterilised ice cream mix can be obtained by heating the mix to no less that 148 °C for at least 2 seconds (2). Small processors may use low-temperature, long-time pasteurisation (LTLT) conditions in a batch process, but most manufacturers now use high-temperature, short-time (HTST) conditions in plate heat exchangers. Ultra high temperature (UHT) processing may also be applied by direct steam injection, or in scraped surface heat exchangers. One problem with these continuous processes is the very viscous nature of ice cream mixes, which may cause fouling of surfaces in heat exchangers, but may also affect the flow characteristics of the mix. If conditions of laminar, rather than turbulent flow are established, there is a possibility of underprocessing. This effect has been demonstrated for ice cream mixes during HTST processing (2). As the pasteurisation of the ice cream mix is essential for product safety and microbiological quality, it is extremely important to ensure that the mix receives an adequate heat treatment. 7.3.4
Homogenisation
The size of the fat globules in the mix must be reduced during processing to improve the whipping and air incorporation properties of the product. This is usually done by homogenisation. The homogeniser is often incorporated into the pasteurising equipment and may act as the metering unit for the HTST pasteuriser. In some cases, homogenisation is carried out downstream of the pasteuriser. This may cause microbiological problems as a result of the complexity of homogenisers, which are difficult to clean and sanitise effectively, and may act as sites of recontamination for heat-treated mix. It is recommended that homogenisation be carried out before, or during, pasteurisation wherever possible.
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7.3.5
Cooling and ageing
In the UK, after pasteurisation it is recommended that the mix is cooled as quickly as possible to no more than 7.2 °C within a maximum time of 1.5 hours. This recommendation does not apply if the mix is sterilised and then transferred immediately to a sterile airtight container under aseptic conditions, and the container remains unopened prior to freezing (18). The mix is then held at that temperature for a time before freezing. This process is known as ageing, and is necessary to allow further physical changes to occur. During ageing, stabilisers and milk proteins hydrate further, and fat crystallisation occurs. Ageing should normally be completed within 24 hours, since longer holding times present a risk of psychrotrophic growth, either by spore-formers that have survived pasteurisation or by post-process contaminants. This may result in spoilage of the mix before freezing. Adequate temperature control during ageing is critical, as is effective cleaning of storage tanks and processing equipment to minimise recontamination of the mix. 7.3.6
Freezing
Ice cream freezing is usually a two-stage process. In the first stage, which may be a batch or continuous process, the mix is cooled to at least -2.2 °C (preferably -5 to -10 °C) whilst air is incorporated into it. If temperatures rise above -2.2 °C the product must be reheated. The incorporation of air in the frozen mix causes an increase in volume (known as the overrun). The overrun varies and may be up to 100%, depending on the nature of the product. It has been shown that freezing using batch freezers results in significant destruction of bacterial cells, probably through mechanical damage caused by ice crystals, but, in continuous systems, which freeze more rapidly, the destructive effect is much less marked (4). Effective cleaning and sanitation of ice cream freezers are important to prevent recontamination of the mix during freezing. Many designs are difficult to clean thoroughly, although large-scale continuous freezers may now incorporate cleanin-place (CIP) systems. After the initial freezing process, the ice cream may be packed directly into the final packaging, shaped in a mould, frozen onto a stick, coated or enrobed in chocolate, or may have other ingredients, such as nuts, added. The product is then immediately cooled further to -25 to -30 °C by the second stage of freezing, referred to as hardening. This is carried out either in freezing tunnels or in hardening rooms. If necessary, further final packaging is then applied and the product is stored at about -25 °C or less. Once the ice cream is frozen hard (core temperature of -18 °C), all microbial growth is prevented. However, the finished product must be of a high microbiological standard, as many pathogens are able to survive for long periods in ice cream. For example, Salmonella has been shown to survive for 7 years in ice cream (5).
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7.4
Distribution
Although no microbial growth can occur in ice cream during storage, there is an opportunity for further contamination to occur at the point of sale. This is particularly the case with bulk products that are dispensed by an operative and presented to the consumer, such as ice cream sold in cones. Microbial contamination may come directly from the operative, or from poorly cleaned and handled utensils used to dispense the product. For example, ice cream scoops are usually kept in water when not in use, and the growth of microorganisms in this water can cause significant contamination of the scoop, and hence the ice cream (6). Training and personal hygiene of those handling ice cream are therefore very important. 7.4.1
Soft-serve ice cream
Soft-serve ice cream differs from other ice cream products in that it is frozen at the point of sale and does not undergo hardening. The pasteurised mix may be transported to the retail outlet, where it is sold directly from a special dispensing freezer into cones, or onto prepared desserts. Alternatively, the mix may be UHT processed and aseptically packed, or prepared on site from a dried powder blend, or by a conventional process. This system presents a number of opportunities for microbial contamination to occur. Temperature abuse during transport and storage of the unfrozen mix is quite likely, allowing sufficient bacterial growth to cause spoilage. Contamination of mixes during preparation on site is also possible. Inadequate cleaning and sanitation of dispensing freezers may also be a problem, and it is necessary to dismantle and clean such equipment daily. Contamination by L. monocytogenes is of particular concern. Some dispensing freezers are now designed to be 'self pasteurising', where all product contact surfaces and residual mixes within the freezer are heated to at least 65 °C for 30 minutes, and then cooled rapidly to 4 °C. A recent UK survey of soft-serve ice cream from fixed and mobile retail outlets showed that there is still cause for concern over the microbiological quality of these products (7). 7.5
Spoilage
Microbiological spoilage will occur only if there is sufficient delay between pasteurisation and freezing. Pasteurisation will destroy most potential spoilage organisms apart from the spores of psychrotrophic bacilli, and microbiological growth does not take place in correctly frozen products. Therefore, the cooling and ageing steps in the process are the most vulnerable for spoilage. This is particularly true if cleaning and sanitation of post-pasteurisation equipment are inadequate, or if flavourings and other ingredients added after pasteurisation are of poor microbiological quality. Therefore, effective control and monitoring of
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plant hygiene, ingredient quality, and the temperature of mixes between pasteurisation and freezing are vital to prevent spoilage. The potential for spoilage of soft-serve ice cream mixes has already been mentioned, and it has been shown that even moderate temperature abuse of stored mixes can lead to the development of high bacterial counts and eventual spoilage (8). 7.6
Pathogens: Growth and Survival
Ice creams have a relatively good recent record from a food safety point of view, probably because of the effect of the heat treatment regulations that have been introduced in many countries. Most outbreaks of foodborne disease associated with ice cream have involved ice cream made from raw milk, or home-made products that have used raw milk, cream or eggs, inadequate heat treatment or been contaminated during handling. For example, a recent outbreak of Salmonella enteritidis infection involving 30 children, following a birthday party in the UK, was associated with the consumption of home-made ice cream made using raw shell eggs (9). Nevertheless, there have been a number of instances of foodborne disease associated with commercially produced ice cream. 7.6.1
Salmonella
Salmonellae are able to survive for very long periods in ice cream, and, although they will not survive adequate pasteurisation, post-process contamination or the use of raw eggs and failure to pasteurise the ice cream mix, is a serious risk. In 1994, a very large outbreak of S.enteritidis infection occurred in Minnesota and other States. The outbreak was estimated to have affected 224,000 people and was associated with a nationally distributed ice cream brand. This was the largest Salmonella outbreak ever recorded in the US. The investigation concluded that the probable cause was cross-contamination of pasteurised ice cream mix in tankers also used for transporting unpasteurised raw eggs. The mix was not subsequently repasteurised (10). The infective dose in this outbreak was later calculated as only about 28 cells (11). 7.6.2
Listeria monocytogenes
There has been some concern over the presence of L. monocytogenes in ice cream, particularly in view of its ability to grow at low temperatures, and its relatively high heat resistance. It is generally considered that the pasteurisation conditions used in the UK are sufficient to destroy the organism, but that more marginal processes applied elsewhere could be less effective, especially in view of the protective effect of stabilisers mentioned in section 7.3.1.5 . Post-pasteurisation contamination is a potential problem, especially in mixes that are held for long periods prior to freezing. It should be noted that L. monocytogenes has been 101
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shown to be dispersed in aerosols even at temperatures below 0 °C (12). There have been a number of large recalls of frozen dairy products in the US since 1985, including ice cream bars, vanilla ice milk, and sherbet, because of Listeria contamination, although it is not clear whether any of these products caused any cases of illness (13). However, L. monocytogenes has been shown to survive freezing and storage in frozen foods for 14 weeks at -18 °C with no reduction in numbers of viable cells (14). Sporadic cases of listeriosis have been reported in Belgium. One notable case was that of a 62 year old immunocompromised man, who consumed ice cream contaminated with L. monocytogenes (15). 7.6.3
Staphylococcus aureus
Staph. aureus will not survive ice cream pasteurisation and does not grow at low temperatures. It may be a post-process contaminant introduced via flavourings and other ingredients, or from personnel (via nasal and hand carriers), but is not able to grow and produce enterotoxin unless severe temperature abuse occurs. An outbreak of this type occurred in 1945 at an army hospital in the UK, where a heattreated mix was cooled slowly overnight before freezing 20 - 30 hours later. Around 700 people were affected (16). 7.6.4
Bacillus cereus
Although there is some concern that psychrotrophic B. cereus spores might survive pasteurisation and then grow in the mix during ageing, it seems unlikely that the population would reach sufficient levels to cause illness. However, if the initial number of spores was very high, and time and temperature control after pasteurisation was not adequate, the population could reach high levels, especially in soft-serve mixes. B. cereus has been isolated from samples of ice cream (17) and there are reports of outbreaks linked to ice cream (18). 7.6.5
Other pathogens
Food handlers were thought to be responsible for an outbreak of verocytotoxinproducing Escherichia coli (VTEC) in 2007. The ice cream, consumed at two birthday parties and at a farm, resulted in five cases of haemolytic uraemic syndrome (HUS) in children, and seven cases of severe diarrhoea (19). These organisms are not heat-resistant and do not grow at low temperatures, but their low infective dose, and their general ability to survive in unfavourable environments suggest that they could pose a serious risk to consumers if inadequate heat treatment or post-pasteurisation contamination occur. There have also been occasional outbreaks of disease associated with the handling of ice cream during manufacture or at the point of sale. These include a major outbreak of typhoid fever in Wales in 1947, which affected 210 people, with four deaths. The ice cream producer was found to be a urinary excreter of 102
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Salmonella typhi. It was following this outbreak that regulations were introduced in the UK regarding heating of ice cream mixes prior to freezing (18). Outbreaks of paratyphoid, shigella dysentery, and Hepatitis A, as a result of handling by infected individuals, have also been reported, (16, 20). These incidents confirm the importance of health checks and hygiene training for ice cream vendors. 7.7
Toxins
Any risk from mycotoxins in ice cream is likely to be a reflection of ingredient quality. Nuts are the most likely source of aflatoxins, and it is important to ensure that nuts used in ice creams are of high quality, with no evidence of mould growth. 7.8
References
1. Holsinger V.H., Smith P.W., Smith J.L., Palumbo S.A. Thermal destruction of Listeria monocytogenes in ice cream mix. Journal of Food Protection, 1992, 55 (4), 234-7. 2. Papademas P., Bintsis T. Microbiology of ice cream and related products, in Dairy Microbiology Handbook: The Microbiology of Milk and Milk Products. Ed. Robinson R. New York, John Wiley. 2002, 213–60. 3. Davidson V.J., Goff H.D., Flores A. Flow characteristics of viscous, non-Newtonian fluids in holding tubes of HTST pasteurisers. Journal of Food Science, 1996, 61 (3), 573-6. 4. Alexander J., Rothwell J. A study of some factors affecting the methylene blue test and the effect of freezing on the bacterial content of ice cream. Journal of Food Technology, 1970, 5, 387-402. 5. Georgala D.L., Hurst A. The survival of food poisoning bacteria in frozen foods. Journal of Applied Bacteriology, 1963, 26 (3), 346-58. 6. Wilson I.G., Heaney J.C.N., Weatherup S.T.C. The effect of ice cream-scoop water on the hygiene of ice cream. Epidemiology and Infection, 1997, 119 (1), 35-40. 7. Little C.L., de Louvois J. The microbiological quality of soft ice cream from fixed premises and mobile vendors. International Journal of Environmental Health Research, 1999, 9, 223-32. 8. Martin J.H., Blackwood P.W. Effect of pasteurisation conditions, type of bacteria, and storage temperature on the keeping quality of UHT-processed soft-serve frozen dessert mixes. Journal of Milk and Food Technology, 1971, 34, 256-9. 9. Dodhia H., Kearney J., Warburton F. A birthday party, home-made ice cream, and an outbreak of Salmonella enteritidis phage type 6 infection. Communicable Disease and Public Health, 1998, 1 (1), 31-4. 10. Hennessy T.W., Hedberg C.W., Slutsker L., White K.E., Besser-Wiek J.M., Moen M.E., Feldman J., Coleman W.W., Edmonson L.M., MacDonald K.L., Osterholm M.T. A national outbreak of Salmonella enteritidis infections from ice cream. New England Journal of Medicine, 1996, 334 (20), 1281-6.
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DAIRY PRODUCTS 11. Vought K.J., Tatini S.R. Salmonella enteritidis contamination of ice cream associated with a 1994 multistate outbreak. Journal of Food Protection, 1998, 61 (1), 5-10. 12. Goff H.D., Slade P.J. Transmission of a Listeria sp. through a cold-air wind tunnel. Dairy, Food and Environmental Sanitation, 1990, 10 (6), 340-3. 13. Ryser E.T. Incidence and behaviour of Listeria monocytogenes in unfermented dairy products, in Listeria, Listeriosis and Food Safety. Eds. Ryser LT., Marth E.H. New York, CRC Press. 2007, 357-403. 14. Palumbo S.A., Williams A.C. Resistance of Listeria monocytogenes to freezing in foods. Food Microbiology, 1991, 8 (1), 63-8. 15. Andre P., Roose H., Van Noyen R., Dejaegher L., Uyttendaele I., de Schrijver K. Neuro-meningeal listeriosis associated with consumption of an ice cream. Médecine et Maladies Infectieuses, 1990, 20, 570-2. 16. Hobbs B.C., Gilbert R.J. Food Poisoning and Food Hygiene. London, Arnold. 1978. 17. Ahmed A.A-H., Moustafa M.K., Marth E.H. Incidence of Bacillus cereus in milk and some milk products. Journal of Food Protection, 1983, 46 (2), 126-8. 18. Griffiths M.W. Milk and unfermented milk products, in The Microbiological Safety and Quality of Food, Volume 1. Eds. Lund B.M., Baird-Parker T.C., Gould G.W. Gaithersburg, Aspen Publishers. 2000, 507-34. 19. De Schrijver K., Possé B., Van den Branden D., Oosterlynck O., De Zutter L., Eilers K., Piérard D., Dierick K., Van Damme-Lombaerts R., Lauwers C., Jacobs R. Outbreak of verocytotoxin-producing E.coli O145 and O26 infections associated with the consumption of ice cream produced at a farm, Belgium, 2007. Eurosurveillance, 2008, 13 (7), 8041. 20. MacDonald K.L., Griffin P.M. Foodborne disease outbreaks, annual summary, 1982. Morbidity and Mortality Weekly Report, 1983, 35, 7.
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8. HACCP
8.1
Introduction
The Hazard Analysis Critical Control Point (HACCP) system is a structured, preventative approach to ensuring food safety. HACCP provides a means to identify and assess potential hazards in food production and establish preventive control procedures for those hazards. A critical control point (CCP) is identified for each significant hazard, where effective control measures can be defined, applied and monitored. The emphasis on prevention of hazards reduces reliance on traditional inspection and quality control procedures and end-product testing. A properly applied HACCP system is now internationally recognised as an effective means of ensuring food safety. The HACCP concept can be applied to new or existing products and processes, and throughout the food chain from primary production to consumption. It is compatible with existing standards for quality management systems such as the ISO 9000-2000 series, and HACCP procedures can be fully integrated into such systems. The new ISO 22000 food safety standard formally integrates HACCP within the structure of a quality management system. HACCP is fully integrated into the British Retail Consortium (BRC) Global Standards for Food Safety, and is one of the ‘fundamental’ requirements of that system. The application of HACCP at all stages of the food supply chain is actively encouraged, and increasingly required, worldwide. For example, the Codex Alimentarius advises that 'the application of HACCP systems can aid inspection by regulatory authorities and promote international trade by increasing confidence in food safety'. In many countries, there is a legal requirement for all food business operators to have some form of hazard analysis based on HACCP as a means of ensuring food safety. For example, within the European Union, Regulations 852/2004 and 853/2004 require a fully operational and maintained HACCP system, according to Codex, to be in place. 8.2
Definitions Control (verb) - To take all necessary actions to ensure and maintain compliance with criteria established in the HACCP plan.
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Control (noun) - The state wherein correct procedures are followed and criteria are met. Control measure - An action and activity that can be used to prevent or eliminate a food safety hazard or reduce it to an acceptable level. Corrective action - An action to be taken when the results of monitoring at the CCP indicate a loss of control. Critical Control Point (CCP) - A step at which control can be applied and is essential to prevent or eliminate a food safety hazard, or reduce it to an acceptable level. Critical limit - A criterion that separates acceptability from unacceptability. Deviation - Failure to meet a critical limit. Flow diagram – A systematic representation of the sequence of steps or operations used in the production or manufacture of a particular food item. HACCP - A system that identifies, evaluates and controls hazards that are significant for food safety. HACCP Plan – A document prepared in accordance with the principles of HACCP to ensure control of hazards that are significant for safety in the segment of the food chain under consideration. Hazard - A biological, chemical or physical agent in, or condition of, food with the potential to cause an adverse health effect. Hazard analysis - The process of collecting and evaluating information on hazards and the conditions leading to their presence to decide which are significant for food safety and therefore should be addressed by the HACCP plan. Monitoring – The act of conducting a planned sequence of observations or measurements of control parameters to assess whether a CCP is under control. Step - A point, procedure, operation or stage in the food chain including raw materials, from primary production to final consumption. Validation - Obtaining evidence that the elements of the HACCP plan are effective. Verification - The application of methods, procedures, tests and other evaluations, in addition to monitoring to determine compliance with the HACCP plan. 8.3
Stages of a HACCP Study
The HACCP system consists of the following seven basic principles:
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1. Conduct a hazard analysis. 2. Identify the CCPs. 3. Establish the critical limit(s). 4. Establish a system to monitor control of the CCP. 5. Establish the corrective action to be taken when monitoring indicates that a particular CCP is not under control. 6. Establish procedure for verification to confirm that the HACCP system is working effectively. 7. Establish documentation concerning all procedures and records appropriate to these principles and their application. It is recommended by the Codex Alimentarius that the practical application of the HACCP principles be approached by breaking the seven principles down into a 12-stage logic sequence. Each stage is discussed below in detail. Figure 8.1 is a flow diagram illustrating this 12-stage logic sequence. 8.3.1
Assemble the HACCP team
HACCP requires management commitment of resources to the process. An effective HACCP plan is best carried out as a multidisciplinary team exercise to ensure that the appropriate product-specific expertise is available. The team should include members familiar with all aspects of the production process as well as specialists with expertise in particular areas such as production, hygiene managers, quality assurance or control, ingredient and packaging buyers, food microbiology, food chemistry or engineering. The team should also include personnel who are involved with the variability and limitations of the operations. If expert advice is not available on-site, it may be obtained from external sources. The scope of the plan should be determined by defining the extent of the production process to be considered and the categories of hazard to be addressed (e.g. biological, chemical and/or physical). 8.3.1.1 Dairy products The HACCP team should ideally have access to expertise on the practices applied at farm level in relation to milk collection, storage and transport. The initial microbial population of raw milk has a significant influence on the safety and quality of processed dairy products. For example, the effectiveness of pasteurisation may be compromised by excessive microbial counts in raw milk, and by the presence of large numbers of pathogens. Therefore, knowledge of primary production procedures is very valuable for the HACCP study.
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1. Assemble HACCP team
2. Describe product
3. Identify intended use
4. Construct flow diagram
5. On-site verification of flow diagram
6. Conduct a hazard analysis List all potential hazards Identify and list control measures
7. Determine CCPs
8. Establish critical limits for each CCP
9. Establish monitoring system for each CCP
10. Establish corrective actions
11. Establish verification procedures
12. Establish documentation and records
Fig. 8.1. Logic sequence for application of HACCP 8.3.2 Describe the product It is important to have a complete understanding of the product, which should be described in detail. The description should include information such as the product name, composition, physical and chemical structure (including water activity (aw), pH, etc.), processing conditions (e.g. heat treatment, freezing, fermentation, etc.), packaging, shelf life, storage and distribution conditions and instructions for use.
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8.3.2.1 Dairy products Many dairy products are manufactured by traditional processes that have been practised for centuries. As a result of this, there is a great deal of background data and experience available to draw on. Furthermore, the majority of these traditional products have a good safety record, suggesting that standard manufacturing processes are safe. This situation can lead to complacency, and it is essential that the basis for the inherent safety of these products is fully understood. This is particularly true in situations where the introduction of new technology, new additives and ingredients, and new requirements from retailers and consumers may give rise to new hazards. 8.3.3
Identify intended use
The intended use should be based on the expected uses of the product by the enduser or consumer (e.g. is a cooking process required?). It is also important to identify the consumer target groups. Vulnerable groups of the population, such as children or the elderly, may need to be considered specifically. 8.3.3.1 Dairy products Dairy products are often consumed by high-risk groups, particularly the very young and the elderly. Infants are at particular risk from pathogens such as Salmonella, and pregnant women and the elderly are especially vulnerable to Listeria infection. This must be considered during the HACCP study and should be taken into account when compiling the instructions for use. 8.3.4
Construct a flow diagram
The flow diagram should be constructed by the HACCP team and should contain sufficient technical data for the study to progress. It should provide an accurate representation of all steps in the production process from raw materials to the endproduct. It may include details of the factory and equipment layout, ingredient specifications, features of equipment design, time/temperature data, cleaning and hygiene procedures and storage conditions. Ideally it should also include details of CCP steps, once determined. 8.3.4.1 Dairy products Examples of flow diagrams for specific dairy products may be found in the appropriate product chapters. Many dairy processing operations have relatively few steps and the flow diagrams appear simple. Common steps occur in many processes - for example, standardisation, pasteurisation, and homogenisation.
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However, it is essential that the details of each step are fully appreciated and recorded. Particular attention should be paid to potential routes of product flow that might allow cross-contamination between raw and pasteurised product. Divert valves, bypasses, pumps, and holding or balance tanks require close scrutiny. In modern dairy plants, it is also important to ascertain how cleaning-inplace systems are designed and operated. Effective cleaning is an essential control for preventing recontamination of pasteurised dairy products. 8.3.5
On-site confirmation of the flow diagram
The HACCP team should confirm that the flow diagram matches the process that is actually being carried out. The operation should be observed at all stages, and any discrepancies between the flow diagram and normal practice must be recorded and the diagram amended accordingly. It is also important to include observation of production outside normal working hours such as shift patterns and weekend working, as well as the circumstances of any reclaim or rework activity. It is essential that the diagram is accurate, because the hazard analysis and decisions regarding CCPs are based on these data. If HACCP studies are applied to proposed new process lines/ products, then any pre-drawn HACCP plans must be reviewed once the lines/products are finalised. 8.3.6 List all potential hazards associated with each step; conduct a hazard analysis; and identify any measures to control identified hazards The HACCP team should list all hazards that may reasonably be expected to occur at each step in the production process. The team should then conduct a hazard analysis to identify which hazards are of such a nature that their elimination or reduction to an acceptable level is essential to the production of safe food. The analysis is likely to include consideration of: •
The likely occurrence of hazards and the severity of their adverse health effects;
•
The qualitative and/or quantitative evaluation of the presence of hazards;
•
Survival or multiplication of pathogenic microorganisms;
•
Production or persistence of toxins;
•
The hurdle effect;
•
The number of consumers potentially exposed and their vulnerability;
•
Any food safety objectives or manufacturer’s food safety requirements.
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The HACCP team should then determine what control measures exist that can be applied for each hazard. Some hazards may require more than one control measure for adequate control and a single control measure may act to control more than one hazard. One control measure may be relevant to several process steps, where a hazard is repeated. Note: it is important at this stage that no attempt is made to identify CCPs, since this may interfere with the analysis. 8.3.6.1 Dairy products The term 'dairy products' includes a varied group of foods, and there is an equally varied range of potential hazards associated with them. Hazards specific to certain types of product are detailed in the appropriate chapters of this manual. For example, there are particular hazards associated with contamination of dried milk powders by salmonellae, and the potential growth of Listeria monocytogenes in soft cheeses. Many of the microbiological hazards associated with dairy products are derived from the raw materials (i.e. raw milk). Pathogens may be part of the resident microflora of the Iiving animal (e.g. Staphylococcus aureus), or may originate from faecal contamination during initial milk collection (e.g. Salmonella and E.coli 0157). Pathogens may also be introduced into raw milk from contaminated equipment during collection, transport, or storage. The majority of these hazards can be eliminated by an appropriate heat treatment, such as pasteurisation or sterilisation. Hazards introduced during processing of dairy products depend very much on the characteristics of the process. For example, heat-sensitive pathogens may be present in pasteurised milk as a result of cross-contamination between raw and heat-treated milk, and slow acid production by the starter culture in fermented milk products may allow growth and toxin production by Staph. aureus. Therefore, it is not possible, or desirable, to generalise about expected hazards, and the reader is referred to the appropriate product chapter in this book for additional advice on specific hazards. 8.3.7
Determine CCPs
The determination of CCPs in the HACCP system is facilitated by using a decision tree (Figure 8.2) to provide a logical, structured approach to decision making. However, application of the decision tree should be flexible, and its use may not always be appropriate. It is also essential that the HACCP team has access to sufficient technical data to determine the CCPs effectively. If a significant hazard has been identified at a step where control is required for safety, but for which no control exists at that step or any other, then the process must be modified to include a control measure.
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Answer the following questions for each identified hazard: Q1. Do control preventative measure(s) exist?
Yes
Modify step, process or product
No
Yes
Is control at this step necessary for safety?
No
Not a CCP
STOP*
Q2. Is the step specifically designed to eliminate or reduce the likely occurrence of a hazard to an acceptable level?
Yes
No
Q3. Could contamination with identified hazard(s) occur in excess of acceptable level(s) or could these increase to unacceptable level(s)?
Yes
No
Not a CCP
Q4. Will a subsequent step eliminate identified hazard(s) or reduce likely occurrence to an acceptable level?**
Yes
Not a CCP
STOP*
No
CRITICAL CONTROL POINT
STOP*
* Proceed to next step in the described process ** Acceptable and unacceptable levels need to be defined within the overall objectives in identifying the CCPs of HACCP plan
Fig. 8.2. CCP Decision Tree A (Adapted from Codex Alimentarius Commission, 1997)
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8.3.7.1 Dairy products Again, given the enormous variety of dairy products and processes in use, it is unwise to generalise on likely CCPs, and the reader is referred to the appropriate product chapter in this book. However, it can be said that effective control measures are likely to include the following: •
Careful control of raw milk quality and selection of sources for other raw materials;
•
Adequate pasteurisation processes;
•
Prevention of cross-contamination of pasteurised product;
•
Effective sanitation and hygiene procedures;
•
Adequate temperature control.
Some examples are as follows: In the manufacture of skimmed milk powder, CCPs are likely to be pasteurisation, and the effective separation, cleaning and maintenance of spray dryers and powder handling equipment. In the production of fermented milk products and cheese, pasteurisation is again likely to be a CCP, but the rapid development of sufficient acidity by the starter culture is also a CCP. Adequate temperature control during processing would normally be considered a CCP in the manufacture of ice cream, as would the microbiological quality of flavouring ingredients added after pasteurisation. 8.3.8
Establish critical limits for each CCP
Critical limits separate acceptable from unacceptable products. Where possible, critical limits should be specified and validated for each CCP. More than one critical limit may be defined for a single step. For example, it is necessary to specify both time and temperature for a thermal process, and a minimum process of 72 °C for 15 seconds, or equivalent, is required for milk pasteurisation. Criteria used to set critical limits must be measurable and may include physical, chemical, biological or sensory parameters. It is prudent to set stricter limits (often called target or process limits/levels) to ensure that any trends towards a loss of control is noted before the critical limit is exceeded.
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8.3.8.1 Dairy products Specific product chapters provide information on criteria that may be used to set critical limits. Some examples relevant to dairy products are: •
Pasteurisation time and temperature
•
Total acidity and/or pH (fermented products)
•
Measured adequacy of cleaning procedures
•
Chilled storage time and temperature
•
Water activity (condensed milk products)
8.3.9
Establish a monitoring system for each CCP
Monitoring involves planned measurement or observation of a CCP relative to its critical limits. Monitoring procedures must be able to detect loss of control of the CCP, and should provide this information with sufficient speed to allow adjustments to be made to the control of the process before the critical limits are violated. Monitoring at critical limits should be able to detect rapidly when the critical limit has been exceeded. Monitoring should either be continuous, or carried out sufficiently frequently to ensure control at the CCP. Therefore, physical and chemical on-line measurements are usually preferred to lengthy microbiological testing. However, certain rapid methods, such as ATP assay by bioluminescence, may be useful for assessment of adequate cleaning, which could be a critical limit for some CCPs, for example, pre-start-up hygiene. Persons engaged in monitoring activities must have sufficient knowledge, training and authority to act effectively on the basis of the data collected. These data should also be properly recorded. 8.3.10
Establish corrective actions
For each CCP in the HACCP plan, there must be specified corrective actions to be applied if the CCP is not under control. If monitoring indicates a deviation from the critical limit for a CCP, action must be taken that will bring it back under control. Actions taken should also include proper isolation of the affected product and an investigation into why the deviation occurred. A further set of corrective actions should relate to the target level, if process drift is occuring. In this case, only repair of the process defect and investigation of the fault are required. All corrective actions should be properly recorded.
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8.3.11
Establish verification procedures
Verification usually involves auditing and testing procedures. Auditing methods, procedures and tests should be used frequently enough to determine whether the HACCP system is being followed, and is effective at controlling the hazards. These may include random sampling and analysis, including microbiological testing. Although microbiological analysis is generally too slow for monitoring purposes, it can be of great value in verification, since many of the identified hazards are likely to be microbiological. For example, analysis of dried milk powders for Salmonella, desserts for Bacillus cereus, and soft cheeses for Listeria would be appropriate verification tests. In addition, reviews of HACCP records are important for verification purposes. These should confirm that CCPs are under control and should indicate the nature of any deviations and the actions that were taken in each case. It is also useful to review customer returns and complaints regularly. 8.3.12
Establish documentation and record keeping
Efficient and accurate record keeping is an essential element of a HACCP system. The procedures in the HACCP system should be documented. Examples of documented procedures include: •
The hazard analysis
•
Determination of CCPs
•
Determination of critical limits
•
The completed HACCP plan
Examples of recorded data include: •
Results of monitoring procedures
•
Deviations from critical limits and corrective actions
•
Records of certain verification activities, e.g. observations of monitoring activities, and calibration of equipment.
The degree of documentation required will depend partly on the size and complexity of the operation, but it is unlikely to be possible to demonstrate that an effective HACCP system is present without adequate documentation and records. The length of time that records are kept will be as per company policy, but should not be less than one year beyond the shelf life of the product. Three to five years is typical for many food companies.
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8.4
Implementation and Review of the HACCP Plan
The completed plan can only be implemented successfully with the full support and co-operation of management and the workforce. Adequate training is essential and the responsibilities and tasks of the operating personnel at each CCP must be clearly defined. Finally, it is essential that the HACCP plan be reviewed following any changes to the process, including changes to raw materials, processing conditions or equipment, packaging, cleaning procedures and any other factor that may have an effect on product safety. Even a small alteration to the product or process may invalidate the HACCP plan and introduce potential hazards. Therefore, the implications of any changes to the overall HACCP system must be fully considered and documented, and adjustments made to the procedures as necessary. Tiggered reviews/audits should occur as a result of changes, whereas scheduled review/audit should be annually, as a minimum. 8.5
References
Wareing, P.W., Carnell, A.C. HACCP – A Toolkit for Implementation. Leatherhead, Leatherhead Food International. 2007. Drosinos E.H., Siana P.S. HACCP in the cheese manufacturing process, a case study, in Food Safety: A Practical and Case Study Approach. Eds. McElhatton A., Marshall R.J. Berlin, Springer. 2007, 90-111. Bernard D., Scott. V. Hazard Analysis and Critical Control Point System: use in controlling microbiological hazards, in Food Microbiology: Fundamentals and Frontiers. Eds. Doyle M.P., Beuchat L.R. Washington DC, ASM Press. 2007, 97186. Rabi A., Banat A., Shaker R.R., Ibrahim S.A. Implementation of HACCP system to large scale processing line of plain set yogurt. Italian Food and Beverage Technology, 2004, (35), 12-17. Institute of Medicine, National Research Council. Scientific criteria and performance standards to control hazards in dairy products, in Scientific Criteria to Ensure Safe Food. Ed. Institute of Medicine, National Research Council. Washington D.C., National Academic Press. 2003, 225-47. Jervis D. Application of Process Control, in Dairy Microbiology Handbook: The Microbiology of Milk and Milk Products. Ed. Robinson R. New York, John Wiley and Sons, Inc. 2002, 593-654. Mortimore S., Mayes T. The effective implementation of HACCP systems in food processing, in Foodborne Pathogens: Hazards, Risk Analysis and Control. Eds. Blackburn C. de W., McClure P.J. Cambridge, Woodhead Publishing Ltd. 2002, 229-56. Ali A.A., Fischer R.M. Implementation of HACCP to bulk condensed milk production line. Food Reviews International, 2002, 18 (2-3), 177-90. 116
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HACCP Mayes T., Mortimore C.A. Making the most of HACCP: Learning from Other’s Experience. Cambridge, Woodhead Publishing. 2001. Mortimore S.E., Wallace C., Cassianos C. HACCP (Executive Briefing). London, Blackwell Science Ltd. 2001. Dairy Practices Council. Hazard Analysis Critical Control Point system - HACCP for the dairy industry. Guideline No. 55, in Guidelines for the Dairy Industry Relating to Sanitation and Milk Quality, Volume 4. Ed. Dairy Practices Council. Keyport, DPC. 2001. Sandrou D.K., Arvanitoyannis I.S. Application of Hazard Analysis Critical Control Point (HACCP) system to the cheese making industry: a review. Food Reviews International, 2000, 16 (3), 327-68. Sandrou D. K., Arvanitoyannis I.S. Implementation of Hazard Analysis Critical Control Point (HACCP) to the dairy industry: current status and perspectives. Food Reviews International, 2000, 16 (1), 77-111. Gould B.W., Smukowski M., Bishop J.R. HACCP and the dairy industry: an overview of international and US experiences, in The Economics of HACCP: Costs and Benefits. Ed. Unnevehr L.J. St Paul, Eagan Press. 2000, 365-84. Chartered Institute of Environmental Health. HACCP in Practice. London, Chadwick House Group Ltd. 2000. Jouve J.L. Good manufacturing practice, HACCP, and quality systems, in The Microbiological Safety and Quality of Food, Volume 2. Eds. Lund B.M., BairdParker T.C., Gould G.W. Gaithersburg, Aspen Publishers. 2000, 1627-55. Stevenson K.E., Bernard D.T. HACCP: A Systematic Approach to Food Safety. Washington DC, Food Processors Institute. 1999. Mavropoulos A.A., Arvanitoyannis I.S. Implementation of Hazard Analysis Critical Control Point to Feta and Manouri cheese production lines. Food Control, 1999, 10 (3), 213-9. Corlett D.A. HACCP User's Manual. Gaithersburg, Aspen Publishers. 1998. Mortimore S., Wallace C. HACCP: A Practical Approach. Gaithersburg, Aspen Publishers. 1998. Khandke S.S., Mayes T. HACCP implementation: a practical guide to the implementation of the HACCP plan. Food Control, 1998, 9 (2-3), 103-9. Forsythe S.J., Hayes P.R. Food Hygiene, Microbiology and HACCP. Gaithersburg. Aspen Publishers. 1998. Food and Agriculture Organisation. Food Quality and Safety Systems: A Training Manual on Food Hygiene and the Hazard Analysis and Critical Control Point (HACCP) system. Rome, FAO. 1998. National Advisory Committee on Microbiological Criteria for Foods. Hazard Analysis and Critical Control Point Principles and Application Guidelines. 1997. Gardner L.A. Testing to fulfil HACCP (Hazard Analysis Critical Control Points) requirements: principles and examples. Journal of Dairy Science, 1997, 80 (12), 3453-7. 117
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DAIRY PRODUCTS Codex Alimentarius Commission. Hazard Analysis Critical Control Point (HACCP) System and guidelines for its application, in Food Hygiene: Basic texts. Ed. Codex Alimentarius Commission. Rome, FAO. 1997, 33-45. Savage R.A. Hazard Analysis Critical Control Point: a review. Food Reviews International, 1995, 11 (4), 575-95. Peta C, Kailasapathy K. HACCP - its role in dairy factories and the tangible benefits gained through its implementation. Australian Journal of Dairy Technology, 1995, 50 (2), 74-8. Pierson M.D., Corlett D.A., Institute of Food Technologists. HACCP: Principles and Applications. New York, Van Nostrand Reinhold. 1992. Bryan F.L., World Health Organisation. Hazard Analysis Critical Control Point Evaluations: A Guide to Identifying Hazards and Assessing Risks Associated with Food Preparation and Storage. Geneva, WHO. 1992. Mayes T. Simple users' guide to the hazard analysis critical control point concept for the control of food microbiological safety. Food Control, 1992, 3 (1), 14-19. International Commission on Microbiological Specifications for Foods. Microorganisms in Foods, Volume 4: Application of the Hazard Analysis Critical Control Point (HACCP) System to Ensure Microbiological Safety and Quality. Oxford, Blackwell Scientific Publications. 1988.
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9. EU FOOD HYGIENE LEGISLATION
9.1
Introduction
Hygiene is an important aspect of ensuring food safety and one that plays an important role in most countries’ food legislation. Hygiene is a general concept that covers a wide subject area, from structural conditions in the factory or process facility, to personnel requirements, final product specifications, including microbiological criteria, transport and delivery vehicles requirements, and conditions of raw materials. Microbiological standards have a useful role and help establish requirements for the microbiological safety and quality of food and raw materials. A number of standards are provided in food legislation; however, the existence of microbiological standards cannot protect consumer health alone. It is generally considered that the principles of Good Manufacturing Practice (GMP) and application of Hazard Analysis Critical Control Point (HACCP) systems are of greater importance. A new package of EU hygiene measures became applicable on 1 January 2006 to update and consolidate the earlier 17 hygiene directives with the intention of introducing consistency and clarity throughout the food production chain from primary production to sale or supply to the final consumer. The general food hygiene Directive 93/43/EEC and other Directives on the hygiene of foodstuffs and the health conditions for the production and placing on the market of certain products of animal origin intended for human consumption have been replaced by several linked measures on food safety rules and associated animal health controls. The new legislation was designed to establish conditions under which food is produced to optimise public health and to prevent, eliminate or acceptably control pathogen contamination of food. Procedures under the new legislation are based on risk assessment and management and follow a 'farm to fork' approach to food safety with the inclusion of primary production in food hygiene legislation. Prescribed are detailed measures to ensure the safety and wholesomeness of food during preparation, processing, manufacturing, packaging, storing, transportation, distribution, handling and offering for sale or supply to the consumer.
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9.2
Legislative Structure
From 1 January 2006, the following EU hygiene regulations have applied: •
Regulation (EC) No. 852/2004 of the European Parliament and of the Council on the hygiene of foodstuffs
•
Regulation (EC) No. 853/2004 of the European Parliament and of the Council laying down specific hygiene rules for food of animal origin
•
Regulation (EC) No. 854/2004 of the European Parliament and of the Council laying down specific rules for the organisation of official controls on products of animal origin intended for human consumption
•
Regulation (EC) No. 2073/2005 on microbiological criteria for foodstuffs
The general hygiene requirements for all food business operators are laid down in Regulation 852/2004. Regulation 853/2004 supplements Regulation 852/2004 in that it lays down specific requirements for food businesses dealing with foods of animal origin. Regulation 854/2004 relates to the organisation of official controls on products of animal origin and sets out what those enforcing the provisions have to do. N.B. A number of more detailed implementing and transitional measures have been adopted at EC level. Subsequently, existing hygiene Directives including those below were repealed: •
Commission Directive 89/362/EEC of 26 May 1989 on general conditions of hygiene in milk production holdings OJ L 156, 8.6.1989, 30–2
•
Council Directive 92/46/EEC of 16 June 1992 laying down the health rules for the production and placing on the market of raw milk, heat-treated milk and milk-based products OJ L 268, 14.9.1992, 1–32
•
Council Directive 93/43/EEC of 14 June 1993 on the hygiene of foodstuffs OJ L 175, 19.7.1993, 1–11
The EU hygiene regulations apply to all stages of food production including primary production. As regulations, the legislation is directly applicable law and binding in its entirety on all member states from the date of entry into force. Although the regulations have the force of law, national legislation in the form of a Statutory Instrument (S.I.) in England, and equivalent legislation in Scotland, Wales and Northern Ireland, is required to give effect to the EU regulations, for example, setting offences, penalties and powers of entry, revocation of existing implementing legislation, etc.
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LEGISLATION
The Food Hygiene (England) Regulations 2006 (S.I. 2006 No.14, as amended) came into force on 11 January 2006 (separate but similar national legislation also came into force on that day in Scotland, Wales and Northern Ireland). The national legislation in all four UK countries also applied the provisions of the EU Microbiological Criteria Regulation No. 2073/2005. Although EU food hygiene regulations are directly applicable in the individual Member States there are some aspects where Member States are required or allowed to adopt certain provisions into their national laws. In England for example, there are temperature requirements for foods laid down in Schedule 4 of the Food Hygiene (England) Regulations 2006, as amended. Also, for England, there are restrictions on the sale of raw milk intended for human consumption as laid down by schedule 6 of the Food Hygiene (England) Regulations 2006, as amended. Both of these issues will be covered later in this chapter. 9.3
Regulation (EC) No. 852/2004 on the General Hygiene of Foodstuffs
Food business operators must ensure that all stages of production, processing and distribution of food under their control satisfy the relevant hygiene requirements laid down in Regulation (EC) No. 852/2004. This Regulation lays down general rules for food business operators on the hygiene of foodstuffs, particularly taking into account a number of factors ranging from ensuring food safety throughout the food chain to begin with primary production, right through to the implementation of procedures based on HACCP principles. There are some exemptions, for example, with primary production, domestic preparation or handling, food storage that is for private or domestic consumption, and also if the producer supplies small amounts of primary product to the final consumer or local retail establishments supplying the final consumer, since Regulation (EC) 852/2004 will not apply in these cases. Likewise Regulation 852/2004 will not apply to collection centres and tanneries meeting the definition of food business because they handle raw material for the production of gelatine or collagen. The regulation lays down general hygiene provisions for which food business operators carrying out primary production must comply with as laid down in Part A of Annex I. Additionally the requirements of EC regulation 853/2004 must be complied with which will be covered later in this chapter. 9.3.1
Annex I - Primary Production
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(c) for products of plant origin - transport operations to deliver primary products (which haven’t been substantially altered) from the place of production to an establishment Food business operators have the responsibility to ensure primary products are protected against contamination. Any community and national legislation relating to the control of hazards in primary production such as measures to control contamination resulting from surroundings, for example, air, soil, water etc. and measures relating to animal health and welfare, and plant health that may impact on human health should be complied with. Food business operators rearing, harvesting or hunting animals or producing primary products of animal origin are to take adequate measures as necessary. Therefore this relates to the cleaning and disinfection of equipment, and the storage and handling of waste. Requirements for record keeping are also laid down. This relates to animal feed (nature and origin), veterinary medicines administered to animals (date given and withdrawal periods), any diseases, analysis of samples from other animals which might impact on human health as well as reports on animal checks performed. 9.3.2
Annex II - Stages Other Than Primary Production
Annex II of the regulation lays down additional general hygiene requirements that must be met by food business operators carrying out production, processing and distribution of food following those stages above. A summary of Chapters I to IV of Annex II is provided in the following sections. 9.3.2.1 Chapter I Chapter I applies to all food premises, except premises to which Chapter III applies. - Food premises must be kept clean and maintained in good repair and condition. The layout should allow for this. - The environment should allow good hygiene practices and give temperature controlled handling and storage conditions where necessary, and to allow foods to be kept at correct temperatures and be monitored. - Additionally there are requirements for adequate lavatories, basins, ventilation, lighting and draining. 9.3.2.2 Chapter II Chapter II applies to all rooms where food is prepared, treated or processed, except dining areas and premises to which Chapter III applies. - The design and layout of rooms should allow for good hygiene practices between and during operations. Therefore floor and wall surfaces, ceilings and windows should be constructed to prevent dirt accumulating.
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- Surfaces where food is handled must be maintained well and allow easy cleaning and disinfection preferably using smooth, washable corrosion-resistant and non-toxic materials. - There should be facilities for cleaning or disinfecting, and for storing working utensils or equipment. Clean potable water and adequate provision for washing food is needed. 9.3.2.3 Chapter III Chapter III applies to temporary premises (e.g. marquees, market stalls, mobile sales vehicles), premises used primarily as a private dwelling-house but where foods are regularly prepared for placing on the market, and vending machines. - Here, premises and vending machines should practically be sited, designed, constructed and kept clean and maintained in good repair and condition so as to avoid the risk of contamination, in particular by animals and pests. - Facilities should allow adequate personal hygiene and surfaces in contact with food should be easy to clean. Enough potable water and storage arrangements for hazardous or inedible substances is required as well as adherence to food safety requirements. 9.3.2.4 Chapter IV Chapter IV applies to all transportation. - This lists requirements that conveyances and/or containers used for transporting foodstuffs are to be kept clean and maintained in good repair and condition to protect foodstuffs from contamination and are, where necessary, to be designed and constructed to permit adequate cleaning and/or disinfection. - Food should be maintained at appropriate temperatures. 9.3.2.5 Chapter V Chapter V refers to equipment requirements. - Adequate cleaning and disinfection is to be done frequently for articles, fittings and equipment contacting food where contamination needs to be avoided. - Equipment should be installed to allow adequate cleaning, and be fitted with the required control device. 9.3.2.6 Chapter VI Chapter VI refers to food waste. - Food waste, non-edible by-products and other refuse is to be removed from rooms where food is present as quickly as possible to avoid accumulation. Such waste is to be deposited in closable containers, to allow easy cleaning.
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- Refuse stores should allow easy cleaning and be free of pests. - Waste must be eliminated hygienically in accordance with community legislation. 9.3.2.7 Chapter VII Chapter VII refers to water supply. - There are requirements that there should be an adequate supply of potable water, requirements for recycled water, ice contacting food, steam used and for the water used in the cooling process for heat treated foods in hermetically sealed containers. 9.3.2.8 Chapter VIII Chapter VIII is about personal hygiene required by those working in a food handling area including clean protective clothing and that those carrying or suffering from a disease are not permitted to handle food. 9.3.2.9 Chapter IX Chapter IX covers provisions applicable to foodstuffs. - A food business operator should not accept raw materials or ingredients, other than live animals, or any other material used in processing products, if they are known to be contaminated with parasites, pathogenic microorganisms or foreign substances. Neither should they accept raw materials or ingredients that are toxic or decomposed to such an extent that, even after the business operator applied normal processing hygienically, the product would be inedible. - Raw materials must be kept under appropriate conditions throughout production, processing and distribution. In particular, temperature control (i.e. cold chain and food thawing) requirements are laid down. 9.3.2.10 Chapter X Chapter X lays down provisions applicable to the wrapping and packaging of foodstuffs to avoid contamination of any form. 9.3.2.11 Chapter XI Chapter XI lays down heat treatment requirements for food that is placed on the market in hermetically sealed containers. - The process used should comply with internationally recognised standards (i.e. pasteurisation, Ultra High Treatment or sterilisation)
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9.3.2.12 Chapter XII Chapter XII states training requirements for food business operators to ensure that food handlers are trained in food hygiene matters and in the application of HACCP principles. 9.3.3
Registration
The regulation requires that food business operators must notify their competent authority of their establishment and have it registered. Food business operators must also ensure that the competent authority always has up-to-date information on establishments, including the notification of significant changes in activity and closure of an existing establishment. Food business operators must ensure that establishments are approved by the competent authority, following at least one on-site visit, when approval is required by the national law of the Member State, or under Regulation (EC) No. 853/2004, or by a separate decision adopted. Separate rules apply for businesses producing products of animal origin. 9.3.4
HACCP
Food business operators, other than at the level of primary production, and associated operations must put in place, implement and maintain a permanent procedure or procedures based on principles of the system of hazard analysis and critical control points (HACCP). Emphasis is placed on risk-related control, with responsibility placed on the proprietor of the food business to ensure that potential hazards are identified and systems are developed to control them. Under HACCP, food business operators must, amongst others, identify hazards to be prevented, eliminated or reduced to acceptable levels, identify and establish critical control points (CCP) to prevent, eliminate or reduce hazards to allow this to be monitored, and establish corrective actions in the case where a CCP is out of control. Procedures must be taken to confirm the above is in place and up-to-date, as well as provide documents and records as evidence for the competent authority. 9.4 Regulation (EC) No. 853/2004 Laying Down Specific Hygiene Rules for Food of Animal Origin Regulation (EC) No. 853/2004 lays down hygiene rules for products of animal origin which apply in addition to the general hygiene rules of Regulation (EC) No. 852/2004.
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9.4.1
Definitions
Dairy products are processed products resulting from the processing of raw milk or from the further processing of such processed products. Raw milk is milk produced by the secretion of the mammary gland of farmed animals that has not been heated to more than 40 °C or undergone any treatment that has an equivalent effect. Milk production holding means an establishment where one or more farm animals are kept to produce milk with a view to placing it on the market as food. Colostrum is the fluid secreted by the mammary glands of milk-producing animals up to three to five days post parturition, that is rich in antibodies and minerals and precedes the production of raw milk Colostrum-based products are processed products resulting from the processing of colostrum or from the further processing of such processed products. 9.4.2
Requirements
The regulation details specific hygiene requirements for raw milk, colostrum, dairy products and colostrum-based products. Extracts of the requirements of regulation 853/2004, as amended, specifically relating to milk and milk products are given below; for full requirements, reference should be made to the actual regulation. Food business operators producing or, as appropriate, collecting raw milk and colostrum must ensure compliance with the requirements laid down in Annex III, Section IX as follows: 9.4.2.1 Chapter I: Raw Milk – Primary Production 9.4.2.1.1 Health requirements for raw milk and colostrum production Raw milk and colostrum must come from animals free from any symptoms of infectious diseases that can be transferred to humans though milk and colostrum. Therefore such milk and colostrum needs to come from: (i) cows or buffaloes belonging to a herd which, within the meaning of Directive 64/432/EEC, is free or officially free of brucellosis; (ii) sheep or goats belonging to a holding free or officially free of brucellosis within the meaning of Directive 91/68/EEC; or (iii) females of other species, for species susceptible to brucellosis, belonging to herds regularly checked for that disease under a control plan that the competent authority has approved.
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Likewise, the same conditions apply in relation to tuberculosis. There are cases whereby raw milk from animals that do not meet the requirements of the above may be used with the authorisation of the competent authority such as: (a) in the case of cows or buffaloes that do not show a positive reaction to tests for tuberculosis or brucellosis, nor any symptoms of these diseases, after having undergone a heat treatment such as to show a negative reaction to the alkaline phosphatase test; (b) in the case of sheep or goats that do not show a positive reaction to tests for brucellosis, or which have been vaccinated against brucellosis as part of an approved eradication programme, and which do not show any symptom of that disease, either: (i) for the manufacture of cheese with a maturation period of at least two months; or (ii) after having undergone heat treatment such as to show a negative reaction to the alkaline phosphatase test; and (c) in the case of females of other species that do not show a positive reaction to tests for tuberculosis or brucellosis, nor any symptoms of these diseases, but belong to a herd where brucellosis or tuberculosis has been detected after the following, checks provided it is treated to ensure its safety: - females of other species belonging, for species susceptible to brucellosis, to herds regularly checked for that disease under a control plan that the competent authority has approved. - females of other species belonging, for species susceptible to tuberculosis, to herds regularly checked for this disease under a control plan that the competent authority has approved. 9.4.2.1.2 Hygiene on milk and colostrum production holdings A. Requirements for premises and equipment This relates to milking equipment and premises where milk and colostrum is stored etc. which must be constructed in a way that limits any risk of contamination. Surfaces of equipment in contact with milk and colostrum are to be adequately cleaned and disinfected where necessary after use. B. Hygiene during milking, collection and transport 1. It states that milking needs to be carried out hygienically, ensuring that before milking starts, the teats, udder and adjacent parts are cleaned. The animal is to be checked for any abnormalities and those showing clinical signs of udder
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disease should not be used. Also, colostrum should be milked separately and not mixed together with raw milk. 2.
Immediately after milking, milk and colostrum must be held in a clean place designed and equipped to avoid contamination. The requirements are that: (a) Milk must be cooled immediately to not more than 8 °C (if a daily collection), or not more than 6 °C (if collection is not daily). (b) Colostrum must be stored separately and immediately cooled to not more than 8 °C (if a daily collection), not more than 6 °C (if collection is not daily), or frozen.
3.
During transport the cold chain must be maintained and, on arrival at the establishment of destination, the temperature of the milk and the colostrum must not be more than 10 °C.
4.
Food business operators need not comply with the temperature requirements laid down in points 2 and 3 if the milk meets the criteria provided for in Part III and either: (a) the milk is processed within two hours of milking; or (b) a higher temperature is necessary for technological reasons concerning the manufacture of certain dairy products and the competent authority so authorises.
C. Staff hygiene Those milking and/or handling raw milk and colostrum must wear suitable clean clothes. Additionally, those performing milking must maintain a high degree of personal cleanliness. 9.4.2.1.3 Criteria for raw milk Criteria for raw milk has been made pending the establishment of standards in the context of more specific legislation on the quality of milk and dairy products. National criteria for colostrum, as regards plate count, somatic cell count or antibiotic residues, apply pending the establishment of specific Community legislation. A representative number of samples of raw milk and colostrum collected from milk production holdings taken by random sampling must be checked for compliance with the following in the case of raw milk and with the existing national criteria referred to for colostrums. (i) Raw cows' milk must meet the following standards: Plate count 30 °C (per ml) < or = 100,0001 Somatic cell count (per ml) < or = 400,0002
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(ii)
Raw milk from other species Plate count 30 °C (per ml)
< or = 1,500,0001
1 Rolling geometric average over a two-month period, with at least two samples per month. However, if raw milk from species other than cows is used for manufacture of products made with raw milk by a process that doesn’t involve any heat treatment, food business operators should aim to ensure the raw milk meets the following criterion: Plate count 30 °C (per ml) < or = 500,0001 1 Rolling geometric average over a two-month period, with at least two samples per month. Without prejudice to Directive 96/23/EC, food business operators may not place raw milk on the market if it contains antibiotic residues in a quantity that, in respect of any one of the substances referred to in Annexes I and III to Regulation (EEC) No. 2377/90, exceeds the levels authorised under that Regulation or, if the combined total of residues of antibiotic substances exceeds any maximum permitted value. Raw milk not complying with the above should be notified to the competent authority and action taken to correct the situation. The checks for compliance may be carried out by, or on behalf of: (a) the food business operator producing the milk;
(b) the food business operator collecting or processing the milk; (c) a group of food business operators; or (d) in the context of a national or regional control scheme. 9.4.2.2 Chapter II: Requirements Concerning Dairy and Colostrum Products 9.4.2.2.1 Temperature requirements Food business operators are to ensure that upon acceptance at a processing establishment: (a) milk is quickly cooled to not more than 6 °C (b) colostrum is quickly cooled to not more than 6°C or maintained frozen and kept at that temperature until processed. 129
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Note: Food business operators may keep milk and colostrum at a higher temperature if processing begins immediately after milking, within four hours of acceptance at the processing establishment, or if the competent authority authorises a higher temperature for technological reasons concerning the manufacture of certain dairy or colostrum-based products. 9.4.2.2.2 Requirements for heat treatment 1.When raw milk, colostrum, colostrum-based or dairy products undergo heat treatment, food business operators must ensure that this satisfies the requirements of Regulation (EC) No. 852/2004, Annex II, Chapter XI. In particular, when using the following processes, they should comply with the specifications mentioned: (a) Pasteurisation is achieved by a treatment involving: (i) a high temperature for a short time (at least 72 °C for 15 seconds); (ii) a low temperature for a long time (at least 63 °C for 30 minutes); or (iii) any other combination of time-temperature conditions to obtain an equivalent effect. The result is a product that should show, where applicable, a negative reaction to an alkaline phosphatase test immediately after such treatment. (b) Ultra high temperature (UHT) treatment is achieved by a treatment: (i) involving a continuous flow of heat at a high temperature for a short time (not less than 135 °C in combination with a suitable holding time), such that there are no viable microorganisms or spores capable of growing in the treated product when kept in an aseptic closed container at ambient temperature; and (ii) sufficient to ensure that the products remain microbiologically stable after incubating for 15 days at 30 °C or for 7 days at 55 °C in closed containers, or after any other method demonstrating that the appropriate heat treatment has been applied. 2. In deciding whether to subject raw milk and colostrum to heat treatment, food business operators must consider procedures developed in accordance with the HACCP principles in Regulation (EC) No. 854/2004 and comply with any requirements that the competent authority may impose in this regard when approving establishments or carrying out checks following Regulation (EC) No. 854/2004. 9.4.2.2.3 Criteria for raw cows' milk 1. Food business operators manufacturing dairy products must initiate procedures to ensure that immediately before being heat treated and if its period of acceptance specified in the HACCP-based procedures is exceeded: 130
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(a) raw cows’ milk used to prepare dairy products has a plate count of less than 300,000 per ml at 30 °C; and (b) heat treated cows’ milk used to prepare dairy products has a plate count at 30 °C of less than 100,000 per ml. Any raw milk not complying with the above should be notified to the competent authority and action taken to correct the situation. 9.4.2.3 Chapter III: Wrapping and packaging Consumer packages must be sealed immediately after filling in the establishment where the last heat treatment of liquid dairy products and colostrum-based products takes place using sealing devices which prevent contamination. The sealing system must be designed so that after opening, evidence of its opening remains clear and is easy to check. 9.4.2.4 Chapter IV: Labelling 1. Firstly the requirements of Directive 2000/13/EC should be met, except in the cases envisaged in Article 13(4) and (5) of that Directive. Labelling must clearly show in the case of: (a) raw milk for direct human consumption, the words 'raw milk'; (b) products made with raw milk, the manufacturing process for which does not include any heat treatment or any physical or chemical treatment, the words 'made with raw milk'; (c) colostrum, the word 'colostrum'; (d) products made with colostrum, the words 'made with colostrum'. 2. The requirements of point 1 apply to products destined for retail trade. 'Labelling' includes any packaging, document, notice, label, ring or collar accompanying or referring to such products. 9.4.2.5 Chapter V: Identification marking By way of derogation from the requirements of Annex II, Section I: 1. rather than indicating the approval number of the establishment, the identification mark may include a reference to where on the wrapping or packaging the approval number of the establishment is indicated; 2. in the case of the reusable bottles, the identification mark may indicate only the initials of the consigning country and the approval number of the establishment. Note: Annex II, Section I lays down requirements for the application of the identification mark to include that it must be applied before the product leaves the establishment and if a product's packaging and/or wrapping is removed or it is 131
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further processed in another establishment, a new mark must be applied to the product. Here, the new mark must indicate the approval number of the establishment where these operations take place. The form of the identification mark is also specified to include the country code for where the establishment is located, for example, UK. 9.5 Regulation (EC) No. 854/2004 of the European Parliament and of the Council Laying Down Specific Rules for the Organisation of Official Controls on Products of Animal Origin Intended for Human Consumption Regulation (EC) 854/2004 gives requirements for official controls on products of animal origin and states requirements for those enforcing the provisions. In this regulation, general principles for official controls in respect of all products of animal origin falling within the scope of the regulation are given. It is a requirement that food business operators give assistance to ensure that official controls carried out by the competent authority can be done properly. The official controls include audits of good hygiene practices and hazard analysis and critical control point (HACCP)-based procedures. Raw milk and dairy products need to comply with the requirements of Annex IV of the regulation. This refers to the control of milk and colostrums production holdings, and to the control of raw milk and colostrums upon collection to ensure that hygiene requirements are being complied with. 9.6 Regulation (EC) No. 2073/2005 on Microbiological Criteria for Foodstuffs Regulation (EC) No. 2073/2005 which has applied since 1 January 2006 establishes microbiological criteria for a range of foods. The aim of this legislation is to complement food hygiene requirements, ensuring that foods being placed on the market do not pose a risk to human health, and it applies to all businesses involved in food production and handling. The definition of ‘microbiological criterion’ means a criterion defining the acceptability of a product, a batch of foodstuffs or a process, based on the absence, presence or number of microorganisms, and/or on the quantity of their toxins or metabolites, per unit(s) of mass, volume, area or batch. Two kinds of criteria have been established: food safety criteria, applying to products placed on the market, and process hygiene criteria that are applied during the manufacturing process. 9.6.1
Food safety criteria
Chapter 1 of the regulation focuses on food safety criteria which covers foods such as ready to eat foods intended for infants and for special medical purposes, and for milk powder and whey powder. The relevant criteria are as follows: 132
Listeria monocytogenes Salmonella Salmonella Salmonella Staphylococcal enterotoxins
Salmonella Salmonella Enterobacter sakazakii*
1.3 Ready-to-eat foods unable to support the growth of L. monocytogenes other than those intended for special medical purposes4,8
1.11 Cheeses, butter and cream made from raw milk or milk that has undergone a lower heat treatment than pasteurisation10
1.12 Milk powder and whey powder
133
1.13 Ice cream11, excluding products where the manufacturing process or composition of the product will eliminate the salmonella risk
1.21 Cheeses, milk powder and whey powder, as referred to in the coagulase-positive staphylococci criteria in Chapter 2.2 of this Annex
1.22 Dried infant formulae and dried dietary foods for specific medical purposes intended for infants below six months of age
1.23 Dried follow-on formulae
1.24 Dried infant formulae and dried dietary foods for specific medical purposes intended for infants below six months of age14
30
0
0
Absence in 10 g
Absence in 25 g
Absence in 25 g
Not detected in 25 g
Absence in 25 g
Absence in 25 g
Absence in 25 g
100 cfu/g5
Products placed on the market during their shelf-life
Products placed on the market during their shelf-life
Products placed on the market during their shelf-life
Products placed on the market during their shelf-life
Before the food has left the immediate control of the food business operator who has produced it
Products placed on the market during their shelf-life
Products placed on the market during their shelf-life
Stage where the criterion applies
ISO/TS 22964
EN/ISO 6579
Absence in 25 g
Products placed on the market during their shelf-life
Products placed on the market during their shelf-life
Products placed on the market during their shelf-life
European screening Products placed on the market method of the CRL during their shelf-life for coagulase-positive staphylococci13
EN/ISO 6579
EN/ISO 6579
EN/ISO 6579
EN/ISO 11290-26
EN/ISO 11290-1
EN/ISO 11290-26
EN/ISO 11290-1
Analytical reference method3
13:54
30
0
0
0
0
0
0
Absence in 25 g7
100 cfu/g5
m M Absence in 25 g
Limit2
30/01/2009
30
5
5
5
5
5
0
5
1.2 Ready-to-eat foods able to support the growth of L. monocytogenes, other than those intended for special medical purposes
0
Listeria monocytogenes
1.1 Ready-to-eat foods intended for infants and ready-to-eat foods for special medical purposes4 5
Microorganisms Sampling plan1 n c Listeria 10 0 monocytogenes
Food Category
TABLE 9.I Food Safety Criteria
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DAIRY PRODUCTS 1 n = number of units comprising the sample; c = number of sample units giving values between m and M 2 For points 1.1-1.25 m = M. 3 The most recent edition of the standard shall be used. 4 Regular testing against the criterion is not required in normal circumstances for the following ready-to-eat foods: - those which have received heat treatment or other processing effective to eliminate L. monocytogenes, when recontamination is not possible after this treatment (for example, products heat treated in their final package) - fresh, uncut and unprocessed vegetables and fruits, excluding sprouted seeds - bread, biscuits and similar products - bottled or packed waters, soft drinks, beer, cider, wine, spirits and similar products - sugar, honey and confectionery, including cocoa and chocolate products - live bivalve molluscs 5 This criterion shall apply if the manufacturer is able to demonstrate, to the satisfaction of the competent authority, that the product will not exceed the limit 100 cfu/g throughout the shelf-life. The operator may fix intermediate limits during the process that must be low enough to guarantee that the limit of 100 cfu/g is not exceeded at the end of shelf-life. 6 1 ml of inoculum is plated on a Petri dish of 140 mm diameter or on three Petri dishes of 90 mm diameter. 7 This criterion shall apply to products before they have left the immediate control of the producing food business operator, when he is not able to demonstrate, to the satisfaction of the competent authority, that the product will not exceed the limit of 100 cfu/g throughout the shelf-life. 8 Products with pH ≤ 4.4 or a ≤ 0.92, products with pH ≤ 5.0 and a ≤ 0.94, w w
products with a shelf-life of less than five days shall be automatically considered to belong to this category. Other categories of products can also belong to this category, subject to scientific justification. 10 Excluding products when the manufacturer can demonstrate to the satisfaction of the competent authorities that, due to the ripening time and aw of the product where appropriate, there is no Salmonella risk. 11 Only ice creams containing milk ingredients. 13 Reference: Community reference laboratory for coagulase-positive staphylococci. European screening method for the detection of Staphylococcal enterotoxins in milk and milk products. 14 Parallel testing for Enterobacteriaceae and E. sakazakii shall be conducted, unless a correlation between these microorganisms has been established at an individual plant level. If Enterobacteriaceae are detected in any of the product samples tested in such a plant, the batch must be tested for E. sakazakii. It shall be the responsibility of the manufacturer to demonstrate to the satisfaction of the competent authority whether such a correlation exists between Enterobacteriaceae and E. sakazakii.
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*C. sakazakii is still refered to as E. sakazakii in legislation despite the name change in 2008. Interpretation of the test results relating to Table 9.I The limits given refer to each sample unit tested. The test results demonstrate the microbiological quality of the batch tested. They may also be used for demonstrating the effectiveness of the hazard analysis and critical control point principles or good hygiene procedure of the process. L. monocytogenes in ready-to-eat foods intended for infants and for special medical purposes: - satisfactory, if all the values observed indicate the absence of the bacterium, - unsatisfactory, if the presence of the bacterium is detected in any of the sample units. L. monocytogenes in ready-to-eat foods able to support the growth of L. monocytogenes before the food has left the immediate control of the producing food business operator when he is not able to demonstrate that the product will not exceed the limit of 100 cfu/g throughout the shelf-life: - satisfactory, if all the values observed indicate the absence of the bacterium, - unsatisfactory, if the presence of the bacterium is detected in any of the sample units. L. monocytogenes in other ready-to-eat foods: - satisfactory, if all the values observed are ≤ the limit, - unsatisfactory, if any of the values are > the limit. Salmonella in different food categories: - satisfactory, if all the values observed indicate the absence of the bacterium, - unsatisfactory, if the presence of the bacterium is detected in any of the sample units. Staphylococcal enterotoxins in dairy products: - satisfactory, if in all the sample units the enterotoxins are not detected, - unsatisfactory, if the enterotoxins are detected in any of the sample units. Enterobacter sakazakii in dried infant formulae and dried dietary foods for special medical purposes intended for infants below 6 months of age: - satisfactory, if all the values observed indicate the absence of the bacterium, - unsatisfactory, if the presence of the bacterium is detected in any of the sample units. 135
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9.6.2
Process hygiene criteria
Chapter 2 focuses on process hygiene criteria, with chapter 2.2 referring to milk and dairy products. Food categories covered range from pasteurised milk to ice cream and frozen dairy desserts. The criteria are outlined in Table 9.II overleaf. Interpretation of the test results relating to Table 9.II The limits given refer to each sample unit tested. The test results demonstrate the microbiological quality of the process tested. Enterobacteriaceae in dried infant formulae, dried dietary foods for special medical purposes intended for infants below six months of age and dried follow-on formulae: - satisfactory, if all the values observed indicate the absence of the bacterium, - unsatisfactory, if the presence of the bacterium is detected in any of the sample units. E. coli, Enterobacteriaceae (other food categories) and coagulase-positive staphylococci: - satisfactory, if all the values observed are ≤ m, - acceptable, if a maximum of c/n values are between m and M, and the rest of the values observed are ≤ m, - unsatisfactory, if one or more of the values observed are > M or more than c/n values are between m and M. Presumptive Bacillus cereus in dried infant formulae and dried dietary foods for special medical purposes intended for infants below six months of age: - satisfactory, if all the values observed are ≤ m, - acceptable, if a maximum of c/n values are between m and M, and the rest of the values observed are ≤ m, - unsatisfactory, if one or more of the values observed are > M or more than c/n values are between m and M.
136
137
Coagulasepositive staphylococci
Coagulasepositive staphylococci
2.2.4 Cheeses made from raw milk that has undergone a lower heat treatment than pasteurisation7 and ripened cheeses made from milk or whey that has undergone pasteurisation or a stonger heat treatment
5
5
5
E-coli5
2.2.2 Cheeses made from milk or whey that has undergone heat treatment
2.2.3 Cheeses made from raw milk
5
Enterobacteriaceae
2.2.1 Pasteurised milk and other pasteurised liquid dairy products4
2
2
2
2
Microorganisms Sampling plan1 n c
Food Category
100 cfu/g
104 cfu/g
100 cfu/g
105 cfu/g are detected, the cheese batch has to be tested for staphylococcal enterotoxins
Improvements in production hygiene and selection of raw materials
Check on the efficiency of heat treatment and prevention of recontamination, as well as the quality of raw materials
Action in case of unsatisfactory results
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LEGISLATION
138 5
2
2
100 cfu/g
100 cfu/g
10 cfu/g
10 cfu/g
100 cfu/g
100 cfu/g
10 cfu/g
10 cfu/g
10 cfu/g
M
ISO 21528-2
EN/ISO 6888-1 or 2
ISO 21528-2
ISO 16649-1 or 2
EN/ISO 6888-1 or 2
Analytical reference method3
End of the manufacturing process
End of the manufacturing process
End of the manufacturing process
End of the manufacturing process
End of the manufacturing process
Stage where the criterion applies
Improvements in production hygiene
Improvements in production hygiene. If values >105 cfu/g are detected, the batch has to be tested for staphylococcal enterotoxins
Check on efficiency of heat treatment and prevention of recontamination
Improvements in production hygiene and selection of raw materials
Improvements in production hygiene. If values >105 cfu/g are detected, the cheese batch has to be tested for staphylococcal enterotoxins
Action in case of unsatisfactory results
13:54
Enterobacteriaceae
5
Coagulasepositive staphylococci
0
2
2
m
Limit2
30/01/2009
2.2.8 Ice cream and8 frozen dairy desserts
5
Enterobacteriaceae
5
2.2.6 Butter and cream E. coli5 made from raw milk or milk that has undergone a lower heat treatment than pasteurisation
2.2.7 Milk powder and whey powder4
5
Microorganisms Sampling plan1 n c
2.2.5 Unripened soft Coagulasecheeses (fresh cheeses) positive made from milk or staphylococci whey that has undergone pasteurisation or a stronger heat treatment7
Food Category
TABLE 9.II cont. Process Hygiene Criteria
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2.2.11 Dried infant fomulae and dried dietary foods for special medical purposes intended for infants below six months of age
2.2.10 Dried followon fomulae
fomulae and dried dietary foods for special medical purposes intended for infants below six months of age
Food Category
Presumptive Bacillus cereus
Enterobacteriaceae
Enterobacteriaceae
5
5
10
1
0
0
Microorganisms Sampling plan1 n c M
500 cfu/g
Absence in 10 g
Absence in 10 g
50 cfu/g
m
Limit2
EN/ISO 793210
ISO 21528-1
ISO 21528-1
Analytical reference method3
TABLE 9.II cont. Process Hygiene Criteria
End of the manufacturing process
End of the manucfacturing process
End of the manufacturing process
Stage where the criterion applies
139
Improvements in production hygiene. Prevention of recontamination. Selection of raw material
Improvements in production hygiene to minimise contamination
Improvements in production hygiene to minimise contamination9
Action in case of unsatisfactory results
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DAIRY PRODUCTS 1 n = number of units comprising the sample; c = number of sample units giving values between m and M 2 For these criteria 2.2.7, 2.2.9 and 2.2.10 m=M 3 The most recent edition of the standard shall be used. 4 The criterion does not apply to milk destined for further processing in food industry. 5 E. coli is used here as an indicator for the level of hygiene. 6 For cheeses which are not able to support the growth of E. coli, the E. coli count is usually the highest at the beginning of the ripening period, and for cheeses which are able to support the growth of E. coli, it is normally at the end of the ripening period. 7 Excluding cheeses where the manufacturer can demonstrate, to the satisfaction of the competent authorities, that the product does not pose a risk of staphylococcal enterotoxins. 8 Only ice creams containing milk ingredients. 9 Parallel testing for Enterobacteriaceae and E. sakazakii shall be conducted, unless a correlation between these micro-organisms has been established at an individual plant level. If Enterobacteriaceae are detected in any of the product samples tested in such a plant, the batch has to be tested for E. sakazakii. It shall be the responsibility of the manufacturer to demonstrate to the satisfaction of the competent authority whether such a correlation exists between Enterobacteriaceae and E. sakazakii. 10 1 ml of inoculum is plated on a Petri dish of 140 mm diameter or on three Petri dishes of 90 mm diameter.
9.7 Food Hygiene (England) Regulations 2006, S.I. 2006 No. 14 (Hygiene requirements specific to the UK) 9.7.1
Sale of raw milk intended for direct human consumption
Regulation 32 of the Food Hygiene (England) Regulations 2006, S.I. 2006 No. 14, requires that Schedule 6 concerning restrictions on the sale of raw milk intended for direct human consumption shall have effect. The provisions of this Schedule are as follows: 1. It is an offence to sell raw milk intended for direct human consumption if it does not comply with the following standards: Plate count at 30 °C (cfu per ml) Coliforms (cfu per ml)
< or = 20,000 < 100
2. Only the occupier of a production holding or a distributor in compliance with the stated requirements may sell raw cows’ milk intended direct for human consumption. 3. The occupier of a production holding may only sell raw cows’ milk intended direct for human consumption: 140
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a)
at or from the farm premises where the animals from which the milk has been derived are maintained; and
b) to: (i) the final consumer for consumption other than at those farm premises; (ii) a temporary guest or visitor to those farm premises as or part of a meal or refreshment; or (iii) a distributor. 4. A distributor may only sell raw cows’ milk intended direct for human consumption: a) which he has bought as in point 3 above; b) in the containers in which he receives the milk, with the container fastenings unbroken; c)
from a vehicle lawfully used as a shop premises;
d) direct to the final consumer. 5. Where the farm premises are being used for the sale of raw cows’ milk intended for direct human consumption, the Food Standards Agency shall carry out such sampling, analysis and examination of the milk as it considers necessary to ensure it meets the required standards. A stated fee applies. 9.7.2
Temperature control requirements
In the UK, Schedule 4 of the Food Hygiene (England) Regulations 2006, S.I. 2006 No. 14 details temperature control requirements for foods in general. The regulations prescribe a chilled food holding temperature of 8 °C or less, but there is also a general requirement that foods must not be kept at temperatures that would result in a risk to health, and particularly that perishable foodstuffs must not be kept at above the maximum recommended storage temperature, which overrides the 8 °C requirement. Hot-held foods (food having been cooked or reheated that is for service or on display for sale) must not be kept below 63 °C. The regulations provide for defences in relation to upward variations of the 8 °C temperature, tolerance periods for chill-holding of foods and hot-holding variations. The defendant may be required to produce well-founded scientific proof to support his claims. For example, with chill-holding tolerance periods, the defendant will need to prove that the food was on service or display, had not been previously put on display at more than 8 °C and had been kept there for less than four hours. Alternatively, it would need to be proved that the food was being transferred to or from a vehicle used for the activities of a food business, to or from premises (including vehicles) at which the food was to be kept at or below 8°C or the recommended temperature, or, was kept at above 8°C or the recommended temperature for an unavoidable reason, such as that below, and was
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kept at above 8 °C or the recommended temperature for a limited period consistent with food safety. The permitted reasons are given below: to facilitate handling during and after processing or preparation the defrosting of equipment, or temporary breakdown of equipment For Scotland, there are separate provisions to include requirements to hold food under refrigeration or in a cool ventilated place, or at a temperature above 63 °C and to reheat food to a temperature of at least 82 °C (The Food Hygiene (Scotland) Regulations 2006, S.S.I. 2006 No. 3). Schedule 4 of the Food Hygiene (England) Regulations 2006 contains several definitions, including: Shelf-life: where the minimum durability or 'use by' indication is required according to Regulation 20 or 21 of the Food Labelling Regulations 1996 (form of indication of minimum durability and form of indication of ‘use-by date’), the period up to and including that date. For other food, the period for which it can be expected to remain fit for sale when kept in a manner consistent with food safety. Recommended temperature: a specified temperature that has been recommended in accordance with a food business responsible for manufacturing, preparing or processing the food recommending that it be kept at or below a specified temperature between 8 ºC and ambient temperatures. It should be noted that the temperature control requirements as detailed in Schedule 4 of the Food Hygiene (England) Regulations 2006 (S.I. 2006 No. 14) do not apply to any food covered by EU Regulation 853/2004 on hygiene of products of animal origin or any food business operation carried out on a ship or aircraft. 9.8
Guidance
In the U.K, the Food Standards Agency has published guidance notes on the requirements of the EU hygiene and microbiological criteria regulations which can, at the time of going to press, be accessed at the following link: http://www.food.gov.uk/foodindustry/guidancenotes/hygguid/fhlguidance/ 9.9
References
1. Regulation (EC) No. 852/2004 of the European Parliament and of the Council on the hygiene of foodstuffs (OJ No. L139, 30.4.2004, 1). The revised text of Regulation (EC) No. 852/2004 is now set out in a Corrigendum (OJ No. L226, 25.6.2004, 3) as amended by Regulation 1019/2008 and as read with Regulation 2073/2005.
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LEGISLATION 2. Regulation (EC) No. 853/2004 of the European Parliament and of the Council laying down specific hygiene rules for food of animal origin (OJ No. L139, 30.4.2004, p.55). The revised text of Regulation (EC) No. 853/2004 is now set out in a Corrigendum (OJ No. L226, 25.6.2004, p.22) as amended by Regulation 2074/2005, Regulation 2076/2005, Regulation 1662/2006, Regulation 1791/2006 and Regulation 1020/2008 and as read with Directive 2004/41, Regulation 1688/2005, Regulation 2074/2005 and Regulation 2076/2005. 3. Regulation (EC) No. 854/2004 of the European Parliament and of the Council laying down specific rules for the organisation of official controls on products of animal origin intended for human consumption(OJ No. L139, 30.4.2004, p.206). The revised text of Regulation (EC) No. 854/2004 is now set out in a Corrigendum (OJ No. L226, 25.6.2004, p.83) as amended by Regulation 882/2004, Regulation 2074/2005, Regulation 2076/2005, Regulation 1663/2006, Regulation 1791/2006 and Regulation 1021/2008 and as read with Directive 2004/41, Regulation 2074/2005, Regulation 2075/2005 and Regulation 2076/2005. 4. Commission Regulation (EC) No. 2073/2005 on microbiological criteria for foodstuffs (OJ No. L338, 22.12.2005, p.1, as read with the corrigenda at OJ No. L283, 14.10.2006, p.62) as amended by Regulation 1441/2007.
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10. PATHOGEN PROFILES
10.1
Bacillus cereus
10.1.1
Morphology
Gram-positive spore-forming rods; 1.0 - 1.2 x 3.0 - 7.0 µm. 10.1.2
Oxygen requirements
Facultative anaerobe - normally aerobic. 10.1.3
Temperature
Typically, the vegetative cells of B. cereus have an optimum growth temperature of 30 - 35 °C, and a maximum ranging from 48 - 55 °C (1, 2, 3). However, psychrotrophic strains have been identified - especially in milk and dairy products - capable of growing within the range 4 - 37 °C (4). Most of these strains were also reported as capable of producing enterotoxin at 4 °C after prolonged incubation (>21 days) (3, 5). 10.1.4
Heat resistance
Vegetative cells of B. cereus are readily destroyed by pasteurisation or equivalent heat treatments. However, spores can survive quite severe heat processes, but there is considerable variation between different strains. D95 - values of between 1.2 and 36 minutes have been reported (6). It has been shown that strains commonly implicated in food poisoning are more heat-resistant than other strains, and are therefore more likely to survive a thermal process. 10.1.5
pH
B. cereus has been reported to be capable of growth at pH values between 4.3 and 9.3, under otherwise ideal conditions (6, 7).
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10.1.6
Aw
The minimum water activity in which B. cereus has been reported to grow is 0.95; possibly as low as 0.91 (in fried rice) or less (6). 10.1.7
Characteristics of B. cereus toxins
The emetic toxin of B. cereus is stable in the pH range 2 - 11 (1); it is also heatresistant, and able to resist heating to 126 °C for 90 min (3, 6). This toxin is produced after active (vegetative) growth at the end of the growth cycle, and may be associated with the formation of spores. The diarrhoeal enterotoxin is unstable at pH values of < 4.0 or > 11.0 (6), and is heat-sensitive, being destroyed at 56 °C for 5 minutes (1, 6). The toxin is a protein that is produced during active growth. 10.2
Campylobacter spp.
10.2.1
Morphology
Gram-negative spirally curved rods; 0.2 - 0.8 x 0.5 - 5.0 µm. 10.2.2
Oxygen requirements
Campylobacter is both microaerophilic and 'capnophilic' (liking carbon dioxide); its growth is favoured by an atmosphere containing 10% carbon dioxide and 5 6% oxygen. Growth is also enhanced by hydrogen. The organism will normally die rapidly in the presence of air; it is particularly sensitive to oxygen breakdown products. Because of this and other growth characteristics (see below), these organisms are not normally capable of growing in foods. 10.2.3
Temperature
Campylobacter jejuni and Campylobacter coli only grow at temperatures above about 30 °C; they (and Campylobacter lari) are consequently referred to as the thermophilic group of Campylobacters. Their optimum temperature for growth is between 42 and 43 °C, with a maximum of 45 °C (8). Campylobacter survives poorly at room temperatures (around 20 - 23 °C); it dies much more quickly than at refrigeration temperatures. It can survive well for short periods at chill temperatures. On the other hand, it is generally more sensitive to freezing, although there may be some survival for long periods (9, 10, 11).
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10.2.4
Heat resistance
C. jejuni is very heat-sensitive. Heat injury can occur at 46 °C or higher. z-values range from 48 - 60 °C depending on pH (8). D-values of 7.2 - 12.8 min have been reported at 48 °C (in skimmed milk) (8). At 55 °C, the range was 0.74 - 1.0 (8). The organism cannot survive normal milk pasteurisation. 10.2.5
pH
Campylobacter has an optimum pH for growth in the range 6.5 - 7.5 and no growth is observed below pH 4.9 (8). 10.2.6
Aw/Sodium chloride
Campylobacter is particularly sensitive to drying; it does not survive well in dry environments. The minimum water activity for growth is 0.98. Campylobacter is also quite sensitive to sodium chloride (NaCl); levels of 2% or more can be bactericidal to the organism. The effect is temperature-dependent; the presence of even 1% NaCI can be inhibitory or bactericidal, depending on temperature. The bactericidal effect decreases with decreasing temperature (12). 10.3
Clostridium botulinum
Seven different types of C. botulinum are known, forming at least seven different toxins; A to G. Types A, B, E and, to a lesser extent, F are the types that are responsible for most cases of human botulism (13, 14). All type A strains are proteolytic, and type E strains are usually non-proteolytic; types B and F can be either. There are four main groupings of the organism, and Groups I and II are those responsible for cases of botulism. 10.3.1
Morphology
Gram-positive spore-forming rods; 0.5 - 2.4 x 1.7 - 22.0 µm. 10.3.2
Oxygen requirements
Although C. botulinum is a strict anaerobe, many foods that are not obviously 'anaerobic' can provide adequate conditions for growth. Thus, an aerobically packed product may not support the growth of the organism on the surface, but the interior of the food may do so. It is also important to note that the inclusion of oxygen as a packaging gas cannot ensure that growth of C. botulinum is prevented.
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10.3.3
Temperature
All strains of C. botulinum grow reasonably well in the temperature range of 20 45 °C, but the low temperatures required to inhibit Groups I (proteolytic group) and II (non-proteolytic group) are different. Group I will not grow at temperatures of 10 °C or less, but Group II strains are psychrotrophic, being capable of slow growth and toxin production at low temperatures - even as low as 3 °C (15, 16). 10.3.4
Heat resistance
The vegetative cells of C. botulinum are not particularly heat-resistant, but the spores of this organism are more so. All C. botulinum types produce heat labile toxins, which may be inactivated by heating at 80 °C for 20 - 30 min, at 85 °C for 5 min, or at 90 °C for a few seconds. 10.3.5
pH
The minimum pH for the growth of proteolytic and non-proteolytic strains is pH 4.6 and 5.0, respectively (17, 18). 10.3.6
Aw/Sodium chloride
The minimum aw for growth of C. botulinum depends on solute, pH and temperature, but under optimum growth conditions 10% (w/w) NaCl is required to prevent growth of Group I, and 5% (w/w) NaCl is necessary to prevent growth of Group II organisms. These concentrations correspond to limiting aw of 0.94 for Group I and 0.97 for Group II (13). These values have been established under carefully controlled laboratory conditions. In commercial situations, safety margins must be introduced to allow for process variability. 10.3.7
Characteristics of C. botulinum spores
The most heat-resistant spores of Group I C. botulinum are produced by type A and proteolytic B strains for which D values are 0.1 - 0.21 minutes at 121 °C (18). The spores of Group II (non-proteolytic/psychotrophic) strains are less heatresistant than Group I strains. However, they may survive mild heat treatments (70 - 85 °C) and their ability to grow at refrigeration temperatures necessitates their control in foods capable of supporting their growth (e.g. vacuum-packed, parcooked meals with pH value > 5.0 and aw > 0.97) (19, 20). D-values at 100 °C are < 0.1 minutes (18).
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10.4
Clostridium perfringens
10.4.1
Morphology
Gram-positive spore-forming rods; 0.3 - 1.9 x 2.0 - 10.0 µm. 10.4.2
Oxygen requirements
C. perfringens - like other clostridia - is an anaerobe. It will not, therefore, grow on the surface of foods unless they are vacuum- or gas-packed. The organism will grow well in the centre of meat or poultry dishes, where oxygen levels are reduced, particularly by cooking. 10.4.3
Temperature
The most significant characteristic of C. perfringens in relation to food safety is the organism's ability to grow extremely rapidly at high temperatures. Its optimum temperature range for growth is 43 - 45 °C, although C. perfringens has the potential ability to grow within the temperature range 15 - 50 °C, depending on strain and other conditions. While some growth can occur at 50 °C, death of the vegetative cells of this organism usually occurs rapidly above this temperature (21, 22). At cold temperatures (0 - 10 °C) vegetative cells die rapidly (21). 10.4.4
Heat resistance
Exposure to a temperature of 60 °C or more will result in the death of vegetative cells of C. perfringens, although prior growth at high temperatures, or the presence of fat in a food will result in increased heat resistance. (It is unusual for spores to be formed in foods after the growth of this organism) (23). In addition, the enterotoxin is not heat-resistant; it is destroyed by heating at 60 °C for 10 minutes (23, 24, 25). 10.4.5
pH
C. perfringens is not a tolerant organism with respect to pH. It grows best at pH values between 6 and 7 (the same pH as most meats). Under otherwise ideal conditions, very limited growth may occur at pH values over the range pH ≤ 5 - ≥ 8.3. Spores, however, will survive greater extremes of pH (and aw) (21, 22). 10.4.6
Aw/Sodium chloride
C. perfringens is not tolerant of low water activities. As in the case of other factors limiting the growth or survival of this organism, the limits for water activity are 149
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affected by temperature, pH, type of solute, etc. The lowest aw recorded to support the growth of C. perfringens appears to be 0.93 to 0.97 depending on the solute (glycerol and sucrose respectively) used to control aw (22, 26). Salt concentrations of 6 - 8% inhibit growth of most C. perfringens strains. Some studies indicate that the presence of 3% NaCl delays growth of C. perfringens in vacuum-packed beef (26). 10.4.7
Characteristics of C. perfringens spores
The spores of C. perfringens can vary quite considerably in their heat resistance, which is affected by the heating substrate. Recorded heat resistance values (Dvalues) at 95 °C range from 17.6 - 64.0 minutes for heat-resistant spores, to 1.3 2.8 minutes for heat-sensitive spores (21). 10.5
Cronobacter (Enterobacter) sakazakii
C. sakazakii is a new genus in the family Enterobacteriaceae. It is a taxanomic reclassification of the pathogen Enterobacter sakazakii and consists of five species; Cronobacter sakazakii (and includes Cronobacter sakazakii subsp. sakazakii and Cronobacter sakazakii subsp. malonaticus), Cronobacter turicensis, Cronobacter muytjensii, Cronobacter dublinensis and Cronobacter genomospecies 1. It accomodates the biogroups of E. sakazakii (27, 28). 10.5.1
Morphology
Gram-negative rod. 10.5.2
Oxygen requirements
C. sakazakii is a facultative anaerobe. 10.5.3
Temperature
The minimum growth temperature is between 5.5 and 8 °C. The lowest recorded temperature at which C. sakazakii is known to grow is 3.4 °C, suggesting that the organism is able to grow during refrigeration. The maximum growth temperature ranges in general from 41 – 45 °C. 10.5.4
Heat resistance
C. sakazakii is considered to be one of the most thermo-tolerant among the Enterobacteriaceae, as C. sakazakii can survive at elevated temperatures (45 °C), 150
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and has the ability to grow at temperatures up to 47 °C in warm and dry environments such as in the vicinity of drying equipment in factories. It has a competitive advantage when compared to other members of the Enterobacteriaceae. However, it does not survive a standard pasteurisation process (> 60 °C) (29, 30, 31, 32). 10.5.5
pH
Like other members of the Enterobacteriaceae, C. sakazakii is presumed to have good resistance to low pH. Survival of the organism in acid environments depends on a number of factors such as pH, acidulant identity, acidulant concentrations, temperature, water activity, atmosphere, and the presence of other inhibitory compounds (33). 10.5.6
Aw
C. sakazakii can survive in dried infant formula having a water activity of approximately 0.2. 10.6
Escherichia coli O157
10.6.1
Morphology
Gram-negative short rods; 1.1 - 1.5 x 2.0 - 6.0 µm. 10.6.2
Oxygen requirements
E. coli O157 is a facultative anaerobe; it grows well under aerobic or anaerobic conditions. High levels of carbon dioxide may inhibit its growth. 10.6.3
Temperature
The growth range for E. coli O157 is thought to be between 7 and 45°C, with an optimum of approximately 37 °C (34). (Note: E. coli O157:H7 grows poorly at 44 - 45 °C and does not grow within 48 hours at 45.5 °C. Therefore, traditional detection methods for E. coli in foods cannot be relied upon to detect E. coli O157:H7). 10.6.4
Heat resistance
E. coli O157 is not a heat-resistant organism. D-values at 57 and 63°C in meat have been reported as approximately 5 and 0.5 minutes, respectively (35). 151
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Anaerobic growth, reduced aw, high fat content and exposure to prior heat shock may result in higher D-values. However, it is unlikely to survive conventional milk pasteurisation. 10.6.5
pH
The minimum pH for growth, under optimal conditions, is 4.0 - 4.4 (using hydrochloric acid as an acidulant) (36, 37). The minimum value is affected by the acidulant used, with both lactic and acetic acids being more inhibitory than hydrochloric acid (34). E. coli O157 is unusually acid-tolerant and survives well in foods with low pH values (3.6 - 4.0), especially at chill temperatures (38). 10.6.6
Aw/ Sodium chloride
Current published data suggest that E. coli O157 grows well at NaCl concentrations up to 2.5% and may grow at concentrations of at least 6.5% (w/v) (aw less than 0.97) under otherwise optimal conditions (39). The organism appears to be able to tolerate certain drying processes (38). 10.7
Listeria spp.
10.7.1
Morphology
Gram-positive short rods; 0.4 - 0.5 x 0.5 - 2.0 µm. 10.7.2
Oxygen requirements
Aerobe or microaerophilic. 10.7.3
Temperature
Listeria monocytogenes is unusual amongst foodborne pathogens in that it is psychrotrophic, being potentially capable of growing - albeit slowly - at refrigeration temperatures down to, or even below 0 °C. However, -0.4 °C is probably the most likely minimum in foods (40). Its optimum growth temperature, however, is between 30 and 37 °C; growth at low temperatures can be very slow, requiring days or weeks to reach maximum numbers. The upper temperature limit for the growth of L. monocytogenes is reported to be 45 °C (41).
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10.7.4
Heat resistance
L. monocytogenes is not a particularly heat-resistant organism; it is not a sporeformer, so can be destroyed by pasteurisation. It has been reported to have slightly greater heat resistance than certain other foodborne pathogens. It is generally agreed that milk pasteurisation will destroy normal levels of L. monocytogenes in milk (>105/ml); the D-value is 0.1 - 0.3 minutes at 70 °C in milk. D-values at 68.9 °C for the strain Scott A were 6 seconds in raw 38% milk fat cream, and 7.8 seconds in inoculated sterile cream. z-values were 6.8 and 7.1 °C, respectively (42, 43). 10.7.5
pH
The ability of Listeria to grow at different pH values (as with other bacteria) is markedly affected by the type of acid used and temperature. Under ideal conditions, the organism is able to grow at pH values well below pH 5 (pH 4.3 is the lowest value where growth has been recorded, using hydrochloric acid as acidulant). In foods, however, the lowest limit for growth is likely to be considerably higher - especially at refrigeration temperatures, and where acetic acid is used as acidulant; pH < 5.2 has been suggested as the lowest working limit (44). 10.7.6
Aw/Sodium chloride
L. monocytogenes is quite tolerant of high NaCl/low aw. It is likely to survive, or even grow, at salt levels found in foods (10 - 12% NaCI or more). It grows best at aw of ≥ 0.97, but has been shown to be able to grow at aw level of 0.90. The bacterium may survive for long periods at aw as low as 0.83 (41). 10.8
Salmonella spp.
10.8.1
Morphology
Gram-negative short rods with peritrichous flagella; 0.5 - 0.7 x 1.0 - 3.0 µm. 10.8.2
Oxygen requirements
Facultative anaerobe.
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10.8.3
Temperature
Salmonellae can grow in the temperature range of 7 - 48 °C. However, some strains are able to grow at temperatures as low as 4 °C (45). Growth is slow at temperatures below about 10 °C, the optimum being 35 - 37 °C. Salmonellae are quite resistant to freezing, Salmonella enteritidis were isolated from ice cream held at -23 °C for 7 years (46), and may survive in some foods for a number of years. 10.8.4
Heat resistance
Salmonella is not a spore-forming organism. It is not, therefore, a heat-resistant organism; pasteurisation and equivalent treatments will destroy the organism under normal circumstances. D values normally range from about 1 to 10 min at 60 °C, with a z-value of 4 - 5 °C. However, high fat or low aw will reduce the effectiveness of heat treatments, and appropriate heat treatments must be determined experimentally for low aw foods. Furthermore, strains vary in their ability to withstand heating; Salmonella senftenberg 775W is about 10 to 20 times more heat-resistant than the average strain of Salmonella at high aw (47). The Dvalue for S. senftenberg in milk at 71.7 °C is 0.02 minutes, and the D-value for Salmonella spp. in milk at 68.3 °C is 0.01 minutes (47). 10.8.5
pH
Salmonella has a pH range for growth of 3.8 - 9.5, under otherwise ideal conditions, and with an appropriate acid. Some death will occur at pH values of less than about 4.0, depending on the type of acid and temperature. The optimal pH for Salmonella growth is between 6.5 - 7.5. 10.8.6
Aw/Sodium chloride
Where all other conditions are favourable, Salmonella has the potential to grow at aw levels as low as 0.945, or possibly 0.93 (as reported in dried meat and dehydrated soup), depending on serotype, substrate, temperature and pH. Salmonellae are quite resistant to drying. The growth of Salmonella is generally inhibited by the presence of 3 - 4% NaCl, although salt tolerance increases with increasing temperature (48). 10.9
Staphylococcus aureus
10.9.1
Morphology
Gram-positive cocci; 0.7 - 0.9 µm diameter. 154
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10.9.2
Oxygen requirements
Facultative anaerobe. The growth of Staph. aureus is more limited under anaerobic than under aerobic conditions. The limits for toxin production are also narrower than for growth. The following relate to limits for growth only. 10.9.3
Temperature
Under otherwise ideal conditions Staph. aureus can grow within the temperature range 7 - 48.5 °C, with an optimum of 30 - 37 °C (49). It can survive well at low temperatures. Freezing and thawing have little effect on Staph. aureus viability, but may cause some cell damage (50). 10.9.4
Heat resistance
Heat resistance depends very much on the food type in which the organism is being heated (conditions relating to pH, fat content, water activity, etc.). As is the case with other bacteria, stressed cells can also be less tolerant of heating. Under most circumstances, however, the organism is heat-sensitive and will be destroyed by pasteurisation. In milk, the D-value at 60 °C is 1 - 6 minutes, with a z-value of 7 - 9 °C. 10.9.5
pH
The pH at which a staphylococcal strain will grow is dependent on the type of acid (acetic acid is more effective at destroying Staph. aureus than citric acid), water activity and temperature (sensitivity to acid increases with temperature). Most strains of staphylococci can grow within the pH range 4.2 to 9.3 (optimum 7.0 - 7.5), under otherwise ideal conditions (49, 51). 10.9.6
Aw/Sodium chloride
Staph. aureus is unusual amongst food-poisoning organisms in its ability to tolerate low water activities. It can grow over the aw range 0.83 - > 0.99 aerobically under otherwise optimal conditions. However, an aw of 0.86 is the generally recognised minimum in foods (52). Staphylococci are more resistant to salt present in foods than other organisms. In general, Staph. aureus can grow in 7 - 10% salt, but certain strains can grow in 20%. An effect of increasing salt concentration is to raise the minimum pH for growth.
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10.9.7
Limits permitting toxin production
Temperature:
10 - 45 °C (optimum between 35 and 40 °C) (very little toxin is produced at the upper and lower extremes) (51)
pH:
5.2 - 9.0 (optimum 7.0 and 7.5) (49, 51)
*Aw:
between 0.87 and > 0.99
Atmosphere:
little or no toxin production in anaerobically packed foods, especially vacuum-packed foods (53)
Heat Resistance: enterotoxins are quite heat-resistant. In general, heating at 100 °C for at least 30 minutes may be required to destroy unpurified toxin (51, 54). * dependent on temperature, pH, atmosphere, strain, and solute. 10.10
Yersinia enterocolitica
10.10.1 Morphology Gram-negative short rods (occasionally coccoid); 0.5 - 1.0 x 1.0 - 2.0 µm. 10.10.2 Oxygen requirements Facultative anaerobe. Carbon dioxide has some inhibitory effect on the growth of Y. enterocolitica. Vacuum packaging can retard growth to a lesser extent. 10.10.3 Temperature Yersinias are psychrotrophic organisms, being capable of growth at refrigeration temperatures. Extremely slow growth has been recorded at temperatures as low as 0 to -1.3 °C. However, the optimum temperature for growth of Y. enterocolitica is 28 - 29 °C with the reported growth range of -2 - 42 °C (55, 56, 57). The maximum temperature where growth has been recorded is 44 °C (57, 58). The organism is quite resistant to freezing and has been reported to survive in frozen foods for long periods (55, 56). 10.10.4 Heat resistance The organism is sensitive to heat, being easily killed at temperatures above about 60 °C. D-values of between 0.18 and 0.96 minutes at 62.8 °C in milk have been 156
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reported (57); D-values in scaling water were 96, 27 and 11 seconds at 58 °C, 60 °C and 62 °C respectively (56). It will therefore be destroyed by standard milk pasteurisation (55). 10.10.5 pH Yersinia is sensitive to pH values of less than 4.6 (more typically 5.0) in the presence of organic acids, e.g. acetic acid. Y. enterocolitica are not able to grow at pH < 4.2 or > 9.0. A lower pH minimum for growth (pH 4.1 - 4.4) has been observed with inorganic acids, under otherwise optimal conditions. Its optimum is pH 7.0 - 8.0; they tolerate alkaline conditions extremely well (59). 10.10.6 Aw/Sodium chloride Yersinia may grow at salt concentrations up to about 5% (aw 0.96), but no growth occurs at 7% (aw 0.945). Growth is retarded in foods containing 5% salt (57, 59). 10.11
References
1. Rajkowski K.T., Bennett R.W. Bacillus cereus, in International Handbook of Foodborne Pathogens. Eds. Miliotis M.D., Bier J.W. New York, Marcel Dekker. 2003, 27-40. 2. Fermanian C., Fremy J.M., Claisse M. Effect of temperature on the vegetative growth of type and field strains of Bacillus cereus. Letters in Applied Microbiology, 1994, 19 (6), 414-8. 3. International Commission on Microbiological Specifications for Foods. Bacillus cereus, in Microorganisms in Foods, Volume 5: Microbiological Specifications of Food Pathogens. Ed. International Commission on Microbiological Specifications for Foods. London, Blackie. 1996, 20-35. 4. van Netten P., van de Moosdijk A., van Hoensel P., Mossel D.A.A., Perales I. Psychrotrophic strains of Bacillus cereus producing enterotoxin. Journal of Applied Bacteriology, 1990, 69 (1), 73-9. 5. Dufrenne J., Soentoro P., Tatini S., Day T., Notermans S. Characteristics of Bacillus cereus related to safe food production. International Journal of Food Microbiology, 1994, 14 (2), 87. 6. Kramer J.M., Gilbert R.J. Bacillus cereus and other Bacillus species, in Foodborne Bacterial Pathogens. Ed. Doyle M.P. New York, Marcel Dekker. 1989, 21-70. 7. Fermanian C., Fremy J.-M., Lahellec C. Bacillus cereus pathogenicity: a review. Journal of Rapid Methods and Automation in Microbiology, 1993, 2 (2), 83-134.
157
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DAIRY PRODUCTS 8. International Commission on Microbiological Specifications for Foods. Campylobacter, in Microorganisms in Foods, Volume 5: Microbiological Specifications of Food Pathogens. Ed. International Commission on Microbiological Specifications for Foods. London, Blackie. 1996, 45-65. 9. Hu L. Kopecko D. J. Campylobacter Species, in International Handbook of Foodborne Pathogens. Eds. Miliotis M. D., Bier J. W. New York, Marcel Dekker. 2003, 181-98. 10. Park S. Campylobacter: stress response and resistance, in Understanding Pathogen Behaviour: Virulence, Stress Response and Resistance. Ed. Griffiths M. Cambridge, Woodhead Publishing Ltd. 2005, 279-308. 11. Doyle M.P. Campylobacter jejuni, in Foodborne Diseases. Ed. Cliver D.O. London, Academic Press. 1990, 218-22. 12. Doyle M.P., Roman D.J. Growth and survival of Campylobacter fetus subsp. jejuni as a function of temperature and pH. Journal of Food Protection, 1981, 44 (8), 596601. 13. Austin J. Clostridium botulinum, in Food Microbiology: Fundamentals and Frontiers. Eds. Doyle M.P., Beuchat L.R., Montville T.J. Washington DC, ASM Press. 2001, 329- 49. 14. Novak J., Peck M., Juneja V., Johnson E. Clostridium botulinum and Clostridium perfringens, in Foodborne Pathogen. Microbiology and Molecular Biology. Eds. Fratamico P.M., Bhunia A.K., Smith J.L. Great Britain, Caister Academic Press. 2005, 383-408. 15. Kim J., Foegeding P.M. Principles of Control, in Clostridium botulinum: Ecology and Control in Foods. Eds. Hauschild A.H.W., Dodds K.L. New York, Marcel Dekker. 1993, 121-76. 16. Lund B.M, Peck M.W. Clostridium botulinum, in The Microbiological Safety and Quality of Food, Volume 2. Eds. Lund B.M., Paird-Parker T.C., Gould G.W. Gaithershurg, Aspen Publications. 2000, 1057 – 1109. 17. Dodds, K.L. Clostridium botulinum, in Foodborne Disease Handbook, Volume 1: Diseases Caused by Bacteria. Eds. Hui Y.H., Gorman J.R., Murrell K.D., Cliver D.O. New York, Marcel Dekker. 1994, 97-131. 18. Hauschild A.H.W. Clostridium botulinum, in Foodborne Bacterial Pathogens. Ed. Doyle M.P. New York, Marcel Dekker. 1989, 111-89. 19. Lund B.M., Notermans S.H.W. Potential hazards associated with REPFEDS, in Clostridium botulinum: Ecology and Control in Foods. Eds. Hauschild A.H.W., Dodds K.L. New York, Marcel Dekker. 1993, 279-303. 20. Betts G.D., Gaze J.E. Growth and heat resistance of psychrotrophic Clostridium botulinum in relation to `sous vide’. Food Control, 1995, 6 (1), 57-63. 21. Wrigley D.M. Clostridium perfringens, in Foodborne Disease Handbook, Volume 1: Diseases Caused by Bacteria. Eds. Hui Y.H., Gorham J.R., Murrell K.D., Cliver D.O. New York, Marcel Dekker. 1994, 133-67. 22. Labbe R., Juneja V.K. Clostridium perfringens gastroenteritis, in Foodborne Infection and Intoxication. Eds. Riemann H.P, Cliver D.O. London, Elsevier. 2006, 137-64. 158
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PATHOGEN PROFILES 23. Labbe R. Clostridium perfringens, in Foodborne Bacterial Pathogens. Ed. Doyle M.P. New York, Marcel Dekker. 1989, 191-243. 24. Lund B.M. Foodborne disease due to Bacillus and Clostridium species. Lancet, 1990, 336 (8721), 982-6. 25. Johnson E.A. Clostridium perfringens food poisoning, in Foodborne Diseases. Ed. Cliver D.O. London, Academic Press. 1990, 229-40. 26. McClane B.A. Clostridium perfringens, in Food Microbiology: Fundamentals and Frontiers. Eds. Doyle M.P., Beuchat L.R., Montville T.J. Washington D.C., ASM Press. 2001, 351-82. 27. Iversen C., Lehner A., Mullane N., Marugg J., Fanning S., Stephan R., Joosten H. Bidlas E., Cleenwerck I. The taxonomy of Enterobacter sakazakii: proposal of a new genus Cronobacter gen. nov. and descriptions of Cronobacter sakazakii comb. nov. Cronobacter sakazakii subsp. sakazakii, comb. nov., Cronobacter sakazakii subsp. malonaticus subsp. nov., Cronobacter turicensis sp. nov., Cronobacter muytjensii sp. nov., Cronobacter dublinensis sp. nov. and Cronobacter genomospecies 1. BMC Evolutionery Biolog,. 2007; 7 (64) 28. Iversen C., Lehner A., Mullane N., Marugg J., Fanning S., Stephan R., Joosten H. Identification of “Cronobacter” spp. (Enterobacter sakazakii). Journal of Clinical Microbiology, 2007, 45 (11), 3814–6. 29. Grant I.R., Houf K., Cordier J.-L., Stephan R., Becker B., Baumgartner A. Enterobacter sakazakii. Mitteilungen aus Lebensmitteluntersuchung und Hygiene, 2006, 97 (1), 22-7. 30. Baxter. P. Have you heard of Enterobacter sakazakii? Journal of the Association of Food and Drugs Officals, 2005, 69 (1), 16-7. 31. Breeuwer P., Lardeau A., Peterz M., Joosten H.M. Desiccation and tolerance of Enterobacter sakazakii. Journal of Applied Microbiology, 2003, 95 (3), 967-73. 32. Deseo J. Emerging pathogen: Enterobacter sakazakii. Inside Laboratory Management, 2003, 7 (3), 32-4. 33. Kim H., Ryu J.-H., Beuchat L.R. Survival of Enterobacter sakazakii on fresh produce as affected by temperature, and effectiveness of sanitisers for its elimination. International Journal of Food Microbiology, 2006, 111 (2), 134-43. 34. Advisory Committee on the Microbiological Safety of Food. Report on verocytotoxinproducing Escherichia coli. London, HMSO. 1995. 35. Meng J., Doyle M.P., Zhao T., Zhao S. Detection and control of Escherichia coli O157:H7 in foods. Trends in Food Science and Technology, 1994, 5 (6), 179-85. 36. Buchanan R.L., Bagi L.K. Expansion of response surface models for the growth of Escherichia coli O157:H7 to include sodium nitrite as a variable. International Journal of Food Microbiology, 1994, 23 (3, 4), 317-32. 37. International Commission on Microbiological Specifications for Foods. Intestinally pathogenic Escherichia coli, in Microorganisms in Foods, Volume 5: Microbiological Specifications of Food Pathogens. Ed. International Commission on Microbiological Specifications for Foods. London, Blackie. 1996, 126-40.
159
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DAIRY PRODUCTS 38. Meng J., Doyle M.P. Microbiology of Shiga-toxin-producing Escherichia coli in foods, in Escherichia coli O157:H7 and Other Shiga Toxin-producing E. coli Strains. Eds. Kaper J.P., O’Brien A.D. Washington D.C., American Society for Microbiology. 1998, 92-108. 39. Glass K.A., Loeffelholz J.M., Ford J.P., Doyle M.P. Fate of Escherichia coli O157:H7 as affected by pH or sodium chloride and in fermented, dry sausage. Applied and Environmental Microbiology, 1992, 58 (9), 2513-6. 40. Walker S.J., Archer P., Banks J.G. Growth of Listeria monocytogenes at refrigeration temperatures. Journal of Applied Bacteriology, 1990, 68 (2), 157-62. 41. Listeria monocytogenes, in Food Microbiology - An Introduction. Eds. Montville T.J., Matthews K.R. Washington, ASM Press. 2005, 173-88. 42. International Commission on Microbiological Specifications for Foods. Listeria monocytogenes, in Microorganisms in Foods, Volume 5: Microbiological Specifications of Food Pathogens. Ed. International Commission on Microbiological Specifications for Foods. London, Blackie. 1996, 141-82. 43. Bradshaw J.G., Peeler J.T., Corwin J.J., Hunt J.M., Twedt R.M. Thermal Resistance of Listeria monocytogenes in dairy products. Journal of Food Protection, 1987, 50 (7), 543-4. 44. Ryser E.T., Marth E.H. Listeria, Listeriosis and Food Safety. New York, Marcel Dekker. 2007. 45. Kim C.J., Emery D.A., Rinke H., Nagaraja K.V., Halvorson D.A. Effect of time and temperature on growth of Salmonella enteritidis in experimentally inoculated eggs. Avian Disease, 1989, 33, 735-42. 46. Wallace G.I. The Survival of Pathogenic Microorganisms in Ice Cream. Journal of Dairy Science, 1938, 21 (1), 35-6. 47. International Commission on Microbiological Specifications for Foods. Salmonellae, in Microorganisms in Foods, Volume 5: Microbiological Specifications of Food Pathogens. Ed. International Commission on Microbiological Specifications for Foods. London, Blackie. 1996, 217-64. 48. D’Aoust, J.-Y. Salmonella, in Foodborne Bacterial Pathogens. Ed. Doyle M.P. New York, Marcel Dekker. 1989, 327-445. 49. Gustafson J., Wilkinson B. Staphylococcus aureus as a food pathogen: staphylococcal enterotoxins and stress response systems, in Understanding Pathogen Behaviour Virulence, Stress Response and Resistance. Ed. Griffiths M. Cambridge, Woodhead Publishing, 2005, 331-57. 50. Reed G.H. Foodborne illness (Part 1): Staphylococcal (“Staph”) food poisoning. Dairy, Food and Environmental Sanitation, 1993, 13 (11), 642. 51. Bergdoll M.S, Lee Wong A.C. Staphylococcal intoxications, in Foodborne Infections and Intoxications. Eds. Riemann H.P., Cliver D.O. London, Academic Press. 2005, 523- 62. 52. Jay J.M., Loessner M.J., Golden D.A. Staphylococcal gastroenteritis, in Modern Food Microbiology. Eds. Jay J.M., Loessner M.J., Golden D.A. New York, Springer Science. 2005, 545-66. 160
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PATHOGEN PROFILES 53. Bergdoll M.S. Staphylococcal Food Poisoning, in Foodborne Disease. Ed. Cliver D.O. London, Academic Press. 1990, 85-106. 54. Stewart G.C. Staphylococcus aureus, in Foodborne Pathogens: Microbiology and Molecular Biology. Eds. Fratamico P.M., Bhunia A.K., Smith J.L. Wymondham, Caister Academic Press. 2005, 273-84. 55. Nesbakeen T. Yersinia enterocolitica, in Foodborne Infections and Intoxications. Eds. Reimann H.P., Cliver D.O. Oxford, Elsevier. 2006, 289-312. 56. Nesbakeen T. Yersinia enterocolitica, in Emerging Foodborne Pathogens. Eds. Motarjemi Y., Adams M. Cambridge, Woodhead Publishing. 2006, 373-405. 57. International Commission on Microbiological Specifications for Foods. Yersinia enterocolitica, in Microorganisms in Foods, Vlume 5. Microbiological Specifications of Food Pathogens. Ed. International Commission on Microbiological Specifications for Foods. London, Blackie. 1996, 458-78. 58. Feng P., Weagant S.D. Yersinia, in Foodborne Disease Handbook, Voume 1. Diseases Caused by Bacteria. Eds. Hui Y.H., Gorham J.R., Murrell K.D., Cliver D.O. New York, Marcel Dekker. 1994, 427-60. 59. Robins-Browne, R.M. Yersinia enterocolitica, in Food Microbiology: Fundamentals and Frontiers. Eds. Doyle M.P., Beuchat L.R., Montville T.J. Washington D.C., ASM Press 1997, 192-215.
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Addresses of Trade Associations and Professional Bodies The Dairy Council Henrietta House 17-18 Henrietta Street Covent Garden London WC2E 8QH United Kingdom Tel: + 44 (0) 207 3954030 Fax: + 44 (0) 207 2409679 Email: [email protected] Web site: www.milk.co.uk
International Dairy Federation (lDF) Diamant Building, Boulevard Auguste Reyers 80 1030 Brussels Belgium Tel: + 32 27339888 Fax: + 32 27330413 Email: [email protected] Web site: www.fil-idf.org Irish Dairy Industries Association (Food and Drink Industry Ireland) Confederation House 84-86 Lower Baggot Street Dublin 2 Ireland Tel: + 353 1 6051560 Fax: + 353 1 6381560 Email: [email protected] Web site: www.fdii.ie
Dairy Industry Federation 19 Cornwall Terrace London NW1 4QP United Kingdom Tel: + 44 (0) 207 4867244 Fax: + 44 (0) 207 4874734 Email: [email protected] European Dairy Association (EDA) 14 Rue Montoyer 1000 Brussels Belgium Tel: + 32 25495040 Fax: + 32 25495049 Email: [email protected] Web site: www.euromilk.org
Scottish Dairy Trade Federation Phoenix House South Avenue Clydebank Glasgow G81 2LG United Kingdom Tel: + 44 (0)141 9511170 Fax: + 44 (0) 141 9511129
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Fax: + 44 (0) 207 2382188 Email: [email protected] Web site: www.defra.gov.uk
American Dairy Science Association (ADSA) 1111 N. Dunlap Avenue Savoy IL 61874 United States of America Tel: + 1 21 73565146 Fax: + 1 21 73984119 Email: [email protected] Web site: www.adsa.org
Institute of Food Research (IFR) Norwich Research Park Colney lane Norwich NR4 7UA United Kingdom Tel: + 44 (0) 160 3255000 Fax: + 44 (0)160 3507723 Web site: www.ifr.ac.uk
Society of Dairy Technology PO Box 12 Appleby in Westmorland Cumbria CA16 6YJ United Kingdom Tel: + 44 (0) 1768 354034 Email: [email protected] Web site: www.sdt.org
Institute of Food Science and Technology (IFST) 5 Cambridge Court 210 Shepherds Bush Road London W6 7NL United Kingdom TeI: + 44 (0) 207 6036316 Fax: + 44 (0) 207 6029936 Email: [email protected] Web site: www.ifst.org
Other Sources of Information Food Standards Agency Aviation House 125 Kingsway London WC2B 6NH United Kingdom Tel: + 44 (0) 207 2768000 Fax: + 44 (0) 207 238 6330 Emergencies only: + 44 (0) 207 270 8960 Email: [email protected] Web site: www.foodstandards.gov.uk
Health Protection Agency (HPA) Centre for Infections 61 Colindale Avenue London NW9 5EQ United Kingdom TeI: + 44 (0) 208 2004400 Fax: + 44 (0) 208 2007868 Web site: www.hpa.org.uk Chilled Food Association PO Box 6434 Kettering NN15 5XT United Kingdom TeI: + 44 (0) 1536 514365 Fax: + 44 (0) 1536 515395 Email: [email protected] Web site: www.chilledfood.org
Department for Environment Food and Rural Affairs (Defra) Nobel House 17 Smith Square London SW1P 3JR United Kingdom Tel: + 44 (0) 207 2386000 164
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Food and Drink Federation (FDF) 6 Catherine Street London WC2B SJJ United Kingdom TeI: + 44 (0) 207 8362460 Fax: + 44 (0) 207 8360580 Email: [email protected] Web site: www.fdf.org.uk Useful Web Sites Gateway to Government Food Safety Information (US) http://www.FoodSafety.gov/ World Health Organization (WHO): Food safety programmes and projects http://www.who.int/foodsafety/en/ European Commission: Activities of the European Union - Food Safety http://europa.eu/pol/food/index_en.htm Centre for Disease Control and Prevention (CDC) (US) http://www.cdc.gov/foodsafety/ Food Safety Authority of Ireland http://www.fsai.ie/ Food Science Australia http://www.foodscience.csiro.au/ International Association for Food Protection http://www.foodprotection.org/ Institute of Food Technologists http://www.ift.org/ Grocery Manufacturers Association http://www.gmaonline.org/ Royal Society for Public Health (UK) http://www.rsph.org.uk/ Society of Food Hygiene and Technology (UK) http://www.sofht.co.uk/
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INDEX Achromobacter spp., in spoilage of cheese 68 in spoilage of UHT processed milk 10 Acid buttermilk 79 Acidophilus milk, production of 77, 79 Acinetobacter, in spoilage of processed milk 9 in spoilage of UHT processed milk 10 Aeromonas spp., survival in fermented milks 88 Aflatoxin M1, in butter 57 in dried milk 33 Aflatoxins, in ice cream 103 in pasteurised milk products 15 Ageing, in ice cream production 99 Alcaligenes metacaligenes, in spoilage of cottage cheese 68 Alcaligenes, in spoilage of cheese 68 in spoilage of processed milk 9 in spoilage of stored raw milk 3 Alcaligenes viscolactis, in spoilage of cottage cheese 68 Alginates, as stabilisers in ice cream 96-7 Alternaria, in spoilage of butter 55 in spoilage of cheese 68 in spoilage of yoghurt 86 Antimicrobial factors, natural – in bovine milk 2-3 Aspergillus, in spoilage of butter 55 in spoilage of cheese 68 in spoilage of yoghurt 86 Aspergillus niger, causing discolouration in cheese 69 Autothermal Thermophilic Aerobic Digester friction process, in production of cream 41 Bacillus cereus, as cause of food-poisoning associated with cream 45 as cause of sweet curdling in cream 42 as cause of sweet curdling in milk 8 as contaminant in ice cream 96 growth and survival in cream 45 in spoilage of cream 42 growth and survival in fermented milks 88 isolated in ice cream 102 isolated in pasteurised milk 6 pathogen profile 145-6
Bacillus coagulans, in spoilage of sweetened condensed milk 29 surviving heat processing in cream production 42 Bacillus licheniformis, in spoilage of sweetened condensed milk 29 surviving heat processing in cream production 42 Bacillus megaterium, in spoilage of sweetened condensed milk 29 Bacillus polymyxa, in spoilage of dairy spreads 56 Bacillus pumilus, as contaminant in cream 42 Bacillus spp., causing discolouration in cheese 69 causing outbreaks of food poisoning 14 growth and survival in dried milk 32 in butter and dairy spreads 49 in pasteurised milk products 14 in spoilage of cheese 68 in spoilage of condensed milk 28 in spoilage of UHT processed milk 10 thermoduric microflora in milk 8 Bacillus stearothermophilus, in spoilage of sweetened condensed milk 29 Bacillus subtilis, in spoilage of sweetened condensed milk 29 Bacillus sporothermodurans, survival in UHTtreated milk 7 Bacillus sporothermophilus, as contaminant in cream 42 in spoilage of evaporated milk 25 Bacillus subtilis, surviving heat in processing of cream 42 Bacterial spoilage, of butter 55 of cheese 68-9 Bactofugation, in processing of milk and cheese 7, 63 Bio yoghurts, production of 79-80 Bitty cream, caused by Bacillus cereus 8, 42 Botulinum, outbreak associated with cheese 73 outbreak associated with yoghurt 88 Bovine milk, composition 1 initial microflora 1-2 Brining, in cheese production 66
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DAIRY PRODUCTS Brucella abortus, presence in cheese 73 Brucella melitensis, presence in cheese 73 Bulk condensed milk, 21 processing of 23-4 Butter 49-59 initial microflora 49 packaging of 52 pasteurisation of 50-1 processing of 50-1 production of (Fig.) 50 ripened cream 51-4 spoilage of 55 Buttermilk, traditional or natural, fermentation of 77-8 Campylobacter jejuni enteritis, outbreaks associated with butter 57 Campylobacter spp., in contamination of butter 57 in pasteurised milk products 11 in raw milk 10 pathogen profile 146-7 Campylobacteriosis, outbreaks caused by pasteurised milk products 11 Candida lipolyticum, in spoilage of bakers’ cream 43 in spoilage of butter 55 Candida pseudotropicalis, in spoilage of cream 43 Candida spp., as contaminant in ice cream 96 in spoilage of cheese 68 in spoilage of yoghurt 85 Carbon dioxide addition, in processing of raw milk 4 Carboxymethyl cellulose, as stabiliser in ice cream 96-7 Carrageenan, as stabiliser in ice cream 96-7 Cassatas, definition 94 Centrifugal separators, use in production of cream 39-40 Cheese 61-74 bacterial spoilage 68-9 discolouration 69 growth and survival of pathogens 69-74 processing 62-7 production (Fig.) 62 value-added 67 Churning, in production of butter 52 Citrobacter, in spoilage of processed milk 9 Cladosporium, in spoilage of butter 55 in spoilage of cheese 68 Clostridium botulinum, growth and toxin production after carbon dioxide addition in processing of raw milk 4 in spoilage of cheese 73 pathogen profile 147-8 survival in fermented milks 88
Clostridium butyricum, causing late blowing in cheese 68-9 Clostridium perfringens, pathogen profile 14950 Clostridium sporogenes, causing late blowing in cheese 68-9 Clostridium spp., growth and survival in condensed/evaporated milk 30 in butter and dairy spreads 49 in spoilage of sweetened condensed milk 29 thermoduric microflora in milk 8 Clostridium tyrobutyricum, causing late blowing in cheese 68-9 Clotted cream, definition 37 processing 42 Colostrum, composition 1 Colours, in ice cream 97 Concentrated and dried milk products, initial microflora 22 Concentrated milk, growth and survival of pathogens 30-3 processing of 23 spoilage of 28-30 Concentrated milk products 21-35 Condensed milk, bulk 21 growth and survival of pathogens 30 processing of 23-4 production (Fig.) 24 spoilage of 28-9 sweetened 21 sweetened – processing of 24-5 sweetened – spoilage of 29 Cooling, in butter production 51 in ice cream production 99 Cooling and packaging, of processed cream 41 of yoghurt 84 Cream 37-47 cultured – production of 78 definitions 37-8 fresh – as ingredient of ice cream 95 growth and survival of pathogens 43-6 initial microflora 38 processing of 38-41 production of (Fig.) 39 spoilage of 42-3 Cream-based desserts, definition 37 processing of 42 Cream ices, definition 93 Crohn’s disease, caused by MAP 14 Cronobacter, growth and survival in dried milk 32-3 in spoilage of processed milk 9 Cronobacter sakazakii, in dried milk, causing neonatal meningitis 32-3 pathogen profile 150-1
168
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INDEX Cryptococcus, in spoilage of butter 55 Crystallisation, in production of dairy spreads 54 Cultured cream, production of 78 Curd formation, in cheese production 65-6 Custards, definition 93 Dairy spreads 49-59 initial microflora 49 packaging 54 production 53-4 spoilage of 55-6, 57 Debaryomyces hansenii, in spoilage of cheese 68 Deep cooling, in processing of raw milk 4 Discolouration, in cheese 69 Distribution, of ice cream 100 Dried and concentrated milks, growth and survival of pathogens 30-3 spoilage of 28-30 Dried milk, growth and survival of pathogens 31-2 processing 26-8 spoilage of 30 spray drying 26-7 Dried milk products 21-35 Emulsification, in production of dairy spreads 53 in production of ice cream 97 Enterobacter, refer to Cronobacter Enterobacteriaceae, causing faecal taints in processed milk 9 in spoilage of condensed milk 28 surviving the drying process in milk processing 27 Enterococci, causing discolouration in cheese 69 in spoilage of condensed milk 28 Enterococcus faecalis, growth in dairy spreads 54 isolated in pasteurised milk 6 Enterococcus faecium, concern over use as starter culture in fermented milks 89 growth in dairy spreads 54 isolated in pasteurised milk 6 Enterobacteriaceae, presence in stored raw milk 3 Enteropathogenic E. coli, causing outbreaks of disease associated with cheese 69, 71 Escherichia coli, causing spoilage in cheese 71 Escherichia coli O157 151-2 in raw milk 10 outbreak of infection by 46 Escherichia coli O157:H7, survival in fermented milks 87 Escherichia faecium, in spoilage of dairy spreads 56
EU food hygiene legislation 119-43 legislative structure 120-1 Evaporated milk, 21-2 growth and survival of pathogens 30 processing of 25-6 production (Fig.) 26 stabilisation 25 Faecal taints, caused by Enterobacteriaceae in processed milk 9 Fermentation, of milk 83-4 Fermented milk 77-91 growth and survival of pathogens 86-9 production of (Fig) 82 Filling and packaging, of processed milk 8 Flavobacterium spp., causing discolouration in cheese 69 in spoilage of butter 55 in spoilage of cheese 68 in spoilage of processed milk 9 presence in stored raw milk 3 Flavours, in ice cream 97 Food Hygiene (England) Regulations 140-1 Food hygiene legislation (EU) 119-43 Food safety criteria, EU legislation (Table) 133 Foot and Mouth Disease virus, in raw milk 14 Freezing, in ice cream production 99 French ice creams, definition 93 Fresh cream, as ingredient of ice cream 95 Fresh whole milk, as ingredient of ice cream 95 Frozen cream, definition 37 processing of 42 Frozen yoghurts, definition 94 Fungal spoilage, of butter 55 of cheese 67-8 Fusarium, in cheese spoilage 68 Geotrichum candidum, in spoilage of bakers’ cream 43 in spoilage of butter 55 in spoilage of cheese 68 Glyceryl monostearate, as emulsifier in ice cream 97 Gram-negative psychrotrophs, causing ropiness and partial coagulation in processed milk 9 Gram-positive species, presence in stored raw milk 3 Guar, as stabiliser in ice cream 97 HACCP 105-18 EU legislation 125 implementation and review of plan 115-6 logic sequence for application (Fig.) 108 seven basic principles 106-7 twelve stages of logic sequence 107-115 Haemolytic uraemic syndrome, caused by VTEC in ice cream 102
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DAIRY PRODUCTS Hard/low-moisture cheese, definition 61 Heat treatment, in processing of fermented milk 83 in production of cream 40-1 in production of ice cream 98 High-pressure processing, of milk 7 High-temperature short-time treatment, in ice cream production 98 Histamine, presence in cheese 74 Homogenisation, in processing of raw milk 5 in production of cream 40 in production of ice cream 98 HTST processes, in production of cream 40 Hygiene of foodstuffs, EU Regulation 121 Hygiene rules for food of animal origin, EU legislation 125-31 Ice cream and related products 93-104 Ice cream, growth and survival of pathogens 101 ingredients 95-7 processing 94-9 production of (Fig.) 95 Ices, definition 93 Immunoglobulins, effect on pathogens in bovine milk 2 Irradiation, in processing of milk 7 Johne’s disease, caused by MAP 14 Kefir, production 80 Klebsiella, in spoilage of processed milk 9 Kluyveromyces, in spoilage of yoghurt 85 Kluyveromyces marxianus, in spoilage of cheese 68 Koumiss, production of 80 Lactic acid bacteria, as starter cultures (Table) 65 Lactic fermentations, of fermented milks 7780 Lactobacilli, isolated in pasteurised milk 6 Lactobacillus, as starter culture in thermophilic fermentation of milk 78-9 Lactobacillus delbrueckii, as starter culture for cheese 63 Lactobacillus delbrueckii subsp. bulgaricus, as starter culture in acid buttermilk production 79 as starter culture in yoghurt production 79 83 Lactobacillus helveticus, as starter culture for cheese 63 Lactococcus spp., as starter cultures in fermentation of buttermilk 77-8 Lactococcus lactis, as starter culture for cheese 63 Lactococcus lactis biovar diacetylis, as starter culture for ripened cream butter 51 Lactococcus lactis subsp. lactis, as starter culture for ripened cream butter 51
Lactococcus mesenteroides subsp. cremoris, as starter culture for ripened cream butter 51 Lactoferrin, antimicrobial activity in bovine milk 3 Lactoperoxidase, bactericidal activity in bovine milk 3 Late blowing, in cheese 68-9 Lben, fermented dairy product 78 Leaky butter, as result of inadequate working in production 52 Legislation, EU food hygiene 119-43 Leuconostoc mesenteroides subsp. cremoris, as starter culture for ripened cream butter 51 as starter culture in fermentation of buttermilk 78 Liquid milk products 1-19 Listeria monocytogenes, causing outbreaks of disease associated with cheese 69 contaminant in butter 56-7 contaminant in ice cream 96,100, 101-2 growth in cream 44 growth in dairy spreads 57 growth in dried milk 32 growth in pasteurised milk products 11-2 growth in raw milk 10 increase in heat resistance in ice cream production 98 survival in fermented milks 86-7 survival of drying process in milk processing 27 survival of thermisation of raw milk 4 Listeria spp., causing spoilage in cheese 63, 70-1 pathogen profile 152-3 Listeriosis, associated with butter 56-7 associated with cheese 69 associated with ice cream 102 associated with pasteurised milk products 11-2 Locust bean, as stabiliser in ice cream 97 Logic sequence, for application of HACCP (Fig.) 107 Long-time pasteurisation, in ice cream production 98 Lysozyme, effect on bacteria in bovine milk 3 Mala, fermented dairy product 78 MAP, as cause of Johne’s and Crohn’s disease 14 Mastitis, as cause of contamination in bovine milk 1-2 Maziwa, fermented dairy product 78 Mesophilic fermentation, of milk 77-8 Microbacterium lacticum, survival of pasteurisation process in butter 51 Microbial rennet, in cheese production 66 Microbiological criteria for foodstuffs, EU legislation 132-40
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INDEX Micrococcus, in spoilage of butter 55 isolated in pasteurised milk 6 Microfiltration, in processing of milk 7 Microflora, initial – of bovine milk 1-2 of butter and dairy spreads 49 of cheese 62 of concentrated and dried milk products 22 of cream 38 of fermented milk 81 of ice cream products 94 Microwaving, in processing of milk 7 Milk ices, definition 93 Milk products, liquid 1-19 Mixing, in ice cream production 97 Modified-atmosphere packaging, of cheese to prevent mould growth 68 Monilia, in cheese spoilage 68 Mould, as indicator of post-process contamination in milk 9 growth on cheese 67-8 in spoilage of butter 55 in spoilage of dried milks 30 in spoilage of yoghurt 86 Mould-lactic fermentations, of milk 80-1 Mousse, definition 93 Mucor, in spoilage of butter 55 in spoilage of cheese 68 in spoilage of yoghurt 86 Mucor miehei, use in coagulation in cheese production 66 Mycobacterium avium subsp. paratuberculosis, in pasteurised milk products 14 Mycotoxins, presence in cheese 73 survival in fermented milks 88 Natamycin, as antifungal agent in packaging of cheese 68 Natural antimicrobial factors, in bovine milk 2-3 NFMS, as ingredients in ice cream 95 Nisin, use in cheese production to prevent late blowing 69 NIZO process, in production of ripened cream butter 51 Nordic sour milk, production of 78 Off-flavours, caused by Gram-negative psychrotrophs in processed milk 9 Osmophilic yeasts, in spoilage of sweetened condensed milk 29 Packaging, of butter 52 of dairy spreads 54 of ice cream 99 of processed cream 41 of processed milk 8 of yoghurt 84
Partial coagulation, caused by Gram-negative psychrotrophs in processed milk 9 Pasteurisation, of cheese 63 of dairy spreads 54 of raw milk 5-6 time-temperature requirements 5 Pasteurised cream 38 Pasteurised milk products 10-1 microbiological spoilage 8-9 Pathogen profiles 145-61 Pathogens, growth and survival in butter and dairy spreads 56-7 growth and survival in cheese 69-74 growth and survival in cream 43-6 growth and survival in dried and concentrated milks 30-3 growth and survival in fermented milks 86-9 growth and survival in ice cream 101 growth and survival in milk 10-5 Penicillium, in spoilage of butter 55 in spoilage of cheese 68 in spoilage of cream 43 in spoilage of dairy spreads 55 in spoilage of yoghurt 86 Penicillium frequentans, as contaminant in yoghurt 89 Pichia, as contaminant in ice cream 96 in spoilage of cheese 68 in spoilage of yoghurt 85 Plate-heat exchangers, use in pasteurisation of milk 5 Poliovirus, survival in unpasteurised cheese 73 Polyoxethylene glycol, as emulsifier in ice cream 97 Post-process contamination, in ice cream 102 in milk 9 Probiotic cultures, in fermented products 89 Probiotic fermentation, of milks 79-80 Probiotic products, in production of yoghurt 84-5 Process hygiene criteria, EU legislation 136-9 Processed cheeses, 67 Processed milk, filling and packaging 8 Processing, effects on microflora of bovine milk 3-7 effects on microflora of concentrated and dried milk 22-3 of butter and dairy spreads 50-3 of cheese 62-7 of cream 38 of fermented milk 81-4 Propionibacterium spp., causing discolouration in cheese 69 Proteus, in spoilage of cream 43 Pseudomonads, in pasteurised cream 43 in spoilage of cheese 68
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DAIRY PRODUCTS in spoilage of condensed milk 28 in spoilage of processed milk 9 in spoilage of UHT processed milk 10 in stored raw milk 3 Pseudomonas fluorescens, in spoilage of butter 55 in spoilage of cheese 68 Pseudomonas fragi, in spoilage of butter 55 in spoilage of cheese 68 source of contamination in ice cream 95 Pseudomonas nigrificans, in spoilage of butter 55 Pseudomonas putida, in spoilage of cheese 68 Pseudomonas putrefaciens, in spoilage of butter 55 Pseudomonas spp., in spoilage of cheese 68 Pseudomonas spp., psychrotrophic – in spoilage of cream 38 Psychrotrophic bacteria, growth during storage of raw milk 3 Pulsed-electric field, in processing of milk 7 Registration of food business operators, EU legislation 125 Rennet, in cheese production 66 Rhizopus, in spoilage of butter 55 in spoilage of yoghurt 86 Rhodotorula, in spoilage of butter 55 in spoilage of yoghurt 85 Ripened cream butter 51-4 Ripening, of cheese 66-7 Ropiness, caused by Gram-negative psychrotrophs in processed milk 9 Saccharomyces, in spoilage of yoghurt 85 Salmonella, in cheese 63 in ice cream 97, 99 in pasteurised milk products 10-1 Salmonella enteritidis, as cause of foodpoisoning associated with cream 44 as cause of food poisoning associated with ice cream 101 Salmonella spp. 153-4 as contaminants in cream 44 causing spoilage in cheese 71-2 growth and survival in dried milk 31 in raw milk 10 Salmonella typhimurium DT40, as cause of food-poisoning associated with cream 44 Salmonellosis, outbreaks associated with cheese 69, 72 outbreaks associated with cream 44 outbreaks associated with dried milk 31 outbreaks associated with pasteurised milk products, 10-1 Salting, in production of butter 52 in production of cheese 66 Semi-soft/semi-hard cheese, definition 61 Separation, in processing of raw milk 5
in production of cream 39-40 Sherbet, definition 93 Shewanella putrefaciens, in spoilage of butter 55 Shigella spp., cause of illness associated with cheese 73 Skimmed milk powder, production of (Fig.) 28 Soft cheese, definition 61 Soft-serve ice cream 100 Sorbets, definition 93 Sorbic acid, as antifungal agent in packaging of cheese 68 Sorbitol esters, as emulsifiers in ice cream 97 Splits, definition 94 Spoilage, of butter and dairy spreads 55-6 of cheese 67-9 of cream 42-3 of dried and concentrated milk 28-30 of fermented milks 85-6 of ice cream 100-1 of processed milk 8-9 of sweetened condensed milk 29 Spray-drying, of milk 26-7 Stabilisation, of evaporated milk 25 Stabilisers, in ice cream 96-7 Staphylococcal food poisoning, outbreaks associated with butter 56 Staphylococcus, presence in cheese 63 Staphylococcus aureus, as post-process contaminant in cream 45 as post-process contaminant in ice cream 102 causing outbreaks of food poisoning 13-4 growth and survival in cheese 64, 72 growth and survival in condensed/evaporated milk 30 growth and survival in dried milk 31-2 in contamination of butter 56 in dried milk – as cause of food poisoning outbreaks 31-2 in pasteurised milk products 13-4 pathogen profile 154-6 survival in fermented milks 87-8 Staphylococcus intermedius, cause of foodpoisoning outbreak associated with butter 57 Starter cultures, in production of cheese 63-5 Starter failure, in cheese production 64 Sterilisation process, for milk 6-7 Sterilised creams 38 Sterilised milk 9-10 Stirred milk, production of (Fig) 82 Storage and transport, of raw milk 3-4, 38-9 Streptococci, survival of pasteurisation process in butter 51 Streptococcus thermophilus, as starter culture for acid buttermilk production 79
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INDEX as starter culture for cheese 63 as starter culture for yoghurt production 79, 83 as starter culture in thermophilic fermentation of milk 78-9 Sugars, as ingredients in ice cream 96 Susa, fermented dairy product 78 Sweet curdling, caused by Bacillus cereus in cream 42 caused by Bacillus cereus in milk 8 Sweetened condensed milk 21 processing of 24-5 spoilage of 29 Temperature control, importance in transport and storage of raw milk 3 Therapeutic fermentation, of milks 79-80 Thermisation, in processing of cheese 63 in processing of raw milk 4 Thermoduric organisms, in spoilage of creambased desserts 43 in spoilage of milk 8 survival of pasteurisation 6 Thermophilic fermentation, of milk 78-9 Torula, as contaminant in ice cream 96 Torula cremoris, in spoilage of cream 43 Torulopsis, in spoilage of butter 55 in spoilage of sweetened condensed milk 29 in spoilage of yoghurt 85 Torulopsis sphaerica, in spoilage of cream 43 Toxins, in pasteurised milk products 15 Transport and storage, of raw milk 3-4, 38-9 Trichoderma harzianum, in spoilage of dairy spreads 55 Tyramine, presence in cheese 74 UHT milk 9-10 UHT process, for milk 6-7 in ice cream production 98 UHT sterilisation processes, in production of cream 41 Ultra-high-pressure homogenisation, in processing of milk 7 Ultra-high-temperature creams 38 Ultra-sound treatment, in processing of milk 7 Untreated cream 38 Vacuum packaging, of cheese to prevent mould growth 68 Value-added cheese 67 Verotoxigenic Escherichia coli (VTEC), causing outbreaks of food poisoning 12 growth and survival in cream 46 in cheese 63 in ice cream 102 in pasteurised milk products 12-3 Villi, production of 81 Viral hepatitis, infection associated with dairy products 46
Viruses, in pasteurised milk products 14-5 VTEC, see Verotoxigenic Escherichia coli Water ices, definition 93 Whipped cream, processing of 41-2 Whipping (whipped) cream, definition 37 Whole milk, fresh – as ingredient of ice cream 95 Working, in production of butter 52 in production of dairy spreads 54 Xanthan, as stabiliser in ice cream 97 Xerophilic moulds, source of contamination in ice cream 97 Yakult, production 79 Yarrowia lipolytica, in spoilage of cheese 68 in spoilage of dairy spreads 55-6 Yeast, as indicator of post-process contamination of milk 9 causing discolouration in cheese 69 in ice cream 97 in spoilage of butter 55 in spoilage of fermented milks 85-6 Yeast-lactic fermentations, of milk 80 Yersinia enterocolitica, causing outbreaks of food poisoning 12 growth in dairy spreads 57 in pasteurised cream 45 in pasteurised milk products 13 pathogen profile 156-7 Yersinia spp., survival in fermented milks 88 Ymer, as type of buttermilk 78 Yoghurt 79 cooling and packing 84 frozen, definition 94 Zygosaccharomyces, as contaminant in ice cream 96
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