Food Hygiene, Microbiology and HACCP Food Hygiene, Microbiology and HACCP Third Edition

Food Hygiene, Microbiology and HACCP Food Hygiene, Microbiology and HACCP Third edition

S.J. FORSYTHE Department of Life Sciences, The Nottingham Trent University, Nottingham, UK and P.R. HAYES formerly of Department of Microbiology, The University of Leeds, Leeds, UK

Springer Science+Business Media, LLC 1998 The author has made every effort to ensure the accuracy of the lnformation hereln. However, appropriate informatlon sources should be consulted, especlally for new or unfamiliar procedures. It ls the responslbility of every practltioner to evaluate the appropriateness of a particular oplnlon in In the context of actual clinica! situations and with due conslderatlons to new developments. The author, editors, and the publisher cannot be held responslble for any typographical or other errors found in thls book.

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ISBN 978-1-4419-5196-0 ISBN 978-1-4757-5254-0 (eBook) DOI 10.1007/978-1-4757-5254-0

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Editorial Services: Ruth Bloom Llbrary of Congress Catalog Card Number:98-071771 ISBN 978-1-4419-5196-0

2 3 4 5 Contents

Preface to the Third Edition xii

Preface to the Second Edition xiv

Preface to the First Edition xvi

1 Fundamental Principles of Microbiology 1 l.l Introduction 1 1.2 Characterisitics of Bacteria 2 1.2.1 Shape and size 2 1.2.2 Reproduction 2 1.2.3 Bacterial structure 2 1.2.4 Gram reaction 3 1.3 Types of Bacteria Important in Foods 4 1.3.1 Gram negative bacteria 4 1.3.2 Gram positive bacteria 7 1.4 Characteristics of Fungi 8 1.4.1 Moulds 8 1.4.2 Yeasts 11 1.5 Characteristics of Viruses and Prions 11 1.6 The Growth Curve of Bacteria 14 1. 7 Factors Influencing Bacterial Growth 15 1.7.1 Nutrients 15 1.7.2 Temperature 16 1. 7.3 Moisture 17 1. 7.4 Oxygen 18 1.7.5 Hydrogen ion concentration (PH) 19 1. 7.6 Inhibitory substances 20 Bibliography 20 References 20

2 Food Poisoning and Other Food-borne Hazards 21 2.1 Introduction 21 2.2 Incidence of Food Poisoning 21 2.2.1 The bacteria responsible 23 2.2.2 Type of food 23 2.3 Bacterial Food Poisoning 24 2.3.1 Salmonellas 24 2.3.2 Enteritis due to Campylobacter spp 32 2.3.3 Staphylococcus aureus 36 2.3.4 Bacillus cereus 39 2.3.5 Vibrio parahaemolyticus 42 2.3.6 Botulism 44 2.3.7 Listeriosis 49 2.3.8 Clostridium perfringens 54 2.3.9 Escherichia coli 57 2.3.10 Miscellaneous bacterial food poisoning and new variant cm 59 VI CONTENTS

2.4 Mycotoxicoses 63 2.4.1 Aflatoxins 64 2.4.2 Miscellaneous mycotoxins 67 2.5 Virus Food Poisoning 68 2.5.1 Small round structured viruses (SRSV) 69 2.5.2 Infective hepatitis 69 2.5.3 Rotaviruses 69 2.5.4 Bovine spongifonn encephalopathy and new variant cm 70 2.5.5 General control measures 70 2.6 Animal Toxins and Parasitic Infections 70 2.6.1 Animals that are naturally toxic to man 70 2.6.2 Secondary toxicity 71 2.6.3 Parasitic infections 73 2.7 Poisonous Plants 76 2.8 Chemical Poisoning 77 Bibliography 79 References 79

3 Food Spoilage 86 3.1 Introduction 86 3.2 Spoilage of Fresh Meats 87 3.2.1 Contamination of tissues by microorganisms 87 3.2.2 Control of microbial growth 88 3.2.3 Effect of storage temperature 90 3.2.4 Chemical changes produced by bacteria in chilled meats 93 3.3 Spoilage of Cured Meats 94 3.3.1 Curing agents 94 3.3.2 The curing process 95 3.3.3 The microbiology and spoilage of bacon and ham 95 3.4 Spoilage of Vacuum-Packed Meats 98 3.4.1 Types of packaging materials 98 3.4.2 Influence of packaging materials on the microbiological flora 98 3.4.3 Spoilage of packed fresh meats 99 3.4.4 Spoilage of vacuum-packed bacon 101 3.4.5 Modified atmospheric packaging 102 3.4.6 Sous vide 103 3.5 Spoilage of Poultry 103 3.5.1 Effects of processing on the microbiological flora 103 3.5.2 Spoilage of chickens held at chill temperatures 105 3.6 Spoilage of Fish and Shellfish 106 3.6.1 Bacteriology of the newly caught fish 106 3.6.2 The effect of initial processing and storage in ice on board ship 106 3.6.3 The effect of handling ashore 108 3.6.4 Chemical changes induced by bacteria in fish 108 3.6.5 Salted fish 109 3.6.6 Smoked fish 110 3.6.7 Packaged fish III 3.6.8 Shellfish III 3.7 Dairy Products 112 3.7.1 Milk 112 3.7.2 Butter 115 3.7.3 Cheese 116 3.7.4 Yoghurt 117 3.8 Eggs and Egg Products 118 3.8.1 The chicken's egg and its spoilage 118 3.8.2 Egg products 119 3.9 Vegetables and Fruits 120 3.9.1 Spoilage by fungi 120 CONTENTS VB

3.9.2 Spoilage by bacteria 121 3.9.3 Control of microbial spoilage 122 3.10 Cereal Based Products 123 3.11 Beer 124 3.12 Wine 125 3.13 Sauerkraut 125 3.14 Canned Foods 125 3.14.1 Leaker spoilage 126 3.14.2 Spoilage due to inadequate heat treatment 129 3.15 Frozen Foods 133 3.15.1 Influence of sub-zero temperatures on microorganisms 133 3.15.2 Factors affecting viability of microorganisms during freezing 133 3.15.3 Effect of cold storage 134 3.15.4 Freezing injury to cells 135 3.15.5 Thawed foods and their spoilage 135 3.16 Dehydrated Foods 136 3.16.1 Methods of drying 136 3.16.2 Influence of drying and freeze drying on microorganisms 137 3.16.3 Storage stability of dried foods 137 3.16.4 Rehydration 138 3.16.5 Intermediate moisture foods 138 3.17 Irradiated Foods 138 3.17.1 Types of radiation 138 3.17.2 Effect of radiation on microorganisms 139 3.17.3 High dose applicatons 140 3.17.4 Low dose applications and the spoilage of foods so treated 141 Bibliography 143 References 143

4 Microbiological Examining Methods 150 4.1 The Rational of Microbiological Testing 150 4.2 Sampling 150 4.2.1 Sampling plan 150 4.2.2 The representative sample 151 4.2.3 Sampling techniques 153 4.2.4 Treatment of sample 154 4.2.5 Examination methods 154 4.3 Microbiological Test Procedures 156 4.3.1 Total viable count 156 4.3.2 Viable but nonculturable bacteria 158 4.4 Conventional Methods 158 4.4.1 Indicator organisms 158 4.4.2 Food poisoning bacteria 161 4.4.3 Food spoilage organisms 168 4.4.4 Canned foods 170 4.4.5 Frozen and dehydrated food 171 4.5 Rapid Detection Techniques 171 4.5.1 Separation and concentration techniques 172 4.5.2 Impedance microbiology 177 4.5.3 Enzyme immunoassays and latex agglutination tests 180 4.5.4 Nucleic acid probes and PCR 182 4.5.5 ATP bioluminescence techniques and hygiene monitoring 185 4.5.6 Lux gene technology 188 4.5.7 Flow cytometry 189 4.5.8 Miscellaneous tests 190 4.6 Microbiological Criteria and Specifications 190 Bibliography 191 References 192 Vlll CONTENTS

5 Factory Design and Construction 203 5.1 The Factory Site 203 5.2 General Design Principles and Structural Techniques 204 5.2.1 Roofing and lighting 205 5.3 Construction of Ceilings, Walls and Floors 207 5.3.1 Ceilings and overhead fittings 207 5.3.2 Walls 208 5.3.3 Floors and drains 210 5.4 Ventilation and Air Conditioning 211 5.5 Noise and Vibration 214 Bibliography 214

6 Factory Layout 215 6.1 Handling of Food Materials 215 6.1.1 Work flow patterns and plant layout 216 6.2 Layout and Integration of Different Work Areas 217 6.2.1 Raw materials: reception 217 6.2.2 Raw materials: storage 218 6.2.3 Processing area 220 6.2.4 Finished product storage 221 6.2.5 Employee service and welfare areas 221 6.2.6 Offices and general administration buildings 227 6.2.7 Laboratories 227 6.2.8 Machine maintenance and storage areas 228 6.2.9 Integration of the principal areas of work 228 Bibliography 231 Reference 231

7 Design of Food Processing Equipment 232 7.1 Introduction 232 7.2 Legislation 233 7.3 Construction Materials 236 7.3.1 General requirements 236 7.3.2 Stainless steel 237 7.3.3 Corrosion of stainless steel 237 7.3.4 Iron and mild steel 238 7.3.5 Copper and its alloys 238 7.3.6 Miscellaneous metals 239 7.3.7 Plastics 239 7.3.8 Rubber, glass and wood 240 7.3.9 Antimicrobial worksurfaces 241 7.4 Growth 'Pockets' 241 7.5 Ease of Dismantling and Re-assembly of Equipment 243 7.6 Accessibility and the Supporting Framework 244 7.7 External Surfaces 245 7.8 Design Features for Individual Items of Equipment 246 7.8.1 Tanks, vats, etc 246 7.8.2 Pumps 249 7.8.3 Valves 250 7.8.4 Pipes 256 7.8.5 Steam and air lines 259 7.8.6 Motors 259 7.8.7 Size reduction equipment 261 7.8.8 Mixers 262 7.8.9 Forming and assembly equipment 263 CONTENTS IX

7.8.10 Mechanical separators 263 7.8.11 Equipment transferring solid foods 264 7.8.12 Heating equipment 269 7.8.13 Safety 273 Bibliography 274 References 274

8 HACCP and Product Quality 276 8.1 HACCP and Quality Schemes 276 8.2 Origins of HACCP 277 8.3 Objectives of HACCP 277 8.4 The Seven Principles of HACCP 278 8.4.1 Principle 1 279 8.4.2 Principle 2 279 8.4.3 Principle 3 279 8.4.4 Principle 4 279 8.4.5 Principle 5 280 8.4.6 Principle 6 281 8.4.7 Principle 7 281 8.5 HACCP-like Implementation 281 8.6 Generic HACCP 281 8.6.1 CCP for refrigerated foods 282 8.6.2 CCP for whole young chickens 282 8.7 Principle I - Hazard Analysis 282 8.7.1 Microbial hazards 284 8.7.2 Extrinsic parameters 287 8.8 Principle 2 - Critical Control Points 290 8.8.1 The CCP decision tree 290 8.8.2 Trends in CCP implementation 291 8.9 Critical Limits 292 8.9.1 Critical liruits during a cooking process 292 8.10 ATP-bioluruinescence and HACCP Monitoring 294 8.11 End-product Testing and Microbiological Criteria 294 8.11.1 Verification 294 8.11.2 Record keeping 295 8.11.3 Dairy industry 295 8.11.4 Meat industry 296 8.11.5 Seafoods industry 297 8.11.6 Catering, cooked-chilled foods, sous-vide 298 8.12 Problems of Implementation 300 8.13 HACCP and Predictive Microbiology 302 8.14 Risk Assessment 304 8.15 Quality Assurance and Quality Control 304 8.16 Raw Material Control 307 8.16.1 Inspection 307 8.16.2 Ambient temperature storage 307 8.16.3 Chill storage 308 8.16.4 Deep frozen storage 309 8.16.5 Storage zones 309 8.17 Process Control 309 8.17.1 Process temperature/time relationships 310 8.17.2 Design of and critical points in pork pie processing 312 8.17.3 Waste materials 314 8.17.4 Maintenance of processing lines 315 8.18 Packaging 315 8.18.1 Required properties of packaging materials 315 8.18.2 Main types of packaging materials and containers 316 x CONTENTS

8.18.3 Microbiological aspects of packaging materials 316 8.18.4 Storage of packaging materials 317 8.19 Finished Product Storage 317 8.20 Transport and Distribution 318 8.21 Total Quality Management and Longitudinal Integrated Safety Assurance 320 Bibliography 321 References 322

9 Cleaning and Disinfection: Methods 327 9.1 Introduction 327 9.2 Definitions 327 9.3 Types of Soil 328 9.4 Removal of Gross Soil 329 9.5 Detergents 330 9.5.1 Desirable properties 330 9.5.2 Classifications of detergents 331 9.5.3 Detergent formulation 338 9.5.4 Factors affecting efficiency of detergents 339 9.6 Chemical Disinfectants 340 9.6.1 Desirable properties 340 9.6.2 Classification of disinfectants 341 9.6.3 Evaluation of disinfectants 347 9.7 Use of Heat 352 9.7.1 Steam 352 9.7.2 Hot water 352 9.8 Dry Cleaning 353 9.9 Cleaning-in-Place (CIP) 353 9.9.1 CIP systems 353 9.9.2 Spraying devices 354 9.9.3 Benefits of CIP 357 9.10 Mechanical Aids for Cleaning 357 9.10.1 Pressurized steam 357 9.10.2 Hydraulic devices 358 9.10.3 Compressed air 358 9.10.4 Ultrasonics 358 9.10.5 Portable cleaning machines 359 9.10.6 Fixed cleaning systems 360 9.11 Foam Cleaning 360 9.12 Cleaning Small Equipment 360 9.13 Paper and Fabric Wipers 362 Bibliography 362 References 362

10 Cleaning and Disinfection: Practical Application 364 10.1 Aims 364 10.2 Cleaning Schedules 365 10.3 Biofilms 366 10.4 Use of Labour 366 10.5 The Role of Management 368 10.6 Miscellaneous Problems Encountered 369 10.7 Assessment of Cleaning Efficiency 370 Bibliography 371 References 371 CONTENTS Xl

11 Hygiene and Training of Personnel 372 11.1 Hand Washing and Care of the Hands 372 11.1.1 Personal hygiene 373 11.1.2 Bactericidal soaps and creams 373 11.1.3 Use of gloves 374 11.2 Practices, Good and Bad 374 11.2.1 Clothing and jewellery 375 11.2.2 Hair 375 11.2.3 Other bad practices 375 11.3 Health Supervision 376 11.3.1 Pre-employment medical examination 376 11.3.2 Health monitoring of employees 376 11.4 Induction and In-Service Training 377 Bibliography 379 References 379

12 World-wide Food Safety Programmes and Legislation 380 12.1 World-wide Food Safety Programmes 380 12.1.1 World-wide food poisoning outbreaks 380 12.1.2 Salm-Net 382 12.1.3 Antibiotic resistance 383 12.2 Legislation 384 12.3 Food Legislation Within the European Community 385 12.3.1 The legislative process 385 12.3.2 Microbiological criteria for foods 386 12.3.3 Examples of EC food legislation 388 12.4 International Food Standards 403 12.4.1 International implementation of HACCP concept 404 12.5 Food Hygiene and Safety Legislation in the UK 405 12.5.1 The Food Safety Act (1990) 405 12.5.2 Codes of Practice 406 12.5.3 Food Safety (General Food Hygiene) 1995 406 12.5.4 Food Safety (Temperature)Regulations 1995 408 12.5.5 Dairy Products (Hygiene) Regulations 1995 410 12.5.6 Food Standards Agency 410 12.5.7 Ice-Cream (Heat Treatment) Regulations (1959); Liquid Egg (Pasteurization) Regulations (1963) 411 12.6 Food Legislation In Some European Countries 412 12.6.1 France 412 12.6.2 Italy 413 12.6.3 Germany 415 12.6.4 Netherlands 417 12.6.5 Food Hygiene Directive (93/43/EEC) implementation 418 12.7 Food Legislation in the USA 418 12.7.1 The GMP regulations 420 12.7.2 Regulations concerning specific foods 421 12.7.3 Microbiological standards in the USA 426 12.8 Food Legislation in Japan and Korea 427 12.8.1 Microbiological Standards in Japan and Korea 428 12.9 Concluding Remarks 428 Bibliography 430 References 430 Index 434 Preface to the third edition

Food microbiology is a fascinating and challenging science. It is also very demanding with a constantly changing sea of guidelines, regulations and equip• ment. Public concerns over food safety issues can overemphasize certain risks and detract from the normal hygienic practice of food manufacturers. This new edition aims to update anyone concerned with the hygienic production of food on key issues of HACCP, food microbiology and the methods of microbe detection. I have taken a 'crystal ball' approach to certain topics. The use of rapid techniques such as lux gene technology and polymerase chain reaction (DNA probes) are progressing so rapidly in the research laboratory that when this book is in print the techniques may be more readily available. New methods for investigating viral gastroenteritis due to small round structured viruses (SRSV) have been developed past the 'research' stage and may become more standard in the next few years. Undoubtedly this will alter our understanding of the prevalence of viral food poisoning. I have also included issues such as new variant CJD (associated with BSE infected cattle) which at the time of writing has only caused the deaths of 20 people, but due to the uncertain incubation time could be a far more serious problem. In the UK there has been a much publicised outbreak of Escherichia coli 0157:H7 which has resulted in a government inquiry and the recommenda• tion of the generic HACCP approach. Hence this approach to HACCP imple• mentation has been included. HACCP is a much talked about approach to hygienic food production but its implementation, especially in small businesses can be difficult. This book does not attempt to teach 'how to HACCP', there is a plethora of books purporting to do that already on the market. However it aims to give a more complete background and world-wide perspective on the issue. Although we have known about Salmonella as a food poisoning organism for a hundred years now it is still (alongside Campylobacter) a prevalent cause of food-borne illness. We do not wish to live in a society solely sustained by sterilized food hence hygienic manufacturing practice (combined with hygienic practice in the home) is a prerequisite for a healthy population. The change in book title from the two previous editions is designed to reflect the change in emphasis of topics.

Additional acknowledgements for the third edition I would like to thank Chapman and Hall for their invitation to update the already well-received book by Pat Hayes. The more I studied the book the more I became wary of touching another person's exhaustive workmanship; therefore PREFACE TO THE THIRD EDITION xiii any errors and omissions are my responsibility. My thanks to Pat for his patience with me and advice. Numerous people have assisted in collecting the new material and given advice; Prof. D.A.A. Mossel (Delft University), Judi Lee (New Zealand Ministry of Agriculture), Anna Mathers (Weetabix Ltd) and Dr Jong-Hyun Park (Korean Food Research Institute). A number of companies have supplied new photos for this edition: Biotrace Ltd Don Whitley Scientific Ltd Dynal AS, Oslo Thanks are due to my wife Debbie for her unfailing support and also James and Rachel, the next generation. S. J. Forsythe Preface to the second edition

The aims of this book remain the same, that is, that it should be of interest to all those people concerned with, or about, food hygiene in the broadest sense. There was clearly a need for a book of this sort and its success has necessitated a second edition. It will, I hope, answer criticisms that were justifiably made about certain omissions and shortcomings levelled at the earlier edition. The whole book has been thoroughly revised with the introduction of several new sections to various chapters. During the time that has elapsed since the earlier edition appeared there has been much publicity about newer forms of 'food poisoning'. Thus listeriosis is discussed in some detail whilst the problems of salmonellas in eggs and BSE are also considered. Interest in irradiated foods has waxed and waned but it is rightly included in the relevant chapter. There has been much progress in methodology with the advent of advanced molecular techniques such as gene probes and that of PCR; these are discussed briefly. I have included sections on HACCP which has come into great prominence in recent years thus answering a specific criticism made of the earlier edition. The chapter on water and waste disposal contains material on Legionnaires' disease and cryptosporidiosis, infections of much concern at the present time. Finally, the chapter on legislation has undergone a major revision with far greater emphasis being placed on EC food hygiene legislation. I have again received much help from experts in their field whom I acknowl• edge here; without them this book could not have been written. Finally, I reiterate that I take full responsibility, as before, for any errors or omISSIOns.

Additional acknowledgements for the second edition I should again like to acknowledge the invaluable help given to me by many individuals and organisations. I wish to express my gratitude to: Miss Dorothy Flowerdew and her colleagues at the Leatherhead Food Research Association for once again supplying vital information and advice on national food legislation and microbiological standards on those countries included in this book; Professor L. Wassermann, Ulmer Spatz, Neu-Ulm, Germany, for further help on German food legislation; David Timper• ley, Campden Food and Drink Research Association, for again devoting so much time in advising me on the intricacies of food equipment design; Dr Tony Baird• Parker, Unilever, for help on HACCP; and Dr Richard Gilbert, Public Health Laboratory Service, for supplying me with food poisoning statistics. PREFACE TO THE SECOND EDITION xv

It is a pleasure to be able to thank the companies and research establishments listed below for helpful discussions and/or supplying new photographic material or drawings: APV, Crawley, West Sussex Campden Food and Drink Research Association, Chipping Campden, Gloucestershire Fristam (Pumps) Ltd, Harrow, Middlesex KEW Industry Ltd, Penrith, Cumbria Northern Foods pIc, Nottingham Rotowash UK Ltd, Isleworth, Middlesex Don Whitley Scientific Ltd, Shipley, West Yorkshire I am indebted to the following publishers and authors for permission to produce extracts, tables or figures from their works: Academic Press for material from Journal of Infection (author, Barbara A. Bannister); Blackwell Scientific Publications, Microorganisms in Foods - Vol. 4; Butterworth-Heinemann, Safe Processing ofFood (D. A. Shapton and N. F. Shapton), and Food Control (A. C. Baird-Parker); Cambridge University Press, Epidemiology and Infection, 103, 425-33 (A. Stevens et al.); Institution of Water and Environmental Management for Water, Pollution Control (M. Shore et al.), and the Public Health Laboratory Service for data from PHLS Reports. Thanks are also due to my departmental colleagues including Kevin Kerr, Jerry Knapp and Richard Lacey who, in their different ways, made contributions to this book. Particular thanks are due to Freddie Webster, not only for her skills on the word processor, but also for her extreme patience with me over a long period of hard work. Finally, I should like to thank my wife, Rita, for her stoicism in carrying out, so conscientiously, the onerous duties of proof-reading. P. R. Hayes Preface to the first edition

Books on food hygiene and its various ramifications are scarce and when I was approached by the publishers to write this book I felt that it might answer a need. That need was for a book to be written in a language that was intelligible to all those involved in food hygiene and also, I hoped, to the layman. My interest in food hygiene goes back many years to when I worked in the food processing industry as a food bacteriologist. I realized then that so many different disciplines with their often divergent viewpoints were involved in this subject and that it was necessary to reconcile these differences to achieve the best results. This is not always as easy as it seems: engineers and micro• biologists, architects and chemists, production managers and quality controllers do not talk the same language but they must be made to where food hygiene is concerned. Being a microbiologist I must confess to some bias. I hope, however, that over the years I have been associated with the food processing industry I have come to appreciate food hygiene objectively and can make suggestions that resolve rather than exacerbate conflicting interests The first four chapters deal almost exclusively with microbiological aspects. The basic principles are presented initially so that the following three chapters dealing, respectively, with food poisoning, food spoilage and microbiological examining methods can be more readily understood by the uninitiated. The chapters following consider factory design, construction and more detailed factory layout, and the design of food processing equipment. The chapter on quality assurance and production control includes a review of critical points in selected food processes; this reflects a recurrent theme of this book, that of practicability - there are many constraints applied in the industrial world which are often not fully appreciated by the theoretician but, so often, the simple modification can be made which improves product quality. The vitally important area of cleaning and disinfection is covered next as methods and their practical application. The most sophisticated and expensive cleaning methods are vitiated if equipment design, factory layout, etc. are inadequate; these chapters are therefore linked with those preceding. The final three chapters cover the disparate subjects of waste disposal, training and legislation. The last-named topic is reviewed particularly in relation to food hygiene legislation. This clearly cannot be presented in detail but it is useful to compare the philosophies of selected countries on this topic. The book should have wide interest and is directed towards the myriads of people involved in food hygiene. Included are factory architects, builders, designers of food processing machinery, engineers, senior management in the PREFACE TO THE FIRST EDITION xvii food industry, microbiologists, hygiene officers, Environmental Health Officers, medical officers, chemists, caterers, educationalists and members of the legal profession. The material covered is diverse and this book could not have been completed without the generous help of many experts more knowledgeable than I in their particular subjects. However, I am the sole author and take full responsibility for it; any errors or omissions are entirely due to my shortcomings and should not be levelled at those acknowledged elsewhere.

Acknowledgements for the first edition It is a pleasure to acknowledge the help given to me by colleagues and other individuals, research establishments and firms during the preparation of this book. Thanks are due to my departmental colleagues for undertaking many of my duties during my absence; I should also like to note the help given by colleagues, Mr J. Lamb and Dr H. G. Muller, in the Procter Department of Food Science. I should like to thank Mr D. A. Timperley, Unilever Research, Sharnbrook, for the many helpful suggestions he made on Chapter 7; similar thanks are due to Messrs D. Littler and P. W. E. Bird, and Dr N. Hughes, Lever Industrial, Liverpool, for comments on Chapter 9; Miss D. Flowerdew and her colleagues at the British Food Manufacturing Research Association, Leatherhead, for advice on international food legislation and microbiological standards included in Chapter 13; Professor L. Wassermann, Ulmer Spatz, Neu-Ulm, Germany, for more detailed help on German food legislation; Dr R. H. G. Charles, Department of Health and Social Security, on EEC food legislation; and Mr P. Mepham, Leeds City Council, on UK food legislation. I am grateful to those companies and research establishments, listed below, that either allowed me unrestricted access into their factories or assisted me with helpful discussions, or supplied photographs or drawings: Alfa-Laval Co. Ltd, Brentford, Middlesex Alveslon Kitchens, Leamington Spa, Warwickshire APV International Ltd, Crawley, West Sussex Batchelors Foods Ltd, Sheffield, Yorkshire Birds Eye Walls Ltd, Walton-on-Thames, Surrey Campden Food Preservation Research Association, Chipping Campden, Gloucestershire Findus (UK) Ltd, Newcastle upon Tyne, Tyne and Wear A. Johnson and Co. (London) Ltd, Reading, Berkshire KEW Industry Ltd, Penrith, Cumbria Marks and Spencer pIc, London Pork Farms Ltd, Nottingham, Nottinghamshire xviii PREFACE TO THE FIRST EDITION

Joshua Tetley and Sons Ltd, Leeds, Yorkshire Toftejorg Ltd, High Wycombe, Buckinghamshire Walls Meat Co., Evesham, Warwickshire I am indebted to the many authors and publishers who allowed me to reproduce specified extracts from their works. Here I should acknowledge that: the extracts from the four DHSS Reports 'On the State of Public Health for the Years 1968,72,74 and 76' are reproduced with the permission of the Controller of Her Majesty's Stationery Office; the extract on canned foods (Put et al., 1972) is reproduced by permission of the editor of the Journal of Applied Bacteriology; and the extract from Kotschevar & Terrell's Food Service Plan• ning is reproduced by permission of John Wiley and Sons. I am also indebted to Dr R. J. Gilbert and co-authors for allowing me to reproduce material from the Journal of Hygiene, Cambridge. I wish to make a special note of the invaluable contribution made by my ex-colleague, Dr A. Neville Barker, in reading the first draft and in making the countless constructive suggestions and emendations that he did. Special thanks are also due to Mr Andrew West for preparation of the graphs and diagrams, and to Mrs Brenda Fisher for her care in typing the text. Finally, I should like to thank my wife, Rita, for her practical help in proof• reading, and for her understanding and forbearance during the difficult periods that inevitably arise when one is writing a book. P. R. Hayes