Table of Contents
About the Editors xi
List of Contributors xiii
Foreword xv
Preface to the Technical Series xvii
Preface xix
Acknowledgements xxi
1 Introduction to Biofilms: Definition and Basic Concepts 1
1.1 Definition of biofilms 1
1.2 Importance of biofilms in the dairy industry 2
1.3 Biofilm formation 3
1.4 Biofilm structure 5
1.5 Composition of the EPS 6
1.6 Composition of the biofilm population 7
1.7 Enhanced resistance of cells within biofilms 9
1.8 Controlling biofilms 10
1.9 Emerging strategies for biofilm control 11
1.10 Conclusion 12
References 12
2 Significance of Bacterial Attachment: A Focus on the Food Industry 17
2.1 Introduction: The importance of bacterial attachment in biofilm development 17
2.2 Conditioning films and bacterial footprints: The importance of conditioning films and bacterial footprints in cell attachment 17
2.3 Bacterial outer surface and attachment 19
2.3.1 Role of surface charge in relation to the abiotic surface and bacterial cell 19
2.3.2 Hydrophobic interactions 20
2.3.3 Role of carbohydrates in attachment 21
2.3.4 Teichoic acids, eDNA and cell attachment: Are we missing something? 22
2.4 Role of the abiotic surface in attachment 23
2.4.1 Are all abiotic surfaces created even? 23
2.4.2 Surface modification and ion impregnation of stainless steel to reduce cell attachment 25
2.4.3 Surface roughness and microtopography 25
2.5 Staphylococcus and attachment, an example: Surface proteins implicated in cell attachment to abiotic surfaces 27
References 29
3 The Effect of Milk Composition on the Development of Biofilms 36
3.1 Introduction 36
3.2 Milk composition 37
3.3 Influence of organic molecules (protein and lipid) on the development of biofilms in the dairy industry 38
3.4 Protein and lipid molecules reduce attachment of bacteria to surfaces 38
3.5 Effect of ions on the development of biofilms of thermophilic bacilli 40
3.6 Conclusion 46
References 46
4 Overview of the Problems Resulting from Biofilm Contamination in the Dairy Industry 49
4.1 Introduction 49
4.2 Microbiological flora associated with dairy manufacturing 49
4.2.1 Psychrotrophs 49
4.2.2 Mesophiles 50
4.2.3 Thermodurics 50
4.2.4 Thermophiles 51
4.3 Effects of biofilms on food safety 51
4.3.1 Bacillus cereus 51
4.3.2 Listeria monocytogenes 52
4.3.3 Cronobacter sakazakii 53
4.4 Effects of biofilms on spoilage 53
4.5 Effects of biofilms on processing efficiency 55
4.5.1 Effects of fouling and biofilms on heat transfer and flow rates 56
4.5.2 Cleaning 57
4.5.3 Corrosion 58
4.6 Conclusion 59
References 60
5 Raw Milk Quality Influenced by Biofilms and the Effect of Biofilm Growth on Dairy Product Quality 65
5.1 Introduction 65
5.2 Composition of raw milk 66
5.3 Measurement of raw milk quality 66
5.4 Regulations and guidelines for the production of raw milk 67
5.4.1 In Europe 67
5.4.2 In the United States 68
5.4.3 In New Zealand 68
5.5 Microbial profile of raw milk and its effect on the dairy industry 69
5.5.1 Spoilage microorganisms in raw milk 70
5.5.2 Foodborne pathogens 76
5.5.3 Beneficial bacteria 80
5.6 Biofilms at dairy farms 82
5.6.1 General characteristics of biofilms 82
5.6.2 Cows 82
5.6.3 Milking equipment and raw milk storage tanks 83
5.6.4 Raw milk tanker 84
5.7 Conclusion 85
References 86
6 Thermoresistant Streptococci 99
6.1 Characteristics of Streptococcus thermophilus and S. macedonicus 99
6.2 Biofilms of thermoresistant streptococci in dairy manufacturing equipment 99
6.3 Attachment of thermoresistant streptococci to surfaces 101
6.4 The role of cell surface proteins in attachment of thermoresistant streptococci 103
6.5 Biofilm growth 104
6.6 Strategies to control thermoresistant streptococci 105
6.6.1 Influence of heat 105
6.6.2 Influence of cleaning and sanitation 107
6.7 Conclusion 109
References 109
7 Thermophilic SporeÂ]Forming Bacilli in the Dairy Industry 112
7.1 Introduction 112
7.2 Thermophilic sporeÂ]forming bacilli of importance to the dairy industry 112
7.2.1 Geobacillus 113
7.2.2 Anoxybacillus flavithermus 114
7.2.3 Bacillus licheniformis 114
7.3 Spoilage by thermophilic bacilli 114
7.4 Bacterial endospores 115
7.4.1 Spore structure and resistance 115
7.4.2 Sporulation 117
7.4.3 Germination 117
7.5 Enumeration of thermophilic bacilli 118
7.5.1 Viable plate counts 119
7.5.2 Rapid methods 119
7.6 Characterisation and identification of thermophilic bacilli 120
7.6.1 MolecularÂ]based typing methods 121
7.7 Biofilm formation by thermophilic bacilli 122
7.7.1 Attachment of cells and spores to surfaces 122
7.7.2 Biofilm development 123
7.7.3 Spore development within biofilms 125
7.8 Thermophilic bacilli in dairy manufacturing 125
7.8.1 Thermophilic bacilli in raw milk 125
7.8.2 Milk powder manufacturing 125
7.8.3 Thermophilic bacilli in other dairy processes 126
7.9 Control of thermophilic bacilli 127
7.9.1 CleaningÂ]inÂ]place 127
7.9.2 Other control methods 128
References 129
8 Biofilm Contamination of Ultrafiltration and Reverse Osmosis Plants 138
8.1 Introduction 138
8.2 Ultrafiltration and reverse osmosis membranes 139
8.3 Membrane configuration and materials 140
8.4 Crossflow and biofouling 140
8.5 Biofilm development 141
8.5.1 Membrane surface characteristics and biofilm formation 141
8.5.2 Other factors 143
8.6 Biofilm structure 144
8.6.1 Models and bioreactors for biofilm study 144
8.7 Investigation of persistent biofilms on UF membranes 145
8.7.1 Attachment of Klebsiella isolates to UF membranes 146
8.7.2 Removal of Klebsiella biofilms from membranes 148
8.8 Other isolates from WPCs 148
8.9 Conclusion 149
References 150
9 Pathogen Contamination in Dairy Manufacturing Environments 154
9.1 Introduction 154
9.2 Pathogenic bacteria 155
9.2.1 Cronobacter species (formerly Enterobacter sakazakii) 155
9.2.2 Escherichia coli 158
9.2.3 Salmonella species 160
9.2.4 Campylobacter jejuni 162
9.2.5 Bacillus cereus 164
9.2.6 Listeria monocytogenes 167
9.2.7 Staphylococcus 169
9.3 Yeasts and moulds 170
9.4 Preventing contamination of dairy products by pathogenic microorganisms 171
9.4.1 Pathogenic bacteria in raw milk 171
9.4.2 Prevention of contamination at the dairy manufacturing plant 171
References 177
10 Biofilm Issues in Dairy Waste Effluents 189
10.1 Introduction 189
10.2 Overview of dairy effluent treatment 190
10.3 Dairy farm waste treatment 192
10.4 Composition of biofilms 193
10.5 Application of biofilms in dairy wastewater treatment 195
10.6 Irrigation systems 196
10.7 Controlling biofilms in waste treatment systems 198
10.8 Conclusion 199
References 200
11 Biofilm Modelling 203
11.1 Introduction 203
11.2 What is a model? 203
11.3 Why construct a model? 204
11.4 Types of model available 205
11.4.1 Probabilistic models 205
11.4.2 Kinetic models 205
11.4.3 Analytical models 206
11.4.4 Numerical models 207
11.5 Modelling dairy biofilms 208
11.6 Example of biofilm modelling 209
11.6.1 Model laboratory system 210
11.6.2 Pipe model 210
11.6.3 Reactor model 219
11.7 Conclusion 226
References 227
12 Biofilm Control in Dairy Manufacturing Plants 229
12.1 Introduction 229
12.2 Factors that influence growth and survival of bacteria in biofilms 229
12.2.1 Temperature 229
12.2.2 Surface materials 232
12.2.3 Nutrients 232
12.2.4 Water 232
12.2.5 Time 233
12.2.6 Cleaning and sanitation 233
12.2.7 Interactions between bacteria in biofilms 234
12.3 Controlling biofilm development in dairy processing equipment 235
12.3.1 Controlling biofilms with standard cleaning practices 235
12.3.2 Changing equipment design 241
12.4 Controlling biofilm development on environmental surfaces 243
12.4.1 Standard cleaning and sanitation practices 243
12.4.2 Moisture 245
12.4.3 Interactions with other microorganisms 246
12.5 Conclusion 247
References 248
Index 252
