Biofilms in the Dairy Industry

Dr Koon Hoong Teh graduated from Massey University, Palmerston North, New Zealand, majoring in food technology. Steve Flint is Professor of Food Safety and Microbiology and director of the Food Division of the School of Food and Nutrition at Massey University, Palmerston North, New Zealand. John Brooks is Adjunct Professor of Food Microbiology at Auckland University of Technology, Auckland, New Zealand, and microbiology consultant at microTech Services Limited, Ashhurst, New Zealand. Geoff Knight is a food microbiologist, principal consultant for Food Process Hygiene Solutions, Melbourne, Victoria, Australia.

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 SporeForming Bacilli in the Dairy Indust