This book covers many aspects of thermal processing of milk and milk products with particular focus on UHT processing. It commences with an overview of the major thermal processing technologies: thermisation, pasteurisation, extended-shelf-life (ESL), UHT and in-container sterilisation. It discusses the principles of the technologies, the processing and packaging equipment used, processing issues such as temperature-time profiles, heat stability, fouling and cleaning, and the quality and safety aspects of the products produced. It provides a balance of the engineering aspects of the processes…mehr
This book covers many aspects of thermal processing of milk and milk products with particular focus on UHT processing. It commences with an overview of the major thermal processing technologies: thermisation, pasteurisation, extended-shelf-life (ESL), UHT and in-container sterilisation. It discusses the principles of the technologies, the processing and packaging equipment used, processing issues such as temperature-time profiles, heat stability, fouling and cleaning, and the quality and safety aspects of the products produced. It provides a balance of the engineering aspects of the processes and the chemical, microbiological and sensory aspects of the products. The changes that occur in products during processing and storage, and the related defects which can arise, are central to the book. The discussions of these changes will be an aid to industry personnel in identifying the causes of quality defects in these products and devising measures which can be taken to eliminate or minimise the defects.
About the Authors Hilton C. Deeth, Emeritus Professor, School of Agriculture and Food Sciences, University of Queensland, Australia, and consultant to the dairy industry Michael J. Lewis, Honorary Fellow, Department of Food and Nutritional Sciences, Taught and researched at The University of Reading, Whiteknights, UK, for 38 years and now working as an adviser on milk and milk products
Inhaltsangabe
About the Authors xv
Preface xvii
List of Abbreviations xxi
1 History and Scope of the Book 1
1.1 Setting the Scene 1
1.2 Scope of the Book 7
1.3 Reasons for Heating Foods 7
1.4 Brief History of Sterilisation Processes 8
References 12
2 Heat Treatments of Milk - Thermisation and Pasteurisation 15
2.1 Introduction 15
2.2 Thermisation 16
2.3 Pasteurisation 17
2.3.1 Introduction 17
2.3.2 Historical Background 18
2.3.3 Pasteurisation Equipment 21
2.3.4 Process Characterisation 24
2.3.5 Processing Conditions 27
2.3.6 Changes During Pasteurisation 28
2.3.7 Changes During Storage 32
2.3.8 Pasteurisation of Other Milk?-Based Products 34
References 36
3 Heat Treatments of Milk - ESL, UHT and in?-Container Sterilisation 41
3.1 Introduction 41
3.2 Some Important Definitions 41
3.2.1 Q10 41
3.2.2 Bacterial Indices, B* and F0 42
3.2.3 Chemical Index, C* 43
3.3 Extended Shelf?-Life (ESL) Milk Processing 44
3.3.1 ESL Milk by Thermal Treatment 44
3.3.2 ESL Milk by Microfiltration Plus HTST Heat Treatment 49
3.3.3 ESL Milk by Thermal Treatment Plus Bactofugation 50
3.3.4 ESL Milk by Thermal Treatment Plus an Antibacterial Agent 50
3.3.5 ESL Milk by Thermal Treatment Plus a Non?-Thermal Technology Treatment 50
3.3.6 ESL Milk by Multiple Thermal Treatments 51
3.4 Sterilisation 52
3.4.1 Introduction 52
3.4.2 UHT Processing 54
3.4.3 In?-Container Sterilisation 58
References 61
4 Microbiological Aspects 65
4.1 Introduction 65
4.2 Bacteria in Raw Milk 65
4.2.1 Non?-Spore?-Forming Psychrotrophic Bacteria and their Heat?-Resistant Enzymes 68
4.2.2 Spore?-Forming Bacteria 69
4.3 Heat Inactivation of Bacteria 78
4.4 Microflora in Processed Milks 80
4.4.1 Pasteurised Milk 80
4.4.2 ESL Milk 83
4.4.3 UHT Milk 85
4.4.4 In?-Container Sterilised Milk 90
4.5 Sterilisation of Equipment and Packaging to Prevent Microbial Contamination of UHT Products 90
References 91
5 UHT Processing and Equipment 103
5.1 The UHT Process 103
5.2 Heating 104
5.2.1 Steam?-/Hot?-Water?Based Heating Systems 104
5.2.2 Electrically Based Heating Systems 146
5.3 Homogenisation 150
5.4 Deaeration 154
5.5 Aseptic Packaging 155
5.5.1 Types of Packaging 155
5.5.2 Sterilisation of Packaging 158
5.5.3 Establishing and Maintaining a Sterile Environment 158
5.5.4 Aseptic Package Integrity 159
5.5.5 Validation of Aseptic Packaging Operations 159
5.6 Plant Cleaning and Sanitisation 161
5.6.1 Introduction 161
5.6.2 Rinsing 161
5.6.3 Water.Product Changeover 162
5.6.4 Cleaning 162
5.6.5 Methods of Measuring Cleaning Effectiveness 164
