Essentials of Thermal Processing

ESSENTIALS OF THERMAL PROCESSING Explore this fully updated new edition of a practical reference on food preservation from two leading voices in the industry Among all food preservation methods in use today, thermal processing remains the single most important technique used in the industry. The newly revised Second Edition of Essentials of Thermal Processing delivers a thorough reference on the science and applications of the thermal processing of a wide variety of food products. The book offers readers essential information on the preservation of food products by heat, including high-acid foods and low-acid sterilized foods requiring a full botulinum cook. The accomplished authors—noted experts in their field—discuss all relevant manufacturing steps, from raw material microbiology through the various processing regimes, validation methods, packaging, incubation testing, and spoilage incidents. Two new chapters on temperature and heat distribution, as well as heat penetration of foods, are included. More worked and practical examples are found throughout the book as well. Readers will also benefit from the inclusion of: A thorough introduction to the microbiology of heat processed foods, food preservation techniques, low acid canned foods, and high acid foods An exploration of acidified products, heat extended shelf-life chilled foods, and processing methods Discussions of cooking and process optimization, process validation, and heat penetration and process calculations An examination of cooling and water treatment, how to handle process deviations, and packaging options for heat preserved foods Perfect for professionals working in the food processing and preservation industries, Essentials of Thermal Processing will also earn a place in the libraries of anyone seeking a one-stop reference on the subject of thermal processing for food products.

Table of Contents:
Preface Glossary of Terms 1 History of Thermal Processing 1.1 A brief history of the science and technology of thermal processing 1.2 Food Microbiology as a Science 1.3 Packaging for Heat Preserved Foods 1.3.1 Convenience – the can opener is invented 1.3.2 Other forms of packing for “canned foods” 1.4 Developments in Cannery Equipment 1.5 Food Safety 2 Microbiology of Heat Preserved Foods 2.1 Food microbiology 2.1.1 Fungi 2.1.1.1 Moulds 2.1.1.2 Yeasts 2.1.2 Bacteria 2.1.2.1 Growth and reproduction of bacteria 2.2 Factors that affect the growth of microorganisms 2.2.1 pH 2.2.2 Moisture 2.2.3 Nutrients 2.2.4 Oxidation–reduction potential 2.2.5 Antimicrobial resistance 2.2.6 Biological structures 2.2.7 Relative humidity 2.2.8 Oxygen content/concentration of gases in the environment 2.2.9 Temperature 2.3 Description of some microorganisms of importance to thermal processing 2.3.1 Moulds 2.3.2 Yeasts 2.3.3 Bacteria 2.2.3.1 Thermophiles 2.3.3.2 Mesophiles – spore-forming bacteria 2.3.3.3 Mesophiles – non-spore forming pathogenic and spoilage bacteria 2.3.3.4 Psychrophiles 2.4 Risk of leaker spoilage from damaged or compromised packaging 2.5 A guideline for identifying spoilage in canned foods 3 Hurdles to Microbial Growth 3.1 Control of the microorganism loading 3.2 Use of restrictive pH levels 3.3 Anaerobic environment or modified atmosphere environment 3.4 Low temperatures 3.5 Dehydration or low water activity 3.6 Chemical preservation 3.6.1 Organic acids 3.6.2 Sulphites and nitrites 3.6.3 Antibiotics 3.6.4 Antioxidants 3.7 Irradiation 3.8 Combination Treatments 4 Low Acid Canned Foods 4.1 Production of a thermally processed food 4.2 F03 sterilisation processes 4.3 Commercial sterilisation 4.4 Microorganism death kinetics 4.5 Log reductions 5 Acid and Other Pasteurized Products 5.1 Background 5.1.1 Naturally acid foods 5.2 Pasteurisation 5.2.1 Considerations when designing a safe pasteurisation process 5.2.2 Calculation of pasteurisation values 5.3 Inhibitory factors to microorganism growth 5.4 P-value guidelines 5.4.1 High acid: pH < 3.5 5.4.2 Acid: pH 3.5–4.0 5.4.3 Acid: pH 4.0-4.2 5.4.4 Medium acid: pH 4.2–4.6 5.5 Guidelines and General Recommendations 5.5.1 Guidelines to critical factors in thermal processing of acid foods 5.6 Thermal processing of fruit  5.3.1 Packaging selection 5.3.2 Oxidation reactions inside an internally plain can of acid fruit 5.3.3 Pigments that discolour in internally plain cans 5.7 Thermal processing of products with low water activity 5.7.1 Jam and high sugar preserves 5.7.2 Canned cake and sponge pudding 5.8 Thermal processing of cured meats 6 Acidified Foods 6.1 Background 6.2 Acidity measurement using pH 6.2.1 The history of pH 6.2.2 The chemistry of pH 6.2.3 Measurement of pH 6.2.3.1 Potentiometric method 6.2.3.2 Colorimetric measurement 6.2.4 Equilibrium pH 6.3 Acidification of foods 6.4 Processing acidified foods 6.5 Design of pasteurisation processes 6.5.1 Medium acid range: pH 4.2–4.6 6.5.2 Acid range: pH 3.5–4.2 6.5.3 High acid range: pH below 3.5 6.6 Hot fill and hold processing 6.7 Critical control points in the production of acidified foods 6.7.1 Ingredients 6.7.2 Heat processing 6.7.3 Post process equilibrated pH 6.7.4 Container integrity 6.7.5 pH during product shelf-life 7 Heat Preserved Chilled Foods 7.1 Understanding microorganism behaviour 7.1.1 Pathogenic microorganisms relevant to chilled foods 7.1.1.1 Clostridium botulinum 7.1.1.2 Bacillus cereus 7.1.2 Microorganisms likely to be found in chilled foods 7.2 Methods of manufacture 7.2.1 Thermal process step applied prior to packaging 7.2.1.1 Low care–high care factories 7.2.2 Thermal process step applied after packaging 7.2.2.1 Caution with latent heat for frozen protein 8 Processing Systems 8.1 In-pack processing: Retort systems 8.1.1 Condensing steam retorts 8.1.2 Crateless retorts 8.1.3 Water immersion retorts 8.1.4 Water spray and cascade 8.1.5 Steam / air retorts 8.1.6 Shaka retorts 8.1.7 Reel & spiral retorts 8.1.8 Hydrostatic retorts 8.2 In-line processing: Heat exchangers 8.2.1 Flow behaviour 8.2.2 Choice of heat exchanger 8.2.3 Maximising product recovery 7.3 New thermal technologies 9 Cook Values and Optimisation of Thermal Processes 9.1 Mathematical analysis of cooking 9.1.1 Cooking equations and kinetic data 9.1.2 Competition between sterilisation and cooking 9.1.3 Optimisation of temperature / time in processing 9.2 Setting process targets 9.2.1 How to select processing conditions without excess quality damage 10 Process Validation: Temperature and Heat Distribution 10.1 Temperature Distribution 10.1.1 Temperature measurement systems 10.2 Heat Distribution 10.2.1 Modes of heat transfer 10.2.1.1 Radiation 10.2.1.2 Conduction 10.2.1.3 Convection 10.2.1.4 Broken heating or mixed heating 10.3 Heat distribution testing 10.3.1 Conducting a HD test 11 Process Validation: Heat Penetration and Process Calculations 11.1 Setting the target process value 11.2 Selecting the conditions for the HP study 11.3 Locating the product cold point 11.4 Process establishment methods 11.4.1 Log reduction methods for HP testing 11.4.1.1 Microbiological spore methods 11.4.1.2 Biochemical systems 11.5 Process calculation methods 11.5.1 General method 11.5.2 Ball method 11.5.3 Numerical methods 11.5.3 Continuous flow with particulates 12 Cooling and Water Treatment 12.1 Chlorine 12.1.1 Chlorine demand and residual chlorine 12.1.2 Using chlorine 12.2 Chlorine dioxide 12.3 Bromine 12.4 Ozone 12.5 Ultraviolet light 12.6 Membrane filtration 13 Handling Processing Deviations 13.1 What constitutes a process deviation 13.2 What can go wrong 13.3 Actions required 13.3.1 TPA actions 13.3.2 Process deviation analysis for broken heating products 13.3.2 Reprocessing 14 Packaging Options for Heat Preserved Foods 14.1 Metal containers 14.1.1 Tin plate 14.1.2 Tin free steel (TFS or ECCS) 14.1.3 Aluminium 14.1.4 Protective coatings (lacquers) 14.1.4.1 Vinyl lacquers 4 14.1.4.2 Organosol lacquers 14.1.4.3 Epoxy-phenolic lacquer 14.1.4.4 Polyester lacquer 14.1.4.5 Acrylic Lacquers 14.1.4.6 Side stripe lacquers to cover the weld 14.1.5 Internally plain (unlacquered) cans 14.1.6 External covering 14.2 Can construction and handling 14.2.1 Product specification 14.2.2 Storage and handling of empty unused cans and ends 14.2.3 Cleaning of empty unused cans 14.2.4 Double seam formation and inspection procedures 14.2.5 Washing of filled cans 14.2.6 Processing of cans 14.2.7 Cooling of cans 14.2.7.1 Corrosion prevention 14.2.8 Secondary packaging 14.3 Glass 1.3.1 Glass manufacture 14.3.2 Closures for sealing glass food containers 14.3.3 Sealing mechanisms 14.3.4 Inspection procedures 14.3.5 Packing and processing 14.3.5.1 Inspection and preparation of containers 14.3.5.2 Filling 14.3.5.3 Capping 14.3.5.4 Atmospheric processing 14.3.5.5 Pressure processing 14.3.5.6 Cooling 14.4 Plastics, flexibles and laminates 14.4.1 Advantages of retortable plastics 14.4.2 Disadvantages of retortable plastics 14.4.3 Polymers used for retortable packaging 14.4.3.1 Polypropylene (PP) 14.4.3.2 Polyethylene terephthalate (PET) 14.4.3.3 Ethylvinylalcohol (EVOH) 14.4.3.4 Polyvinylidene chloride (PVDC) 14.4.3.5 Polyamide (PA) 14.4.3.6 Aluminium 14.4.3.7 Glass-coated barrier films 14.4.4 Types of packages used for thermally processed foods 14.4.4.1 Retort pouches 14.4.4.2 Plastic cans and pots 14.4.4.3 Retortable composite carton 14.4.5 Processing considerations – control of headspace 15 Incubation Testing 15.1 Purpose of incubation tests 15.2 Causes of spoilage 15.2.1 Leaker spoilage 15.2.2 Under-processing 15.2.3 Thermophilic spoilage 15.3 Descriptive terms for canned food spoilage 15.4 Methods for incubation testing 15.4.1 Sample size 15.4.2 Temperatures and times for incubation 15.4.2.1 Thermophilic organisms 15.4.2.2 Mesophilic organisms 15.4.3 Post incubation inspection of containers 15.5 Biotesting 16 Critical Factors in Thermal Processing 16.1 Background 16.2 Key aspects of hygiene control systems for food processing (from Codex Alimentarius) 16.3 Identifying critical control points in thermal processing 16.3.1 Microbial load or bio-burden 16.3.2 pH of the product 16.3.3 Water activity (aw) 16.3.4 Consistency 16.3.5 Presence, concentration and types of preservatives 16.3.6 Rehydration 16.3.7 Blanching 16.3.8 Size and style of in-going ingredients 16.3.9 Container, packing and filling considerations 16.3.9.1 Headspace 16.3.9.2 Container vacuum and exhausting of containers 16.3.9.3 Container size and geometry 16.3.9.4 Initial temperature of product 16.3.10 Process related critical factors 16.3.10.1 Processing method 16.3.10.2 Processing medium 16.3.10.3 Type and characteristics of heat processing system 16.3.10.4 Processing temperature 16.3.10.5 Processing time 16.3.10.6 Processing at high altitudes 17 Environmental Aspects of Thermal Processing 17.1 Lifecycle Assessment (LCA) 17.1.1 Impact categories 17.1.1.1 Global warming potential (GWP) 17.1.1.2 Pesticide use / ecotoxicity 17.1.1.3 Abiotic resource use 17.1.1.4 Acidification potential 17.1.1.5 Eutrophication potential 17.1.1.6 Land use 17.1.1.7 Water use 17.2 Greenhouse gas emissions 17.2.1 Case study: Bottled apple juice 17.2.1.1 Raw materials (0.407 kg CO2e/PU) 17.2.1.2 Manufacture (0.061 kg CO2e/PU) 17.2.1.3 Transportation (0.057 kg CO2e/PU) 17.2.1.4 Waste (0 kg CO2e/PU) 17.2.1.5 Overall carbon footprint (0.525 kg CO2e/PU) 17.2.1.6 GHG emissions for other food products Index

About the Author :
Gary Tucker, Campden BRI in the United Kingdom. Susan Featherstone is a Director at Safe Food Consulting in South Africa.