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Gary Tucker S.. Essentials of Thermal Processing
Table of Contents
List of Tables
List of Illustrations
Guide
Pages
Essentials of Thermal Processing
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. 1.4.1 Seaming
1.4.2 Processing
1.5 FOOD SAFETY
References
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 MICRO‐ORGANISMS
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
2.2.9.1 D‐value
2.2.9.1.1 Probability of a non‐sterile unit (PSNU)
2.2.9.2 z‐value
2.3 DESCRIPTION OF SOME MICRO‐ORGANISMS OF IMPORTANCE TO THERMAL PROCESSING
2.3.1 Moulds
2.3.2 Yeasts
2.3.3 Bacteria
2.3.3.1 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
References
3 Hurdles to Microbial Growth
3.1 CONTROL OF THE MICRO‐ORGANISM 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
3.6.1.1 CIMCSEE code
3.6.2 Sulphites and nitrites
3.6.3 Antibiotics
3.6.4 Antioxidants
3.7 IRRADIATION
3.8 COMBINATION TREATMENTS
References
4 Low‐acid Canned Foods
4.1 PRODUCTION OF A THERMALLY PROCESSED FOOD
4.2 F03 STERILISATION PROCESSES
4.3 COMMERCIAL STERILISATION
4.4 MICRO‐ORGANISM DEATH KINETICS
4.5 LOG REDUCTIONS
Worked example 4.1Clostridium sporogenes
Worked example 4.2Bacillus stearothermophilus
References
5 Acid Foods and Other Pasteurised 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 MICRO‐ORGANISM GROWTH
5.4 PASTEURISATION VALUE (P‐VALUE) GUIDELINES. 5.4.1 High acid: pH < 3.5
Example 5.1 Apricot softening
Example 5.2 Processing of grapefruit
5.4.2 Acid: pH 3.5–4.0
5.4.3 Acid: pH 4.0–4.2
Example 5.3 Canning of peaches
Example 5.4 Canning of pears
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
Example 5.5 Thermo‐tolerant aciduric spore‐forming bacteria
5.6 THERMAL PROCESSING OF FRUIT
5.6.1 Packaging selection
5.6.2 Oxidation reactions inside an internally plain can of acid fruit
5.6.3 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 cakes and sponge puddings
5.7.3 Bacteria of concern
Example 5.6 Everfresh retorted bread and cake products
5.7.4 Yeast and mould
5.7.5 Process recommendations – cake
5.7.6 Process recommendations – bread
5.8 THERMAL PROCESSING OF CURED MEATS
References
Note
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
Example 6.1 Calculating the pH of a solution
6.2.3 Measurement of pH
6.2.3.1 Potentiometric method
Example 6.2 Measuring the pH of salad dressing
Example 6.3 Measuring the pH of acidified bean salad
6.2.3.2 Colorimetric measurement
6.2.4 Equilibrium pH
6.3 ACIDIFICATION OF FOODS
Example 6.4 Cold preservation of pickles by acids
6.4 PROCESSING ACIDIFIED FOODS
Example 6.5 Spaghetti in Tomato Sauce
Example 6.6 Fresh packed whole pepper pickles (Downing 1996)
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
References
Note
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
Worked example 7.1 6‐log process for psychrotrophic C. 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
Box 7.1 Food poisoning example: Canned chilled carrot juice
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
Worked example 7.2 Energy required to thaw frozen chicken
References
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 and spiral retorts
8.1.8 Hydrostatic retorts
8.2 IN‐LINE PROCESSING: HEAT EXCHANGERS
8.2.1 Flow behaviour
Worked example 8.1 Reynolds number for a tomato ketchup
Worked example 8.2 Reynolds number for a fruit juice
8.2.2 Choice of heat exchanger
8.2.3 Maximising product recovery
8.3 NEW THERMAL TECHNOLOGIES
References
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
Worked example 9.1 Quality optimisation for a vitamin with z‐value of 33 °C (e.g. thiamine)
Worked example 9.2 Quality optimisation for a white sauce
Worked example 9.3 Optimisation for retention of vitamin C in canned oranges
9.2 SETTING PROCESS TARGETS
9.2.1 How to select processing conditions without excess quality damage
Worked example 9.4 Deciding on worst case heat penetration factors for canned soup with vegetables
Worked example 9.5 Setting optimised processes close to F03
References
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
Example Factors that affect starch gelatinization
10.3 HEAT DISTRIBUTION TESTING
10.3.1 Conducting a HD test
References
11 Process Validation: Heat Penetration and Process Calculations
11.1 SETTING THE TARGET PROCESS VALUE
11.2 SELECTING THE CONDITIONS FOR THE HP STUDY
11.2.1 Product
11.2.2 Container or package
11.2.3 Retort or processing system
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
Worked example 11.1
Worked example 11.2
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
11.5.4 Continuous flow with particulates
References
12 Cooling 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
References
13 Handling Processing Deviations. 13.1 WHAT CONSTITUTES A PROCESS DEVIATION
13.2 WHAT CAN GO WRONG
13.3 ACTIONS REQUIRED
Box 13.1 Brand damage
13.3.1 TPA actions
Worked example 13.1 Process deviation caused by boiler failure – using the Ball method
Worked example 13.2 Process deviation caused by boiler failure – using the CTemp method
13.3.2 Process deviation analysis for broken heating products
Worked example 13.3 Process deviation caused by boiler failure – using the CTemp method but with a 10‐minute hold extension
13.3.3 Reprocessing
Worked example 13.4
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
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
Box 14.1 Migration Compounds
14.1.4.6 Side stripe lacquers to cover the weld
14.1.5 Internally plain (unlacquered) cans
Box 14.2 Tin in food (UK, Food Standards Agency 2002)
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
Box 14.3 Properties of glass
14.3.1 Glass manufacture
Box 14.4 Recycled glass
14.3.2 Closures for sealing glass food containers
14.3.3 Sealing mechanisms
14.3.4 Inspection procedures
Box 14.5 Tamper evidence
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 Ethyl‐vinylalcohol (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
Example 14.1 Retort pouches for tuna
14.4.4.2 Plastic cans and pots
14.4.4.3 Retortable composite carton
14.4.4.4 Processing considerations – control of headspace
Box 14.6 Induction sealing
References
15 Incubation Testing
15.1 PURPOSE OF INCUBATION TESTS
15.2 CAUSES OF SPOILAGE
15.2.1 Leaker spoilage
Box 15.1 Example of leaker spoilage: Staphylococcus aureus in canned peas (1957, UK)
Box 15.2 Example of leaker spoilage: Salmonella typhiin canned corned beef (1964, Aberdeen, Scotland)
15.2.2 Under processing
Box 15.3 Example of under processing: Clostridium botulinum in canned vichyssoise soup (1971, USA)
15.2.3 Thermophilic spoilage
Box 15.4 Example of thermophilic spoilage: Bacillus sporothermodurans in retorted rice
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
References
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 altitude
References
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
Example 17.1 Beef, a high‐carbon footprint ingredient
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
References
Index
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