Essentials of Thermal Processing

Essentials of Thermal Processing......Page 4
Contents......Page 6
Preface......Page 14
Glossary of Terms......Page 18
1.1 A BRIEF HISTORY OF THE SCIENCE AND TECHNOLOGY OF THERMAL PROCESSING......Page 26
1.2 FOOD MICROBIOLOGY......Page 31
1.2.1 Fungi......Page 32
1.2.1.1 Moulds......Page 33
1.2.1.2 Yeasts......Page 34
1.2.2 Bacteria......Page 35
1.2.2.1 Growth and reproduction of bacteria......Page 36
1.3.1 pH......Page 38
1.3.2 Moisture......Page 40
1.3.3 Nutrients......Page 41
1.3.4 Oxidation–reduction potential......Page 42
1.3.7 Relative humidity......Page 43
1.3.9 Temperature......Page 44
1.4 DESCRIPTION OF SOME MICROORGANISMS OF IMPORTANCE TO THERMAL PROCESSING......Page 45
1.4.2 Yeasts......Page 46
1.4.3.1 Thermophiles......Page 47
1.4.3.2 Mesophiles – spore-forming bacteria......Page 49
1.4.3.3 Mesophiles – non-spore forming pathogenic and spoilage bacteria......Page 51
1.4.3.4 Psychrophiles......Page 52
2 Hurdles to Microbial Growth......Page 54
2.2 USE OF RESTRICTIVE pH LEVELS......Page 56
2.3 ANAEROBIC ENVIRONMENT OR MODIFIED ATMOSPHERE ENVIRONMENT......Page 58
2.4 LOW TEMPERATURES......Page 59
2.5 DEHYDRATION OR LOW WATER ACTIVITY......Page 60
2.6 CHEMICAL PRESERVATION......Page 61
2.6.2 Sulphites and nitrites......Page 62
2.6.4 Antioxidants......Page 63
3 Low Acid Canned Foods......Page 64
3.1 HISTORY OF THE CANNING INDUSTRY......Page 65
3.2 PRODUCTION OF A THERMALLY PROCESSED FOOD......Page 67
3.3 F03 STERILISATION PROCESSES......Page 69
3.4 COMMERCIAL STERILISATION......Page 71
3.5 MICROORGANISM DEATH KINETICS......Page 73
3.6 LOG REDUCTIONS......Page 76
4.1 BACKGROUND......Page 80
4.2 THERMAL PROCESSING OF FRUIT......Page 81
4.3 PACKAGING SELECTION......Page 82
4.3.2 Pigments that discolour in internally plain cans......Page 83
4.4.1 Calculation of pasteurisation values......Page 84
4.5 INHIBITORY FACTORS TO MICROORGANISM GROWTH......Page 87
4.5.1 High acid: pH < 3.8......Page 88
4.5.2 Acid: pH 3.8–4.2......Page 90
4.6 P-VALUE GUIDELINES......Page 91
4.7 GUIDELINES TO CRITICAL FACTORS IN THERMAL PROCESSING OF ACID FOODS......Page 93
5.1 BACKGROUND......Page 96
5.2.1 The history of pH......Page 97
5.3 THE CHEMISTRY OF pH......Page 98
5.4.1 Potentiometric method......Page 101
5.4.2 Colorimetric measurement......Page 102
5.5 ACIDIFICATION OF FOODS......Page 103
5.6 PROCESSING ACIDIFIED FOODS......Page 104
5.7 DESIGN OF PASTEURISATION PROCESSES......Page 106
5.7.3 High acid range: pH below 3.8......Page 107
5.8.1 Ingredients......Page 108
5.8.3 Post process equilibrated pH......Page 109
5.8.5 pH during product shelf-life......Page 110
6 Heat Preserved Chilled Foods......Page 112
6.1 UNDERSTANDING MICROORGANISM BEHAVIOUR......Page 113
6.1.1 Pathogenic microorganisms relevant to chilled foods......Page 115
6.1.1.1 Clostridium botulinum......Page 116
6.1.1.2 Bacillus cereus......Page 118
6.1.2 Microorganisms likely to be found in chilled foods......Page 119
6.2 METHODS OF MANUFACTURE......Page 122
6.2.1 Thermal process step applied prior to packaging......Page 123
6.2.1.1 Low care–high care factories......Page 125
6.2.2 Thermal process step applied after packaging......Page 126
6.2.2.1 Caution with latent heat for frozen protein......Page 128
7.1 IN-PACK PROCESSING: RETORT SYSTEMS......Page 134
7.1.1 Condensing steam retorts......Page 135
7.1.2 Crateless retorts......Page 136
7.1.3 Water immersion retorts......Page 137
7.1.4 Water spray and cascade......Page 138
7.1.5 Steam/air retorts......Page 140
7.1.6 Shaka retorts......Page 141
7.1.7 Reel & spiral retorts......Page 142
7.1.8 Hydrostatic retorts......Page 143
7.2 IN-LINE PROCESSING: HEAT EXCHANGERS......Page 144
7.2.1 Flow behaviour......Page 145
7.2.2 Choice of heat exchanger......Page 150
7.3 NEW THERMAL TECHNOLOGIES......Page 155
8.1 MATHEMATICAL ANALYSIS OF COOKING......Page 158
8.1.1 Cooking equations and kinetic data......Page 159
8.1.2 Competition between sterilisation and cooking......Page 163
8.1.3 Optimisation of temperature/time in processing......Page 165
9 Measurement and Validation of Thermal Processes......Page 170
9.1 SETTING THE TARGET PROCESS VALUE......Page 171
9.2.1 How to select the worst case conditions......Page 172
9.2.1.3 Retort or processing system......Page 173
9.3.1 Temperature distribution tests......Page 174
9.3.2 Heat penetration tests......Page 176
9.3.2.1 Locating the product cold point......Page 177
9.4 PROCESS ESTABLISHMENT METHODS......Page 178
9.4.1 Temperature measurement systems for TD and HP testing......Page 179
9.4.2 Log reduction methods for HP testing......Page 181
9.4.2.1 Microbiological spore methods......Page 182
9.4.2.2 Biochemical systems......Page 185
9.5.1 General method......Page 186
9.5.2 Ball method......Page 187
9.5.3 Numerical methods......Page 188
10 Cooling and Water Treatment......Page 192
10.1 CHLORINE......Page 193
10.1.2 Using chlorine......Page 194
10.2 BROMINE......Page 195
10.3 Ozone......Page 196
10.4 ULTRAVIOLET LIGHT......Page 197
10.5 MEMBRANE FILTRATION......Page 198
11.1 WHAT CONSTITUTES A PROCESS DEVIATION......Page 200
11.2 WHAT CAN GO WRONG......Page 201
11.3 ACTIONS REQUIRED......Page 204
11.3.1 TPA actions......Page 205
11.3.2 Process deviation analysis for broken heating products......Page 208
12 Packaging Options for Heat Preserved Foods......Page 212
12.1.1 Tin plate......Page 214
12.1.4 Protective coatings (lacquers)......Page 215
12.1.4.3 Epoxy-phenolic lacquer......Page 216
12.1.5 Internally plain (unlacquered) cans......Page 218
12.2.1 Product specification......Page 220
12.2.3 Cleaning of empty unused cans......Page 221
12.2.4 Double seam formation and inspection procedures......Page 222
12.2.5 Washing of filled cans......Page 223
12.2.7.1 Corrosion prevention......Page 224
12.3 GLASS......Page 226
12.3.1 Glass manufacture......Page 227
12.3.2 Closures for sealing glass food containers......Page 228
12.3.3 Sealing mechanisms......Page 229
12.3.4 Inspection procedures......Page 230
12.3.5.3 Capping......Page 231
12.3.5.5 Pressure processing......Page 232
12.4 PLASTICS, FLEXIBLES AND LAMINATES......Page 233
12.4.2 Disadvantages of retortable plastics......Page 234
12.4.3.3 Ethylvinylalcohol (EVOH)......Page 235
12.4.4.1 Retort pouches......Page 236
12.4.5 Processing considerations – control of headspace......Page 239
13.1 PURPOSE OF INCUBATION TESTS......Page 242
13.2 CAUSES OF SPOILAGE......Page 243
13.2.1 Leaker spoilage......Page 244
13.2.2 Underprocessing......Page 245
13.2.3 Thermophilic spoilage......Page 247
13.3 DESCRIPTIVE TERMS FOR CANNED FOOD SPOILAGE......Page 248
13.4.1 Sample size......Page 249
13.4.2 Temperatures and times for incubation......Page 250
13.4.2.1 Thermophilic organisms......Page 251
13.4.3 Post incubation inspection of containers......Page 252
13.5 BIOTESTING......Page 253
14.1 BACKGROUND......Page 254
14.2 KEY ASPECTS OF HYGIENE CONTROL SYSTEMS FOR FOOD PROCESSING (FROM CODEX ALIMENTARIUS)......Page 255
14.3 IDENTIFYING CRITICAL CONTROL POINTS IN THERMAL PROCESSING......Page 256
14.3.3 Water activity (aw)......Page 257
14.3.4 Consistency......Page 258
14.3.6 Rehydration......Page 259
14.3.8 Size and style of in-going ingredients......Page 260
14.3.9.1 Headspace......Page 261
14.3.9.2 Container vacuum and exhausting of containers......Page 262
14.3.9.3 Container size and geometry......Page 263
14.3.10.2 Processing medium......Page 264
14.3.10.4 Processing temperature......Page 265
14.3.10.5 Processing time......Page 266
15 Environmental Aspects of Thermal Processing......Page 268
15.1 LIFECYCLE ASSESSMENT (LCA)......Page 269
15.1.1 Impact categories......Page 270
15.1.1.3 Abiotic resource use......Page 271
15.1.1.5 Eutrophication potential......Page 272
15.1.1.7 Water use......Page 273
15.2 GREENHOUSE GAS EMISSIONS......Page 274
15.2.1 Case study: Bottled apple juice......Page 275
15.2.1.1 Raw materials (0.407 kg CO2e/PU)......Page 276
15.2.1.2 Manufacture (0.061 kg CO2e/PU)......Page 277
15.2.1.4 Waste (0 kg CO2e/PU)......Page 278
15.2.1.6 GHG emissions for other food products......Page 279
Index......Page 284