The Stability and Shelf-life of Food

WP0857_PDF_TOC......Page 1
The stability and shelf-life of food......Page 3
Contents......Page 5
Preface......Page 9
Contributors......Page 11
1.1 What is shelf-life?......Page 13
Part 2: Case studies......Page 0
1.2 Factors influencing shelf-life......Page 15
1.2.1 Microbiological changes......Page 16
1.2.3 Physical deteriorative changes......Page 17
1.4.1 Sensory panels......Page 18
1.4.2 Instrumental methods......Page 19
1.4.3 Physical measurements......Page 20
1.4.4 Chemical measurements......Page 22
1.5.1 Accelerated shelf-life testing......Page 23
1.5.2 Predictive models......Page 24
1.6 The design of shelf-life experiments......Page 25
1.7 Extending of shelf-life......Page 27
Sous-vide processing......Page 28
1.7.2 Packaging......Page 29
1.8 The structure of this book......Page 30
1.9 References......Page 31
Appendix......Page 32
Part 1: Analysing shelf-life......Page 35
2.1 Introduction......Page 36
2.2.1 Water activity – its uses and limitations......Page 38
2.2.2 Sorption isotherms......Page 39
2.3.1 State diagrams and viscosity......Page 41
2.3.2 Equations used to fit and predict Tg......Page 44
2.3.4 Measuring Tg......Page 46
2.4.1 Microbial growth in the glass transition region......Page 48
2.4.2 Stabilising effects of the glassy state......Page 52
2.4.3 Rates of reactions in relation to the glass transition......Page 54
2.4.4 The glass transition and the stability of frozen foods......Page 56
2.5 Conclusions......Page 57
2.6 Acknowledgements......Page 58
2.7 References......Page 59
3.1 Introduction......Page 66
3.2.2 Experimental design......Page 68
3.2.4 Modelling and mathematical validation......Page 69
3.2.5 Product validation......Page 71
3.3.1 Food MicroModel......Page 73
3.3.2 Pathogen Modeling Program......Page 74
3.3.3 Pseudomonas Predictor......Page 75
3.3.5 Decision Support System......Page 76
3.3.8 ChefCad software......Page 77
3.3.11 MicroFit......Page 78
3.4.2 Meat and meat products......Page 79
3.4.3 Fish......Page 81
3.4.4 Vegetable products......Page 82
3.4.5 Considerations when applying models......Page 83
3.5 Future trends......Page 84
3.6 Sources of further information and advice......Page 85
3.7 References......Page 86
4.1 Introduction......Page 90
4.2.1 The human senses......Page 92
4.2.2 Factors influencing the quality of sensory data......Page 94
4.3.2 Provision of a dedicated sensory testing environment......Page 95
4.3.3 Selection of suitable test procedures......Page 96
Analytical tests......Page 97
4.3.5 Data handling, analysis and presentation......Page 98
4.4.2 Duo–trio test......Page 99
4.4.5 Analysis of discrimination tests......Page 100
4.5 Quantitative descriptive tests......Page 101
4.5.1 Scaling procedures......Page 102
Vocabulary development......Page 103
4.5.4 The Spectrum TM method......Page 104
4.5.6 Time-related methods......Page 105
4.5.8 Multivariate analysis of scaled data......Page 106
4.7.1 Selection of tests for shelf-life assessment......Page 107
4.8 The interpretation of sensory shelf-life data......Page 108
4.9 Instrumental methods in sensory shelf-life testing......Page 110
4.9.1 Appearance......Page 111
4.9.2 Aroma and flavour......Page 112
4.10 Future trends......Page 113
4.11 References......Page 114
5.2 Basic principles......Page 117
5.3 Initial rate approach......Page 118
5.4 Kinetic model approach......Page 120
5.4.1 Single accelerating factor......Page 122
5.4.2 Glass transition models......Page 126
5.4.3 Multiple accelerating factors......Page 127
5.4.4 Accelerated methods for establishing a kinetic model......Page 129
5.4.5 The ‘no model’ approach......Page 130
5.4.6 Combination of approaches......Page 132
5.5.1 Absence of deterioration index......Page 133
5.5.3 Statistical problems......Page 134
5.7 References......Page 135
6.1 Introduction: starch retrogradation......Page 139
6.2.2 Techniques monitoring the impact of reordering on molecular mobility and rheology......Page 140
6.4 Principles of NMR......Page 141
6.5.2 Results and discussion......Page 146
6.6 Future trends......Page 150
6.7 Sources of further information and advice......Page 151
6.8 References......Page 152
Part 2:
Case studies......Page 153
7.1.1 The role of packaging......Page 154
7.1.2 Packaging usage......Page 156
7.2.1 Abiotic spoilage of foods......Page 157
7.2.2 Moisture......Page 158
7.2.4 Light......Page 159
7.2.6 Temperature......Page 160
7.3.1 Biotic spoilage......Page 161
7.3.3 Heat treatment as a means of extending shelf-life......Page 162
7.3.5 Modified-atmosphere packaging (MAP)......Page 164
7.4 The range of packaging options available......Page 166
7.4.2 Glass......Page 167
7.4.3 Metal containers......Page 168
7.4.4 Aluminium foil......Page 169
7.4.5 Paper-based packaging materials......Page 170
7.4.6 Plastics......Page 171
7.5.1 Calculating barrier requirements......Page 173
7.5.2 Choosing the right barrier......Page 174
7.5.5 Product and packaging development......Page 175
7.8 Sources of further information and advice......Page 177
7.9 References......Page 178
8.1 Introduction......Page 179
8.2.2 Product formulation......Page 182
Poultry......Page 183
8.2.4 Thermal processing......Page 184
8.2.5 Cooling......Page 185
8.2.6 Chilled storage and distribution......Page 186
8.3 How shelf-life is measured......Page 187
Screening subjects for QDA......Page 188
A generic QDA training programme......Page 189
Evaluation of panellists and descriptors......Page 190
Panel agreement......Page 191
QDA: experimental design and statistical analysis......Page 192
Consumer acceptance testing: experimental design and statistical analysis......Page 193
8.3.5 Instrumental evaluation......Page 195
8.4 Extending shelf-life......Page 196
8.6 Sources of further information and advice......Page 197
8.7 References......Page 198
9.1 Introduction......Page 205
9.2.1 Milk protein......Page 206
9.2.2 Milk fat......Page 208
9.3.1 Psychrotrophic Gram-negative bacteria......Page 210
9.3.2 Heat-resistant bacteria......Page 212
9.4.2 Plasmin......Page 213
Post-heat treatment contamination......Page 214
Heat-resistant organisms......Page 215
9.6.1 Cottage cheese......Page 217
9.7.1 Heat-resistant enzymes......Page 218
Methods of detection of extracellular enzyme activity......Page 219
9.8.1 Butter and spreads......Page 220
9.8.2 Dried milk products......Page 221
9.8.4 Sterile concentrated milk......Page 222
9.8.6 Cream liqueurs......Page 223
9.8.7 Cheese......Page 224
9.11 Bibliography......Page 226
10.2.1 Product composition......Page 228
10.2.3 Moisture migration and equilibrium relative humidity......Page 229
10.3 Chocolate and chocolate products......Page 231
10.3.1 Fat bloom......Page 232
10.3.2 Sensory changes during storage......Page 234
10.3.4 Anti-bloom agents......Page 236
10.3.5 Moisture migration......Page 237
10.3.6 Accelerated storage tests......Page 238
10.4.1 Structure and influence of composition on glass transition......Page 239
10.5.1 Structure and composition......Page 240
10.5.2 Microstructural changes affecting texture......Page 241
10.5.3 Shelf-life assessment......Page 243
10.6.1 Physical characteristics and microstructure......Page 244
10.6.2 Shelf-life measurement......Page 247
10.7.1 Composition and structure......Page 248
10.7.2 Deteriorative changes during storage......Page 249
Trade/professional bodies......Page 251
Books......Page 252
10.9 References......Page 253
11.1 Introduction......Page 256
11.2.1 Introduction......Page 257
11.2.2 Quality criteria in fresh produce......Page 258
Texture......Page 259
11.2.3 Causes of quality deterioration in harvested fruits and vegetables......Page 260
Breaking of dormancy......Page 261
Fungal and bacterial pathogens......Page 262
Physiological disorders......Page 264
Physical injury......Page 265
11.3.1 Introduction......Page 266
Firmness......Page 267
Taste components......Page 268
11.4.1 Introduction......Page 269
Vacuum cooling......Page 270
Dehydration ('curing' ) of bulb crops......Page 271
Sprouting suppressants for root, tuber and bulb crops......Page 272
11.4.4 Refrigerated storage......Page 273
11.4.5 Controlled atmosphere storage......Page 274
Modified-atmosphere packaging (MAP)......Page 275
11.5.2 On-line technologies for non-destructive grading and shelf-life evaluation......Page 276
11.5.3 Replacements for post-harvest chemicals......Page 277
11.6 Conclusions......Page 278
11.7.1 UK-based research organisations......Page 279
11.8 References......Page 280
12.1 Introduction......Page 286
12.2 What determines the shelf-life of fats and oils?......Page 287
Hydrolytic rancidity development......Page 289
Oxidative rancidity development......Page 291
Polymorphism......Page 293
Quality defects......Page 296
12.2.3 Microbial stability......Page 297
Sensory evaluation......Page 298
Chemical analysis......Page 300
Microbiological analysis......Page 301
Accelerated storage trials......Page 302
Oxygen bomb methods......Page 303
12.3.3 Set-up of storage trials......Page 304
12.4 Measures for ensuring storage stability and extending shelf-life of fats and oils......Page 306
Oxygen content......Page 307
Antioxidants......Page 308
Storage conditions......Page 310
12.5 Future trends......Page 311
12.6 Sources of further information and advice......Page 313
12.8 References......Page 314
13.1.1 Mayonnaise......Page 317
13.1.2 Dressings......Page 318
Appearance......Page 319
Stability......Page 320
13.2.2 Microbial activity......Page 323
Pathogens – food safety......Page 325
13.3.1 Storage trials – sensory......Page 326
13.3.2 Storage trials – microbiology......Page 327
13.3.4 Predictive modelling......Page 328
13.4 Implications of measurement for formulation and preservation......Page 329
13.5 Extending shelf-life......Page 331
13.6 Future trends......Page 334
13.8 References......Page 335