Food Process Engineering and Technology (eBook)

Front Cover 1
Food Process Engineering and Technology 4
Copyright Page 5
Contents 6
Introduction – Food is Life 18
Chapter 1 Physical properties of food materials 24
1.1 Introduction 24
1.2 Mechanical properties 25
1.2.1 Definitions 25
1.2.2 Rheological models 26
1.3 Thermal properties 27
1.4 Electrical properties 28
1.5 Structure 28
1.6 Water activity 30
1.6.1 The importance of water in foods 30
1.6.2 Water activity, definition and determination 31
1.6.3 Water activity: prediction 31
1.6.4 Water vapor sorption isotherms 33
1.6.5 Water activity: effect on food quality and stability 36
1.7 Phase transition phenomena in foods 36
1.7.1 The glassy state in foods 36
1.7.2 Glass transition temperature 37
Chapter 2 Fluid flow 44
2.1 Introduction 44
2.2 Elements of fluid dynamics 44
2.2.1 Viscosity 44
2.2.2 Fluid flow regimes 45
2.2.3 Typical applications of Newtonian laminar flow 47
2.2.3a Laminar flow in a cylindrical channel (pipe or tube) 47
2.2.3b Laminar fluid flow on flat surfaces and channels 50
2.2.3c Laminar fluid flow around immersed particles 51
2.2.3d Fluid flow through porous media 53
2.2.4 Turbulent fluid flow 53
2.2.4a Turbulent Newtonian fluid flow in a cylindrical channel (tube or pipe) 54
2.2.4b Turbulent fluid flow around immersed particles 56
2.3 Flow properties of fluids 57
2.3.1 Types of fluid flow behavior 57
2.3.2 Non-Newtonian fluid flow in pipes 58
2.4 Transportation of fluids 60
2.4.1 Energy relations, the Bernoulli Equation 60
2.4.2 Pumps: Types and operation 63
2.4.3 Pump selection 69
2.4.4 Ejectors 72
2.4.5 Piping 73
2.5 Flow of particulate solids (powder flow) 73
2.5.1 Introduction 73
2.5.2 Flow properties of particulate solids 74
2.5.3 Fluidization 79
2.5.4 Pneumatic transport 82
Chapter 3 Heat and mass transfer, basic principles 86
3.1 Introduction 86
3.2 Basic relations in transport phenomena 86
3.2.1 Basic laws of transport 86
3.2.2 Mechanisms of heat and mass transfer 87
3.3 Conductive heat and mass transfer 87
3.3.1 The Fourier and Fick laws 87
3.3.2 Integration of Fourier's and Fick's laws for steady-state conductive transport 88
3.3.3 Thermal conductivity, thermal diffusivity and molecular diffusivity 90
3.3.4 Examples of steady-state conductive heat and mass transfer processes 93
3.4 Convective heat and mass transfer 98
3.4.1 Film (or surface) heat and mass transfer coefficients 98
3.4.2 Empirical correlations for convection heat and mass transfer 101
3.4.3 Steady-state interphase mass transfer 104
3.5 Unsteady state heat and mass transfer 106
3.5.1 The 2nd Fourier and Fick laws 106
3.5.2 Solution of Fourier's second law equation for an infinite slab 107
3.5.3 Transient conduction transfer in finite solids 109
3.5.4 Transient convective transfer in a semi-infinite body 111
3.5.5 Unsteady state convective transfer 112
3.6 Heat transfer by radiation 113
3.6.1 Interaction between matter and thermal radiation 113
3.6.2 Radiation heat exchange between surfaces 114
3.6.3 Radiation combined with convection 117
3.7 Heat exchangers 117
3.7.1 Overall coefficient of heat transfer 117
3.7.2 Heat exchange between flowing fluids 119
3.7.3 Fouling 121
3.7.4 Heat exchangers in the food process industry 122
3.8 Microwave heating 124
3.8.1 Basic principles of microwave heating 125
3.9 Ohmic heating 126
3.9.1 Introduction 126
3.9.2 Basic principles 127
3.9.3 Applications and equipment 129
Chapter 4 Reaction kinetics 132
4.1 Introduction 132
4.2 Basic concepts 133
4.2.1 Elementary and non-elementary reactions 133
4.2.2 Reaction order 133
4.2.3 Effect of temperature on reaction kinetics 136
4.3 Kinetics of biological processes 138
4.3.1 Enzyme-catalyzed reactions 138
4.3.2 Growth of microorganisms 139
4.4 Residence time and residence time distribution 140
4.4.1 Reactors in food processing 140
4.4.2 Residence time distribution 141
Chapter 5 Elements of process control 146
5.1 Introduction 146
5.2 Basic concepts 146
5.3 Basic control structures 148
5.3.1 Feedback control 148
5.3.2 Feed-forward control 148
5.3.3 Comparative merits of control strategies 149
5.4 The block diagram 149
5.5 Input, output and process dynamics 150
5.5.1 First order response 150
5.5.2 Second order systems 152
5.6 Control modes (control algorithms) 153
5.6.1 On-off (binary) control 153
5.6.2 Proportional (P) control 155
5.6.3 Integral (I) control 156
5.6.4 Proportional-integral (PI) control 157
5.6.5 Proportional-integral-differential (PID) control 157
5.6.6 Optimization of control 158
5.7 The physical elements of the control system 159
5.7.1 The sensors (measuring elements) 159
5.7.2 The controllers 166
5.7.3 The actuators 166
Chapter 6 Size reduction 170
6.1 Introduction 170
6.2 Particle size and particle size distribution 171
6.2.1 Defining the size of a single particle 171
6.2.2 Particle size distribution in a population of particles defining a 'mean particle size'
6.2.3 Mathematical models of PSD 175
6.2.4 A note on particle shape 177
6.3 Size reduction of solids, basic principles 180
6.3.1 Mechanism of size reduction in solids 180
6.3.2 Particle size distribution after size reduction 180
6.3.3 Energy consumption 180
6.4 Size reduction of solids, equipment and methods 182
6.4.1 Impact mills 183
6.4.2 Pressure mills 184
6.4.3 Attrition mills 185
6.4.4 Cutters and choppers 187
Chapter 7 Mixing 192
7.1 Introduction 192
7.2 Mixing of fluids (blending) 192
7.2.1 Types of blenders 192
7.2.2 Flow patterns in fluid mixing 194
7.2.3 Energy input in fluid mixing 195
7.3 Kneading 198
7.4 In-flow mixing 201
7.5 Mixing of particulate solids 201
7.5.1 Mixing and segregation 201
7.5.2 Quality of mixing, the concept of 'mixedness' 201
7.5.3 Equipment for mixing particulate solids 204
7.6 Homogenization 206
7.6.1 Basic principles 206
7.6.2 Homogenizers 208
Chapter 8 Filtration 212
8.1 Introduction 212
8.2 Depth filtration 213
8.3 Surface (barrier) filtration 215
8.3.1 Mechanisms 215
8.3.2 Rate of filtration 216
8.3.3 Optimization of the filtration cycle 221
8.3.4 Characteristics of filtration cakes 222
8.3.5 The role of cakes in filtration 223
8.4 Filtration equipment 224
8.4.1 Depth filters 224
8.4.2 Barrier (surface) filters 224
8.5 Expression 228
8.5.1 Introduction 228
8.5.2 Mechanisms 228
8.5.3 Applications and equipment 230
Chapter 9 Centrifugation 234
9.1 Introduction 234
9.2 Basic principles 235
9.2.1 The continuous settling tank 235
9.2.2 From the settling tank to the tubular centrifuge 237
9.2.3 The baffled settling tank and the disc-bowl centrifuge 240
9.2.4 Liquid–liquid separation 241
9.3 Centrifuges 243
9.3.1 Tubular centrifuges 244
9.3.2 Disc-bowl centrifuges 245
9.3.3 Decanter centrifuges 247
9.3.4 Basket centrifuges 247
9.4 Cyclones 248
Chapter 10 Membrane processes 250
10.1 Introduction 250
10.2 Tangential filtration 251
10.3 Mass transfer through MF and UF membranes 252
10.3.1 Solvent transport 252
10.3.2 Solute transport sieving coefficient and rejection
10.3.3 Concentration polarization and gel polarization 255
10.4 Mass transfer in reverse osmosis 258
10.4.1 Basic concepts 258
10.4.2 Solvent transport in reverse osmosis 259
10.5 Membrane systems 262
10.5.1 Membrane materials 262
10.5.2 Membrane configurations 264
10.6 Membrane processes in the food industry 266
10.6.1 Microfiltration 266
10.6.2 Ultrafiltration 266
10.6.3 Nanofiltration and reverse osmosis 268
10.7 Electrodialysis 270
Chapter 11 Extraction 276
11.1 Introduction 276
11.2 Solid–liquid extraction (leaching) 278
11.2.1 Definitions 278
11.2.2 Material balance 279
11.2.3 Equilibrium 279
11.2.4 Multistage extraction 279
11.2.5 Stage efficiency 283
11.2.6 Solid–liquid extraction systems 285
11.3 Supercritical fluid extraction 288
11.3.1 Basic principles 288
11.3.2 Supercritical fluids as solvents 289
11.3.3 Supercritical extraction systems 290
11.3.4 Applications 292
11.4 Liquid–liquid extraction 293
11.4.1 Principles 293
11.4.2 Applications 293
Chapter 12 Adsorption and ion exchange 296
12.1 Introduction 296
12.2 Equilibrium conditions 297
12.3 Batch adsorption 299
12.4 Adsorption in columns 304
12.5 Ion exchange 305
12.5.1 Basic principles 305
12.5.2 Properties of ion exchangers 306
12.5.3 Application: Water softening using ion exchange 309
12.5.4 Application: Reduction of acidity in fruit juices 310
Chapter 13 Distillation 312
13.1 Introduction 312
13.2 Vapor–liquid equilibrium (VLE) 312
13.3 Continuous flash distillation 315
13.4 Batch (differential) distillation 318
13.5 Fractional distillation 321
13.5.1 Basic concepts 321
13.5.2 Analysis and design of the column 322
13.5.3 Effect of the reflux ratio 327
13.5.4 Tray configuration 327
13.5.5 Column configuration 328
13.5.6 Heating with live steam 328
13.5.7 Energy considerations 329
13.6 Steam distillation 330
13.7 Distillation of wines and spirits 331
Chapter 14 Crystallization and dissolution 334
14.1 Introduction 334
14.2 Crystallization kinetics 335
14.2.1 Nucleation 335
14.2.2 Crystal growth 337
14.3 Crystallization in the food industry 340
14.3.1 Equipment 340
14.3.2 Processes 342
14.4 Dissolution 345
14.4.1 Introduction 345
14.4.2 Mechanism and kinetics 345
Chapter 15 Extrusion 350
15.1 Introduction 350
15.2 The single-screw extruder 351
15.2.1 Structure 351
15.2.2 Operation 352
15.2.3 Flow models, extruder throughput 354
15.2.4 Residence time distribution 357
15.3 Twin-screw extruders 357
15.3.1 Structure 357
15.3.2 Operation 359
15.3.3 Advantages and shortcomings 360
15.4 Effect on foods 360
15.4.1 Physical effects 360
15.4.2 Chemical effect 361
15.5 Food applications of extrusion 362
15.5.1 Forming extrusion of pasta 362
15.5.2 Expanded snacks 362
15.5.3 Ready-to-eat cereals 363
15.5.4 Pellets 364
15.5.5 Other extruded starchy and cereal products 364
15.5.6 Texturized protein products 365
15.5.7 Confectionery and chocolate 365
15.5.8 Pet foods 366
Chapter 16 Spoilage and preservation of foods 368
16.1 Mechanisms of food spoilage 368
16.2 Food preservation processes 368
16.3 Combined processes (the 'hurdle effect') 370
16.4 Packaging 370
Chapter 17 Thermal processing 372
17.1 Introduction 372
17.2 The kinetics of thermal inactivation of microorganisms and enzymes 373
17.2.1 The concept of decimal reduction time 373
17.2.2 Effect of the temperature on the rate of thermal destruction/inactivation 375
17.3 Lethality of thermal processes 377
17.4 Optimization of thermal processes with respect to quality 380
17.5 Heat transfer considerations in thermal processing 381
17.5.1 In-package thermal processing 381
17.5.2 In-flow thermal processing 386
Chapter 18 Thermal processes, methods and equipment 392
18.1 Introduction 392
18.2 Thermal processing in hermetically closed containers 392
18.2.1 Filling into the cans 393
18.2.2 Expelling air from the head-space 395
18.2.3 Sealing 396
18.2.4 Heat processing 397
18.3 Thermal processing in bulk, before packaging 403
18.3.1 Bulk heating – hot filling – sealing – cooling in container 403
18.3.2 Bulk heating – holding – bulk cooling – cold filling – sealing 403
18.3.3 Aseptic processing 405
Chapter 19 Refrigeration, chilling and freezing 408
19.1 Introduction 408
19.2 Effect of temperature on food spoilage 409
19.2.1 Temperature and chemical activity 409
19.2.2 Effect of low temperature on enzymatic spoilage 412
19.2.3 Effect of low temperature on microorganisms 413
19.2.4 Effect of low temperature on biologically active (respiring) tissue 415
19.2.5 The effect of low temperature on physical properties 416
19.3 Freezing 417
19.3.1 Phase transition, freezing point 418
19.3.2 Freezing kinetics, freezing time 419
19.3.3 Effect of freezing and frozen storage on product quality 425
Chapter 20 Refrigeration, equipment and methods 430
20.1 Sources of refrigeration 430
20.1.1 Mechanical refrigeration 430
20.1.2 Refrigerants 435
20.1.3 Distribution and delivery of refrigeration 436
20.2 Cold storage and refrigerated transport 437
20.3 Chillers and freezers 440
20.3.1 Blast cooling 440
20.3.2 Contact freezers 442
20.3.3 Immersion cooling 443
20.3.4 Evaporative cooling 443
Chapter 21 Evaporation 446
21.1 Introduction 446
21.2 Material and energy balance 447
21.3 Heat transfer 449
21.3.1 The overall coefficient of heat transfer U 450
21.3.2 The temperature difference T[sub(s)] – T[sub(c)] (& #916
21.4 Energy management 457
21.4.1 Multiple-effect evaporation 458
21.4.2 Vapor recompression 463
21.5 Condensers 464
21.6 Evaporators in the food industry 465
21.6.1 Open pan batch evaporator 465
21.6.2 Vacuum pan evaporator 466
21.6.3 Evaporators with tubular heat exchangers 466
21.6.4 Evaporators with external tubular heat exchangers 468
21.6.5 Boiling film evaporators 468
21.7 Effect of evaporation on food quality 471
21.7.1 Thermal effects 471
21.7.2 Loss of volatile flavor components 474
Chapter 22 Dehydration 476
22.1 Introduction 476
22.2 Thermodynamics of moist air (psychrometry) 478
22.2.1 Basic principles 478
22.2.2 Humidity 478
22.2.3 Saturation, relative humidity (RH) 479
22.2.4 Adiabatic saturation, wet-bulb temperature 479
22.2.5 Dew point 480
22.3 Convective drying (air drying) 481
22.3.1 The drying curve 481
22.3.2 The constant rate phase 484
22.3.3 The falling rate phase 487
22.3.4 Calculation of drying time 489
22.3.5 Effect of external conditions on the drying rate 492
22.3.6 Relationship between film coefficients in convective drying 493
22.3.7 Effect of radiation heating 494
22.3.8 Characteristic drying curves 494
22.4 Drying under varying external conditions 495
22.4.1 Batch drying on trays 495
22.4.2 Through-flow batch drying in a fixed bed 497
22.4.3 Continuous air drying on a belt or in a tunnel 498
22.5 Conductive (boiling) drying 498
22.5.1 Basic principles 498
22.5.2 Kinetics 499
22.5.3 Systems and applications 500
22.6 Dryers in the food processing industry 502
22.6.1 Cabinet dryers 503
22.6.2 Tunnel dryers 504
22.6.3 Belt dryers 506
22.6.4 Belt-trough dryers 506
22.6.5 Rotary dryers 507
22.6.6 Bin dryers 507
22.6.7 Grain dryers 509
22.6.8 Spray dryers 509
22.6.9 Fluidized bed dryer 514
22.6.10 Pneumatic dryer 515
22.6.11 Drum dryers 516
22.6.12 Screw conveyor and mixer dryers 517
22.6.13 Sun drying, solar drying 518
22.7 Issues in food drying technology 518
22.7.1 Pre-drying treatments 518
22.7.2 Effect of drying conditions on quality 519
22.7.3 Post-drying treatments 520
22.7.4 Rehydration characteristics 520
22.7.5 Agglomeration 521
22.8 Energy consumption in drying 521
22.9 Osmotic dehydration 524
Chapter 23 Freeze drying (lyophilization) and freeze concentration 528
23.1 Introduction 528
23.2 Sublimation of water 528
23.3 Heat and mass transfer in freeze drying 529
23.4 Freeze drying, in practice 535
23.4.1 Freezing 535
23.4.2 Drying conditions 535
23.4.3 Freeze drying, commercial facilities 535
23.4.4 Freeze dryers 536
23.5 Freeze concentration 537
23.5.1 Basic principles 537
23.5.2 The process of freeze concentration 538
Chapter 24 Frying, baking, roasting 542
24.1 Introduction 542
24.2 Frying 542
24.2.1 Types of frying 542
24.2.2 Heat and mass transfer in frying 543
24.2.3 Systems and operation 544
24.2.4 Health aspects of fried foods 545
24.3 Baking and roasting 545
Chapter 25 Ionizing irradiation and other non-thermal preservation processes 550
25.1 Preservation by ionizing radiations 550
25.1.1 Introduction 550
25.1.2 Ionizing radiations 550
25.1.3 Radiation sources 551
25.1.4 Interaction with matter 552
25.1.5 Radiation dose 554
25.1.6 Chemical and biological effects of ionizing irradiation 555
25.1.7 Industrial applications 557
25.2 High hydrostatic pressure preservation 558
25.3 Pulsed electric fields (PEF) 559
25.4 Pulsed intense light 559
Chapter 26 Food packaging 562
26.1 Introduction 562
26.2 Packaging materials 563
26.2.1 Introduction 563
26.2.2 Materials for packaging foods 565
26.2.3 Transport properties of packaging materials 568
26.2.4 Optical properties 570
26.2.5 Mechanical properties 571
26.2.6 Chemical reactivity 572
26.3 The atmosphere in the package 573
26.3.1 Vacuum packaging 573
26.3.2 Controlled atmosphere packaging (CAP) 574
26.3.3 Modified atmosphere packaging (MAP) 574
26.3.4 Active packaging 574
26.4 Environmental issues 575
Chapter 27 Cleaning, disinfection, sanitation 578
27.1 Introduction 578
27.2 Cleaning kinetics and mechanisms 579
27.2.1 Effect of the contaminant 579
27.2.2 Effect of the support 581
27.2.3 Effect of the cleaning agent 581
27.2.4 Effect of the temperature 583
27.2.5 Effect of mechanical action (shear) 583
27.3 Kinetics of disinfection 584
27.4 Cleaning of raw materials 585
27.5 Cleaning of plants and equipment 587
27.5.1 Cleaning out of place (COP) 587
27.5.2 Cleaning in place (CIP) 587
27.6 Cleaning of packages 588
27.7 Odor abatement 588
Appendix 592
Table A.1 Common conversion factors 593
Table A.2 Typical composition of selected foods 594
Table A.3 Viscosity and density of gases and liquids 595
Table A.4 Thermal properties of materials 595
Table A.5 Emissivity of surfaces 596
Table A.6 US standard sieves 596
Table A.7 Properties of saturated steam – temperature table 597
Table A.8 Properties of saturated steam – pressure table 598
Table A.9 Properties of superheated steam 598
Table A.10 Vapor pressure of liquid water and ice below 0°C 599
Table A.11 Freezing point of ideal aqueous solutions 600
Table A.12 Vapor–liquid equilibrium data for ethanol–water mixtures at 1 atm 600
Table A.13 Boiling point of sucrose solutions at 1 atm 601
Table A.14 Electrical conductivity of some materials 601
Table A.15 Thermodynamic properties of saturated R-134a 601
Table A.16 Thermodynamic properties of superheated R-134a 602
Table A.17 Properties of air at atmospheric pressure 603
Figure A.1 Friction factors for flow in pipes 604
Figure A.2 Psychrometric chart 604
Figure A.3 Mixing power function, turbine impellers 605
Figure A.4 Mixing power function, propeller impellers 605
Figure A.5 Unsteady state heat transfer in a slab 606
Figure A.6 Unsteady state heat transfer in an infinite cylinder 606
Figure A.7 Unsteady state heat transfer in a sphere 607
Figure A.8 Unsteady state mass transfer, average concentration 607
Figure A.9 Error function 608
Index 610
A 610
B 610
C 610
D 611
E 612
F 612
G 613
H 614
I 614
J 614
K 614
L 614
M 614
N 615
O 615
P 615
R 616
S 617
T 617
U 618
V 618
W 618
Y 618
Series List 620