Contents
Preface ........................................................... xi
1 Separation processes - an overview .................................. 1
1.1 Foods - the raw material ... ............................... 1
1.2.1 Introduction ...... ............................... 5
1.2.2 Separations from solids .......................................
Separation from the solid matrix ............................ 9
1.2.3 Separations from liquids ..................................... 10
Liquid-solid separations ................................... 10
Immiscible liquids ........................................ 11
General liquid separation processes ...........................
1.2.4 Separations from gases and vapours ............................ 13
1.3 Water treatment ................................................. 15
1.4 References ..................................................... 15
A . S . Grandison and M . J . Lewis
1.2 Separation techniques ... ............................... 5
7
Solid-solid separations ................................. 8
11
2 Supercritical fluid extraction and its application in the food industry ....
D . Steytler
17
2.1 Introduction ................. ............................... 17
2.2 The supercritical fluid state ..... ............................... 18
2.2.1 Physical properties of NCF CO, ............................... 20
Density ................................................ 20
Viscosity ............................................... 21
Diffusion ............................................... 22
Volatility (vapour pressure) ................................. 23
Chemical properties ...................................... 23
Biochemical properties ............................... 24
vi Contents
2.3 Properties of NCF solutions ....................................... 24
2.3.1 Solubilities in NCFs ........................................ 24
General principles ........................................ 25
Effect of molecular structure .............................. 25
Effect of temperature and pressure ......................... 28
2.3.2 Theoretical models (equations of state (EOS)) ..................... 28
Entrainers ............................................... 34
2.3.3 Diffusion coefficients ........................................ 35
2.4 Factors determining the efficiency of NCF extraction ................... 36
2.4.1 Extraction stage ............................................ 37
Mechanism of extraction ................................... 37
The ‘free diffusion’ model ................................ 38
The ‘shrinking core’ model ............................... 38
Solubility ............. ............................... 40
Diffusion coefficient ...................................... 40
Adsorption .............................................. 40
The role of water ......................................... 41
2.4.2 Separation stage ............................................ 42
Equipment and experimental techniques used in NCF extraction and
fractionation ................................................... 44
2.5.1 Extraction ............... ........................
Pilot plants with recirculati ............................... 44
Small pilot plant with total loss of COZ
2.5.2 Fractionation .............................................. 46
2.5
...
Cascades of separation vessels ....................
Zosel’s ‘hot finger’ fractionation column
2.6 Applications ..............................................
...................
2.6.1 Decaffeination of coffee and tea ............................... 49
2.6.2 Seed oil extraction .......................................... 51
2.6.3 Purification of lecithin ....................................... 52
2.6.4 Lowering cholesterol levels in foods ............................ 53
2.6.5 Fractionation of high-value oils and fats ......................... 53
Butterfat ................................................ 53
Fish oils ................. ............................ 54
2.6.6 Extraction of flavours and fragrances ........................... 54
2.7 References ..................................................... 57
3 Pressure-activated membrane processes ............................ 65
3.1 Introduction .................................................... 65
3.2 Terminology .................................................... 66
3.3 Concentration factor and rejection .................................. 69
3.4 Membrane characteristics ......................................... 70
3.5 Permeate rate ................................................... 71
3.6 Transport phenomena and concentration polarisation ................... 72
M . J . Lewis
Contents vii
3.7 Membrane equipment ............................................ 75
3.7.1 Membrane configuration ..................................... 76
3.8 Safety and hygiene considerations .................................. 82
3.9 Reverse osmosis applications .................................... 86
3.9.1 Introduction ............................................... 86
3.9.2 Water treatment ............................................ 87
3.9.3 Milk processing ............................................ 88
3.9.4 Fruit and vegetable juices .................................... 90
3.9.5 Other applications ..... ........................... 91
3.10 References ................ .....................
4 Ultrafiltration .................................................. 97
4.2 Processing characteristics ......................................... 98
4.2.1 Rejection or retention factors ................................. 98
4.2.2 Yield ................ ................................. 101
4.2.4 Practical rejection data ...................................... 104
4.3 Performance of ultrafiltration systems ............................... 105
Permeateflux ............................................ 105
4.3.1 Transport phenomena and concentration polarisation .......... . 106
4.3.2 Fouling ................ ........................... 111
4.3.3 Factors affecting flux ... ............................... 114
Energy input ....... ........................... 114
4.4 Diafiltration .................................................... 116
Introduction ............................................. 116
116
Washing-in ............................................. 118
M . J . Lewis
4.1 Introduction .................................................... 97
4.2.3 Average rejection ...... ................................. 103
4.4.1 Washing out at constant volume
4.4.2 Diafiltration applications ... ............................ 119
...............................
4.4.3 Protein fractionation .............................
4.5.1 Dairy applications . . ...........................
4.5 Ultrafiltration applications ... ... ...............
4.5.2 Oilseed and vegetable proteins ............................ 125
4.5.3 Animal products ........................................... 127
4.5.4 Biotechnology applications ................................... 128
Membrane-based bioreactors ............................... 128
Enzyme reactors ......................................... 128
Membrane fermenters ..................................... 131
Recovery of components and downstream processing ............ 132
133
4.6 References ..................................................... 134
4.5.5 Medical applications: serum fractionation .........................
viii Contents
5 Microfiltration , . , . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
A. S. Grandison and T. J. A. Finnigan
5.1 Introduction .................................................... 141
5.2 Theory, materials and equipment . . . . . . . . . . . . . . . . . . . . . . . , , , . . . , . . . . . 141
5.2.1 Membrane configurations and characteristics . . . . . . . . , , , , , . . . . . . . . 142
5.2.2 Performance of microfiltration systems and membrane fouling . . . . . . . 146
Applications in the food and biotechnology industries . . . . , . . . , . . . . . . . . . . 148
5.3.1 Food industry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I . . . . . . . 148
5.3.2 Applications for biotechnology . .......................... 150
152
Ion-exchange and electrodialysis.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
A. S. Grandison
Ion-exchange . . . . . . . . . . . . . . . . . . . . ......................... 155
6.1.1 Theory, materials and equipment
155
158
5.3
5.4 Conclusions ............... . . . . . . ........ ......... 151
5.5 References . . . . . . . . . . . .......................
6
6.1
Solute/ion-exchanger interactions . . . . . , , . . . . . . . . . . . . . . . . . . . .
Ion-exchange groups . . . . . . . . . . . . . , , , , . . . . . . . . . . . . . . . . . . . . .
Ion-exchange materials . . . . . . . . . . . . . . . . . . . . . . . . .
.......................
....................
Elution ................................................. 159
160
Mixed bed systems . . . ............................... 160
Stirredtanks ............................................ 160
160
Softening ............................................... 161
Demineralisation 16 1
Decolorisation . . . . . ............................
Protein purification . . . ................................ 163
Purification of other compounds . . . . . . . . . . . , . . . . . . . . .
Electrodialysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ........ 166
6.2.1 Theory and equipment . . . . . . . ...................... 167
6.2.2 Applications of ED in the food an
6.3 References . . . . . . . . . . . . . . . . . . . . . .
7 Innovative separation methods in bioprocessing . . . . . . . . . . . . . . . . . . . . . 179
J. A. Asenjo and J. B. Chaudhuri
7.1 Introduction .................................................... 179
7.2 System characteristics . . . . . . . . . . . . , . . , . . . . . . . , . . . . . . , , . . . . . . . . . . . .
180
7.2.1 Physicochemical basis for separation operations . . . . . . , , , . . . . . . . . . , 180
7.2.2 Kinetics and mass transfer . . . . . . . . . . . . . . . , . . . . . , , . . . . . . . . . . . . . 18 1
Liquid-liquid extraction: introduction , . , , , . . . . . . . . . . . , . . . . . . . . . . . . . . , 181
7.3.1 Aqueous two-phase separation . . . . . . . . . . , . . . . . . . . . . , . . . . , 182
7.3.2 Reverse micelle extraction . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . 185
Ion-exchange columns .........................
6.1.2 Applications of ion-exchange in the food and biotechnology industries
. . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . .
6.2
7.3
Contents ix
7.3.3 Perfluorocarbon affinity separations ..............
...........
7.4.1 Adsorption system
7.4.2 Continuous adsorption recycle extraction. ........
7.4.3 Membrane chromatography .............................
7.4.4 Chromatographic and adsorption materials ........ 201
7.5 Other developments ......... ..........
7.5.1 Electrically enhanced separations ... .................. 202
.................
............. 204 7.6 References ............
.......................... 8 Fractionation of fat .................. , 207
K. K. Rajah
8.1 Introduction .................... ................
.......... ........... 210
8.2 Dry fractionation ................ ................ 211
8.2.1 Flat-bed vac ....................
Vacuband batch filter. ....................
8.2.2 Rotary drum filters ................. .............. 215
8.2.3 Membrane filters ...... ...............
Low pressure ............. ...................
........ 224
....................
8.3 Detergent fractionation ................
................ 232
8.4 Solvent fractionation ...... .............
8.5 References .................... ................ 238
9 Solids separation processes ....................................... 243
9.2 Physical properties of solids. ............ ................ 244
9.2.2 Particle size and particle size distribution ................... 247
9.2.3 Particle density .....................
9.2.4 Forces of adh ...................... 252
9.2.5 Bulk properties ...........
9.2.6 Bulk density and porosity .............
9.2.7 Flowability ..... .....................
M. J. Lewis
9.1 Introduction ..... ..............
9.2.1 Classification of powders .............
x Contents
9.3 Separation of particulates and powders ............................... 256
9.3.1 Size reduction .............................................. 256
9.4 Air classification ................................................. 260
9.4.1 Introduction ................................................. 260
9.4.2 Commercial air classifiers .................................... 262
9.4.3 Process characterisation ...................................... 264
9.4.4 Applications ............................................... 268
9.4.5 Cereal separations .......................................... 268
9.4.7 Other applications .......................................... 273
9.5 Wet separation processes .......................................... 273
9.3.2 Sieving ................................................... 258
9.4.6 Legumes .................................................. 270
9.5.1 Protein recovery ..........
9.5.2 Soya processing .........................
9.5.3 Wheat protein ....................................
9.5.4 Other applications ................
Some miscellaneous solids separations .........................
9.6.3 Cleaning of raw materials .....................................
9.6.4 Sorting and grading .........................................
Colour sorting and grading .................................
9.6
9.6.1 Dehulling ...........................................
9.6.2 Peeling ................................................... 279
279
281
281
9.7 References ..................................................... 283
Index .............................................................. 287
