Contents Preface 1 Separation processes- an overview S. Grandison and M. J. Lewis 1.1 Foods the raw material 1.2 Separation techniques 1.2.1 Introduction 1.2.2 Separations from solids Solid-solid separations 55789 Separation from the solid matrix 1.2.3 Separations from liquid 10 Immiscible liquids General liquid separation processes 1. 2. 4 Separations from gases and vapours 13 1.3 Water treatment 1.4 References 15 2 Supercritical fluid extraction and its application in the food industry D. Steytler 2.1 Introduction 2.2 The supercritical fluid state 2.2. 1 Physical properties of NCF CO2 ens Viscosity ,., Diffusion Volatility(vapour pressure) Chemical properties 22222 Biochemical pro
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
i Contents 2.3 Properties of NCF solutions 24 2.3.1 Solubilities in NCFs General principles Effect of molecular structure Effect of temperature and pressure 2.3.2 Theoretical models (equations of state(EOs)) Entrainers 2.3, 3 Diffusion coefficients 2.4 Factors determining the efficiency of NCF extraction 36 2. 4. 1 Extraction stage Mechanism of extractio The‘ free diffusion’ model,,,,, 38 The‘ shrinking core’ model,, Diffusion coefficient 40 Adsorption The role of water 2.4.2 Separation stage 2.5 Equipment and experimental techniques used in NCF extraction and 2.5.1 Extraction Pilot plants with recirculation Small pilot plant with total loss of CO? 2.5.2 Fractionation Cascades of separation vessels Zosel's 'hot finger'fractionation column 2.6 Applications 2.6.1 Decaffeination of coffee and 2.6.2 Seed oil extraction 2.6.3 Purification of lecithin 2.6. 4 Lowering cholesterol levels in foods 2.6.5 fractionation of high-value oils and fats 53 Butterfat 2.6.6 Extraction of flavours and fragrances 54 2. 7 Reference Pressure-activated membrane processes M.J. Lewis 3.1 Introduction 3.2 Terminology 3.3 Concentration factor and rejection 3.4 Membrane characteristics 3.5 Permeate rate 660012 3.6 Transport phenomena and concentration polarisation
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 3.7.1 Membrane configuration 3.8 Safety and hygiene considerations 3.9 Reverse osmosis applications 6266 3.9.1 Introduction 3.9.2 Water treatment 39.3 Milk processing… 3.9.4 Fruit and vegetable juices 90 3.9.5 Other applications 3. 10 References Ultrafiltration M. J. Lewis 4. 1 Introduction 4.2 Processing characteristics 4.2. 1 Rejection or retention factors 98 4.2.2 Yield 4.2.3 Average rejection.... 103 4.2.4 Practical rejection data 4.3 Performance of ultrafiltration systems Permeate flux 105 4.3. 1 Transport phenomena and concentration polarisation 4.3.2 Fouling 111 4.3.3 Factors affecting flu 114 Energy input 4. 4 Diafiltration 116 Introduction 4. 4. 1 Washing out at constant volume 116 Washing-in 118 4.4.2 Diafiltration applications 4.4.3 Protein fractionation 119 4.5 Ultrafiltration applications 4.5.1 Dairy applications 4.5.2 Oilseed and vegetable proteins 125 4.5.3 Animal products 4.5.4 Biotechnology applications 128 Membrane-based bioreactors reactors Membrane fermenters 131 Recovery of components and downstream processing 132 4.5.5 Medical applications: serum fractionation 133 4.6 References 134
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
vili Contents 5 Microfiltration .................................................141 A.S. Grandison and T J. A Finnigan 5.1 Introduction 5.2 Theory, materials and equipment 5. 2.1 Membrane configurations and characteristics ,142 5.2.2 Performance of microfiltration systems and membrane foulit 5.3 Applications in the food and biotechnology industries 5.3. 1 Food industry 5.3.2 Applications for biotechnology 5.4 Conclusions B052 5.5 References 6 lon-exchange and electrodialysis.,... 155 A. S. Grandison 6.1 Ion-exchange 6.1.1 Theory, materials and equipment 55 Solute/ion-exchanger interactions Ion-exchange groups,,,,, Ion-exchange materials Capacity 159 Blinding and fouling 159 Elution lon-exchange columns Mixed bed systems 160 Stirred tanks 6.1.2 Applications of ion-exchange in the food and biotechnology industries 160 Demineralisation 161 Decolorisation l63 Protein purification Purification of other compounds 166 6.2 Electrodialysis 6.2.1 Theory and equipment 167 6.2.2 Applications of ED in the food and biotechnology industries 69 6.3 References .173 7 Innovative separation methods in bioprocessing 179 J. A. Asenjo and J B Chaudhuri 7.1 Introduction 179 7.2. 1 Physicochemical basis for separation operations 7.2 System characteristics... 7.2.2 Kinetics and mass transfer 181 7.3 Liquid-liquid extraction: introduction 7.3. 1 Aqueous two-phase separation 18 7.3.2 Reverse micelle extraction
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
7.3.3 Perfluorocarbon affinity separations 7.3.4 Liquid membrane separations 7.4 Solid-based separations 7.4.1 Adsorption systems: expanded bed adsorption 195 7.4.2 Continuous adsorption recycle extraction 7.4.3 Membrane chromatography 7.4.4 Chromatographic and adsorption material 201 7.5 Other developments 7.5.1 Electrically enhanced separations 202 7.5.2 Genetic approaches to protein purification 7.5.3 Purification of intracellular proteins 7.6 References 8 Fractionation of fat 8.1 Introductio 207 8. 1. 1 Crystallisation: nuclei formation and crystal growth 209 1. 2 Polymorphis 210 8.1.3 Quality of edible oils 210 8.2 Dry fractionation 211 8.2.1 Flat-bed vacuum band filter 213 Florentine co s filter Vacuband bat 214 8.2.2 Rotary drum filters 215 8.2.3 Membrane filters High pressure Hydrofilter press 225 8.3 Detergent fractionation 8.3. 1 The Lipofrac process 232 8.3.2 Crystallisation 232 8.4 Solvent fractionate 8.5 References 238 9 Solids separation processes 9.1 Introduction 243 9.2 Physical properties of solids I of powde 246 9.2.2 Particle size and particle size distribution 247 9.2 4 Forces of adhesion 2.5 Bulk properties 9.2. 6 Bulk density and porosity 9.2.7 Flowability
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 ................. 7.6 References ............ ............. 204 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
9.3 Separation of particulates and powders 9.3.1 Size reduction 9.3.2 Sieving 258 9.4 Air classification 9.4.1 Introduction 260 9.4.2 Commercial air classifiers 9.4.3 Process characterisation 9.4.4 Applications 268 9.4.5 Cereal separations 268 9.4.6 Legumes 270 9. 4.7 Other applications 273 9.5 Wet separation processes 273 9.5.1 Protein recovery 274 9.5.2 Soya processing 27 9.5.3 Wheat protein 276 9.5.4 Other applications 277 9.6 Some miscellaneous solids separations 278 9.6.1 Dehulling 278 9.6.2 Peeling 279 9.6.3 Cleaning of raw materials 9.6.4 Sorting and grading 281 Colour sorting and grading 281 9.7 References Index ……………287
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
