Contributors xiii

About the editor xv

Preface xvii

Acknowledgments xix

1 Introduction to Drying 1
C. Anandharamakrishnan

1.1 Introduction 1

1.2 Fundamental principles of drying: the concept of simultaneous heat and mass transfer 2

1.2.1 Heat transfer during the drying process 2

1.2.1.1 Conduction drying 3

1.2.1.2 Convection drying 4

1.2.1.3 Radiation and dielectric drying 5

1.2.2 Mass transfer during the drying process 6

1.2.2.1 Diffusion mechanism 7

1.2.2.2 Capillary mechanism 8

1.3 The drying curve 9

1.4 Stages of drying 9

1.4.1 Constant rate period 10

1.4.2 Falling rate period 11

1.5 Techniques for the drying of dairy products 12

1.6 Conclusion 13

References 13

2 Dried Dairy Products and their Trends in the Global Market 15
Aadinath, T. Ghosh, P.H. Amaladhas and C. Anandharamakrishnan

2.1 Introduction 15

2.2 Milk powders and dried milk products 16

2.2.1 Primary dairy powders 16

2.2.2 Secondary dairy powders 16

2.3 World market dynamics 18

2.3.1 Production 18

2.3.1.1 Oceania 18

2.3.1.2 India 20

2.3.1.3 European Union 20

2.3.1.4 Argentina 20

2.3.2 Consumption 20

2.3.2.1 Algeria 20

2.3.2.2 Indonesia 21

2.3.2.3 China 21

2.3.2.4 Mexico 21

References 21

3 Techniques for the Preconcentration of Milk 23
I. Roy, A. Bhushani and C. Anandharamakrishnan

3.1 Introduction 23

3.2 Need for preconcentration 23

3.2.1 Skim milk 24

3.2.2 Whey powders and infant formula 24

3.3 Concentration methods 25

3.4 Thermal methods 25

3.4.1 Evaporation 25

3.4.1.1 Single-effect recirculation evaporator 25

3.4.1.2 Multiple-effect evaporator 26

3.4.1.3 Falling-film evaporator 27

3.4.1.4 Plate evaporator 28

3.4.1.5 Horizontal tube evaporator 30

3.4.1.6 Mechanical film evaporator 30

3.4.1.7 Low-temperature evaporator 30

3.5 Non-thermal methods 30

3.5.1 Freeze concentration 30

3.5.2 Membrane separation techniques 32

3.5.2.1 Microfiltration 34

3.5.2.2 Ultrafiltration 35

3.5.2.3 Reverse osmosis 37

3.6 Conclusion 37

References 37

4 Drum Drying 43
P. Karthik, N. Chhanwal and C. Anandharamakrishnan

4.1 Introduction 43

4.2 Drum-drying process 44

4.2.1 Effect of operating parameters on product quality and the capacity of the drum dryer 45

4.3 Types of drum dryers 46

4.3.1 Single-drum dryers 46

4.3.2 Double-drum dryers 47

4.3.3 Twin-drum dryers 47

4.3.4 Vacuum-drum dryers 48

4.3.5 Enclosed-drum dryers 49

4.4 Classification of the feeding method 49

4.4.1 Single- and multiple-roll feed 49

4.4.2 Nip feed 49

4.4.3 Dip feed 49

4.4.4 Spray feed 49

4.4.5 Splash feed 50

4.5 Operating parameters 51

4.5.1 Important operational conditions in the drum drying of milk 52

4.6 Advantages and disadvantages of drum/roller drying 54

4.7 Conclusion 54

References 55

5 SprayDrying 57
S. Padma Ishwarya and C. Anandharamakrishnan

5.1 Introduction 57

5.2 Spray drying: principle of operation 57

5.2.1 Atomization 59

5.2.1.1 Rotary atomizers 60

5.2.1.2 Pressure nozzle atomizers 62

5.2.1.3 Twin-fluid atomizers 62

5.2.1.4 Monodisperse droplet generators 63

5.2.2 Droplet–drying air interaction and moisture evaporation 65

5.2.3 Particle separation 72

5.3 Characteristics of spray-dried dairy powders 74

5.3.1 Rehydration 74

5.3.2 Particle size and shape parameters 75

5.4 Handling spray-drying processing problems 77

5.4.1 Stickiness 77

5.4.2 Thermal denaturation of proteins 79

5.5 Applications of spray drying for the production of dried milk and milk products 79

5.6 Conclusion 84

References 88

6 Freeze Drying 95

A. Bhushani and C. Anandharamakrishnan

6.1 Introduction 95

6.2 Steps in freeze drying 95

6.2.1 Freezing 96

6.2.2 Primary or sublimation drying 99

6.2.3 Secondary or desorption drying 100

6.3 Merits of freeze drying over other drying techniques 100

6.4 Heat and mass transfer in freeze drying 101

6.5 Freeze-drying equipment 103

6.6 Properties influencing the freeze drying of dairy products 106

6.6.1 Milk 106

6.6.2 Lactose 109

6.7 Preservation of kefir culture by freeze drying 111

6.8 Microencapsulation of probiotics by freeze drying 112

6.8.1 Probiotics 112

6.8.2 Need for microencapsulation 113

6.8.3 Cell viability issues associated with freeze drying 113

6.8.4 Characteristics of microencapsulated probiotic cells 114

6.9 Conclusion 115

References 117

7 Spray Freeze Drying 123
S. Padma Ishwarya, C. Anandharamakrishnan and A.G.F. Stapley

7.1 Introduction 123

7.2 SFD process 124

7.2.1 Atomization 125

7.2.2 Freezing 126

7.2.2.1 Spray freezing into vapour 127

7.2.2.2 Spray freezing into vapour over liquid 127

7.2.2.3 Spray freezing into liquid 129

7.2.3 Freeze drying 130

7.2.3.1 Vacuum freeze drying 130

7.2.3.2 Atmospheric SFD and atmospheric spray fluidized-bed freeze drying 131

7.2.3.3 Sub-atmospheric pressure SFD 132

7.3 Applications of SFD in dried dairy products 132

7.3.1 SFD of whole milk and skim milk 133

7.3.2 SFD of whey protein 135

7.3.3 SFD for microencapsulation of probiotics 140

7.4 Advantages and limitations of SFD 144

7.5 Conclusion 144

References 144

8 Optimization of Dairy Product Drying Processes 149
S. Parthasarathi and C. Anandharamakrishnan

8.1 Introduction 149

8.2 Experimental design tools for process optimization 149

8.2.1 Response surface methodology 149

8.2.1.1 Advantages of RSM 151

8.2.1.2 Limitations of RSM 151

8.2.2 Artificial neural networks 151

8.2.2.1 Feed-forward neural network 152

8.2.2.2 Learning process of an ANN 153

8.2.2.3 Optimization of process parameters 154

8.2.3 Finite element and finite volume methods 154

8.2.3.1 Finite element method 155

8.2.3.2 Finite volume method 155

8.3 Drying process variables and their influence on process and product quality 156

8.3.1 Drum drying 157

8.3.1.1 Heat and mass transfer 157

8.3.2 Spray drying 158

8.3.2.1 Exergy efficiency 160

8.3.2.2 Atomization 160

8.3.3 Freeze drying 161

8.3.3.1 Temperature measurement 162

8.3.3.2 Computational modelling 164

8.3.4 Spray freeze drying 169

8.4 Conclusion 170

References 171

9 Computational Fluid Dynamics Modelling of the Dairy Drying Processes 179
J. Gimbun,W.P. Law and C. Anandharamakrishnan

9.1 Introduction 179

9.2 Spray drying 179

9.2.1 Spray-drying process 179

9.2.2 Flow field simulation 180

9.2.2.1 Steady or unsteady approach 181

9.2.2.2 Turbulence modelling 182

9.2.3 Discrete phase modelling 183

9.2.4 Wall deposition and the particle build-up model 186

9.2.5 Particle interaction 186

9.2.6 Validation and issues of CFD simulation 189

9.3 Freeze drying 189

9.3.1 Modelling of freeze drying 190

9.3.1.1 Mass and heat-transfer modelling 190

9.3.1.2 Primary drying modelling 191

9.3.1.3 Secondary drying modelling 192

9.4 Spray freeze drying 193

9.5 Conclusions and future scope 196

References 196

10 Physicochemical and Sensory Properties of Dried Dairy Products 203
P.H. Amaladhas and F. Magdaline Eljeeva Emerald

10.1 Introduction 203

10.2 Milk Powder Manufacture 203

10.2.1 Roller drying 205

10.2.2 Spray drying 206

10.2.3 Freeze drying 208

10.2.4 Spray freeze drying 208

10.3 Properties of dairy powders as influenced by drying method 208

10.4 Physical properties 209

10.4.1 Morphology, particle size, shape and distribution 209

10.4.2 Density 210

10.4.3 Reconstitution properties 213

10.4.4 Agglomeration and instantization 216

10.4.5 Flowability and stickiness 216

10.4.6 Heat and coffee stability 217

10.5 Chemical and sensory properties 218

10.5.1 Protein quality 218

10.5.2 Non-enzymatic browning 219

10.5.3 Oxidation and chemical quality 219

10.5.4 Sensory quality 220

10.6 Properties of special powders 220

10.6.1 Whey powders 220

10.6.2 Whey protein concentrates 221

10.6.3 Cheese powder 221

10.6.4 Yoghurt powder 222

10.6.5 Infant milk powders 222

10.6.6 Dairy whiteners 223

10.7 Conclusion 223

References 223

11 Packaging of Dried Dairy Products 229
R. Gopirajah and C. Anandharamakrishnan

11.1 Introduction 229

11.2 Dairy packaging trends 230

11.3 Forms of packaging materials 231

11.3.1 Metal cans 232

11.3.2 Glass bottles 232

11.3.3 Stretch-wrap packaging 232

11.3.4 Flexible pouches 232

11.3.5 Bag-in-box packages 233

11.3.6 Cups 233

11.3.7 Paper-board containers 233

11.4 Packaging of dried milk products 234

11.4.1 Packaging of whole milk powder 235

11.4.2 Packaging of non-fat dried milk powder 236

11.5 Developments in packaging techniques 237

11.5.1 Intelligent packaging 237

11.5.2 Active packaging 238

11.5.2.1 Migration mechanism in active packaging 239

11.5.2.2 The use of scavengers (absorbers) to prevent lipid oxidation 239

11.5.3 Nanotechnology in dairy packaging 240

11.5.3.1 Bionanocomposites and their applications 241

11.5.3.2 Modelling the barrier properties of polymer-clay nanocomposites 242

11.6 Conclusion 244

References 244

12 Recent Advances in the Drying of Dairy Products 249
M.W.Woo

12.1 Introduction 249

12.2 Typical layout of a dairy spray-drying process 250

12.2.1 Multistage drying process 250

12.2.2 Some unique process layouts 251

12.3 Advances in operating spray dryers 252

12.3.1 Controlling the drying process 252

12.3.1.1 Single droplet to dryer-wide prediction 252

12.3.2 Controlling powder stickiness and deposition 259

12.4 Advances in operating fluidized-bed dryers 261

12.4.1 Controlling crystallization 261

12.4.2 Controlling agglomeration 262

12.5 Conclusion 263

References 263

13 Industrial Scale Drying of Dairy Products 269
D. Anand Paul

13.1 Introduction 269

13.2 Process flow in a dairy drying plant 270

13.3 Lexicon of industrial-scale drying 272

13.4 Industrial spray drying of dairy products 273

13.4.1 Automation of industrial-scale spray dryers 273

13.4.2 Efficiency of spray-dryer operation 274

13.4.3 Bottlenecks in industrial spray-drying 276

13.4.4 Hygiene in spray-dryer operation 277

13.4.5 Safety aspects of spray drying 278

13.5 Industrial drum drying of dairy products 279

13.5.1 Critical control points in industrial drum drying 280

13.5.2 Energy efficiency of drum drying 282

13.5.3 Safe operation of drum dryers 283

13.6 Conclusion 283

References 283

14 Challenges Involved in the Drying of Dairy Powders 287
U. Kiran Kolli

14.1 Introduction 287

14.2 Challenges in the drying of dairy powders 288

14.2.1 Fouling 288

14.2.1.1 Mechanisms 288

14.2.1.2 Factors affecting fouling 289

14.2.2 Stickiness 291

14.2.3 Fires and explosions 292

14.2.4 Powder loss 293

14.2.5 Transport of powder 293

14.2.6 Storage of dairy powders 294

14.2.7 Plant economics 294

14.2.8 Development of speciality dairy powders 294

14.3 Use of modelling as a tool to solve some challenges 295

14.4 Conclusion 296

References 296

Index 301