Spray Drying Techniques for Food Ingredient Encapsulation Institute of Food Technologists Series

Spray drying is a well-established method for transforming liquid materials into dry powder form. Widely used in the food and pharmaceutical industries, this technology produces high quality powders with low moisture content, resulting in a wide range of shelf stable food and other biologically significant products. Encapsulation technology for bioactive compounds has gained momentum in the last few decades and a series of valuable food compounds, namely flavours, carotenoids and microbial cells have been successfully encapsulated using spray drying.

Spray Drying Technique for Food Ingredient Encapsulation provides an insight into the engineering aspects of the spray drying process in relation to the encapsulation of food ingredients, choice of wall materials, and an overview of the various food ingredients encapsulated using spray drying. The book also throws light upon the recent advancements in the field of encapsulation by spray drying, i.e., nanospray dryers for production of nanocapsules and computational fluid dynamics (CFD) modeling.

Addressing the basics of the technology and its applications, the book will be a reference for scientists, engineers and product developers in the industry.

About the authors xiv

Preface xv

Acknowledgments xvi

1 Introduction to spray drying 1

1.1 Introduction 1

1.2 Stage 1: Atomization 2

1.2.1 Principle of atomization 3

1.2.2 Classification of atomizers 4

1.2.2.1 Rotary atomizers 4

1.2.2.2 Pressure nozzle (or hydraulic) atomizer 6

1.2.2.3 Two-fluid nozzle atomizer 7

1.2.2.4 Ultrasonic atomizers 8

1.2.2.5 Electrohydrodynamic atomizers 9

1.3 Stage 2: Spray-air contact 11

1.4 Stage 3: Evaporation of moisture 13

1.5 Stage 4: Particle separation 15

1.5.1 Cyclone separator 15

1.5.2 Bag filter 15

1.5.3 Electrostatic precipitator 17

1.6 Morphology of spray dried particles 17

1.6.1 Skin-forming morphology with hollow internal structure 19

1.6.2 Blow-hole formation 20

1.6.3 Agglomerate 21

1.6.4 Formation of dented structure and presence of small particles within large particles 21

1.7 Spray-drying process parameters and their influence on product quality 22

1.7.1 Atomization parameters 22

1.7.1.1 Atomization pressure 22

1.7.1.2 Feed flow rate 23

1.7.1.3 Feed viscosity 23

1.7.1.4 Feed surface tension 23

1.8 Parameters of spray-air contact and evaporation 24

1.8.1 Aspirator flow rate (or speed) 24

1.8.2 Inlet temperature 24

1.8.3 Outlet temperature 25

1.8.4 Glass transition temperature (Tg) 27

1.8.5 Residence time of particles in the spray chamber 27

1.9 Types of spray dryer 27

1.9.1 Open cycle spray dryer 28

1.9.2 Closed cycle spray dryer 28

1.9.3 Semi-closed cycle spray dryer 28

1.9.4 Single-stage spray dryer 29

1.9.5 Two-stage spray dryer 29

1.9.6 Short-form 30

1.9.7 Tall-form 30

1.10 Applications and advantages of spray drying 31

References 33

2 Introduction to encapsulation of food ingredients 37

2.1 Introduction 37

2.2 Encapsulation of food ingredients 37

2.3 The core and wall for encapsulation 40

2.3.1 Carbohydrates 42

2.3.2 Proteins 42

2.3.3 Lipids 43

2.4 Encapsulation techniques 43

2.4.1 Chemical encapsulation processes 44

2.4.1.1 Coacervation 44

2.4.1.2 Inclusion complexation 45

2.4.1.3 Liposome entrapment 47

2.4.2 Mechanical or physical encapsulation processes 48

2.4.2.1 Emulsification 48

2.4.2.2 Spray chilling, spray cooling and fluidized bed drying 50

2.4.2.3 Freeze drying 50

2.4.2.4 Extrusion 52

2.4.2.5 Electrohydrodynamic technique for microencapsulation: electrospraying and electrospinning 53

2.4.2.6 Spray drying 54

2.5 The lexicon of encapsulation 59

References 60

3 Spray drying for encapsulation 65

3.1 Introduction 65

3.2 Principle of encapsulation by spray drying 65

3.3 Process steps and parameters of encapsulation by spray drying 67

3.3.1 Emulsion formation 67

3.3.1.1 Rationale of emulsification step 67

3.3.1.2 Emulsion parameters influencing encapsulation efficiency 68

3.3.2 Spray drying of emulsion 70

3.3.2.1 Atomization of the emulsion and influencing parameters 70

3.3.2.2 Drying of the emulsion droplets and influencing parameters 71

3.4 Food ingredients encapsulated by spray drying 71

3.4.1 Microorganisms 72

3.4.2 Flavors 72

3.4.3 Bioactive food components 73

References 74

4 Selection of wall material for encapsulation by spray drying 77

4.1 Introduction 77

4.2 Characteristics of wall materials for encapsulation by spray drying 77

4.2.1 Solubility 77

4.2.2 Emulsification property 78

4.2.3 Film-forming ability 78

4.2.4 Viscosity 78

4.2.5 Glass transition 79

4.2.6 Degree of crystallinity 79

4.3 Approaches to choosing wall materials for encapsulation 80

4.3.1 Estimation of drying kinetics and drying curve analysis for wall material selection 81

4.3.1.1 Isothermal drying method 81

4.3.1.2 Estimation of drying kinetics under simulated conditions of spray drying 82

4.3.2 Estimation of emulsification capacity 84

4.3.3 Analysis of viscosity and rheological characteristics of wall material dispersion 85

4.3.4 Determination of thermal properties of wall materials 86

4.4 Commonly used wall materials for encapsulation of food ingredients by spray drying 88

4.4.1 Gum Arabic 88

4.4.2 Maltodextrin 89

4.4.3 Whey protein (concentrate or isolate) 91

4.4.4 Gelatin 91

4.4.5 Sodium caseinate 92

4.4.6 Modified starches 92

4.4.7 Chitosan 93

References 98

5 Encapsulation of probiotics by spray drying 101

5.1 Introduction 101

5.2 Definition of probiotics and significance of probiotics encapsulation 101

5.3 Probiotic characteristics of importance to spray drying encapsulation 103

5.4 Criteria to decide suitability of wall material for encapsulation of probiotics 104

5.5 Selection of spray drying process parameters 106

5.5.1 Effect of atomization on probiotic cell viability 107

5.5.2 Effect of spray drying process conditions on probiotic cell survival 108

5.5.2.1 Thermal effect of spray drying process on cell viability 109

5.5.2.2 Dehydration effect of spray drying process on cell viability 112

5.6 Stability of spray dried probiotic microencapsulates to gastric environment 115

References 122

6 Encapsulation of flavors and specialty oils 126

6.1 Introduction 126

6.2 Selective diffusion theory and mechanisms of volatile retention during spray drying 127

6.3 Performance parameters of flavor encapsulation by spray drying 132

6.3.1 Encapsulation efficiency 133

6.3.1.1 Total oil analysis 133

6.3.1.2 Surface oil analysis 134

6.3.2 Lipid oxidation 134

6.3.2.1 Peroxide value determination 134

6.3.2.2 Active oxygen determination 135

6.3.3 Morphology and particle size 135

6.4 Factors influencing encapsulation of flavors and oils by spray drying 137

6.4.1 Emulsion-related factors 137

6.4.1.1 Wall material 137

6.4.1.2 Core 140

6.4.2 Spray drying-related factors 142

6.4.2.1 Atomization factors 142

6.4.2.2 Inlet and exit air temperatures 143

6.4.2.3 Feed temperature 145

References 153

7 Encapsulation of bioactive ingredients by spray drying 156

7.1 Introduction 156

7.2 Spray drying for encapsulation of polyphenols 156

7.2.1 Polyphenols and their functional properties 156

7.2.2 Rationale for encapsulation of polyphenols 157

7.2.3 Influence of core nature on encapsulation efficiency 157

7.2.4 Influence of wall material selection and spray drying

process parameters on polyphenolic core retention 157

7.3 Spray drying encapsulation of vitamins 161

7.3.1 The functional benefits of vitamins 161

7.3.2 Vitamin stability and rationale for encapsulation of vitamins 161

7.3.3 Influence of wall material and feed composition on vitamin encapsulation 162

7.3.4 Influence of spray drying process parameters on vitamin encapsulation 163

7.4 Spray drying encapsulation of carotenoids 163

7.4.1 Carotenoids and their functional significance 163

7.4.2 Rationale for encapsulation of carotenoids 165

7.4.3 Effect of wall material selection and feed composition on encapsulation of carotenoids 165

7.4.4 Effect of spray drying process conditions on encapsulation of carotenoids 167

References 176

8 Spray drying for nanoencapsulation of food components 180

8.1 Introduction 180

8.2 Introduction to food nanoparticles and nanoencapsulation 181

8.3 Nano spray dryer 183

8.3.1 Operation principle of nano spray dryer 183

8.3.1.1 Piezo-electric driven vibrating mesh atomization 183

8.3.1.2 Heating mode, hot air flow pattern in and configuration of spray chamber 184

8.3.1.3 Product separation by electrostatic precipitator 186

8.4 Nanoencapsulation of food bioactive compounds by nano spray dryer 188

8.5 Analytical methods to characterize nanoencapsulates in foods 189

8.5.1 Electron microscopy 190

8.5.1.1 Scanning electron microscopy 190

8.5.1.2 Transmission electron microscopy 191

8.5.1.3 Atomic force microscopy 191

8.5.1.4 Atmospheric scanning electron microscopy 192

8.5.2 Quantification of nanoparticles’ size and mass by electron microscopy 193

References 195

9 Functional properties of spray dried encapsulates 198

9.1 Introduction 198

9.2 Controlled release of encapsulated bioactive compounds 198

9.2.1 Controlled release by dissolution 199

9.2.2 Controlled release by diffusion 199

9.3 Masking of off-taste by spray drying encapsulation 201

9.4 Improvement in stability of encapsulated bioactive compounds 202

References 208

10 Analysis of spray dried encapsulates 210

10.1 Introduction 210

10.2 Analysis of physical characteristics of spray dried encapsulates 211

10.2.1 Moisture content 211

10.2.2 Particle size 211

10.3 Analysis of the efficiency of spray drying encapsulation process 214

10.3.1 Estimation of encapsulation efficiency 214

10.3.1.1 Encapsulation efficiency of specialty oils 214

10.3.1.2 Encapsulation efficiency of vitamins and polyphenolic compounds 215

10.3.1.3 Encapsulation efficiency of flavors

and other volatile compounds 215

10.3.1.4 Encapsulation efficiency of probiotic cells 216

10.4 Analysis of the stability of spray dried microencapsulates 216

10.4.1 Analysis of probiotic cell stability under simulated in vitro gastrointestinal conditions 217

10.4.2 Analysis of oxidative stability for lipophilic core compounds 217

10.4.2.1 Estimation of peroxide value by spectrophotometry method 217

10.4.2.2 Rancimat method for estimation of peroxide value 218

10.4.2.3 Gas chromatography method for analysis of oxidative stability 219

10.4.3 Analysis of the functional properties of spray dried encapsulates 220

10.4.3.1 Study of core release from microencapsulates 220

10.4.3.2 Taste-masking effects 221

References 222

11 Modeling approach for spray drying and encapsulation applications 224

11.1 Introduction 224

11.2 Computational fluid dynamics modeling 224

11.2.1 Conservation of mass equation 225

11.2.2 Conservation of momentum equation 225

11.2.3 Conservation of energy equation 225

11.3 Modeling of spray drying process – a theoretical perspective 229

11.3.1 Atomization 230

11.3.1.1 Boundary conditions for atomization models 230

11.3.2 Spray-air contact 232

11.3.2.1 Reference frames 235

11.3.2.2 Turbulence models 237

11.3.2.3 Droplet/particle trajectory 239

11.3.2.4 Droplet temperature 239

11.3.2.5 Droplet residence time 240

11.3.2.6 Particle impact position 241

11.3.3 Droplet drying and particle formation 243

11.4 Modeling of core release from encapsulates 245

References 249

12 Synergistic spray drying techniques for encapsulation 252

12.1 Introduction 252

12.2 Spray fluidized bed coating for encapsulation 252

12.2.1 Theory of fluidization 253

12.2.2 Fluid bed encapsulation – process steps and influential factors 253

12.2.2.1 Atomization 254

12.2.2.2 Droplet-particle interactions 258

12.2.2.3 Drying of coating material on particle surface 261

12.2.2.4 Food ingredient applications of spray fluidized bed coating 261

12.2.2.5 Challenges associated with spray fluidized bed coating 262

12.2.2.6 Recent advancements in spray fluidized bed coating 263

12.3 Spray-freeze-drying for encapsulation 263

12.3.1 Spray freezing 265

12.3.1.1 Spray freezing into vapor (SFV) 265

12.3.1.2 Spray freezing into vapor over liquid (SFV/L) 265

12.3.1.3 Spray freezing into liquid (SFL) 269

12.3.2 Freeze drying 270

12.3.2.1 Conventional freeze drying 270

12.3.2.2 Atmospheric freeze drying 271

12.3.3 Factors affecting the encapsulation efficiency of SFD process 271

References 273

13 Industrial relevance and commercial applications of spray dried active food encapsulates 275

13.1 Introduction 275

13.2 Applications of spray dried encapsulates in the food industries 276

13.2.1 Confectionery industry 276

13.2.2 Bakery industry 277

13.2.3 Other product categories 278

13.3 Cost analysis of the spray drying encapsulated active ingredient 278

13.4 Major industry players producing spray dried encapsulated food ingredients 281

13.4.1 Symrise 281

13.4.2 International Flavors & Fragrances (IFF) 281

13.4.3 Firmenich 281

13.4.4 Givaudan 282

13.4.5 Takasago International Corporation 282

13.4.6 TasteTech 282

13.4.7 Kievit 282

13.4.8 Synthite 282

13.5 Challenges and future scope of the spray drying encapsulation of food ingredients 283

References 284

Index 285

Padma Ishwarya S. is Research Fellow of the Food Engineering Department, CSIR-Central Food Technological Research Institute, Mysore, India.