Confectionery and Chocolate Engineering (2^nd Ed.)
Principles and Applications

Confectionery and chocolate manufacture has been dominated by large-scale industrial processing for several decades. It is often the case though, that a trial and error approach is applied to the development of new products and processes, rather than verified scientific principles.

Confectionery and Chocolate Engineering: Principles and Applications, Second edition, adds to information presented in the first edition on essential topics such as food safety, quality assurance, sweets for special nutritional purposes, artizan chocolate, and confectioneries. In addition, information is provided on the fading memory of viscoelastic fluids, which are briefly discussed in terms of fractional calculus, and gelation as a second order phase transition. Chemical operations such as inversion, caramelization, and the Maillard reaction, as well as the complex operations including  conching, drying, frying, baking, and roasting used in confectionery manufacture are also described.

This book provides food engineers, scientists, technologists and students in research, industry, and food and chemical engineering-related courses with a scientific, theoretical description and analysis of confectionery manufacturing, opening up new possibilities for process and product improvement, relating to increased efficiency of operations, the use of new materials, and new applications for traditional raw materials.

Preface xxiii

Preface to the second edition xxvii

Acknowledgements xxix

Part I: Theoretical introduction

1 Principles of food engineering 3

1.1 Introduction 3

1.2 The Damköhler equations 6

1.3 Investigation of the Damköhler equations by means of similarity theory 8

1.4 Analogies 14

1.5 Dimensional analysis 16

1.6 System theoretical approaches to food engineering 19

1.7 Food safety and quality assurance 21

Further reading 22

2 Characterization of substances used in the confectionery industry 23

2.1 Qualitative characterization of substances 23

2.2 Quantitative characterization of confectionery products 33

2.3 Preparation of recipes 49

2.4 Composition of chocolate confectioneries biscuits and wafers made for special nutritional purposes 56

Further reading 60

3 Engineering properties of foods 61

3.1 Introduction 61

3.2 Density 61

3.3 Fundamental functions of thermodynamics 65

3.4 Latent heat and heat of reaction 71

3.5 Thermal conductivity 76

3.6 Thermal diffusivity and Prandtl number 78

3.7 Mass diffusivity and Schmidt number 81

3.8 Dielectric properties 85

3.9 Electrical conductivity 91

3.10 Infrared absorption properties 95

3.11 Physical characteristics of food powders 96

Further reading 107

4 The rheology of foods and sweets 109

4.1 Rheology: its importance in the confectionery industry 109

4.2 Stress and strain 109

4.3 Solid behaviour 115

4.4 Fluid behaviour 120

4.5 Viscosity of solutions 159

4.6 Viscosity of emulsions 161

4.7 Viscosity of suspensions 164

4.8 Rheological properties of gels 166

4.9 Rheological properties of sweets 171

4.10 Rheological properties of wheat flour doughs 183

4.11 Relationship between food oral processing and rheology 193

Further reading 194

5 Introduction to food colloids 197

5.1 The colloidal state 197

5.2 Formation of colloids 199

5.3 Properties of macromolecular colloids 202

5.4 Properties of colloids of association 208

5.5 Properties of interfaces 210

5.6 Electrical properties of interfaces 219

5.7 Theory of colloidal stability: the DLVO theory 221

5.8 Stability and changes of colloids and coarse dispersions 224

5.9 Emulsion instability 233

5.10 Phase inversion 243

5.11 Foams 245

5.12 Gelation as a second-order phase transition 256

Further reading 261

Part II: Physical operations

6 Comminution 265

6.1 Changes during size reduction 265

6.2 Rittinger’s surface theory 266

6.3 Kick’s volume theory 267

6.4 The third or Bond theory 268

6.5 Energy requirement for comminution 268

6.6 Particle size distribution of ground products 269

6.7 Particle size distributions 273

6.8 Kinetics of grinding 275

6.9 Comminution by five-roll refiners 276

6.10 Grinding by a melangeur 280

6.11 Comminution by a stirred ball mill 284

Further reading 289

7 Mixing/kneading 290

7.1 Technical solutions to the problem of mixing 290

7.2 Power characteristics of a stirrer 290

7.3 Mixing time characteristics of a stirrer 292

7.4 Representative shear rate and viscosity for mixing 292

7.5 Calculation of the Reynolds number for mixing 292

7.6 Mixing of powders 294

7.7 Mixing of fluids of high viscosity 300

7.8 Effect of impeller speed on heat and mass transfer 301

7.9 Mixing by blade mixers 302

7.10 Mixing rolls 303

7.11 Mixing of two liquids 304

Further reading 304

8 Solutions 306

8.1 Preparation of aqueous solutions of carbohydrates 306

8.2 Solubility of sucrose in water 308

8.3 Aqueous solutions of sucrose and glucose syrup 309

8.4 Aqueous sucrose solutions containing invert sugar 311

8.5 Solubility of sucrose in the presence of starch syrup and invert sugar 312

8.6 Rate of dissolution 312

8.7 Solubility of bulk sweeteners 315

Further reading 316

9 Evaporation 317

9.1 Theoretical background: Raoult’s law 317

9.2 Boiling point of sucrose/water solutions at atmospheric pressure 318

9.3 Application of a modification of Raoult’s law to calculate the boiling point of carbohydrate/water solutions at decreased pressure 319

9.3.1 Sucrose/water solutions 319

9.3.2 Dextrose/water solutions 319

9.3.3 Starch syrup/water solutions 319

9.3.4 Invert sugar solutions 319

9.3.5 Approximate formulae for the elevation of the boiling point of aqueous sugar solutions 320

9.4 Vapour pressure formulae for carbohydrate/water solutions 323

9.5 Practical tests for controlling the boiling points of sucrose solutions 330

9.6 Modelling of an industrial working process for hard boiled sweets 331

9.7 Boiling points of bulk sweeteners 335

Further reading 335

10 Crystallization 337

10.1 Introduction 337

10.2 Crystallization from solution 337

10.3 Crystallization from melts 355

10.4 Crystal size distributions 371

10.5 Batch crystallization 374

10.6 Isothermal and non-isothermal recrystallization 375

10.7 Methods for studying the supermolecular structure of fat melts 376

10.8 Crystallization of glycerol esters: Polymorphism 381

10.9 Crystallization of cocoa butter 385

10.10 Crystallization of fat masses 398

10.11 Crystallization of confectionery fats with a high trans-fat portion 411

10.12 Modelling of chocolate cooling processes and tempering 414

10.13 EU programme ProPraline 421

Further reading 422

11 Gelling emulsifying stabilizing and foam formation 424

11.1 Hydrocolloids used in confectionery 424

11.2 Agar 424

11.3 Alginates 429

11.4 Carrageenans 432

11.5 Furcellaran 437

11.6 Gum arabic 437

11.7 Gum tragacanth 438

11.8 Guaran gum 439

11.9 Locust bean gum 439

11.10 Pectin 440

11.11 Starch 444

11.12 Xanthan gum 447

11.13 Gelatin 448

11.14 Egg proteins 453

11.15 Foam formation 458

Further reading 466

12 Transport 468

12.1 Types of transport 468

12.2 Calculation of flow rate of non-newtonian fluids 468

12.3 Transporting dessert masses in long pipes 470

12.4 Changes in pipe direction 471

12.5 Laminar unsteady flow 472

12.6 Transport of flour and sugar by airflow 472

Further reading 477

13 Pressing 478

13.1 Applications of pressing in the confectionery industry 478

13.2 Theory of pressing 478

13.3 Cocoa liquor pressing 480

Further reading 482

14 Extrusion 483

14.1 Flow through a converging die 483

14.2 Feeders used for shaping confectionery pastes 491

14.3 Extrusion cooking 495

14.4 Roller extrusion 497

Further reading 500

15 Particle agglomeration: instantization and tabletting 501

15.1 Theoretical background 501

15.2 Processes of agglomeration 512

15.3 Granulation by fluidization 514

15.4 Tabletting 516

Further reading 524

Part III: Chemical and complex operations: stability of sweets: artisan chocolate and confectioneries

16 Chemical operations (inversion and caramelization) ripening and complex operations 527

16.1 Inversion and caramelization 527

16.2 Acrylamide formation 538

16.3 Alkalization of cocoa material 540

16.4 Ripening 542

16.5 Complex operations 545

16.6 Drying/frying baking and roasting 562

Further reading 577

17 Water activity shelf life and storage 579

17.1 Water activity 579

17.2 Shelf life and storage 594

17.3 Storage scheduling 601

Further reading 602

18 Stability of food systems 604

18.1 Common use of the concept of food stability 604

18.2 Stability theories: types of stability 604

18.3 Shelf life as a case of marginal stability 606

18.4 Stability matrix of a food system 607

Further reading 608

19 Artisan chocolate and confectioneries 609

19.1 Actuality of artisanship in the confectionery practice 609

19.2 The characteristics of the artisan products 609

19.3 Raw materials and machinery 610

19.4 The characteristics of the artisan confectionery technologies 611

19.5 Managing an artisan workshop 611

19.6 An easy and effective shaping technology for producing praline bars 612

Further reading 614

Part IV: Appendices

1 Data on engineering properties of materials used and made by the confectionery industry 617

A1.1 Carbohydrates 617

A1.2 Oils and fats 626

A1.3 Raw materials semi-finished products and finished products 626

2 Comparison of Brix and Baumé concentrations of aqueous sucrose solutions at 20 ^∘C(68 ^∘F) 643

3 Survey of fluid models: some trends in rheology 645

A3.1 Decomposition method for calculation of flow rate of rheological models 645

A3.1.1 The principle of the decomposition method 645

A3.1.2 Bingham model 646

A3.1.3 Casson models 647

A3.1.4 Herschel–Bulkley–Porst–Markowitsch–Houwink (HBPMH) (or generalized Ostwald–de Waele) model 651

A3.1.5 Ostwald–de Waele model (The power law) 653

A3.2 Calculation of the friction coefficient (ξ) of non-newtonian fluids in the laminar region 653

A3.3 Tensorial representation of constitutive equations: The fading memory of viscoelastic fluids 654

A3.3.1 Objective derivatives and tensorial representation of constitutive equations 654

A3.3.2 Boltzmann’s equation for the stress in viscoelastic solids: The fading memory of viscoelastic fluids 656

A3.3.3 Constitutive equations of viscoelastic fluids 657

A3.3.4 Application of the constitutive equations to dough rheology 658

A3.3.5 Rheological properties at the cellular and macroscopic scale 659

A3.4 Computer simulations in food rheology and science 660

A3.5 Ultrasonic and photoacoustic testing 660

A3.5.1 Ultrasonic testing 660

A3.5.2 Photoacoustic testing 661

Further reading 661

4 Fractals 663

A4.1 Irregular forms: fractal geometry 663

A4.2 Box-counting dimension 664

A4.3 Particle-counting method 665

A4.4 Fractal backbone dimension 666

Further reading 666

5 Introduction to structure theory 668

A5.1 The principles of the structure theory of blickle and seitz 668

A5.1.1 Attributes and their relations: structure 668

A5.1.2 Structure of attributes: a qualitative description 669

A5.1.3 Hierarchic structures 670

A5.1.4 Structure of measure: a quantitative description 670

A5.1.5 Conservative elements: conservative substantial fragments 670

A5.1.6 New way of looking 672

A5.2 Modelling a part of fudge processing plant by structure theory 673

Further reading 674

6 Technological layouts 675

Further reading 686

References 687

Index 737