Food Oral Processing

This volume provides an overview of the latest research findings on the physics, physiology, and psychology of food oral consumption, as well as the experimental techniques available for food oral studies. Coverage includes the main physical and physiological functionalities of the mouth; the location and functionalities of various oral receptors; the main sequences of eating and drinking, and the concomitant food disintegration and destabilisation. Chapters also explain oral processing and its relation to flavour release and texture perception, and there is an introduction to the principles of food rheology as they relate to eating. Food Oral Processing is directed at food scientists and technologists in industry and academia, especially those involved in sensory science and new product development. It will also be of interest to oral physiologists, oral biologists and dentists. The book will be a useful reference for undergraduate and postgraduate students of these disciplines.

Here is the revised text with only person names wrapped in asterisks: Preface xiv  Contributors xvii  Part One Oral Anatomy and Physiology 1 1 Oral Cavity 3 Luciano José Pereira 1.1 Introduction 3  1.2 The oral cavity 3  1.3 Salivary glands and saliva secretion 6  1.4 Orofacial muscles 7  1.5 The tongue 9  1.6 Concluding remarks 12  Acknowledgements 12  References 13  2 Oral Receptors 15 LinaEngelen 2.1 Introduction to oral receptors 15  2.1.1 Babies sense the world around them through the mouth 15  2.1.2 Receptors 15  2.1.3 Innervation and transduction 16  2.2 Taste 17  2.2.1 Taste receptors 18  2.2.2 Taste molecules and modalities 20  2.2.2.1 What substances give rise to the different sensations? 20  2.3 Mechanoreception 22  2.3.1 Tactile stimulation 22  2.3.2 Function during eating 23  2.3.3 Mechanoreceptors in the mouth 24  2.3.3.1 SA1 – form and texture 25  2.3.3.2 Fa 1 25  2.3.3.3 SA2 – shape and position of tongue 25  2.3.4 Proprioceptors 26  2.3.4.1 Proprioception 26  2.3.4.2 Muscle spindles 27  2.3.4.3 Golgi tendon organ 27  2.3.4.4 Mechanoreceptors as proprioceptors 28  2.3.5 Periodontal receptors 28  2.3.5.1 Function of periodontal receptors 28  2.3.6 Signal transduction and central processing 29  2.4 Nociception 30  2.4.1 Nociceptors 30  2.4.2 Nociception in food 31  2.4.3 Nociceptive transduction 32  2.5 Thermal perception 33  2.5.1 Thermal sensation 33  2.5.2 Thermoreceptors 34  2.5.3 Thermal transduction 34  2.5.4 Temperature and food 35  2.5.5 The thermoreception and nociception relation 36  2.6 Olfaction 36  2.6.1 Olfaction and food 36  2.6.2 Olfactory receptors and transduction 37  2.7 Concluding remarks 38  References 38  3 Role of Saliva in the Oral Processing of Food 45 Guy Carpenter 3.1 Introduction 45  3.2 Control of salivary secretion 46  3.3 Functionalities of saliva 50  3.3.1 Salivary interactions with the oral mucosa 51  3.3.2 Perception of taste 52  3.3.3 Protection of the oral environment 53  3.4 Saliva in bolus formation, swallowing and oral clearance 54  3.4.1 Bolus formation and swallowing 54  3.4.2 Post-mastication oral clearance 54  3.5 Concluding remarks 56  Acknowledgements 56  References 57  Part Two FOOD ORAL MANAGEMENT 61 4 Oral Management of Food 63 Andriesvan derBilt 4.1 Introduction 63  4.2 Factors influencing oral function 63  4.2.1 Dental factors 66  4.2.2 Jaw muscle activity (EMG) and bite force 67  4.2.3 Masticatory performance 68  4.2.4 Swallowing of food 69  4.2.5 Saliva 70  4.3 Influence of food characteristics on chewing 72  4.3.1 Influence of food type on muscle activity, chewing force and jaw movement 74  4.3.2 Crispy food 75  4.3.3 Influence of food type and volume on swallowing 75  4.3.4 Muscle activity and jaw movement in various phases of chewing 78  4.4 Neuromuscular control of chewing and swallowing 79  4.4.1 Cortical masticatory area 80  4.4.2 Central pattern generator 80  4.4.3 Peripheral feedback 80  4.4.4 Simulated chewing experiments 81  4.4.5 Neuromuscular control of chewing crispy food 83  4.5 Concluding remarks 84  References 85  5 Breaking and Mastication of Solid Foods 95 Carolyn F. Rossand Clifford L.Hoye Jr. 5.1 Introduction 95  5.2 Mechanical properties and food texture 96  5.3 Characterisation of mechanical properties 96  5.4 Oral selection of food particles 99  5.4.1 The role of the tongue 99  5.4.2 Selection function 100  5.5 Breakage function 101  5.5.1 Definition of breakage function 101  5.5.2 Crack initiation and propagation 103  5.5.3 Correlations between breakage function and food mechanical properties 105  5.5.4 Limitations of breakage function 107  5.6 Concluding remarks 107  References 108  6 Oral Behaviour of Food Emulsions 111 Anwesha Sarkar and HarjinderSingh 6.1 Introduction 111  6.2 Food emulsions in general 112  6.3 Interfacial layers 113  6.4 Emulsion stability 117  6.4.1 Depletion flocculation 118  6.4.2 Bridging flocculation 119  6.4.3 Coalescence 120  6.5 Behaviour of emulsions under oral conditions 121  6.5.1 Saliva-induced destabilisation 122  6.5.1.1 Neutral or negatively charged emulsion−saliva interactions 124  6.5.1.2 Positively charged emulsion−saliva interactions 125  6.5.2 Shear-induced destabilisation 127  6.5.3 Relating oral destabilisation to sensory perception 129  6.5.3.1 Droplet flocculation 129  6.5.3.2 Droplet coalescence 130  6.6 Concluding remarks 131  References 132  7 Bolus Formation and Swallowing 139 JiansheChen 7.1 Introduction 139  7.2 Mechanisms of swallowing 139  7.2.1 Stages of swallowing 139  7.2.1.1 The oral phase 140  7.2.1.2 The pharyngeal phase 141  7.2.1.3 The oesophageal phase 142  7.2.2 Oral pressure and bolus swallowing 143  7.2.2.1 Bolus location before swallowing 143  7.2.2.2 The oral pressure 144  7.2.2.3 Measurements of oral pressure 146  7.3 The formation of a food bolus and the triggering criteria of bolus swallowing 147  7.3.1 Dynamics of bolus formation 147  7.3.2 Critical criteria in triggering a swallow 149  7.3.3 Influences of food properties on bolus formation 152  7.4 Concluding remarks 154  References 155  Part Three Food Oral Processing and Sensory Perception 157 8 Oral Processing and Texture Perception 159 LinaEngelen and René A. deWijk 8.1 Introduction 159  8.1.1 What is texture? 159  8.1.2 Why is texture important for the perception of foods? 160  8.2 Where is texture sensed in the mouth? 161  8.2.1 The special case of the texture of fat 161  8.3 Texture versus food structure 162  8.3.1 Liquids 162  8.3.2 Semi-solids 162  8.3.3 Solids 163  8.3.3.1 Crispy and crunchy food 163  8.4 The measurement of oral processes 164  8.5 Texture versus oral processing 165  8.6 Texture attributes are systematically related 167  8.7 The role of saliva in texture perception 168  8.7.1 Saliva flow rate and texture perception 169  8.7.2 Saliva composition and texture perception 170  8.7.3 Salivary enzymes and texture perception 171  8.8 Oral temperature and texture perception 171  8.9 Concluding remarks 172  References 173  9 Oral Processing and Flavour Sensing Mechanisms 177 Sarah Adams and Andrew J. Taylor 9.1 Introduction 177  9.2 Mechanisms for sensing and measuring taste 178  9.2.1 Taste thresholds 179  9.2.2 Food structure, oral breakdown and tastant release 180  9.3 Mechanisms for sensing and measuring aroma 181  9.4 Mechanisms for sensing and measuring texture 184  9.5 Multi-sensory interactions 187  9.6 Measuring food breakdown and deposition in vivo 189  9.6.1 Imaging food in vivo 190  9.6.2 Spectroscopy of food components in vivo 192  9.6.3 Following mastication in vivo 193  9.7 Biochemical flavour changes during oral processing 193  9.8 Applications of knowledge to real food products 195  9.9 Concluding remarks 195  Acknowledgements 196  References 196  10 Multi-sensory Integration and the Psychophysics of Flavour Perception 203 Charles Spence 10.1 Introduction 203  10.2 Taste/Gustation 205  10.3 Olfactory–gustatory interactions in multi-sensory flavour perception 206  10.4 Oral–somatosensory contributions to multi-sensory flavour perception 208  10.5 Auditory contributions to multi-sensory flavour perception 210  10.6 ‘Visual flavour’: visual contributions to multi-sensory flavour perception 211  10.7 The cognitive neuroscience of multi-sensory flavour perception 215  10.8 Concluding remarks 216  References 219  Part Four Principles and Practices of Instrumental Characterisation for Eating and Sensory Perception Studies 225 11 ‘Oral’ Rheology 227 Jason R. Stokes 11.1 Introduction to food rheology and oral processing 227  11.2 Liquid food rheology and structure 229  11.2.1 Dispersions of particles and polymers 229  11.2.2 Shear thinning 231  11.2.3 Viscoelasticity 234  11.2.3.1 Linear viscoelasticity 235  11.2.3.2 Non-linear viscoelasticity: normal stresses 236  11.2.3.3 Extensional viscosity 237  11.2.4 Instrumentation for liquid foods 237  11.2.4.1 Cone-and-plate 237  11.2.4.2 Parallel plate 238  11.2.4.3 Concentric cylinder 238  11.2.4.4 Extensional viscosity 238  11.3 Soft food rheology and microstructure 239  11.3.1 Microstructure: gels and glasses 239  11.3.2 Rheology 241  11.3.3 Mechanical properties and fracturing behaviour 244  11.4 Solid food breakdown and rheology 245  11.5 Saliva and rheology 246  11.5.1 Saliva 246  11.5.2 Real or artificial saliva to study food–saliva interactions? 247  11.5.3 Saliva rheology 248  11.6 Sensory perception and the fluid dynamics between tongue and palate 249  11.6.1 Shear flow 250  11.6.2 Shear flow and sensory thickness: what is the shear rate in the mouth? 251   11.6.3 Squeeze flow 253  11.6.4 Shear and squeeze flow: defining an oral shear stress? 255  11.6.5 Micro-rheology: gap dependency, confinement and slip 258  11.7 Concluding remarks 258  References 259  12 ‘Oral’ Tribology 265 Jason R. Stokes 12.1 Introduction 265  12.2 Principles of tribology 266  12.2.1 Hydrodynamic lubrication and the Reynolds equation 266  12.2.2 Elastohydrodynamic lubrication 267  12.2.3 Film thickness and friction in isoviscous elastohydrodynamic lubrication 268  12.2.4 Limits of hydrodynamic lubrication: Stribeck curve 270  12.2.5 Boundary lubrication 271  12.3 Food lubrication 273  12.3.1 Kokini models for ‘smoothness’ and ‘slipperiness’ 274  12.3.2 Biosubstrates and simulated oral contacts 275  12.3.3 Soft-tribology 277  12.3.3.1 Master curves 277  12.3.3.2 Emulsions 278  12.3.3.3 Hydrocolloids 280  12.3.3.4 Saliva 282  12.4 Concluding remarks 284  Acknowledgements 285  References 285  13 Applications of Electromyography (EMG) Technique for Eating Studies 289 Yadira Gonzalez Espinosa and JiansheChen 13.1 Introduction 289  13.2 Principles of electromyography technique 289  13.2.1 Muscle motors and their activation 289  13.2.2 Surface electromyography vs. intra-muscular electromyography 290  13.3.3 Main mastication muscles for surface electromyography studies 292  13.3 EMG experimental design and set-up 293  13.3.1 Electrodes, location and placement 293  13.3.2 Selection criteria of subjects for EMG studies 298  13.3.3 Experimental procedures 299  13.3.3.1 Preparation 299  13.3.3.2 Set-up 300  13.3.3.3 Set-up checking and validation 300  13.3.3.4 Test performance 301  13.4 Data analysis 304  13.4.1 Processing of raw EMG signals 304  13.4.1.1 Rectification 305  13.4.1.2 Integration 305  13.4.1.3 Root mean square (RMS) 305  13.4.2 Masticatory parameters: analysis of chewing sequence and individual chewing cycles 306  13.4.2.1 Analysis of the whole chewing sequence 306  13.4.2.2 Analysis of individual chewing cycles 309  13.5 Case studies 312  13.6 Concluding remarks 314  References 315  14 Soft Machine Mechanics and Oral Texture Perception 319 MichaPeleg and Maria G.Corradini 14.1 Introduction 319  14.2 Sensory terms and vocabulary 321  14.3 Soft machine mechanics 322  14.3.1 The signal generated by stiff and soft machines 322  14.3.2 Mechanical sensitivity of soft machines 325  14.4 The ‘amplifier’ and sensory sensitivity 327  14.5 Adaptation and fatigue 333  14.6 Concluding remarks 334  References 335  Part Five Applications and New Product Developments 337 15 Appreciation of Food Crispness and New Product Development 339 Paula Varela and SusanaFiszman 15.1 Introduction 339  15.2 Appreciation of crispy and crunchy texture 339  15.3 Mechanical and structural features of crispy/crunchy food 340  15.3.1 Wet-crisp food products 340  15.3.2 Dry-crisp food products 341  15.3.3 Crusted or multi-layered food products 342  15.4 Characterisation of crispy/crunchy textures 342  15.4.1 Sensory perception and measurement of crispness/ crunchiness 342  15.4.2 Instrumental characterisation of crispness/crunchiness 343  15.4.2.1 Texture measurements 343  15.4.2.2 Acoustics 344  15.4.3 Instrumental characterisation of crispness – structure and microstructure 346  15.5 Influence of the product design and formulation, process and storage conditions in the attainment, enhancement and maintenance of the crispy/crunchy character in wet, dry and crusted food products 348  15.5.1 Wet-crisp products 348  15.5.2 Dry and crusted products 350  15.5.2.1 Bread as an example of composite crisp food 350  15.5.2.2 Deep fried products 351  15.6 Concluding remarks 353  References 353  16 Design of Food Structure for Enhanced Oral Experience 357 Adam Burbidge 16.1 Introduction 357  16.2 Biophysics of oral perception 357  16.3 Structural stimuli of mechanoreceptors 363  16.4 Engineering of microstructures in food 370  16.4.1 Freeze drying 373  16.4.2 Puffed cereals 375  16.4.3 Spray dried powders 376  16.4.4 Ice cream production 377  16.5 Acknowledgements 378