Dr Jianshe Chen is Senior Lecturer in the School of Food Science and Nutrition, University of Leeds, UK. Dr Lina Engelen is Research Fellow in the Faculty of Health Sciences, University of Sydney, Australia.

This book contains extremely useful reference material for individuals working and studying in a broad range of disciplines who desire to know more about aspects of food oral processing. Rarely has all of this information been found in one place. (Trends in Food Science & Technology, 8 October 2012)

• Here is the revised text with only person names wrapped in asterisks:Preface xiv Contributors xvii Part One Oral Anatomy and Physiology 11 Oral Cavity 3Luciano José Pereira1.1 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 15LinaEngelen2.1 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 45Guy Carpenter3.1 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 614 Oral Management of Food 63Andriesvan derBilt4.1 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 95Carolyn 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 111Anwesha Sarkar and HarjinderSingh6.1 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 139JiansheChen7.1 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 1578 Oral Processing and Texture Perception 159LinaEngelen and René A. deWijk8.1 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 177Sarah Adams and Andrew J. Taylor9.1 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 203Charles Spence10.1 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 22511 ‘Oral’ Rheology 227Jason R. Stokes11.1 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 265Jason R. Stokes12.1 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 289Yadira Gonzalez Espinosa and JiansheChen13.1 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 319MichaPeleg and Maria G.Corradini14.1 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 33715 Appreciation of Food Crispness and New Product Development 339Paula Varela and SusanaFiszman15.1 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 357Adam Burbidge16.1 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

Dr Jianshe Chen is Senior Lecturer in the School of Food Science and Nutrition, University of Leeds, UK. Dr Lina Engelen is Research Fellow in the Faculty of Health Sciences, University of Sydney, Australia.

This book contains extremely useful reference material for individuals working and studying in a broad range of disciplines who desire to know more about aspects of food oral processing. Rarely has all of this information been found in one place. (Trends in Food Science & Technology, 8 October 2012)

• Here is the revised text with only person names wrapped in asterisks:Preface xiv Contributors xvii Part One Oral Anatomy and Physiology 11 Oral Cavity 3Luciano José Pereira1.1 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 15LinaEngelen2.1 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 45Guy Carpenter3.1 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 614 Oral Management of Food 63Andriesvan derBilt4.1 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 95Carolyn 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 111Anwesha Sarkar and HarjinderSingh6.1 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 139JiansheChen7.1 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 1578 Oral Processing and Texture Perception 159LinaEngelen and René A. deWijk8.1 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 177Sarah Adams and Andrew J. Taylor9.1 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 203Charles Spence10.1 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 22511 ‘Oral’ Rheology 227Jason R. Stokes11.1 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 265Jason R. Stokes12.1 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 289Yadira Gonzalez Espinosa and JiansheChen13.1 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 319MichaPeleg and Maria G.Corradini14.1 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 33715 Appreciation of Food Crispness and New Product Development 339Paula Varela and SusanaFiszman15.1 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 357Adam Burbidge16.1 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

Dr Jianshe Chen is Senior Lecturer in the School of Food Science and Nutrition, University of Leeds, UK. Dr Lina Engelen is Research Fellow in the Faculty of Health Sciences, University of Sydney, Australia.

This book contains extremely useful reference material for individuals working and studying in a broad range of disciplines who desire to know more about aspects of food oral processing. Rarely has all of this information been found in one place. (Trends in Food Science & Technology, 8 October 2012)

• Here is the revised text with only person names wrapped in asterisks:Preface xiv Contributors xvii Part One Oral Anatomy and Physiology 11 Oral Cavity 3Luciano José Pereira1.1 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 15LinaEngelen2.1 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 45Guy Carpenter3.1 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 614 Oral Management of Food 63Andriesvan derBilt4.1 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 95Carolyn 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 111Anwesha Sarkar and HarjinderSingh6.1 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 139JiansheChen7.1 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 1578 Oral Processing and Texture Perception 159LinaEngelen and René A. deWijk8.1 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 177Sarah Adams and Andrew J. Taylor9.1 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 203Charles Spence10.1 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 22511 ‘Oral’ Rheology 227Jason R. Stokes11.1 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 265Jason R. Stokes12.1 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 289Yadira Gonzalez Espinosa and JiansheChen13.1 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 319MichaPeleg and Maria G.Corradini14.1 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 33715 Appreciation of Food Crispness and New Product Development 339Paula Varela and SusanaFiszman15.1 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 357Adam Burbidge16.1 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