Functional Foods and Beverages In vitro Assessment of Nutritional, Sensory, and Safety Properties

A much-needed guide to in vitro food functionality evaluation principles, processes, and state-of-the-art modeling 

There are more than a few books devoted to the assessment of food functionality but, until now, there were no comprehensive guides focusing on the increasingly important subject of in vitro food evaluation. With contributions from the world’s foremost experts in the field, this book brings readers up to speed on the state-of-the-art in in vitro modeling, from its physiological bases to its conception, current uses, and future developments.

Food functionality is a broad concept encompassing nutritional and health functionality, food safety and toxicology, as well as a broad range of visual and organoleptic properties of food. In vitro techniques bridge the gap between standard analytical techniques, including chemical and biochemical approaches and in vivo human testing, which remains the ultimate translational goal for evaluation of the functionality of food. Although it is a well- established field, in vitro food testing continues to evolve toward ever more accurate predictions of in vivo properties and outcomes. Both ethical and highly economical, these approaches allow for detailed mechanistic insights into food functionalities and, therefore, a better understanding of the interactions of food and human physiology.

• Reviews the core concepts of food functionality and functionality evaluation methodologies
• Provides an overview of the physiology of the gastrointestinal tract, including host-microbial interactions within it
• Delves into the physiology of sensory perception of food, taste and texture as they relate to in vitro modeling
• Explores the challenges of linking in vitro analysis of taste, aroma and flavor to their actual perception
• Addresses in vitro models of the digestion and absorption of macronutrients, micronutrients, and phytonutrients
• Describes in vitro evaluations of toxicants, allergens and other specific food hazards

Functional Foods and Beverages is an indispensable working resource for food scientists as well as researchers working in government facilities dedicated to tracking food safety.

Nicolas Bordenave, PhD, Assistant Professor, Faculty of Health Sciences, School of Nutrition Sciences, University of Ottawa, Ottawa, Canada

Mario G. Ferruzzi, PhD, Professor of Food Science and Nutrition, Department of Food, Bioprocessing and Nutrition Science, Plants for Human Health Institute, North Carolina State University, Raleigh, USA

List of Contributors xv

Preface xvii

Acknowledgements xix

1 Overview of Functional Foods 1
Robin A. Ralston, Amy D. Mackey, Christopher T. Simons and Steven J. Schwartz

1.1 Overview of Functional Foods 1

1.1.1 Foods and Nutrients are Linked to Health and Disease 1

1.1.2 Definition of Functional Foods 2

1.1.3 Functional Foods Market 2

1.1.4 How Functional Foods are Studied 3

1.2 Functional Foods and their Regulatory Aspects 6

1.3 Nanotechnologies in Functional Foods 7

1.4 Sensory Functionalities of Foods 9

References 11

2 The In vivo Foundations for In vitro Testing of Functional Foods: The Gastrointestinal System 15
Edwin K. McDonald, Heather Rasmussen, Christopher Forsyth and Ali Keshavarzian

2.1 Introduction 15

2.2 Overview of the Structure of the Gastrointestinal Tract 16

2.2.1 Mucosa 17

2.2.2 Submucosa 17

2.2.3 Muscularis (or Muscularis Propria) and Serosa (or Adventitia) 18

2.2.4 Additional Components of the Gastrointestinal Tract: Accessory Organs, Vasculature, Innervation, Gut�-Associated Lymphoid Tissue, and Microbiome 18

2.2.4.1 Accessory Organs of the GIT 18

2.2.4.2 Vasculature of the GIT: Blood and Lymphatic Supply 19

2.2.4.3 GIT Innervation 19

2.2.4.4 Gut�-Associated Lymphoid Tissue 19

2.2.4.5 Intestinal Microbiome 20

2.3 Functions of the GIT and Associated In vitroModeling 20

2.3.1 Motility 21

2.3.1.1 The Foundations of GIT Motility: Smooth Muscle Cell Contractions (SMC) and ENS Regulation 22

2.3.1.2 In vitro Motility Modeling 23

2.3.2 Barrier Function, Secretion, and Absorption 24

2.3.2.1 Tight Junctions and the Barrier Function of the GIT 25

2.3.2.2 Intestinal Permeability: Definitions and the Role of Tight Junctions 26

2.3.2.3 Influences on Permeability 26

2.3.2.4 Absorption and Secretion 27

2.3.2.5 In vitro Models of Barrier Function, Absorption, and Secretion 28

2.3.3 Regulation of Immune Response 32

2.3.3.1 The Mucosal Immune Response Depends on IECs and GALT 32

2.3.3.2 Antigen Exclusion: The Importance of Secretory IgA 32

2.3.3.3 Antigen Sampling is Necessary for Immune Homeostasis 33

2.3.3.4 Antigen Presenting Cells and IECs Modulate T�-cell Adaptive Immune Responses 34

2.3.3.5 In vitro Models of Mucosal Immunity 34

2.3.4 Storage, Fermentation, and Removal of Fecal Matter 35

2.3.4.1 Storage and Removal of Fecal Matter 35

2.3.4.2 Colonic Fermentation 36

2.3.4.3 Short-Chain Fatty Acids 37

2.3.4.4 In vitro Models of Fermentation 37

2.4 Limitations of In vitro Modeling of the Gastrointestinal Tract 38

2.5 Dynamic In vitro Models of Digestion 40

2.6 Conclusions 40

References 41

3 In vivo Foundations of Sensory In vitro Testing Systems 53
James Hollis

3.1 Introduction 53

3.2 Taste 54

3.2.1 Overview 54

3.2.2 Taste Anatomy 55

3.2.3 Taste Coding 58

3.2.4 Transduction Mechanisms 58

3.2.4.1 Overview 58

3.2.4.2 Sour 59

3.2.4.3 Salt 60

3.2.4.4 Bitter 60

3.2.4.5 Sweet 61

3.2.4.6 Umami 62

3.2.4.7 Downstream Signaling of T1R and T2R 62

3.2.5 Non�-Canonical Taste Modalities 63

3.2.5.1 Fat Taste 63

3.2.5.2 Calcium 64

3.3 Factors that Influence Taste Acuity 65

3.3.1 Saliva 65

3.3.2 Genetic Differences 66

3.4 Chemesthesis 66

3.5 The Olfactory System 67

3.5.1 Olfactory Anatomy 68

3.5.2 Olfactory Binding Proteins 68

3.5.3 Olfactory Receptors 69

3.5.4 Transduction Mechanisms 70

3.6 Texture 70

3.6.1 Mechanoreceptors 71

3.6.2 Proprioreceptors 71

3.6.3 Periodontal Receptors 72

3.6.4 Central Processing of Texture 72

3.7 Convergence of Taste, Smell and Texture to Produce Flavor 73

3.8 Concluding Remarks 73

References 74

4 In vitro Models of Host–Microbial Interactions Within the Gastrointestinal Tract 87
Ezgi Özcan, Rachel Levantovsky, and David A. Sela

4.1 Introduction: The Human Gastrointestinal Tract 87

4.2 The Current State of In vitro Model Systems to Model Gut Ecosystems 91

4.3 Batch Culture Systems to Model the Gut Microbial Consortium 93

4.4 Continuous Systems to Model the Human GIT 96

4.5 Mucus�-Immobilized Models of the Gut 107

4.6 Models to Simulate Complex Host–Microbial Interactions 111

4.7 Gastric–Small Intestine Model Systems 113

References 120

5 Macronutrient Nutritional Functionality of Carbohydrates, Proteins and Lipids: Digestibility, Absorption and Interactions 137
Amanda Wright and Susan M. Tosh

5.1 Introduction 137

5.2 Applications and Considerations 139

5.2.1 Carbohydrates 139

5.2.2 Proteins 141

5.2.3 Triglycerides 142

5.3 Simulating Digestive Processes 143

5.3.1 Oral Food Processing and Implications for Sample Preparation 143

5.3.2 Gastric Phase 145

5.3.3 Upper Intestinal Phase 147

5.4 Interactions and Structural Considerations 150

5.5 Post�-Digestion Analysis 151

5.6 In vitro Models 154

5.6.1 Static Models 154

5.6.1.1 INFOGEST Method for General Nutrient Digestion 154

5.6.1.2 Englyst Method for Rate for Carbohydrate Digestion 158

5.6.1.3 Streamlined Protein Digestibility 159

5.6.1.4 pH Stat Method for Testing Emulsified Lipids 160

5.6.2 Dynamic 160

5.7 Limitation of In vitro Digestion Tests 162

5.8 Conclusions 163

References 164

6 In vitro Approaches for Investigating the Bioaccessibility and Bioavailability of Dietary Nutrients and Bioactive Metabolites 171
Chureeporn Chitchumroonchokchai and Mark L. Failla

6.1 Introduction 171

6.2 Static Models of In vitro Digestion 173

6.3 Dynamic Models of In vitro Digestion 176

6.4 Application of In vitro Digestion Method for Determining the Digestive Stability and Bioaccessibility of Dietary Compounds 177

6.5 Caco�-2 Cell Model 180

6.6 Examples of the Effects of Bioaccessible Dietary Compounds on the Functions of Absorptive Intestinal Epithelial Cells 183

6.7 Coupling the In vitro Digestion and Caco�]2 Cell Models 185

6.8 Co�-culture Models Using Caco�-2 Cells 187

6.9 Conclusions 192

References 192

7 In vitro Models for Testing Toxicity in the Gastrointestinal Tract 201
Ioannis Trantakis

7.1 Introduction 201

7.2 Advantages of In vitro Tests 203

7.3 Limitations of Established Cell Line Models 204

7.4 Single Cell Lines 205

7.5 Co�-culture Cell Models 207

7.6 3D Co�-culture Models 209

7.7 Organs on a Chip 210

7.8 Summary and Conclusions 214

References 214

8 In vitro Methods for Assessing Food Protein Allergenicity 219
Ossanna Nashalian, Nicolas Bordenave and Chibuike Udenigwe

8.1 Introduction 219

8.2 Food Sensitization, Hypersensitivity and Allergy 220

8.2.1 The Mechanism of Developing Food Hypersensitivities 222

8.2.2 The Exposure to Allergens 224

8.2.2.1 The Gastrointestinal (GI) Route 225

8.2.2.2 The Respiratory Tract Route 231

8.2.2.3 The Cutaneous Route 231

8.3 Safety Needs and Regulatory Consideration in Detecting Allergens in Food 231

8.4 In vitro Analytical Methods for Testing Known Allergens 234

8.4.1 Protein�-Based Approaches 234

8.4.2 Immunoassay Approaches 238

8.4.2.1 Enzyme�-Linked Immunosorbent Assay (ELISA) 238

8.4.2.2 Other Immunoassay�-based Methods 240

8.4.3 DNA�-based Approaches 242

8.4.3.1 Real�-Time PCR 242

8.4.3.2 Microarray Assay 242

8.4.4 Mass Spectrometry�-based Approaches 243

8.4.5 In vitro Cell�-based Methods for the Prediction of Food Allergenicity 243

8.4.6 In Silico Methods for the Prediction of Food Allergenicity 246

References 251

9 Challenges of Linking In vitro Analysis to Flavor Perception 263
Avinash Kant and Rob Linforth

9.1 Introduction 263

9.2 What is “Flavor”? 264

9.2.1 Flavor Analysis Overview 264

9.2.2 Significance of Aroma Compounds 265

9.2.3 Challenges of Food Flavor Compounds 266

9.3 Overview of Flavor Analysis Techniques 269

9.3.1 Key Isolation Techniques 269

9.3.2 Taste Compound Isolation 270

9.3.3 Aroma Compound Isolation 270

9.3.3.1 Solvent Extraction 270

9.3.3.2 Distillation 271

9.3.3.3 Headspace 271

9.3.4 Taste Compound Detection 272

9.3.5 Aroma Compound Separation and Detection 272

9.4 Further Developments in Aroma Analysis 273

9.4.1 Gas Chromatography–Olfactometry 273

9.4.2 Interpretation of GC–Olfactometry Data 274

9.4.3 Recent Advances in Aroma Extract Preparation 277

9.4.4 Solid-Phase MicroExtraction 277

9.4.5 Advances in Solvent Assisted Flavor Extraction 279

9.4.6 Challenges of Single Aroma Compound Data Interpretation 280

9.4.7 Correlation of the Sensory Experience with GC Data 281

9.5 Recent Advances Developing In vitro Flavor Analysis Tools 282

9.5.1 Electronic Devices for Flavor Assessment 282

9.5.2 eNose 283

9.5.3 eTongue 284

9.5.4 Further Developments in Electronic Flavor Devices 285

9.6 Model Mouth Systems 286

9.7 Real Time Studies of Flavor Delivery 287

9.8 Future Direction of In vitro Flavor Studies 292

9.8.1 Taste Research 292

9.8.2 Taste Cell Model Systems 294

9.8.3 Odor Receptors 295

9.8.4 Sensomics Approach 296

9.8.5 Interaction Effects and Multi�-modal Perception 297

9.8.6 Brain Imaging by fMRI 297

9.9 Summary 298

References 300

Index 305

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