Kokumi Substance as an Enhancer of Koku: Biochemistry, Physiology, and Food Science

Preface
Contents
Contributors
Part I: General Concept
	Chapter 1: Koku Perception and Kokumi Substances
		1.1 Definition of ``Koku Perception´´
			1.1.1 Koku Perception by Foods
			1.1.2 ``Koku´´ and ``Deliciousness´´ Are Not Synonymous
			1.1.3 Definition of ``Koku Perception´´
		1.2 Three Elements Involved in ``Koku Perception´´
			1.2.1 Complexity in Koku Perception
			1.2.2 Mouthfulness in Koku Perception
			1.2.3 Lastingness in Koku Perception
		1.3 Substances Involved in Each Element of Koku Perception
			1.3.1 Substances Involved in the Complexity of Koku Perception
			1.3.2 Substances Involved in the Mouthfulness of Koku Perception
			1.3.3 Substances Involved in the Lastingness of Koku Perception
		1.4 Kokumi Substances Enhancing the Intensity of Koku Perception
		References
	Chapter 2: Kokumi Substance as an Enhancer of Koku: Its Definition
		2.1 Classification of Koku-Enhancing Substances
			2.1.1 Taste-Related Koku-Enhancing Substances
			2.1.2 Odor-Related Koku-Enhancing Substances
			2.1.3 Texture-Related Koku-Enhancing Substances
		2.2 Kokumi Substance; Its Definition
		References
Part II: Kokumi γ-Glutamyl-Peptides
	Chapter 3: Biochemical Studies on Kokumi γ-Glutamyl Peptifdes
		3.1 Discovery of Glutathione as a Kokumi Substance
		3.2 Kokumi γ-Glutamyl Peptides in Beans
		3.3 Kokumi γ-Glutamyl Peptides in Fermented Foods
			3.3.1 Cheese
			3.3.2 Soy Sauce
			3.3.3 Fermented Fish Seasonings
		References
	Chapter 4: Kokumi Substances from Garlic; Discovery of Glutathione (GSH; γ-Glu-Cys-Gly) as a Kokumi Substance
		4.1 Introduction
		4.2 Identification of Kokumi Substances in Garlic
		4.3 Assessment of Threshold Values of GSH in Water and Umami Solutions
		4.4 Sensory Characteristics of GSH in Reconstituted Model Extracts
		4.5 Quantitative Analysis of GSH in Various Foods
		References
	Chapter 5: Kokumi Substances in Soybean Seeds
		5.1 General Introduction
			5.1.1 General Description of Soybean Products
			5.1.2 Flavor and Taste Components in Soybean
			5.1.3 Contribution of Kokumi Substances to Food Palatability
			5.1.4 Analytical Methods for Studying Kokumi Substances
			5.1.5 Scope of This Research
		5.2 Isolation and Characterization of the Key Kokumi Substances in Soybean Seeds
			5.2.1 Introduction
			5.2.2 Materials and methods
				Materials
				Fractionation of Water-Soluble Components from Soybeans
				Identification and Quantitative Analysis of Kokumi Substances
				Sensory Analysis
				Statistical Analysis
			5.2.3 Results and Discussion
				Taste-Improving Effects of Soybean Seeds
				Isolation of the Key Kokumi Substances
				Structure Determination of the Kokumi Substances
				Quantitative Analysis of the Kokumi Substances
				Sensory Analysis of Kokumi Substances
			5.2.4 Conclusions
		5.3 Diversity of γ- Glutamyl Peptides and Oligosaccharides, the Kokumi Substances, in Seeds from Soybean Mini Core Collections
			5.3.1 Introduction
			5.3.2 Materials and Methods
				Materials
				Extraction of γ-Glutamyl Peptides and Oligosaccharides
				Liquid Chromatography-Quadrupole-Time-of-Flight-Tandem Mass Spectrometry Analysis
				Quantitative Analysis of γ-Glutamyl Peptides and Oligosaccharides
				Statistical Analysis
			5.3.3 Results and discussion
				Quantification of the Concentrations of γ-Glutamyl Peptides and Oligosaccharides in the Mini Core Collections
				Profiles of the Concentrations of the γ-Glutamyl Peptides and Oligosaccharides in Soybean Seeds
				Diversity of the Concentrations of the γ-Glutamyl Peptides and Oligosaccharides in the Japanese Mini Core Collection (JMC) and...
				Correlation Analysis Between the Content of the γ-Glutamyl Peptides and Oligosaccharides
			5.3.4 Conclusions
		References
	Chapter 6: Kokumi Substances in Thai-Fermented Freshwater Fish, ``Pla-ra´´
		6.1 What Is Pla-ra?
		6.2 Pla-ra and Thai Cuisine
		6.3 Production Process of Pla-ra
		6.4 Taste-Active Compounds in Pla-ra
		6.5 Mouthfulness of Pla-ra
		6.6 Raw Materials and Kokumi Substance Formation
		6.7 Diversity of Bacteria in Pla-ra and Their Potential Roles in Kokumi Substance Creation
		6.8 Conclusion
		6.9 Future Forward
		References
	Chapter 7: Identification and Quantification of the Kokumi Peptide, γ-Glu-Val-Gly, in Foods
		7.1 Introduction
		7.2 Materials and Methods
			7.2.1 Materials
			7.2.2 Sample Preparation and Derivatization Procedure
			7.2.3 Identification and Quantification of AQC-Derivatized γ-Glu-Val-Gly
			7.2.4 Statistical Analysis
		7.3 Results
			7.3.1 Validation on the Identification of γ-Glu-Val-Gly in Food Samples
			7.3.2 Quantification of γ-Glu-Val-Gly in Raw or Cooked Foods
			7.3.3 Analysis and Quantification of γ-Glu-Val-Gly in Fermented Foods
				Fish Sauces
				Soy Sauces
				Fermented Shrimp Pastes
				Brewed Alcoholic Beverages
				Cheeses
		7.4 Discussion
			7.4.1 Development of Methods to Identify and Quantify γ-Glu-Val-Gly in Foods
			7.4.2 γ-Glu-Val-Gly in Raw and Cooked Foods
			7.4.3 γ-Glu-Val-Gly in Fish Sauces
			7.4.4 γ-Glu-Val-Gly in Soy Sauces
			7.4.5 γ-Glu-Val-Gly in Fermented Shrimp Pastes
			7.4.6 γ-Glu-Val-Gly in Beer
			7.4.7 γ-Glu-Val-Gly in Cheeses
			7.4.8 Mechanism Underlying the Synthesis of γ-Glu-Val-Gly in Fermented Foods
		7.5 Conclusion
		References
	Chapter 8: Mechanism for Perceiving Kokumi Substances: Involvement of Calcium-Sensing Receptor (CaSR) in the Perception of Kok...
		8.1 Introduction
		8.2 Materials and Methods
			8.2.1 Materials
			8.2.2 Assessment of CaSR Activity Using HEK-293 Cells
			8.2.3 Sensory Analysis of CaSR Agonists
			8.2.4 Quantitative Analysis of Sensory Intensities of Kokumi Substance Relative to GSH
			8.2.5 Sensory Evaluation of Effects of GSH and γ-Glu-Val-Gly on Basic Taste Solutions and Foodstuffs
		8.3 Results
			8.3.1 CaSR Activity of GSH, a Representative Kokumi Substance
			8.3.2 Properties of Known CaSR Agonists as Kokumi Substances
			8.3.3 Inhibitory Effects of the CaSR Antagonist, NPS-2143, on Sensory Effect of GSH and γ-Glu-Val-Gly
			8.3.4 Relationships Between CaSR and Sensory Intensities of Kokumi Substance of γ-Glutamyl Peptides
			8.3.5 Effects of GSH and γ-Glu-Val-Gly on Basic Taste Solutions and Foodstuffs
		8.4 Discussion
		References
	Chapter 9: Molecular Mechanism of Enhancement in Basic Tastes by Kokumi Substances: A Potent Calcium-Sensing Receptor (CaSR) A...
		9.1 Introduction
		9.2 Materials and Methods
			9.2.1 Animals
			9.2.2 Taste Bud Isolation
			9.2.3 Cellular Biosensor Technique
			9.2.4 Immunohistochemistry
			9.2.5 Reagents and Solutions
			9.2.6 Data Analysis
		9.3 Results
			9.3.1 A CaSR Agonist Enhances Sweet-Induced ATP Secretion
			9.3.2 Acetylcholine Mediates the γEVG-Induced Enhancement of the Sweet Taste Response
			9.3.3 Taste Cells that Express T1R3 Also Express Muscarinic Acetylcholine Receptors
			9.3.4 CaSR Stimulation Induces Release of Acetylcholine from Taste Buds
		9.4 Discussion
		References
	Chapter 10: Enhancement of Combined Umami and Salty Taste by Glutathione in the Human Tongue and Brain
		10.1 Introduction
		10.2 Materials and Methods
			10.2.1 Participants
			10.2.2 Stimuli
			10.2.3 Stimulus Delivery
			10.2.4 Training Session
			10.2.5 Experimental Paradigm and Stimuli in fMRI
			10.2.6 fMRI Data Acquisition
			10.2.7 Sensory Evaluation of Taste with and without Glutathione
				Distinguishing of Solutions with and without Glutathione
				Sensory Evaluation of Taste with and without Glutathione During fMRI
					Evaluation of Taste Quality
					Evaluation of Taste Intensity
			10.2.8 fMRI Data Analysis
			10.2.9 Individual Level Analysis
			10.2.10 Group Analysis
		10.3 Results
			10.3.1 Sensory Evaluation of Taste with and without Glutathione
				Evaluation of Taste Quality
				Evaluation of Taste Intensity
			10.3.2 fMRI Results
				Individual Level Analysis
				Group Analysis
		10.4 Discussion
			10.4.1 Sensory Evaluation of Taste with and without Glutathione
				Evaluation of Taste Quality
				Evaluation of Taste Intensity
			10.4.2 fMRI Data
			10.4.3 Study Limitations and Future Prospects
		References
	Chapter 11: γ-Glutamyl-Valyl-Glycine (γ-Glu-Val-Gly) and Glutathione (γ-Glu-Cys-Gly) as Kokumi Substances in Rodents
		11.1 Introduction
		11.2 γ-Glu-Val-Gly (EVG) Studies in Rats
			11.2.1 Two-Bottle Preference Test
			11.2.2 Taste Nerve Recording
		11.3 Glutathione (GSH) Studies in Mice
		11.4 Other Possible Kokumi Substances and Their Receptors
		11.5 Conclusion
		References
	Chapter 12: Effects of the Potent Kokumi Peptide, γ-Glutamyl-Valyl-Glycine, on Sensory Characteristics of Foods and Beverages
		12.1 Background
		12.2 Effects of γ-Glutamyl-Valyl-Glycine on Sensory Characteristics of Chicken Consommé
			12.2.1 Introduction
			12.2.2 Materials and Methods
				Materials
				Selection of the Panel
				Training of the Panel
				Selection of Sensory Attributes
				Procedure for the Sensory Evaluation
				Statistical Analysis
			12.2.3 Results and Discussion
				Sensory Attributes for Chicken Consommé
				Sensory Characteristics of Chicken Consommé with Added γ-Glu-Val-Gly
			12.2.4 Conclusions and Implications
		12.3 Effects of γ-Glutamyl-Valyl-Glycine on Sensory Characteristics of Hamburger Steak
			12.3.1 Introduction
			12.3.2 Materials and Methods
				Preparation of γ-Glu-Val-Gly
				Preparation of Hamburger Steak with or without γ-Glu-Val-Gly
				Panelists
				Selection of Sensory Attributes
				Procedure for the Sensory Evaluation
				Statistical Analysis
			12.3.3 Results and Discussion
				Selection of Sensory Attributes
				Effects of γ-Glu-Val-Gly on Hamburger Steak
			12.3.4 Conclusions and Implications
		12.4 Effects of γ-Glutamyl-Valyl-Glycine on Sensory Characteristics of Orange Flavored Drink
			12.4.1 Introduction
			12.4.2 Materials and Methods
				Preparation of γ-Glu-Val-Gly
				Preparation of Orange Flavored Drink with or without γ-Glu-Val-Gly
				Panelists
				Selection of Sensory Attributes
				Procedure for the Sensory Evaluation
				Statistical Analysis
			12.4.3 Results and Discussion
				Selection of Sensory Attributes
				Effects of γ-Glu-Val-Gly on Orange Flavored Drinks
			12.4.4 Conclusions and Implications
		12.5 Effects of γ-Glutamyl-Valyl-Glycine on Sensory Characteristics of Reduced-Fat Peanut Butter
			12.5.1 Introduction
			12.5.2 Materials and Methods
				Preparation of γ-Glu-Val-Gly
				Preparation of Reduced- and Full-Fat Peanut Butter
				Sensory Panel
				Selection of Sensory Attributes
				Procedure for the Sensory Evaluation
				Statistical Analysis
			12.5.3 Results and Discussion
				Sensory Attributes
				Sensory Evaluation of Reduced- and Full-Fat Peanut Butter
				Effects of the Addition of γ-Glu-Val-Gly on Reduced-Fat Peanut Butter
			12.5.4 Conclusions and Implications
		12.6 Effects of γ-Glutamyl-Valyl-Glycine on Sensory Characteristics of Reduced-Fat French Dressing
			12.6.1 Introduction
			12.6.2 Materials and Methods
				Preparation of γ-Glu-Val-Gly
				Preparation of Reduced- and Full-Fat French Dressing
				Sensory Panel
				Selection of Sensory Attributes
				Procedure for the Sensory Evaluation
				Statistical Analysis
			12.6.3 Results and Discussion
				Sensory Attributes
				Sensory Evaluation of Reduced- and Full-Fat French Dressing
				Effects of the Addition of γ-Glu-Val-Gly on Reduced-Fat French Dressing
			12.6.4 Conclusions and Implications
		12.7 Effects of γ-Glutamyl-Valyl-Glycine on Sensory Characteristics of Reduced-Fat Custard Cream
			12.7.1 Introduction
			12.7.2 Materials and Methods
				Preparation of γ-Glu-Val-Gly
				Preparation of Reduced- and Full-Fat Custard Cream
				Sensory Panel
				Selection of Sensory Attributes
				Procedure for the Sensory Evaluation
				Statistical Analysis
			12.7.3 Results and Discussion
				Sensory Attributes
				Sensory Evaluation of Reduced- and Full-Fat Custard Cream
				Effects of γ-Glu-Val-Gly on Reduced-Fat Custard Cream
			12.7.4 Conclusions and Implications
		12.8 General Discussion
		References
	Chapter 13: Perceptual and Nutritional Impact of Kokumi Compounds
		13.1 Introduction
		13.2 Impact of Kokumi Compounds on Sensory Perception
			13.2.1 Kokumi Perception and Hedonic Responses
		13.3 Opportunities for Product Reformulation and Energy Content Reduction Using Koku Sensations
		13.4 Outlook: Research Gaps and Future Directions for Koku and Health
		References
Part III: Amino Acids, α-Peptides, and Their Related Kokumi Substances
	Chapter 14: Amino Acids, α-Peptides, and Their Related Kokumi Substances
		14.1 Introduction
		14.2 Kokumi α-Peptides
		14.3 Kokumi N-Acyl-Amino Acids
		14.4 Candidates for Amino Acids and Peptide-Related Kokumi Substances
			14.4.1 Amino Acids
			14.4.2 α-Peptides
			14.4.3 Peptides Modified by the Heating Process
				Maillard Peptides (Peptides Modified by Heating with Xylose)
				Maillard-Reacted Products from Tropomyosin and Collagen
		References
Part IV: Lipid-Related Kokumi Substances
	Chapter 15: Biochemical Studies on Lipid-Related Kokumi Substances
		15.1 Introduction
		15.2 Alkyne-Containing Fatty Acids and Their Derivatives
		15.3 Oxylipins
		15.4 GPR120 Agonists
		References
	Chapter 16: Involvement of GPR120 in Perception of Fatty Oral Sensations in Humans
		16.1 GPR120 Agonists Enhance the Fatty After Orosensation When Added to a Fat-Containing System, but Do Not Evoke It by Themse...
			16.1.1 Introduction
			16.1.2 Materials and Methods
				Materials
				Preparation of Samples for Sensory Evaluations
					Preparation of Emulsions for Comparisons of Mineral and Vegetable Oils
					Preparation of Emulsions for the Evaluation of the GPR120 Agonist, TUG891
				Samples for the Evaluation of Low-Fat Food Systems
				Sensory Evaluations
					General Methods
					Sensory Evaluation of Emulsion Samples
					Measurement of the Point of Subjective Equivalent (PSE) in Low-Fat Dressing
					Sensory Evaluation of Low-Fat Dressing with GPR120 Agonists
					Sensory Evaluation of GPR120 Agonists in Aqueous Solution or a Suspension of Mineral Oil
				Measurement of Physical Properties of Emulsion Samples
				Measurement of Minor Components of Canola Oil
				Assay of GPR120 Activity Using HEK-293 Cells
				Statistical Analysis
			16.1.3 Results
				Physical Properties of Emulsion Samples Prepared from Mineral or Vegetable Oil
				Contents of Minor Components in Canola Oil
				Sensory Evaluation of Emulsions Prepared from Mineral Oil and Vegetable Oil
				Effects of the GPR120 Agonist, TUG-891 on Emulsions Prepared from Vegetable Oil and Mineral Oil
				PSE of GPR120 Agonists in Low-Fat Dressing
				Effects of GPR120 Agonists on the Fatty After Orosensation of Low-Fat Dressing
				Sensory Evaluation of GPR120 Agonists in Aqueous Solution or the Emulsion from Mineral Oil
				Measurement of GPR120 Activity
				Relationship Between Sensory Activity and GPR-120 Activity
			16.1.4 Discussion
			16.1.5 Conclusions
		16.2 Effects of the Potent GPR120 Agonist, TUG-891, on Sensory Characteristics of Whipped Cream
			16.2.1 Introduction
			16.2.2 Materials and Methods
				Materials and Preparation of Samples
				Sensory Evaluation
					Panelists and Ethics Approval
					Selection of Sensory Attributes
					Panel Training
					Sensory Evaluation of Whipped Cream with TUG-891
				Statistical Analysis
			16.2.3 Results and Discussion
				Selection of Sensory Attributes
				Sensory Evaluation of Normal-Fat Whipped Cream with TUG-891
			16.2.4 Conclusion
		References
Part V: Future Prospect
	Chapter 17: Overview and Future Prospects of Studies on Kokumi Substances
		17.1 Definition of a Kokumi Substance
		17.2 Kokumi γ-Glutamyl Peptides
			17.2.1 Biochemical Studies
			17.2.2 Physiological Studies
			17.2.3 Food Science and Sensory Science
		17.3 Amino Acids, α-Peptides, and Their Related Kokumi Substances
		17.4 Lipid-Related Kokumi Substances
		17.5 Future Prospects of Studies on Kokumi Substances