Bitterness

Michel Aliani is Associate Professor and Director of sensory research studies in the Human Nutritional Sciences department at the University of Manitoba, Canada. Dr. Aliani has expertise in flavor chemistry and mass spectrometry systems, and is interested in flavouromics, studies of functional foods which are destined to nutritional interventions and, in metabolomics, studies of biological fluids after ingestion of functional foods. Michael N. A. Eskin is Professor in the Department of Human Nutritional Sciences, Faculty of Agricultural and Food Sciences, University of Manitoba, Canada. Dr. Eskin has published over 120 research papers, 50 chapters and 13 books. He is the recipient of a number of awards, including the 2012 IFT Stephen S. Chang Award and the Alton S. Bailey Medal Award by the American Oil Chemists' Society for his research in lipids. In 2016, he received the Order of Canada for his pioneering research which contributed to the success of the Canadian canola industry. Dr. Eskin is also a fellow of IFT, The American Oil Chemists' Society, Canadian Institute of Food Science and Technology, and Institute of Food Science and Technology in the UK. He is a co-editor of Lipid Technology.

• List of Contributors xiiiPreface xvSECTION I THE BIOLOGY OF BITTERNESS PERCEPTION 11 Biochemistry of Human Bitter Taste Receptors 3Jasbir Upadhyaya, Nisha Singh, Raj Bhullar, and Prashen Chelikani1.1 Introduction 31.2 Bitter taste receptors: T2Rs 31.3 T2R signal transduction 51.4 Bitter taste perception and T2R polymorphisms 61.5 Ligand binding and activation mechanisms of T2Rs 81.6 Nutrigenomics of taste 101.7 Bitter taste blockers 121.8 Expression of T2Rs in extraoral tissues 121.9 Conclusion 13Acknowledgement 14References 142 Physiological Aspects of Bitterness 21Maik Behrens and Wolfgang Meyerhof2.1 Introduction 212.2 Anatomy 212.3 Taste signal transduction 232.4 Gustatory bitter taste receptor gene expression 242.5 Extragustatory bitter taste receptors 282.6 Outlook 31Acknowledgements 31References 313 Bitterness Perception in Humans: An Evolutionary Perspective 37Hui Yang and Peng Shi3.1 Bitter taste receptors - A group of G protein-coupled receptor (GPCR) members 383.2 Tas2R gene family - A highly diverse family in vertebrates 383.2.1 Bitter taste receptors - a group of G protein-coupled receptor (GPCR) members 383.3 The evolution of Tas2R gene family in vertebrates 403.4 Diverse selective forces drove the evolution of Tas2R genes in primates 413.5 Genetical basis of tasteblindness – human PTC perception as an example 433.6 PTC tasteblindness in humans and chimpanzees - shared phenotype resulted from unshared genotypes 443.7 Closing remarks 45Acknowledgement 46References 46SECTION II THE CHEMISTRY OF BITTERNESS 494 Fruits and Vegetables 51Ernst Hoehn and Daniel Baumgartner4.1 Introduction 514.2 Fruits 564.2.1 Flavonoids, flavonols and limonoid aglycones in grapefruit, orange and lemons 564.2.2 Cyanogenic glycoside in apricot, almonds and other species 584.3 Vegetables 604.3.1 Brussels sprouts, cabbage, cauliflower, turnips/Swedes and collards and kale: glucosinolates/isothiocyanates and phenolics 604.3.2 Carrots: 6-Methoxymellein, polyacetylenes and phenolic acids 634.3.3 Potatoes, tomatoes and other solanum species: glycoalkaloids 664.4 Future progress 68References 685 Bitterness in Beverages 81Ayyappan A. Aachary and N. A. Michael Eskin5.1 Introduction 815.2 Bitterness in tea 815.3 Bitterness in coffee 835.4 Bitterness in cocoa/hot chocolate 865.5 Bitterness in beer 875.6 Bitterness in wine 905.7 Bitterness in cider 92References 946 Structural Characteristics of Food Protein-Derived Bitter Peptides 103Rotimi E. Aluko6.1 Introduction 1036.2 Bitter peptides preparation and taste evaluation 1076.3 Role of amino acid composition and position arrangement in determining peptide bitterness intensity 1086.3.1 Relationship between peptide hydrophobicity and bitterness intensity 1086.3.2 Influence of peptide chain length and N- or C-terminal amino acid residue 1096.3.3 Amino acid type and position on peptide chain 1116.3.4 Influence of amino acid isomeric configuration 1176.4 Peptide Debittering Methods 1176.4.1 Peptide complexation 1176.4.2 Hydrophobic column adsorption 1206.4.3 Enzyme treatment 1216.5 Conclusions 123Acknowledgement 123References 123SECTION III ANALYTICAL TECHNIQUES FOR SEPARATING AND CHARACTERIZING BITTER COMPOUNDS 1297 Sensory Evaluation Techniques for Detecting and Quantifying Bitterness in Food and Beverages 131Donna Ryland, Erin Goldberg, and Michel Aliani7.1 Screening methods 1317.2 Test methods 1327.3 Techniques to maximize bitterness perception 1377.4 Use of standards 1387.5 Conclusion 139References 1538 Analysis of Bitterness Compounds by Mass Spectrometry 159Geraldine Dowling8.1 Introduction 1598.2 Overview of LC-MS 1638.2.1 Electrospray ionisation 1638.2.2 Solvents 1648.2.3 Additives 1648.2.4 pH 1658.2.5 Adduct formation 1668.2.6 Ion-Pairing and ion exchange 1668.3 Data acquisition in LC-MS 1678.3.1 Targeted compound screening 1678.3.2 Non-targeted compound (retrospective) screening 1678.3.3 Ion annotation 1698.3.4 Mass-based identification 1698.3.5 Spectral interpretation 1708.3.6 Spectral matching 1708.3.7 Compound identification 1718.4 LC-MS application of bitterness compounds 1728.4.1 Bitter compound quantitation by triple quadrupole and selected ion monitoring 1728.4.2 Quantitation of bitter compounds by LC-IT-MS and LC-HRMS 1758.5 Challenges and future perspectives 1788.6 Optimisation of mass spectra parameters 1798.7 Recording of MSn profile 1798.8 Challenges in the collection of HRMS data 1838.9 Conclusions 185References 1869 Evaluation of Bitterness by the Electronic Tongue: Correlation between Sensory Tests and Instrumental Methods 193Michel Aliani, Ala’a Eideh, Fatemeh Ramezani Kapourchali, Rehab Alharbi, and Ronak Fahmi9.1 Introduction 1939.2 The electronic tongue 1939.2.1 Sensor arrays 1949.2.2 Data processing 1959.3 The electronic tongue and food production 1959.4 Electronic tongue and bitterness 1979.5 Evaluating bitterness in food products using electronic tongues 1989.6 Conclusion 202References 202SECTION IV METHODS FOR REMOVING BITTERNESS IN FUNCTIONAL FOODS AND NUTRACEUTICALS 20710 Methods for Removing Bitterness in Functional Foods and Nutraceuticals 209Erin Goldberg, Jennifer Grant, Michel Aliani, and Michael Eskin10.1 Introduction 20910.2 Reducing and removing bitter components 21010.2.1 Physical methods 21010.2.1.1 Temperature treatment 21010.2.1.2 Ion exchange and adsorbent resins 22210.2.1.3 Extraction with sub-critical water 22210.2.2 Chemical methods 22210.2.2.1 Fermentation 22210.2.2.2 Aging and polymerization of phenols 22310.2.2.3 Alkalization 22310.2.3 Masking techniques 22410.2.3.1 Flavorings 22410.2.3.2 Amino acids 22610.2.3.3 Aroma additions 22610.2.3.4 Gluconate and acetate 22810.2.3.5 Lipids: phospholipids and fatty acids 22810.2.3.6 Zinc, lactate, and acetate 22810.2.4 Bitter blockers 22910.3 Conclusion 231References 232Index 237