Taste perception and integration
Résumé
Introduction
The sense of taste is essential for the evaluation of food quality. It allows, at the level of the oral cavity, to evaluate the caloric content of the consumed food, to detect the presence of salt, and protect us against the ingestion of toxic molecules. Our gustatory system allows the perception of different food constituents as alkali metallic salts (salty), acids (sour), sugars (sweet), and bitter compounds. Umami is a different taste, arising from the perception of amino acids, such as l-glutamate, and 5′-ribonucleotides. Other taste qualities are still a matter of debate, including fat taste, corresponding to the taste of fatty acids (Khan and Besnard, 2009), metallic taste, and the kokumi taste that is related to mouthfulness, thickness, and long-tasting savory sensations (Maruyama et al., 2012). This last taste sensation does not refer to an independent taste quality, but correspond more to a reinforcement of other taste qualities. Another class of compounds present in many foods or aromatic spices is named trigeminal stimuli. These chemical compounds that are present in mustard oil, chili peppers, or horseradish, are responsible for pungency. Other trigeminal stimuli such as menthol or eucalyptol are also responsible for cooling sensations. Astringency is another trigeminal sensation, described as a dry mouthfeel that is generated by particular foods (unripe fruits) or drinks (tea or red wine), which are rich in polyphenolic compounds such as tannins. The objective of this chapter is, first, to review the different molecules responsible for each basic taste, with, additionally, a short overview on trigeminal molecules. A second objective is to describe the physiology of taste at both the peripheral and central levels; the final objective is to present taste–taste interactions. Physiological mechanisms involved for each basic taste at the peripheral level are presented in Fig. 4.1. Several examples are presented in this chapter, but not exhaustively. Complementary examples can be found in the book chapters by Behrens and Meyerhof (2016), Laffitte et al. (2016), Thomas-Danguin et al. (2016).