The primary processes of taste perception for these modalities are now better understood. Within the bitter taste quality, for instance, tens of different receptors exist. The mechanism for the response of more polar tastants with salty, sour and alkaline qualities has been proposed. The coming years will see the development of a practical use of TRs in vitro on membranes or chips to determine the quality and intensity of tastants in flavors, foods or beverages.
For the maintenance of life and species, every living organism — including humans — needs nutrition, e.g., food and drink. To fi nd, select and appreciate nutrients requires both physical (touch, sight and hearing) and chemical (smell and taste) means. The chemical communication for the sense of taste in vertebrates starts in the mouth with the intake of water- or saliva-soluble tastants. Papillae with taste buds containing nerve cells with TRs are situated on the tongue, palate and larynx. Those TRs can distinguish among sweet, bitter, umami, fatty, salty, sour and alkaline tastants. Whereas sweet taste perception may provide information about palatable food, the bitter modality may warn and protect against the ingestion of poisonous materials. (Many naturally occurring poisonous substances taste bitter to humans.) Because all animals show an aversion to bitter-tasting compounds, it may be concluded that bitter perception is a defense mechanism against the intake of harmful substances, which, in turn, may explain why mammals possess a large number of bitter TRs.
Topics covered: taste perception; previous research; the primary mechanism of taste perception; umami, bitter and sweet taste modalities; fatty taste; salty, sour and alkaline tastes; pain perception and mouthfeel; behavioral studies of taste perception; application of recent findings