taste, response to chemical stimulation that enables an organism to detect flavors. In humans and most vertebrate animals, taste is produced by the stimulation by various substances of the taste buds on the mucous membrane of the tongue. A taste bud consists of about 20 long, slender cells; a tiny hair projects from each cell to the surface of the tongue through a tiny pore. The taste cells contain the endings of nerve filaments that convey impulses to the taste center in the brain. Five fundamental tastes, or a combination of these, can be detected by the buds: sweet, sour, salt, bitter, and umami. Umami, a savory taste triggered by glutamate, inosinate, and guanylate and associated with protein-rich foods, was identified by Kikunae Ikeda in Japan in the early 20th cent., and umami receptors were only discovered in 1996. Only the buds most sensitive to salty flavor are scattered evenly over the tongue. Sweet-sensitive taste buds are more concentrated on the tip of the tongue, sour flavors at the sides of the tongue, and bitter and umami flavors at the back. The close relationship of taste to smell gives the impression that a greater variety of tastes exists. This is also why an impairment of smell, as during a cold, may impart the feeling that the sense of taste is diminished.

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