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Mammalian Taste Buds

Being a gourmet chef or a gourmand is a matter of more than just good taste; it requires highly functional taste buds. The human mouth and nose feature thousands of different biochemical receptors that bind odorants and allow the brain to decode diverse signals for a plethora of tastes. In spite of the large number of receptors and codes, only five main tastes are distinguishable - sweet, bitter, sour, salty, and Umami (or Unami).

View a high magnification image of mammalian taste buds.

Traditionally, Western scientists have thought taste sensation to be limited to only the first four of the five listed tastes, while the Chinese literature added a fifth, hot (in the sense of "spicy"). In Japan, hot is replaced by Umami, which is argued to have its own taste receptor on the tongue. Japanese researchers include hot with metallic and astringent as the three tastes that stimulate both the taste buds and the mucus membranes of the mouth. The tastiness factor, Umami seibun, according to the Japanese, is associated quite specifically with certain amino acids, sugars, and nucleotides, most notably the food flavor enhancers monosodium glutamate (MSG), sodium inosinate, and sodium guanylate. Umami is naturally found in seaweed, tomato juice, Parmesan cheese, mushrooms and other edible fungi, aged cheeses, and protein-rich foods such as steaks and seafood, and is marketed as a synthesized flavor enhancer. Recently, scientists at the University of Miami (Florida) discovered the biochemical receptor for Umami, thus adding credence to a fifth taste sensation.

There are five main regions that contain taste buds: the epiglottis, circumvallate papillae, fungiform papillae, geschmackstreifen, and the foliate papillae. Biochemists often utilize the laboratory rat as a source of mammalian foliate papillae for experimentation. Onion-shaped taste buds reside in the papillae, the soft protuberances that cover the upper and side surfaces of the mammalian tongue. The foliate papillae are located along the sides of the human tongue toward the rear of the mouth. They are sensitive to both sourness and bitterness, and may have served as an adaptation for avoidance of eating toxic substances or foods laced with them.

Contributing Authors

Cynthia D. Kelly, Thomas J. Fellers and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.



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