TASTE RECEPTORS. “Two families of taste receptors exist, sweet (TASIRI, TASIRI5), and bitter (TASZRI, TASZR50, and TASZR60), which when combined in dimers or other complexes give the perception of taste. In addition, visual, olfactory, trigeminal and mechanical mechanisms contribute. Hot tastes (chili pepper) are sensed by vanilloid receptor family, and cool tastes such as mint by CMRI receptors.”
http://en.m.wikipedia.org/wiki/Taste_receptor