Since 1767, when chemist Joseph Priestley first infused water with carbon dioxide to produce carbonated water—the main ingredient of sodas, sparkling wines, and a variety of carbonated drinks—there has been no scientific explanation of how people taste the carbonation bubbling in their glass. Researchers at the National Institute of Dental and Craniofacial Research (NIDCR) and their colleagues from the Howard Hughes Medical Institute at the University of California, San Diego, report that they have discovered the answer in mice, whose sense of taste closely resembles that of humans. They found that the taste of carbonation is initiated by an enzyme tethered like a small flag from the surface of sour-sensing cells in taste buds. The enzyme, called carbonic anhydrase 4 (CA-IV), interacts with the carbon dioxide in the soda, activating the sour cells in the taste bud and prompting it to send a sensory message to the brain, where carbonation is perceived as a familiar sensation.
(Source: NIDCR, October 15, 2009)