Aside from the natural and artificial flavors and sweeteners, soda and other fizzy beverages have a distinct carbonated taste. It is difficult to describe, but you know it is there when tiny bubbles of carbon dioxide go crazy all over your tongue.

Scientists once thought that all the bubble popping, in fact, is what accounted for the tingly taste of carbonation. But that idea was disproved by studies in which carbonated beverages consumed in a pressurized environment, in which no bubbles formed, produced the same taste.

So the mystery of carbonation remained, until now. In a paper in Science, researchers report that carbonation is tasted on the tongue by the same receptors that detect sourness.

Image Credit... Chris Gash

Jayaram Chandrashekar of the University of California, San Diego, Charles S. Zuker, formerly of U.C.S.D. and now at Columbia, and colleagues used mice in their studies, implanting electrodes in a nerve leading from taste receptor cells in the tongue. When the tongue was exposed to club soda or even just to gaseous CO2, there was a measurable response in the nerve.