How Tongues Taste the Carbonation in a Fizzy Beverage

This is from New York Times.

http://www.nytimes.com/2009/10/20/science/20obfizz.html?ref=science

This suggested that taste receptors were responsible. But there are receptors for five tastes: sweet, sour, salty, bitter and umami (sometimes termed savory). They repeated the experiment using mice that had been genetically engineered without one type of receptor. Those without sour receptors showed no response to the carbonation, indicating that those receptors were responsible.

The researchers also looked at the genes in sour taste receptors, and identified one, called Car4, that encodes an enzyme that is known to be involved in sensing carbon dioxide in the body. The enzyme helps convert CO2 into bicarbonate ions and free protons. Since bicarbonate does not stimulate taste receptors, the researchers said, it is probably the protons that are responsible.

But the researchers note that carbon dioxide doesn’t really taste sour. So the ultimate perception of carbonation may involve other senses as well, including the mechanical stimulus of all those popping bubbles.