60秒科学:Carbonation Has a Taste（在线收听）

Carbonation Has a Taste
In a study in the journal Science, researchers found that the taste buds for sensing sour also respond to carbonated beverages, because the fizz gets turned into chemical components, one of which is protons--basically simple, sour acid. Karen Hopkin reports

If you’ve ever craved an ice-cold soda, you know that sometimes you’re just looking for something that tastes…fizzy. If that sounds odd, scientists have discovered that carbonation actually has a flavor. And that our taste buds can sense CO2.

Bubbly soft drinks tickle our tongues with their effervescence. But researchers got to wondering whether we can taste the carbonation. To find out, they studied mice whose taste cells had been turned off, one flavor at a time. So, one mouse couldn’t taste sweet things, another couldn’t taste bitter, a third couldn’t taste salt, and so on. And they found that mice lacking the cells that sense the taste sour no longer respond to CO2.

Probing further, they discovered that eliminating a single gene renders these mice blind, if you will, to the taste of carbonation. That gene encodes an enzyme that breaks down CO2—and water…don’t forget the water—into bicarbonate and protons. And it’s the protons—which are essentially acid—that the sour-sensitive cells seem to sense. The work appears in the journal Science.

The scientists speculate that our CO2 sensor evolved to help us avoid food that’s spoiled. Yet we still like some of our drinks to include the delightfully acidic tingle of a touch of CO2.

—Karen Hopkin