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Humans can 'taste' carbon dioxide in fizzy drinks

The human tongue can taste the "flavour" of carbon dioxide in the bubbles of fizzy drinks, which may explain why flat Champagne is not so much fun as drinking it fresh from the bottle.

Scientists have found that taste receptors on the tongue which detect the flavour of sour food can also respond to the gases of carbonated or fermented drinks, which may explain why the bursting of Champagne bubbles on the tongue is so pleasurable.

Charles Zuker, a neuroscientist at Columbia University in New York, found that a class of taste-receptor cells in the tongue respond to carbon dioxide, and specifically identified an enzyme called carbonic anhydrase 4 in the detection of the gas. Previous research had concluded that the tingling sensation produced from fizzy drinks was due to the bursting of CO2 bubbles but the new research revealed that the way we taste may also be responsible.

The study, published in the journal Science, was carried out on laboratory mice genetically modified to lack sour-sensing taste cells. The scientists found that the mice also lacked the ability to detect carbon dioxide in carbonated water, but those that retained the sour-sensing cells showed a neurological response when drinking carbonated water.

The finding could explain why champagne, beer and other fizzy drinks taste flat and uninteresting when people are given acetazolamide, a prophylactic taken to avert altitude sickness. The drug is also known to inhibit the carbonic anhydrase 4 enzyme in the sourness taste receptors of the tongue.