October 16, 2009

How Humans Taste Fizz

Scientists have found out how people can taste the bubbly sensation from carbonated beverages.

The answer appears to lie in an enzyme on the surface of sour-sensing cells in taste buds, researchers reported in the journal Science.

Researchers at National Institutes of Health's National Institute of Dental and Craniofacial Research (NIDCR) and colleagues from the Howard Hughes Medical Institute at the University of California, San Diego (UCSD) used mice in their study.

Mice have a similar sense of taste to that of humans.

Researchers found that the enzyme, known as carbonic anhydrase 4, is responsible for the taste of carbonation in drinks.

The enzyme activates the sour cells in the taste buds, which sends a sensory message to the brain.

"Of course, this raises the question of why carbonation doesn't just taste sour," said senior author Nicholas Ryba, from NIDCR.

"We know that carbon dioxide also stimulates the mouth's somatosensory system. Therefore, what we perceive as carbonation must reflect the combination of this somatosensory information with that from taste."

The carbonation taste is delivered to the brain as a familiar sensation. Common sensory information includes taste, touch, pain and temperature, scientists said.

"When people drink soft drinks, they think that they are detecting the bubbles bursting on their tongue," he said.

"But if you drink a carbonated drink in a pressure chamber, which prevents the bubbles from bursting, it turns out the sensation is actually the same. What people taste when they detect the fizz and tingle on their tongue is a combination of the activation of the taste receptor and the somatosensory cells. That's what gives carbonation its characteristic sensation."

The human tongue contains taste buds to sense bitter, sweet, salty, sour and umami (savory) flavors.


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