Solving a Bubbly Puzzle: How We Taste Carbonization

By Brett Israel | October 16, 2009 1:46 pm

big-gulp_webCracking open a cold can of Coke and taking a bubbling swig will have your taste buds dancing—and now scientists know why. A new study shows that cells in taste buds that respond to sour stimuli also seem to be the ones responsible for tasting the carbonation’s fizz [NPR].The fact that we can taste the carbon dioxide in a fizzing soda has previously puzzled scientists, since the human tongue is usually thought to only sense five flavors—bitter, sweet, salty, sour, and umami (also called savory). However, the new study, published in Science, shows that the sour taste buds have an enzyme that interacts with carbon dioxide, so it’s not the bursting bubbles that you taste, it’s the C02 itself.

The researchers discovered this tricky bit of chemistry by studying mice. They gave the animals sips of club soda or a little buzz of carbon dioxide gas and recorded how the tongue signaled the sensation to the brain. Both soda and the gas produced similar sensations. But when they tested mice bred to have no sour taste buds, the brain never got its sensory alert. Further probing uncovered the enzyme responsible [AP]. The mechanism should be the same in humans, according to the scientists.

The discovery of a C02-sensing taste bud is not only interesting to soft drink manufacturers, but also to evolutionary biologists. After all, Coca-Cola didn’t usher in a new era of carbonated beverages until the late 1800s, so why would our sour-tasting cells have evolved to taste carbon dioxide? The study’s authors write, “CO2 detection could have evolved as a mechanism to recognize CO2-producing sources—for instance, to avoid fermenting foods.” One happy irony of such a hypothesis is that the very same mechanism that allowed our deep ancestors to recognize and avoid fermentation allows modern humans to intentionally create the fermented beverages beer and champagne. Or, our carbonation-detecting skills could be an accident. The sour-cell enzymes might be maintaining the pH balance of the taste buds, and the tang of soda water is just fallout [].

Related Content:
DISCOVER: Sliced: Building a Better Bubbly
80beats: Fabulous Fizz: How Bubbles Make Champagne Burst With Flavor
80beats: Human Taste Buds May Recognize a Sixth Flavor: Calcium
80beats: Revealed: The Genetic Root of Seeing Sounds and Tasting Colors

Image: flickr / roland

MORE ABOUT: chemistry, senses, taste
  • winspire

    Who would have thought that our sour-detecting taste buds have a connection with bubbles. Interesting. There is a bigger problem with the fizz- the acidity level eats away at teeth and lowers one’s pH levels into the below neutral zone.

    Also, about 20% of calories now come from sugared drinks of one variety or the other, and recent decades are the first time in history where a culture as ours sees them as normal, though they are not normal or healthy for the body- and at great expense.

    Getting into the habit of eating at least 1 thing green helps, and more if you will, but doing something on a sustainable level is key. Also, there are products on the market now that can make a huge difference in the acidity which is key. One fascinating website on this is

    As far as sweet drink lovers who want energy, a new all-natural drink that is sweet but has no sugars of any kind is found at . It’s too bad that in many cases the really exceptional products are not found in the grocery store, and many folks never find solutions.

    Often, it’s just trading 1 or 2 bad detrimental things in the diet for something good that makes all the difference.

  • marcy

    we were taught in high school that basic foods tasted bitter and acidic food tasted sour. isn’t dissolved carbon dioxide an acid? i may be wrong, but isn’t it carbonic acid? if that’s the case, why is it a big discovery that it is sensed by the sour taste receptors?

  • Christina Viering

    Thinking of how the mice were tested is giving me the creeps.

  • Jo

    Fascinating…So much more to learn about CO2 it seems

    I’ve often wondered if the CO2 we ingest so much of could be combining with our calcium (from bones and teeth!) to form calcium carbonate…I keep meaning to research this more, because if so then we aren’t just turning into little CO2 storage units, we’re actually degrading our bones/teeth to do it !

    Surely there’s a safer was to store CO2 😉

    BTW: I’m writing about an interesting CO2 capture method that uses the same enzymatic process that our lungs do !

  • Nessy

    I agree with you guys. Fizzy drinks aren´t healthy and they can make you feel sick. I feel far better since I´ve switched to tea!


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