Why Does Carbonation Affect The Taste?

Why is it that when a soda goes flat- that is, it loses its dissolved carbon dioxide- that it just doesn’t taste the same? The ingredients are still the same. What happened??

Why should the ‘fizziness’ of a soda affect the flavor?

Thanks.

Warning: a little bit of a WAG ahead

Dissolved carbon dioxide in water actually creates a weak acid (Carbonic acid - H[sub]2[/sub]CO[sub]3[/sub]). I think the acid has a flavor of its own - sort of tart and sour - that balances the sweetness of the soda.

I like seltzer which is unsweetened carbonated water (sometimes with flavoring). It definitely does not taste just like normal water with bubbles.

Then again seltzer doesn’t taste like water when flat either

Carbon dioxide gas does have a flavor to it. A somewhat bitter one. This is why whipped cream is made with nitrous oxide. N[sub]2[/sub]O has a sweet taste.

Soda water is jsut CO2 in water and it definatly tasts bitter.

Why doesn’t soda water taste like water when allowed to go flat?

You have two things here, I believe: Soda water is not nec. the same as Seltzer water.

Seltzer water is just Water with CO2 dissolved in it.

Soda water (i.e., club soda) has sodium bicarbonate in it (whence come the CO2 bubbles). So you’ll still have some byproduct left over once the CO2 leaves.
If plain seltzer tastes different than plain water when it goes flat, that’s news to me. Never noticed any difference.

A lot of what we think is taste is actually “mouth feel”, and carbonated water will certainly have a different mouth feel from flat water.

Let some dry ice bubble through water for awhile. Taste it. It tastes exaclty like soda water.

Spray a slow flow of CO2 at your tongue for awhile (perhaps using dry ice chunks in a small plastic bottle.) Your saliva will taste like soda water.

After becoming “sensitized” to this effect, I think I once detected CO2 in a small room crammed full of people. The room was extremely stuffy, and I started to get that very slight soda-water taste in my mouth.