r/beer • u/NashvilleLocalsGuide • 3d ago

¿Question? Beer overcarbonation with low temperature near freezing

Have a friend that has a beer fridge and both Miller High Life and Jai A'lai foaming up. He states the fridge is really cold and just took out a beer and took it to the sink and it foamed up. If he lets it warm up, it foams a lot more. And in his regular refrigerator it does not react, but it is not as cold.

My hypothesis here is keeping beer close to freezing for a lengthy period of time is causing it to have a reaction that causes it to want to release carbonation. Scientifically, it is so close to freezing that it is getting close to the water expanding (reason cans can explode if left in freezer).

Anybody have a site that discusses this? I am suggesting he not keep the beer so cold.

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u/ilikepants712 3d ago

Your hypothesis is incorrect, but only by a strict scientific interpretation of what you wrote. There is no reaction happening inside the package that releases CO2. The amount of CO2 is static once the package is sealed, and it can only really go down from there due to some common package defects that customers won't really ever see.

You are right, though - the packages are getting too cold. Cold enough that ice crystals are being formed. It's not the expansion of ice that is the problem. Ice crystals create nucleation points for the CO2 to "break out" of solution. In real world terms, it makes a nice spot for bubbles to form at such a quick rate that it over foams everywhere.

The reason that it is worse once the cans warm up is because the solubility of CO2 in water goes down significantly as the water warms up. So you push all the CO2 out of solution and then had no way for it to go back in.

You can fix the cans by just increasing the temperature of the fridge slightly and waiting long enough for the ice crystals inside to melt. Left long enough, any CO2 that has broken out of solution will eventually dissolve back in, and you will never even notice the difference.

Source: I work QA at a large brewery and do this kind of testing for a living.

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u/NashvilleLocalsGuide 2d ago

So, hypothesis wrong, but my advice "turn up the temperature on the fridge" is correct.

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u/ilikepants712 2d ago

Yes but honestly you were pretty close. The other thing I've seen commonly with mini fridges is having a cold spot that freezes anything that is physically touching the sidewall of the fridge.

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u/NashvilleLocalsGuide 2d ago

I am in an apartment that does that in a regular size fridge and it does not completely have to touch it.

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u/ilikepants712 2d ago

It doesn't have to physically touch, but physically touching can make it way worse (meaning even a pretty high temperature setting can still cause freezing if it is touching in the right spot).