This winter we had a party at my house and we set the beer outside on the porch to keep it cold. We forgot to bring it in overnight, and when I went out the next morning I found that some of the beer had frozen.
What do you do when beer freezes? Is it still good to drink?
The truth is that after freezing beer may or may not be the same. It is up to a couple of variables:
What Changes in Beer When it Freezes?
If the beer freezes all the way through (mine did) it is likely to lose some carbonation and taste flat, but it still retains its beer characteristics as long as the seal is not broken on the cap. The alcohol is retained, though it may separate from the water, and the hop and malt flavors remain. If there were live yeast in the bottle they will not survive the freezing, as their cell walls will burst.
How is the Beer Affected After Freezing and Thawing?
The freeze-thaw cycle will actually accelerate the aging of the beer. Even if the carbonation is not lost you might see haze or flakes in the beer after it thaws (especially if it goes through multiple freeze-thaw cycles). These flakes are caused by the proteins in the beer ripping apart and settling out. They are mostly a cosmetic issue, but I have found it mentally difficult to drink beer that has floating flakes in it.
How to Defrost a Frozen Beer
There are several recommendations for how to defrost a frozen beer, but it seems the most effective method is to place the beer in a refrigerator to warm up slowly, rotating the bottle a half-turn every twelve hours or so. This helps to thaw the beer evenly and prevent the proteins from settling out, preserving your beer a little longer.
The Bottom Line on Frozen Beer
When all is said and done, the only way to tell if your beer has been ruined by freezing is to try it. Sometimes the carbonation and flavor are preserved, sometimes they are not. In my case I was pleasantly surprised to find that the beer actually tasted normal and had its normal carbonation after thawing back out.
What has your experience been with beer after it freezes?