Can beer freeze, and is it still good afterwards?

Beer of 5 percent by volume freezes at around 2 degrees below zero, beer of 10 percent by volume only at around 4 degrees below zero.

Pure water freezes at zero degrees. Dissolved substances lower that point: the more particles in the water, the lower the freezing point. For water the cryoscopic constant is 1.86 degrees Celsius per molality, and the drop is directly proportional to the amount of dissolved substance. Alcohol accounts for most of that drop, residual sugars and proteins for a small part.

Water expands by about 9 percent when freezing, and that expansion is the reason a full bottle or can can burst.

Ice is less dense than liquid water, which is why ice cubes float. In a closed bottle the ice has nowhere to go and the pressure rises until the crown cap pops off or the glass cracks. A can visibly bulges. Beer that freezes in the shed can foul a whole crate with glass.

Beer that has been frozen and thawed again remains drinkable as long as the packaging has stayed intact.

When thawing, the carbon dioxide does not come back into solution by itself, so the beer foams less and tastes flatter. Proteins and polyphenols can clump together, making the beer cloudy or showing flakes. If the bottle has cracked or the crown cap has lifted, throw the beer away: the contents were then no longer sealed.

When freezing, water first turns to ice, so that the remaining liquid gets a higher alcohol content.

The phenomenon is called freeze distillation. In its Handboek Accijns, the Customs describes that beer can gain a higher alcohol content this way and still remain beer, as long as it retains its beer character. The German eisbock is built on that idea. Do not try it in your freezer at home: the bottle bursts before the process yields anything.

Keep the storage place above zero degrees and do not place crates against an outside wall or directly on a concrete floor.

An unheated garage or shed drops along with the outdoor temperature during a frost period, and night is the most dangerous moment. Move crates indoors during sustained frost, to a hallway or a cellar. Also store beer in the dark, because temperature and light are the two factors that spoil the flavour fastest.