If you keep a beer in the freezer for an extended period, it can lead to various outcomes depending on the temperature and duration of freezing:
Supercooling: Beer, like other liquids, can undergo supercooling if the temperature in the freezer is below its freezing point (around -2 to -3 degrees Celsius or 28 to 26 degrees Fahrenheit). In this state, the beer remains liquid even though it has reached a temperature below its freezing point. However, the moment the beer is disturbed or opened, it can rapidly turn into ice, causing the bottle or can to burst or explode.
Formation of Ice: If the freezer's temperature is below the freezing point of beer and the beer is left in there for a long time, it will eventually freeze and turn into ice. This can cause the beer to expand, potentially leading to a broken bottle or can, or it may affect the beer's taste and texture once thawed.
Changing Taste and Texture: Even if the beer doesn't freeze entirely, the cold temperatures in the freezer can affect its taste and texture. Freezing can cause the beer to lose some of its carbonation, leading to a flatter taste when consumed.
To avoid any mishaps, it's generally not recommended to keep beer in the freezer for prolonged periods, especially in glass bottles, as they can shatter due to expansion when frozen. If you need to quickly chill a beer, it's best to use a refrigerator or an ice bucket filled with ice and water for a short period. Always check the beer's temperature regularly to prevent it from freezing.