Letter Re: Questions on Freezing Canned Foods

How cold can canned goods get? Near freezing, below freezing (say teens), way below freezing (negative numbers?)
I’m also interested to know this for canned butter and canned cheese.
Thanks! – Maxx

JWR Replies: Freezing generally will not harm the contents of most canned foods, but doing so will put the integrity of the can’s seal at risk. (And, once breached, it then opens up a whole raft of further potential problems, that range from mild (discoloration and oxidation) to severe (botulin poisoning).

Reactions to freezing depend on both the can’s construction and the contents of the can. If it is full, and the contents have high water content, then the can will likely split. Low water content items are less likely to split a can seam, but there is no real way to be sure. This is because even if the percentage of expansion for any given food product when frozen is known, there are additional variables such as air (or nitrogen) volume in the can–the space not filled by the food–and the amounts of excess moisture that can vary from batch to batch going through a cannery line. Sorry that there are no real “hard and fast rules”.

One thing is certain: Each transition between the unfrozen and frozen state adds additional stress to a can, so avoid multiple transitions through the freezing point!