In the winter months, basements and other food storage areas may get much colder than expected when a heat source fails, a door or window is accidentally left open or for some other reason. For best quality, canned foods should be stored at temperatures between 50 and 70 degrees F in a dark, dry place. However, if the canned foods do freeze accidentally, they can still be safe to use as long as the jars do not become unsealed.
So if you notice that your canned foods did freeze, check to be sure that the jars are still safely sealed. If they became unsealed, throw the food away — it could have gotten contaminated through the broken seal and might make people sick. If the seals are still good, they are still safe to use, although the final product may be softer than usual.
If you do store canned foods where you know they may freeze, wrap the jars in newspapers, place them in heavy cartons and cover them with more newspapers and blankets to help prevent freezing.
Go to MU Extension's Food Preservation program for more home food preservation tips.