Are cans of mushrooms and tomatoes that were inadvertently frozen safe?
These canned products are safe to eat, provided the can is not swollen or bulging, and provided the seams are still intact. Canned foods have at least 2 seams: one is the welded side seam vertically along the can body, which requires removing the paper label to see; the other seam goes around the entire top lid, where the top lid is attached to the can body. Some cans have a third seam, which is all the way around the bottom lid and can body, identical to the top lid seam. All two (or three) seams must be intact, without any bulging. The reason an occasional can might bulge after freezing is that the water volume expands 9 percent on freezing, and if the empty space at the top of the can is too small, the ice will bulge the can, possibly opening a seam slightly. If that happens, a spore of C. botulinum could enter the slightly opened seam, grow, and produce toxin. You should visually inspect every can before use, to make sure all seams are unaffected by the freezing. If you see a bulge
