Why is it recommended not to reheat mushrooms. Are there any differences between fresh and canned mushrooms?

Germany

Mushrooms are perishable foods. Their proteins can be easily destroyed by enzymes and microorganisms. So if mushrooms are not cleaned properly, but only steamed, and then stored improperly (e.g. at room temperature), they soon go bad. In former times the general recommendation was not to reheat mushrooms again, because of the risk of deterioration. We recommend only to use fresh mushrooms and also to thoroughly clean even those which look clean. If they are stored in a fridge and for not more 24 hours, it is in general no problem to reheat mushrooms again at recommended temperatures of 70 OC.
Industrial processed mushrooms - whether dried, frozen, canned or sterilised - can also be reheated without risk.