Why Does Freezed Food Have an Expiration Date?

Freezing significantly slows enzymatic activity, but it does not stop it entirely. Enzymes are specialized proteins made by living organisms to do jobs that are other than being a tissue of some kind. The walls of your freezer heat up periodically to melt off any ice that's building up on the walls of the freezer. If you've never heard of defrosting the freezer, well, thank the auto defrost function.