In the event that the electricity goes off, the National Live Stock and Meat Board stresses the importance of keeping the freezer door closed.
Unopened freezers that are full, well-insulated and have been set sufficiently cold can keep items frozen for one or two days. When the power goes on, if meats are still partially frozen, they should be quickly refrozen. Meats that have completely defrosted but are still cold can be cooked, then frozen.
How can you determine if meat is no longer good to eat? Check for a general change in the quality. This includes loss of freshness and a color change from bright red in beef or pink in pork, veal or lamb to a dull gray color. An off-odor will develop, and if the meat has been kept in an unopened package, the surface may become slippery. If there is any question about the safety of the meat, it should be discarded.