Michigan State University Extension
Preserving Food Safely - 01600509
If power is interrupted or the freezer fails to hold a proper temperature, do not open the cabinet unnecessarily. Food in a loaded cabinet usually will stay frozen for 2 or more days, even in summer. In a cabinet with less than half a load, food may not stay frozen more than a day. Cover the freezer with blankets to help hold in the cold. Pin the blanket away from the air vent. The air vent must be kept open since air is needed when the electricity comes back on.
If the power is not to be resumed within 1 or 2 days, or if the freezer may not be back to normal operation in that time, use dry ice to keep the temperature below freezing and to prevent deterioration or spoilage of frozen food. To locate dry ice, check with local food companies, chemists or druggists.
When dry ice is obtained quickly following interruption of power, 25 of dry ice in a fully loaded 10-cubic foot cabinet should hold the temperature below freezing for 3 to 4 days; less than half a load for 2 to 3 days. In the freezer, place dry ice on a board or heavy cardboard on top of food packages. Open freezer only when necessary. Don't handle dry ice with bare hands; it can cause burns. When using dry ice, the room should be ventilated. If you can't get dry ice, try to locate a locker plant and move food there in insulated boxes.
Occasionally, frozen foods are partially or completely thawed before the freezer is discovered not operating.
The important considerations in refreezing foods are the temperature at which thawed foods have been held and the length of time they were held after thawing.
You may safely refreeze frozen foods that have thawed if they still contain ice crystals or are still at refrigerator temperature after thawing (about 40 degrees Fahrenheit).
Partial thawing and refreezing reduces the quality of most foods. Foods that have been frozen and thawed require the same care as foods that have never been frozen. Use refrozen foods as soon as possible to save as much of their eating quality as you can.