Each year some 5,000 Americans die from food-borne illnesses, according to the National Institutes of Health. Given the harm these diseases cause, it's important to handle and cook your food properly to minimize your risk of contracting a food-borne illness. One possible safety concern is refrozen meat. There are some circumstances where you can indeed refreeze meat and others where you should refrain from doing so.
According to the U.S. Department of Agriculture, you can refreeze meat if it's been thawed in the refrigerator, although the quality may deteriorate somewhat. You can also freeze foods that have been properly cooked. You should never, however, refreeze meats left outside the refrigerator or at temperatures of 40 degrees Fahrenheit for more than two hours. If the temperature is 90 degrees or above, you should not refreeze any meat left outside the refrigerator for more than one hour.
The reason why it's unsafe to refreeze meat left at room temperature has to do with the bacteria that cause food-borne illness. Meat can become contaminated with harmful bacteria during slaughter and processing, and these bacteria are already present in the meat when you buy it. Refrigeration inhibits bacterial growth but does not kill the bacteria. Freezing causes the bacteria to become dormant but will not kill them either. The bacteria in a piece of frozen meat have stopped growing but once the meat is at room temperature they will re-awaken and resume their growth.
By keeping the meat at room temperature for several hours then refreezing it, you give the bacteria another chance to grow and produce more progeny. The meat will now contain far more of the bacteria than it did originally, and when you thaw it again, the rate of bacterial growth will be greater, increasing the chances it will cause illness. Since freezing does not actually kill the bacteria that cause these diseases, cooking to a sufficiently high temperature is the only foolproof way to do so.
Refreezing After a Power Outage
In the event of a power outage, it's a good idea to situate the meat in your freezer so it won't drip on the other contents (assuming the freezer thaws out completely). Keep the freezer closed and once it's repaired recheck the condition of your meat. If the meat still has ice crystals or remains partly frozen, you can refreeze it. Just as with meat left at room temperature, however, you should never refreeze the meat if it's been at 40 degrees or above for two hours or more.