Refreezing thawed meat may be dangerous because harmful bacteria may grow on the meat while it is thawing. Refreezing the meat does not tend to kill this bacteria. In general, the risk of bacterial contamination is highest in meat that has been thawed outside the refrigerator for more than two hours.
The United States Department of Agriculture advises consumers not to refreeze meat and poultry that has been thawed outside of the refrigerator for more than two hours, or at a temperature above 90 degrees for more than one hour. This is due to the increased growth rate of bacteria at these higher temperatures.
Meat and poultry that has been thawed in the refrigerator at a temperature of less than 42 degrees is generally safe to refreeze, though the texture of the meat may be altered when it is thawed. The thawing process causes the meat to lose water. Additionally, refreezing meat causes ice crystals to form in the meat, disrupting the structural integrity of the tissue.
Freezing cooked meat and poultry is generally safe, though the length of time that the cooked meat remains viable depends on the preparation methods. Most cuts of refrigerated meat available at grocery stores have already been frozen during transport, therefore freezing them again may alter the texture.