Final answer:
Food should never be thawed at room temperature due to the risk of microbial growth. The USDA recommends thawing in the refrigerator, in cold water, or in a microwave, and advises against refreezing food that has been thawed.
Step-by-step explanation:
The way that food should NEVER be thawed is at room temperature. Thawing food at room temperature can allow for microbial growth as the food comes into the temperature danger zone (between 4°C and 60°C or 40°F and 140°F), which can lead to foodborne illnesses. The US Department of Agriculture (USDA) recommends safe thawing methods such as in the refrigerator, in cold water that is changed every 30 minutes, or in a microwave. Once thawed, the food should be treated like fresh perishables and cooked immediately if not kept cold.
The refrigerator should maintain a temperature at or below 4°C (40°F) to inhibit bacterial growth. Foods should never be refrozen once they have thawed, since this can lead to bacterial growth and potential foodborne illness. Cooked leftovers left at room temperature for more than two hours should not be eaten, even if reheated well, due to the risk of bacterial growth and toxins that may not be destroyed by reheating.