Underthawing

Underthawing refers to the incomplete thawing of a frozen item, particularly food. This occurs when the temperature of the food does not reach a safe level throughout, leaving portions still frozen or at temperatures that allow for rapid bacterial growth. This can happen if a food item is too large to thaw properly in the allocated time, if the thawing method is insufficient, or if the food is removed from the thawing process prematurely.

The primary concern with underthawing is food safety. When food is not thawed completely, the internal parts may remain in the "danger zone" between 40°F (4°C) and 140°F (60°C), where bacteria multiply quickly. This can lead to an increased risk of foodborne illness. For cooking purposes, underthawed food may also not cook evenly, potentially resulting in undercooked areas even if the exterior appears done.

Safe thawing methods include refrigerating the food, immersing it in cold water (changing the water every 30 minutes), or using a microwave on the defrost setting, provided the food is cooked immediately after. Avoid thawing at room temperature, as this significantly increases the risk of underthawing and bacterial contamination. If food is underthawed, it is generally recommended to cook it thoroughly or to refreeze it if it has been thawed safely in the refrigerator and has not been at room temperature for an extended period.