Reheating to 165 °F

The target

CDC says to reheat leftovers to 165 °F or hotter before serving. When reheating in a microwave, it recommends a food thermometer to make sure the food reaches 165 °F. Nebraska Extension gives the same target, or until hot and steamy, and says to bring soups, sauces and gravies to a rolling boil.¹²³

Microwave and oven

Use a container labeled microwave safe, and cover and rotate the food so it heats evenly. When reheating meat and poultry in the oven, Nebraska Extension says the oven should be set no lower than 325 °F.³

CDC adds that letting food sit for a few minutes after microwaving allows cold spots to absorb heat from hotter areas and cook more completely.²

University of Illinois Extension says to use microwave-safe containers, and lists what not to use: plastic storage bags, brown paper bags, plastic grocery bags, newspapers, aluminum foil and plastic containers. It also says to reheat all food to 165 °F as measured with a food thermometer.⁴

Frozen leftovers can go straight into a saucepan, oven or microwave without thawing. Reheating takes longer that way, but it is safe.³

Frozen cooked foods

The National Center for Home Food Preservation says most cooked or prepared foods do not have to be thawed before heating, and that casseroles, soups, stews and leftovers should be heated to at least 165 °F in the center before serving. The oven helps preserve texture, but a cold glass container should not go into a preheated oven unless its manufacturer says it is freezer to oven safe.⁵

Why not the slow cooker

Nebraska Extension does not recommend reheating in a slow cooker, because food may sit too long in the danger zone between 40 °F and 140 °F. Illinois Extension suggests reheating on the stovetop or in the microwave instead, then moving the food to a slow cooker only to keep it warm at 140 °F or above.³⁴

Deli meat and hot dogs

For people at higher risk of Listeria infection, such as people who are pregnant or 65 and older, CDC lists deli meat, cold cuts, hot dogs and fermented or dry sausages reheated to 165 °F or until steaming hot as the safer choice.⁶

Cooking ahead

CDC guidance on Clostridium perfringens says that food cooked ahead of time should be kept at 140 °F or hotter, or refrigerated at 40 °F or colder, and reheated to 165 °F or hotter before serving. Germs can multiply rapidly in food left between 40 °F and 140 °F, and foods cooked in large batches and held at unsafe temperatures have been linked to outbreaks.¹