6 Common Errors When Reheating Leftovers

I used to be unfamiliar with the concept of enjoying leftovers for lunch. Not long ago, I would wander into my kitchen around 2 p.m., rummage through the fridge, and end up with a disappointing combination of raw veggies and hummus. An hour later, my stomach would start growling again.

Eventually, I discovered that preparing extra dinner the night before meant having a ready-made meal for the next day's lunch. However, reheating leftovers requires a specific approach to eliminate harmful bacteria that may linger in cooked food. Below are six common mistakes people make with leftovers, along with a debunked myth. Master these tips to avoid food poisoning and make the most of your meals.

Leaving food at room temperature for over two hours is a mistake.

Perishable items, such as cooked meals or leftovers, should not remain at room temperature for more than two hours. Serve dishes immediately after cooking while they are still at or above 140 F. The USDA's Food Safety and Inspection Service warns that the "danger zone" for bacterial growth, which can lead to foodborne illnesses, lies between 40 F and 140 F.

If food has been left out for more than two hours, discard it. In temperatures exceeding 90 F, such as during a summer picnic, dispose of it after just one hour, as advised by the USDA.

Cool and refrigerate leftovers promptly to ensure safety. Use shallow containers and break down larger items into smaller portions for faster cooling. For soups or stews, divide them into smaller containers. Large cuts of meat, like roasts or turkeys, should also be sliced into smaller pieces before refrigeration. To speed up cooling, place leftovers in airtight food storage containers and submerge them in an ice or cold-water bath before refrigerating. When transporting perishables, opt for insulated carriers to keep them at a safe temperature, such as these chic lunch bags.

Storing leftovers in non-airtight containers is a mistake.

Opt for high-quality, airtight food storage containers instead of wraps, takeout boxes, or flimsy plastic options. Match the container size to the amount of leftovers, filling it as much as possible to minimize air exposure. Consider investing in meal prep containers if you frequently pack leftovers for lunch. This approach prevents bacterial contamination, retains moisture, and protects food from absorbing unwanted odors.

Storing leftovers in a refrigerator that's not cold enough is a mistake.

Ensure your refrigerator is set to 40 F or lower, and verify this with a fridge thermometer. An Eatright.org survey revealed that over a third of people keep their fridge at 40 F or above, and 41 percent are unaware of the correct temperature setting. This oversight can lead to spoiled leftovers and increased bacterial growth.

Keeping leftovers beyond three to five days is a mistake.

According to the USDA, refrigerated leftovers should be consumed within three to five days or frozen for up to four months. Trust your senses—discard any food with unusual smells, colors, or textures. To stay organized, label leftovers with their preparation date and maintain a tidy fridge for easy visibility. When unsure, it's better to dispose of the food.

Failing to reheat leftovers to a sufficiently high temperature is a mistake.

The USDA advises, "Leftovers should reach an internal temperature of 165 F when reheated, as measured by a food thermometer. For sauces, soups, and gravies, bring them to a rolling boil. Covering leftovers during reheating helps retain moisture and ensures even heating." A food thermometer is essential to confirm the temperature is high enough to kill harmful bacteria, especially for high-risk foods like chicken, eggs, and pork.

When using a microwave to reheat leftovers, ensure the food is heated evenly. If your microwave lacks a turntable, rotate the dish halfway through and stir or toss the food to eliminate cold spots where bacteria can grow.

After reheating, let the food stand for one minute before checking its temperature with a food thermometer to ensure it has reached 165 F. The USDA also suggests covering the dish with a microwave-safe lid. "The steam generated helps destroy bacteria and promotes even cooking."

Cross-contamination in your microwave is a common oversight.

While many use microwaves to defrost frozen meat, this practice is a separate concern, and we generally advise against it.

Raw meat juices can harbor harmful bacteria, so if you must use the microwave to thaw meat, seafood, or poultry, take steps to prevent cross-contamination. For example, use dedicated plates for defrosting meat and another for reheating ready-to-eat foods, or thoroughly wash the plate with hot, soapy water between uses.

Having explored the most frequent errors in storing and reheating leftovers, let's debunk a persistent myth: the idea that potatoes are unsafe to eat as leftovers.

Don't fall for the myth that reheating cooked potatoes causes botulism.

Botulism, a rare but serious illness caused by Clostridium botulinum (C. botulinum), is not to be taken lightly. Tamika Sims, PhD, senior director of food technology communications at the International Food Information Council, explains, "C. botulinum can be present on fruits, vegetables, and seafood, making safe food handling crucial, especially during home canning. Avoid cross-contamination and wash produce thoroughly with cool running water." (Refer to our guide on proper produce washing).

While potatoes can foster Clostridium botulinum growth at warmer temperatures, Sims clarifies, "Reheating potatoes in a microwave or other device does not cause botulism."

When handling potatoes, follow Sims' advice: wash them properly, prevent cross-contamination, and refrigerate cooked potatoes promptly after cooking. For foil-wrapped potatoes, the CDC recommends keeping them hot (above 140 F) until serving or refrigerating them with the foil loosened.