6 Mistakes You’re Making When Reheating Leftovers That Could Make You Sick
I’ve always considered leftovers to be a convenience, but recently it feels more accurate to say that they’re a lifeline.
As we’ve grown accustomed to the lifestyle that comes with working from home, many of us have been forced (for better or worse) to forgo the $15 chopped salad station in the office cafeteria or that tri-weekly coffee shop panini habit. At first, I’d saunter into my kitchen around 2 p.m. and fumble around in the fridge, eventually tossing together some sorry mix of crudité and hummus, only to be left with a grumbling tummy within an hour.
It wasn’t long until I realized that if I made extra dinner the night before, I’d have an already-made meal ready to scarf when lunchtime rolls around. So yeah, I’m late to the lunch leftover game (to think how much money I could have saved!). But here’s the thing: there’s an art to reheating leftovers. And by art, I mean a way to do it that can kill the potentially harmful bacteria that resides in food that’s already been cooked and cooled. Here, the six major mistakes you’re making in the leftovers department, plus one myth we needed to debunk. Learn them, live them, love them. Because it’s just not a great time to get food poisoning, you know?
Letting food sit out at room temperature for longer than two hours.
Don’t allow any perishable foods, including cooked foods or leftovers, sit out at room temperature for more than two hours. And after cooking anything, make sure to keep your dish at 140°F or warmer until or while serving. According to the United States Department of Agriculture’s Food Safety and Inspection Service, the “danger zone” between 40°F and 140°F is where harmful bacteria that cause foodborne illness can grow.
“Throw away all perishable foods that have been left in room temperature for more than two hours (one hour if the temperature is over 90°F, such as at an outdoor picnic during summer),” says the USDA on its website. Additionally, remember to refrigerate leftovers as quickly as you can—and try to bring their temperature down as fast as possible so they don’t linger in the temperature danger zone. Shallow containers can help accomplish this, as can cutting larger foods into smaller pieces. For instance, you may want to divide large batches of soup or stew into smaller containers for quicker cooling. Same goes for whole roasts, turkeys, or hams—cut them into smaller parts before placing them in the fridge. To accelerate cooling, you can also try placing airtight containers in an ice or cold-water bath before you refrigerate.
Not storing them in airtight containers.
Choose high-quality, airtight food storage containers over wraps, takeout containers, and other flimsy or mismatched plastic pieces when possible. Also, be sure to match the quantity of your leftovers to the size of the container—this will eliminate extra airspace which helps keep bacteria out, preserves moisture, and avoids other odors from latching onto the food.
Storing leftovers in a fridge that’s too warm.
Check that your fridge is set at 40°F or below. And don’t just rely on the pre-programmed settings—rather, enlist help from a refrigerator thermometer. According to an Eatright.org survey, more than a third of people typically keep their refrigerator set at 40°F or higher, and 41 percent admit they don’t know the proper temperature to which their refrigerator should be set. Think of all the lost leftovers—and the bacterial growth—this could have caused.
Keeping leftovers longer than three to five days.
The USDA recommends using refrigerated leftovers within three to five days or freezing them for up to four months. Your nose knows best, so be sure to discard any foods with off odors, colors, or textural changes. To simplify things, always label leftovers to keep track of when they were made, and keep your fridge well organized so you can see what you have on hand. And when in doubt, throw it out.
Not reheating them to a high enough temperature to eliminate dangerous bacteria.
“When reheating leftovers, be sure they reach 165°F as measured with a food thermometer,” recommends the USDA. “Reheat sauces, soups, and gravies by bringing them to a rolling boil. Cover leftovers to reheat. This retains moisture and ensures that food will heat all the way through.” Remember: a food thermometer is the only reliable way to ensure you’ve reached a high enough temperature to eliminate harmful bacteria and to determine the doneness of cooked foods—this is particularly important when reheating foods that are often contaminated with bacteria that is likely to cause foodborne illness, such as chicken, eggs, and pork.
When using the microwave to reheat leftovers, even heating is key to ensuring that your food is safe to eat throughout. If your microwave doesn’t have a turntable, you should take extra measures to make sure leftover food is cooked through. Try this method: rotate your dish one-half turn midway through the heating time before stirring or tossing it to eliminate any cold spots where bacteria can thrive. Next, let your food stand for one minute before inserting a food thermometer to ensure food has reached the proper internal temperature of 165°F. The USDA also recommends covering your dish with a microwave-safe lid when reheating. "The moist heat that is created will help destroy harmful bacteria and will ensure uniform cooking."
Cross contaminating inside your microwave.
Many people still use their microwaves to defrost frozen meat (this is a whole separate issue). Remember that juices from raw meat often carry harmful bacteria, so if you’re someone who does use the microwave to thaw meat, seafood, or poultry, you’ll have to take precautions to avoid cross-contamination. For instance, you should use separate microwave plates—keeping one for defrosting meat and another for heating foods you’ll eat immediately after—or wash your plate in hot, soapy water between uses to kill bacteria.
Now that we’ve covered the mistakes you might be making when storing and reheating leftovers, we’d like to touch on one falsehood we’ve seen time and again on the internet regarding one food that we “shouldn’t” be eating leftover: potatoes.
Myth: Reheating cooked potatoes can produce botulism.
“Botulism, which is caused by a Clostridium botulinum (C. botulinum) bacterial infection causes a rare, yet serious, illness,” explains Tamika Sims, PhD, senior director of food technology communications at the International Food Information Council. “C. botulinum can be found on the surface of fruits, vegetables, and seafood, thus it’s extremely important to practice safe food handling during food preparation, especially when home canning, a practice that has gained interest recently. Safety practices include keeping seafood away from ready-to-eat foods and washing fruits and veggies before preparing them with cool running water.” (For the proper way to wash produce, see our guide here).
That being said, at warmer temperatures, potatoes are particularly prone to growing Clostridium botulinum, the bacteria that causes botulism. You can help prevent this by following Sims’ advice and properly washing potatoes, avoiding cross contamination, and stashing cooked spuds in the fridge as soon as you pull them from the oven or boiling water. For foil-wrapped potatoes, the CDC adds that “keeping potatoes that have been baked while wrapped in aluminum foil hot (at temperatures above 140°F) until they are served, or refrigerating them with the foil loosened,” is the safest storage method.
But final word: “Heating or reheating potatoes via a microwave or any other device cannot cause botulism,” Sims affirms.