Medically Reviewed by Christine Mikstas, RD, LD on March 05, 2021
Fact: Refrigerate Leftovers Within 2 Hours
The bacteria that cause food poisoning grow quickly at room temperature. To make sure it’s safe, put food in the fridge or freezer in the 2 hours after it’s cooked or taken off a heat source, such as a warming tray. If it’s hot outside (above 90 F), do this within 1 hour. One in 3 people admit to eating pizza left out overnight. If those slices have been sitting out for hours, throw them away.
Myth: Cool Hot Foods Before Refrigerating
You don’t need to wait until leftovers are room temperature. You can put hot foods directly into the fridge. Large amounts, such as a pot of soup or a whole chicken, can take too long to cool. If you’d like to chill them quickly, you can divide them into smaller, shallow portions or put them in a leak-proof container in a large bowl of ice and a little water.
Fact: Set Your Fridge to 40 F or Below
More than a third of Americans have too-warm refrigerators. This can lead to bacteria growth. Check that your fridge is set to 40 degrees or below; the freezer should be 0 F or below. If the control doesn’t show the exact temperature, you may need an appliance thermometer. And it’s best to leave room between items. This helps the cold air circulate and cool down food.
Myth: Leftovers Are Safe Until They Smell
You can’t see, smell, or taste the bacteria that can make you sick. To protect against food poisoning, toss out food after 3 to 4 days in the fridge or move it to the freezer. While frozen leftovers are safe for a long time, they lose flavor and texture after 3 to 4 months. Always use airtight packaging or containers, and write down the date.
Myth: It’s OK to Eat Cold Leftovers
To kill dangerous bacteria, you need to heat food to 165 F. The best way to tell if it has reached that temperature is with a food thermometer. Put it in different places, especially the thickest or deepest part, because dishes can cook unevenly.
Fact: Don’t Use Hot Water to Thaw Frozen Foods
Putting frozen foods in hot water or leaving them on the counter to thaw can make bacteria grow faster. There are three safe ways to thaw food: in the refrigerator, in cold water, and in the microwave. It's also safe to cook foods straight from frozen.
Myth: Freezing Food Destroys Bacteria
While freezing can slow the growth of bacteria, it doesn’t kill them. When you thaw leftovers, the bacteria may start growing again and make you sick. That’s why it’s important to reheat thawed leftovers the right way.
Myth: It’s OK to Reheat Leftovers in a Slow Cooker
Slow cookers and chafing dishes can take a while to warm up. That means your leftovers may stay between 40 and 140 F for too long. Instead, microwave them, bake them at 325 F or higher, or bring sauces, soups, and gravies to a rolling boil. No matter what method you choose, always check the temperature with a thermometer before serving.
Fact: You Can Freeze Leftovers More Than Once
Didn’t finish all those leftovers? Don’t toss them out. Put them back in the freezer and save them for another meal. Just make sure that you heated them to 165 F first. If a large container of leftovers was frozen and only a portion of it is needed, it is safe to thaw the leftovers in the refrigerator, remove the needed portion and refreeze the remainder of the thawed leftovers without reheating it.
Myth: Microwaves Kill All the Bacteria
Microwaves cook food from the outside in. This leaves cold spots where bacteria can grow. One study found that simply zapping a dish for 5 minutes didn’t kill salmonella. To microwave safely, cover leftovers with a lid or vented plastic wrap. Halfway through cooking, stir, rotate, or turn the food upside down. Let stand for a few minutes, and put a thermometer in different places to check the temperature.
Myth: Eat Leftovers Right Away After Reheating
If you’ve microwaved leftovers, you’ll need to wait a few minutes before digging in. Microwaves work by making food molecules vibrate quickly. Even afterward, they continue to create heat and cook that dish, so the temperature can rise by several degrees. To make sure your leftovers are safe to eat, let them stand for 3 minutes.
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Academy of Nutrition and Dietetics: “Tips for Reheating Leftovers.”
Epidemiology and Infection: “Salmonella Outbreak from Microwaved Food.”
Foodsafety.gov: “Handle Leftovers with Care.”
Food Research International: “The Effect of Freezing on the Survival of Escheria Coli 0157:H7 on Beef Trimmings.”
Food Science: “Fate of Listeria Monocyogenes During Freezing and Frozen Storage.”
Harvard Health Publishing: “Microwave Cooking and Nutrition.”
Journal of Food Protection: “Effects of Freezing and Storage on Microorganisms in Frozen Foods: A Review.”
Journal of Food Science: “Influence of Cooking Methods on Antioxidant Activity of Vegetables.”
University of Tennessee Agricultural Extension Service: “Your Microwave Oven: A Real Time Saver.”
U.S. Department of Agriculture: “Leftovers and Food Safety,” “Microwave Ovens and Food Safety,” “Safe Handling of Take-Out Foods,” “The Big Thaw — Safe Defrosting Methods for Consumers.”
FDA: “Refrigerator Thermometers: Cold Facts About Food Safety,” “Are You Storing Food Safely?”
Washington State Department of Health: “Food Safety Myths.”