How Do I Know if My Leftovers Are Safe to Eat?

Some leftovers spoil more easily than others. Leftover are safe to eat if there are no foul odors, foam, slimy texture, rising air bubbles, unnatural colors, or mold.

Most of us have experienced this at some point: Your stomach is grumbling, and your mind jumps to the yummy leftovers you have from last night's dinner. You head into the kitchen, only to find them sitting out on the counter instead of the fridge. You realize you forgot to put them away, and they've been sitting at room temperature all night long.

There's nothing as disheartening as thinking you might have to give up those leftovers you were looking forward to. So how do you know whether leftovers are safe to eat, or if they need to be tossed? How long are leftovers good for? While some leftovers are fine at room temperature, others need prompt refrigeration to prevent spoilage. 

When you're deciding if something that's been left out on the counter or in the back of the fridge is safe to eat, the first thing you should consider is whether it's a high-risk or low-risk food. Some foods are much more likely to grow bacteria than others. 

Low-risk foods

Low-risk foods are those that aren't likely to cause food poisoning even if they're left out for several days. These are foods that are considered shelf-stable or those that have been preserved. 

Shelf-stable leftovers include:

• Bread
• Biscuits
• Cereal
• Crackers
• Cakes (except for cheesecake)
• Dry goods
• Smoked or salted fish 
• Pickled foods
• High-sugar foods such as jam and chocolate

High-risk foods

High-risk foods are those that pose a significant risk of contamination if they're not stored properly. The foods with the highest risk of food poisoning include: 

• Meat, especially raw or undercooked
• Raw fruits and vegetables that haven't been washed
• Raw milk and raw milk products
• Eggs, especially raw or undercooked
• Seafood and raw shellfish
• Raw or undercooked sprouts
• Raw flour

The first step in ensuring your leftovers are safe to eat is making sure they are cooked properly in the first place. Food should be prepared safely, cooked to a safe temperature, and refrigerated promptly after cooking. The following guidelines will help you determine if leftovers are safe to eat:

Don't leave leftovers out

Perishable foods should be refrigerated within two hours of being cooked. This includes the time the food spends sitting out on the table during the meal. The clock starts as soon as the food is finished cooking. If the ambient temperature in the room is 90 degrees or higher, you should refrigerate perishable food within one hour. 

Avoid the danger zone

Bacteria grows the fastest at temperatures between 40 and 140 degrees Fahrenheit. If you need to keep hot food out after cooking, use a warming dish to keep it at 140 degrees or warmer. For cold food, set bowls or trays in ice, or use cold serving trays that are replaced often to keep it below 40 degrees. 

Cool cooked food quickly

After you cook food or remove it from a warming dish, cool it as quickly as possible so you can safely refrigerate it. Portion out leftovers into smaller containers since they'll cool faster. It can take hours for a big pot of soup to cool enough to refrigerate. Leaving a big pot or pan of food to cool for hours will allow bacteria to grow and contaminate it. 

Properly store leftovers

When you're ready to refrigerate your leftovers, wrap them in airtight wrapping or put them in an airtight container. Not only does this keep them safe from bacterial contamination, but it also keeps them from absorbing odors from the refrigerator or drying out. 

Toss leftovers that have been left out too long

With food prices increasing, it hurts to throw away leftovers, particularly when they may not look or smell bad. However, if food has been sitting out for longer than two hours, or one hour if the room's temperature is over 90 degrees, you should discard it. 

Don't eat leftovers that have been refrigerated too long

Even if your leftovers have been properly refrigerated and kept out of the temperature danger zone, they can't be kept indefinitely. Refrigerated leftovers should be eaten within three to four days. Frozen leftovers are technically safe to eat indefinitely, but they start to lose flavor and freshness after three or four months. 

If you've stored your leftovers properly, you need to make sure you heat them safely before you eat them. Leftovers that have been frozen can be thawed in the refrigerator, in cold water, or in the microwave. If you're heating up leftovers in the microwave, heat them to 165 degrees. After they've been heated up, they can be refrigerated for three to four days or frozen again.  

When thawing leftovers in cold water, they should be in a waterproof package, so they aren't exposed to bacteria in the air and water. You should cook them thoroughly before refrigerating or freezing them. 

Even if you've properly stored your leftovers, you should immediately discard them if you notice any signs of spoilage. Spoiled food can cause food poisoning. Signs that your food may be spoiled include: 

• Canned foods that are bulging or improperly sealed
• Rising air bubbles
• Foul odor
• Foam
• Slimy texture
• Unnatural colors
• Mold

Frozen food is more likely to suffer from freezer burn than spoilage. Although it's safe to eat, frozen food with freezer burn probably won't taste very good. Signs of freezer burn include: 

• Grainy texture
• Dry texture
• Grayish-brown spots on the food's surface

You should carefully inspect frozen food for signs that it was thawed accidentally. If you suspect it was, discard it.