Leftovers can be kept for 3 to 4 days in the refrigerator. After that, the risk of food poisoning goes up. If you don't think you'll be able to eat leftovers within four days, freeze them right away. Frozen leftovers will stay safe for a long time. But they usually taste better if eaten within 3 to 4 months.
After 3 to 4 days, germs, also called bacteria, may begin to grow in refrigerated leftovers. This growth increases the risk of food poisoning, also called foodborne illness. Bacteria typically don't change the taste, smell or look of food. So you can't tell whether a food is dangerous to eat. If you're in doubt about a food's safety, it's best to throw it out.
What if the leftovers have been sitting out?
The best plan is to put leftovers in the refrigerator right after your meal. Food that is sitting out for a party or picnic should be chilled after two hours at typical room temperature. If it's above 90 degrees Fahrenheit (32 degrees Celsius) or more, food should not sit out for more than one hour.
The key for food safety is to keep hot food hot and cold food cold. Your goal is to lower the time that food is in the "danger zone." That means between 40 degrees Fahrenheit and 140 degrees Fahrenheit (4 degrees Celsius and 60 degrees Celsius). This is the temperature range when bacteria can multiply fast.
Keep hot foods above 140 degrees Fahrenheit (60 degrees Celsius) in a warming tray or slow cooker while sitting out. Cold perishable foods, such as chicken salad or cold meat sandwiches, can be put in serving dishes in bowls of ice.
How do I safely reheat leftovers?
Reheat leftovers until the internal temperature reaches 165 degrees Fahrenheit (74 degrees Celsius). Stir the food when reheating to make sure the food heats evenly. Slow cookers aren't suggested for reheating leftovers because the slow rate the temperature raises may promote bacterial growth.
Frozen leftovers should be thawed before cooking. Do not thaw leftovers by leaving them on the counter.
You can safely thaw frozen food three ways. You can microwave it, move it to the refrigerator to thaw overnight or put it in a leakproof container in cold water.