Most food safety experts advise that leftovers should be eaten or frozen within about three days after their original cooking, but a lot depends on the type of food and how it’s been stored. Meals that have been left at room temperature for more than a few hours are more at risk for contamination than those that have been promptly refrigerated, for instance, and dishes that contain meat are usually more prone to bacterial growth than those that contain predominantly vegetables or raw fruits. In most cases, the best advice is just to use common sense. People who are wondering if food is still edible should look at it, think about how long it’s been stored, and smell and taste it. If anything seems “off,” the food should be discarded.
In General
Opinions on how long properly stored dishes will be edible vary from source to source. The “official” recommendations from most government health authorities and professional food safety teams is four days maximum, but other people say that up to a week is fine so long as the food still looks and smells fresh. Frozen foods typically last longer, but should still be eaten within a month or two of freezing.
There isn’t really a hard and fast timing rule, since things spoil at different rates. Meats tend to attract more serious food-contaminating bacteria such as salmonella or E. coli and can go bad pretty quickly, but a fresh fruit salad may be fine in the fridge for much longer. Understanding where experts are coming from and using common sense are usually the best ways to ensure that meals made from leftovers are both safe and delicious.
Proper Storage
One of the keys to preserving the life of extra food is learning how to store it safely. There are a number of different theories, but one of the most predominant teaches that leftover food should be allowed to reach room temperature and them then promptly frozen or refrigerated in an airtight container. Hot items that are chilled too rapidly may produce condensation, which can speed the growth of harmful bacteria since most toxins thrive in moist environments.
Cooks have to be careful not to wait too long letting things cool, though. Most safety experts agree that meals should be stored no later than two hours after they were cooked, which is different than two hours after a meal concluded or two hours after leaving a restaurant. Separating a large meal into smaller portions in shallow containers can help it cool faster.
Food will usually last the longest and resist bacterial growth the best in an airtight container. Transferring things to a glass or metal packages with sealing lids is usually best, though durable plastic bags that seal across the top are also good options. People who store leftover food a lot might want to invest in a professional food sealer system, though these are often very expensive and can take up a lot of counter space.
Thinking About Temperature
The internal temperature of the refrigerator or freezer can also have an impact on how long things will stay fresh, with colder temperatures usually translating to longer life spans. People who store a lot of pre-cooked meals are usually better off setting their fridges to one of the coldest possible settings to give things the best shot of staying fresh. When it comes to freezers, colder temperatures are often the difference between that food that develops ice crystals and “freezer burn” and meals that stay relatively fresh for months on end. Lightly frozen foods are more susceptible to temperature fluctuations when the door is opened or new things are added in.
Foods that are freezer burned aren’t necessarily bad or dangerous, but they don’t usually taste very good. People who freeze a lot of leftover foods might be wise to look into a stand-alone deep freezer if they can’t make what they have get colder; packing meals in several layers of plastic or other airtight material can also make a difference. Marking the date of freezing with tape or a wax pencil can help cooks remember how long things have been stored, and keeping a list of what’s inside might also be helpful for people who are worried about forgetting what they’ve stored and when.
Reheating Guidelines
Even dishes that have been properly stored should usually be thoroughly reheated before they’re eaten in order to kill off any bacteria that might have started growing. A lot of this depends on the sort of food at issue, of course; a leftover green salad doesn’t need to be warmed, but a steak or hamburger would. Food doesn’t necessarily need to be re-cooked, but experts usually recommend bringing it back to its original cooking temperature before serving it. Things that have been frozen should usually be allowed to thaw in the refrigerator before reheating.
High-Risk Foods
When people don't know the history of leftovers, it may be best to discard them immediately. Foods brought to a family picnic or other outdoor event may have already exceeded their two-hour safety margin by the time the party ends. Foods prepared with egg, including mayonnaise, are often of particular concern, since these can spoil in just an hour or so, particularly when it’s hot. Fish and rare meats should also usually be eaten or stored very soon after cooking to prevent contamination.
What to Look Out For
The human digestive system can handle a certain amount of food contamination without major complications, which means that eating leftovers that have begun to spoil doesn’t always lead to food poisoning or other digestive troubles. Still, most medical professionals warn that it’s best not to take chances. Food should be discarded at the first sign of spoilage or discoloration, and anything that smells or looks even remotely unappetizing should not be eaten.
Many people set their own rules when it comes to how long they feel comfortable storing food. After three days, for example, someone may want to pitch every carry-out box or foil-wrapped mystery meat in the refrigerator. People may also want to consider ordering smaller portions when dining out and avoid stocking up on uneaten food at a picnic or wedding reception. It's often best to pack up only what can be readily frozen or consumed within a few days.
