When to Toss Leftovers, According to Experts

There's often a random collection of storage containers and take-out boxes with leftovers in my fridge. I have a very organized friend who immediately puts the date on a label before she refrigerates any leftovers. I’m not that good.

Instead, my husband and I do the sight or sniff test. It is likely okay to eat if it doesn’t smell off or look funky. If we truly aren’t sure how old the leftovers are—or even what something is—we ditch it. It turns out, the experts agree that this is a good way to filter through leftovers.

Use Your Eyes and Nose

“The [food] spoilage process undergoes three stages,” says Keith Warriner, professor in the Department of Food Science at the University of Guelph in Ontario, Canada. “First you will smell off-odors, then see some degradation, for example wilting or meat discolation, then visible growth like slime on chicken, mold on cheese.” 

It can be easier to tell if fruit and vegetables go bad because you might see mold or browning. However, other foods like chicken or pasta don’t have visible signs of deterioration.

The sniff test works for some things, like meat, fish, and milk, Warriner says. “These have high protein and therefore produce ammonia and esters that have low thresholds. Other products in which odor is masked (marinated meats, cheese) are more difficult to detect.” 

However, it is important to note, Warriner says, that food that is contaminated with pathogens like salmonella can look and smell fine but can still make you sick.

Toss Your Leftovers Out After This Many Days

The cutoff for keeping most leftovers fresh and safe is about three to four days, according to the U.S. Department of Agriculture’s Food Safety and Inspection Service. Much longer than that and the risk of bacteria goes up. 

Experts like Warriner say, “The general consensus is five days. Once you put food in the fridge then microbes start growing and if there are pathogens that could reach dangerous levels.”

Bacteria—like E.coli, salmonella, and listeria—can lead to foodborne illnesses. Symptoms can range from a simple queasy stomach to more serious diarrhea, vomiting, and dehydration.

It’s important to note that not all germs are the same, says Jacob Tuell, MPH, Ph.D., a food safety and quality assurance manager, and director of the muscle foods division of the Institute of Food Technologists.

“Spoilage microorganisms that cause foods to deteriorate are not the same as pathogenic microorganisms which cause us to get sick,” he says. “Spoilage microorganisms will make food unpleasant over time but is not a safety risk.”

If foods are stored in what’s known as the “danger zone” (40°F to 140°F) for too long, that can trigger the growth of bacteria that can cause disease.

“I would be more concerned with knowing the history of my leftovers—were they cooled promptly after serving and kept cold?—than the duration of storage,” Tuell says. “Unfortunately, foods can harbor pathogens, but show no evident signs of spoilage.”

Best-by and Use-by Dates

If you have leftovers in a store-bought package, it’s not a bad idea to check the “best-by” or “use-by” dates.

“Best-by dates are an indication of when to consume a food for peak quality and are not related to food safety,” says Tuell. “So long as it has been handled properly, such as keeping it refrigerated if it requires refrigeration, most foods can be safely consumed well past their date.”

Warriner recommends paying attention to the dates on deli meats, pasteurized soups, soft cheeses, and vacuum-packed meats. In those cases, the date is based on food safety.