Many consumers have questions about food expiration dates. Pictured: can with expiration date

Every day the average American throws out nearly a pound of food, according to a recent study from the Department of Agriculture. There are plenty of reasons why good, usable food gets tossed—picky kids, overstocked pantries, or even leftovers that sit in refrigerators too long.

But another major factor is the misconception about what all of those dates on food package labels—“sell by,” “use by,” and “best if used by”—really mean. Ninety percent of Americans misinterpret the dates on labels, according to a recent study from the Natural Resources Defense Council (NRDC) and throw out food that could still be consumed or frozen for later use.

That raises the question: If expiration dates aren’t a reliable gauge of food spoilage, how does a consumer know what to keep and what to toss?

What Date Labels Actually Mean

With the exception of baby formula, there are no federal regulations on date labeling. Often the “best if used by,” “sell by,” and “use by” designations are just manufacturers’ best guesses about how long their food will taste its freshest. Supermarkets may also use the dates as a guide when stocking shelves. But the dates have little to do with how safe the food is.

  • Best if Used By/Before. This guarantees when a product is of the best quality or flavor. For instance, a jar of salsa may not taste as fresh or crackers may be soft instead of crisp after this date. It's not about safety.
  • Sell By. This is the date set by manufacturers to tell retailers when to remove the product from shelves. The goal is to ensure that the consumer has the product at its best quality, which can be several days to several weeks, depending on the item. For instance, milk, assuming proper refrigeration, should last five to seven days past its sell-by date before turning sour.

  • Use By. This is the last date that guarantees the best quality of a product. This is also not a safety date except when used on infant formula.
More on Food Labels

According to a recent report from the NRDC and Harvard University, manufacturers typically use methods such as lab tests and taste-testing to set these label dates. But consumers have no way of knowing the background. In many cases, dates are conservative, so if you eat the food past that date, you may not notice any difference in quality, especially if the date has recently passed.

As a general rule of thumb, most canned foods (for example, canned tuna, soups, and vegetables) can be stored for two to five years, and high-acid foods (canned juices, tomatoes, pickles) can be stored for a year up to 18 months, according to the USDA. Watch out for dents and bulges in cans, though. That might be a sign it’s time to toss those products.

If you’re still not sure whether a product or item is worth saving past its date label, a free app the USDA created, FoodKeeper, will help you determine how soon specific items—everything from oats to coconut milk to maple syrup—should be consumed if it’s stored in the pantry or how long it will last in your refrigerator once it’s opened.

Staying Safe

While nonperishable items like grains and dried and canned goods can still be used well past their label dates, meat, dairy, and eggs are a different story. Although there are still no federally regulated expiration dates on those items, they obviously have shorter shelf lives. According to Sana Mujahid, Ph.D., manager of food-safety research at Consumer Reports, the best way to know whether a perishable food has spoiled is simply to “trust your taste buds and sense of smell.”

Foods past their prime often develop mold, bacteria, and yeast, causing them to give warning signs to your senses. Spoiled food will usually look different in texture and color, smell unpleasant, and taste bad before it becomes unsafe to eat.

Foodborne illness comes from contamination, not from the natural process of decay. That said, bacteria like listeria thrive in warmer temperatures, so it’s important to always keep your perishables refrigerated at the proper temperature. (The Food and Drug Administration says your fridge should be set no higher than 40° F.)

Also, a good rule of thumb is to throw out a perishable item after 2 hours at room temperature or half that time in high heat. Also keep all food preparation surfaces clean and avoid cross-contamination of raw meat and other grocery items.

“The most important thing that consumers should do is follow good food handling and storage practices, which can prevent unnecessary spoilage and ensure food safety,” says Mujahid.

How to Avoid Waste

  • Freeze it. “Freezing is an excellent way to halt the aging process and extend the life of foods that might otherwise go bad or get thrown away,” says Tyler Lark, Ph.D., a food-waste researcher at Gibbs Land Use and Environment Lab. Frozen foods won’t go bad because bacteria and other pathogens can’t grow in frozen temperatures. This even applies to milk, bread, cheese, and raw eggs (crack and lightly beat them first).

  • Save that fruit. According to the NRDC, fruit is one of the most common items to be tossed prematurely. Fruits like bruised apples, overripe bananas, or citrus like oranges and clementines that have dried up can be used in various recipes, for example, from the “Amazing Waste Cookbook” (PDF) created by the Nelson Institute for Environmental Studies at the University of Wisconsin-Madison.

  • Extend the life of produce. There are a variety of tricks for extending the shelf life of veggies, like wrapping broccoli in a damp paper towel, keeping celery in tinfoil instead of plastic, and sticking asparagus in a glass with a half-inch of water.

  • Organize your fridge. Studies have shown that out-of-sight foods are often forgotten, so keep the most perishable items up front on the highest shelves. And if you really want to get proactive, keep a list of the items closest to expiration. (Newer “smart fridges” can make this process even easier.)

  • Compost. Composting expired produce or packaged items like bread is a great way to recycle food without contributing to more waste.