What do expiration dates really mean? Are they exact dates indicating the moment your food will be unsafe to eat? Are they suggestions? Are the regulated by the FDA?

The answer is more complicated than you might think. Expiration dates are not actually tied to food safety at all, though that is how we think of them. Instead, they’re chosen by the manufacturer to indicate the date at which optimal flavor has passed. But that doesn’t mean your food is unsafe to eat. Unfortunately, because of our misunderstanding of the dates, we throw out far too much food from our refrigerators than necessary! Let’s look at a few examples for better understanding.

EGGS

This is a big one, in part because it’s difficult to tell from the outside whether an egg has gone bad! In truth, eggs last a long time. In fact, they might already be weeks old by the time you buy them at the grocery store. It all depends on how they’re shipped and stored before they reach your local market.

Fortunately, eggs can easily be consumed 3-5 weeks after you’ve brought them home. And how do you tell the age of an egg? Inside each egg is an air cell, this pocket actually serves as a little oxygen tank for potential baby chicks. The air cell is created in a gap between the shell and the inner membrane. As the egg ages, that air pocket continues to grow because egg shells have millions of microscopic pores that allow for gas transfer. So, if you put an egg in a bowl of water, an older egg will float, while a new egg will sink because there isn’t enough air to keep it buoyant. 

But is a floating egg safe to eat? Actually, it probably is. Salmonella has nothing to do with the age of an egg, it could be there in an egg from day one and is more related to chicken cleanliness than anything else.

DAIRY

According to Ethel Tiersky, the editor of ShelfLifeAdvice.com, “nearly two-thirds of Americans needlessly discard a quarter-gallon of milk each month.” We’ve all done it before, look at the date on the carton and toss whatever is remaining, even if one day before it tasted fine. And it’s an honest mistake, food safety is a huge issue. But remember, these dates are not tied to food safety, they're tied to food taste. And the dates can vary from state to state, since there is no governmental regulation. In Connecticut, milk must bear a “Sell By” stamp not more than 12 days from the day of pasteurization, in Pennsylvania that timeline is 14 days. 

What’s the best way to tell if your milk has gone bad? Smell it! Trust your nose, it knows more than you think. When milk smells off, it is time to throw it away. But remember, that bad smell could come before the “Sell by” date, depending on how well you store the milk to begin with.

Yogurt is another product to appraise by smell. Open yogurt will spoil more quickly than a sealed package because of the interaction with oxygen. But if you splurged on a bunch of yogurt cups because they were on sale, and still have 4 or 5 left when the expiration date arrives, don’t worry. Sealed yogurt will usually last one or two weeks past the “sell by “ date. Again, when you open the container, take a whiff first. If it smells like yogurt, then it’s still yogurt. If you see mold, time to chuck it.

Speaking of mold, what to do with cheese when it goes bad? Get yourself a good knife and cut off the offending moldy bits! Cheese is aged, it’s already quite old by the time you get it. Don’t worry so much about the expiration date, again, just smell it!

PASTA, CEREAL, RICE

Dried pasta has a one to two year shelf life based on the packaged dates, but it can last even longer than that! It doesn’t contain any water, which is the main ingredient in spoilage (water allows microbial growth), so as long as you store it in a cool, dry location, it’s good for years after the expiration date. The same goes for rice, so if you bought a giant bag when it was on sale, don’t fret when the date comes and goes. Those expiration dates are based on when the manufacturer thinks the product will no longer taste its best. But that doesn’t mean it’s unsafe to eat.

Cereal is another long-lifer. Boxes of your favorite cereals can last months after the sell by date. They may get a little stale (particularly if they’re opened), but that isn’t a signal of pathogens. Staleness is just a sign of moisture migration.

Expiration dates are actually quite new, they only arrived in the early 1970s. Prior to that, we were eating much more fresh food than packaged goods, and so we used common sense to tell when something had withered or spoiled. The National Institutes of Health has reported that in 2009 American food waste had increased 50% since 1974 and now totals about 1400 calories per day per person. 

Of course, the most infuriating part of expiration dates is the wording: Sell By, Use By, Best Before, and Expiration Date all mean different things, but none are based on food safety. 

Sell By: this tells the supermarket how long to display a product before throwing it out (this generates food waste, not all markets can donate the product to food banks).

Use by or Best Before: This tells you when to use the product by for the best flavor quality.

Expiration date: This typically is a suggestion for the last day you can consume food, but since there’s no scientific way to tell the exact moment a piece of food will spoil, it’s just a guess. Spoilage has more to do with the temperature and humidity of your storage (fridge, counter) than anything else.