raiding fridge Shutterstock/Christopher Boswell
Shutterstock/Christopher Boswell
  • Expiration dates are based on rough estimates.
  • Americans waste 40% of the food they purchase annually, the equivalent of $218 billion.
  • Instead of relying on imprecise sell-by dates, here’s the best way to tell if foods like eggs, cheese, fish, or veggies have gone bad, according to science.

The best way to tell if a food is still good to eat isn’t necessarily looking at the sell-by date printed on the package.

Expiration dates are based on rough estimates. They can tell you when a carton of eggs or a raw steak will likely reach the limit for their best quality, but that’s about it, according to research compiled by the Natural Resources Defense Council (NRDC), a nonprofit environmental organization.

“Millions of Americans are tossing perfectly good food in the trash because they think it’s not safe to eat after the date on the package,” Dana Gunters, a senior scientist with the National Resources Defense Council, said in a statement last year.

Americans throw away up to 40% of purchased food every year, the equivalent of $218 billion. In addition to the wasted money — about $1,500 per year for a family of four, according to the NRDC — food waste also means that all of the resources that were used to grow, store, and transport food get wasted, too.

Here’s how to tell if everything in your refrigerator — including milk, cheese, hummus, and fish — has gone bad.

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A bad egg floats.

A bad egg floats.
Narong Jongsirikul/Shutterstock

Egg shells are slightly porous, and as they age, small sacs of air begin to form between the shell wall and the egg.

If there’s enough of an air bubble inside an egg to cause it to float in a bowl of water, chances are it’s gone bad, according to the US Department of Agriculture.

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Expired yogurt begins to puddle more than usual.

Expired yogurt begins to puddle more than usual. Gene Kim

When kept in a sealed container, yogurt can last between one and three weeks. That’s thanks to its live bacterial cultures, which act as a natural preservative.

But when those cultures start to die off, things go awry. More liquid than usual will pool on the surface, and sometimes mold will form.

Other signs of expiration include curdling near the bottom, according to StillTasty.

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Uncooked beef gets slimy when it’s gone bad.

Uncooked beef gets slimy when it's gone bad. iStock

Uncooked beef with a foul odor, slimy texture, or sticky or tacky feel is best thrown out, according to the USDA.

Changes in color, on the other hand, aren’t necessarily an indication that raw meat has expired, the agency says.

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Expired hummus develops a sour taste.

Expired hummus develops a sour taste.