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Read this before you purge your fridge

How do you tell when food is rotten? What do the dates on the package mean? Here are the answers.

Alina Bradford/CNET

There's a lot of confusion over when you should toss the food in your fridge. The United States Department of Agriculture (USDA) says that this confusion is a large contributor to food waste in the United States

Unfortunately for many, the date stamped on the package may make things even more confusing. Here's what sell-by, use-by and best-by dates mean, and how you can really tell when your food's gone bad. 

Sell-by date

The sell-by date may seem pretty self-explanatory. The food goes bad on this date, it's rotten and you shouldn't buy it, right? 

Actually, the food inside the package is still fresh. This date just helps stores manage their inventories, according to the USDA.

In fact, according to the Institute of Food Technologists, only two-thirds of a product's total shelf-life has been used when the sell-by date expires. This means the food will remain fresh for days to come.

Many stores put items that are on or past their sell-by date on discount. As long as you use the item in the next few days, you can get a great deal on perfectly safe food. 

You can also freeze foods with an expired sell-by date if you're not going to use them right away. So, look for these deals and stock up.

Use-by date

The use-by date is more important for consumers. It actually gives you an idea of when the food may go bad, though it's not always an indicator of when the food will make you sick. 

Typically, if a product is past its use-by date, its texture, color and quality could change, but may not be technically rotten. If it's a day or two past the use-by date, you should be OK. Any longer than that and you should probably toss it.

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The only exception to this rule is baby formula. The USDA notes that any formula past the use-by date should be thrown away.

Best-by date

The best-by date has nothing to do with safety. It's just on the package to let you know how long the food item will taste and look its best. After the date has passed, the food may taste stale.

So how do you know when food is bad?

OK, so the label dates don't really help that much to determine the moment food goes bad. So how do you avoid throwing away perfectly good food? 

There are a few ways to tell if food is too old to eat, according to the USDA. Basically, trust your senses.

If it smells rotten or has mold growing on it, toss it out. When meat products get slimy or sticky, that's a good sign they're rotten, too. 

Many people think that meat or poultry items are bad if they changes color. That's a myth. Color change is normal, though if the meat is sticky, slimy, moldy or stinky as well, toss it.

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