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How Long Can Shredded Cheese Be Left Out?

We all want it to last forever. But, for the most part, it doesn’t.

You accidentally left a bag of shredded cheddar or mozzarella cheese, opened or unopened, on the counter overnight. Now it’s the next day, and you are wondering if it’s still okay to eat.

The package says “keep refrigerated,” which you already know, so that’s not really helpful. After all, the Food Safety and Inspection Service at the USDA recommends keeping perishable foods at room temperature for no more than 1-2 hours so that bacteria doesn’t grow to unsafe levels.

At the same time, you know that cheese was invented some three thousand years ago—long before refrigeration—and that farmers made cheese to preserve milk and stored it in their root cellars for months, sometimes years.

What’s the verdict, then?

Will a package of shredded cheese that’s sat out overnight become inedible or not? I scoured the Internet to find out what experts thought on the topic.

Dry, hard, less acidic shredded cheeses, such as cheddar, dried mozzarella, and parmesan, can be left out longer than their unripened and moist counterparts (brie, cottage, fresh mozzarella, ricotta, queso blanco, and others).

At least that’s the word from Undeniably Dairy, a dairy information resource funded by the National Dairy Council, the Innovation Center for U.S. Dairy and Dairy Management Inc.

Speaking of advice straight from the horse’s mouth! Still, that doesn’t necessarily answer the question at hand. So I set out to find even better advice on the matter elsewhere.

Adam Brock, Director of Food Safety, Quality, and Regulatory Compliance at non-profit organization Dairy Farmers of Wisconsin, tells Bon Appétit that harder cheeses can sit out for 4 to 8 hours, perhaps even longer, without spoiling.

According to a slide deck by the Wisconsin Center for Dairy Research, the following cheeses are exempt from refrigeration requirements during aging, storing, shipping, and display provided they have been stored at a temperature no higher than 86°F (30°C):

  • Aged Cheddar;
  • Colby;
  • Monterey Jack;
  • Parmesan;
  • Processed Cheese;
  • Swiss/Emmentaler Cheese.

Your Definition of “Overnight” Matters

So here comes the dreaded “it depends” answer that you all hate. “Overnight” is a broad term…

It’s one thing to leave a package of shredded cheese out after making yourself a drunken burrito at 3:00 am, then forgetting to put it back in the fridge (and fixing that mistake the next morning).

It’s another to leave the cheese out on the counter on a late Saturday afternoon, only to find that it was still there around noon on Sunday on a hot summer’s day (in such a case, I wouldn’t risk it).

With all this knowledge—and the rest of the things you need to know, which I will tell you about in a moment—you will have to decide for yourself whether or not to throw the shredded cheese away.

What Happens When Shredded Cheese Sits Out

It should be noted that storing cheese at room temperature comes at the expense of its best quality and safety for consumption:

Initially, the cheese begins to sweat as the butterfat separates from the solids. After a few hours, the cheese dries out and, in some cases, becomes crusty and crumbly. Eventually, pathogenic bacteria (the kind that can make you sick) replicate so much in and on it, they make it inedible.

Sweaty cheese is generally salvageable.

Sure, it won’t be as appealing and flavorsome as when you brought it back from the grocery store, but it is still cheese. Simply soak up that sweat with the help of a kitchen towel.

What if it sat it out for so long, it turned dry and crusty?

Before you go on and do anything else, decide if the cheese is still safe to eat. You are in murky waters, and you will have to rely on common sense. You never want to eat anything that’s moldy, that smells funny, or that, after a quick taste test, doesn’t taste good.

If you feel repelled, your body is telling you not to cross the line. Err on the side of caution and throw that thing in the bin.

According to the U.S. Centers for Disease Control and Prevention, 48 million Americans contract food poisoning every year. 128,000 of them are hospitalized, and 3,000 of them die.

Cooking is as much a gesture of love as it is a call for responsibility, so don’t put yourself your family at risk; it is simply not worth it at the end of the day.

If—and only if–you deem the cheese still edible, you could always use it to prepare a melty-cheese snack like grilled cheese sandwiches or stir it in with whole milk in a pot to make a nacho cheese sauce.

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Jim is the former editor of Home Cook World. He is a career food writer who's been cooking and baking at home ever since he could see over the counter and put a chair by the stove.