So, You Accidentally Ate Moldy Cheese. Here’s the Best and Worst Case Scenario.

Photo credit: Maren Winter / EyeEm - Getty Images
Photo credit: Maren Winter / EyeEm - Getty Images

From Prevention

It’s easy for things to get lost in your fridge. So, when you come across cheese that’s been hanging out for a while, there’s a solid chance it could have grown mold.

That’s where the mental dilemma comes in: Do you really have to chuck the whole thing? Can you cut off the moldy part and eat the rest? And how bad is it to eat cheese with mold on it, anyway? Before you try to eat around the problem, there are a few things you should know about moldy cheese first.

What is mold, exactly?

Mold is a type of microscopic fungus that thrives in moist areas, according to the United States Department of Agriculture (USDA). It’s unclear exactly how many different types of mold there are, but there may be 300,000 or more.

Most molds are threadlike, multi-celled organisms that are transported by water, air, or insects, the USDA says. Many have a body that consist of root threads that invade the food it lives on, a stalk that rises above the food, and spores that form at the ends of the stalks.

Foods that are moldy can also have invisible, harmful bacteria like Listeria, Salmonella, and E. coli growing along with them, says Darin Detwiler, Ph.D., director of the Regulatory Affairs of Food and Food Industries program at Northeastern University and author of Food Safety: Past, Present, and Predictions.

Keep in mind that you can’t necessarily see all of the mold that’s infected your cheese (or any other food). “Think of mold as a weed,” says Susan Whittier, Ph.D., director of the clinical microbiology service at New York Presbyterian/Columbia University Medical Center. “Even though you pull it out, it still has roots and it’s just going to grow back.”

The type of food matters here, she says. Mold may be more likely to spread widely in soft foods, ruining even the parts that look OK, while it may be more localized in dense, hard foods, like a Parmesan cheese.

Why can mold be harmful?

Again, there is a wide range of molds out there. Some will do nothing, while others can make you really sick. Certain molds can cause allergic reactions and respiratory problems, the USDA says. And some molds, with the right conditions, can produce something called “mycotoxins,” that is, poisonous substances that can make you sick and even kill you.

How does cheese get moldy?

Some cheeses are meant to be moldy, and it’s OK to eat those molds, says Jane Ziegler, D.C.N., R.D., L.D.N., associate professor and director of the Department of Clinical and Preventive Nutrition Sciences at Rutgers University. “Blue veined cheese—Roquefort, blue, Gorgonzola, and Stilton—are formed by the introduction of Penicillium roqueforti spores,” she explains. “Brie and Camembert have white surface molds. Other cheeses may have an internal and a surface mold. These cheeses are safe to eat.”

But mold spores can also latch onto your cheese through the air or water, where they can grow. “When moisture exists on any food, ventilation allows for exposure to spores, which can collect and grow on the food’s surface,” Detwiler says. “Mostly these are invisible to the naked eye, but when one can see mold, strong roots have already grown.

What can happen if you eat moldy cheese?

There’s a wide range here and a lot depends on the type of mold and whether it’s harboring bacteria—things you really can’t tell simply by eyeballing it. Detwiler breaks down possible outcomes this way:

  • Best-case scenario: Nothing. It could taste bad or you might get an upset stomach.

  • In-between scenario: You could have a moderate allergic reaction, contract a foodborne illness, or have respiratory issues.

  • Worst-case scenario: You could be hospitalized, put on dialysis, or even die. This is more of a risk in people who are immunocompromised, Detwiler says.

“To be safe, it is better to toss the cheese, especially when there are children and individuals at high-risk in the household,” Ziegler says.

That’s especially true when you’re dealing with a soft cheese, shredded cheese, or sliced cheese. “Because soft cheeses have a high moisture content, they can be contaminated well beyond the surface of the moldy area,” Ziegler says.

If your cheese is hard or semi-soft, like cheddar, Parmesan, or Swiss, Detwiler says you might be OK to cut off the moldy part and eat the rest of the cheese. “Cut off at least one inch around and below the moldy spot,” he says. “Be sure to keep the knife out of the mold, so it doesn’t contaminate other parts of the cheese.”

The best way to store your cheese safely

The USDA specifically recommends cleaning the inside of your fridge every few months with either baking soda dissolved in water or a bleach solution to try to get rid of mold spores that could be lurking in there.

You’ll also want to keep your cheese covered in plastic wrap, and make sure you don’t leave it out of the fridge for more than two hours at a time, the USDA says. If you want to be really next-level about your cheese storage, you can try this tip from Detwiler: Wrap a hard or soft cheese in a new piece of parchment or waxed paper after each use to keep it fresh. “These breathable materials prevent mold-causing moisture from collecting on the surface without drying it out,” he says.

Bottom line: If you have moldy cheese and you’re not sure what kind it is or what to do, it’s really best to pitch it. If in doubt, throw it out.

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