One of the most common kitchen worries is letting food that needs to be refrigerated sit out. Everyone knows not to let raw meat or poultry sit out, but what about cheese? How long can cheese sit out?
To answer the question, it helps to understand what cheese is.
What is Cheese?
Cheese is made by combining milk (usually cow's milk, but sometimes the milk of sheep, goats or buffalo) with a starter culture of bacteria to sour the milk, plus an enzyme to form solid lumps called curds, leaving behind a protein-rich liquid called whey.
The whey is drained away and the curds are cooked, cut up and pressed together, squeezing out still more whey, and aged for several weeks, up to 12 months or even longer. Salt and other flavorings are added, and the resulting product is cheese.
Can Cheese Go Bad?
So can cheese go bad if you leave it out? People have been making cheese for at least 7,500 years. Mechanical refrigeration, on the other hand, has only been around for about 150 years. So refrigeration is clearly not a crucial factor in making or storing cheese.
Indeed, one of the most important stages of cheesemaking is the aging process, where newly shaped blocks of cheese are stored at temperatures ranging from 50 to 59 degrees F. Many cheeses spend weeks, months, even years in this unrefrigerated state. Far from diminishing quality, this aging process is essential to producing high-quality cheese.
But we should be clear on what we mean by "go bad." There's food spoilage, where bacterial changes cause a loss of quality; and then there's food poisoning, where dangerous bacteria reproduce in or on the surface of the food, which if you then eat it, can make you sick. So the question is, can that happen with cheese?
And the answer is, not likely. Virtually all cheese sold in the U.S. is made with milk that's been pasteurized, a process that eliminates potentially harmful bacteria from the milk. That means that cheese can't make you sick. Even if you leave it out for days, illness-causing bacteria aren't going to just spontaneously appear in your cheese.
So that leaves plain old spoilage. Like food poisoning, food spoilage is also caused by bacteria, only it's different bacteria. Food spoilage consists of changes in color, flavor, texture, aroma and so on, caused by those bacteria, that make that food unappetizing. The one thing these spoilage bacteria don't do is make you sick. They're not pathogens, they just turn your food into something you wouldn't care to eat.
The most common food preservation techniques, and the most ancient, involve depriving those bacteria of water, oxygen, or both. Without water or oxygen, the bacteria that cause food spoilage die.
And since making cheese involves squeezing out most of the water, cheese does not easily support the bacteria that cause food spoilage. The most common form of spoilage on cheese is mold, a type of fungus spread by spores, not bacteria, and it can grow even in the fridge. (The moldy parts can be cut off, leaving the unmoldy parts underneath perfectly good to eat.)
So, neither food poisoning nor food spoilage is much of an issue with cheese. The biggest issue with leaving cheese out at room temperature is loss of quality due to drying out and the separation of the fat from the cheese.
Hard Vs. Soft Cheese
In general, most of us are guilty of over-refrigerating our cheeses.
Cheese is made up of 20 to 40 percent fat, depending on the variety. When fat is chilled, its flavor, aroma, and texture change. For example, Brie straight from the refrigerator can be rubbery and flavorless, whereas served at room temperature it is soft, creamy, and luscious. Hard and semi-firm cheeses like cheddar and Swiss can be crumbly, bland and dry if they're too cold.
Now, if you're grating cheese into a casserole or making a grilled cheese sandwich, cold cheese is fine. But if you're preparing a cheese platter featuring expensive cheeses where the flavor, aroma and texture are crucial, it's important to let the cheese sit at room temperature for at least an hour before serving.
How Long Can Cheese Sit Out?
And as for how long you can leave it out, soft cheeses can stay out for 2 to 4 hours, while harder cheeses can stay out for up to 8 hours. Beyond that, the fat will start to leach out of the cheese, giving the surface a greasy appearance, and altering its texture. Again, this assumes an ordinary room temperature of around 70 degrees.
Some aficionados even claim that cheese shouldn't be refrigerated at all, which is not as outlandish as it sounds, assuming it's kept in a cool place, away from direct sunlight, and consumed within a day or two.
For one thing, apart from keeping things cold, refrigerators are incredibly efficient at extracting moisture from the air. Which means that if you store your cheese in the fridge, it's going to dry out, causing your cheese to lose quality more rapidly than if you kept it wrapped in parchment paper in a cool, dark cellar.
There are exceptions. Fresh, unripened cheeses like ricotta, cottage cheese and cream cheese need to be stored in the fridge.
Apart from that, though, aged cheeses can stay out for hours, and up to a day, assuming your house is cool. One way to look at it is that whatever you can't eat within a day should be kept in the fridge. This goes for soft, ripened cheeses like Brie, Camembert and other so-called "bloomy-rinded" cheeses, as well as semi-firm cheeses like Monterey Jack, cheddar and Swiss, and hard cheeses like Parmesan, Romano and pecorino. But since most people keep their homes warmer than 59 F, the fridge is the next best place.