What Does It Actually Mean When Cheese Is Aged?

When we say that something has "aged like milk," such as an incorrect March Madness bracket or the film "Get Him to the Greek," it's not a compliment. It means that, like your two-week-old jug of 2% milk in the fridge, something has gone sour over time (as opposed to something that's "aged like wine"). But cheese is essentially just aged milk, and for most cheeses, aging is a vital part of the process. Heck, some moldy rinds are not only safe to eat but delicious. Still, as anyone who's read "Diary of a Wimpy Kid" and feared the Cheese Touch will tell you, that doesn't mean you can eat a moldy wedge of Swiss any old time you like. So it's worth asking: What does it mean to age cheese, and how is it different from just growing old or, indeed, growing mold?

Simply put, aging cheese is a matter of controlling which microbes grow on it — and just as importantly, which microbes don't grow on it. The microbes that feed upon your old milk or forgotten cheese are harmful bacteria that will give you a serious case of food poisoning or worse. But not all bacteria is bad: Some bacteria will turn milk into cheese, while other bacteria will intensify the flavor of that cheese over time. The job of the cheesemaker, then, is to control the conditions so that they reach the desired outcome.

The aging process looks different depending on what kind of cheese you're after. Some kinds of cheese, like mozzarella or ricotta, don't get aged at all: These are ideally consumed fresh, or as fresh as possible. But most other kinds of cheese can be aged for varying lengths of time in all sorts of conditions. Most common is the use of a "cheese cave," which doesn't have to be a literal cave (as awesome as that might be). This is just anywhere large, cool, and dark enough to maintain the right conditions for bacteria growth.

Some kinds of cheese, like Gruyère or Limburger, are "washed rind" cheeses, which mean they're regularly bathed throughout the aging process with a saline solution that encourages the growth of a certain kind of mold that makes these cheeses, like Scotland's Minger, often smell so bad. Other kinds of cheese are blue cheeses, like Stilton or Roquefort, which require a direct injection of the mold into their flesh. As for old reliable cheddar, it's wrapped up in an airtight bag and left to age for up to a year, which makes the flavor go from mild and creamy to sharp and tangy — just one illustration of the power of aging cheese, which in one case, is enough to sell for $209 a pound.