Good mold, bad mold

Thirty feet below the streets of Brooklyn, certain old brewery tunnels are now growing mold — thick, stinky, hairy, mottled mold — around and inside wheels of cheese.

These living carpets don’t deter Benton Brown, co-owner of the tunnels and the cheese within. “In France, we cut off these crazy rinds and it was the first thing we ate,” he says gleefully.

There’s a polite name for Brown’s business — Crown Finish Caves, a cheese aging facility — but there’s no masking what he admits to eating: fungus.

If a gray smudge of fungi appears on the cheddar in your fridge, you’d toss it in the garbage, not your mouth. So why is Brown’s mold gourmet, while your refrigerator mold is just gross? What makes a professional cheese-maker’s mold different?

Truthfully, not much.

If the right cheese curds from the right milk are at the right temperature, fungi become “the king of the mountain,” says Dennis D’Amico, a food microbiologist at the University of Connecticut who studies cheese production. Under the correct conditions, mold spores thrive on proteins, fats, sugars and the remains of the original bacteria that turned the milk into cheese. As the mold spreads throughout the cheese and its exterior, it continues the transformation that the bacteria started.

So when human teeth finally sink in, they bite into a new set of even smaller active molecules. And if the cheese is blue cheese, where the bacteria P. roqueforti dwell deep inside, enjoying a slice means consuming living fungi in the middle of their own midday snack.

The flavors, smells and textures specific to each type of cheese are due to various combinations of fungi species. A Brie or Camembert, for example, requires at least four types of mold. One, G. candidum, produces a sulfur flavor and contributes to the creaminess of the cheese. Another, P. camemberti, blossoms into a distinct white rind. The symphony of mold makes the final texture and mushroomy, sweaty taste.

But while the concerto is beautiful, the identities of all the musicians remain mysterious.

Identifying all of the active fungi in a cheese is “an endless, endless rabbit hole,” says Brown. Most of the moldy cheeses we have today are happy accidents, D’Amico said, the details of which can only be understood with elaborate lab analyses.

In the meantime, cheese agers like Brown stash freshly-made wheels in caves and vaults cultivated with ecosystems of mold, using techniques that have been employed for centuries. In recently-converted cheese facilities like Brown’s, cheese agers calibrate portions of their caves to specific temperatures and moisture levels. Each alcove is dedicated to one kind of cheese. Man-made caves like Crown Finish rely on samples from natural cheese caves to introduce the ideal mold culture into each separate nook.

“By making that same cheese over and over, you feed the same ecosystem over and over again,” says D’Amico. Brown watched this growth happen at Crown Finish. It took the caves about a year of repetitive use for enough mold to end up on the finished cheeses, he explains.

This method isn’t foolproof. A soil mold called mucor, which bears an uncanny resemblance to cat hair, thrives in the same environment that desirable cheese fungi needs. Brown does his best to keep the mucor out, but sometimes ends up having to throw out unsellable wheels of cheese.

In a way, refrigerators aren’t much different than these cheese caves. Mold spores, which are in the air all the time, land on bricks of cheese in the fridge just like they land on cheese wheels in a cave.

The major difference is that kitchen molds generally produce a “basement, musty flavor” that isn’t appreciated in the cheese community. “If it was, we’d harness it,” says D’Amico. Instead, cheese-making literature indicates the preferred mold qualities to be “barnyardy”, “gamey” or even “human feet” like.

Some of those descriptors might flare nostrils, but Brian Keyser promises there’s more to a cheese flavor than stench. The owner of Casellula, a cheese-centric restaurant in New York, Keyser says other flavors are playing in every cheese – some sweeter, some saltier. “When those flavors are in balance – that’s how you get pleasure,” he explains. “But you have to get used to it.”

Keyser is so accustomed to cheese rot that household mold doesn’t faze him. “If I was blindfolded, I’m not sure I’d be able to tell if household black mold was on a brie – I’ve never tried.”

And nor should you. D’Amico advises against eating fungi that grows on cheese at home, mostly because these unidentified, uncultured species might cause allergic reactions. As with most cheeses, there’s a simple solution: cut off the yuck. “If you cut mold away to the depth where the cheese tastes good again, you’re probably back to square one,” he says.

The Mayo Clinic and U.S. Department of Agriculture mostly agree. The softer the cheese, the easier it is for mold to penetrate the entire sample and bring potentially dangerous bacteria with it. So if a soft cheese like ricotta is moldy, consumers should toss the whole thing out. But if it’s a more solid cheese like cheddar or gorgonzola, hacking off the offending portion and proceeding to munch is fine.

If the mold in your home is creeping up your walls and not your cheese, those spores are something else. They tend to appear with unusually high levels of moisture in the building, like flooding damage that hasn’t dried or a poorly-ventilated bathroom. Most only become a problem for people who already have allergies or lung problems.

For the most part, Brown thinks the American aversion to mold is just a cultural fear, one he grew up with as well. U.S. palates tend not to welcome mold like many foreign palates do. Part of the challenge for American cheese makers, Brown explains, is finding a cheese style that hearkens back to European classics but without the heavy mold Americans tend to reject.

Cheese, after all, “is just fermented dairy,” Brown says. “Though my mother would be disgusted by that.”