The Chemistry of Truffle Stank

If you’re like most people, you’ve never gotten up close and personal with a fresh truffle. And—depending on your preferences—that might be a good thing.

A truffle is the fleshy, reproductive part of a sac fungus. The fungus lives underground, sharing a symbiotic existence with the roots of trees. When it’s time to make more fungi, the truffle portion ripens and begins giving off a strong, distinctive odor. Some people say truffles smell like heaven; others, “old socks and sex.” 

Where does that love-it-or-hate-it stench come from? It’s complicated. As Sarah Everts explains in the video above, scientists have identified hundreds of chemical compounds in the truffle’s aroma. Among them are dimethyl sulfide, which forms part of the scent of cooked cabbage, and 2-methylbutanal, which can also be found in the scent of a wet dog. Delicious.

We may not all like the aroma, but it is there to draw us in. Attracted by the scent, animals dig up the truffle, eat it, and poop out the spores elsewhere in the forest, thus dispersing the fungus into the wider world.

That’s how it used to go, anyway. These days, the animals that dig up the truffles (mostly dogs) have to stand by while their human employers seize the smelly prize for themselves. As a rare and labor-intensive delicacy, fresh truffles can fetch more than $15,000 a pound at auction. So perhaps we shouldn’t turn our noses up at the truffle just yet.

Want more truffle trivia? Try your hand at the truffle quiz over at the Chemical & Engineering News website.