Chefology: Truffles, Demystified

Now that we’re in the throes of truffle season, chefs and servers are busy shaving slices of fungal gold on dishes all over town. To better appreciate your next taste of these earthly delights, here’s what you need to know about the science of growing and eating truffles.

What exactly is a truffle and how does it relate to a mushroom?

Truffles are underground mushrooms. Normally when mushrooms have “sex” and disperse their offspring (spores), they do it out in the open. Those brightly colored mushrooms in the forest that look like caps or cups are typical mushrooms that pop up from the ground. These mushrooms are lined with spores that disperse, land in a new location, and grow to become a new fungus.

Truffles, however, prefer to have sex in the dark. The gills that drop the spores of a typical mushroom are packed together in truffles to form a sac. It’s these inverted mushroom sacs that truffle hunting dogs find buried in the soil. When you eat a slice of a truffle, you are eating millions of tiny little spores that would have grown up to become baby truffle fungi.

Photo by Ben Wolfe

Every bite of truffle is packed full of thousands of microscopic spores. This summer truffle has been sliced in half to reveal a light interior where thousands of tiny sacs of microscopic spores (inset) are found. 

Why are truffles so rare and expensive?

Truffles are rare because they only grow in very specific conditions. Unlike other mushrooms that grow on dead logs or in the soil (see our previous post on nature’s three ways to make a mushroom), truffles need a live plant to grow in a relationship called the ectomycorrhizal symbiosis. The truffles get sugars from the roots of the tree and in return the truffles provide nutrients from the soil to their tree partner. Truffles only grow on certain types of trees, including oak, hazel, poplar, beech and pine.

The challenge in growing significant quantities of truffles is that you need to grow both the tree and the fungus—and you need them to cooperate with each other while a whole zoo of other microbes lurks in the soil. Scientists still don’t know all of the conditions that tell the fungus to make a truffle structure, so it’s impossible force truffles to grow. Growing the appropriate trees in the correct type of soil and climate is the best you can do—the rest is largely up to nature.

Most truffles are still harvested in Europe where they have been growing for millions of years. There has been considerable success growing high quality truffles in Australia and moderate success growing them in the United States.

What are the main types of truffles?

White truffles (Tuber magnatum)

The most highly prized, most aromatic, and most expensive truffles are the white truffles. Their season ranges from November to early January. Prices are usually near several thousand dollars a pound. This year’s white truffle season happens to be one of the best in a long time— it started early, prices are low (relatively speaking), and quality is high. If you’ve never had them, this is the season to try them.

Photo by Scott Jones

A trio of this season’s white truffles at No. 9 Park.

Black truffles (Tuber melanosporum)

Black truffles are somewhat more woodsy and mushroomy than white truffles, and not as aromatic. But these have great truffle flavor and are available from December through March when they come from France as Périgord truffles. In our summer, we get them from Australia. Depending on the season, black truffles are usually half the cost of white truffles.

Photo via Wikipedia/Wazouille

A cross-section of a Périgord black truffle.

Summer truffles (Tuber aestivum)

Like their cousin the black truffles, summer truffles and Burgundy truffles (Tuber uncinatum) are black on the outside. However, their interior is much lighter in color, ranging from light brown to white. These truffles tend to have minimal truffle flavor and instead have a simple mushroom earthiness. They’re the least expensive of all the truffles (about one tenth the cost of white truffles), and are available during summer where they come from Italy and France. These truffles are beautiful and delicious, but because of their simple flavor, they often leave people wondering about all the truffle hype.

Photo by Ben Wolfe

A cross-section of a summer truffle.

Other truffles

The three species of truffle described above are the major types of truffles used in restaurants around the world. But there are several hundred truffle species found around the world, and some of these lesser known truffles may one day break into the culinary scene.

Numerous species of desert truffles grow in arid regions in Europe, Africa, and Asia, and have played important roles in the cultures of many desert societies. American pecan farmers have been getting some help from American truffle scientists to explore the ecology and culinary potential of the pecan truffle (Tuber lyonii). Truffles can even be found in our own backyards, although it’s very unlikely that they’d be a species that would taste good. During his Ph.D. research, Ben detected truffles under an oak tree in Harvard Yard.

What chemicals are responsible for providing truffles with their distinct flavors?

There are many volatile compounds that scientists have identified in truffles that contribute to their aromas. Each species has a different set of chemicals that provide unique aroma profiles. In a study of the white truffle, 37 different compounds were found to be associated with typical white truffle aroma.

The one compound that is thought to be common across all truffle species is dimethyl sulfide. This is a volatile sulfur compound that is commonly associated with rotten cabbage aromas in ripe cheeses. This same compound gives truffles their funky earthy notes. Interestingly, dimethyl sulfide is also a major contributor to the smell of farts.

What is the best way to incorporate a truffle into a dish?

Scott loves to pair the white truffle with a Parmigiano-Reggiano risotto or perfectly scrambled eggs. He also loves white truffles shaved over handmade tagliatelle with plenty of butter and Parm. When using truffles with pasta, make sure the pasta is hot to help bring out the volatiles of the fungi.

Pair black truffles with with beef. More specifically, we love it with a roasted ribeye, topped with a slice of seared foie gras, and a Madeira pan sauce. Black truffle also pairs well with surf and turf.

For summer truffle, you can shave it on on anything you’d like to use to impress someone. Scott tends to use a dish with broth so that the limited truffle flavor is dispersed and somewhat more pervasive. Braised lamb shoulder with, say, salsa verde and bagna cauda? Shave some summer truffle on it.

Why are European truffles becoming more difficult to get?

European truffle harvesters have noticed a steady decline in abundance of truffles over the last several decades. Scientists believe that climate change may be partly to blame. Summers are becoming dryer in many regions where truffles are grown and these dry summers inhibit the growth of truffle fungi. This could actually be a good thing for other parts of the world, however, where climate change is creating new environments where truffles could be grown.

Another threat to the future of European truffles are weedy Chinese truffles that are invading European truffle grounds. It’s unclear how they got there, but a truffle species from China (Tuber indicum) has been found in Italian truffle grounds. French truffle scientists freaked out in a paper published in 2008 when this discovery was made, because these truffles are thought to be more aggressive than the native truffles and could replace these highly prized species. The French believe that the Chinese truffles have much less flavor than their European counterparts. Chinese truffles are sometimes laced with synthetic truffle flavor and sold as fraudulent versions of their European truffle counterparts. Unlike a dandelion, it’s difficult to manage weedy fungi that spend most of their time underground. So the Europeans have little in the way of management options to protect their truffle heritage. Check out this awesome 60 Minutes report for more on the threats to the European truffle market.