Jun. 18, 2014

On the Oregon Truffle Scent

by Julie Leibach

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Truffle forager Kris Jacobson was hesitant when a young couple from New York called her last month, asking her to guide a foray into the Oregon woods. Peak season for certain truffles was winding down, and she didn’t want her potential clients to be disappointed with a small haul. “I've never been skunked before, and I certainly don't want to get skunked by taking you guys out,” she told them. So Jacobson—who runs Umami Truffle Dogs, which specializes in wild truffle forays and harvesting—did what seemed right: She tried to discourage the two from coming.
 
They were undeterred. More interested in a novel experience than a big fungal payday, Lisa Shu and Matt Wilson arrived a couple weeks later to join Jacobson and her dog, Ilsa, on a hunt through a dense forest in the Coast Range, which courses along the western edge of Oregon.
 
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Typically, this particular forest is so dark that Jacobson must attach a red strobe light to Ilsa’s orange harness to keep the dog in sight. But on this mild afternoon in late May, the sun shone brightly as the group worked their way among native sword ferns and scattered carpets of green moss. Needles shed from looming decades-old Douglas fir trees formed a soft duff atop the loamy soil that lent a spring to the step. This habitat was prime Oregon black truffle territory.
 
At least 350 known truffle species grow in the Pacific Northwest, according to a 2009 federal report on truffle fungi—more than in any other region in the U.S. or in Europe, which is home to the French perigord, burgundy, and notorious Italian white truffles (known to fetch $2,000 a pound). Only Australia grows more species, boasting “a tremendous diversity” of around 2,000, says Jim Trappe, a professor in the Department of Forest Ecosystems and Society at Oregon State University and a world expert on truffles.
 
While plenty of truffle species in the Pacific Northwest have culinary potential, most are rare and hard to find. In Oregon—which harvests the bulk of native truffles in the U.S.—four culinary species are sought most and sold commercially: the Oregon black, the Oregon winter white, the Oregon spring white, and the Oregon brown, the most elusive of the group.
 
While fans claim that native Oregon truffles can hold their own in a pasta dish or cream sauce just as well as their European counterparts, their reputation hasn’t always been sweet. For decades, chefs overlooked the state’s culinary truffles as a wild delicacy, according to Trappe.
 
Over the past few years, however, esteem for Oregon truffles has been growing locally and even nationally with help from the Oregon Truffle Festival, an annual winter event that brings together harvesters such as Jacobson, scientists, restaurateurs, and tourists to experience and promote the fungal fare. At the same time, truffle aficionados have lately been supporting a better method of foraging: dogs. As it turns out, what makes finding truffles easy with a dog is also what makes them so desirable as food—aroma.
 
 
Over the centuries, truffles have evolved multiple times from mushrooms. But unlike mushrooms that poke their heads above the soil surface with the help of a stem, truffle fungi are by and large stem-less—they resemble little potatoes or, in the case of the Oregon black truffle, lumps of coal—and most remain completely underground. Out of (human) sight beneath the soil, truffles get cozy with host plants, typically trees, through a symbiotic relationship called mycorrhiza, which translates quite literally to “fungus-root.”
 
To understand the relationship, first picture a tree’s taproot plunging under the earth like a carrot, with lateral roots extending to the sides. From those roots, tiny appendages half a millimeter thick, called feeder roots, amble a few millimeters into the soil to greet the hair-like filaments of the truffle mycelium. Like a glove cloaking fingers, the mycelium snugly encases the feeder roots while also penetrating several cells deep, almost as a pathogen might, according to Randy Molina, a former research botanist and team leader of forest mycology for the USDA’s Pacific Northwest Research Station. This intimate association is the mycorrhiza (and more specifically, most truffles form ectomycorrhizae, a specific association with feeder roots.)
 
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“The fungi are, in essence, an extension of the root system," says Molina, who’s worked closely with truffle expert Jim Trappe on fungus research in the Pacific Northwest. The relationship has something for everyone: The truffle receives energy in the form of simple sugars produced through photosynthesis, which it can’t make on its own. The tree, in turn, gets water and nutrients from regions of the soil that its feeder roots can’t reach. "[The fungus is] able to explore the volume of soil that may be a hundred to a thousand times the volume that the root can explore,” says Molina. “[It] is able to really get into every nook and cranny.”
 
While some truffles form ectomycorrhizae with multiple host plants (and one host can have multiple fungal associations), other truffles typically stick with one tree. Indeed, the wide variety of tree species that grows in the Pacific Northwest is one reason for the region’s truffle bonanza (variable climate is another).
 
In the case of Oregon’s well-known culinary truffles, the preferred arboreal companion is a Douglas fir. For a beginning forager, this is useful information—but it only takes a person so far into the woods. Finding the precise location of a truffle is another matter.
 
Hidden underground, truffles don’t betray their position with a tip of the cap like a forest-dwelling mushroom does. Instead, they toss out other clues in the form of volatile aromatic compounds that woodland animals—and well-trained truffle dogs—can detect. The smells are most potent once the truffles are ripe, the reason being a matter of fungal posterity.
 
 
Like mushrooms, truffles produce spores in a fleshy structure called a fruiting body. Rather than ejecting their spores into the open to be carried by the wind as a ‘shroom does, however, truffles keep them tucked away. As a result, the fungi can’t rely on the vagaries of weather for spore dispersal and instead depend on animals—everything from squirrels to bears—to find them, eat them, and defecate the spores out again, intact.
 
But for a truffle to make it into a digestive tract, “it needs somehow to convince some passing animal to stop what it's doing and come look for it and dig it up,” says Charles Lefevre, the founder of New World Truffieres, which specializes in truffle cultivation in orchards. Evolution’s solution to the problem, so to speak, was for truffles to spray a little perfume.
 
Kris Jacobson has trained Ilsa, a Belgian malinois (a type of shepherd), to track truffle aroma to the point of laser precision. When they’re out on a hunt, Ilsa works in a circle around her owner while Jacobson homes in on every sound and movement the dog makes. “If I can see her head turn as she's moving—turn sharply to the left or to the right—I know she's caught the scent of a truffle,” says Jacobson.
 
Once Ilsa turns her head, her body follows for a short distance. Then she reverses for a few paces, turns back again, and continues to zig and zag in the shape of a Wi-Fi signal until she’s pinpointed the smell. At the source, she starts digging at the earth. And somehow, “she literally will stop before she damages the truffle,” says Jacobson. “It's usually right below where she has stopped digging.”
 
“Trained dogs are just superb at finding the ripe truffles," says mycologist Trappe. Yet, while Europeans have used canines to harvest truffles for a century or longer, only recently have dogs hit the truffle scene in the Pacific Northwest, and more are in training (a few truffle foragers on the East Coast use dogs as well).
 
Instead, foragers historically used rakes, which led to indiscriminate digging as they searched for a fungus they couldn’t see. That led to a lot of mediocre hauls, says Lefevre. “The truffles are in the ground for months at full-size before they mature, and when you use a rake to harvest them, you mostly find immature truffles”—but immature truffles are worthless, because they have no “lovely aroma” says Lefevre. 
 
And when it comes to cooking with truffles, aroma is everything. “Too many chefs have been sold [immature] truffles that have no value and have been disappointed, so the Oregon truffles have acquired a kind of negative reputation," says Lefevre. “The purpose of the dog is to find truffles that actually have aroma, so they are performing the primary quality control function for us.”
 
 
“There's basically something called a ‘truffle paradox,’” says Jack Czarnecki, co-founder of The Joel Palmer House restaurant in Dayton, Oregon, whose menu revolves around wild mushrooms and truffles harvested with dogs on private lands that staff may access with permission (most culinary truffles probably grow on private lands). “Truffles by themselves have virtually no flavor,” he says. “If you taste them, they taste kind of like raw mushrooms—they have a vague, mild, buttery, nutty characteristic, but they don't taste at all like the way they smell.”
 
The so-called “flavor” in a truffle instead comes from the same volatile organic compounds that entice animals to dig through soil to find them. Those compounds are generally fat-soluble, which means that they’re attracted to other fatty substances, such as oil, eggs, and butter. Just placing truffles next to eggs in the shell is enough to infuse them with the truffle smell.
 
Each truffle species also has a signature scent based on a unique molecular makeup. “The black, for instance, is a combination of earth, chocolate, and pineapple,” says Czarnecki, while “the white is heady with the aromas of fresh cut grass, herbs, and garlic. They're very different from one another, and that's kind of fun.”
 
Truffles in general shouldn’t be cooked, because “the heat drives off the aromatics,” according to Trappe. One of the best ways to enjoy the “truffle experience,” he says, is to make truffle-infused butter. Sprinkle some truffles around a block of butter in a sealable container, close it tight, and let it sit for about a week in the fridge so that the butter can absorb the aroma and get “really truffly,” Trappe advises. After a week, bring the butter to room temperature, and immediately spread it on some warm, crusty white bread, letting it melt in. “That's when I think you get the purest sense of what the truffle aroma is all about,” he says.
 
“With any truffle, you want to keep it simple,” adds Czarnecki. “You want the truffle to be front and center.”
 
Charles Lefevre is doing his part to put truffles in the spotlight. In 2006, he and his wife founded the annual Oregon Truffle Festival, which promotes both the region’s native species as well as cultivars from Europe that are beginning to take hold in orchards.
 
“People are coming from all over the world, descending upon little Eugene,” says Jacobson, who has sponsored the festival in the past (her recent clients, Lisa Shu and Matt Wilson, learned about Jacobson's business by visiting the Oregon Truffle Festival website).
 
Among the events offered are forays into the woods, local Oregon truffle tastings, and truffle dog training workshops—and practically any dog can learn to do it (several years ago, “an ancient miniature dachshund” was the star of the show).
 
“We're trying to make this an authentic celebration of this region of the world,” says Lefevre.
 
 
After spending more than two and a half hours in the forest, Jacobson, Ilsa, and her clients enjoy a fruitful day. Instead of leaving empty-handed, Shu and Wilson have, with Ilsa’s help, collected several handfuls of Oregon black truffles. “Ilsa is probably the most amazing, the smartest dog that I have ever encountered,” says Shu. “There were no false positives, which is an incredible thing. She was right every single time.”
 
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Their haul also included one species that Jacobson didn’t recognize. “It smelled just like an Oregon black truffle,” she says, although it looked more like a brown one. She sent a sample off to a mycology lab for analysis a few weeks ago.
 
“I'm 99 percent sure that these are going to be a new culinary-type truffle,” she says. Indeed, preliminary results suggest that while others like it might already exist in laboratory collections, it’s an undescribed species most closely related to the Oregon black.
 
“To have these wild truffles in this small region of the United States that have this incredible aroma profile from one end of the spectrum all the way to the other side, it's really pretty mind-boggling,” says Jacobson, “and the rest of the world is going to discover them. It's just a matter of time.” One more reason to keep on digging.
 
About Julie Leibach

Julie is the managing editor of ScienceFriday.com. She is a huge fan of sleep and chocolate. Follow her @julieleibach.

The views expressed are those of the author and are not necessarily those of Science Friday.

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