Truffles are hypogeous (underground) versions of mushrooms. They don't form a prominent stem and their spore-bearing surfaces are enclosed. They rely on animals eating them (mycophagy ) to distribute their spores, instead of air currents like mushrooms. Truffles resemble small potatoes, and often between the size of a marble and a golf ball (see the photo gallery ). There are hundreds of different kinds of truffles, and while none are known to be poisonous, only a few of them are considered to be delicacies by humans. Truffles (and mushrooms) are only the "fruit" of the fungus (like an apple to an apple tree); the main perennial fungal body exists as a web of filamentous hyphae in the soil. All of the truffle fungi form mycorrhizae with the roots of trees, and are essential to the trees' ability to acquire nutrients. The belowground fruiting habit of truffles is thought to be an adaptation to forest fires or dry or frosty periods, in which aboveground mushrooms are more vulnerable. Oregon State University Extension has published a nice overview of truffles available here, "An Oregon Garden Guide to Truffles."
What is mycophagy?
As most truffles never break the surface of the soil, they must rely on animals to eat them and distribute the spores in their scats. The word "mycophagy" comes from the Greek words "mykes" (fungus) + "phagein" (to eat). Some animals, like the red-backed vole, eat truffles almost exclusively. In order to be located by hungry critters, truffles have evolved strong scents that, as they mature, can be detected from a distance by a suitably sensitive nose. Depending on the species of truffle, to humans these scents can be pungent, fruity, unpleasant, or delectable.
What is mycorrhizae?
Mycorrhizae is a symbiotic (mutually beneficial) association between some kinds of fungi and plants. The word "mycorrhizae" comes from the Greek words "mykes" (fungus) + "rhiza" (root). Fungal filaments (hyphae) are much more efficient at extracting water and nutrients from the soil than root hairs - it has been reported that there are as much as 100 meters of fungal hyphae in one teaspoon of healthy forest soil. The fungal hyphae not only permeate the soil, they penetrate the root cells of plants and facilitate a nutrient exchange where the host plant gets needed nutrients from the soil via the fungi, and the fungi (which cannot perform photosynthesis) get their needed sugars from the host plant. Many plants will not grow well at all unless they have mycorrhizal fungi on their roots helping them get nutrients.
What is the role of truffles in ecosystems?
Truffles (and mushrooms) are the "fruit" of underground webs of fungi. The fungi of all truffles (and many mushrooms) are mycorrhizal. Mycorrhizae are essential in assisting trees obtain nutrients and water from the soil - without mycorrhizae we would not have forests as we know them today. Truffles are also an important part of the food chain via mycophagy. For example, flying squirrels rely on truffles for food, and spotted owls rely on squirrels for food. In turn, the fungi rely on the squirrels (and owls!) for spore distribution, the trees rely on the fungi for nutrient acquisition, the fungi rely on the trees for energy (sugars from photosynthesis), and the owls and squirrels rely on the trees for habitat.
What are "True" vs. "False" truffles?
In Europe, the term "truffle" in the very strictest ("true") sense has historically only referred to those hypogeous (belowground) fungi that were gourmet edibles. primarily in the genus Tuber. Tuber s are members of a larger grouping of fungi called Ascomycetes. For some folks, only Tuber s and their close relatives are considered "true truffles" (all others being "false truffles"), and for other folks all hypogeous Ascomycetes (irrespective of culinary qualities) are called "true truffles". However, there are many, many other perfectly nice species of hypogeous fungi, both Ascomycetes and Basidiomycetes. that are not particularly prized as food outside the squirrel community. Nowadays many folks have discarded the "true truffle" and "false truffle" distinctions for a more egalitarian nomenclature, and are quite comfortable simply calling all hypogeous fungi TRUFFLES.
What are Ascomycetes and Basidiomycetes?
Ascomycetes and Basidiomycetes are two major groups of fungi (like cats and dogs are two major groups of animals). Unlike cats and dogs, the distinction between Ascomycetes and Basidiomycetes is based on microscopic characteristics, namely the manner in which the spores are produced. In Ascomycetes, the spores are produced inside of sock- or sac-shaped structures called asci. In Basidiomycetes, the spores are produced on prongs on the outside of structures called basidia. As a general rule, Ascomycetes tend to have a brittle texture (such as Morels ), and hypogeous (belowground) Ascomycetes (eg. truffles) are frequently - but not always - hollow (such as Genea ). Basidiomycetes are fleshier in texture (all gilled mushrooms are Basidiomycetes), and the hypogeous Basidiomycetes tend to be squishy or spongy on the inside (such as Zelleromyces ). This key may help in distinguishing "asco's" from "basid's". There are two other groups: The Zygomycetes form their spores individually on specialized "suspensor cells" and contain one truffle-forming ectomycorrhizal genus, Endogone . The Glomeromycetes form their spores individually or in clusters at the ends of hyphae. Only one genus in this group forms truffles, Glomus .
Are any truffles poisonous?
No truffles are known to be poisonous to humans (but we don't know everything. ). This non-toxicity seems sensible, considering that truffles rely on small animals (via mycophagy ) to distribute their spores. That said, ALWAYS be absolutely sure of the identification of anything you are considering eating. Many poisonous Amanita and Cortinarius mushrooms start out as belowground "eggs " that can be dead-ringers for truffles at a glance. The Oregon white truffles that most folks around here are interested in eating (Tuber gibbosum & T. oregonense ) are firm and brittle, will have a beige to smokey-colored marbled interior, and a pleasant earthy odor. Mushroom eggs (and many truffle species that are only appetizing to squirrels) are generally more squishy, spongy, or cartilaginous - always check every truffle you intend to eat, different species frequently intermix.
Where are truffles found?
Truffles can potentially be found almost anywhere there are trees. Only a few families of trees (such as maples and cedars) do not associate with truffle-forming fungi. Truffles fruit throughout the fall, winter, and spring, depending
on species and locality. They usually occur at the interface between the organic litter and the mineral soil, about one to six inches deep, but can emerge to the surface or be more than a foot deep. Evidence that small animals have been digging in an area recently is often a good indication that truffles may be about. For a detailed accounting of what kind of habitat a particular truffle species likes, and when it is likely to be found, see the Specific Habitats page.
How are truffles found?
In North America, truffles are found by raking the organic litter away with a 4-tine garden rake. Find suitable habitat (most any forested area; see above) and gently peel back the litter layer (remember to replace the litter when you are done and try to leave the area as you found it). Look for things that look like little potatoes, often beige, yellowish, or reddish brown (see the photo gallery). If you find one it will be immediately apparent that it is not a dirt clod. Finding truffles takes a little luck and a lot of patience. Sometimes they just aren't there, but you never know until you look. In Europe, pigs and dogs have been used for centuries to help find truffles.
Pigs vs. dogs?
The scents produced by truffles to encourage mycophagy sometimes attract animals that are larger than squirrels. Some truffles, including the gourmet edibles Italian perigord, French white, and Oregon white, produce a scent that mimics a male pig sex hormone. It is for this reason that female pigs have been used historically in Europe to help find truffles. More recently, dogs have become the preferred truffle hunting companion for several reasons, among them 1) Dogs can be trained to find, but not eat the truffles, and 2) Dogs are much easier to get into the back seat of a car.
Truffle maturity and the market
In the United States, we have not advanced to the point of using trained animals to help find truffles. This is unfortunate not only from an efficiency standpoint, but also a market reputation standpoint. The reason for this is that truffles only develop the aroma that attracts animals and excites chefs when they are fully mature. Thus, pigs and dogs will only indicate where mature truffles are. In North America where we humans (with our lousy noses) rake indiscriminately for truffles, we frequently get as many immature specimens as mature ones. Commercial collectors often have incentive to sell all the truffles they find, whether they are mature or not. Immature truffles have little culinary value, as they have not yet developed the pungent aromas that chefs seek. The frequent presence of immature specimens in commercially available Oregon white truffles has diminished their reputation and value on the world market compared to their European counterparts.
Truffle dog training?
NATS offers occasional truffle dog training seminars in Corvallis, Oregon. Contact Marilyn Hinds for information. Below are some dog trainers who offer specialty courses in canine trufflehunting, in no particular order:
Pacific Truffle Dogs offers truffle dog training courses in the Portland area.
Umami Truffle Dogs offers truffle dog training courses in Veneta, west of Eugene.
NW Truffle Dogs offers truffle dog training courses in the Portland area.
Trifecta Training offers truffle dog training courses in the Eugene area.
Toil and Truffle offers truffle dog training courses in the Seattle area.
The general principal is to start when the dog is young, and get them used to the scent of truffles by having them fetch a sock with mature truffles inside, and gradually work up to finding the hidden, then buried sock. Some folks have used a pungent cheese (like limburger) as a surrogate for mature truffles. Links to accounts of truffle dog training are below:
Oregon black truffle (Leucangium carthusianum. formerly Picoa carthusiana )
Native to France, Italy, and Spain, the summer truffles are usually at their best in July, but can be found from May to October. They have a black exterior and off-white interior, and a relatively light scent. This truffle has been established on plantations in Sweden and New Zealand.
Tuscan truffle (Tuber borchii. formerly Tuber albidum )
Similar to the Italian white truffle in appearance, having a chestnut to muddy tan exterior and a softish interior equally divided between chocolate brown and white. The flavor can be distinctly garlicky.
Pecan truffles (also called Texas truffles) are found from New Mexico to the gulf coast and eastern seaboard to the great lakes and eastern Canada. It is not limited to areas with pecan trees, but was named based on the habitat in which it was discovered. More information can be found at this University of Georgia website. Click here for a story about Pecan truffles from the Hilton Head Island-Bluffton Island Packet, and click here for a story about Pecan truffles from the New York Times.
Chinese truffles (Tuber sinense. Tuber indicum. and Tuber himalayense )
These are three distinct species found in southwest China, but pickers tend to lump them together as Chinese truffles. This is unfortunate since the flavor and quality vary from one species to another. First marketed in France in 1994, these truffles are now found in American restaurants at fairly reasonable prices, but their flavor and aroma do not come close to that of the French truffles, perhaps for the same reasons as Oregon white truffles (too many immature specimens ). T. indicum is recognizable by its brown interior and very fine white veins. T. sinense has a dark brown interior with large ivory veins, and is said to be chewy and oily with a bitter aftertaste.
Desert truffles (Terfezia boudieri. Terfezia pfielii. Terfezia claveryi. and others)
Native to northern Africa and the Middle East, these truffles have been a staple for many nomadic tribes for millenia. Sometimes called the Lightning Truffle, they often fruit shortly after thunderstorms wet the desert. There is an account of desert truffle culture here .
Truffles are generally used raw, or very lightly cooked, because the flavor compounds are highly volatile. Truffles go very well with brie cheese (doesn't everything?). NATS has compiled a cookbook of truffle recipes. a few of which are posted on the Recipes page. Below are some links to other truffle recipe websites: