This article was originally published in Knowable Magazine.
Every morning, for three months of the year, Lola wakes up at 8 and goes hunting. She races past oak trees, running at full speed through a 50-hectare field set in the southern end of the province of Buenos Aires, Argentina. The daily challenge—to find her elusive prey—never fails to excite her. She darts from place to place until faltering at last: 40 minutes into her day, she gets distracted or simply gives in to exhaustion.
Lola is a Brittany, and beneath her orange-spotted white coat is the agile body of a hunter. But her most important tool is her sense of smell. “Through training, dogs learn to recognize substances in their long-term memory—in this case, the smell of truffles,” says the dog trainer Germán Escobar.
A graduate of the University of Buenos Aires who originally hails from Colombia, Escobar has trained Lola and the eight other dogs of the Argentine truffle farm Trufas del Nuevo Mundo, located in Espartillar, a small town of 785 inhabitants.
With up to 300 million olfactory receptors in the nose—far more than humans have—and a region in their brains dedicated to odor analysis that, in proportion, is 40 times larger than that of Homo sapiens, trained dogs are able to do what no person can: track one of the most valuable and desired delicacies—the “black diamond” of the kitchen—deep underground.
For centuries, certain prized truffles were found mostly in European countries such as Spain, Italy, and France, where they grow in the wild. But over the past 50 years, truffle production has experienced an incredible global expansion, thanks to cultivation techniques that have given rise to farms in far-flung regions. Today, the United States, China, and Turkey, as well as countries across the Southern Hemisphere—Australia, New Zealand, South Africa, Chile, and Argentina—have emerged as new producers of the famous fungi.
At least 180 species of truffle are known, although only a fraction are of any commercial interest. The black truffle is one of the most celebrated and coveted: A kilogram of black truffles can sell for over $1,000. Another highly valued species—for which festivals are organized in Italy every year—is the white truffle, also known as Trifola d’Alba Madonna (Truffle of the White Virgin).
World black truffle production has grown in recent years thanks to the increase in cultivation of this prized fungus, according to a 2021 analysis published in the journal Forests. Spain leads world production of black truffles, with an annual average of 47 tons, followed by France and Italy.
Each of these natural jewels—black, rough, spherical, some as big as apples—is a miniature aroma factory. Some say the black truffle smells like cold mountain air or damp earth. Others say it evokes the smell of boiled potato, cauliflower, black olive, butter, mushroom, sulfur, or garlic.
In 1825, the French gastronome Jean Anthelme Brillat-Savarin crowned it “the diamond of the kitchen” and highlighted it as an aphrodisiac. The Italian composer Gioachino Rossini went further, declaring it the “Mozart of mushrooms.” And it was said that the English poet Lord Byron kept a truffle on his desk, confident that its perfume would stimulate creativity and attract the muses.
The truffle’s unique aroma is the result of a set of volatile organic compounds produced by the fungus. Far from being the result of a single molecule, the odors we perceive are produced by tens or hundreds of these invisible airborne particles. The molecules are all around us, and those that are generated by living organisms directly or indirectly influence the life of plants, insects, and even humans by contributing to communication, mating, and even the generation of flavors and aromas.
Of all fungi, truffles are among those that emit the highest amount of volatile organic compounds. More than 200 VOCs have been identified so far in various truffle species. Both black and white truffles pump out a mixture of alcohols, ketones, aldehydes, dimethyl sulfide, dimethyl disulfide, diacetyl, and other compounds.
“The aroma potency varies according to truffle type,” wrote the Italian chemist Elisabetta Torregiani and her team at the University of Camerino in a 2020 paper published in the journal Molecules. “Black truffles are considered to be the most aromatic of all,” summer truffles are the least, and white truffles are in the middle.
In addition, “the truffle’s aroma changes throughout its maturation,” says the researcher Eva Tejedor Calvo of the Center for Agricultural and Food Research and Technology of Aragon, in Zaragoza, Spain. Tejedor Calvo traveled to Argentina to study the aromatic differences between that country’s black truffles and Spanish truffles. “We know that, depending on the locations within the same country, the aromas can change,” she says. “They can also vary depending on the climate, depending on the soil, even between two trees in the same field.”
The aromatic potency of these fungi, which grow underground in complete darkness and attached to tree roots, serves a purpose. It is an evolutionary strategy for their survival as a species.
“Fungi are so smelly because they communicate chemically with other organisms in their environment,” explains Joan W. Bennett, a microbiologist at Rutgers University and co-author of a report on aromatic diversity in the fungal kingdom in the 2020 Annual Review of Microbiology. “Fungi do not have nervous systems, so they must use other means of defense and dispersal. For example, some of the volatile compounds attract insects that clearly help with the dispersal of their spores. While hundreds of VOCs associated with molds and fungi have been chemically identified, we are only now beginning to understand their functionality.”
“Their delicious aroma and nutritional power attracts animals that benefit from eating them, and they carry them in their intestines and thus disperse them in faraway places,” explains the Argentine mycologist Francisco Kuhar, a researcher at the Multidisciplinary Institute of Plant Biology of the National Scientific and Technical Research Council of Argentina, who co-wrote the book Crónicas del Reino de los Hongos (Chronicles of the Kingdom of Mushrooms). “We can say that their exquisite aroma was selected to use us animals to disperse them.”
This sophisticated strategy of olfactory manipulation extends throughout the mushroom family. Truffles use it in a similar way as flowers that rely on insects and birds as dispersers and pollinators. “Unlike most fungi that spread their spores through the air, truffles are found underground and require animals to help with their dispersal,” Bennett says. “It is believed that the truffle odor evolved because volatiles can diffuse through the soil and attract animals to eat and further disseminate their spores. This production of pungent cocktails consisting of volatile compounds draws a set of animals that truffles have co-evolved with, or at least adapted to, in order to facilitate spore dispersal.”
Pigs are one of these animals.Black-truffle hunters in Italy and France are said to have made use of trained pigs since the 15th century, especially females, which are particularly attracted to the intoxicating smell of the truffle: It emanates a chemical scent similar to andostrenone, a sex hormone that is also produced by boars.
The problem is that these animals are mesmerized not only by the truffle’s aroma but also by its taste, and it is very difficult to train them not to devour it. For this reason, truffle pigs were banned in Italy in 1985. There, professional truffle hunters (known as tartufai) must be licensed. They roam the fields with trained dogs, and their knowledge, which has been passed down orally for centuries, is included in UNESCO’s Representative List of the Intangible Cultural Heritage of Humanity.
In the 1880s, forest biologist Albert Bernhard Frank began to explore the possibility of growing truffles in Prussia. Although Frank failed to come up with a commercial method for cultivating truffles, the meticulous botanist’s many years of study were not in vain, as the plant ecologist David W. Wolfe recalls in his book Tales From the Underground: A Natural History of Subterranean Life. Frank noticed that truffles never grew independently; they always appeared near oak, hazel, poplar, or beech trees. He surmised that the truffle was a parasite. Later, he figured out that the two organisms work in partnership. Trees depend on fungi to help gather essential minerals, and truffles, which cannot photosynthesize, receive nutrients from the tree’s roots. In 1885, Frank described this symbiotic relationship with the term mycorrhiza (from the Greek myco, meaning “fungus,” and rhiza, meaning “root”).
Since then, intimate associations between plants and fungi have been identified in fossils dating back more than 450 million years. Today, more than 200,000 plant species are known to harbor mycorrhizal fungi.
“Mycorrhizal fungi extend the plant root systems, and these fungi ‘forage’ the soil for nutrients, especially nitrogen and phosphorus. They can also confer drought and pathogen resistance,” notes Serita Frey, a University of New Hampshire ecologist who describes this symbiotic link in a paper published in the 2019 Annual Review of Ecology, Evolution, and Systematics. “In exchange for these vital services, the plant provides the fungus with energy in the form of sugars, which the plant makes through photosynthesis.” She adds that some plants cannot survive without their fungal partner: “They have become dependent on the fungi for nutrition.”
In his book Truffle Hound: On the Trail of the World’s Most Seductive Scent, With Dreamers, Schemers, and Some Extraordinary Dogs, Rowan Jacobsen points out that truffle cultivation remains as much an art as a science. Each farm follows its own techniques; some closely guard secrets. The truffle’s journey from spore to plate is fraught with biological uncertainty, economic competition, and logistical headaches.
Hundreds of conditions and variables must align: This finicky fungus grows only when environmental conditions (temperature range, well-marked seasons, rainfall or controlled irrigation) and soil conditions (acidity, humidity, minerals such as phosphorus and potassium) are exactly right.
New inoculation techniques developed in France in the 1970s opened the door to growing the species in managed plantations. “In a nursery, it’s first a matter of attaching the fungus spore to the roots of the tree,” explains Faustino Terradas, the sales manager of Trufas del Nuevo Mundo. “The spore then begins to germinate and generate a mycelium, or a fungus root, that is going to cover the root of the tree. Then it is taken to the field and planted.”
During the first few years, the tree’s health is cared for, the acidity of the soil is controlled, and water is supplied through irrigation in order to generate the conditions for the underground development of the truffle. “During the spring, the primordia or small truffles, red on the outside and white on the inside, are generated,” Terradas says. “From then on, it matures. In autumn, it widens. And in the winter is when it finishes ripening.”
Yields in France fell dramatically in the 20th century—first because of the closures of truffle fields during the world wars, and then because of decreasing rainfall and rising temperatures.
This situation has boosted the black truffle’s expansion. Black truffles now inhabit continents where they were not found a hundred years ago. In recent decades, attempts to domesticate it have spread around the world: After centuries of truffles being a delicacy in Europe dispersed by dogs, pigs, squirrels, and insects, it is now humans, motivated by the mushrooms’ special aroma, who are driving their planetary migration.
The first U.S. black truffle was harvested in Northern California in 1987. In 2009, Chile became the third country in the Southern Hemisphere to cultivate truffles, after New Zealand and Australia. According to the mycologist Ian Hall of the Royal Society of New Zealand, who developed methods for the first truffle plantations in the Southern Hemisphere, there may be as many as 1,000 truffle farms outside Europe.
In Argentina, where harvesting takes place in the colder months from mid-May to mid-September, Trufas del Nuevo Mundo got its first “black diamond”—weighing in at 69 grams—in 2016. Since then, this venture has expanded to 20,117 mycorrhizal trees, and the farm exports truffles to the Northern Hemisphere when they are out of season in Europe.
The truffle “has a lot of history, but there is little research,” Terradas says. “Wheat has been planted for [thousands of years], but the truffle only 50 years ago. We still have a long way to go to understand the truffle and its development.”