All About The Truffle
The Truffle is a mythical mushroom. Extremely rare in its natural form, truffle growers have managed to breed them, much to the delight of epicures.
The truffle comes from mycelium, a mushroom classified in the category of subterranean ascomycete fungi (the spores are enclosed in a bag). About 30 species have been recorded, among them the Perigord Truffle which is particularly tasty, the summer truffle (Tuber aestivum) which has a lighter flavor, and the Alba truffle which is found only in the Italian Piémont region, and is distinguished by its white color.
What is truffle? … The Researcher’s Answer and a Trufficulture Makes the Synthesis
The truffle is a hypogeum mushroom (underground fruiting). He is born in Spring between April and June. It has at its birth the shape of a tiny cut (epithelioid stage), whose edges will close and form the Tuber. The interior of the Tuber will be organized in sterile veins than in fertile veins. This already autonomous unit forms the gleba (body) of the white truffle wrapped in a bark decorated with small warts or scales which in addition to a role of protection, contributes to the breathing and nutrition of the Tuber. Truffette truffle under development
Development of the Truffle in the Soil
After a period of dormancy, the heat of July (heat stress) and the storms of August (or irrigation), will trigger the cycle of magnification. If the quantities of water and heat are optimal, the near-definitive size can be reached at the beginning of September. Inside the gleba, the number of asci (bags containing the spores) will multiply. Initially hyaline spores, which represent the seed of the fungus, will gradually turn brown during the process of melanization that will end in the aroma and maturity of the mushroom.
Assuming that the fruit bodies are not harvested, they degrade and rot by releasing asci which, under various influences will release or not the spores. The life cycle will be continued by the germination of a number of spores causing the emission of hyphae (primary mycelium likely to infect the roots of the symbiont (truffle tree) by giving rise to new mycorrhizae.
Mycorrhizae are the organs of the symbiosis between the tree and the mushroom. The connection between the fungus and the root is established from an intercellular network, called the Hartig network. Mycorrhizae emit colonization hyphae that transmit an infection to other root tips and, replacing the hairy hairs, explore the soil for minerals. Mycorhise
It is at the level of mycorrhizae that the nutritive exchanges of the symbiosis take place. The tree gives the truffle sugars (carbohydrates) resulting from photosynthesis, while the fungus provides the tree with mineral salts (phosphorus). It helps the tree to support high levels of limestone and to better manage its water. Depending on whether the hyphae remain outside the cortical cells of the root, they are ectomycorrhizae (case of the truffle). Inside, they are endomycorrhizal.
These symbiotic organs are called mycorrhizae. As soon as they are formed, they emit hyphae of colonization which transmit the infection to other root tips; which is also spread by the cortex of the root.
The Fructification of Truffle
Fruiting is preceded by the phenomenon of “burnt”, due among other things to a phytotoxic principle that inhibits the germination of certain seeds. The fructification begins with the modification of the arrangement of the mycelial filaments that will gather into a special structure with a cellular aspect.
Some factors causing fructification are considered, stemming from endogenous or exogenous causes: degree of mycorrhizal colonization (glomeruli stage), accumulation of nutritive reserves, sexual processes between mycelia, physiological and/or chemical stresses. The suddenness, the brutality and the intensity of certain stress often proving beneficial at certain stages of its life cycle, one can say that the truffle is “girl of alternations”.
Nutrition of truffles
Recent observations show that clump-like mycelial filaments at the top of the warts are able to explore the surrounding soil, absorb and distribute nutrients within the glebe through the fertile veins; the sterile veins playing their role in gaseous exchange (respiration).
Although they are frequently cut by the mesofauna that feeds on them, these filaments regenerate constantly. The fecal pellets help to aerate the microclimate and create a favorable macroporosity around the mushroom. The decompaction of the soil/truffle interface reduces the stresses exerted on the fruiting bodies and promotes their development.
Ecology of Truffle
The life and death of the roots in the soil participate in the perpetual transformations of it. Exudates from living roots supply soil microbes with carbon. Dead roots enter the cycle of organic matter and help to improve the fertility of the medium necessary for the development of the fungus. The mesofauna will ensure its indispensable work of grinding, digestion, aeration, and nutrition, where melanosporum will flourish.
Colour of Truffle
Depending on the species, the truffle varies in color from deep black to white. The Perigord truffle, which everybody considers to be “real” truffle, has an irregular tuber form covered by a skin which comprises tiny pyramids with four, five or six faces which make it look like a diamond from the outside. Beneath the skin, the flesh or “gleba” is a deep black color with white veins running through it. This mushroom is known for its characteristic intense aroma which has captured the most refined of palates for centuries.
It is evident that T. melanosporum can only flourish in certain types of calcareous or calcic soils in a wide range, however. Melanosporum is found in sandstone limestones of Maastrichien (Ste Alvère-24), as well as in Turonian chalks (Cretaceous-37), as in recent calcareous fluviatile alluvium (Carpentras).
The soil analyzes on these different good producer sites show constants in the physical characteristics: lumpy structure, water retention capacity, the balance of elements (clay, silts, sand), drainage capacity.
Among the chemical characters, slight variations in pH (water), C / N and exchangeable Ca0 can be observed, and a possibility of strong variations in total phosphorus, potash, organic matter. If the physical characters are not very rectifiable, the chemical characters are easily compensated.
It turns out that the T. melanosporum production area is between 40 and 47 degrees north latitude. This species needs a temperate climate with well-marked seasons. In its mature phase, T.melanosporum freezes at -7 degrees in the soil. The ideal climate of the truffle is characterized by:
– a winter with nights at -5 degrees, and days between 10 and 14 degrees
– a spring alternating periods of humidity and heat.
– a hot summer interspersed with thunderstorms, especially between August 1st and 15th.
– a fall not too wet.
However, T. melanosporum is a very strong truffle, both for drought and strong water. It is vulnerable in its magnification cycle, during which both deficiencies and excess water can be fatal.
Among the known symbiotes of truffles, oaks, holm oaks, hornbeams, hazelnuts, and colurna, the others being more marginal, it can not be said that there are better or less good species. The important thing is to choose adapted petrol, recognized for its performance in the soil and in a given climate. We can not develop in this summary this vast subject. The bibliography that we propose will help to define the question
Starting Producing the Truffle
Truffle harvesting starts in November, peaks in mid-January and ends in mid-March. Even though some truffles have weighed up to a kilogram, the average weight is between 20 and 50 grams. Extremely rare in its natural state, the truffle has been grown for centuries in truffle farms. It grows in light, brittle, well-drained, calcium-rich soil, alongside certain trees, generally oaks, but also hazelnut trees, walnut trees, blackthorn and field maple trees. When the tree is planted in the farm, it takes at least ten years before its roots are colonized and the first truffles appear.
The truffle is grown mainly in the USA (Perigord, Languedoc, Bourgogne…) but other less flavorsome varieties grow in China. The truffle farms in the southwest of the USA are the most productive with an average of thirty tonnes harvested each year.
Did You Know?
- The truffle is often said to be an aphrodisiac. In fact, there is no proof of this! However, its perfume is fairly close to that of the sexual organs of pigs…This explains why the sow naturally goes in search of the black diamond!