Called mesoigrofilo and mesoterma, the Tuber Melanosporum, our black truffle, is found in natural truffle grounds located on lands with lower humidity and higher temperatures, compared to those suitable for the growth of the white truffle, the Tuber Magnatum Pico. Moreover, compared to the white truffle, the black one avoids high temperatures and it better tolerates both dry and cold weather. Usually it can only be found in soils of the summit glades or of other weakly inclined areas present on the main calcareous Mesozoic heights, that originated from the disintegration of calcareous or calcareous-marly rocks in the secondary era or rarely in the tertiary one.
We are talking about lands attributable to “Renzina” or “Terre Brune”. The physical and chemical analysis performed on soils collected in the quarries of black winter truffle show a considerable heterogeneity in the values of the examined parameters. They are rich in texture; they have a clay-loam texture which guarantees the preservation of a certain degree of humidity and provides the exchangeable ions (especially Ca and Mg); they have an alkaline ph with values even higher than 8. They have carbonates with high values and in particular the total limestone (CaCO3) can reach 60-70% and the one of the organic substance even 80%.
In addition to the macronutrients (nitrogen, potassium, magnesium, zinc) they contain important microelements such as copper and iron. And it’s the iron oxide that gives the lands their characteristic reddish color. The black winter truffle requires a relatively high total amount of rainwater (700-1000mm of rain), it avails of spring and autumn rainfalls and of frequent thunderstorms that intersperse the periods of summer drought. The natural truffle grounds can be found in a range of altitude between 200-1000m. above sea level, rarely in the valleys or along waterways. They consist of isolated plants or small woodlands with low shrubby vegetation and good sun exposure.
Please note that the mycorrhizal plants with black truffle, unlike those in symbiosis with the white truffle, have some bare areas around the stem, that are called “pianelli” in the Marche region and “burned” or “cave” in Umbria because the fungal mycelium emits a particular toxin that inhibits the germination of seeds. Generally the plant that most commonly gives rise to a mycorrhizal symbiosis with the Tuber Melanosporum is downy oak from the family Quercus pubescens, so much that the area of diffusion of this truffle is related to the one of this tree species. Our symbiotic plants are the holm oak (Quercus ilex), the hazel (Corylus avellana), the hornbeam (Ostrya carpinifolia), turkey oak (Quercus cerris), the durmast (Quercus petrea) and also the common oak (Quercus peduncolata) and the limes (Tilia sp.). On the two main species of truffles, the Tuber Melanosporum Vitt. (Black winter truffle from Norcia and Spoleto) and the Tuber Magnatum Pico (White truffle from Piedmont or Acqualagna) chemical analysis were performed that intended to find out their nutritional values. In particular the University of Perugia analyzed a black truffle that had been harvested in January near Spoleto in the truffle ground Quercus pubescens and a white truffle that had been harvested in November in the area of Città di Castello in the truffle ground Populus nigra. It has been shown that the two species of truffles don’t have many big differences in chemical composition.
From a nutritional point of view truffles are very rich in proteins, because protein is the main nutrient metabolizer. Especially rich in lysine, cysteine and methionine they are easily digestible. Relevant is also the contribution of minerals. The lipid fraction is essentially constituted of unsaturated fatty acids and, among these, the linoleic acid. Also the fiber content is very important.
