Imagine walking in an autumn forest, with the humid air smelling of earth and leaves. Under your feet, a few centimeters above the ground, lies a treasure that shines not with gold, but with aroma: the truffle. Hidden deep in the ground, truffles blend with the roots of trees such as oaks or poplars, exchanging water, minerals and organic compounds with them. Incapable of spreading their spores with the wind, because they grow underground, truffles have found a different strategy to reproduce: spreading a perfume capable of attracting animals, which dig in the earth to find them, thanks to that complex and earthy scent that comes from organic molecules and sulfur compounds. The perception of this aroma is subjective: for some, these molecules smell of gas and “stink”, while for others they are a pleasant scent. Inside the rough rind – the peridium – he hides there glebethat is, the pulp that holds the spores and can reveal the age and species of the truffle. Some truffles have a light peridium, others dark: an example of this is respectively Tuber magnatumthe prized white of Alba and the Tuber aestivumknown as scorzone.
How truffles are made and their secret symbiosis
The truffles widespread in Europe almost all belong to this genus Tuberand they are underground mushroomsthat is, they live and develop underground. They are not isolated organisms, but they form groups symbiotic relationships with the surrounding trees, such as poplars, beeches, pines, oaks, hazels, alders and limes. The hyphae (thin filaments of the fungus that branch out into the ground) intertwine with the roots of the tree, forming a complex structure called mycorrhiza. From this collaboration, both benefit: the truffle provides water and mineral salts to the plant, the tree “repays” with sugars and other organic substances. It is a perfect natural cooperation, active underground and invisible to our eyes.
What we commonly call “truffle” is actually it sporophore of the mushroom, i.e. the fruitful part responsible for the production and dissemination of spores.
It is made up of two main portions:
- The peridiumthat is, the external covering;
- There glebeor the internal pulp, protected by the peridium.
The gleba is what we see once the truffle has been cut, with characteristic veins that give it an appearance marble: inside there are two types of striations, the sterile veinswhich do not produce spores, often clear; and the fertile veinsdarker, which contain the aschi, the capsules containing the spores. The color of the serf and the appearance – for example whether it has lighter or darker areas, evident veins – are useful indicators for determining the species of truffle and its state of ripeness. The gleba is often lighter in young truffles, but gradually darkens as the spores mature, until it shows the characteristic color of each species.
Why truffles “stink”: the cause of the gas smell
Truffles they cannot disperse the spores with the windas common mushrooms do. They then developed another strategy: the perfume. The aromatic molecules of truffles are irresistible to many insects and animals – often mammals such as wild boars, foxes and wolves – which dig to eat them. The spores then pass through the digestive system and are expelled elsewhere, ready to germinate. Examples of these volatile compounds (i.e. those that are easily dispersed in the air) are derivatives of butanalan organic molecule made up of four carbon atoms which belongs to the category of aldehydes. Other molecules are sulfur compoundslike the dimethyl sulfide (DMS) and the dimethyl disulfide (DMDS), particularly known for their intense and characteristic odor.
The types of white and black truffles in Italy
Species that have a lighter colored peridium (such as whitish, beige, yellow-ochre) and often smoother are commonly called “white”. Species with a dark peridium (from brown to black) – often with a rougher surface – are called “black”. Be careful though: the distinction between “white truffles” and “black truffles” does not have a rigorous taxonomic value, and within these two groups there are numerous varietieseach with its own morphological and organoleptic characteristics.
In Italy, among the varieties of white truffle the T. magnatumvery widespread in the Alba area, in Piedmont, among the most valuable and expensive, so much so that at the beginning of the 2000s it had reached the price of almost €8000 per Kg. The value of this truffle does not depend only on its intense and unmistakable aroma, but also on other factors such as the need for an extremely specific habitat, which does not allow it to grow everywhere. Next to the “king” of white truffles there is also his “cousin”, the T. borchiialso called “whitewash“, that is more widespread and easily cultivatedand therefore less refined.
Moving on to black truffles, we have the T. melanosporum, also known as “precious black truffle”, with a brilliant black color which can also take on brown/reddish shades especially between the veins. It is a very prized truffle with an aromatic and intense smell. The one we know as scorzone, is the T. aestivumwidespread not only in Italy but also in much of Europe, less valuable, but widely used in cooking, thanks to its characteristic aroma reminiscent of toasted malt.
