A picture of black truffles last week in Mercabarna (main wholesale market in Barcelona). They are not yet very mature and therefore its flavor is not as intense.
The distinctive aroma of truffles is what makes them special. The most important Volatile Organic Compounds (VOCs) are those from the metabolism of sulfur.
Since the truffle genome was published, lots of papers have been trying to elucidate what proteins are responsible for producing its peculiar flavor [i]. And they have already identified 126 genes related to sulfur emissions. When I read these articles, several questions come to my mind:
Can we completely imitate the flavor of truffles artificially?
Some researches seek to mimic the aroma of truffles through mycelial fermentations. In a work of 2012 [ii], they manage to extract up to 59 VOCs in a fermentation of T. melanosporum and conclude that these compounds are very similar to those produced by the fruiting body, especially favored by the presence of sucrose in the medium.
We know that truffles from different origin have different aroma. Is this change in the aroma influenced by just soil characteristics?
VOCs are not just produced by truffles, but some depend on bacteria and yeasts that live in the soil around those truffles. This is probably why the truffle aroma varies depending on where it has been harvested or their stage of development. In fact, pure cultures of yeasts isolated from fruiting bodies of T. melanosporum and T. magnatum produce the characteristic VOCs of each truffle [iii]. Furthermore, when pure truffle mycelia is cultivated (and thus free of bacteria and related yeasts) and VOCs emitted are analyzed, some compounds that are usually present in the fruit body, are now absent [iv].
Maybe is not too far away the time when we’ll be able to change the aroma of a truffle by inoculating certain bacteria or yeast to the ground (probiotics), or by chemical changes through the addition of certain products in the truffiere. Although personally, I would not like this point to be reached, so do not miss that magic that still each terroir can create to some truffles.
Marcos S. Morcillo
[i] Mohammad Tawhidul Islam et al. 2013. Unlocking the Puzzling Biology of the Black Périgord Truffle Tuber melanosporum. J. Proteome Res. 12 (12), pp. 5349–5356; doi: 10.1021/pr400650c
[ii] Li, Y. Y.; Wang, G.; Li, H. M.; Zhong, J. J.; Tang, Y. J. Volatile organic compounds from a Tuber melanosporum fermentation system. Food Chem. 2012, 135 (4), 2628−37.
[iii] Buzzini P, Gasparetti C, Turchetti B, Cramarossa MR, Vaughan-Martini A, Martini A, Pagnoni UM, Forti L (2005) production of volatile organic compounds (VOCs) by yeasts isolated from the ascocarps of black (Tuber melanosporum Vitt) and white (Tuber magnatum Pico) truffles. Arch Microbiol 184:187-193. doi:10.1007/s00203-005-0043-y
[iv] Splivallo R, Bossi S, maffei M, Bonfante P (2007) Discrimination of truffle fruiting body versus mycelial aromas by stir bar sorptive extraction. Phytochemistry 8:2584-2598. doi:10.1016/j.phytochem.2007.03.030