Effects of Freeze‐Drying Treatment on the Aromatic Profile of Tuber spp. Truffles

The influence of lyophilization on the aromatic profile of two different truffles from Spain (Tuber melanosporum and Tuber aestivum) and a cultivated truffle (Tuber indicum) was evaluated by means of the headspace analysis. The volatile compounds were separated by gas chromatography and identified by mass spectrometry. The truffle aroma contained the characteristic compounds, such as 2-methyl-1-propanol, 2-methyl-1-butanol and dimethyl sulfide. Lyophilization and the subsequent rehydration of the truffles did not affect significantly the aroma profile of T. melanosporum; however, the volatile contents of T. indicum were slightly modified and those of T. aestivum changed after the treatment, in terms of reducing the 2-butanol and 2-butanone percentages and increasing the 2-methylpropanal, 2-methylbutanal and 3-methylbutanal concentrations. From this study, we can conclude that truffle aromatic profile of the species T. melanosporum and T. indicum is mainly maintained after lyophilization whereas T. aestivum profile is substantially modified. Practical Applications Truffles are products with limited shelf life and their sensory properties are rapidly lost so that these fungi become a less valuable product in a few days. Losses of volatile compounds, oxidation and enzymatic reactions are a considerable problem during their storage. Several techniques have been used to preserve their sensory properties; however, the aroma profile is commonly modified as a result of high temperature processes or enzymatic reactions. This article describes the use of freeze-drying as a form of processing technique for truffles (Tuber melanosporum, Tuber aestivum and Tuber indicum) to be stored. The use of lyophilization avoids the loss and degradation of volatile compounds because the process is performed at low temperatures. The results showed that the truffle aromatic profile of the species T. melanosporum and T. indicum was mainly maintained after lyophilization, whereas T. aestivum profile was substantially modified.