From Nontargeted to Targeted Analysis: Feature Selection in the Differentiation of Truffle Species (Tuber spp.) Using 1H NMR Spectroscopy and Support Vector Machine

Italian White Truffle (Tuber magnatum Pico): Discovery of new molecules through untargeted UHPLC-QTOF-MS analysis

The Italian white truffle (Tuber magnatum Pico) is worldwide recognized as one of the most expensive edible mushrooms. Its chemical characterization has not yet been properly investigated in scientific literature. The aim of this study was to explore, for the first time, the truffle polar metabolic profile using an untargeted approach through UHPLC-ESI-QTOF-MS data-dependent acquisition. The total features list was filtered and molecules were annotated according to the MS spectra correspondence score with a threshold of 60 %. This led to a total of 412 annotated compounds mainly referred to amino acids, B-vitamins, carbohydrates and fatty acids derivatives. A targeted analysis was applied to four annotated molecules never detected in truffle before, being riboflavin, azelaic, 2-isopropylmalic and 3-isopropylmalic acids. Some constituents of the extracts were semi-quantitatively analysed by 1H NMR spectroscopy. Results place a first brick in white truffle characterization, paving the way towards authenticity biomarkers detection useful in frauds prevention.

Identification of Bis(methylsulfanyl)methane and Furan-2(5H)-one as Volatile Marker Compounds for the Differentiation of the White Truffle Species Tuber magnatum and Tuber borchii

Some truffles are expensive and, therefore, are prone to food fraud. A particular problem is the differentiation of high-priced Tuber magnatum truffles from cheaper Tuber borchii truffles, both of which are white truffles with similar morphological characteristics. Using an untargeted approach, the volatiles isolated from samples of both species were screened for potential marker compounds by comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC×GC-TOFMS) and statistical analysis of the obtained semiquantitative data. Results suggested bis(methylsulfanyl)methane and furan-2(5H)-one as compounds characterizing T. magnatum and T. borchii, respectively. Exact quantitation of both volatiles by conventional one-dimensional gas chromatography-mass spectrometry in combination with stable isotopologues of the target compounds as internal standards confirmed both as marker compounds. The method is suitable to be used in the routine analysis for the objective species differentiation of T. magnatum and T. borchii.