Multidimensional Gas Chromatography Coupled to Combustion-Isotope Ratio Mass Spectrometry/Quadrupole MS with a Low-Bleed Ionic Liquid Secondary Column for the Authentication of Truffles and Products Containing Truffle

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Abstract
Truffles are among the most expensive foods available in the market, usually used as flavouring additives for their distinctive aroma. The most valuable species is Tuber magnatum Pico, better known as “Alba white truffle”, in which bis(methylthio)methane is the key aroma compound. Given the high economical value of genuine white truffles, analytical approaches are required, able to discriminate between natural or synthetic truffle aroma. Gas chromatography coupled to combustion-isotope ratio mass spectrometry (GC-C-IRMS), exploiting the 13C/12C ratio abundance of the key flavourings compounds in foods, has been a recognized technique for authenticity and traceability purposes, however a number of issues have greatly limited its widespread use, so far. In the present research, a high-efficiency HS-SPME MDGC-C-IRMS with simultaneous quadrupole MS detection, has been applied for the evaluation of bis(methylthio)methane, resolving the coelution occurring with other components. With the aim to minimize the effect of column bleeding on δ13C measurement, a medium polarity ionic liquid-based stationary phase was preferred to a polyethylene glycol one, as secondary column. Twenty-four genuine white truffles harvested in Italy were analysed, attaining δ13C values between -42.63‰ and -33.89‰, with a maximum standard deviation lower then 0.7‰. Two commercial intact truffles and 14 commercial samples of pasta, sauce, olive oil, cream, honey and fresh cheese flavoured with truffle aroma were analysed, and the results from δ13C measurement were evaluated in comparison with those of genuine “white truffle” range and commercial synthetic bis(methylthio)methane standard.

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