Characterization of natural vanilla flavour in foodstuff by HS-SPME and GC-C-IRMS

Vanillin can be obtained by extraction from the pods of Vanilla (organic vanillin), by synthetic pathways using different precursors (mainly lignin and guaiacol), and by enzymatic bioconversion (biovanillin) from natural precursors, (mainly ferulic acid, eugenol and isoeugenol, and turmeric acid). Based on the origins its commercial value greatly changes. At the same time the European Regulation allows to label food discriminating between the sources of the ingredient indicating the term ‘natural’ even if the ingredient is obtained by biosynthetic pathways. However from literature it is apparent that the distinction between synthetic and biosynthetic vanillin is not always possible, while the natural one can be easily discriminated, although rarely used. The method here proposed is based on head-space solid-phase microextraction and gas chromatography coupled to isotope ratio mass spectrometry to determine the carbon isotope ratio (δ13C) of vanillin extracted from vanilla pods, commercial flavoured foodstuff and in vanillin samples of different origins. Isotope fractionation during SPME extraction has been determined based on sample’s isotopic composition. The results confirm the literature ones and allow to reveal which biovanillin can be easily characterized and distinguished from the synthetic ones. In most cases it has been possible to evaluate the origin of vanillin used in the different food preparations.