C and H stable isotope ratio analysis using GC-IRMS for vanillin authentication

Vanilla extracts are widely used as flavouring ingredients in foods and beverages and aromatic compounds in perfumes and pharmaceuticals. Due to the high cost of producing high-quality natural extracts from Vanilla planifolia, synthetic or natural identical biosynthetic vanillin (from natural precursors such as guaiacol, ferulic acid, eugenol and lignin) are often used as a substitute [1]. To verify the authenticity of vanilla extracts from Vanilla planifolia, one of the most commonly used methods is stable isotope ratio analysis (SIRA) of 13C/12C (expressed as δ13C), since it has been found that different plants discriminate differently against 13C and differently from the synthetic source. Today this analysis is no longer enough to discover vanillin adulteration, due to the practice of adding 13C to the methylic site of synthetic vanillin [2]. In this study, we combined analysis of 13C/12C with that of 2H/1H (expressed as δ2H) using GCIRMS [3]. 16 authentic samples of Vanilla planifolia, 16 natural identical, 5 synthetic vanillin and 20 commercial extracts were considered. Authentic natural vanillin from Vanilla planifolia and natural identical vanillin are characterised by δ2H values much lower than those of synthetic vanillin. The isotopic values of all the commercial extracts declared to be from Vanilla planifolia (N=20), had δ13C within the typical range for natural vanillin, but δ2H outside the range and more similar to that of synthetic vanillin. The combination of δ13C with δ2H GC-IRMS analysis of vanillin can therefore be proposed as a suitable tool for improving the detection of vanilla extract adulteration