Combination of 13 C and 2 H SNIF ‐ NMR isotopic fingerprints of vanillin to control its precursors

Synthetic vanillin is the flavouring most used in agro‐food industries, but more and more frequently consumers are now turning to natural origin. Vanilla planifolia (Andrews) is the most commercialized species of pods in the world and is mainly produced in Madagascar. However, periodically the production of V. planifolia suffers from poor climatic conditions, with the resulting degradation of both the quality and the quantity of the pods. Consequently, the price of vanilla pods rose to record in 2017 and the risk of fraud has increased in response. Analytical methods based on isotopic compositions have already proven their ability to ensure the authenticity of natural vanillin. In 2006, ²H SNIF‐NMR (site‐specific natural isotopic fractionation by nuclear magnetic resonance) was approved as official method by the Association of Official Analytical Chemists (AOAC 2006.05). However, this method is time consuming and the extraction of 1 g is cumbersome for the finished products. The information brought by combined ²H and ¹³C SNIF‐NMR profiles was compared using chemometric tools to determine the best routine tool to improve both the global analysis time and the potential of detection. As a result of this work the ability of the SNIF‐NMR method to verify the authenticity of vanillin has been improved, in particular by providing the first means to discern the geographical origin of vanilla pods. Furthermore, ¹³C NMR using pulse sequences such as INEPT (insensitive nuclei enhanced by polarization transfer) offers the possibility to improve the sensitivity of the analysis, with a reduced quantity of product (less than 50 mg) and a shorter analysis time, which will facilitate the study of the finished matrices as well as clearly discriminating the origins of the vanilla flavourings.