Detection of Sophisticated Adulterations of Natural Vanilla Flavors and Extracts:  Application of the SNIF-NMR Method to Vanillin and p-Hydroxybenzaldehyde

Abstract

This paper describes recent progress in the isotopic analysis of the two main aromatic constituents of vanilla flavor (vanillin and p-hydroxybenzaldehyde (pHB)). Some improvements concerning the SNIF-NMR analysis of vanillin are presented. They include (i) improvement of the analytical precision by using new software for automatic phasing, baseline correction and curve fitting of the signals of the 2H-NMR spectra; (ii) significant enrichment of the database containing measurements performed on vanillin extracted from vanilla beans harvested in different countries and on synthetic vanillin; (iii) standardization of the purification process to obtain pure vanillin, in order to avoid isotopic fractionation; and (iv) improvement of the statistical tools for both proving and quantifying adulterations. All these improvements were also successfully applied to site specific deuterium NMR analysis of pHB. It is now also possible with the SNIF-NMR method to discriminate between the natural and chemical origins of pHB. New results concerning the δ13C deviation of pHB are also presented. Thus the lowest value of δ13C of pHB extracted from vanilla bean can be set at −19.5‰. We recommend the methodology presented in this paper as a standard procedure for purifying vanillin and pHB, without significant isotopic fractionation, from most matrices (for example from ice cream, yogurts, etc.), in order to perform isotopic analyses (13C IRMS and 2H-NMR). Keywords: SNIF-NMR; vanillin; pHB; δ13C; adulteration; vanilla flavor; vanilla extract; ice cream; purification

Fast single run of vanilla fingerprint markers on microfluidic‐electrochemistry chip for confirmation of common frauds

“…In addition, the natural origin of the vanilla samples can also be checked by comparison with the ratios between the vanilla markers [17,18,22]. The ratio obtained for the prominent markers (VAN/PHB) was in agreement with the bibliographic values (10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), as well as (VAN/VANA) (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29), while on the contrary, (VAN/PHBA) ratio was not in agreement with the bibliographic values (53-110) [26]. This kind of anomaly has also been documented for natural vanilla extracts [18].…”

“…The replacement of VAN with EVA inevitably results in the use of the flavoring in artificial products because the presence of this compound is a unambiguous evidence of their non-natural origin. However, the presence of VAN in vanilla-related samples is not unequivocal proof of their authenticity because adulteration of vanilla extracts with synthetic VAN (lignin-derived) is a major problem in commercial products [18][19][20][21]. As a consequence, the high demands and the high price of authentic vanilla extracts leads to numerous attempts to blend and adulterate samples and their authenticity must be verified by MS or by multianalyte detection in vanilla extract profiles using GC and HPLC [22][23][24][25].…”

Position-specific hydrogen isotope equilibrium in propane

“…This subject grew dramatically with the development of NMR techniques for measuring position-specific variations in D and 13 C abundances in organic molecules (Martin and Martin, 1981;Caytan et al, 2007). Such work has been applied to foodscience, plant physiology, paleoenvironment reconstruction and environmental contamination (Remaud et al, 1997;Gilbert et al, 2012;Ehler et al, 2015;Julien et al, 2015 and2016). Intramolecular isotopic fractionations can reflect temperatures of molecular synthesis, mechanisms of formation, and/or source substrates (Martin et al, 2008;Eiler, 2013b).…”

Comparison of extraction techniques and modeling of accelerated solvent extraction for the authentication of natural vanilla flavors

“…(iii) Distribution of the deuterium atoms within the vanillin structure by site-specific natural isotope fractionation-NMR (SNIF-NMR) [18,19]. This technique was recently proposed as an AOAC official method [20] and applied to 13 C determinations [21,22].…”