Modulation of the 13C/12C ratio of vanillin from vanilla beans during curing

Abstract

ABSTRACTAuthenticity of vanilla extracts can be monitored by, for example, analysis of marker compounds and analysis of stable isotope ratios of vanillin using site‐specific natural isotopic fractionation by nuclear magnetic resonance or isotopic ratio mass spectrometry (IRMS) techniques. In order to improve vanilla bean quality curing technologies were proposed using enzymatic or microbiological processes. However, the influence of process parameters on the 13C/12C ratio of vanillin from vanilla beans was not known. An isotopic shift of vanillin was found in the early stages of traditional vanilla bean curing. In model experiments using acid hydrolysis a δ13CV‐PDB value (where V‐PDB represents the standard Vienna‐Pee Dee Belemnite) of vanillin of −21.5‰ was obtained. In vanilla extracts prepared by an enzymatic curing process δ13CV‐PDB values for vanillin of −21.6 to −22.2‰ were found. These values are significantly more negative than those of vanilla extracts from traditional curing. Data suggest that the less negative δ13CV‐PDB values in traditional extracts are the result of an isotope discriminating degradation of vanillin in the traditional process. The 13C/12C ratios found for some vanilla beans and extracts prepared thereof were outside the reference data set used for authenticity control by IRMS. Because of the implication on vanilla authenticity judgment – although the δ13CV‐PDB data were measured by two independent methods – it is desirable that the experiments are repeated to confirm the results. Copyright © 2012 John Wiley & Sons, Ltd.