Use of the 13C/12C, 15N/14N and 18O/16O Isotopic Ratios of Theobromine and Caffeine in the Characterization of Geographic Origin

Abstract

The aim of this work is to characterize the geographical origin of cocoa beans and coffee beans. This study aims to contribute to the traceability of raw materials in order to fight against falsification. For this purpose, we based our work on the measurement of isotope ratios in 13C, 15N and 18O. The multi-element isotope ratios have been evaluated as a means to distinguish fermented cocoa beans of different geographic and varietal origins. The isotopic ratios of 13C, 15N and 18O were measured in theobromine obtained from samples of fermented cocoa beans. Twenty-two (22) samples of different geographical origins covering the four mainland cocoa producing areas were analyzed on the one hand and on the other hand, 16 caffeine samples from various origins were also analyzed. The treatment of the values resulting from these isotopic analyzes by statistical methods, namely the principal component analysis (PCA) makes it possible to visualize the discriminations between the different origins. The most discriminating variables identified as responsible for the geographic and varietal differences were the δ15N, δ13C and δ18O values of cocoa beans and certain extracts and tissues. We have shown that the isotope ratios are correlated with the altitude and precipitation conditions encountered in the different cocoa growing regions.