Fourier transform ion cyclotron resonance mass spectrometrical analysis of raw fermented cocoa beans of Cameroon and Ivory Coast origin

Abstract

Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is an ultra-high resolution mass spectrometry technique used mainly in analysis of unresolved complex mixtures comprising tens of thousands of analytes. For the first time, it was used to analyze samples of raw fermented cocoa beans originating from Cameroon and Ivory Coast. The direct infusion mass spectra of the raw fermented cocoa bean extracts showed 10091 and 10911 peaks, resp., rating cocoa among the most complex organic mixtures ever analyzed. Automated molecular formula calculations could assign 2995 and 2968 of the peaks, resp. to formulae containing only C, H, O, N≤3 and S≤1 atoms. The formulae were separated into four groups depending on their heteroatom content and the intensities of the groups were compared in class plots, showing the highest population in the CHON species, but the highest abundance in the CHO species. Elemental ratios obtained from the molecular formulae were plotted in an intensity coded three-dimensional modification of the van Krevelen diagram. For the CHO species, the van Krevelen diagram showed that most of the intensity belongs to the lipid, polyphenol and carbohydrate regions of the plot. The biggest difference was observed in the CHON group, assigned as peptide degradation products, where the Ivorian beans showed greater variety and molecular diversity and higher total intensity of the nitrogen containing compounds, in accordance with the fact that the Ivorian beans show generally higher nitrogen content than the Cameroon beans. FTICR-MS proves capable not only for high-throughput comparison of major classes of metabolites from cocoa samples from different origins, but also can give insight into the different molecular formulae comprising these compound classes.