Determination of Trace Elements in Cacao Nibs and Cacao Mass by X-Ray Fluorescence Analysis and Its Application to Identification of Their Production Areas

Abstract

Trace elemental analysis of chocolate ingredient (cacao nibs and cacao mass) was performed using X-ray fluorescence (XRF) analysis in order to characterize the geographical origins of the cacao beans. By using an energy-dispersive XRF spectrometer equipped with three-dimensional polarization optics and employing three secondary targets (Ti, Ge, and Mo), determination of trace elements at the sub-ppm level in cacao bean samples was accomplished. For example, the Lower Limit of Detection (LLD) of bromine was calculated to 0.40 mg/kg and 12 elements (P, S, K, Ca, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr) were detected for cacao samples. Cacao nibs and cacao mass samples from 10 different geographical area covering Africa, Asia Pacific, Central and South America were analyzed. Results showed that there were some difference between the trace element contents, reflecting a difference in their geographical origins. A statistical analysis showed that the concentration of seven elements (Mn, Fe, Ni, Cu, Zn, Rb, Sr) are good parameters for constructing a discriminant function of geographical origin. The present work demonstrates that XRF is useful as a rapid and simple tool for provenance analyses of agricultural products.