Chemical signatures from UPLC/MS for cocoa provenance determination

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Abstract

The production of chocolate products is a global industry that needs a method to determine the geographic origins of its most essential component, cocoa. Traceability of cocoa is becoming more important for quality control in the chocolate industry, so that consumers can know they are purchasing products that adhere to fair-trade regulations, organic farming practices, etc. Many of the steps in the process of producing cocoa can influence the chemical makeup of the different aspects of the final product including the flavor profile and aroma. Each region where cocoa is gown has variations in soil composition, weather and farming practices that influence the cocoa bean development. Additionally, differences in post-harvest treatments including fermentation and roasting conditions influence the overall chemical composition of the resulting cocoa liquor used to make finished chocolate products. These differences result in unique chemical signatures that can identify cocoa liquors by their country of origin. Many studies have employed GC/MS, ICP/MS, and HPLC to quantify and detect the presence of certain classes of compounds in cocoa, but there are fewer studies focused on provenance determination via chemical signatures.

Previous work by this group has been able to accurately determine the country of origin of cocoa samples using ICP/MS to construct a unique elemental profile for each country. Use of LC/MS provides an opportunity to evaluate a wide variety of molecules for generating chemical signatures. The cocoa sample preparation and conditions for UPLC/ESI-TOFMS used to obtain unique chemical signatures from cocoa liquor samples are described. Several classes of compounds were identified from the mass spectral data, and the semi-quantitative analysis method was verified with a cocoa standard reference material. Discriminate analysis was used to identify cocoa liquor samples from five different countries. The method was able to accurately group and identify country of origin in 95% of samples. Future directions include moving beyond country level provenance determination, to regional discrimination within countries, and potentially differences in signatures due to genetic strains of cacao.