Determining the Geographical Origin of Cocoa Beans in Chocolate using Stable Isotope Ratios

Sustainability of cocoa bean farms is becoming an increasingly important matter. With more chocolate showing more sustainability labels, there needs to be confidence in the consumer's mind on these labels. One way in which to build this confidence is to ensure traceability of the cocoa bean from farm to the final chocolate product. The stable isotope ratio of cocoa bean samples were measured using IRMS to see if their isotope ratio profile reflects their country of origin. δ2H, δ13C and δ15N were all measured on the bulk unshelled cocoa bean, along with δ2H and δ13C of the three most abundant fatty acids within cocoa beans; Palmitic acid, Stearic acid and Oleic acid. The results were analysed using PCA and showed that the samples tended to split into two groups. Nicaragua, Ghana and Vietnam and Papua New Guinea, The Solomon Islands and Samoa. Two chocolate samples were made from cocoa beans which originated from Ghana. The δ13C and δ2H of extracted fatty acids were analysed as their methyl esters (FAMEs) and compared to the results of the cocoa bean fatty acids. These results showed that the chocolate samples had isotope ratio values closer to that of Vietnam than Ghana. However, the samples from Ghana were also found to be close to those of Vietnam. As an investigative study, this study showed that the method of FAME isotope ratios could potentially be used in future to determine origin of cocoa beans. With some more samples and research, this could lead to the possibility of using it on cocoa beans within a mixture to determine origin. This study also investigated the gas chromatography stable isotope analysis of underivatized fatty acids extracted from cocoa beans samples. This method is a way to analyse the fatty acids without the need to conduct mass balance calculations needed for FAME analysis. Although the chromatographic responses were found to be much lower than that of the FAME, results seen from one chromatographic peak showed similar trends observed for the δ13C in bulk and FAME analyses. Thereby indicating the potential for this technique to be in traceability studies