Ghanaian Cocoa Bean Fermentation Characterized by Spectroscopic and Chromatographic Methods and Chemometrics

Abstract

Export of cocoa beans is of great economic importance in Ghana and several other tropical countries. Raw cocoa has an astringent, unpleasant taste, and flavor, and has to be fermented, dried, and roasted to obtain the characteristic cocoa flavor and taste. In an attempt to obtain a deeper understanding of the changes in the cocoa beans during fermentation and investigate the possibility of future development of objective methods for assessing the degree of fermentation, a novel combination of methods including cut test, colorimetry, fluorescence spectroscopy, NIR spectroscopy, and GC-MS evaluated by chemometric methods was used to examine cocoa beans sampled at different durations of fermentation and samples representing fully fermented and dried beans from all cocoa growing regions of Ghana. Using colorimetry it was found that samples moved towards higher a* and b* values as fermentation progressed. Furthermore, the degree of fermentation could, in general, be well described by the spectroscopic methods used. In addition, it was possible to link analysis of volatile compounds with predictions of fermentation time. Fermented and dried cocoa beans from the Volta and the Western regions clustered separately in the score plots based on colorimetric, fluorescence, NIR, and GC-MS indicating regional differences in the composition of Ghanaian cocoa beans. The study demonstrates the potential of colorimetry and spectroscopic methods as valuable tools for determining the fermentation degree of cocoa beans. Using GC-MS it was possible to demonstrate the formation of several important aroma compounds such 2-phenylethyl acetate, propionic acid, and acetoin and the breakdown of others like diacetyl during fermentation. Practical Application: The present study demonstrates the potential of using colorimetry and spectroscopic methods as objective methods for determining cocoa bean quality along the processing chain. Development of objective methods for determining cocoa bean quality will be of great importance for quality insurance within the fields of cocoa processing and raw material control in chocolate producing companies.

The impact of yeast starter cultures on the microbial communities and volatile compounds in cocoa fermentation and the resulting sensory attributes of chocolate

“…In the chocolates, the alcohols 2-Ethyl-1-hexanol, 2-Heptanol, and 2-Nonanol were identified. Their presence is desirable because they impart sweet, fruity, and floral notes (Aculey et al 2010;Frauendorfer and Schieberle 2008). As observed in the present study, the profile and relative concentrations of volatile compounds varied with yeast inoculation.…”

“…This is probably due to the yeast metabolism during the fermentation process, which produces esters with flower, fruity, and honey flavors (Aculey et al 2010;Frauendorfer and Schieberle 2008). Isoamyl acetate and ethyl acetate were the main esters detected (around 90 % of total esters) after inoculated fermentation; they are related to banana and pineapple flavors, respectively.…”

Impact of fermentation on nitrogenous compounds of cocoa beans (Theobroma cacao L.) from various origins

“…During roasting these nitrogenous compounds with reducing sugars undergo Maillard reactions to develop characteristic cocoa flavor. On the contrary, unfermented cocoa beans were found not generate cocoa flavor upon roasting (Aculey et al, 2010;Kirchhoff, Biehl, & Crone, 1989;Lopez & Dimick, 1995;.…”

Effect of Fermentation and Roasting on the Phenolic Concentration and Antioxidant Activity of Cocoa from Nicaragua

“…These two processes affect the concentration of polyphenols and the antioxidant activity (AA) of the beans (Aculey et al . ).…”