A laboratory-scale model cocoa fermentation using dried, unfermented beans and artificial pulp can simulate the microbial and chemical changes of on-farm cocoa fermentation

Abstract

Cocoa fermentation is an essential step for chocolate production whereby flavor potential is generated and bitterness and astringency are moderated. To facilitate fermentation research in laboratories geographically distant from cocoa-growing regions, and to simplify and control the fermentation system, a laboratory fermentation model system was developed. The model system consisted of dried unfermented beans, artificial pulp medium, and laboratory incubator to control temperature and aeration. The model system developed in this study showed a succession of key microorganisms including Saccharomyces cerevisiae, Lactobacillus plantarum, Lactobacillus fermentum, Acetobacter pasteurianus, and Acetobacter tropicalis. The pH of cocoa beans decreased to an acceptable final pH (4.8). Sugars were well consumed and acetic acid and ethanol were produced during fermentation. Desirable volatile compounds including phenylethyl alcohol, acetoin, 2-phenylethyl acetate, and 3-methylbutyl acetate increased in the cocoa beans during fermentation. In addition, the concentration of polyphenols decreased with fermentation. These results lead to the conclusion that the model system developed in this study was able to simulate the microbial and chemical changes occurring in in situ cocoa fermentation. This laboratory-scale model system will enable systematic examination of the effects of process parameters on fermented bean quality.