Microorganism population, theobromine, antioxidant, and FTIR analysis of Samarinda cocoa bean fermented with Saccharomyces cerevisiae and Acetobacter aceti

This research aimed to observe S. cerevisiae and A. aceti induced fermentation of cocoa bean from Samarinda, Indonesia, in comparison to commercial cocoa bean in terms of microbial population, pH, total acids, total phenols, theobromine, antioxidant capacity, and FTIR profile. Cocoa beans were fermented with a boxed fermentation method resembling commercial plantation for four days at ambient box temperature (35-40°C). Four fermentation samples were produced which were spontaneous, 2% Saccharomyces cerevisiae, Acetobacter aceti, or mixed culture (S. cerevisiae and A. aceti) induced fermentations. Total Plate Count (TPC) and Total Yeast-Mold (TYM), pH, total phenol, theobromine, antioxidant activity, and FTIR analyses were performed according to the established method. There was no significant difference in the microbe population in all fermented cocoa. Mixed culture fermented cocoa had a slightly lower final pH. S. cerevisiae fermented cocoa produced the highest total phenol compared to the same compound content in other fermented cocoa. The mixed culture fermented cocoa had better theobromine content 162.3±22.6 ppm, antioxidant capacity 424.9±3.3 ppm, and the closest theobromine and caffeine identification zones to commercial cocoa samples. The use of mixed culture of S. cerevisiae and A. aceti is suggested as the better inoculum to ferment cocoa bean at local farms.