IF Okonkwo* and CQ Igwilo
Department of Applied Microbiology and Brewing, Nnamdi Azikiwe University, Awka, Anambra State, Nigeria
*Corresponding author: If.okonkwo@unizik.edu.ng
The importance of cocoa in the beverage industry cannot be over-emphasized, and its fermentation by microorganisms gives rise to better yield. Natural fermentation and controlled fermentation of the cocoa bean with Lactobacillus plantarum, Saccharomyces cerevisiae, and Acetobacter pasteurianus were carried out, and the physiological characterization of the dominant species was determined. The dynamics in microbial population and time course were examined by the microbial count method. The physicochemical properties of natural and controlled fermented cocoa beans and the metabolite production were determined by titration. We figured out the chemical contents of naturally fermented and controlled fermented cocoa beans through proximate analysis. The physiological characterization of the dominant isolates showed that Saccharomyces cerevisiae grew at 25 and 35°C and pH 2.5, 3.5, and 5, as well as ethanol concentrations of 5, 10, and 15%. Also, Lactobacillus plantarum grew at 25, 35, and 45°C, pH of 3.5 and 5, and ethanol concentration of 5 and 10, but not at 15%. We recorded a luxuriant growth at 25 and 35°C for Acetobacter pasteurianus, pH 5.0 and 3.5, and ethanol 5 and 10%. The dynamics in microbial composition showed that the Yeast population, LAB and AAB populations increased slowly and reached a maximum of 6.1x107, 4.4x107, and 5.4x107 cfu, respectively, at days 3-4 for the natural fermentation, while they increased abruptly and reached a maximum of 7.2x107, 6.0x107, and 6.1x107 cfu, respectively at day 2-3 for the controlled fermentation. The controlled fermentation of the cocoa mass led to the highest temperature and pH after 72h of fermentation. There was faster sugar depletion in the controlled fermented beans than in the naturally fermented beans, which led to higher metabolite content in the controlled fermentation than in the natural fermentation. Thus, the fermentation of cocoa beans with starter addition produced fermented beans with higher chemical quality and reduction in the time of fermentation to 3 days, compared to 6-7 days obtainable during natural fermentation.