As the pulp breaks down and drains away bacteria continue to be active until fermentation is complete. The yeasts found during cocoa fermentation come from the surrounding environment eg soil, trees etc. Research by Hansen and Welty shows that yeasts multiply very rapidly during fermentation and are able to survive drying and storage. After fermentation the cocoa beans are dried. During the subsequent processing of the cocoa beans the beans are cleaned and can then undergo a form of thermal pre-treatment to separate the shell from the bean.
Water accumulates on the surface of the bean and bursts the shell.
The high surface temperature induced by this process brings about a drop in the amount of microbiological contamination, especially yeast and other fungi. The beans are then separated from the shells and roasted. Following roasting the beans are turned into cocoa mass by grinding. The quality of the cocoa mass is important due to the natural variability which exists in cocoa. Food and Agriculture Organization, 1963.