The pods are discarded on site, and the beans and pulp are brought back from the field for fermentation. Small farms often ferment cacao in piles, covered with banana leaves. Larger operations often use wood or cement boxes. Fermenting cacao is the first step in producing chocolate’s complex flavor, and the chemistry of the fermentation process is as complex as the chocolate itself. The actual fermentation has little to do with cocoa beans, which are shielded from bacteria by their shells. The yeast and bacteria actually feed off the sugars in the white, gooey pulp, turning them into alcohols and acidic compounds. Some of these fermentation byproducts can pass through the shell into the bean, contributing to it’s bitter taste. Another factor in developing the bean’s flavor is the heat generated by fermentation—usually around 130°F—which kills the bean and encourages enzymes that convert some of the bean’s fat into sugars. Fermentation is one of the most important determinants of a bean’s flavor.
Fermentation can take anywhere from three days to a full week. Too long, and the beans will rot. Too short, and they don’t develop much flavor. That doesn’t stop some growers from skipping the step entirely, especially those that sell to industrial chocolate makers like Hershey and Nestlé, whose formulas are tailored to deliver consistent chocolate regardless of the beans’ quality.