Microbial fermentation is also an anaerobic process in which organic foods are broken down into simpler compounds and chemical energy without the presence of oxygen for at least part of the process or not at all. Chemist Louis Pasteur described fermentation as "respiration without air. " This process takes place on the farms where the cacao beans are grown. Fermentation can be done in several ways. .
However, all fermenting methods depend on removing the beans from the pods by splitting them with machetes, hammers or by hitting the pod against a tree, exposing a white, sugary pulp. Each pod encases approximately forty cacao beans. The beans are then piled together and covered. West African cacao farmers use banana leaves to cover the beans. This method does not produce consistent results. Cacao plantation farmers in the West Indies, Malaysia and Latin America construct large, shallow, wooden boxes with holes or slatted bottoms for drainage. This method results in optimum fermentation. Drosophila melanogaster, commonly known as fruit or vinegar-flies, transfer microorganisms to the beans. This initiates fermentation of the pectinaceous pulp surrounding the beans by allowing microorganisms to develop, a process similar to composting. .
Yeasts of the Saccharomyces cerevisiae species begin to grow and convert the sugars that surround the pulp to ethanol. Bacteria then starts to grow. The bacteria oxidizes the ethanol to acetic acid and then to carbon dioxide and water. This process produces heat which raises the temperature in the covered heap of beans. At this time, the chemical composition of the bean begins to change. The plant enzymes hydrolyze the sucrose into glucose and fructose. The pulp starts to break down and drain off within twenty four hours of the start of this process. This is known as sweating. The covered heap of sticky pulp becomes a cloudy, dark, dense broth in which the cacao seeds begin to absorb flavors.
