What is Mucilage?
Mucilage is the fruity layer of the coffee cherry that is found between the outer skin and the parchment layer that surrounds the seed. During the wet-processing method, the coffee cherries are pulped to remove the outer skin, leaving behind the mucilage. This layer is sticky and has a high sugar content, making it an ideal environment for fermentation. After pulping, the coffee beans are then placed in fermentation tanks where bacteria and yeast break down the sugars in the mucilage, releasing carbon dioxide and other byproducts. This process can take anywhere from 12 to 48 hours, depending on the desired flavor profile.
Once fermentation is complete, the mucilage is washed off the beans using water. This can be done in several ways, including using channels or tanks to move the beans through water or by using mechanical equipment to scrub the mucilage off the beans. The washed beans are then dried, either in the sun or using mechanical dryers, until the moisture content reaches the desired level for export.
The amount of mucilage left on the bean after pulping can have a significant impact on the final flavor of the coffee. Some producers choose to leave a small amount of mucilage on the beans, a process called "honey processing," to impart a sweeter, fruitier flavor. Others prefer to completely remove the mucilage for a cleaner, brighter cup. Understanding the role of mucilage in the wet-processing method is important for coffee professionals, as it can greatly impact the flavor and quality of the final product.