Processing the Cherries

Once the coffee has been picked, processing must begin as quickly as possible to prevent fruit spoilage. Depending on location and local resources, coffee is processed in one of two ways:

The Dry Method is the age-old method of processing coffee, and still used in many countries where water resources are limited. The freshly picked cherries are simply spread out on huge surfaces to dry in the sun. In order to prevent the cherries from spoiling, they are raked and turned throughout the day, then covered at night or during rain to prevent them from getting wet. Depending on the weather, this process might continue for several weeks for each batch of coffee until the moisture content of the cherries drops to 11%.

The Wet Method removes the pulp from the coffee cherry after harvesting so the bean is dried with only the parchment skin left on. First, the freshly harvested cherries are passed through a pulping machine to separate the skin and pulp from the bean.  

Then the beans are separated by weight as they pass through water channels. The lighter beans float to the top, while the heavier ripe beans sink to the bottom. They are passed through a series of rotating drums which separate them by size.

After separation, the beans are transported to large, water-filled fermentation tanks. Depending on a combination of factors — such as the condition of the beans, the climate and the altitude — they will remain in these tanks for anywhere from 12 to 48 hours to remove the slick layer of mucilage (called the parenchyma) that is still attached to the parchment. While resting in the tanks, naturally occurring enzymes will cause this layer to dissolve. 

When fermentation is complete, the beans feel rough to the touch.  The beans are rinsed by going through additional water channels, and are ready for drying.