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Coffee Fundamentals: Coffee Processing

Coffee processing involves removing the outer cherry from the inner seed of the coffee in preparation to export the beans. Here we will discuss the two most common processing methods, the washed and natural processes. Keep in mind that this outlines the standard practice but coffee producers around the world have endless variations that add a local character to their coffee.

Natural (or Dry) Process

Natural processing is the oldest processing method and is most popular in countries that do not have abundant water. While simpler than the washed process it is often more difficult to ensure a consistently great coffee. The natural process involves simply laying out the harvested cherry to dry in the sun on a tarp, cement patio or raised drying bed. The cherries remain for a matter of weeks depending on weather until the cherry dries out to its optimal moisture content. Throughout the drying time the cherries are raked to ensure even drying. This process concentrates the sugars from the outer cherry onto the inner coffee bean resulting in a heavier body and fruit flavors. Following the drying period the coffee cherries are brought to a mill to separate the dried cherry from the bean.


Raised Drying Beds

Washed (or Wet) Process

While the natural process dries the cherry on the bean, the washed process removes the outer cherry prior to drying. This process originated because of the need to process coffee while prohibiting mold growth in countries with wet and humid climates. The first step is to remove the skin and pulp from the bean with a pulping machine. Next a series of water channels are used to separate the beans based on weight. Then the beans are moved to a water fermentation tank where the beans will stay for 12-72 hours. Here naturally occurring enzymes will help to remove the slick mucilage layer that is still on the bean. Finally, the beans are rinsed and moved to another location for drying and milling. The washed process is the more consistent process and is known for a more acidic flavor profile than other processing methods. Many people will consider this their normal cup of coffee.


Fermentation tanks and washing channels at the Kinini washing station in Rwanda