How coffee is processed after harvesting has an important influence on the flavour of the roasted beans. Here's a quick guide to each process:
Washed: The coffee cherry is brought to the wet mill where it is de-pulped (removal of outermost fruit skin). The coffee is then fermented in a tank for 12-36 hours after which they are washed with clean water and lightly scrubbed to remove any residual mucilage. The beans are then placed on patios or elevated screens to dry. The papery parchment skin surrounding the beans remains but during hulling this is also removed. Coffees processed in this way highlight the intrinsic organic acids that give these coffees a bright and refreshing taste.
Semi-washed: (also known as the pulped natural method) This process entails the removal of the skin followed by de-pulping after which the beans are left to dry without any intermediate wet fermentation stage. The sticky sweet inner layer of mucilage clings to the beans and imbues them with sweetness and fruit notes. Beans processed in this way tend to have a reduced acidity that can emphasise other flavour characteristics that may be masked when acids are dominant.
Honey Process: This is a refined version of the pulped natural process with the main difference being that more fruit is allowed to remain on the shell of the coffee seed. During drying the interaction between the seed and the fruit is continuously evaluated.
Natural: Natural processed coffee allows the fruit to dry around the bean until the cherry becomes hard after which the bean is hulled from the dry fruit either by hand or mechanically. Naturally processed coffees emphasise fruity flavours and tend to be heavy in body, sweet and smooth. However, unless carefully controlled during harvesting, underripe cherries, which are impossible to sort from the ripe ones once they are dried, can lead to very mixed cup profiles from coffees processed using this method.