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By: Alex 15 April 2015
So, after a lengthy break due to a disastrous ski holiday (resulting in a broken leg!), it is finally time for the last instalment of ‘Coffee Processing Explained’!
This concluding post covers off the washed process – this is arguably our favourite coffee process at North Star due to the incredibly clean and bright coffees it produces.
The washed process is widely used across Latin America and parts of East Africa and requires both the cherry and mucilage surrounding the parchment to be removed with the use of friction, fermentation and water.
Once the ripe cherries have been picked, they are delivered to a wet mill where they are loaded into a depulping machine which forces the beans out of the cherry. At this stage, the beans are contained within the pulp of the cherry, also known as the mucilage. This sticky mucilage is composed of natural sugars and alcohols and contributes massively to the sweetness, acidity and overall flavour profile of the coffee.
Once the beans have been pulped, they are put into fermentation tanks for around 24 hours dependent on temperature, though farmers are now experimenting with fermentation time to develop different flavour profiles. For example, a longer fermentation means the beans have more time to absorb some of the sugars and can result in a slightly sweeter, ‘funkier’ flavour.
Fermentation results in the mucilage being broken down leaving the beans in their parchment which are then ready to be washed. This can either happen in tanks of clean water or, in East Africa, it is often done in channels. Once the beans have been washed they will feel gritty in your hands which means they are now ready to be dried. At this stage, the parchment beans are taken to drying tables (raised African beds) or to patios to sit for a period of around 10-12 days, before finally reaching the dry mill to be hulled and sorted ready for export.
Coffees from Kenya are perhaps the best example of truly outstanding washed coffees – following fermentation, Kenyan beans are left to soak in tanks of clean water for a period of up to 72 hours which really helps to build up the amino acids existent within the bean, contributing hugely to the incredible citrus acidity found in the cup profile. We should be seeing new crop Kenya coming into the roastery within the next two weeks and look forward to updating the webshop soon!
If you have any questions about anything covered in this series of blog posts then please feel free to drop us a line or give us a call on the contact details provided.