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 which yeast and bacteria will use as fuel for the fermentation.
In the coffee industry, we describe the length of fermentation as being a period of time in which coffee is piled in tanks or held underwater, with the goal of either accelerating or retarding fermentation, typically this could take anywhere between 12 and 48 hours. In Kenya, it is common to see a double fermentation washed process, the beans are soaked for a second period which demands more water usage, but produces an incredibly clean cup.
When fermentation is complete the mucilage will be fully removed, and the beans will feel rough to the touch rather than slimy. This means they are ready for another quick rinse, then the drying stage.
Drying is usually done on large concrete patios in the sun, under canopies, on raised beds or mechanically. It is widely accepted that a slower drying time contributes to greater balance and complexity in the cup.
Once dried to about 10-12% moisture content, the coffee still needs to be separated from its protective parchment with a de-hulling machine. The parchment is cracked, allowing the green coffee inside to be released. This green coffee is then packaged up for grading and export.
This process is the primary method for preparing specialty-quality coffee in most of Africa, Central and South America (with the exception of Brazil, where it’s uncommon).
Washed processing typically translates to clean and refined flavours with crisp, sparkling acidity. This is a resource-intensive process, which is often makes it too expensive for some farmers or cooperatives to consider.
If you’re interesting in trying a washed processed coffee go check out our brand new Colombian: Paraiso Enigma
Check out our partners Cafe Imports video shoot on location below…