KIGUTHA AA, Aberdare - Kenya
Natural yeast fermentation
Oct - Jan 2021
Worka Chelele station
Sour cherry candy, lime and white sugar
We find the WORKA Cooperative in the village of Chelchele, Ethiopia. It has over 300 member farms that grow outstanding and ethically produced coffees at about 1,900 masl. As a member of the Yirgacheffe Coffee Farmers Cooperative Union (YCFCU) it receive permanently support of best practices to improve the coffee quality and also the commercialisation of the coffee abroad.
Coffee in this region is cultivated between 1,945 and 1,970masl and the station includes 12 standardised fermentation tanks and 360 drying beds. Coffee trees are typically shaded by Cordia and Acacia and the predominant varietals are known locally as Kumie, Diga & Wilsho.
Over a number of years the Yirgacheffe region has developed a distinguished reputation for fine coffees, producing some of the most sought-after microlots in world. The combination of high altitude (up to 2,200m in some areas), fertile soil, consistent and plentiful rains, and an abundance of local knowledge are all contributing factors to the high status of Yirgacheffe coffees. The indigenous ‘heirloom’ varietals - which grow wild in Ethiopia - are responsible for the unique flavour notes which make for an unusual but refined cup. When processed naturally through sun-drying these present as juicy and jammy stone-fruit flavours, floral notes and chocolate with a creamy body.
Shade grown cherries are delivered to the mill for careful sorting, to select only the ripest. The cherries are then fermented in sealed tanks with added yeast cultures, then dried in the sun on raised African beds for up to 21 days. In the daytime they are raked and turned periodically to ensure a consistent drying process. The cherries are covered between 12pm and 3pm to protect them from sun damage and at night time to protect it from rainfall and moisture. Once the coffee has dried to the right level it is milled, graded, sorted and thoroughly handpicked, before being bagged in GrainPro for export from the port of Djibouti.
The word “fermentation” describes the process of metabolization of sugars and other compounds by microorganisms like yeasts and bacteria, which will consume those compounds and convert them into fuel for their own use, leaving behind useful by-products like ethanol and different acids. Those converted compounds are absorbed into the cellular structure of the seed and, when heat is applied to those seeds in the roaster, the compounds will be what transform into the flavours we love in coffee: Complex tastes, fruity acids, and other good, interesting notes.
Once the coffee has been placed in a tank for a fermentation process for more than 96 hours, it is sundried with its mucilage as explained above. On the cup it produces a refined sweetness, acidity, and body and also adding distinguished sensorial notes, like fruits, caramel, chocolate, and others.