The True Purpose of Fermentation

As our new Kenyan coffee selection approaches Barcelona, we want to open a discussion about a topic that continues to spark debate within the coffee industry: fermentation. In Kenya, this stage of the process is particularly critical because its main goal is to remove the mucilage that surrounds the parchment completely. If this sugar-rich layer is not properly removed, it can over-ferment during drying, resulting in unwanted flavours in the bean.

It is often overlooked that all coffee produced worldwide is fermented. This is not a characteristic exclusive to experimental processes or a recent marketing strategy. From traditional washed processes to natural methods, some form of fermentation is always involved. The key difference lies not in whether the coffee is fermented, but in the purpose of the fermentation.

​In traditional origins like Kenya, fermentation primarily serves a technical function in the coffee processing. The classic Kenyan method includes two tank fermentations, interspersed with multiple washes, which help cleanse the bean, stabilise it, and allow its natural flavour profile to shine through. This combination contributes to the bright acidity, structure, and sensory clarity for which Kenyan coffees are renowned.

In recent times, we also see longer, controlled, or experimental fermentations aimed at modifying or intensifying specific cup profiles. While we don’t wish to judge trends or fads in specialty coffee, we believe it’s important to be transparent about when fermentation is used to preserve and enhance the intrinsic quality of a lot, and when it may be employed to mask defects from a poor harvest, potentially through the lactic acids generated during the process. Fermenting coffee isn't a new concept; understanding the reason behind fermentation is what truly makes a difference.