Yeast Fermentation

Coffee in fermentation tanks at the Gahahe site in Kayanza, Burundi

Yeast fermentation involves adding different types of external yeasts to the fermentation stage of wet processing in order to help control the outcome, and ultimately, how the coffee tastes. Naturally occurring yeasts are always a part of the fermentation process, which along with bacterias, react with sugars in the coffee fruit, resulting in chemical reactions that affect flavor, and break down the sticky outer fruit layer making it easy to remove. The results of the yeast fermented coffees we’ve tasted are mixed, but we have seen discernible differences, and even superior results, when tasting alongside the same coffee that underwent traditional wet processing (specifically in Burundi). Cost and labor are also considerations the farmer has to make, both of which this process significantly adds to production.

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