Koji Fermentation

Koji fermentation arrived in coffee late — coming from traditional Japanese food production. Koji is the name of the Aspergillus oryzae fungus — an edible fungus used for thousands of years in Japan to produce miso, sake, soy sauce, and mirin. It breaks down starches into simple sugars and secretes enzymes that transform flavor dramatically.

Its entry into coffee began around 2018-2020, with experimental producers in Panama and Colombia who decided to test what happens when coffee is produced with a koji culture instead of (or alongside) regular fermentation bacteria.

Process: cherries or depulped beans are inoculated with a koji culture (usually from rice that's been pre-inoculated), then undergo controlled anaerobic fermentation. The fungus releases enzymes that break proteins down into amino acids and starches into sugars — creating notes of umami, miso, fig, squash, and soy sauce.

The final profile is completely different from regular coffee — fans of the style describe it as 'gourmet' and 'savory,' not just sweetness and fruit like other fermentations. But it's not for every taste.

The method is fairly experimental and availability is limited. Only a few boutique farms (Hacienda La Esmeralda in Panama tried it) study it seriously. High cost, risk of experimental failure (fungus failing to take hold), and a polarizing reception profile.