Koji Fermentation

Fermentation using koji (Aspergillus oryzae), the mold at the heart of Japanese sake and miso. The mold is cultivated on the coffee (or its mucilage) and produces powerful enzymes — amylases and proteases — that break starches and proteins into sugars and amino acids.

The producer inoculates depulped or whole cherries with koji spores and holds them at the warm, humid conditions the mold needs for a defined culturing window. The mold's enzymes generate flavor precursors (sugars, amino acids) that yeast and bacteria then ferment into unusually deep, savory-sweet aromatics. The lot is then washed or dried normally.

Deeper enzymatic breakdown than standard fermentation yields — reports describe intensified sweetness, savory-adjacent umami notes, and fruit flavors with unusual depth and density.

Koji reaches compounds ordinary fermentation can't touch (starches and proteins), opening genuinely new flavor territory rather than remixing the same fruit-sugar chemistry.

Early reports: dense sweetness, savory-umami undertones, brothy-deep fruit — unlike both classic and anaerobic lots. Documented examples are still few, so treat descriptions as provisional.

Wrong humidity or temperature grows the wrong mold — a food-safety and flavor catastrophe. Koji handling requires clean-room discipline well beyond normal processing skill.

Yes — a microbial culture (Aspergillus oryzae), the same domesticated mold used in sake and miso. It is a processing agent, not a flavoring, but it must be disclosed.

Nothing flavors the bean directly; the mold's enzymes change the coffee's own chemistry. But because koji is an added organism, transparency about it matters more, not less.

A very small number of frontier producers and researchers — documented examples are scarce and terminology is still settling.

Experimental microlots, mainly in Latin America; early documentation comes from processing forums and a handful of producers.

Too few documented commercial lots exist to name reliable examples — we list the method because readers encounter the term, and we flag that documentation is thin.