Definition
What fermentation does
Fermentation is the metabolic process where yeasts, bacteria, and other microorganisms break down sugars in coffee mucilage. This produces organic acids, alcohols, and other compounds that affect final cup flavor.
In washed processing, fermentation happens in tanks over 12-36 hours to remove mucilage. In natural processing, it happens inside the drying fruit over 2-4 weeks. Both require careful control--too little yields flat coffee; too much creates vinegar or alcohol off-notes.
Fermentation basics
Why Roasters Care
What fermentation affects
Acidity character
Fermentation produces organic acids. Lactic, acetic, malic. The balance shapes perceived acidity--bright vs. sour vs. flat.
Sweetness development
Controlled fermentation develops flavor precursors that become sweetness during roasting. Sugar alone isn't enough.
Defect risk
Over-fermentation causes vinegar, onion, or alcohol defects. Under-fermentation leaves mucilage that affects drying.
Natural complexity
The extended fermentation in naturals creates fruit complexity--but also risk. It's why naturals vary more.
Controlled experiments
Some producers now use controlled anaerobic or extended fermentation for specific flavors. Specialty innovation.
Quality indicator
Clean fermentation reflects producer skill and infrastructure. It's a sign of quality control at origin.
Our Approach
How we evaluate fermentation
Cup for ferment defects
Sam cups every lot for fermentation quality. Vinegar, onion, and boozy notes are automatic rejects.
Source from controlled stations
We work with washing stations that monitor fermentation--timing, temperature, tank cleanliness.
Natural selection rigor
For naturals, we're especially careful. Clean fermentation separates good naturals from problematic ones.
ARDI as proof
ARDI demonstrates what controlled natural fermentation looks like--fruit without funk, 16 years running.
Current Inventory
Natural coffees with clean fermentation
WUSH WUSH
Oromia, Hambela
Sangaria | Fruit Bomb | Floral | Sweet Finish
Natural, 120 hours dry Fermentation! · In Stock
Natural ARDI
Sidama, Damo
Clean Strawberry | Peach | Sweet Finish
Natural · In Stock
Harrar Gr 1
Oromia, Micheta
Chocolate | Barries | Carmel | Full Body
Natural · In Stock
NATURAL SIDAMA GR 4
Sidama
Dark Chocolate | Nuts | Medium Acidity | Complex | Comforting
Natural · In Stock
Want cleanly fermented coffee?
Request samples and taste what proper fermentation produces.