Processing

Fermentation

The microbial process that breaks down coffee mucilage and develops flavor precursors. Happens in tanks for washed and inside the fruit for naturals. A critical quality variable.

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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

Washed fermentation 12-36 hours in tanks
Natural fermentation 2-4 weeks in fruit
Key organisms Yeasts, LAB, bacteria
Products Acids, alcohols, esters
Critical control Time, temperature, oxygen

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

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