What is double fermentation process in coffee?

Double fermentation process is a post-harvest method in which coffee undergoes two distinct, sequential fermentation phases. The first phase is typically conducted on whole cherries (with mucilage and pulp), the second on the parchment after depulping. This double fermentation aims to develop superior aromatic complexity, with cup profiles that combine the characteristics of both phases — often fruity sweetness from the first phase and cleaner acidity from the second.

Double fermentation process is a relatively recent specialty coffee innovation, popularised in the 2010s by Central and South American producers seeking to go beyond the limitations of traditional processing methods — washed, natural, honey — by adding a temporal and sequential dimension to fermentation.

The protocol structure varies by producer, but the general logic is:

**Phase 1 — Whole cherry fermentation**: Freshly picked cherries are placed in closed containers (with or without water) for 12 to 48 hours. During this phase, micro-organisms on the skin and mucilage begin breaking down sugars. Pectolytic enzymes partially attack the skin and mucilage, releasing aroma precursor compounds and altering tissue structure. Depending on the producer, this phase may be anaerobic or slightly aerobic.

**Phase 2 — Parchment fermentation**: After depulping, the bean with its parchment (mucilage still partially present) is fermented again for an additional 24 to 72 hours, generally under washed conditions (submerged or dry). This second phase extends microbial action on a different substrate and under modified conditions (more acidic pH after the first fermentation, less available sugar, altered microbial flora).

Practitioners describe the resulting cup as combining greater complexity: the first phase contributes more intense fruity notes (analogous to natural), the second delivers clarity and phosphate acidity (analogous to washed). Together, this creates a hybrid profile with more aromatic layers than a standard process.

Stations such as El Injerto (Guatemala) and various Costa Rican estates have experimented with double fermentation variants with significant competitive results. SCA scores for well-managed double fermentation lots typically sit between 86 and 92 points.

Double fermentation process steps

• Selective picking and sorting of cherries at optimal ripeness
• Phase 1: whole cherry fermentation in closed container, 12–48 h (anaerobic or aerobic)
• Depulping of cherries after phase 1
• Phase 2: parchment fermentation (residual mucilage) in closed tank or open air, 24–72 h
• Parchment washing (if washed final) or direct drying (if honey final)
• Drying on raised beds 20–35 days to 10–12 % moisture