Dry fermentation

Dry fermentation ferments pulped coffee without adding water to the tank — the beans sit in their own mucilage.

Versus wet fermentation

Wet fermentation submerges the coffee, which moderates temperature and dilutes the products of fermentation.

Dry fermentation concentrates everything. Microbial activity is more intense, temperature rises faster, and the flavor contribution is greater.

The result

More pronounced fruit and complexity than a wet-fermented washed coffee, while remaining cleaner than a natural.

The risk

Less margin. Without water to buffer it, an unmonitored tank can overheat and over-ferment quickly, producing sour, vinegary coffee.

Producers running dry fermentation successfully monitor temperature closely and stop on measurement rather than on the clock.

Where it is used

Kenya traditionally, and increasingly by quality-focused producers elsewhere experimenting with fermentation as a flavor variable.

Brewing it

Filter, light roast, a clean brewer.

How producers know when to stop

Traditionally by touch: a handful of beans rubbed together feels gritty, not slippery, once the mucilage has broken down. More careful producers measure pH, which falls as fermentation proceeds, and temperature, and stop at a target rather than at a fixed hour. After fermentation the coffee is washed and dried as any washed coffee, so the bag usually says only washed; dry fermentation appears on the label mainly from producers who treat it as a selling point.