Specialty Fermentation is a specialized “Washed” or “Wet-Processed” method, often utilized in high-quality coffee production (e.g., in Kenya), which combines dry fermentation to break down mucilage, followed by soaking to increase acidity, and finally drying on raised beds. 

1. Fermentation (Dry & Wet) & Soaking

After harvesting, the coffee cherries are pulped (skin removed), leaving the sticky mucilage-covered parchment. 

  • Dry Fermentation (Overnight): The pulped beans are placed in tanks without water, allowing microbes to break down the sugars in the mucilage, typically overnight (12–24 hours). (BRIX / Variations in varieties should guide the output. Recommended Hours 15 to 18 hours.
  • Washing & Sorting: The coffee is washed, often passing through water channels that separate high-quality dense beans (which sink) from lighter, lower-quality beans.
  • Wet Fermentation (Soaking): The beans are then soaked in clean water for an additional 24 hours (or more). This step (sometimes called “double fermentation” or “double-washed”) strengthens amino acids and acids in the bean, resulting in higher complexity, brightness, and a cleaner cup. (KCS Recommended 33 hours).

2. Drying on Tables (Raised Beds)

After the final soak, the mucilage is completely removed, and the coffee is in the “parchment” stage. 

  • Process: The wet parchment coffee is spread out in thin layers on raised drying tables (also known as “African beds” or “pergamino” beds).
  • Management: The beans are turned constantly to ensure even drying and to allow for the hand-picking of any defects.
  • Duration: The drying process takes 1 to 3 weeks, depending on the climate and volume, until the coffee reaches a target moisture level of 11-12%. 

Summary of Benefits

This specific sequence—dry ferment, then wash, then soak, then dry—is designed to: 

  • Remove all mucilage: Ensures no residual fruit remains on the parchment.
  • Enhance acidity: The soaking step in clean water (wet ferment) significantly increases the complexity and acidity of the coffee.
  • Cleanliness: Results in a very clean, bright, and, in the case of Kenya, a very crisp, fruit-toned coffee. 

After drying, the coffee parchment is removed (hulling) to produce the final green beans, which are then roasted. 

Learn Specialty Coffee Fermentation at Kenya Coffee School and Barista Mtaani