Coffee Processing

Washed, wet process and wet-hulled explained...

Washed (or wet-processed) is the most common process in the world for high quality specialty coffee. This process helps to eliminate the chances of off-tastes from overripe or fermented coffee cherries which could detract from the flavor of the bean.

 As soon as the beans are harvested and still moist, the coffee cherry is washed off to remove the skin and pulp of the fruit.

The beans are then soaked in water fermentation tanks for 24-72 hours, which breaks down pectin. Next, the sticky fruit (cherry) is washed off the inner green beans. The beans, still coated with their parchment shells, are then dried in the sun for about three weeks until they reach an approximate 11% moisture level. At this point, they are bagged and warehoused for 30 days of rest, or ‘repose’. Parchment is then shelled off, coffee is graded by size and density, and hand-sorted for export. Wet processing results in higher acidity than dry processed methods, and gives coffees a clean taste.

Further confusion arises with the term wet-hulled. Though Indonesia has produced wet-processed coffee (from Java, Bali, Flores, for example), a wet-hulled process is used in Sumatra and Sulawasi, which in the Bahasa language of Indonesia is called Giling Basah. These coffees tend to have more body, lower acidity and a characteristic bluish-green color. The cherries are picked and run through a hand-crank drum for pulping, which grates the fruit skin off the bean.

Farmers leave the coffee to ferment in containers overnight to break down the mucilage, which in turn, is washed off the next day.

The difference between wet-hulled and wet-processed/fully washed at this point is that the Sumatran farmers take the wet parchment coffee (dried after only a few hours to 50% moisture content instead of for the three weeks and 11% moisture mentioned above) to market and sell to collector middlemen. These folks take this mixture to a mill for another day or so of drying (to 25-35% moisture content), then send it through a wet-huller machine which removes the parchment.

Next the beans are set out to dry for two to three days (without their protective parchment coating unlike the washed process described above, where the beans are in parchment for about a month). The complete wet-process/washed method can take two to three months from harvest to export, whereas Indonesian wet- hulled coffee is often exported in less than one month from harvest to export.

Why the huge difference in processing?

The main reason is that Indonesian weather is very humid. In drier high-altitude regions of Central America, pickers might harvest a tree three to four times for ripe fruit over a given season. Indonesian farmers harvest weekly for eight months removing ripe cherries. Drying is quite difficult because of daily rain showers, hence some producers have started building covered drying patios.

This wet-hulled process produces flavor profiles which are uniquely different from coffees from other parts of the world. The specialty coffee industry will need to continue educating growers on avoiding bean defects (which can result from wet-huller machines, for example) so that growers will get the best prices they can; roasters will need to experiment with appropriate profiles for these specially processed beans, while customers will ultimately enjoy the fruits of all the labors.