aka Honey, Pulped Natural, Semi-Lavado
The washed process and the semi-washed process are very similar in the first step – the cherry is removed (pulped), but here the similarity ends. Semi-washed coffees are dried with the mucilage clinging to the outside of the parchment.
The fruit of the coffee plant, known as the cherry, is picked once it ripens on the branch. Mature coffee cherries can manifest themselves in red, yellow and orange pigmentation. After being harvested, cherries are transported to washing stations where they are first weighed and then loaded into a depulping machine. The coffee cherry is then sliced open by either a metal or sharp plastic blade. The beans are squeezed out of the cherry via centrifugal force. The semi-washed process, also known as pulped natural and honey coffee in some regions, begins with the depulping of the coffee cherry, the outermost layer of the coffee fruit.
The cherry can be pulped with a depulper, or with mechanical demucilagers. Mechanical demucilagers can be calibrated to alter the percentage of mucilage that remains intact on the beans. Mucilage, composed of natural sugars and alcohols, plays a crucial role in developing the sweetness, acidity and overall flavor profile in the coffee beans. Since mechanical demucilagers are a serious investment for coffee producers, the method (depulper or mechanical demucilager) that a producer uses is primarily determined by their financial means.
The parchment, with its layer of mucilage remaining, is taken directly to dry in the sun (skipping the fermentation tank and washing stage that occurs at this point in washed process coffee). Mechanical drying is not feasible for beans processed in this manner since the mucilage will stick to the walls of the drying machine and destroy the equipment. Instead it must be dried in the sun on patios or drying beds made of very flat, even surfaces. If any part of the drying surface is uneven, the producer runs the risk of allowing the mucilage to condense in one area of the bed and create rot that will harm the quality of the coffee.
Coffees that are only fermented for a very short amount of time, too short to remove the mucilage layer entirely from the outside of the parchment, are still considered semi-washed (see Indonesian Wet Hulling).
Drying is an extremely delicate process that must be attended to constantly. The beans must be rotated, usually by raking, to ensure that they dry evenly to avoid fermentation and rot. During the drying stage the remaining mucilage dries into the core of the bean changing the final flavor profile.
The parchment has a slightly mottled, red/brown appearance similar to caramelized sugar on the outside of a candied nut. The coffee beans are then stored and left to rest surrounded by the layer of parchment, or pergamino in Spanish, and dried mucilage until ready for shipment.
When processed properly, semi-washed coffees have an intense sweetness, heightened mouthfeel and rounded acidity.
Indonesian Wet Hulling
Coffee production and processing in Indonesia is unique, and certain techniques, like wet hulling, seem entrenched in the culture. All of the farmers that Stumptown works with in Indonesia are smallholders with anywhere from 0.5 to five hectares. After harvesting, the coffee is depulped using hand cranked devices. The depulped coffee beans, laden with their mucilage, are fermented for a short time in wicker baskets or plastic sacks, which is not the most ideal situation. Those using concrete fermentation tanks rarely keep them clean enough to make it a more viable option. After fermentation, the coffee beans are washed by hand. Since these beans are only fermented for a short period of time and often washed just once, so not all of the mucilage is removed which results in a semi-washed coffee.
After washing, the parchment covered coffee is laid out to dry on patios, raised beds or on plastic tarps. Instead of drying coffee beans to 10-12% moisture levels, the norm in most other coffee regions, Indonesians only dry to 40% moisture before they hull the wet beans (remove the parchment). These still wet green coffee beans are then dried in the sun to the usual 10-12% moisture content. This process flattens acidity while increasing mouthfeel. A good chunk of that “classic” Sumatran profile is due to this wet-hulling process. The other elements that are a part of the process, such as fermenting in sacks, not fully washing, less than ideal drying situations and the trade of wet parchment also play a significant role in the final flavor.