Wet hulling, or Giling Basah, is a type of coffee processing that is unique to Indonesia and most often used in Sulawesi and Sumatra. Despite sounding similar to wet processing, the most common type of coffee processing, wet hulling is actually very different. Wet hulling as a processing method has two driving causes: moisture and money.
The wet climate of Indonesia makes it difficult for coffee to dry for long periods of time. A combination of rain and humidity prevent easy drying, and the farmers had to come up with another way to process their coffee. Another factor is the desire to get their coffee to the market as fast as possible. Spending extensive time on drying out coffee means they have to wait longer to sell it, so they prefer using a faster method.
Wet hulling begins with small holder farmers picking their coffee. They often only have a few half acres of land, and not very many trees. Their only piece of processing equipment is a hand-cranked pulper that is shared among the farmers of their village. They run the coffee cherries through the pulper, removing the skins but leaving most of the fruit, or mucilage, still on the coffee bean.
They then ferment the beans overnight, using sacks, tubs, tanks, or whatever method they have access to. The fermentation makes it much easier to wash off the mucilage in the morning. Once the mucilage has been removed, the parchment still remains. The parchment is a thin shell that covers the outside of the coffee bean and can be easily removed if the coffee is dry.
The farmers, however, opt not to wait until the beans dry out completely. They leave the parchment coffee out until it has dried to 50% moisture capacity and sell it to their local market. The buyers will buy a heaped can full of coffee and sell a level can full, paying and charging the exact same price. They make their money off the small excess amount.
Once the buyers have it, they will keep the parchment coffee in bags for a while, which lets the beans ferment further. Some farmers may have better quality coffee than others, but the buyers often mix all the coffee together, defects and all. The buyer also finally removes the parchment, using a machine called a wet-huller. The machine uses a lot of friction to remove parchment from the swollen, still moist bean. This force often mangles or crushes the bean, causing wet hulled coffee to have more defects. Indonesian processors commonly use a Kemajuan huller, a Dutch-designed and Javanese manufactured huller that is modified to process wet hulled coffee. It can hull beans between 35 and 45 percent moisture content and output 800 kilograms of green beans an hour.
The now parchment-less coffee then dries further and waits in a warehouse to be sold. The speedy process of wet-hulling makes it possible to sell coffee within a month of its first being picked.
Wet-hulled coffee has a distinctive tendency towards earthy, solid flavors. It has low acidity and brightness due to the fermentation it undergoes during processing. It has been described with flavors of humus, herbs, and moss. Low-quality wet hulled coffee sometimes has more bitter vegetable flavors that make for a slightly more unpleasant cup of coffee. It is also known for a distinct spicy flavor, which gives it a place in the Starbucks Christmas blend.
The quality of wet-hulled coffee varies. When done well, an actually good cup of coffee can be achieved. However, wet hulling is frequently done as a method of saving time and getting profit as fast as possible. Wet hulling in itself does not guarantee poor coffee quality, and when done properly creates a flavor that many coffee connoisseurs enjoy. Competitive coffee tasters often score wet-hulled coffee as among Indonesia’s best flavors. Despite the sometimes sloppy method, wet hulled coffee can be an amazing drink.