GILING BASAH - WET HULLED PROCESSING
Ever wondered why Sumatran coffees all seem to have “that taste?” The earthy and spiced flavor that all Indonesian coffees seem to posses regardless of roast profile is due to a unique processing method that is really only done there: wet hulling.
Wet hulling, or “giling basah” locally, is unique to Indonesia, though it is sometimes practiced in parts of Vietnam - and it’s idiosyncratic there for two reasons. First, coffee was introduced to Indonesia in the late 1600s by the Dutch East India Trading Company (often referred to by its Dutch initials, VOC), and the VOC was concerned with exactly one thing: profit at all costs. Since the wet hulling process takes less time than traditional drying methods, the VOC was able to export coffee more quickly and thus turn a profit faster during a time when coffee prices were exorbitant: as much as 1% of an average yearly income for a mere kilogram of beans.
The second reason is more practical and is why giling basah is still practiced in Indonesia, particularly Sumatra, today. Indonesia is a hot, humid climate with abundant rainfall - more so than any other specialty coffee producing country. Indonesia doesn’t have a typical wet/dry season climate structure, having mostly constant rainfall and cloud cover. This makes drying coffee exceptionally difficult. You can see this represented visually below thanks to Perfect Daily Grind and World Weather Online. Note how Sidamo in Ethiopia has a defined wet and dry season, with coffee harvests and processing coinciding with the dry season. In Bandar though, a city on the southern tip of the island of Sumatra, the rainfall both in amounts and days of rainfall per month is nearly constant. You may remember from our washed processing materials that it takes up to three weeks to fully dry a coffee - this kind of drying is nearly impossible in Indonesia.
Where wet hulled processing differs from typical washed processing is in the drying method. Washed or naturally processed coffees are typically kept in their cherry or parchment layer until export, when they are dry milled (sometimes called “hulling”). This promotes even drying to about 11% moisture content, and also helps protect the bean from microbial attack. In Indonesia, the parchment is removed while the beans are still “wet,” as high as 40% moisture. This is done using a machine very similar to a de-pulper that is calibrated to remove the wet parchment layer. The beans are then spread out to dry without this layer, which leads to quicker drying times in a humid environment where bacteria can run rampant.
Wet hulling is responsible for the typical flavor profile associated with Indonesian coffee: wood, earth, spice, tobacco, leather, mustiness, and low acidity. It also imparts a heavy body to the coffee. These flavors, which may be considered defects in fully washed or natural coffees are often sought after by coffee drinkers. If you’ve ever had a customer wax poetic about the “bold” flavors of Sumatran coffee, you know what I mean. Some coffee professionals feel the process clouds the taste of terroir; that is, you’re tasting giling basah rather than Sumatran coffee notes. Regardless, wet hulling provides us with unique flavors and a wholly unique story as to its development as a process.
Customers love hearing about our coffees - both the technical and the story based aspects. It’s kept me excited about working in coffee for the last fifteen years, and I hope it does the same for you.