Who would have thought that a collapsed volcano would provide a premium and fertile growing environment of high-quality specialty coffee? Sumatra, a large Indonesian island west of Java – where we get the slang for coffee, and south of the Malay Peninsula, is known for its rugged tropical terrain, wildlife, smoldering volcanoes and, of course, coffee.
Fifty million people populate this island and suffered through the 2004 tsunami, which cost many people their lives and many more their livelihood. Coffee farming, in many ways, provided a clear path for the local economies to rebuild upon the back of this disaster. Coffee is a very local family business in this area where small families continuously harvest. Very much in contrast to the large coffee fields and production facilities of Brazil and parts of Mexico. Conversely, Sumatra enjoys almost year round harvesting. Between 8-10 months a year, local farmers are picking coffee beans and shipping them to market, creating a steady funding stream for family growers. At any given time, you’ll see one tree with ripe cherries, green still-growing cherries, and the tree flowering.
Sumatra coffee is known for its distinctive deep and earthy taste. Grown around the edges of a collapsed volcano on Lake Toba and reflecting the traditional Mandheling profile, this distinctive single-origin coffee is grown under the unique conditions that create a deep, velvety flavor and earthy aroma.
Much of the unique flavor comes from the way Sumatra’s coffee beans are processed, the wet-hull method, not to be confused with wet-processed coffee. In the typical wet-processing method, a farm would slowly dry this coffee for days or weeks, usually on a patio or raised bed, or sometimes in a mechanical dryer, down to 10-11.5 % moisture. Sumatra coffee beans are nearly always processed by the wet-hull method, called Giling Basah in Bahasa language.
In Sumatra and other parts of Indonesia, they take their clean wet parchment coffee, dry it a few hours until it has 50% moisture content, and sell it to a collector middleman, or deliver it to a mill. The mill might dry the coffee a little bit more, a day or two, but in general, they send it to a special machine (the wet-huller) when the coffee still has 25-35% moisture content. Then the coffee is laid out to dry, which provides an opportunity for the coffee bean to absorb the natural elements surrounding it. Drying without the shell is rapid, so the mill is able to sell the coffee quickly.
What does this do to the coffee? The flavors of the land and processing can be very pronounced. The unique growing conditions coupled with the wet hulling process creates a lower-acid cup or an herbal or earthy taste, less brightness or fruitiness, and seems to enhance the body. Notes of cocoa, smoke, earth and cedar wood can show well in the cup.
Occasionally, Sumatran coffees can show greater acidity, which balances the body. This acidity takes on tropical fruit notes and sometimes an impression of grapefruit or lime.
Try for yourself
The flavor of typical wet-hull Sumatra can be polarizing among buyers. Each coffee drinker has to discover if this type of flavor is right for them, or not; whether it's a go-to daily drinker or an occasional diversion. Try for yourself to see what exotic flavors appeal to your palate.