What you need to know about Indonesian "wet-hulled" coffee

Earth. Tobacco. Herbs. Cedar. Funk. Love it or hate it, "wet-hulled" coffee's unique flavor profile is immediately recognizable in your cup. But what makes it taste that way?

Many coffee drinkers are oblivious to the details of the process that creates these flavors, for a few reasons:

It's relatively uncommon.

Wet-hulling—or "giling basah" in the local Bahasa language—is only practiced in Indonesia, particularly the islands of Sumatra and Sulawesi. Most other coffee processing methods are more or less global: you can find washed, natural, and honey process/pulped natural coffees from nearly every coffee-producing region.

The name can be confusing.

"Wet-hulled" is easily confused with "wet-processed," another term for "washed," which is the world's most common coffee processing method. But the two processes produce dramatically different results: wet-hulling emphasizes body and mutes acidity, while wet-processing highlights delicate acidity and sweetness.

Its circumstances are regional and unique.

Unless you're aware of the economic and climatic factors unique to Indonesia that gave rise to wet-hulling, the process appears to be unnecessarily complicated. 

Here's how it works:

1) A smallholder farmer picks coffee and runs it through a hand-cranked depulper to remove the skin from the coffee cherries.

2) The cherries are fermented overnight to break down the mucilage—the fruit layer beneath the skin—which is then washed off. 

3) The coffee is dried for a few hours on a patio until it reaches about 50% moisture, at which point the bean is still swollen inside the parchment (a thin layer protecting the inner seed). Contrast this to a typical washed coffee, which would be dried to 10-12% moisture content inside the parchment over a period of weeks.

4) The farmer then sells the coffee to a middleman at the local market in order to get paid quickly. (For reference, it typically takes a coffee farmer 2-3 months to dry, bag, rest, hull, and finally sell and export a washed coffee.)

5) The middleman then sells the coffee to a collector or mill, where it is further dried to 25-35% moisture content and sent through a wet-huller to remove the parchment layer. Because the bean has not yet dried and shrunk away from the parchment, the friction required at this stage can damage the bean, which is still moist and pliable.

6) The mill then air-dries the hulled coffee to 12-13% moisture. Without the protective parchment layer the coffee dries quickly, but it's exposed to wider temperature variation as well as ambient yeast and bacteria.

7) The coffee is ready to export just a month after it was picked.

The results:

The quick pace of the wet-hulling process is a necessity in Indonesia's humid and rainy climate, which makes it difficult to dry coffee consistently for extended periods. Plus, coffee grows quickly in this climate and must be picked and processed frequently throughout the harvest. In order to reduce risk and ensure a profit, farmers and middlemen sell their coffee as quickly as possible. 

We source Indonesian coffees that have been processed with great attention to detail and carefully sorted (above), sidestepping problems that can arise in traditional wet-hulling. Weather permitting, the coffee is dried in the sun on clean patios, or on beds protected from rain, in order to prevent damage and defects. Flavors are rich and earthy rather than musty, with sweetness and acidity that you won't find in lower-quality lots.

Wet-hulled coffee's intense flavor is not for everyone, but as a single-origin offering it provides a unique experience for the adventurous coffee drinker. Many blends rely on Sumatran coffees for body, making them an important part of any coffee program. Enjoy!