Is the Wet-Hulled Coffee Processing Method the Same as Washed Processing? What Are the Specific Steps of Wet-Hulling?

Introduction to Coffee Processing Methods by FrontStreet Coffee

In traditional washed processing, fresh coffee cherries have their pulp removed and are left to ferment in concrete tanks overnight, undergoing acidification and the breakdown of pectin. The parchment beans are then sun-dried for about 20 days, until they reach 11% moisture content. At that point they can be bagged, the parchment layer is removed, and the coffee is graded by density and size and sorted by hand for export.

The green beans stay inside the parchment layer and continue to "wash." Protected by the parchment, they sit in a relatively clean micro-environment that stabilizes moisture, softens swings in day and night temperature, and reduces the direct impact of sunlight.

In washed processing, the beans are typically dried to 11% moisture content. They become what we know as dried green beans, with a thin parchment that comes off easily.

What is Wet Hulling?

So what exactly is wet hulling, and what are its specific steps?

Wet hulling, or Wet Hulling, is called Giling Basah in the local language and is a traditional Indonesian processing method. Judging by the name alone, it seems similar to washed processing, but the cupping flavors of the two methods are completely different. Coffee processed by wet hulling is usually full-bodied and intense, with a very distinct character.

Wet Hulling Process

Because there is a large gap between the parchment shell and the green bean, farmers sell their beans to local collection stations that buy wet parchment coffee once the beans reach their first drying stage at 35-40% moisture content. During collection, some beans go into separate bags and others are mixed together, which leaves the batch with uneven moisture levels. This may stem from incomplete fermentation or from mucilage still clinging to the parchment in a partially dry state. Quality is not assessed at collection, however; the beans are simply mixed and bagged together.

The beans, still in parchment, are sun-dried for 2 to 3 days until they reach 20-24% moisture content, then run through a specially designed wet-hulling machine. The machine uses heavy friction to tear away the parchment layer that clings tightly to the green bean. At this stage, white or green mucilage typically flows out. Long soaking in mucilage and the humid conditions leave the beans soft, pale, and swollen, taking on a grayish-green color. Under the friction and agitation they bruise easily, especially at the ends, forming small gaps that produce the horse-hoof or goat-hoof shape known locally as kuku kambing.

Final Processing

Before export, the hulled green beans are spread directly in courtyards, on tarps, or even on roads to dry. Without the parchment's protection, they dry very quickly, finally reaching 12-13% moisture content. At that point they show a deep green or bluish-gray color. The beans are then sorted, bagged, and made ready for export.

Without the parchment shield, the green beans are directly exposed to their surroundings and can be affected by environmental molds, yeasts, and bacteria. In direct sunlight, moisture evaporates fast, causing uneven drying that leaves spots, which in turn can produce inconsistent roast levels later. Excessive heat during hulling can also age the coffee quickly, producing the woody, earthy flavors we often taste in Sumatran coffee.

FrontStreet Coffee Recommendation

FrontStreet's Indonesian Mandheling is a straightforward way to taste what wet hulling does to a coffee. Sourced from the Lake Toba area of the Lintong region in Sumatra and roasted medium-dark, it shows the classic profile: low acidity and a full, thick body, with caramel, dark chocolate, and toasted bread aromas and a long, sweet finish, ideal for anyone who likes a strong, heavy cup.

For the highest grade, FrontStreet's PWN Golden Mandheling is the flagship. PWN buys only high-grade Mandheling green beans and sorts every lot once by machine and then by hand, meeting a standard of beans sized 18 screen and above with fewer than three defects per 300 grams of green beans, plus three rounds of hand sorting to remove any remaining defects. The result is a cleaner, sweeter Mandheling with sandalwood, herbs, spice, roasted hazelnut, caramel, and dark chocolate. FrontStreet's classic espresso blend rounds out the range, layering the creamy, nutty character of Brazilian coffee with medium-dark Mandheling to add body and a distinctive sandalwood, herbal, and spice aroma.