How is Sumatra Coffee? Introduction to Semi-Washed Sumatra Coffee Characteristics

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FrontStreet Coffee - Introduction to Sumatra Semi-Washed Processing Method

The Unique Wet-Hulling Method of Mandheling

Wet hulling - known locally as Giling Basah - is a traditional Indonesian coffee processing method. Judging by the name alone it sounds close to washed (wet) processing, yet the two produce completely different cup profiles. Wet-hulled coffee is typically rich and intense, with a very distinct personality.

Steps of Wet-Hulled Processing

1. Remove the skin and pulp, keeping the parchment and mucilage

2. Ferment in the water pool

3. Wash away the mucilage

4. Sun-dry with the parchment on for 2-3 days until the moisture content reaches 20-24%

5. Hull off the parchment

6. Dry the green beans down to a moisture content of 12-13%

7. Prepare for export

Why Use Wet Hulling?

Climate Reasons

Indonesia's tradition of wet hulling starts with the weather. Humidity stays between 70-90% all year, typhoons roll through regularly, and in some areas annual rainfall can reach 2,000mm or more. Green coffee beans are terribly vulnerable to rain - so how does Indonesia overcome such harsh conditions and still produce rich, mellow Mandheling coffee? By relying on wet hulling.

Under tropical conditions, coffee normally takes an average of 2-3 weeks to dry. In Indonesia's humid climate, drying becomes a major headache: the process drags on even longer, and while the coffee sits at high humidity for all that time, bacteria can more easily penetrate the green beans.

In conventional washed processing, drying happens with the parchment still on, which shields the green beans to some extent from external damage. Wet hulling, however, strips the parchment off for the final drying stage, letting sunlight strike the surface of the green beans directly. The beans dry far faster - roughly 2-3 times quicker than washed processing.

Economic Benefits

When Dutch colonists first brought coffee to Indonesia in the 17th century, they wanted greater and faster returns. Wet hulling dramatically shortened the time beans spent on the farm and cut labor costs substantially - squarely in line with the investor mindset of quick profits and lower overhead, and another reason the method took hold.

Defects and Kuku Kambing (Goat Hoof Beans)

When the parchment is hulled off in wet hulling, the coffee's moisture content is still as high as 20-24%, whereas most other methods wait until it drops to 10-12%. In this "semi-dry" state the parchment clings to the surface of the green beans, making hulling harder than with fully dry beans and demanding far more friction.

On the other hand, semi-dry green beans are very fragile at that moment - far softer than fully dried beans - so they are easily squeezed and form small cracks. These are what we commonly call horse hoof or goat hoof beans (known locally as kuku kambing).

The sheer speed of wet hulling also leaves Mandheling with a higher defect rate. Processing plants therefore assign workers to sort defects by hand, generally as DP (double picking) or TP (triple picking). Mandheling that has been triple-picked will show a noticeably lower defect rate than double-picked lots.

FrontStreet Coffee Recommendation

If wet hulling has you curious about Sumatran coffee, start with FrontStreet Coffee's PWN Golden Mandheling. Produced by Indonesia's PWN company to exceptionally strict standards - only beans above an 18 screen size are selected, with fewer than 3 defects permitted per 300g sample to meet the top G1 grade, followed by three rounds of hand sorting - it delivers a clean, sweet, low-acid cup with a thick, velvety body, herbal and dark chocolate aromas, and a faint earthy note. Golden Mandheling is chiefly exported to the Japanese and American markets, so genuine lots are limited; FrontStreet's product listings show the PWN certificates and PWN-branded bags that set its Golden Mandheling apart.

FrontStreet brews its Golden Mandheling as a pour-over to bring out its best: water at 87-88°C, 15g of coffee at a medium-coarse sugar-like grind, a 1:15 ratio, and a three-pour method. Bloom with 30ml of water to wet the grounds fully, pour 100ml to lift the bed and draw out the golden crema, then finish with a gentle 95ml center pour to highlight caramel sweetness, chocolate, and nuts over that signature full body. For espresso lovers, FrontStreet's classic blend - Brazil's creamy nuttiness enriched with medium-dark Mandheling, plus a touch of robusta for extra crema - offers butter, roasted chestnut, and caramel flavors with sandalwood, herbal, and spice undertones, working beautifully for lattes and Dirty drinks alike.