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, also known as Wet Hulling, is called Giling Basah in the local language and is a traditional Indonesian coffee processing method. Judging from the name alone, Wet Hulling is very similar to wet processing (washed processing), however, the cupping flavors of these two processing methods are completely different. Coffee processed by Wet Hulling is usually rich and intense, with a very distinct personality.

Steps of Wet Hulling Processing Method

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 parchment for 2-3 days until the moisture content reaches 20-24%

5. Hull the parchment

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

7. Prepare for export

Why Use Wet Hulling?

Climate Reasons

The tradition of using Wet Hulling in Indonesia begins with the local weather. Indonesia's humidity is between 70-90% throughout the year, with constant typhoons. In some areas, annual rainfall can even reach as much as 2,000mm. As we know, green beans are most afraid of rain. How does Indonesia overcome such harsh weather conditions and produce rich, mellow Mandheling coffee? That is by relying on Wet Hulling.

Under tropical climate conditions, coffee takes an average of 2-3 weeks to dry. In Indonesia's humid climate, drying coffee becomes a major problem. Coffee drying must take longer, and during this time, the coffee still maintains high humidity, making it easier for bacteria to penetrate the green coffee beans.

In the regular washed processing process, drying is carried out with the parchment to protect the green beans from external damage to a certain extent. However, we can note that Wet Hulling removes the parchment for the final drying step, allowing sunlight to directly hit the surface of the green beans, causing the green coffee beans to dry quickly, 2-3 times faster than washed processing.

Economic Benefits

When Dutch colonizers first introduced coffee to Indonesia in the 17th century, these colonists pursued more and faster economic returns. Wet Hulling greatly shortened the time spent on the farm and also significantly reduced labor costs. This aligns with the investor mindset of pursuing quick profits and reducing costs. This is also a reason that promoted the Wet Hulling processing method.

Defects and Kuku Kambing (Goat Hoof Beans)

When hulling the parchment in Wet Hulling, the coffee's moisture content is still as high as 20-24%, while in general processing methods, coffee is hulled only when the moisture content drops to 10-12%. In a "semi-dry" state, the parchment tends to adhere to the surface of the green beans, making hulling more difficult than "fully dry" hulling, requiring greater friction.

But on the other hand, "semi-dry" green coffee beans are very fragile at this time, with hardness far inferior to "fully dry" green beans, so the beans are more likely to be squeezed and form small cracks. This is what we often call horse hoof or goat hoof beans (locally called kuku kambing).

The ultra-fast speed of Wet Hulling processing also causes Mandheling to have higher defects. The processing plant will arrange employees for manual defect sorting. Generally, there will be DP (double picking) and TP (triple picking). Mandheling that undergoes triple picking will be superior in defect rate to double picking.

Important Notice :

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