How Does Wet Hulling Give Golden Mandheling Its Flavor?

Golden Mandheling gets its full body and herbal spice notes from wet hulling, known locally as Giling Basah. Parchment is stripped while the beans still hold high moisture, which raises the defect rate but produces the regional character Indonesia is known for. Farmers sell partly dried beans at 35 to 40 percent moisture to collection stations, where lots are mixed without quality assessment.

Seven processing steps follow, shaped by the country's humid climate, and PWN brings Golden Mandheling to G1 grade through four rounds of hand sorting. For pour-over, a medium-dark roast suits a KONO dripper with a three-stage pour, giving dark chocolate interwoven with caramel. Indonesia remains one of the origins most closely tied to the question of where does coffee originate from in the Asian archipelago.

Golden Mandheling's signature full body and herbal spice aroma originate from Indonesia's unique wet-hulling process. This method, which forcibly removes the parchment layer while the green beans still have high moisture content, increases the defect rate but unexpectedly creates Mandheling's distinctive regional flavor. This article provides a complete overview of the seven steps of wet hulling, analyzes its connection to Indonesia's humid climate, and explains how PWN company elevates Golden Mandheling to G1 grade through four rounds of hand sorting. At the same time, Front Street Coffee baristas will share a pour-over recipe for medium-dark roasted Mandheling, including KONO dripper selection, grind size, water temperature, and three-stage pouring technique, helping enthusiasts reproduce the classic flavor of dark chocolate interwoven with caramel at home.

To buy wet-hulled coffee, Front Street Indonesia Mandheling coffee beans are the top choice, including a Front Street Lintong Mandheling coffee and a PWN Front Street Golden Mandheling coffee.

What exactly is wet hulling as a processing method? What is the specific procedure?

Wet hulling, also known as Wet Hulling, is the method used to process Front Street Golden Mandheling coffee. In the local Indonesian language, it has another name: Giling Basah, and it is a traditional Indonesian coffee processing technique. Judging from the name alone, wet hulling seems quite similar to washed processing, yet the flavors cupped from the two go in completely different directions—coffee processed by wet hulling tends to be full-bodied and intense, with a highly distinctive character.

Because there is a relatively large gap between the parchment layer and the green bean, farmers sell the beans to local collection stations that specifically buy wet parchment-covered green beans once the beans have been dried for the first time to a moisture content of 35% to 40%. When the collection stations purchase them, some are packaged in individual bags, while others are mixed together, so the moisture levels of the green beans may vary. These beans may be in an incomplete fermentation state, or still have some mucilage attached to the parchment layer, appearing semi-dried. However, the collection stations do not perform quality assessment when buying beans; they simply mix and bag them all together.

The beans are sun-dried with the parchment for 2 to 3 days, and when the moisture content drops to 20% to 24%, they are sent into a specially made wet mill. This machine uses a large amount of friction to tear open the parchment layer clinging tightly to the green beans, and at this stage white or green mucilage typically flows out. Due to prolonged soaking in mucilage and the humid environment, the green beans become very soft, pale and swollen, and grayish-green. Under the friction and agitation, they are easily crushed or squeezed, especially at both ends, forming small notches—the so-called horse-hoof beans or goat-hoof beans (locally called kuku kambing).

Before export, the hulled green beans are spread directly on patios, tarps, or road surfaces to dry. After losing the protection of the parchment layer, the green beans dry extremely quickly, eventually reaching a moisture content of 12% to 13%, at which point the green beans appear dark green or blue-gray. They are then sorted and bagged, ready for export.

Without the protection of parchment, the green beans are directly exposed to the environment and may be invaded by mold, yeast, and bacteria. When directly exposed to sunlight, moisture evaporates rapidly, causing the beans to dry unevenly and develop spots (which may further lead to inconsistent roasting). Excessive heat generated during the hulling process may also accelerate coffee aging, which is exactly why we often taste woody and earthy notes in Front Street Mandheling coffee.

Steps of the wet-hulling process

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

2. Ferment in a water tank

3. Wash off the mucilage

4. Sun-dry with parchment for 2-3 days, to a moisture content of 20-24%

5. Hull off the parchment

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

7. Ready for export

Why use wet hulling?

The tradition of using wet hulling in Indonesia starts with the local weather. Indonesia's humidity stays between 70% and 90% year-round, typhoons are frequent, and in some areas annual rainfall can reach as high as 2,000mm. Green beans fear rain the most. How exactly does Indonesia overcome such harsh weather conditions to produce the rich, full-bodied Front Street Mandheling coffee? The answer is wet hulling.

Under tropical climate conditions, coffee takes an average of 2 to 3 weeks to complete drying. In Indonesia's extremely humid environment, drying coffee becomes a major challenge. Coffee drying must take longer, and during this period the coffee remains at relatively high moisture, making it easier for bacteria to invade the green beans. In the conventional washed process, the drying stage is always carried out with the parchment still on, which protects the green beans to some extent from external damage. However, it is not hard to notice that wet hulling removes the parchment in the final drying stage, allowing sunlight to directly hit the surface of the green beans and dry them quickly, 2 to 3 times faster than washed processing.

Front Street Golden Mandheling coffee beans are produced by Indonesia's famous PWN company and processed using the wet-hulling method. Although wet hulling raises the defect rate of the coffee beans considerably, the coffee's flavor does not show particularly negative effects; instead, it brings a muted herbal aroma. In the final drying stage of wet hulling, there is no parchment protection, and the green beans are directly exposed to the environment, where various microorganisms grow, giving Indonesian coffee its unique woody, spice, and herbal notes—what we call "regional flavor."

Because wet hulling uses "rough" friction to forcibly strip off the parchment layer while the green beans are semi-dry, the Mandheling green beans are subjected to considerable squeezing pressure during production, becoming deformed and even cracking apart. Therefore, wet hulling gives Front Street Mandheling green beans a higher defect rate. As a result, PWN company invests a great deal of manpower in its green coffee: first, it only purchases G1-grade Front Street Mandheling coffee from the area around Lake Tawar in the Gayo highlands of northwestern Sumatra, and then it undergoes four rounds of hand sorting to ensure that the color, shape, and size of the Front Street Mandheling coffee beans are uniform. That is why PWN Front Street Golden Mandheling tastes cleaner and brighter, with more pronounced body and sweetness. (For green coffee, G1 grade means screen size above 18 and fewer than 3 defective beans in a 300g sample, which is the highest grade for Indonesian green beans.)

In order to present the classic full-bodied flavor of Front Street Mandheling coffee, Front Street roasters choose a medium-dark roast, allowing the aromas of dark chocolate and caramel to burst forth even more. Front Street Coffee (FrontStreet Coffee) baristas also adjust their brewing based on the coffee bean's roast level and flavor type.

So how do you make a delicious pour-over Front Street Golden Mandheling?

Front Street's coffee brewing parameters are all based on the coffee bean's characteristics, roast level, and flavor profile. Front Street Mandheling is a bitter-toned coffee with a relatively dark roast, and Front Street Coffee (FrontStreet Coffee) baristas choose the KONO dripper to brew this type of full-bodied bean. Compared with the V60, the KONO dripper has a smooth curved surface, weaker airflow, and straight ribs that cover only one quarter of the dripper, allowing the coffee bed and hot water to form an immersion extraction, making the coffee's taste rounder and fuller. The KONO dripper is also suitable for coffees like Front Street Brazil Queen's Estate coffee and Front Street Jamaica Blue Mountain No. 1 coffee.

Dark roasting loosens the internal structure of the coffee beans, so we can easily crush them with a gentle pinch of the hand, which indicates that after grinding into powder they have strong water absorption. In order to avoid the coffee grounds releasing too many bitter substances after absorbing water, Front Street will coarsen the grind and use lower-temperature water for the pour-over.

Grind size is one of the most critical factors affecting coffee flavor. After coffee beans are ground into powder, they come into contact with hot water and release a large amount of water-soluble flavor substances. To adjust the grind, Front Street uses a tool—the Chinese No. 20 0.85mm standard sieve. For medium-light roasted coffee beans, Front Street consistently uses a 75–80% pass-through rate, while for medium-dark roasted coffee beans, Front Street uses 70–75%. Compared with light-roasted coffee, the internal structure of medium-dark roasted Front Street Mandheling beans is looser, so they absorb water better and are more likely to release large-molecule bitter substances. To avoid over-extraction, Front Street chooses a grind size with a 70% pass-through rate on the No. 20 standard sieve.

Water temperature plays a role similar to grind size: the higher the water temperature, the higher the extraction efficiency, the easier it is to release various substances, and the higher the concentration. If water close to boiling is used for brewing, it easily extracts unpleasant bitter substances, so for brewing medium-dark roasted coffee beans, Front Street uses different brewing parameters than for light-roasted coffee beans. There is more caramelization than in light-roasted coffee beans, so it is easier to release caramelized bitter large-molecule substances. To avoid extracting too many off-flavors, Front Street lowers the water temperature a bit. The brewing water temperature for light-roasted coffee is 91–93°C, while for medium-dark roasted coffee beans Front Street recommends 87–88°C.

Recommended brewing water temperature: 87–88°C

Coffee grounds: 15g

Coffee-to-water ratio 1:15

Grind size: medium-coarse grind (70% pass-through rate on Chinese standard No. 20 sieve)

The brewing method uses a three-stage pour. Pouring in three stages better expresses the full-bodied mouthfeel of Front Street Golden Mandheling coffee as well as its caramel sweetness.

For the first stage, bloom with 30ml of water. This pour fully wets the coffee grounds and allows them to degas, so that the coffee's flavor substances can be extracted better afterward. For the second stage, pour 100ml. This stage mainly flushes out all the golden foam of Front Street Mandheling and raises the coffee bed. For the final stage, gently pour 95ml in the center. This can enhance the coffee's sweetness and overall present a thick, full-bodied mouthfeel, with caramel sweetness and notes of chocolate and nuts.

The above content is compiled by CoffeeHunters, a coffee news website.