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What's the Difference Between Sumatra's Unique Wet-Hulling and Washed Processing Methods?

Published: 2026-01-27 Author: FrontStreet Coffee

Last Updated: 2026/01/27, For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style). Are wet-hulling and washed processing methods about seeking common ground while preserving differences? In traditional washed processing methods, fresh coffee cherries have their pulp removed and are left to ferment overnight in concrete water tanks.

As the single-origin coffee with the deepest roast level on FrontStreet Coffee's bean menu, Mandheling coffee possesses rich roasting aromas, a solid and mellow mouthfeel, and low acidity. When dark roasted, we can experience both its prolonged bitterness and its elegant sweetness. Through smell and taste, we can simultaneously perceive its unique earthy fragrance, which is truly captivating.

At this point, some friends might ask: since they are all medium-dark roasted coffee beans, why does only Mandheling have this distinctive flavor?

The Origin of Mandheling's Unique Flavor

It's well known that Mandheling comes from Sumatra Island, Indonesia. The biggest difference from many coffee-producing regions is that Indonesia's local weather is variable, humid, and rainy, with annual humidity between 70-90%. Sometimes it's sunny in the morning and heavy rain in the afternoon, with typhoons arriving unexpectedly. Annual rainfall can even reach over 2000mm. Under such harsh climate conditions, it's very difficult and time-consuming to completely dry the parchment beans to the specified moisture content. Moreover, Indonesia is a major coffee-producing country focused on mass production. To shorten coffee bean processing time and quickly sell them for cash, people have developed a unique semi-washed method: Wet Hulling.

Wet Hulling, known as "Giling Basah" in Indonesian, like washed, natural, and honey processing, has existed and been practiced in coffee production for many years. Currently, wet-hulled coffee is still primarily produced in Indonesia, mainly in the northern regions of Sumatra and the Sulawesi producing areas.

The Wet Hulling Process

Initially, this region also used natural processing, but the quality was unstable, so they switched to a semi-natural method similar to Brazil's. However, unlike Brazil's arid climate, they couldn't dry the sticky parchment beans outdoors for several days after removing the coffee cherry pulp. Doing so in the hot, rainy Indonesian climate would only cause them to mold directly, so they would only dry outdoors for one to two days.

When the moisture content of the parchment beans drops to 30-50%, they are purchased by brokers. At this point, the mucilage layer hasn't solidified yet, and the beans are still semi-hard and semi-soft, but they need to be promptly taken to the processing plant to use specialized machines to grind off the parchment hull to prevent over-fermentation and sour odors.

Due to the greater difficulty of hulling in wet hulling, machines need to use greater friction to tear open the parchment layer tightly attached to the green beans. At this stage, white or green viscous liquid usually flows out. Due to long-term soaking in this viscous liquid and the humid environment, the green beans eventually become soft, turn white and swollen, and form a gray-green color. Through the stirring of friction, the green beans are also more easily crushed or bruised, especially at both ends, forming small缺口 that resemble sheep's hooves. This is why Sumatra has a higher ratio of "sheep's hoof beans."

It's important to know that coffee beans have four protective layers: pulp, mucilage, parchment hull, and silver skin. Wet hulling, however, removes the third and fourth protective layers midway. This means the coffee beans are directly exposing their "inner beans" to receive sunlight.

After the parchment beans have their hulls ground off by machines, they continue to dry until the moisture content reaches approximately 12-15%, at which point they can be bagged. Finally, these coffee beans are sent for machine sorting to remove various impurities and then classified by particle size.

The "naked beans" without the parchment layer dry very quickly, while also being directly exposed to sunlight and moisture, allowing various microorganisms to grow. This gives Indonesian coffee its unique woody, spicy, and herbal plant aromas - what we call "terroir flavor."

The Distinctive Characteristics of Mandheling

From this, we can understand that Mandheling's unique herbal fragrance and沉木味 are both due to the local high humidity, which forces the entire post-processing to be divided into three stages for drying the mucilage layer. This is also a rare processing method worldwide, accidentally creating Mandheling's special low acidity, thickness, and earthy flavor characteristics.

Some customers might ask FrontStreet Coffee: Which Mandheling should I choose? If you're a coffee novice just starting out and hoping to understand different regional flavors, FrontStreet Coffee suggests starting with our cost-effective Lindong Mandheling as your daily bean. This way, you can understand the flavor characteristics of several major producing regions before choosing your preferred type. But if you're already a coffee connoisseur, FrontStreet Coffee believes PWN Golden Mandheling coffee is an excellent choice.

Brewing Recommendations

Mandheling presents full-bodied roasted coffee aromas and a solid mouthfeel, suitable for various brewing extraction methods, such as pour-over, siphon pot, French press, AeroPress, moka pot... FrontStreet Coffee's favorite way is to taste the rich mouthfeel of Golden Mandheling coffee in the form of pour-over black coffee.

FrontStreet Coffee prefers to use KONO drippers for extracting coffee beans that express thickness and richness. The KONO dripper only has short ribs in the middle and lower sections, while the upper part is a smooth curved surface. This way, when we wet the dripper, it fits tightly with the filter paper, restricting gas release during coffee extraction. Therefore, hot water stays longer in the dripper, increasing coffee extraction rate and concentration, making the coffee taste more rich and mellow. KONO drippers are also suitable for beans with rich flavor profiles like Brazil Queen Estate coffee.

Recommended Brewing Parameters

Generally, FrontStreet Coffee chooses 15g of coffee grounds. The choice of coffee amount usually refers to the design specifications of the dripper, and FrontStreet Coffee's dripper is suitable for 1-2 people's servings, which can be between 15-20g. Too much can easily affect extraction. Regarding the choice of coffee-to-water ratio, 1:15 is most commonly used, and ratios between 1:13-1:17 are all acceptable. FrontStreet Coffee believes that everyone's taste is different - 1:13 might be too strong for some people, while 1:17 might be too weak, so we take the middle value of 1:15.

Brewing parameters: KONO dripper, 87°C water temperature, 1:15 coffee-to-water ratio, China #20 standard sieve filtered 70% grinding degree, 15g coffee grounds, three-stage extraction.

First wet the dripper to make the filter paper fit tightly with the dripper, then pour in the ground coffee powder, trying to level the coffee bed as much as possible. Pour 30g of 87°C hot water from the center to start a 30-second bloom. At this point, you can see the dark roasted Mandheling coffee form a high dome. Then begin evenly pouring the second stage until the liquid weight reaches 125g. Wait until the coffee liquid drops to halfway before starting the final 100g pour. Note to maintain a small, steady water flow throughout to avoid uneven extraction. Once all the coffee liquid has finished dripping, you can remove the dripper, shake the coffee in the sharing pot to mix, and begin tasting.

The brewing parameters mentioned by FrontStreet Coffee are all based on fresh coffee beans, so freshly roasted coffee is the primary condition here. The coffee beans shipped by FrontStreet Coffee are all freshly roasted within 5 days. When you receive the coffee from logistics, it's just in the optimal flavor window. This is to ensure every customer can enjoy good coffee with the most complete flavor profile.

The freshly brewed PWN Golden Mandheling coffee clearly has a solid mouthfeel, with more intense cedar, spice, dark chocolate, and roasted hazelnut aromas. The aftertaste is clean, the flavor is elevated to another level, and you can feel the sweetness of caramel and the lingering finish.

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