Introduction to the Characteristics of Indonesian Mandheling Coffee: Common Processing Methods Including Washed, Natural, and Wet-Hulled

The biggest difference between Indonesia and many other coffee-producing regions lies in the local humid weather. Indonesia's humidity ranges between 70-90% year-round, typhoons can strike unexpectedly, and annual rainfall even exceeds 2000mm. Such harsh weather conditions simply cannot accommodate the 2-3 week sun-drying process used in Africa. Wet processing not only consumes more time but also requires more labor costs and water resources, which Indonesia, focused on mass production, cannot afford. Consequently, they have developed a unique semi-washed method—the wet hulling process.

Unlike traditional sun-drying and water-washing methods, wet hulling first uses a hulling machine to remove the outer skin of the coffee cherry, then directly pours it into a pool for brief fermentation of several hours. At this point, a small amount of mucilage still remains on the parchment shell, which is removed through brushing. Next, the parchment coffee is dried until the moisture content reaches 30-40%, at which point the coffee farmers sell the raw beans to buyers. The buyers then directly hull the partially dried parchment coffee, accelerating drying, removing mucilage and parchment to obtain raw beans.

Because the hulling machine uses significant friction to tear away the parchment layer tightly attached to the raw beans, this stage typically releases white or green mucus. After prolonged exposure to this mucus and humid conditions, the raw beans become soft, pale, swollen, and form a gray-green color. Through the agitation of friction, the raw beans are also more easily crushed or bruised, particularly at both ends, forming small gaps that create "elephant beans." The "naked beans" without parchment dry very quickly while also being directly exposed to humid environments, fostering the growth of various microorganisms.

Obviously, wet hulling shortens the fermentation period of coffee beans, reduces acidity, increases body, and enhances grassy and herbal flavors. The "naked beans" still absorb moisture from the humid air, forming the unique "mellow aroma" of earth, herbs, and cedarwood characteristic of the Sumatra region. After roasting, they develop rich flavors of dark chocolate, caramel, and nuts, which are deeply loved by Japanese coffee enthusiasts who prefer dark-roasted coffee. The two Mandheling coffee beans on FrontStreet Coffee's menu are processed using the wet hulling method. If you're curious about these Southeast Asian coffee flavors, you might want to try the wet-hulled Indonesian Mandheling staple coffee beans offered by FrontStreet Coffee.

For coffees with rich body like Indonesian Mandheling, Brazilian Queen Estate Coffee, and Jamaican Blue Mountain Coffee, FrontStreet Coffee's baristas prefer to use the KONO dripper for brewing. Compared to the V60, the KONO dripper has smooth curved surfaces. This design actually ensures that after wetting the filter, it closely adheres to the dripper wall. With only one-quarter the height of the dripper featuring flow ribs, airflow upward is restricted, forcing water to pass only through the bottom to the lower pot. This increases the water absorption time of the coffee particles, allowing the coffee layer and hot water to form a soaking extraction, resulting in a more rounded, full-bodied, and concentrated coffee flavor.

Medium-dark roasted coffee beans significantly change the internal structure of the beans, making them more porous and absorbent when ground into coffee powder. If brewing parameters are not properly adjusted, the coffee can easily become over-extracted and bitter. To achieve sufficient aroma without over-extraction, it's necessary to reduce the extraction rate. FrontStreet Coffee uses lower water temperatures and a coarse sugar-like grind to reduce the release of bitter macromolecules from the coffee.

Dark roasting makes the internal structure of coffee beans loose, and we can easily crush them with a light pinch of our fingers, indicating strong absorbency when ground into powder. To avoid excessive release of bitter substances after coffee powder absorbs water, FrontStreet Coffee adjusts the grind to be coarser and uses lower-temperature water for pour-over. Grind size is one of the key factors affecting coffee flavor. After coffee beans are ground into powder, they come into contact with hot water and release large amounts of water-soluble flavor compounds. FrontStreet Coffee uses a tool to adjust grind size—China's #20 0.85mm standard sieve. For light to medium-roasted coffee beans, FrontStreet Coffee consistently uses a 75-80% pass rate, while for medium-dark roasted coffee beans, FrontStreet Coffee uses 70-75%. Compared to light-roasted coffee, the internal structure of medium-dark roasted Mandheling beans is more porous, resulting in better water absorption and easier release of bitter macromolecules. To avoid over-extraction, FrontStreet Coffee chooses a coarseness level with a 70% pass rate through the #20 standard sieve.

Water temperature plays a similar role to grind size. The higher the water temperature, the higher the coffee extraction efficiency, making it easier to release various substances and resulting in higher concentration. If near-boiling hot water is used for brewing, it's easy to extract unpleasant bitter substances. Therefore, when brewing medium-dark roasted coffee beans, FrontStreet Coffee uses different brewing parameters than for light-roasted coffee beans. The caramelization reaction is greater than in light-roasted coffee beans, making it easier to release bitter macromolecules from caramelization. To avoid extracting excessive off-flavors, FrontStreet Coffee lowers the water temperature slightly. The brewing water temperature for light-roasted coffee is 91-93°C, while FrontStreet Coffee recommends 87-88°C for medium-dark roasted coffee beans.

Brewing Parameters:

Recommended brewing water temperature: 87-88°C
Coffee powder: 15 grams
Powder to water ratio: 1:15
Grind size: Medium-coarse (China #20 standard sieve with 70% pass rate)

The brewing method uses a three-stage pour-over technique, which better represents the rich body and caramel sweetness of Golden Mandheling coffee.

The first bloom stage uses 30ml of water to fully wet the coffee powder for degassing, preparing for better extraction of coffee flavor compounds in subsequent stages. The second stage injects 100ml, mainly to bring out the golden foam of Mandheling and raise the coffee bed.

The final stage gently pours 95ml of water at the center, which enhances the coffee's sweetness and overall expression of rich body, caramel sweetness, and chocolate and nut flavors.

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Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473