Why Does Indonesian Mandheling Coffee Use the Wet-Hulled Method?

Introduction to Dark Roast Coffee and Mandheling Varieties

When it comes to dark roast coffee, many people think of Asian coffee beans, most commonly those from Indonesia. Mandheling coffee is particularly famous for its rich, mellow flavor. At FrontStreet Coffee, we currently offer two varieties of Mandheling coffee: Lintong Mandheling and Gold Mandheling. The Gold Mandheling coffee beans are processed using the wet hulling method, which yields flavors of toasted bread, pine, caramel, and cocoa when brewed. The taste is rich and mellow, with varied layers, intensity, and balance, finishing with a persistent caramel sweetness.

Why Wet Hulling is Common in Indonesian Coffee Processing

Customers who frequently purchase Mandheling coffee often ask why the wet hulling method is commonly used in coffee processing. The answer lies in adaptation to local conditions. Indonesia, the world's largest archipelagic country, is located in the tropics with predominantly tropical rainforest climate. The average annual temperature ranges between 25-27°C, with most regions experiencing high temperatures, abundant rainfall, warm and humid conditions, short sunshine hours, and year-round humidity between 70%-90%. Consequently, the rainy weather makes it difficult for Indonesia to dry coffee cherries through prolonged sun exposure like other countries. Additionally, during the washing process, after coffee cherries ferment in water, there is often insufficient sunlight to dry them properly.

The Origins and Process of Wet Hulling

Thus, the wet hulling method (known as Giling Basah in Indonesian) was developed. This processing method is also called "semi-washed processing" as it resembles traditional washing but with distinct differences. The initial stages of wet hulling are similar to washing - after fermentation, the beans undergo brief sun exposure, and while still high in moisture content, the parchment layer is removed directly before final drying and hulling. This approach significantly reduces the sun-drying time for coffee beans, allowing them to dry more quickly.

Furthermore, when Indonesia was under Dutch colonial rule, coffee cultivation and export were controlled by the Dutch. The wet hulling method effectively reduced coffee processing time while decreasing labor investment, resulting in greater profit margins. Consequently, wet hulling was widely promoted throughout Indonesia.

Step-by-Step Wet Hulling Process

Today, after harvesting, coffee cherries first undergo floatation to select out lower quality beans. Then machines are used to remove the outer skin and pulp, leaving coffee beans with parchment and mucilage layers placed in water tanks for fermentation. During this period, fermentation decomposes the mucilage layer of the beans, concluding after approximately 12-36 hours to obtain parchment-covered coffee beans. The parchment-covered beans are then placed under the sun for drying, depending on weather conditions, until the moisture content drops to 30%-50%. After drying, a hulling machine removes the parchment layer from the beans, and finally, the beans are dried until their moisture content reaches 12%.

Challenges and Evolution of Wet Hulling

Although this method perfectly suits the local climate and accelerates the processing workflow, it has drawbacks, particularly the tendency to produce "horse hoof beans." The process of using a hulling machine to remove the parchment layer is quite violent, making it easy to crush or damage the raw coffee beans while removing the parchment, especially at both ends of the beans. Some coffee beans develop cracks resembling horse hooves, earning them the name "horse hoof beans." However, when purchasing PWN Gold Mandheling coffee beans today, "horse hoof beans" are less common, suggesting improvements in the processing workflow.

PWN Gold Mandheling: Premium Quality

Today's PWN Gold Mandheling is produced by Pwani Coffee Company. The company has acquired almost all the best growing regions in Indonesia, so most coffee beans from PWN Company are specialty grade. Furthermore, PWN Company has registered "Gold Mandheling" as a trademark, meaning only coffee produced by PWN Company can be considered genuine "Gold Mandheling."

After acquiring raw coffee beans, PWN also arranges for three rounds of manual selection to remove defective, small-sized, and aesthetically unappealing beans. What remains are large, plump coffee beans with minimal defects, which improves the coffee's cleanliness. Consequently, Gold Mandheling commands a significantly higher price than other Mandheling varieties.

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