How Should Mandheling Coffee Beans Be Roasted? What is Sumatra Mandheling Coffee Wet Hulling?

Introduction to Sumatra Coffee

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Commonly known as Mandheling, Sumatra coffee originates from Sumatra Island in Indonesia. This island is Indonesia's second-largest island and the world's sixth-largest island, with an area of 470,000 square kilometers—thirteen times the size of Taiwan!

Sumatra Coffee Growing Regions

Although Sumatra Island is large, not the entire island produces coffee. Large-scale coffee tree cultivation is mainly concentrated in the two northernmost provinces among the island's eight provinces: Aceh Province and North Sumatra Province. Aceh coffee is primarily produced in the Gayo Mountain area around Lake Tawar, where most farmers are local Gayo indigenous people. Meanwhile, North Sumatra Province's coffee mainly comes from the Sidikalang production area on the west side of Lake Toba (the world's largest super-caldera lake) and the Lintong production area on the south side, where local farmers are mostly composed of Batak indigenous people.

Unique Processing Methods

Sumatra coffee's production system is unique: there are very few large coffee estates on the island, replaced instead by tens of thousands of small farmers. These small farmers not only grow and harvest coffee themselves but also remove coffee seeds with pulp from berries and sun-dry them in every household. However, when the green beans are not yet completely dry, the seed shells are removed... and collected by small, medium, and large purchasers, dried in batches, and then transferred to exporters. When they reach exporters, sometimes they still need to be sun-dried again until moisture content meets standards before entering the bean selection room, where defective beans and impurities are manually removed, graded by screens, and then packaged for export.

This unique semi-washed processing method is locally called Giling Basah, also known as wet-hulling. This system allows coffee beans to dry at a relatively slow speed, thus creating the characteristic rich texture of Sumatra coffee. Although it requires significant human labor for subsequent defect removal operations, the resulting full-bodied style is unique in the world!

Golden Mandheling

Golden Mandheling: Mainly produced in Java, Sulawesi, and Sumatra of Indonesia. Unlike coffee from other regions of the world, Mandheling is not famous for its growing region but for its harvesting and processing methods.

Golden Mandheling enjoys a prestigious position in the coffee industry. The semi-washed (also known as dry processing) Sumatra variety is the most outstanding bean in the Indonesian coffee world. Purely hand-picked, it is mellower than regular Mandheling, combining low-acidity sweet and bitter flavors with great depth. Besides the rich and rugged characteristics that Mandheling coffee should have.

Gayo Production Region

Sumatra Island distinguishes between "Aceh Province Gayo Mountain" and "North Sumatra Province Lake Toba" and "Lintong Lasuna" in the northern part of the island, and the "Gayo production area" around the scenic Lake Tawar in Bengkulu Province in southern Sumatra. The world-famous Golden Mandheling coffee comes from the Gayo production area of Lake Tawar.

The characteristics of the Gayo production area include abundant rainfall with an annual average of about 2200mm and an average altitude between 1100-1400 meters, plus volcanic soil favorable for coffee cultivation.

This production area usually involves independent small farmers in coffee cultivation work, using shade trees to improve coffee quality. Unlike Lintong Mandheling from another Indonesian specialty coffee origin, Gayo production area coffee has relatively calm and restrained characteristics. Therefore, Golden Mandheling not only possesses thick creamy texture and rich chocolate dried fruit flavors but also reduces the proportion of defective beans due to farmers' tedious bean selection procedures.

FrontStreet Coffee Roasting Recommendations

Since Mandheling beans themselves have relatively high acidity, FrontStreet Coffee usually chooses dark roasting to reduce its acidity and highlight its rich body as well as cocoa and nut flavors.

Indonesian coffee beans are mostly mixed cultivation of Typica, Typica varieties, and Arabica local varieties containing Robusta genes. In terms of roasting, it's suitable to use medium heat for slow roasting to achieve consistent dehydration. Using standard roasting methods, set air damper to 20% when adding beans, 50% at the browning point, and 80% at first crack. Heat can be fine-tuned according to ROR conditions with adjustment ranges around 5%. It's recommended to roast until the beginning of second crack, with medium-dark roast degree, which can effectively remove the earthy taste of Indonesian wet-hulled coffee and increase chocolate flavor and body.

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