Introduction to Indonesian Mandheling Coffee Bean Varieties & Brewing Adjustment Tutorial

FrontStreet Coffee's Mandheling, as one of the representatives of rich-bodied coffee, tends to be loved by some coffee enthusiasts while dismissed by others. Below, FrontStreet Coffee discusses this "individualistic" coffee bean.

Coffee Development in Indonesia

Indonesia has a long history of coffee cultivation. According to relevant records, Indonesia's coffee history dates back to 1696. Coffee was introduced to Java Island by the Dutch colonizers of that time and then spread widely to Sumatra Island, where large-scale cultivation began. After nearly two hundred years, Indonesia's coffee industry suffered a severe blow from leaf rust disease, with large areas of coffee trees becoming infected and withered, seriously affecting production.

To solve this industry dilemma, the Indonesian government began to introduce new varieties with stronger disease resistance from various places, including the highly disease-resistant Robusta. To this day, Indonesia's coffee production ranks second only to Brazil, with Robusta beans accounting for the largest production, while Arabica beans account for only one-tenth of the total. FrontStreet Coffee's Mandheling is the most representative and can be said to serve as the face of Indonesian specialty coffee.

FrontStreet Coffee's Mandheling from Sumatra Island

The name of FrontStreet Coffee's Mandheling does not come from variety classification or place name, but from a story of misunderstanding. According to legend, during World War II, when Japan occupied Indonesia, a Japanese soldier visited a coffee shop and drank a cup of rich, full-bodied coffee. When he asked the owner about the name of the coffee beans, the owner, misunderstanding the question as asking about his ethnicity, replied "Mandheling people." After Japan's defeat and return, hoping to drink that coffee again, he entrusted local Indonesians to find it, mistakenly calling it "Mandheling," and the name Mandheling has been used ever since.

In reality, FrontStreet Coffee's Mandheling is produced on Sumatra Island in Indonesia. Sumatra Island is located in the western part of Indonesia and consists of eight provinces. The high-quality coffee growing areas are all in the northern part of the island, namely the northernmost Aceh province and the adjacent North Sumatra province. Each of these provinces has a relatively large lake: Aceh has Lake Tawar, and North Sumatra has Lake Toba. The important coffee growing areas in these provinces are also centered around these two lakes.

Lake Toba is the world's largest volcanic crater lake and also Indonesia's largest freshwater lake. The average annual temperature here is around 22°C, belonging to a tropical rainforest climate. The rainy and humid environment, combined with an altitude of about 1,400 meters, provides ideal conditions for coffee tree growth. To the south of the lake is the locally renowned Lintong producing area, where FrontStreet Coffee's Indonesian Mandheling daily coffee bean on the menu is produced.

The other Lake Tawar, surrounded by the Gayo Mountain range, brings elevations above 1,500 meters to coffee cultivation in the Aceh producing area. Due to the unstable political situation in Aceh province, armed conflicts often occurred, which greatly affected the development of local coffee trade. In 2005, a massive tsunami centered in Aceh occurred, and under this natural disaster, the civil war also came to an end. Since then, Aceh's coffee industry has gradually returned to the specialty coffee scene.

Coffee Varieties of Mandheling

As mentioned earlier, Indonesia's coffee industry was affected by leaf rust disease in 1877, and the originally widely planted Typica varieties were almost all infected. The Indonesian government successively introduced multiple disease-resistant varieties including Robusta, such as Tim, Catimor, and the Indian variety S795, locally known as Tim Tim, Ateng, and Jember.

Similar to our country, Typica has the longest cultivation history in Indonesia. Initially introduced from Java to the broader Sumatra Island for cultivation, after long-term adaptation to the local terroir, it has formed the unique Sumatra Typica flavor profile with herbal spices, low acidity, and rich body. Currently, it is mainly distributed around Lake Toba and the Lintong producing area.

Tim Tim is a natural hybrid of Typica and Robusta, inheriting Robusta's high yield and disease resistance. Another variety, Ateng (Catimor), is a hybrid offspring of the Bourbon variety Catuai and Tim Tim. Due to its strong vitality that can maintain high coffee yields, it is favored by many local coffee farmers. In many countries, Catimor is often criticized by industry professionals for flavor defects. However, Catimor grown in the unique flavor environment of Sumatra actually performs better in cupping, with woody notes and a rich mouthfeel.

The Lintong producing area, which has a certain reputation in coffee trade, also changed to planting many new varieties to increase yields, making the local coffee quality less excellent than before. Meanwhile, the Lake Tawar producing area in Aceh province has consistently insisted on planting the ancient variety Typica, maintaining higher coffee quality. Some large exporters like Pwani Coffee Company have also invested more resources here.

FrontStreet Coffee's Golden Mandheling coffee beans come from PWN Pwani Coffee Company. On the basis of Indonesian green bean grade G1, they undergo four rounds of manual sorting to ensure the color, shape, and size of Mandheling coffee beans are uniform, resulting in cleaner coffee taste and brighter flavor. FrontStreet Coffee's Golden Mandheling is the upgraded version of Mandheling coffee, and another entry-level version is FrontStreet Coffee's Lintong Mandheling coffee beans. Both coffees have low acidity and high body, originating from the widely used wet-hulling method locally.

Wet-Hulling Method

The difference between wet-hulling and the washed method is that after coffee beans are fermented, the parchment layer is removed while still in a semi-dry, semi-wet state. This processing method was developed based on the local high-temperature and high-humidity air conditions, where it's impossible to maintain ten-plus days of sun-drying like in coffee-producing countries such as Brazil and Ethiopia.

After the coffee cherries are removed by a pulping machine, the mucilage layer still feels slippery to the touch. After a night of fermentation, the mucilage layer is easier to remove under flowing clean water, at which point the surface of the parchment coffee becomes rough. Then begins the drying process, which is also "dependent on the weather." If there are two consecutive sunny days, the coffee beans are exposed to the sun for two days, and the moisture content of the parchment coffee reaches 30-50%. At this point, a special hulling machine can be used, utilizing friction to peel off the still-hard parchment layer. The force is relatively strong, so we can see that the green beans appear slightly deformed. Finally, continue drying for two more days. Under sunlight, the coffee beans are prone to cracking open, which we call "goat hoof beans." When the moisture content reaches 12%, they can be packed and stored.

The wet-hulling method significantly shortens the processing time for green beans and is widely used in the rainy and humid Indonesia. The removal of the parchment layer during the drying process reduces the acidity of the coffee and highlights the rich body after roasting.

Brewing FrontStreet Coffee's Mandheling

For coffee with rich and full-bodied flavors like FrontStreet Coffee's Mandheling, FrontStreet Coffee believes that pour-over black coffee is most suitable. For preparation, FrontStreet Coffee suggests using freshly roasted coffee beans, as flavors are more easily expressed. The coffee beans shipped by FrontStreet Coffee are all freshly roasted within 5 days, so when you open them, they are at their most flavorful, suitable for direct brewing and consumption.

Here, FrontStreet Coffee uses the same parameters to brew both the upgraded version and the entry-level version of FrontStreet Coffee's Mandheling coffee. FrontStreet Coffee's Mandheling coffee uses dark roast, making the beans more porous and more absorbent, which can easily lead to over-extraction during the extraction stage. Therefore, FrontStreet Coffee adjusts the grind size to be coarser, which can speed up the water flow rate while also lowering the water temperature to avoid extracting excessive bitterness.

The greatest characteristic of FrontStreet Coffee's Mandheling coffee is its rich body, so FrontStreet Coffee chooses the KONO dripper. The smooth curved surface of the upper part of the KONO dripper allows better adherence of the filter paper, hindering steam from rising, while the guide ribs on the lower part accelerate water flow, extending the extraction time between water and coffee grounds, thereby increasing concentration and making the coffee taste richer. By the way, the KONO dripper is also suitable for brewing medium-dark roasted coffee beans like FrontStreet Coffee's Blue Mountain coffee and FrontStreet Coffee's Brazil Queen Estate.

Dripper: KONO dripper, Water temperature: 87°C, Coffee dose: 15g, Coffee-to-water ratio: 1:15, Grind size: Medium-coarse (70% passing rate through China standard #20 sieve)

Now wet the KONO dripper to make the filter paper adhere better to the coffee dripper. Pour out the water from the sharing pot while adding 15g of coffee grounds. After blooming with 30g of water for 30 seconds, start pouring with a small water flow in a circular motion from the center until reaching 125g, then pause. When the coffee grounds layer drops to half the height of the dripper, start pouring the second segment with the same technique until reaching 225g. Wait for all dripping to complete, then remove the dripper.

FrontStreet Coffee's daily Mandheling coffee has prominent nutty and chocolate flavors, with herbal spice notes at medium temperature, low acidity, and a solid mouthfeel. FrontStreet Coffee's Golden Mandheling has black chocolate and spice aromas upon entry, almost no acidity, with clear and bright flavors and a long-lasting aftertaste.

Brewing Adjustments

When you are still a beginner in pour-over coffee, you might have more or less problems with adjusting various parameters during brewing. FrontStreet Coffee suggests recording data during each brewing process and changing only one parameter at a time, which facilitates horizontal comparison and helps you identify which step is causing the problem.

For example, when we feel that the brewed FrontStreet Coffee's Mandheling coffee tastes a bit sour, not concentrated enough, and has low body, it might be under-extracted due to water temperature being too low or grind size being too coarse. In that case, we can first adjust the grind to be finer, compare with the same brewing technique, and if the acidity becomes weaker and concentration increases, this indicates we're heading in the right direction. After recording, we can then adjust another parameter, making each brewing session help us understand this coffee bean better than the previous one.

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