How Does Wet Hulling Shape Sumatra Mandheling Coffee?

Mandheling is neither a variety nor a region; the name comes from an ethnic group in the northern highlands of Sumatra. Its signature goat-hoof shape appears because semi-dry green beans have their mucilage and parchment removed while still soft, so mechanical friction cracks them unevenly. Those gaps are not defects, and the cup shows a solid body, herbal and earthy notes, low acidity and a long finish.

Sub-regions such as Lintong, Lake Toba, Lake Tawar and the Gayo Mountains give different profiles, and the local varieties TimTim and Ateng appear across them. Golden Mandheling and Lintong Mandheling are the two most common labels. Brewing works well with calibrated water temperature, grind size, a chosen coffee-to-water ratio and a three-pour technique, which together keep the heavy body without over-extraction.

Mandheling is a classic name that coffee lovers cannot avoid; it is neither a variety nor a region, but the name of an ethnic minority on the northern highlands of Sumatra. This article begins with the origin of the name Mandheling and the geography of the Sumatra producing region, sorts out the differences between sub-regions such as Lintong, Lake Toba, Lake Tawar and the Gayo Mountains, explains how the wet-hulling process creates the signature goat-hoof bean appearance, and clarifies the actual meaning of the Indonesian coffee varieties TimTim and Ateng. It also fully shares Front Street Coffee's pour-over parameter system, covering water temperature, grind size calibration, coffee-to-water ratio selection and the three-pour technique, and finally summarizes the flavor profiles of Golden Mandheling and Lintong Mandheling, making it suitable reading for coffee lovers who want a systematic understanding of Mandheling.

Anyone who has handled coffee beans may have noticed that Mandheling beans are relatively large and often have a goat-hoof shape, which is one of its most recognizable labels. The reason for this is related to the wet-hulling process: when semi-dry, semi-wet green beans have their mucilage and parchment layer removed, their texture is uneven in hardness, so they are easily damaged and cracked by mechanical friction, forming goat-hoof-like gaps. Such beans are not defects. Its body is solid, smooth on entry, with herbal notes and an earthy, deep aroma, a long finish, and virtually no perceptible acidity.

The three characters "曼特宁" are neither the name of a coffee variety nor a place name of a producing region, but the name of an ethnic minority living on the northern highlands of Sumatra Island【SUMATERA ISLAND】. During World War II, when the Japanese army occupied Indonesia, a soldier drank an extremely aromatic cup of coffee in a cafe and asked the owner what coffee it was, but the owner mistakenly thought he was being asked where he was from, and answered "Mandheling." After the war ended, this soldier returned to Japan, recalled the flavor he had tasted in Indonesia, and had someone ship 15 tons of coffee beans from Indonesia to Japan. The result was a huge hit, and the name Mandheling spread from there.

Indonesian Sumatra Coffee Producing Region

Mandheling coffee is also called Sumatra coffee because it grows on the Indonesian island of Sumatra. Sumatra is Indonesia's largest island and the sixth-largest island in the world. It lies to the northwest of Indonesia, stretching from northwest to southeast, with the equator running through its center. The island's terrain is high in the northwest and low in the southeast, with the Barisan Mountains running through it. It is mainly planted with Arabica and is the core producing region of Mandheling; the southeast is mostly plains or swamps, mainly planted with Robusta varieties. The island has more than 90 volcanoes and numerous volcanic lakes, providing nutrient-rich soil for coffee. Due to its geographical location, Sumatra has Indonesia's earliest harvest season—from November to March of the following year.

Lintong Mandheling comes from the Lintong highlands in north-central Sumatra, near Lake Toba, and can be understood as the regular version of Sumatra Mandheling.

Lake Toba is located in the central part of North Sumatra Province. In 1888, Dutch colonists introduced "Java Mandheling" northward to the Lake Toba area, creating the modern legend of Mandheling.

Lake Tawar is located in the central part of the Special Region of Aceh, at the northernmost tip of Sumatra Island, with an area less than one-tenth that of Lake Toba.

At present, the best-quality beans in the Sumatra region come from the Gayo Mountains, mostly grown from old tree varieties. The Gayo Mountains are located in the Aceh producing region of North Sumatra Province, at an altitude between 1,500 and 2,500 meters, and most local coffee farmers are indigenous Gayo people. This place has ideal conditions for coffee growing—high altitude, fertile soil, sufficient rainfall, and Lake Tawar provides abundant water. Moreover, coffee in this area is generally cultivated organically, without chemical fertilizers, and is regarded as a green coffee production area in the world, so Gayo coffee is also often called green coffee or Gayo organic coffee.

Front Street Coffee's Golden Mandheling coffee from the new crop season comes from the Gayo Mountains in Aceh, North Sumatra, and is a Golden Mandheling coffee bean produced by PWN. Golden Mandheling has stricter quality control: first, the beans are required to reach 19 mesh, full and uniform in size, belonging to the highest grade G1. PWN's beans are darker green in color and regular flat beans in shape. In addition, they must undergo one machine sorting and three manual hand-sortings to ensure that among a 300g green bean sample there are no more than 3 defective beans.

Mandheling Coffee Varieties

Indonesia has a very long history of coffee cultivation. In the early period, Arabica was dominant, but later, affected by leaf rust, about 90% of Indonesia's exported coffee beans are currently Robusta, with Arabica accounting for only 10%. Front Street's Lintong Mandheling coffee variety is labeled TimTim Ateng, while the variety of Golden Mandheling coffee is written as Ateng. In fact, TimTim refers to Timor, an Arabica variety with Robusta lineage; Ateng is Catimor, a cross between Caturra and Catimor. These names are merely local customary terms.

Mandheling Coffee Beans Processing Method

Mandheling coffee beans use the wet-hulling processing method. Some customers find the appearance of Mandheling beans not very attractive because both ends have gaps, commonly known as goat-hoof beans, but these are not defective beans. Indonesia is located near the equator and has a tropical rainforest climate, and coffee beans produced in large quantities mostly use the relatively rough wet-hulling process. The wet-hulling method greatly compresses the entire processing flow, but removing the parchment layer in a semi-dry state requires considerable friction, so the green beans are easily crushed and damaged, especially at both ends, thus forming small gaps.

Front Street's Brewing Parameters for Mandheling Coffee

Front Street Coffee believes that to brew a good pot of coffee, one should mainly start from four aspects: water temperature, grind size, coffee-to-water ratio, and brewing technique.

1. Water Temperature

Front Street Coffee adjusts the water temperature according to the roast level when making pour-over. During roasting, substances inside the coffee beans are lost as the roast deepens, so for dark-roasted beans, the temperature is appropriately lowered to avoid extracting too many unwanted flavors. For medium-light roasted beans, Front Street Coffee recommends a water temperature of 90-91°C; for medium-dark roast, 88-89°C is recommended.

For this Mandheling coffee bean, the flavor is known for its full body. To highlight its full-bodied character, Front Street Coffee uses a medium-dark roast.

2. Grind Size

The grind size of coffee is also related to the roast level. Grind size refers to the size of the coffee particles, and it affects the contact time between coffee and water. The finer the coffee powder, the more substances can be extracted in the same amount of time, but over-extraction is also easy; conversely, the coarser the coffee powder, the fewer substances are extracted in the same amount of time, but under-extraction is likely.

Because everyone has a different grinder, the parameters will also differ. Here Front Street suggests buying a No. 20 cupping calibration sieve with an aperture of 0.85mm. Take 10g of coffee beans, set a rough grind size and grind them into powder, pour into the sieve and sift, then weigh the sifted coffee powder (be sure to sift until no coffee powder can pass through the sieve).

A pass rate of 70%-75% (7-7.5g sifted from 10g powder) is the most suitable grind size. The grind size standard for pour-over is: light roast 80%, medium-dark roast 75%. If the sifting rate exceeds the suitable range, adjust coarser; if it does not reach it, adjust finer.

3. Coffee-to-Water Ratio

This is the pour-over coffee water-to-coffee ratio extraction parameter flavor difference obtained by Front Street Coffee based on the SCAA Golden Cup extraction theory.

【Bold Taste】1:10～1:11, i.e. 1:12.5～1:13.5 under the Golden Cup standard 【Moderate Taste】1:12～1:13 (i.e. 1:14.5～1:15.5 under the Golden Cup standard) 【Light and Fresh】1:14～1:16 (i.e. 1:16.5～1:18.5 under the Golden Cup standard)

When the ratio of coffee bean grams to brewing water is between 1:14.5 and 1:15.5, it most easily falls within the golden range of 18%-22% Golden Cup extraction yield and 1.15%-1.35% concentration.

Therefore, Front Street Coffee suggests using the foolproof 1:15 coffee-to-water ratio when brewing this Mandheling coffee.

4. Brewing Technique

Finally, the pour-over technique is also crucial. Common methods include the three-pour method, one-cut flow, and drip method. Here Front Street Coffee suggests that beginners use the three-pour method to brew, because this technique is suitable for light-roasted, medium-light, and medium-dark roasted coffee beans. The staged extraction of the three-pour method can clearly present the front, middle, and back flavors of the coffee, and relatively better ensure complete flavor expression. Next, Front Street Coffee will teach everyone how to perform three-pour pour-over coffee brewing.

Three-Pour Brewing Technique: (Front Street's three-pour brewing method for Mandheling coffee)

Front Street believes that the fine flavor of Mandheling coffee lies in balanced acidity, sweetness and bitterness, and high body. For roasting, Front Street chose medium-dark roast, which can highlight the coffee beans' nutty, pine, and herbal notes. Using a KONO dripper can provide better body. Water temperature 88°C, coffee-to-water ratio 1:15, coffee dose 15g, grind size (75% pass rate on the China No. 20 standard sieve).

First Pour: Blooming (to help degassing)

First, wet the KONO dripper so the filter paper fits the dripper more tightly, pour out the water in the sharing pitcher, and at the same time add 15g of coffee powder, then bloom with 30g of water for 30s. Many coffee lovers do not understand why pour-over coffee needs blooming. In fact, blooming is because coffee beans undergo a series of chemical reactions and physical changes during the roasting process from green beans to roasted beans. After reaching a certain degree of roasting, a large amount of gas (mostly carbon dioxide) accumulates inside the coffee beans.

Generally speaking, the fresher the beans and the closer to the roast date, the more bubbles usually appear during blooming. Dark-roasted beans also release more gas during blooming than light-roasted beans. Front Street Coffee's coffee beans are all freshly roasted, so customers are generally advised to rest the beans for three days first, allowing the coffee beans to release carbon dioxide first, so that instability and under-extraction can be avoided during brewing.

After the gas is released during blooming, the coffee particles can absorb water evenly, which helps subsequent extraction be uniform. A good bloom can both allow the coffee powder to degas quickly, fully and evenly, and allow the coffee powder to contact water quickly, helping extraction be more uniform. These are precisely the purpose and significance of blooming in pour-over coffee.

Second Pour

After blooming for 30s, proceed to the second pour, starting from the center and pouring in circles with a small stream until 125g, then stop. To make the water column's penetrating force concentrated, the circular movement range should be small, about the size of a one-yuan coin, and then circle outward. From the start of the second pour, pay attention to the water amount and try not to exceed the height of the coffee bed; that is, when the water column circles to near the filter paper, you can stop pouring.

Third Pour

When the coffee bed drops to half the height of the dripper, pour the second stage in the same manner until 225g. After all dripping is completed, remove the dripper.

From the start of the third pour, observe the extent of the water level dropping. Likewise, start pouring in circles from the center, and do not let the water amount exceed the height of the coffee bed. At this time you will also see that the foam has covered the entire surface. The third pour should increase the tumbling of coffee particles, causing all settled particles to turn over, thereby dissolving soluble substances.

The tumbling particles will gradually settle as pouring stops. At this point, rely on the flow rate caused by the dropping water level to make the coffee particles rub against each other. Therefore, once pouring stops, the coffee powder particles will sink and cause clogging, so pay special attention to the rhythm of pouring. If pouring is interrupted too many times, it is equivalent to letting the coffee powder particles remain soaked in water, which will cause astringency and off-flavors in the tail-end extraction.

Start timing from the beginning of pouring; the extraction time is 2'00". Next, pick up the entire cup of coffee and shake it evenly, then pour it into a cup and taste.

【Front Street PWN Golden Mandheling Coffee Flavor】: The coffee has varied layers overall, full-bodied and clean, with rich nutty and caramel aroma, chocolate notes, a lasting finish, and high balance.

【 Lintong Mandheling Coffee Flavor】: On entry it has a rich herbal aroma, black chocolate, caramel, and a sweet aftertaste.

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The above content is compiled by CoffeeHunters, a coffee news website.