How Does the Coffee Bean Process Shape Mandheling?

Mandheling is a Sumatran coffee known for full body, low acidity, and spicy, herbal notes. The wet-hulled coffee bean process, called giling basah, removes parchment while the bean is still moist, which produces the dense, low-acid profile and the distinctive "goat hoof" shape. The article also compares Lintong Mandheling with Front Street PWN Golden Mandheling in origin, variety, and flavor.

Lintong refers to coffee grown southwest of Lake Toba, mostly on smallholder plots at 1,100 to 1,600 meters, using Timtim and Ateng varieties. Brewing comparisons cover pour-over, AeroPress, siphon, and French press, since each device extracts the heavy body and herbal notes differently. Dark roasting brings out lingering bitterness and an elegant sweetness, a style mellow coffee roasters often favor for Sumatra lots.

Mandheling is one of the most iconic coffees of Sumatra, Indonesia, known for its full body, low acidity, and spicy, herbal notes. This article explores the differences between Lintong Mandheling and Front Street PWN Golden Mandheling in terms of origin, variety, processing method, and flavor, and explains in detail how the Sumatra wet-hulled process shapes its unique character, including the formation of "goat hoof" beans and defect control. At the same time, Front Street Coffee compares PWN Golden Mandheling brewed four ways—pour-over, AeroPress, siphon, and French press—presenting the flavor expression and extraction recommendations for each device, helping coffee lovers gain a more comprehensive understanding of Mandheling.

To learn more about specialty coffee, follow our WeChat official account: Front Street Coffee (FrontStreet Coffee).

Mandheling comes from Sumatra, Indonesia, in Asia, so it is also often called Sumatra coffee. Its main producing regions include Java, Sulawesi, and Sumatra, with Sumatra being the most famous for Mandheling.

Among the fine traditional Arabica coffees produced in northern Sumatra, the most outstanding quality is often marketed under the names Lintong and Mandheling. Strictly speaking, Lintong refers to coffee grown in a relatively small area southwest of Lake Toba in the Lintong administrative district. The local coffee-growing areas are fairly scattered, distributed across high-altitude, rolling clay plateaus rich in ferns. Lintong coffee is not shade-grown and uses no chemicals, and is almost entirely owned by smallholders.

Front Street Coffee — Indonesian Sumatra Lintong Mandheling

Origin: Lintong region, Sumatra, Indonesia

Altitude: 1100-1600m

Processing method: Wet-hulled

Variety: Timtim, Ateng

Flavor description: Baked toast, nuts, caramel, herbs, chocolate

Front Street Coffee believes that Mandheling coffee has a rich aroma, a solid and full body, and low acidity, making it deeply intriguing. When dark-roasted, you can experience both its lingering bitterness and its elegant sweetness, perceiving its unique mellow fragrance through both smell and taste.

Based on its understanding of Mandheling coffee, Front Street's roasters aim to maximize the expression of Mandheling's flavors, preserving Mandheling's own style while also suiting most people's tastes. Every specialty coffee shop has its own characteristics; Front Street hopes to bring its unique understanding of coffee to present the best Mandheling to customers while retaining the characteristics of Front Street Coffee. Front Street Coffee currently sells two Mandheling coffees: one is the Lintong Mandheling described above, and the other is the Golden Mandheling from the PWN company in the Gayo Mountain area of Aceh.

Front Street Coffee — Indonesian Sumatra Front Street PWN Golden Mandheling coffee beans

Origin: Gayo Mountain, Aceh, Sumatra, Indonesia

Altitude: 1100-1600m

Processing method: Wet-hulled

Variety: Ateng

Flavor description: Spices, nuts, pine, caramel, herbs, chocolate

The difference between the two is that Front Street PWN Golden Mandheling coffee beans undergo at least three rounds of hand-sorting after harvesting and drying, ensuring the bean size reaches 18 or above. With fewer than 3 defective beans (per 300g green bean sample), it belongs to the highest grade, G1. PWN beans are darker green in color with a neat, flat bean shape.

What are the differences between Mandheling coffee beans at different roast levels?

To find out, Front Street Coffee tested light-roasted, medium-dark-roasted, and dark-roasted Mandheling coffee beans using drip extraction (pour-over). For one serving, grind size and water temperature were adjusted slightly according to the roast level.

1. Light roast: 80% passing through a standard No. 20 sieve, water temperature 90°C, water-to-coffee ratio 1:15

2. Medium-dark roast: 75% passing through a standard No. 20 sieve, water temperature 88°C, water-to-coffee ratio 1:15

3. Dark roast: 70% passing through a standard No. 20 sieve, 86°C, water-to-coffee ratio 1:15

The test results are as follows:

1. Light roast: At this roast level, the Mandheling has a stronger fruity acidity and is slightly bitter; the fruity acidity is pronounced but pleasant on entry, with a mouth-watering sensation on both sides of the mouth, and average smoothness.

2. Medium-dark roast: Very well balanced, rich and full-bodied, with more pronounced bitterness, more prominent chocolate and slight sweetness, obvious licorice aroma, weak fruity acidity, better smoothness than the light roast, and a strong aroma, with the fruity acidity notably enhanced.

3. Dark roast: Almost no acidity, very heavy bitterness; if roasted over direct fire, improper roasting can also produce a burnt taste.

All coffee beans sold by Front Street Coffee are freshly roasted and shipped within 5 days of roasting. The optimal flavor window for freshly roasted coffee beans is 30-35 days after roasting is completed.

The darker the roast, the more carbon dioxide is produced inside the coffee beans. After roasting is finished, the beans are rich in carbon dioxide, so don't rush to drink them; let them rest for 3-5 days (counting from the roast date) to allow the beans to release some carbon dioxide in their original packaging, reducing uneven extraction caused by excessive carbon dioxide bubbles during brewing.

Mandheling coffee bean processing method — Sumatra wet-hulled process

March to May and September to December each year are the harvest seasons for Sumatra Mandheling, and most coffee farmers now only harvest fully red coffee cherries. After collecting the coffee cherries in the morning, the cherries are depulped and the mucilage removed in the afternoon; Sumatra's natural environment is superior, and most of the water used is mountain spring water.

1. Depulp the coffee cherries and place the parchment beans in a large bucket or tank filled with water, skimming off any defective floating parchment beans.

2. Briefly wash the dense parchment beans that sink to the bottom, then take them out and put them in a bucket or plastic bag for a short dry fermentation—that is, letting the mucilage sugars on the surface of the parchment ferment to enhance flavor. Basically, the longer the fermentation, the heavier the acidity. Fermentation time varies from person to person, generally only a few hours, but some estates skip the dry fermentation stage and directly sun-dry the parchment beans, which can stabilize acidity and improve the viscous mouthfeel, allowing the mucilage sugars to fully ferment and increase flavor; fermentation usually lasts between 12-36 hours, depending on the specific situation.

3. Sun-dry the parchment beans for one to two days until the moisture content reaches 30%-50%; the beans are still half-hard and half-soft. Then remove the parchment with a huller and sun-dry again to speed up drying. After about two days, when the moisture content reaches 12%-13%, the coffee beans are collected into woven bags, usually 40 kg and 80 kg per bag, and sent to the coffee processing factory for hulling—done, about four days in total.

The hulling process uses a huller to grind off the parchment, then the beans are sun-dried again until the moisture content reaches about 12%-15%. Then the coffee beans are sent for machine sorting to remove various impurities and are classified by bean size. Of course, accidents can happen. During hulling, the temperature of the coffee beans rises to 30-60°C and the parchment is completely destroyed, which may very likely trigger germination. The wet-hulled process also means that because the parchment is removed during processing, the beans are directly exposed to the air, so moldy and other defective beans are far more common than in washed and natural processes. Mold brings good flavors because coffee beans have four layers of protection: skin, mucilage, parchment, and silverskin.

In the washed process, only the first two layers are removed, retaining the parchment and silverskin for sun-drying. The wet-hulled process, however, removes the third and fourth protective layers midway, leaving the bean exposed to the sun—this is why Sumatra green beans have a blue-green color. Although wet-hulling shortens drying time, it also greatly increases the chance of contamination by mold, fungi, and yeast. Interestingly, contamination is not necessarily a bad thing; it depends on the strain. Dr. Martha Taniwaki of Brazil's Institute of Food Technology once tried infecting coffee beans with different strains and actually produced different flavors, including rotten, rancid, musty, woody, iodine, caramel, chocolate, and floral notes.

Academics believe that the woody, grass jelly, earthy, banana, and spicy notes of Sumatra coffee are likely created by mold. Roastery managers also often tell researchers that some mold-infected coffee beans taste better after being cleaned, while others are hard to swallow, depending on the strain. Perhaps it is possible to suppress bad molds and introduce good molds, controlling wild yeasts and cultivating elegant yeasts. But which molds help enhance coffee flavor and which are harmful remains to be further studied.

Goat hoof beans are the "ID card" of Mandheling coffee beans!

The wet-hulled process may trigger the germination mechanism of green beans, thereby affecting flavor. Because coffee beans that have lost all four protective layers are exposed, they are far more likely to trigger germination than washed beans that have only lost two layers—that is, activating the metabolism of sugars, proteins, and fats, all of which are coffee aroma precursors. In addition, the friction generated during hulling raises the bean temperature to 30°C-60°C, which also favors germination and mold growth.

Moreover, the half-hard, half-soft moist green beans are easily crushed by mechanical force when the parchment is removed, and the beans tend to crack into a goat-hoof shape—this is why Sumatra has a relatively high proportion of goat hoof beans. But whether goat hoof beans are good or bad remains undecided to this day. The key to control is keeping equipment and beans clean. Once hulled, drying must be quick to produce the full-bodied, low-acid, sweet Sumatra flavor; if control is poor, it may produce a dull Sumatra coffee, or even a moldy, earthy taste. If you prefer stronger acidity, Aceh can also be washed-processed, depending on customer demand.

Summary of the flavor characteristics of the wet-hulled process

To summarize the flavor of wet-hulled coffee, setting aside those subtle differences, we generally consider wet-hulled beans to have earthy, smoky, and chocolate notes. Full-bodied yet rather subdued, the low acidity comes from a shorter, weaker fermentation process and a longer drying time—if you've forgotten about wet-hulled fermentation, flip back and take a look.

As for the earthy and herbal flavors of wet-hulled beans, opinions vary widely. Some say it is related to the bean varieties used in wet-hulled regions (Timor line & Catimor line: with Robusta lineage), some say it is the result of organic interactions between green beans and the external environment, and some even say it is because there are too many defective beans!

There are many sources of defective beans in the wet-hulled process. First, natural defects present from the coffee cherry stage are unavoidable; another contributor is the hulling step, as well as spoilage during the transport of wet parchment beans, and damage to exposed green beans from sunlight and moisture. Another point is that irregular weather brings uneven drying speeds, which also detracts from flavor. This is why Mandheling requires so many rounds of hand-sorting.

Finally, Front Street Coffee summarizes the characteristics of various green bean processing methods.

Production risk: Wet-hulled / Natural > Washed / Honey > Semi-washed

Equipment cost: Washed / Semi-washed > Honey / Wet-hulled > Natural

Water usage: Washed > Semi-washed > Honey / Wet-hulled

How to brew Mandheling coffee beans?

Different devices and brewing methods produce different mouthfeels. Next, Front Street takes the store's PWN Golden Mandheling coffee beans as an example, using four different brewing methods to compare and analyze their flavor characteristics.

【Pour-over】

Flavor: Layered and varied, clean, balanced, with a long-lasting caramel sweetness in the finish

1. Choice of device: Hario V60

2. Water temperature: 88°C

3. Grind size: Medium-coarse (70% passing through a standard No. 20 sieve)

4. Roast level: Medium-dark roast

5. Bloom time: 25 seconds

Specific technique: 【Three-pour interrupted flow】For pour-over Mandheling, 15g coffee, ground on a Fuji Royal ghost burr grinder setting 4, V60 dripper, 88-89°C water. First pour 30g of water and bloom for 25s, pour to 104g and pause, wait until the water in the coffee bed drops to half before pouring again, pour slowly until 220g, discard the last 5g; water-to-coffee ratio 1:15, extraction time about 2:00.

For Mandheling, you can also use the volcano pour method, or a flannel filter or Kono!

Specific technique: High-temperature extraction, water temperature 90-92°C, pour a thin stream in the early stage within an area the size of a coin, pause, bloom, pause, bloom, keeping the coffee bed in a blooming state; bloom time 1:30, then finish with a fast heavy pour; total extraction time 2:30.

【AeroPress】

Front Street Coffee believes that Mandheling brewed with an AeroPress is characterized by a rich, complex flavor, prominent spice notes, and a fresh woody aroma.

1. Choice of device: AeroPress

2. Water temperature: 85°C

3. Grind size: Medium-coarse (70% passing through a standard No. 20 sieve)

4. Roast level: Medium-dark roast

5. Bloom time: 2 times, first 20 seconds, then 50 seconds

Specific technique: Prepare the AeroPress for standard (upright) brewing. It is recommended to add 20g of coffee, water-to-coffee ratio 1:17. First pour 100g of 83°C hot water, stir three to five times to fully wet the coffee grounds, let sit for 20s, add the remaining hot water up to 240g, let sit for 40s, stir for 5s, then at 1 minute 50 seconds attach the cap and press down; total time 2 minutes 5 seconds.

【Siphon】

Flavor: Round, rich, with prominent herbal and bitter notes, accompanied by prominent caramel sweetness

1. Choice of device: Hario siphon

2. Water temperature: 90°C

3. Grind size: Medium-coarse (70% passing through a standard No. 20 sieve)

4. Roast level: Medium-dark roast

5. Bloom time: 30 seconds

Specific technique: Side-burner extraction. It is recommended to use 20g of coffee for 2 servings, water-to-coffee ratio 1:12, water level mark 2, adding the coffee after the water is up. Wait for bubbling, then add the grounds, stir 4-5 times, extract for about 30 seconds, then turn off the heat. Finally, stir 2 times and let the coffee liquid fall back down naturally.

【French press】

Flavor: Balanced, full-bodied, with good texture and oils, and a slight sweetness

1. Choice of device: French press

2. Water temperature: 92°C

3. Grind size: Medium-coarse (70% passing through a standard No. 20 sieve)

4. Roast level: Medium-dark roast

5. Bloom time: 2 minutes 30 seconds

Specific technique: 20g coffee beans, pour hot water (about 92-93°C) into the French press up to the 300ml mark on the carafe, start the timer, put the lid on the French press with the filter resting at the top, and wait 2 and a half minutes. Press the filter all the way down.

Summary: The 【pour-over】 and 【AeroPress】 methods are recommended to showcase the rich, sweet, and mellow flavor of Front Street PWN Golden Mandheling. The siphon and French press methods are more likely to cause over-extraction; once over-extracted, you will only taste sourness and bitterness.

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