Aceh Gold and the Science of Specialty Coffee - Exploring Mandheling Grades from Sumatra Island

Exploring Premium Indonesian Coffee: A Comprehensive Guide

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To gain deeper insights into premium coffee, FrontStreet Coffee purchased Mr. Han Huaizong's book "Premium Coffee Studies." The shop gifted us a sample bag of coffee beans labeled "Sumatra Aceh Gold."

After some research, we learned that Aceh Gold is actually Aceh Gold—high-quality coffee from the Aceh region of Sumatra Island. Traditional Sumatra coffee gives a first impression of intense, bold, herbal "heavy flavors." With such curiosity, FrontStreet Coffee tried this Aceh Gold and was surprisingly impressed. It not only lacked the characteristic herbal and medicinal notes of Mandheling but also avoided the heavy smoky flavor. Instead, it offered a very clean profile with rich creamy chocolate aromas and a hint of subtle acidity, making FrontStreet Coffee feel like we were tasting a refined Latin American coffee.

At this point,我相信 our friends are eager to understand the mysterious Aceh region. Let FrontStreet Coffee guide you into this world-famous island nation and deeply explore what premium coffees this region offers.

Indonesian Mandheling coffee features very rich and mellow caramel and herbal flavors, with a thick body in terms of mouthfeel—substantial and full, with a long-lasting sweet aftertaste. FrontStreet Coffee considers it a premium coffee well worth tasting. Indonesia is a major coffee-producing country in Asia, with Mandheling being its most famous coffee. The country has three major coffee-producing regions—what are the differences between the Indonesian coffees they produce? Follow FrontStreet Coffee to find out!

Indonesian Coffee Geography

Indonesia consists of over 17,000 islands scattered along the equatorial volcanic belt. Indonesia straddles both sides of the equator, with a humid tropical rainforest climate abundant in rainfall and fertile volcanic soil providing rich nutrients. The best planting areas throughout the archipelago are Java, Sumatra, and Sulawesi islands.

Coffee Growing Regions:

Java Island (Jawa)

Java holds an extremely important position in coffee history. Unlike most other Indonesian coffees grown on small farms for initial processing, Java coffee grows on large farms or plantations, mostly government-operated, using modern methods for washed processing. The variety belongs to S795, locally called Jember, and is artificially cultivated.

Java produces refined aromatic coffee with relatively low acidity, delicate mouthfeel, and good balance. Java coffee's aroma and acidity surpass those from Sumatra and Sulawesi islands. Java's best plantations include Blawan, Jambit, Kayumas, and Pankur. Java Mocha coffee is a blend of Java coffee and Yemen Mocha coffee.

Sulawesi Island

Sulawesi Island was formerly called Celebes. Sulawesi is one of the oldest islands in the archipelago, with exposed rocks dating back over millions of years. Yellow-red podzolic soils are found in coffee production areas. These soils often contain several layers of iron-rich clay beneath the surface. The most famous region is Toraja, located in the highlands of South Sulawesi.

Kalosi, south of Toraja, is the main metropolitan area of this region. There are two lesser-known areas: Mamasa to the west and Gowa south of Kalosi. Some particularly interesting beans are processed using the washed method, worth exploring—highly recommended to try if you have the chance. The semi-washed processing method is commonly used throughout Sulawesi Island, and the area also produces many Robusta beans. This area's name is most often used to represent Sulawesi coffee, known for its full viscosity, rich flavors, and deep yet lively acidity.

Most Arabica beans are grown at high elevations around Tana Toraja, while Kalosi in the south has become a brand name.

Kalosi: A market name for coffee from the southwestern part of Sulawesi Island, named after the small town of Kalosi in the island's central region, serving as the main trading hub for Toraja coffee beans.

Toraja: A growing area in the southeastern highlands of Sulawesi Island, also the name of the island's premium beans. Toraja is not a place name, city name, or variety name, but rather refers to the "Toraja" people who live in the central mountainous region of Sulawesi and are skilled at growing coffee. Toraja is also one of the world's rarest premium beans, with an annual production of about 1,000 metric tons, distributed across the rugged slopes at about 1,200 meters elevation in central and southwestern Sulawesi. Cultivation and harvesting are difficult, with an average annual yield of only 300 kg per hectare—far below the average of over 1,000 kg in Central and South America.

Toraja's three major plantations include: "PT Kapal Api" with 2,000 hectares of coffee gardens; "CSR" ranking second with 1,100 hectares; and Japan's "Key Coffee" "Toarco Jaya" as the third largest with 700 hectares. In other words, Toraja is more precious and rare than Mandheling or Golden Mandheling.

Toraja uses washed or semi-washed processing, offering brighter acidity than Sumatra's Mandheling or Golden Mandheling, with more distinct layering. It has rich caramel sweetness but less earthy, woody flavors and body thickness than Mandheling, with slight floral notes.

Sumatra Province

The best coffee from Sumatra comes from two places: in the northern part of Sumatra, the Central Aceh region near Lake Tawar, and further south in the mountainous area around Lake Toba. Due to many small tenant farmers and their unique semi-washed processing methods combined with iron-deficient soil, coffee beans from this region display a distinctive blue color in their fresh green bean stage.

Mandheling: Refers to semi-dried or sun-dried beans from the Lintong mountainous area at 900-1,200 meters elevation on the southwestern shore of Lake Toba in north-central Sumatra. The Batak people form the backbone of coffee farmers in this region, once praised as the world's fullest coffee beans. Mandheling is a trademark used for Arabica coffee from North Sumatra, produced by the Mandailing people from the Tapanuli region of northwestern Sumatra, featuring unique herbal and woody incense flavors.

Lintong Region: Lintong Mandheling, elevation 1,200 to 1,500 meters, comes from the most famous coffee in the Lake Toba region of North Sumatra Island. A correct understanding of Golden Mandheling coffee—it's not simply that golden-colored Mandheling equals Golden Mandheling.

Golden Mandheling is produced in the Lintong region of northern Sumatra, Indonesia. Harvesting is limited to fully manual single-berry picking of fully ripe fruits to ensure initial bean selection quality. Coffee cherries undergo SEMI-WASHED processing, natural sun drying, and after hulling, go through another drying refinement process, two green bean cleaning operations, and four Hand-Pick manual selection processes. Therefore, it can be said to be a strictly selected top-grade Mandheling coffee. Golden Mandheling marked with "PWN" is the abbreviation of Indonesia's Pawani Company, whose produced Golden Mandheling coffee has been registered in Indonesia.

Lake Toba, located in central North Sumatra Province. Dutch colonists moved "Java Mandheling" north to the Lake Toba region in 1888. Lintong in North Sumatra and the Lake Toba area can be called Mandheling—Lintong is truly the Mandheling producing region. Mandheling originates from the mountainous area around Lake Toba. This lake's geographical location is north of Medan, the capital of Sumatra Island, belonging to a high-altitude freshwater lake. Average height is about 900 meters above sea level. The commonly mentioned Mandheling refers to Typica or its variant coffee beans grown in the mountainous area around Lake Toba. This lake is diamond-shaped, 100 kilometers long and 30 kilometers wide, covering 1,130 square kilometers. It's a high-altitude lake with an average elevation of about 900 meters; simultaneously, it's also the world's largest volcanic lake.

Lake Tawar, located in central Aceh Special Autonomous Region. Situated at the northern tip of Sumatra Island, most coffee produced in North Sumatra is Gayo, mainly of the Ateng variety. Lake Tawar at the northern tip can be called Aceh coffee or Lake Tawar coffee. Its area is less than one-tenth of Lake Toba. However, in recent years, coffee quality and production have surpassed Lake Toba.

Gayo Mountains Aceh

Aceh, elevation 1,110 to 1,300 meters, at the northernmost corner of Sumatra Island. In Aceh Province on the northern side of Sumatra Island, Gayo coffee is grown on the slopes surrounding the town of Takegon and Lake Tawar. The elevation in production areas averages between 1,110 and 1,300 meters. Coffee is grown by small tenant farmers under shade trees. Wet-processed coffee is cleaner but usually doesn't match Sumatra coffee's flavor characteristics. Traditionally processed coffee resembles that from Sumatra's Mandheling region, with advantages showing unique flavors and deep yet lively viscosity.

Aceh has suffered long-term political instability, making it not a region most people would visit. Gayo people are determined personalities, hardworking and resilient, with nearly 20% of coffee processors being women.

FLORES

Flores is a small island about 320 kilometers (200 miles) east of Bali Island, one of the Indonesian archipelago islands, elevation 1,200 to 1,700 meters. As a region that entered the coffee industry relatively late, it has developed a good reputation in coffee cultivation.

In the past, much of Flores' coffee production was for domestic consumption or mixed with other coffees for export, rarely sold directly under the name "Flores coffee." The island has active and dormant volcanoes, with Bajawa volcano's mixture having significant positive impacts in the main growing areas. In coffee processing, semi-washed processing is the most common method in this region, with some still using fully washed processing. Harvest period is May to September.

Timor Island

Divided into East Timor and West Timor. Originating in the early 20th century, East Timor has not used chemical agents and fertilizers for the past 25 years, making it possibly the world's largest organic coffee producer. However, due to East Timor's political instability, exports are difficult. Currently, most available beans are from West Timor.

Bali Island

Although part of Indonesian coffee, Bali's coffee farmers feel that Indonesian coffee quality is inconsistent and doesn't match Bali's premium coffee quality, so they established themselves as "Bali Coffee" to distinguish it from Indonesian coffee. Bali Island not only has Arabica coffee beans but also produces abundant Robusta coffee. According to sources, Bali Golden Coffee is created by grafting the roots of Arabica coffee trees with the branches and leaves of Robusta coffee, commonly known as the [Catimor] variety.

Coffee came to Bali relatively late, initially growing in the Kintamani highlands at 1,000 to 1,500 meters elevation. Coffee production was severely affected when Mount Agung erupted in 1963, causing over 20,000 deaths and widespread destruction in eastern Bali. By the late 1970s and early 1980s, the government distributed Arabica seedlings to promote coffee production, though some believe this had limited effects as about 80% of the island's current production is Robusta beans. Although tourism provides the largest income, agriculture employs the most people on the island, with Japan being the largest buyer in the past. Harvest period is May to October.

Civet Coffee (Luwak): Civet coffee from Bali is famous not for its origin but for its unique new processing method. A mammal called the civet eats ripe coffee cherries, digesting only the fruit flesh, while the extremely hard coffee beans are excreted. After manual selection, cleaning, sun drying, deodorizing, screening, processing, roasting, and several other steps, it becomes "cat poop coffee." Due to its very limited production and its rarity and special taste, this coffee has become one of the rarest coffees in the world and one of the most expensive.

Now some companies simply create a product also called "Kopi Luwak" by artificially raising and feeding coffee cherries to civets. Wild civets are captured and kept in iron cages for three years, constantly being fed and excreting coffee beans, many suffering from malnutrition, psychological trauma, and other issues (zoochosis), unable to adapt to nature and dying.

Varieties

Indonesia has over 20 varieties of Arabica coffee circulating in the commercial market. Common ones include Caturra, Catimor, Timor, Typica, Robusta, Liberica, Ekselsa, and Sidikalong. The most famous is Typica, the original cultivated variety introduced by the Dutch. When Indonesian coffee suffered from leaf rust attacks, many Typica varieties disappeared in the late 1880s. However, in Sumatra, Sulawesi, and Flores, especially in high-altitude and remote areas, the Typica varieties from Bergandal and Sidikalang can still be found.

Another variety is Long Berry Mandheling, also called TimTim—a bean from Indonesia. Due to its long shape, many call it "horse face bean," while others call it long strip Mandheling. Actually, Tim Tim is not a pure variety but a natural hybrid between Arabica and Robusta coffee trees. This variety was discovered on Timor Island in the 1940s and cultivated due to its natural disease resistance. In the Americas, this variety is called Hybrido de Timor, abbreviated as Tim Tim. In Indonesia, this variety is also called Bor Bor.

After being screened for particle size, some producers store the coffee for one to three years before sale. This process gives the coffee a very mild and warm character with woody and cinnamon flavors. Fresh beans gradually change color from deep yellow to brown.

Processing Methods

Three main processing methods: natural dry processing, semi-washed, and fully washed. Due to the humid climate with frequent rain, [Wet Hulling] is commonly used to pursue more efficient drying:

Most coffee farmers also only harvest fully red coffee cherries. After collecting coffee cherries in the morning, they remove the fruit skin and pulp in the afternoon. Sumatra's natural environment is superior, with most water used being mountain spring water.

1. Remove coffee fruit skin, place parchment beans in water-filled barrels or tanks, remove defective parchment beans floating on the liquid surface.
2. Clean the dense parchment beans that sink to the bottom, place them in barrels or plastic bags for slight dry fermentation—allowing the pectin sugars on the seed coat surface to ferment and enhance flavor. Basically, the longer the fermentation time, the heavier the acidity. Fermentation time varies by person, generally only a few hours, but some plantations skip the dry fermentation stage, directly sun-drying parchment beans to reduce acidity and increase viscous mouthfeel, allowing full pectin sugar fermentation to enhance flavor. Usually, fermentation time is between 12-36 hours, depending on specific conditions.
3. Sun-dry parchment beans for one to two days until moisture content reaches 30%-50%, beans still semi-hard and semi-soft, then use a hulling machine to remove the parchment shell and continue drying. About two days until moisture content reaches 12%-13%, then collect coffee beans into woven bags, usually 40kg and 80kg per bag, and send to coffee processing plants for hulling. Completion takes about four days total.

Risks of Wet Hulling: Beans are prone to cracking open like sheep hooves, with increased chances of mold, fungi, and yeast contamination.

Green Bean Grading

Defective beans are an important factor that destroys final coffee flavor. Therefore, the final step in green bean processing must remove defective beans. Grading is based on the proportion of defective beans, supplemented by screen size. With the rise of premium coffee trends, coffee-producing countries increasingly focus on coffee quality. Controlling defective beans is the most important approach, so using defective bean proportion as a grading method or auxiliary basis is becoming increasingly common. Indonesian coffee beans adopt this defective bean proportion grading method. Indonesian beans are mainly divided into 6 grades: G1-G6.

Grading by defect rate (based on 300g), Grade standards:

• G1 Grade1: Total defects less than 11
• G2 Grade2: Total defects greater than 12 less than 25
• G3 Grade3: Total defects greater than 26 less than 44
• G4a Grade4a: Total defects greater than 45 less than 60
• G4b Grade4b: Total defects greater than 61 less than 80
• G5 Grade5: Total defects greater than 81 less than 150
• G6 Grade6: Total defects greater than 151 less than 225

Common abbreviations in Indonesian green bean exports:

Processing methods: WP=WetProcessed-Wet Hulling; DP=DryProcessed-Natural/Dry; AP=AfterPolished-Polishing (removes silver skin)

Aged Mandheling

Green beans achieve natural aging through extended storage time (usually 2-3 years). These changes include reduced acidity, color changes, and increased bean thickness. The storage environment must be cool and ventilated, conducted under strictly controlled conditions with regular uniform turning, humidity and ventilation adjustments to prevent insect infestation or mold.

Flavor: Through the precipitation of time, it loses some of Mandheling's wildness while gaining more thickness and delicacy in mouthfeel. After aging processing, coffee beans have weaker acidity but higher body and thickness, giving a mature and steady feeling, completely different from the lively and bright character of new beans. Acidity becomes very gentle, mouthfeel more rounded and easy to drink, much like aged Pu-erh tea. It has a pleasant pine aroma with herbal and cocoa flavors, plus persistent caramel-like sweet aftertaste.

Tiger Mandheling

• Region: Aceh
• Varieties: Caturra, Typica, Sidikalong
• Soil: Volcanic soil
• Elevation: 1500m
• Processing: Wet Hulling
• Flavor: Relatively balanced mouthfeel with high cleanliness, featuring distinct cream, dark chocolate, and nut flavors.

West Java Coffee

• Region: Mount Tigulaja, Indonesia
• Elevation: 1400-1600 meters
• Roast Level: Light
• Processing: Honey Process
• Flavor: Strong fruit aroma, tropical fruits, plum and jackfruit flavors, clean and sweet aftertaste.

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