A roaster’s guide to Sumatran coffee

Peter Lancashire
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March 15, 2022
sumatran coffee

Indonesia has a rich history of growing coffee, with the first crops integrated into the country over 300 years ago.

It is the world’s fourth-largest coffee producer and exporter, and the island of Sumatra makes up over 60% of the crop growing areas in the country.

In 2021, Indonesia produced an estimated 750,000 metric tons of coffee. Sumatra accounted for close to 75% of Indonesia’s total coffee production.

However, Sumatran coffee can be divisive within the specialty sector as it has a unique processing method that results in an intense flavour profile. While it may not be to everyone’s tastes, Sumatran coffee is popular among those who prefer a dark, more intense roast profile.

Read on to get a better understanding of Sumatran coffee and how it should be roasted.

island of sumatra

What is Sumatra?

Indonesia was one of the first places to cultivate coffee beans on a large scale outside of Ethiopia and Arabia.

After Borneo, Sumatra is the second-largest island in west Indonesia. It is split by the equator, providing an ideal tropical climate for coffee growing and production.

Dutch colonists first introduced coffee plants to the island in the mid-1870s and began growing near Lake Toba. The lake surrounds a super volcano, making the soil incredibly fertile and rich in nutrients.

Almost all coffee grown in Indonesia now comes from smallholder estates, with three main coffee varieties coming from the island of Sumatra.

Mandheling

Mandheling is a trade name used for arabica coffee grown in northern Sumatra. The name derives from the Mandailing people, who produce coffee in the Tapanuli region of the island.

Mandheling coffee is typically known for its sweet chocolate and licorice tones, and earthy aroma. It is often medium or dark roasted to bring out the beans’ unique characteristics.

Gayo

Different from other types of coffee in Indonesia, Gayo coffee has a very distinctive taste and aroma, which makes it sought after by roasters and consumers alike.

It is known as one of the best quality coffees from Indonesia, and has a variety of flavours. This is because the location of the soil, water content, and soil conditions in the Gayo highlands tend to vary.

Lintong

Lintong coffee is grown to the south-west of Lake Toba, and this area produces up to 18,000 tons of arabica a year.

While this coffee is lesser known than the Mandheling and Gayo varieties, its sweet flavour and low acidity makes it quite popular among specialty coffee drinkers.

brewing coffee with a v60

What does Sumatran coffee taste like?

Generally, Sumatran coffee has distinct flavour profiles, depending on which part of the island the beans are grown. It is commonly full-bodied, with little acidity and an earthy, herbaceous aroma.

Many of the signature flavours found in Sumatran coffee can be attributed to how the beans are processed.

Coffee producers in Indonesia traditionally use the “wet hulling” or “Giling Basah” processing method. This method usually takes between two and three months to bring beans to a state where they are ready for roasting.

Wet hulling should not be confused with wet processing, as they are two very different methods. “Wet processing” is the traditional washed process used in most coffee-producing countries.

Wet hulling uses pulp machines to remove the skins of the coffee cherries. The beans, which are still covered with mucilage, are left to ferment overnight. They are then washed and only partially dried so the beans retain around 50% of their moisture content.

The semi-wet beans are then sent to warehouses to dry further before being shipped to importers and roasters.

Lei Cruz, who is part of the marketing team at Home Grounds, states the wet-hulling method has been adopted by Indonesian producers because of the area’s damp climate. “Farmers in the region typically have less than four hours of drying time a day,” she says in an online article.

roasting sumatran coffee

How to roast Sumatran coffee

Many tend to roast Sumatran coffee towards the medium to dark side of the spectrum, as this tends to bring out more sweetness and body. However, it’s important for roasters to judge each batch individually as not all Sumatran beans will behave the same.

For example, an article published on Sweet Maria’s Coffee Library blog suggests there is a tendency to over-roast Indonesian coffee beans. “The reason is that they don’t show as much roast colour, and have a mottled appearance up until the second crack,” the article states.

This often makes roasters think the beans must be roasted dark. While the resulting cup of coffee can be quite pleasant with a dark roast, Indonesian coffees should be roasted to the verge of the second crack, and no further.

In light of this, samples should be taken several times between the first and second crack. This will give roasters a better idea of how long the coffee needs to develop.

However, while extending the roast time can help roasters develop a well-balanced cup, lighter roasts may be better suited to natural-processed Sumatran coffees.

For example, Canada-based Eleven Speed Coffee Roasters state: “Coffee from Sumatra is typically associated with dark, smoky, earthy flavours due to the wet-hulling process. Recently, new processing techniques have started to gain popularity and farms can earn more from higher quality coffees.”

The flavours traditionally associated with Sumatran coffee are an acquired taste. However, educating producers in the region could help elevate Indonesian beans and remove the stigma attached to them.

Furthermore, roasters can introduce consumers to more Indonesian coffees so they are able form their own opinions on the unique taste. Ultimately, keeping the beans fresh is essential to ensuring consumers enjoy the full range of flavours Sumatran coffee provides.

sustainable coffee bags

At MTPak Coffee, we can provide roasters with sustainable coffee packaging materials, such as kraft paper, rice paper, PLA, and LDPE coffee bags. Our recyclable, biodegradable, and compostable options in addition to recyclable degassing valves and resealable zippers will ensure your packaging is as sustainable as possible.

Additionally, our sustainable water-based inks can be used to print information on your coffee bags, helping to educate consumers about the unique flavours behind Indonesian coffees.

For more information on our sustainable coffee bags, contact the team.

A roaster’s guide to Sumatran coffee

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