Why Sumatra Coffee Tastes Earthy—And How Natural Processing Changes the Game

Sumatra coffee is famous for its bold, earthy, and herbal flavors, but why is that? The answer lies in its unique wet-hulled (or "Giling Basah") process—a method that speeds up drying in Sumatra’s humid climate but also leaves the beans more vulnerable to defects. This approach contributes to its signature deep body and low acidity, but often prevents Sumatra coffees from meeting specialty-grade standards due to inconsistency and imperfections.

However, a growing number of producers are experimenting with natural (dry) processing, a method that allows the coffee cherry to dry fully before removing the parchment. This change preserves the fruit’s sweetness, enhances clarity, and introduces vibrant, juicy flavors—offering a new take on Sumatra coffee that can rival the best specialty lots. 

What does coffee process mean?

The coffee seeds that we roast and grind are found inside of a fruit. There are a number of ways for farmers to harvest that seed from the fruit – this is called processing. The way a coffee is processed plays a huge part into why you may like (or dislike) a certain coffee. Different processes will do a better job of highlighting certain characteristics of a coffee over others. Sometimes the resources available at origin will dictate what process is traditionally used, such as Giling Basah in Indonesia or natural processing in areas where water may be hard to come by.

While you may have a preference, this doesn’t mean that one process is superior over another. There are a lot of ways a coffee can be processed–some are more traditional while others can be more experimental–however, the general steps are similar across the different methods. Two of the most prominent coffee processing methods are natural and washed.

Natural Process

Natural processed coffees are harvested from the tree and are sent out to dry with the outer fruit still on. This results in the coffee seed receiving flavors from the outer fruit layer and its sugars. To maintain consistency, the coffee fruit is harvested when it has reached a fully ripe state. Natural coffees are typically dried on raised beds or patios until the fruit layer around the seed has completely dried, which can take at least two weeks. During the drying process a level of fermentation will occur which also affects the flavor of the coffee–usually leading to fruity notes. Once it is dried, the fruit layer is removed using machinery.

Washed Process

The washed process, or sometimes referred as the “wet process”, is where the coffee seed is extracted from the fruit before drying. This process uses de-pulping machines to squeeze the seed from the fruit. Once the seed is removed, they usually get sent to fermentation tanks that use microbes and yeast to break down the remaining sticky fruit and sugar remnants called “mucilage”. After spending time fermenting, the seeds are then washed with water to remove the mucilage. Once they are washed they are dried in the sun on patios or raised beds.  

Natural coffees typically result in a fruitier and more full-bodied flavor due to spending more time in the fruit, or cherry. Washed coffees tend to have flavors that are more associated with the seed itself–lighter body; higher acidity, and nuttier. 

Sumatra coffees, however, are not typically processed using any of these methods – for a very important reason. 

Explaining the Wet-Hulled Process

There is a very big variable that needs to be considered when deciding what coffee processing method to use–climate. The main goal in coffee processing is to extract the seed from the fruit, and to dry the seed. Because of drying being a central part of any process, climate can make a huge difference. Sumatra, and all of Indonesia, has a very humid climate. This humidity results in the coffee fruit staying on the tree for many more months compared to coffees of other origins. This wet climate causes issues for producers such as revisiting the plant multiple times through the picking season and elongating the drying process during processing. As a result, producers in this region have developed the "Wet-Hulled" process. This addresses the humidity issue, while impacting cup profiles with very distinct qualities.

The wet-hulled process–also referred to as “Giling Basah”–starts off similar to washed processing. The coffee fruit is harvested from the tree and then taken to de-pulping machines to have the seed extracted. Once extracted, the seeds are sent off to fermentation tanks to break down the mucilage before being washed off. This is where the similarities to washed processing ends. Wet-hulled coffees are then sent to machines to be hulled–to also remove the thin parchment layer of the seed. In other processes, this parchment remains intact as a layer of protection from pests, dirt, weather, etc. Drying coffees without the outer parchment layer is a lot quicker which is why farms in Indonesia adopt this method. 

Wet-hulled coffees are sent through a machine for removing the parchment while their moisture content is still relatively high, which can be risky. This is because wet coffee seeds are brittle and prone to cracking. Most coffees are dried to around 11% moisture content before removing their parchment layer for this reason. Wet-hulled coffees however, contain around 50% moisture content during this stage which leads to inconsistency in quality.

Giling Basah is trying to solve the problem of climate, but it is not an inferior method rather a necessary method. In every processing method there will be compromises – the compromise here is removing the parchment for quicker drying time, opening up the seed to exposure of outside elements. 

Why Natural Processed Sumatra is a Big Deal

Using natural processing for Sumatran coffees is not impossible, but it is very difficult and thus a rarity. Farmers still have to deal with the humidity, but they have been finding ways to overcome it. This usually requires more work to physically rotate the cherries, along with some luck from the weather, to prevent moisture build up that could lead to mold or rot. Our newest seasonal coffee is a Sumatra that has been processed using the Natural method. It has a fuller body and very pleasant fruity flavor with notes of blackberry, prune, and pineapple.

Sumatran coffees are not typically processed in this manner. This has led us to experience characteristics from these natural Sumatras that we have been missing out on. We are really excited to start seeing more farms from these regions experiment with processing, leading to more unique cups like this.