What is Wet Hulled?

There are many things that can influence a coffee’s flavour on its journey from field to roastery.

Terroir, species, varietal, weather and processing can all play a part in creating cup profile. This is no more apparent than in Indonesia, where a coffee processing method reflects both the culture and climate of the country.

During a recent trip to Sumatra, we learnt more about the process known locally as Giling Basah.

Giling Basah

In the Indonesian Bahasa language, Giling Basah translates to ‘hulled’ and ‘wet’, meaning ‘wet-hulled’. It refers to a processing method specific to Indonesian islands like Sumatra and Sulawesi, and contributes to these regions’ full-bodied, earthy and forest-like cup profiles.

The wet-hulled process shares similarities to the washed process; however, it has some key distinctions that make it unique.

The Wet-Hulled Process

In the washed process, coffee cherries are typically picked, floated and pulped to remove the skin. They are then fermented in tanks overnight to remove the sticky mucilage before being washed and dried in their parchment, either mechanically or in the sun.  

Once the green beans and parchment have reached the desired moisture level (10-12%), they are dry milled, sorted, graded and stored, ready for shipment.  

You can read more about this in Jamie’s article here.  

With wet-hulled processing, the first few steps are the same as the washed process. Farmers pick coffee cherries, known locally as Golongdon, and either deliver them to local collectors or process them on their farms.  

Coffee is washed and floated to remove underripe cherries, pulped to remove the skin and fermented overnight. 

The following morning, coffee is rewashed and dried on patios in the sun. It is here where the wet-hulled method diverges from washed processing.  

Instead of drying the parchment coffee to 10-12% moisture, coffee is dried to 40-50%, which takes around two to three days. At this stage the coffee, still plump and moist, is known as “Gabah”.  

The wet Gabah is collected, then ‘wet-hulled’ to remove the parchment. Hulling occurs in machines specifically designed to hull while wet to limit the damage to the pliable coffee.  

The resulting coffee is referred to as “Labu” – wet-hulled coffee with a moisture content of 40-50%.

The Labu is returned to the patios and dried for a further two days. As the Labu reaches around 15% moisture, it is gathered and often sent to dry mills or warehouses for final drying and processing. At this stage, the coffee is referred to as “Asalan”.  

At the final stage, Asalan coffee is dried to 12% before cleaning, separating, sorting and preparing the coffee for export. 

Why Do Farmers Wet Hull?

On paper, the wet-hulled process is more complex than washed-processed coffee. And with more processing stages comes more room for error. So why do farmers and collectors wet hull, removing the protective parchment while the coffee is still wet? 

It’s estimated that 99% of the coffee produced In Indonesia is by smallholders. Many producers will grow coffee alongside other crops, relying on agriculture for their primary income. Producing and selling coffee quickly is an asset during harvest in gaining access to money quickly, so speeding up the process can benefit producers and collectors alike.  

The Indonesian climate also makes coffee processing very hard. Unlike areas such as South and Central America or Africa with kinder climates, Indonesia’s high humidity and rainfall during harvest season, especially in regions like Sumatra, makes it hard to dry coffee. The tricky Indonesian climate limits other methods like washed or natural, so hulling the parchment while wet reduces the coffee’s mass and helps reduce drying time.  

Quality & Flavour

For some, the cup profile of wet-hulled coffee can be a challenge. Descriptors like ‘herbal’, ‘earthy’ or ‘mossy’ may not resonate with the speciality aficionados out there. But within Giling Basah coffee, there is a world of flavour to explore.   

Traditionally, wet-hulled coffee is known for its high body and low acidity. But in recent years, as more attentive processing and sorting have emerged in reaction to the specialty coffee industry, wet-hulled processing is unveiling some exceptional cup profiles. 

The Hutan coffee produced by Ketiara KOPEPI, for example, has a vibrant and sophisticated, pineapple-like acidity underpinned by a chocolate-tobacco sweetness. Ketiara’s Mandheling is herbal but has a wonderfully comforting cup profile with cinnamon, nutmeg and orange tasting notes. These are cup profiles that you won’t find anywhere else in the world. And with the coffee scoring 84+ points, they are definitely ticking the specialty boxes.  

The wet-hulled process plays an essential role in forming Sumatran coffee. And it’s amazing to think that the Giling Basah method was itself developed out of the need to work in harmony with the region’s climate.  

You’d be hard-pressed to find another cup profile that is so intrinsically linked to the land in which it was grown.  

Discover the flavours of wet-hulled processing by exploring our range of Sumatran coffees below.