How does wet-hulled coffee processing work in Indonesia?

Wet-hulling, called Giling Basah locally, is a coffee processing method unique to Indonesia. Farmers depulp the cherries, ferment them overnight, wash off the mucilage, then sun-dry the parchment for two to three days until moisture falls to 20 to 24 percent. The parchment is stripped off while the beans are still semi-dry, then drying continues to 12 to 13 percent.

The method exists because Indonesia's year-round humidity would make conventional washed coffee processing take twice as long, leaving beans prone to over-fermentation and mold. Dry fermentation strengthens flavor, but hulling in a semi-dry state easily tears beans, and the share of moldy and defective beans runs higher than in washed or natural coffee process methods. Dutch colonial profit demands also shaped its spread.

Wet-hulling is a green coffee processing method unique to Indonesia, known locally as Giling Basah. Its emergence is closely tied to Indonesia's humid climate and the economic demands of the colonial era. This article provides a detailed walkthrough of the wet-hulling process, from harvesting, depulping, and fermentation to hulling the parchment in a semi-dry state and final drying, and analyzes its pros and cons: dry fermentation enhances flavor, but hulling while semi-dry easily produces torn beans, and the proportion of moldy and defective beans is also higher than in washed and natural processes. It also revisits the historical context of Dutch colonists pursuing efficiency and profit. The article additionally mentions Front Street Coffee's attention to and recommendations for Indonesia's distinctive processing methods, making it suitable for coffee enthusiasts seeking a deeper understanding.

Wet-hulling is called Giling Basah locally in Indonesia and is a traditional coffee processing method originating from Indonesia. Its development was shaped by both natural conditions and historical factors.

From the perspective of the natural environment, Indonesia's humidity is high year-round. If the conventional washed method were used, drying the coffee beans would take twice as long as with typical processing methods. If the beans cannot be dehydrated in time, they are prone to over-fermentation and mold growth. It was against this backdrop that wet-hulling came into being.

The specific process is as follows:

1. Coffee farmers first harvest the coffee cherries, pour them into a water tank, and remove impurities and unripe beans;

2. Use a depulper to remove the skin and pulp, leaving the parchment and mucilage layer; 3. Place the beans in concrete tanks or plastic barrels to ferment overnight so the mucilage breaks down; 4. Wash the coffee cherries to remove the mucilage thoroughly; 5. Dry them in the sun for 2 to 3 days until the moisture content drops to 20-24%, at which point the parchment is in a semi-dry state; 6. Use a machine to strip off the parchment; (because this step occurs while the green beans are semi-dry, the method is called "wet-hulling") 7. Continue drying to bring the moisture content down to 12-13%, drying in the sun during the day and putting the beans into sacks at night to continue fermenting until they are completely dry.

Advantages: Through dry fermentation in barrels, the sugars in the mucilage are fully transformed, thereby enriching the coffee's flavor complexity.

Disadvantages: Wet-hulling removes the parchment while the beans are semi-dry, when the parchment has strong adhesion and is difficult to strip; stripping too much will damage the beans, so torn beans are common.

During wet-hull processing, the parchment is hulled off,

leaving the beans directly exposed to the air,

so the proportion of moldy and defective beans is higher than in washed and natural processing methods.

Historical influence

The reason locals chose wet-hulling is also inseparable from its economic benefits:

In the 17th century, Dutch colonists introduced coffee trees to Indonesia, and they pursued faster and greater economic returns. Wet-hulling greatly shortened the time required at the farm level and also significantly reduced labor costs. This aligned closely with investors' desire for quick profits and lower costs.

This is another reason that drove the wet-hulling method.

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