COFFEE WASHING PROCESS

Wet Hulled

Wet-hulling, or giling basah, is a traditional coffee processing method used in Indonesia. The word ‘hulling’ refers to removing the parchment from the beans.

Firstly, ripped cherries are picked and depulped through a hand-cranked pulper that only removes the skins while retaining most of the fruit and mucilage on the beans.

The beans will then be placed in a water tank or plastic rice bags overnight to allow the wet-fermentation process to take place. This step breaks down the pectin in the mucilage, making it easier for the mucilage to be washed off the next day.

After removing the mucilage, what remains is also known as a wet parchment coffee. From here, the beans will be sun dried in its parchment for around 24-72 hours, where the moisture content will be about 20-24% — leaving the bean at the required hardness for hulling. Since the parchments are semi-dry, the beans will be soft and inflated with water. 

The semi-dried beans will be placed through a specially designed huller that hulls semi-dried parchment. Finally, the process will be finished when the hulled beans are re-dried until it has 10-12% moisture content, before it is prepared for shipping.

Wet-hulled coffee beans are identified by their dark green and bluish appearance. They usually have a heavy body, little acidity or sweetness. Notable cupping notes include herbs and distinct spicy notes.


Wet Hulled
Pick Ripe Cherries
In the picking stage, the level of ripeness and elevation of fresh fruits (cherries) are critical. Red and purple-red cherries produce the best flavours, while under-ripe (green) and over-ripe cherries produce astringent tastes which deteriorate the overall cup-quality. Often, red-cherries grown at higher altitudes are highly demanded as it produces better flavours due to better maturity and higher sugar content.
Submerge in Water
Submerging is a process of removing impurities from the harvest. Through the fluidity and gravity of water, the immature fruits, floaters, withered beans, sticks and leaves are removed. When the fresh cherries are submerged in water, the pulp which carries microorganisms will hasten the fermentation process.
Depulp
After Cherries are harvested, they have to be depulped within 24 hours or else the cherries may produce an overly fruity or rotten flavour that can ruin the coffee’s cup-quality. Depulping is the process of separating the coffee seeds from the outer layer of flesh from the fruit and it usually happens at the farm or a centralized depulping station.
Ferment
During fermentation, microorganisms in mucilage will react with sugar to degrade, leading to fermentation. This is an essential stage of coffee processing as this is when microorganisms interact with enzymes and amazing flavours are developed. The coffee fragrance changes from fresh fruits to berry-like, transforming into tropical fruits and rich red wine - the ideal state of natural fermentation.
Remove Mucilage
After the cherries are depulped, what remains are coffee beans covered in a thin and sweet (sugary) layer known as the mucilage. There are two ways of removing the mucilage: 1. Fermentation. 2. Mechanical separation. Through fermentation, the beans are poured into a clean tank where its natural bacteria and enzymes react to break down the mucilage layer. On the other hand, removing mucilage through machines is easier, however it disallows the producers in having the flexibility to influence the coffee flavour.