Wet Hulling Explained

Typical Indonesian coffee processing explained

Wet hulling or 'giling basah'

Wet Hulling Process

Wet hulling or 'giling basah' is unique for Indonesia

Below describes the supply chain and processing for the Indonesian Wet Hulled coffee. This method is used all over the country, but pictures and description below are from the situation in North Sumatra & Aceh provinces. Other locations are similar.

Cherry Picking

To start with the red cherries are hand picked. This is done by both men and women on farm level. Each farmer (woman/man) having approximately 1 ha of land.

Indonesia Sumatra Coffee harvest farmers
local coffee cherry pulping machine


At the end of the day the cherries are collected and pulped using rustic pulping machines.


The freshly pulped coffee is then stored in small tanks or bags overnight for fermentation. This is for a period of approximately 12 hours and is necessary to be able to wash off the remaining mucilage on the beans.

Coffee fermentation Indonesia Sumatra
Coffee drying farm Indonesia

Drying to 35%-40%

In the morning the coffee is washed and then dried to 35-40% moisture. This is often done at the farmers house or, if they do not have enough space, at a mill. Coffee is now locally called Labu.

It is usually at this stage that the coffee is sold to a collector and on to a mill with hulling facilities. Farmers will often have several collectors to choose from. Collectors can be working independently, working for an exporter or for a cooperative and they usually cover a few villages.


Once the coffee is dried to 35%-40% it is hulled. This is the famous wet-hulling process, unique for Indonesia. Coffee is wet-hulled because it allows for faster drying of the coffee.

Coffee wet hulling Indonesia Matahari-gt
coffee drying Sumatra

Drying to 12%

Sun-drying follows, on the mill’s patios until reaching a 12% moisture content. This takes about 3 days. The coffee is now called Asalan.


Following the drying process, the coffee is graded using an array of machines: a gravity sorter (Sutton), a de-stoner and sometimes a colour sorter.

Coffee grading local Indonesia Matahari gt
Hand sorting coffee Mandheling Indonesia Matahari gt

Hand Sorting

Then the hand sorters (usually local ladies)  go over all the beans up to three times.

Bagging & Loading

The coffee is then put into bags and loaded into a container for export. In Indonesia jute bags of 60 kg are used. GrainPro (or similar) are not a standard, but can be included for an extra fee of between $70 – $100 per ton.

Packed green coffee in jute bags Indonesia Matahari gt
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