The pristine region of North Sumatra is the birthplace of a unique coffee processing method employed nowhere else in the coffee bean-producing world. A creative combination of traditional techniques and local factors have been woven to craft the wet-hulled process.

There are many contributors to the cup including bean variety, terroir, altitude and micro-climate. All these, combined with the innovative wet-hulled processing, bring us one of the most distinctive profiles in the world. Juicy and syrupy, Sumatran coffees are renowned for having a bigger and bolder body in the cup than that of other regions, with uniquely earthy, herbal and spicy notes.

During a Q Calibration class, the blind cupping of a Sumatran Blue Batak confused everyone’s taste buds; it was simply so different! When the scores of each Q Grader candidate were revealed, there was an enormous variance in how each person interpreted it. It is truly a coffee that starts conversations!

As specialty producers, our Tiga Raja mill operators have extensive knowledge of the preparation and processing of this unique wet-hulled coffee. Through our collaborations, we have a fortunate ‘up close and personal’ vantage point and have gained a strong understanding as to the origins of this profile. It begins with a systemised logistics system, an economical yet effective fermentation process, and a hulling and drying method that is truly extraordinary.

People, Culture and Environment

Wet-hulling, or giling basah, is an inspired process indigenous to North Sumatra. This region of Indonesia has its peak harvest from October to January. These are the wettest months of the year, making it extremely difficult to dry the coffee over an extended period. As coffee is growing so quickly during these months of prime conditions, it must also be picked and processed regularly.

The popularity of wet-hulling can be attributed to the producers’ need for prompt payments. Holding a supply of coffee cherries for too long is not ideal, and so to reduce risk, local farmers developed a technique to remove the coffee husk while the beans are still at 35% moisture thus speeding up the drying process. Comparatively, in other coffee-growing regions, the removal of husks is delayed until the beans are between 12-15%.

Typically, farmers in North Sumatra yield between 400-500 kgs of green beans per hectare during the main harvest season. Sometimes a smaller harvest (called fly crop) follows around March or April. On average it takes between 7-10 days to have the coffee move from ‘cherry’ to ‘green bean ready’, depending on the weather.

The typical production cycle of North Sumatran Coffee goes a little like this:

Day 1 (Harvest Day)

Coffee farmers pick their cherries once a week, usually the day before market day. They do the cherry picking in the morning, followed by pulping (usually with a hand-cranked depulper) in the late afternoon. The coffee bean, with mucilage intact, will ferment overnight in jute bags.

Day 2 (Market Day)

The coffee is washed early in the morning. This process is made easier after the overnight fermentation. This washing removes all layers except the parchment. In the farmers' backyard, the beans are then laid out to dry on the patio for the day. Moisture levels at this stage are still around 40-50%.

Toward the end of the afternoon, the farmers will take a full grocery bag (or for larger farmers a full jute bag) of parchment to the market where it is typically sold to a processing collector. The purchase price this agent gets at the mill or from a processor will reflect an agreed quality. It’s a busy day of business for the farmers who often have other crops (such as citrus) to sell at the market.

By the end of Day 2, the farmers have money in their pockets to purchase weekly groceries. In other bean processing environments, it can take months to see a financial return for harvest so wet-hulling is an efficient and attractive method.

Day 3 (Drying)

After receiving the coffee, the coffee processor or mill will dry it for one more day to bring the moisture level down to around 35%. This measurement is mostly done intuitively by experienced hands.

Day 4 (Wet-Hulling Day)

The timing of this step is crucial. If the parchment is dried for too long it will compromise quality and the coffee will become discoloured. If dried hastily, the beans will break and chip during the process. The hulling equipment must be adjusted specifically to remove wet parchment, as the bloated bean is still pressing against the parchment shell.

Day 5-7 (More Drying)

Once hulled, the drying process continues in a greenhouse, with regular turning. At the point it reaches 14% moisture the beans have reached ‘Asalan Grade.’

Day 8 (Sorting)

To achieve the label of ‘Suton Grade’ a gravity separator removes all the broken beans and sorts the harvest by density. It is usual to expect to lose around 7% of the total volume during this process. It’s at this point a more accurate measure of moisture content can be calculated and achieved to the desired 13%.

Day 9 (The Final Stage)

The coffee is sorted manually, twice. The first time for primary defects and then again for secondary. It’s desirable not to lose more than another 7% during this quality control stage however, during a bad season, we can lose as much as 20%. To ensure quality, this stringent process is an absolute necessity.

For Five Senses, this means our Tiga Raja coffees are now ready to prepare for export. We excitedly await the delivery of this truly unique experience because the joy of this coffee and its history is in the sharing.

Introducing Tiga Raja, Wet-Hulled


The wet-hulled process is now used throughout the Indonesian archipelago and even experimentally in some other countries. The Aceh region of Northern Sumatra is where this unique processing style originated.

This Indonesian produce comes with a distinctive signature and has a special place in the world of coffee. We roasters identify it through the slightly bluish colour of the green bean. Your barista might notice some split or slightly chipped beans which are the identifying marks of the wet-hulling process. As a coffee lover, you will notice it in bold, earthy flavour notes that may be new to your palette.

These marks and flavours help tell the story of the special people, culture and environment who’ve contributed to its creation. The narrative includes the hard work of the farmers in fields and on patios. It describes busy village markets and family groceries being bought and sold. The mill and its workers are represented in the attentive detail to the flavour profile. They speak of silver raindrops, and green mountains covered in heavy grey clouds.

They tell the story of our Tiga Raja coffee.

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