Indonesian Coffee Bean Processing Methods | Beyond Mandheling: Exploring West Java Origins

Coffee Processing Methods

Coffee processing methods refer to the process of transforming coffee cherries into green coffee beans (seeds).

Generally, there are three main processing methods:

• Natural Process
• Washed Process
• Methods between natural and washed: including semi-washed (wet-hulled), Brazilian pulped natural and honey process.

Natural Process

Selection, drying, hulling, sorting and grading.

Washed Process

Selection, pulping, fermentation, washing, drying, hulling, sorting and grading.

Wet-Hulled Process

The wet-hulled method is very common for Indonesian coffee beans and differs from typical washed and natural processes.

In washed, honey-processed or natural-processed coffee, the parchment layer is retained until the bean becomes dehydrated and hard, with moisture content dropping to 12%, or until it is stored for 1-3 months of maturation, before being removed.

In the wet-hulled process, however, the parchment layer is removed while the beans are still moist and soft, with a high moisture content of 30-35%, exposing the green beans directly, and drying then continues. The method was developed to suit Sumatra's humid climate and to speed up drying. The shortened drying time cuts the fermentation period, significantly lowering acidity while increasing body. The result is distinct caramel and fruit flavors with slight woody and herbal notes, which together make up the unique terroir of Mandheling.

Take Tiger Mandheling, for example.

Tiger Mandheling grows on hillside slopes at around 1,500 meters, where a humid tropical rainforest climate brings abundant rainfall and volcanic soil provides nutrients. Because of year-round humidity, the wet-hulled method is used to shorten drying. Brewed with 88-89°C water at sugar particle size in a Kono dripper, with a 1:14 coffee-to-water ratio and 30 seconds of pre-infusion followed by a one-stage pour, it produces distinct dark chocolate and creamy flavors with high clarity.

Pulped Natural Process

The natural process is difficult to control in terms of quality, while the washed process consumes a great deal of water: on average, 1 ton of coffee cherries requires 10-20 tons of water to produce approximately 200kg of coffee beans. Producing countries with limited water resources cannot afford that. In the 1990s, Brazil used its advantageous dry climate to invent the pulped natural process.

After multiple improvements, and following the version of the late Dr. Ernesto Illy, the pulped natural process works as follows. Coffee cherries are first screened in water tanks to remove defective floating cherries, then the skin, pulp and part of the mucilage layer are removed, followed by one hour of washing. Because the soaking and fermentation time is short, not all the mucilage is washed away and some remains on the parchment shell. The sticky parchment beans are then spread on drying patios, preferably on breathable African raised beds.

Take this West Java Amman Estate natural honey process, for example. Hand-picking is used to ensure consistency of the cherries. After picking, the outer skin is removed and the cherries are processed with the pulp retained, also known as pulped natural. After about a month of natural drying they are washed and otherwise processed, then stored for half a month before packaging. The sole purpose of the process is to create more complex, full-bodied flavors.

Honey Process

Brazil's pulped natural method spread to Central American countries such as Costa Rica and El Salvador, where it was improved and became known as the honey process.

The honey process involves drying green beans while retaining the mucilage layer. After the outer pulp is removed from the coffee beans, a viscous, gel-like substance remains. In traditional washed processing this would be washed away with clean water, but because some high-altitude regions have limited water, this method of drying directly with the mucilage was developed.

Honey-processed coffee has higher sweetness and sugar content than washed coffee, and its body is also relatively higher (assuming the same roast level).

Depending on the degree of mucilage removal, the length of drying (or the thickness of the drying layer) and how often the beans are turned during drying, honey processing is further divided into black honey, red honey, orange honey, yellow honey and white honey.

Based on the degree of mucilage removal:

Black honey: retains 80% of the mucilage. Some estates remove almost no mucilage for black honey, which requires the longest drying time, over 14 days. During the process, coverings are used to block intense sunlight and prevent drying too quickly, allowing a more complete sugar conversion.

Red honey: removes 25% of the mucilage (specific practices vary among estates), with about 12 days of sun exposure and possibly shade covers during the process.

Yellow honey: removes 40% of the mucilage and takes maximum sunlight for about 8 days.

Some regions and estates distinguish by drying thickness and turning frequency. For yellow and white honey, for example, both retain 20-30% of the mucilage:

Yellow honey: thick-layer drying, fewer turns and a longer drying time.

White honey: thin-layer drying, more turns and a shorter drying time.

Take this coffee from the Sumava Estate, where owner Francisco Men preserves most of the original forest within the estate to maintain ecological balance, and where the coffee shows rich fruit aromas with high sweetness. When brewing Costa Rican Black Honey with a V60: 15g of beans, a 1:15 coffee-to-water ratio, sugar particle size grind, brewed to 225g, using 37g of water for 30 seconds of pre-infusion. First stage: a medium water flow to brew 120g, extracting the floral and berry aromas from the front and middle sections. Second stage: a large water flow to extract a strong black tea flavor. The cup shows distinct tomato acidity and soft berry acidity, preserving a bright, delicate citrus aroma and a low-pitched raisin and nutty aftertaste, with strong sweetness.

As the coffee market pursues more extreme flavors, many experienced and capable professionals have begun controlling the details of honey processing to create higher-quality beans and to demonstrate the possibilities of coffee flavor.

Instruments such as sugar meters are used to determine the picking time of coffee cherries. Cherries of consistent maturity taste cleaner, sweeter red cherries increase the sweetness of the coffee, and riper fruit also adds fermentation aromas.

The honey process retains the cleanliness of the washed process. Though not as bright as washed, it increases sweetness and caramel flavors.

Summary of Green Bean Processing Methods

Acidity: Washed > Semi-washed > Honey > Wet-hulled > Natural

Sweetness: Natural > Honey > Wet-hulled > Semi-washed > Washed

Production Risk: Wet-hulled / Natural > Washed / Honey > Semi-washed

Equipment Costs: Washed / Semi-washed > Honey / Wet-hulled > Natural

Water Usage: Washed > Semi-washed > Honey / Wet-hulled

FrontStreet Coffee Recommendation

FrontStreet Coffee's roasted Indonesian West Java honey-processed coffee beans offer complete assurance in both brand and quality. More importantly, they provide excellent value: half a pound (227 grams) costs only about 118 yuan. At 15g of coffee per cup, one package yields 15 cups, so each cup costs only about 7 yuan. Set against the tens of yuan per cup charged in coffee shops, that is a genuinely conscientious recommendation.

For the classic wet-hulled expression, FrontStreet Coffee's Linton Mandheling comes from the Linton region of Sumatra. It is roasted medium-dark to soften the acidity and highlight a rich, aromatic character, with dark chocolate and caramel flavors alongside a wild herbal note that comes from both the growing environment and the processing method. The cup is low-acid, full-bodied, with a strong and lingering sweetness, and suits drinkers who dislike acidity.

At the highest grade, FrontStreet Coffee's PWN Golden Mandheling is produced by the PWN company, which buys only high-quality Mandheling green beans and selects them once by machine and then by hand, so every lot is specialty grade with even, plump, large and clear beans and a low defect rate. The PWN standard takes beans of screen size 18 or above as the base and requires fewer than 3 defective beans in a 300g green-bean sample, meeting the top G1 grade; on top of that, three rounds of hand-sorting remove all remaining defects, improving both the cleanliness and the sweetness. Roasted medium-dark, it carries a rich roasted aroma, and the brewed black coffee has a clean taste and full body, again ideal for those who do not care for acidic coffee.

To brew Golden Mandheling, a pour-over shows it at its best. FrontStreet Coffee suggests 87-88°C water, 15g of grounds, a 1:15 coffee-to-water ratio, a coarse-sugar grind, and a three-stage pour, which better expresses the full body and caramel sweetness. The first pour is 30ml, wetting all the grounds to let them degas; the second is 100ml, which brings out the golden foam and lifts the coffee bed; the final pour is 95ml, gently down the center, which raises the sweetness and rounds out the rich body with caramel sweetness and chocolate and nut flavors.