How Do the Three Green Coffee Bean Processing Methods Differ?

Natural, washed, and honey processing remain the foundation of specialty coffee, even as new techniques appear. Natural processing dries the whole fruit in the sun for about four weeks without removing skin or pulp, demanding a very dry climate. Washed and honey methods remove parts of the fruit before drying, which changes the flavor direction of the final cup.

Indonesia also relies on wet hulling, a regional method rarely used elsewhere, and there are offshoots like semi-washed, which derives from natural processing, and natural washed, which sits in the washed family. Each route leaves different sugars and compounds on the bean, so the same variety can taste fruity, clean, or syrupy depending on how it was handled.

The processing method of green coffee beans directly determines the flavor direction of the final cup. Although the modern coffee industry continually produces various novel special processing techniques, the three traditional methods of natural, washed, and honey processing remain the cornerstones of the specialty coffee world. In addition, a unique regional method known as wet hulling is widely used in Indonesia. This article will systematically outline the specific operational procedures, quality characteristics, and flavor differences of these processing methods, while also introducing semi-washed, which derives from natural processing, and natural washed, which belongs to the washed system. The article will also incorporate several representative coffee beans from the Front Street brand to help readers more intuitively understand how different processing methods perform in actual flavor.

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Today, coffee processing methods are becoming increasingly diverse, and with technological advances, various special processing methods are emerging one after another. However, from the perspective of traditional green coffee bean processing, the most basic classifications can generally be grouped into three types: natural, washed, and honey processing. There is also another special technique that is relatively rare in other producing regions but commonly used in Indonesia—wet hulling of coffee beans. Below, Front Street will explain these coffee bean processing methods one by one.

1. Natural Processing Method

Characteristics: Natural sun-dried processing method: retains all substances

The basic process is: after the coffee fruit is harvested, no treatment is done to remove the skin or pulp, and it goes directly into the sun-drying stage. This is the oldest known processing method. The entire drying cycle usually needs to last around four weeks. The operation process must be extremely meticulous and rigorous. The natural sun-drying method has very high requirements for local climate conditions and needs an extremely dry environment. In some producing regions, people use dryers to assist in drying the fruit (the hot air produced by the dryer can speed up drying and also makes it easier to control the degree of drying). For example, coffee beans from Ethiopia are often processed naturally, and the naturally processed Red Cherry coffee beans listed by Front Street use this ancient processing method.

Semi-washed processing also derived from natural processing, with Brazil uniquely creating semi-washed: its characteristic is the natural removal of mucilage. Brazil has a vast coffee planting area and mostly uses mechanical harvesting for economic efficiency. When 75% of the fruit in the coffee plantation turns red, mechanical harvesting begins, followed by the same preliminary operations as the washed method, that is, moving the fruit into water tanks to remove floating beans, screening out sinking beans, and then using large pulping machines to remove the pulp and take out the beans covered in mucilage.

Next, the sticky beans are moved to an outdoor drying yard. Brazil's climate is dry, and after about one day the sticky mucilage on the surface of the beans hardens. Then a large amount of manpower is used to turn them over repeatedly, and after about two to three days the beans can reach a certain degree of dehydration. They are then further dried with a dryer, after which the beans are stored for about ten days for further aging in order to stabilize quality. Before export, the parchment (that is, the bean pod) is removed, and the coffee beans are taken out, graded, and packaged. Front Street has a Brazil Queen Estate coffee bean that uses the distinctive semi-washed method, so this Front Street Brazil Queen Estate has a relatively full body and a noticeably sweet taste.

2. Washed Processing

Characteristics: Uses washing and fermentation methods to remove the skin, pulp, and mucilage.

The basic steps are:

(1) Bean selection:

Place the harvested fruit in a water-filled tank and soak for about 24 hours. At this point, the ripe fruit will sink, while unripe and overripe fruit will float up and can be removed.

(2) Remove pulp:

Use a machine to remove the skin and pulp, leaving only the coffee beans wrapped in the parchment. At this point, there is still a layer of mucilage on the outside of the beans, and the washing process is meant to wash away this layer of mucilage. (3) Fermentation:

The mucilage has strong adhesion and is not easy to remove. It must be left in the tank for about 18-36 hours to ferment and break down the mucilage. There are two fermentation methods, namely wet fermentation and dry fermentation; the former adds water, while the latter does not. During fermentation, the seed and the internal pulp undergo special changes, and this is the step in the washed method that most affects coffee flavor.

(4) Washing:

Farms using the washed method must build washing pools and be able to introduce a continuous supply of fresh water. During processing, the fermented beans are placed into the pool and moved back and forth, using the friction of the beans and the force of flowing water to wash the coffee beans until they are smooth and clean.

(5) Drying

After washing, the coffee beans are still wrapped in parchment and have a moisture content of 50%, so they must be dried to reduce the moisture content to 12%, otherwise they will become moldy and spoil. A better processing method is to use sunlight drying. Although it takes 1-3 weeks, the flavor is especially good and it is quite popular.

(6) Hulling

Once the beans are dried, they can be stored in a warehouse or sent to a factory for hulling to remove the parchment and silver skin. Finally, as with natural processing, washed coffee also has a sorting and grading process to remove defective beans and ensure better quality, before being sold to exporters and shipped around the world. Washed processing is very suitable for regions with abundant water resources, such as China's Yunnan region, which uses washed processing. In recent years, the popularity of Yunnan coffee has remained high, and Front Street also has several coffees from the Yunnan region. Among them is a Front Street 2013 Typica coffee that uses the classic washed method to process green coffee beans. Because washed coffee beans have a relatively clean and bright taste and can very well represent the basic flavor of the producing region, most coffees in Front Street's daily drinking bean series use washed processing.

In addition, there is also a natural washed method, which uses a high-pressure washing machine to process coffee beans and is very common in Brazil. Natural washed is very close to washed, with the difference being that natural washed uses a high-pressure washing machine to remove the mucilage on the surface of the coffee, thereby skipping the fermentation stage. Many green coffee bean processing companies in Brazil and Colombia have applied for patents for this method and have become monopoly enterprises in the local natural washed processing field.

This method uses far less water than the washed method, so some people habitually call it "semi-dry." Because it does not undergo fermentation, the coffee beans do not have (or have only extremely low) fermentation risk, and the overall quality of the coffee is more consistent. Unfortunately, because the coffee does not ferment, the taste tends to be flat.

3. Honey Processing

Characteristics: Removes the skin and pulp, retains part or all of the mucilage (pulp natural ≈ honey processing)

Today, almost all producing regions in Costa Rica use honey processing. This method is also widely spread throughout Central America. Because the surface mucilage of coffee beans is extremely sticky and high in sugar, people usually call it "honey." During honey processing, the coffee retains part or all of the "honey" while drying. Because the mucilage dries very quickly, the coffee beans almost do not ferment during the drying process. Coffee beans processed this way have slightly higher acidity than natural washed, but much lower than washed and natural sun-dried processing, so there is still a big difference between washed, natural, and honey-processed coffee beans. Because the coffee taste brought by Costa Rican honey processing is very popular, Front Street has also listed coffee beans from the Costa Rica Musician series.

Grading of green coffee beans after honey processing. There are 3 levels in total: yellow, red, and black. The variation in color depth comes from the length of light exposure during the coffee drying process. "Yellow honey" has 25% parchment, "red honey" 50%, and "black honey" 100%. Therefore, from "yellow honey" to "black honey," the required drying time is longer and the management requirements are more stringent.

The reason it was said earlier that pulp natural ≈ honey processing is that, in a narrow sense, pulp natural is limited to Brazilian coffee. Brazil's pulping machines generally do not have the function of adjusting the pulping aperture, and under default conditions they scrape off most of the pulp, which is the "yellow honey" level.

[Yellow honey processed green coffee beans] have the longest light exposure time. A long light exposure time means higher heat, so this kind of coffee can be dried within 1 week. In general, the drying time of coffee depends on local climate, temperature, and humidity conditions.

[Red honey processed green coffee beans] have a drying time of 2-3 weeks, usually due to weather conditions or being placed in the shade. If the weather is sunny, growers provide shade to block part of the sunlight in order to reduce light exposure time.

[Black honey processed green coffee beans] are placed in the shade to dry for the longest time, and the light exposure time is also the shortest. This kind of coffee has a drying time of at least 2 weeks. The processing of black honey green coffee beans is the most complex and has the highest labor cost, so the price is the most expensive.

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