Six Common Coffee Processing Methods

Coffee processing methods come in rich varieties, with no fewer than five that we're all familiar with! Such as natural, washed, honey process, and so on. We all know that different processing steps can lead to completely different flavor profiles in coffee. However, before the concept of specialty coffee became widespread, the development of coffee processing methods worldwide served only one purpose—drying coffee beans to make them easier to store, and that's all.

But with the popularization of specialty coffee concepts, people gradually realized that processing methods have a direct impact on coffee flavor. Therefore, many places no longer simply choose coffee processing methods solely for the purpose of drying, but also to achieve ideal flavor profiles while drying. So in today's article, FrontStreet Coffee will revisit six common coffee processing methods—their origins, operations, and characteristics!

Natural Process

Natural processing is always introduced first because it's the oldest processing method. For centuries, all coffee in the world used natural processing. Back then, it wasn't even called the "natural method"—just like drying peanuts, it was simply a common drying process.

The steps of natural processing are very simple. After coffee cherries are picked, they are directly sun-dried. Once the entire coffee fruit is completely dry, machines are used to crush the skin, pulp, and parchment layer to extract the coffee beans, completing the process. The drying time generally depends on the local sunlight intensity and duration (also affected by different processing steps). For example, the sunlight in Ethiopia is relatively abundant, so the coffee bean drying time is about 3-4 weeks. The advantages of natural processing are very obvious—it only requires a location with long hours of sunlight. Additionally, since the skin and pulp surround the coffee beans throughout the drying and fermentation process, the resulting coffee develops very rich flavor profiles. However, its disadvantages are also prominent: one is its strong dependence on weather, and the other is that because fermentation control is relatively low, the final quantity of high-quality coffee beans is relatively smaller, making them more expensive. (A customer once asked FrontStreet Coffee why natural-processed red label is more expensive than washed red label—this is one of the reasons.)

Although natural processing only requires sunlight, for most coffee-producing countries, this is a difficult requirement to meet, such as in the West Indies. When coffee became widely cultivated in the West Indies, local farmers naturally had to process coffee. However, due to the local humid and rainy weather with short sunlight hours, the time required for sun-drying coffee cherries was greatly extended. This led to easier spoilage during the drying process because of the humid environment causing mold. So by the mid-19th century, the "washed method" was born.

Washed Process

The biggest difference between washed and natural processing is whether the coffee beans need to have their skin and pulp removed before drying, which can significantly shorten the drying time required for the beans (half of regular natural processing). The birth of washed processing also benefited from the Industrial Revolution. In 1845, the world's first coffee pulper machine was invented in Jamaica, and from then on, washed processing could successfully emerge.

Traditional washed processing is simple yet refined. Before formal processing, flotation is used to screen out defective fruits. Then a pulper is used to remove the skin and pulp of selected coffee cherries. Subsequently, coffee beans with mucilage are placed in water tanks for fermentation (to remove the mucilage). After fermentation is complete, workers wash the coffee beans to remove residual mucilage on the surface. Once washing is complete, the coffee beans are moved to a drying patio for drying. Finally, only the parchment layer needs to be removed from the coffee beans, and the washed processing is complete.

Because washed processing doesn't allow coffee beans to ferment excessively during processing, the final coffee can have a cleaner profile, meaning the coffee can better showcase its original flavor characteristics. Washed processing has given rise to many branches, and different countries and places use different variations of washed processing. For example, Kenya's washed processing is nicknamed K72, where coffee beans undergo two washing soaks during processing, with soaking times often reaching 72 hours, hence the name K72, or "Kenya-style 72-hour washed processing" (details can be found by clicking the blue text).

Washed processing is great in every aspect except for one drawback: wastewater. On average, every ton of coffee beans requires 10-20 tons of water. Therefore, for countries with limited water resources, washed processing is quite a luxury. But one country was very clever—it invented a processing method that could achieve similar results without using excessive water resources. That's right, this country is Brazil, and the processing method invented by Brazil is called "pulped natural"!

Pulped Natural Process

The pulped natural method invented in Brazil, as the name suggests, adopts both natural processing workflow and washed processing steps, allowing for both reduced water usage and significantly shortened drying time. Because Brazil's natural processing was criticized for being very rough for a long time, and at the same time they couldn't use excessive water resources, in 1990, Brazil invented the pulped natural processing method.

The specific method involves floating the harvested coffee cherries, then using a pulping machine to remove the coffee's pulp, skin, and part of the mucilage, followed by placing the coffee beans in water tanks for an hour-long soak. Since the soaking time is not long, most of the mucilage remains on the surface of the coffee beans. Even so, because the skin and pulp have been removed, the coffee beans can significantly shorten drying time during subsequent drying, greatly reducing the chance of spoilage, and the coffee thus achieves a relatively cleaner profile (compared to natural processing). This is precisely why FrontStreet Coffee chose a pulped natural FrontStreet Coffee Brazil Red Bourbon as the Brazilian representative in FrontStreet Coffee's regional daily coffee series.

Wet Hulled Process

Most friends have asked at FrontStreet Coffee stores whether pulped natural can also be called semi-washed. Theoretically, yes, but in most cases, semi-washed refers to wet hulling. Wet hulling is a unique coffee processing method in Indonesia. Due to the extremely harsh local weather (for coffee beans)—humid, rainy, and with very high humidity—drying coffee beans with parchment becomes very time-consuming. Additionally, Indonesia is a major coffee-producing country with huge output. Like Brazil, to sell coffee beans quickly for cash, they needed a processing method that could dry coffee beans rapidly. However, the above methods were all too time-consuming for Indonesia, so they developed a unique processing method based on their understanding—wet hulling.

The steps of wet hulling are the same as washed processing in the first half: first floating, then removing skin and pulp, then placing coffee beans with mucilage and parchment in water for 12-36 hours to decompose the mucilage. After decomposition, coffee beans with only parchment are spread under the sun for drying. When the coffee bean moisture content drops below 50%, a hulling machine is used to remove the parchment layer from the coffee beans. Finally, another drying session reduces the bean moisture to below 12%, completing the process.

Because removing the parchment layer when beans have high moisture content is quite difficult, the hulling machine's operation is very rough, easily causing coffee beans to be squeezed and damaged during dehulling, becoming "elephant beans." Although elephant beans may not look attractive, they don't fall into the category of defective beans. (But they do increase the risk of coffee bean contamination.) Although wet hulling allows Indonesian coffee beans to dry quickly, the process is very cumbersome and not refined. This easily leads to coffee bean contamination, and the defect rate of processed coffee beans is much higher than the above processing methods, which is why manual sorting of coffee beans is necessary. Interestingly, the flavors resulting from these factors have actually become the aromatic characteristics of Indonesian local coffee beans. The unique mellow aroma and thick mouthfeel of FrontStreet Coffee's Indonesia Lindong Mandheling are bestowed by the wet hulling process.

Honey Process

This processing method, which sounds delicious, originated in Costa Rica. Costa Rica's main processing method was initially washed, but due to the continuous downturn in the coffee market at the end of the 20th century, local farmers, in order to obtain more income to sustain their livelihoods, no longer sold coffee cherries to local washed processing stations but chose self-production and self-sales to earn more income. Then, honey processing, which doesn't require excessive investment, was born under this background. Honey processing evolved from Brazil's pulped natural. Its biggest difference from pulped natural is that coffee beans don't come into contact with any moisture after floating. The "honey" in honey processing doesn't describe the sweetness of the processed coffee, but rather during processing, the mucilage coating the coffee beans resembles honey, hence the name "honey processing."

The steps of honey processing are very simple. First, harvested coffee cherries are floated. After removing impurities and defective fruits, they undergo depulping while retaining mucilage. Then the beans are moved to under the sun for drying. After drying to the specified moisture content, hulling can be performed to extract the beans, completing the process. Because the drying time and fermentation degree of honey processing are between natural and washed processing, honey-processed coffee beans often perform between natural and washed processing. Generally, honey-processed flavor profiles tend toward the complexity of natural processing, while the mouthfeel is closer to the thickness and cleanliness of washed processing.

FrontStreet Coffee also often mentions that honey processing is divided into four different types: yellow honey, red honey, white honey, and black honey. Their main difference lies in the degree of mucilage retention. Because mucilage contains sugar, which changes color after oxidation, the amount of mucilage retained during coffee bean processing directly affects its color depth during processing. The more mucilage, the more oxidized sugar, thus the deeper the appearance color of coffee beans, and the flavor profile will also be more complex.

Anaerobic Process

Unique processing methods such as carbon dioxide maceration, red wine anaerobic, lactic acid fermentation, alchemist, enzyme, heat/cold shock, and others mostly belong to anaerobic processing. Anaerobic is currently a very popular processing method. Because most anaerobic-processed coffee beans have unique flavors different from conventional ones, this special processing method has been popular since 2015 when it first appeared on competition stages and won championships, gaining recognition.

The specific methods vary from person to person, and different estates and places use different processing methods because their combination approaches are very diverse, so FrontStreet Coffee won't share overly detailed anaerobic processing steps here. However, most anaerobic processing adds anaerobic fermentation steps before/during conventional coffee processing. By placing coffee cherries/beans in an oxygen-free environment for fermentation, the degree and direction of fermentation can be controlled, allowing coffee beans to develop the flavor profiles desired by producers. Generally, the anaerobic processing process is directly "concentrated" by producers in the name. For example, anaerobic natural means adding anaerobic fermentation to the natural processing steps; similarly, anaerobic washed adds anaerobic fermentation to the washed processing steps; double anaerobic natural means coffee beans undergo two fermentations during natural processing, and so on.

The degree of bean fermentation determines the intensity of its fermentation aroma. The deeper the fermentation degree, the stronger the fermentation aroma in the coffee, and vice versa. For example, FrontStreet Coffee Ethiopia Santa Venezi in FrontStreet Coffee's bean list, although using anaerobic natural processing, doesn't give a sense of fermentation aroma when brewed, but more of a tropical fruit juice sensation. Another coffee in FrontStreet Coffee's bean list, FrontStreet Coffee Orange Oak Barrel (now sold out), emitted a strong fermented wine aroma. The above are six common coffee processing methods in daily life. Which method do you prefer for processed coffee beans?

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