How Does Each Coffee Processing Method Change the Cup?

Coffee beans are the seeds inside coffee cherries, so the skin, pulp, pectin layer, and parchment must be removed before green coffee exists. That removal step is called coffee processing, and the method chosen shapes the final flavor. Natural, washed, semi-washed, and honey processing are traditional; anaerobic fermentation, barrel fermentation, and enzyme processing are newer additions.

Natural processing dries whole cherries in the sun for about a week before hulling, which keeps costs low but leaves results weather-dependent. Washed, semi-washed, and wet-hulled lots trade some of that fruit for clarity and structure, while anaerobic and barrel methods push layered, fermented notes. Knowing these differences gives buyers a clearer frame when tasting and comparing green coffee beans.

For coffee cherries to become green beans, they must go through a series of processing steps that remove the skin, pulp, pectin layer, and parchment. Different processing methods not only determine the appearance of the green beans, but also profoundly shape the flavor direction of the final cup. Traditional natural, washed, semi-washed, and honey processing each have their adherents, while in recent years new-style methods such as anaerobic fermentation and barrel fermentation have emerged endlessly, bringing more possibilities to coffee flavor. This article will systematically sort out the operational processes, advantages and disadvantages, and flavor characteristics of these processing methods, interspersed with examples of many representative products under the Front Street brand, to help coffee lovers build a clear cognitive framework for processing methods and have more direction when purchasing and tasting.

Coffee beans are essentially the seeds of coffee cherries, so the skin, pulp, pectin layer, and parchment must be removed one by one before green coffee beans can be obtained. At this point, the green beans are usually white, emerald green, or yellow, and only after roasting do they turn into dark brown roasted coffee beans. The above removal process is collectively called "processing," and different processing methods directly affect the final flavor of the coffee, which is precisely the core discussed in this article.

Traditional processing methods include natural, washed, semi-washed, honey processing, and so on, while in recent years more and more innovative techniques have been used to increase flavor layering, such as the currently much-watched anaerobic processing method, barrel fermentation, and enzyme processing, which can be described as endlessly varied and emerging one after another.

The natural processing method, as the name suggests, uses sunlight for drying. Red coffee cherries are placed in the sun to dry for about a week, with the specific duration flexibly adjusted according to weather conditions. After the skin and pulp are dried and darkened, the skin and pulp are removed with a huller, and finally defective beans are picked out to complete the process.

The advantage of the natural method is its low cost—there is no need to pay rent to the sun—and it is the oldest, most traditional processing method. But its disadvantages are equally obvious: it requires a large drying area, and rainy regions are not suitable for it. In addition, because it is difficult to precisely control the drying degree of each bean, the proportion of defective beans in rough natural batches is somewhat higher. In terms of flavor and mouthfeel, during the natural drying process the pulp undergoes a certain degree of fermentation, so it usually has richer fruity and vinous aromas, while acidity is relatively lower.

The Front Street Red Cherry Coffee Beans launched by Front Street are naturally processed Yirgacheffe, and their processing steps are more refined than traditional simple natural processing. Freshly picked red coffee cherries are first manually sorted to remove defective beans, overripe beans, and insect-damaged beans, retaining high-quality fruit. They are then sent to the drying site for processing. Different producing regions use different drying racks: some use tarps, some use raised beds, and the most common is the African drying bed. The drying process generally lasts 27 to 30 days, and is considered complete only when the coffee fruit turns dark purple and the moisture content drops to 11%. The taste of Front Street natural Yirgacheffe is more intense, with richer layering, a vinous fermented flavor, and higher sweetness as well.

It is often said that washed coffee beans have higher acidity and better cleanliness. Why exactly is that?

The washed processing method was originally developed to solve the problem that many regions lacked sufficient sunlight and could not carry out natural processing. In the washed method, impurities are first removed from the coffee cherries in a water tank, then the skin and pulp are stripped off with a pulper, but the pectin layer and parchment still remain attached, so the beans are placed in a fermentation tank to let microorganisms break down the pectin layer. After decomposition is complete, they are rinsed with water, then taken out to dry. After drying, the parchment is removed with a huller to obtain coffee beans. Finally, defective beans are likewise picked out.

The entire process—the water tank, fermentation, washing channels, and other stages—consumes a large amount of water resources, hence the name "washed." The benefit of washing is that the process is highly industrialized, precisely controllable, stable in quality, clean and clear in mouthfeel, and more prominent in fruity acidity. Because no pulp participates in fermentation during washing, the coffee beans retain more acidic aromatic substances such as malic acid and citric acid. In addition, washed coffee beans often have richer floral aromas.

The multiple steps of washing can remove bad beans, greatly reducing the proportion of coffee defects and making quality more stable. During drying, there is no pulp wrapping the outside, so the flavor has elevated acidity and higher cleanliness, highlighting the flavor characteristics of a single origin. Therefore, if you want to understand the "taste of terroir" or "regional flavor" of an origin, Front Street suggests starting with its washed batch.

Washing is a processing method that Front Street greatly favors, and dozens of coffee beans on the bean list are washed. If you want to taste the characteristics of washed beans, Front Street recommends a coffee bean from Ethiopia: Front Street Yirgacheffe Gotingding Coffee Beans. Washed processing gives Front Street Yirgacheffe a break from its previous unevenness, and the medium-light roast preserves a fresh citrus profile and elegant white floral aroma, with an overall bright and delicate flavor.

So what happens if natural and washed are combined?

Yes, we call it semi-washed, and in some cases it is also called honey processing. The semi-washed method is as follows: first remove impurities, skin, and pulp as in washed processing, but do not remove the pectin layer by soaking; instead use a mucilage remover to remove the pectin, then dry in the sun. After drying, use a huller to remove the parchment, and finally pick out problematic green coffee beans. Let us trace back: if you do not use a mucilage remover to remove the pectin and instead take it directly to dry in the sun, then it becomes honey processing! After drying, the pectin and parchment are removed together with a huller.

The key lies in this layer of pectin, because it is highly sticky and has a texture like honey, so it is called honey processing; it is not that any honey is added during processing. How much pectin layer is retained during washing becomes the key to the flavor differences in honey processing. If only about 10% of the pectin is retained for sun drying, it is called "white honey processing," and the coffee has a clean mouthfeel, closer to washed. If only about 25% of the pectin is retained for sun drying, it is called "yellow honey processing," because the coffee beans turn yellow. Retaining about 50% of the pectin is called "red honey processing"; retaining 100% of the pectin for sun drying is "black honey processing." The more pectin retained, the more difficult the processing and the longer the sun-drying time required. Compared with washed, the flavor is richer, more complex, and more variable.

Is semi-washed also called wet-hulled processing?

The coffee cherry harvest season in Sumatra happens to coincide with the rainy season, which is quite troublesome, so they developed another unique processing method. The steps before wet-hulling are the same as the washed method. Indonesians first remove the pulp from the coffee fruit, then ferment it in water for 3 hours. After washing off the mucilage, the green coffee beans with parchment are dried for a short time for 2 to 3 days. At a moisture content of 20% to 24%, in a semi-soft, semi-hard state, the parchment is hulled off the beans in parchment, and then drying continues until the coffee's moisture content drops to 13%, at which point it can be bagged.

Because the hulling machine uses relatively great friction to tear open the parchment layer clinging tightly to the green beans, and through the stirring of friction, the green beans are also more likely to be crushed or squeezed and damaged, especially at both ends, forming small gaps and causing "goat hoof" beans. The "naked beans" with the parchment removed dry very quickly, and at the same time are directly exposed to a humid environment, where various strains grow, giving Indonesian coffee its unique woody, spicy, and herbal notes—what we call "regional flavor."

I believe some friends are already curious about what the flavor of Southeast Asia is really like. If you have not yet tasted Front Street Mandheling Coffee, Front Street suggests starting with the small-pack, wet-hulled Front Street Indonesia Lintong Mandheling Staple Beans, which present the classic Mandheling flavor and are convenient for us to try at home.

After reading the above introduction, you will find that during processing, the pulp—especially the fermentation of the pectin layer—affects coffee beans a great deal, so people began to think hard about this matter. Anaerobic processing and barrel fermentation are among the more common new processing methods.

In anaerobic processing, coffee beans that have had the skin and pulp removed but still have the pectin layer are placed into stainless steel tanks, oxygen is pumped out, leaving only carbon dioxide, and anaerobic bacteria help the coffee beans ferment inside for about 18 to 24 hours. Of course, each estate's method and timing may be slightly adjusted (for example, not every estate necessarily has stainless steel tanks). In this process, great attention must be paid to the amount of pectin, temperature, pressure, pH, and fermentation time to prevent any slight error in flavor.

Anaerobic processing can produce coffee with very complex and diverse flavors, such as the recently common anaerobic natural, which can be regarded as adding some elements—such as fermented flavors—to the originally traditional natural flavor. The Front Street Colombia Flower Moon Night Coffee Beans launched by Front Street use anaerobic natural processing, with richer ripe fruit sweetness and acidity and fermented aromas.

Professional coffee knowledge exchange. For more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style).

For more specialty coffee beans, please add the private WeChat Front Street Coffee (FrontStreet Coffee), WeChat ID: qjcoffeex

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