How Many Coffee Bean Processing Methods Are There? Flavor Stories and Characteristics of Coffee Processing Methods

The world is filled with numerous coffee-producing regions. From careful cultivation to harvesting full, vibrant coffee fruits, and then transforming them into a delicious cup of coffee, a series of processing steps must be followed. Among these, the most crucial step is the coffee bean processing method. Not every region uses the same processing methods. For example, the wet-hulling method used for processing green coffee beans in the Indonesia region is currently common only in Indonesia and extremely rare elsewhere.

Why Coffee Bean Processing Methods Are Crucial

FrontStreet Coffee emphasizes that coffee bean processing methods are extremely important because, beyond uncontrollable factors like terrain and climate, the processing method is also a vital step in determining the flavor of coffee beans. FrontStreet Coffee uses the same Yirgacheffe region coffee beans from its menu to illustrate this point. Although both coffee beans come from the Yirgacheffe region, one uses the ancient natural processing method while the other uses washed processing. When you brew these two coffee beans using the same technique and brewing parameters, you'll discover that the washed-processed Yirgacheffe coffee beans have a very clean taste, while the natural-processed coffee beans have a richer body, more pronounced sweetness, and more intense floral aromas.

Differences Between Washed and Natural Processing

Although both washed and natural processing are among the three major coffee bean processing methods, their processing techniques are quite different. FrontStreet Coffee will briefly introduce these two processing methods. There are significant differences between washed and natural processing. Washed processing uses large amounts of water resources, while natural processing rarely uses water. In washed processing, coffee fruits are first poured into washing tanks or buckets, then buoyancy is used to remove unripe fruits or other impurities like wood chips that could affect the coffee flavor. Then, the selected coffee fruits have their skins and pulp removed by a depulper, and the coffee beans with mucilage are placed in washing tanks for approximately 18 hours of fermentation to break down the mucilage. After another washing of the coffee beans, they can be dried.

Natural processing, on the other hand, is simpler. After removing defective fruits, the coffee fruits are dried directly with their skins and pulp intact. When the moisture content of the coffee fruits drops to about 11%, the skins and pulp can be removed for storage. Many countries' special coffee processing methods are largely derived from these two methods, creating their own unique processing techniques.

Semi-Washed Processing

For example, Brazil created its own semi-washed method based on natural processing. After removing the coffee fruit skins and pulp, the beans are placed in water tanks for about an hour of washing. Due to the short time, mucilage still remains on the green coffee beans, which are then dried. The semi-washed processing method is very suitable for areas with water shortages, but as FrontStreet Coffee understands, this method can also easily cause coffee beans to deteriorate and pick up other off-flavors.

Honey Processing

Besides washed and natural processing, the third major coffee bean processing method is honey processing. Honey processing is mainly used by Costa Rica. The general coffee processing process is very similar to natural processing - first removing the coffee fruit defects, then directly preserving the mucilage without the fermentation process that requires clean water. This process of preserving mucilage and drying directly causes the mucilage's sugars to continuously adhere to the coffee beans, resulting in very pronounced sweetness in the coffee beans.

One of the coffee beans on FrontStreet Coffee's menu - the Musician Series Baha coffee bean from Costa Rica - uses honey processing. However, this Baha honey-processed coffee bean has an additional step, so its actual processing method is called raisin honey processing. Why add the word "raisin"? As FrontStreet Coffee understands, this coffee bean first preserves the complete coffee fruit and dries it directly. After drying, the skin and pulp are removed, then the mucilage is preserved for drying. Because the drying process allows it to slowly lose moisture in the natural environment like a raisin, it's called raisin honey processing.

Wet-Hulling Processing

Another special coffee bean processing method is the wet-hulling method from Indonesia that FrontStreet Coffee mentioned at the beginning. Because the environment is relatively humid, using natural processing would easily cause coffee beans to mold during the drying process. Therefore, local Indonesian coffee removes the coffee fruit skins and pulp first, then dries them. At this point, the moisture content of the green coffee beans is still very high. Then machines are used to remove the parchment, and the coffee beans with parchment removed undergo another drying to reduce their moisture content to about 12-13%, completing the processing.

Because the coffee beans have their parchment removed while still in a semi-dry state, the parchment at this stage is difficult to remove, and the coffee beans are very susceptible to compression damage, often resulting in "elephant beans" (also known as "goat hoof beans"), hence the name wet-hulling method. Therefore, FrontStreet Coffee also understands that it's precisely this wet-hulling method that gives Indonesia's Mandheling its unique flavor. However, during the green bean processing, only when handled well can it produce the rich body and Mandheling flavor. If coffee beans are not handled well during the wet-hulling process, Mandheling coffee can easily develop musty, earthy flavors.

Anaerobic Fermentation Processing

Another processing method that is now widely used is anaerobic enzyme processing. One of the coffee beans on FrontStreet Coffee's menu - Rose Valley coffee from Colombia - uses anaerobic fermentation processing. First, freshly harvested coffee fruits with defective beans removed are placed directly in sealed fermentation tanks for low-temperature fermentation at temperatures between 10-15 degrees Celsius. In an anaerobic environment, the decomposition speed of mucilage sugars slows down because the low temperature inhibits microbial growth. After more than three days of anaerobic fermentation, the coffee fruits in the tanks undergo natural processing, and after drying is complete, the skins and pulp are removed for storage. The anaerobic fermentation processing method has developed very rapidly in the coffee industry in recent years. At the 2018 WBC competition, five of the top six competitors used anaerobic fermentation processing. FrontStreet Coffee believes this also demonstrates the unique advantages of anaerobic fermentation processing.

Advantages of Anaerobic Fermentation

Because the fermentation process of traditional processing methods is relatively difficult to control due to numerous variables, the risks are also higher. During anaerobic fermentation, not only can parameters like time, temperature, and pH be controlled, but it can also produce flavors and textures that traditional processing methods cannot achieve, thereby reducing risks. However, the processing techniques for anaerobic fermentation are not yet mature and require continuous exploration.

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