Green Coffee Bean Processing Methods: What Are the Different Coffee Processing Techniques and Their Unique Characteristics

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FrontStreet Coffee - Introduction to Coffee Processing Methods

Natural Process

Due to local water resource limitations, this oldest processing method is still used in many countries today. Freshly picked coffee cherries are simply spread over large grounds and exposed to sunlight. To prevent the cherries from rotting, they are constantly raked throughout the day and covered at night to prevent moisture from possible rain. Depending on weather factors, processing each batch of coffee cherries may take several weeks. Until the moisture content of the cherries drops to 11%, the dried cherries are transported to warehouses for storage.

Washed Process

In the washed processing method, coffee cherries are picked and only the pulp with the inner parchment is retained and dried. This involves several steps. First, fresh coffee cherries pass through a pulping machine that separates the outer skin and pulp. The pulp is washed with water and then dried under shading. Coffee beans are transported in water channels and separated by weight, with lighter beans floating on the water surface while heavier, mature beans sink to the bottom.

Then the coffee beans pass through a series of rotating drums that separate them by size. After separation, the coffee beans are transferred to large fermentation tanks filled with water. Depending on various factors such as bean condition, climate, and altitude, these coffee beans will remain in the fermentation tanks for 12-48 hours. The purpose of this step is to remove the smooth mucilage layer (called the pectin layer) still attached to the parchment. Enzymes naturally produced during fermentation in the tanks will break down the pectin layer. When fermentation is complete, the coffee beans will feel rough rather than smooth. At this point, the coffee beans will be rinsed through another water channel. They are then ready for drying.

If coffee cherries are processed using the washed method, the pulped and fermented raw beans must be dried to a moisture content of about 11% to be suitable for storage. These beans are still wrapped in the parchment layer (inner skin) and can be spread on patios or ground for sun-drying, with regular turning, or dried using large drum dryers. When the coffee beans are dry, they are called "parchment coffee" and are packed in sisal or jute bags for export.

Honey Process

When Costa Rica invented the honey process, it was to enhance the sweetness and fruit aroma of coffee beans. This is because slowly drying coffee beans with pectin outdoors is an important step in the honey process. This step allows the beans to fully absorb the fruit aroma and sugars from the pectin layer.

Therefore, from the perspective of flavor impact, the name "Honey Process" is well-deserved. However, some believe that this processing method is called honey process also because coffee beans with pectin look like they're coated in honey.

The honey process is very troublesome, requiring coffee farmers to remove the coffee fruit skin while preserving as much pectin as possible. Then, the coffee beans with the pectin layer are placed directly on outdoor elevated racks for long-term exposure and air-drying. During the 1-2 week exposure process, to ensure even drying of the coffee beans, the shell beans must be turned every few hours. After dehydration, the coffee beans are placed in wooden containers for maturation. In contrast, the semi-natural process is much simpler. During the drying process, the semi-natural method relies on machine drying, with only 2-3 days of exposure on drying beds, while also scraping off more pectin.

Knowledge Point: According to the degree of pectin retention, honey processing is divided into yellow honey, black honey, etc.

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