Specialty Coffee Bean Processing Methods Coffee Refinement Methods

The fruit of the coffee tree contains a pair of elliptical seeds at its center, covered by outer skin, inner pericarp, and pulp. Unprocessed mature fruits will quickly spoil, so the purpose of processing is to enable long-term storage of coffee beans, facilitating storage and distribution.

Figure (1) Coffee fruit

After coffee cherries are harvested, they must be processed immediately. Processing involves removing the outer skin and pulp from the coffee fruit, then taking out the seeds and removing their husks - this is what we commonly call green coffee beans. After processing, the coffee beans are still green beans, which are then roasted to produce the various flavored coffee beans we normally drink.

1. Coffee Processing Methods

Coffee processing methods are mainly divided into three categories: dry method, wet method, and semi-washed method. Generally, 5000KG of coffee fruit can yield 1000kg of green coffee beans.

1.1 Dry Method

The dry method is a traditional coffee bean processing technique where harvested fruits undergo natural sun drying, sometimes supplemented with mechanical drying. The process is: Harvest → Drying field (sun exposure) → Hulling machine (removing pulp, etc.) → Grading (electronic bean sorter or manual selection, sieve screens, etc.) → Export.

Figure (2) Dry method coffee beans

Green beans processed by the dry method tend to have a yellowish color, with coffee bean moisture content generally around 11%-12%. The advantage is that sun-dried beans relatively have better sweetness and body, while also having less acidity, which many coffee enthusiasts love. The disadvantage is that due to the use of manual and natural processing methods, sun-dried beans may not look appealing in appearance, have poor market presentation, and exhibit unstable quality with significant variations.

Figure (3) Dry method coffee beans close up

1.2 Wet Method

The wet method is currently the most popular processing technique, with most specialty coffee beans choosing this method. The wet coffee processing process is: Harvest → Water tank (removing impurities and unripe beans) → Pulping machine (removing pulp and impurities) → Fermentation tank (removing mucilage attached to the inner pericarp) → Washing pool (selecting light-weight and hard-textured beans) → Drying field (or drying machine) → Hulling machine (removing inner pericarp) → Grading (electronic bean sorter or manual selection, sieve screens, etc.) → Export.

Figure (4) Wet method drying field

Coffee beans processed using the wet method have a more uniform appearance, with fewer impurities and defective beans, and moisture content generally around 16%. The advantages are less off-flavors, clean taste, and bright fruit acidity; the biggest disadvantage is that during the fermentation process, coffee beans can easily pick up sour and astringent flavors, and one fermented bean can ruin 50 grams of beans.

Figure (5) FrontStreet Coffee Yirgacheffe G2/Wet method

1.3 Semi-washed Method

The semi-washed method is also known as the "honey processing method" and represents a compromise between the dry and wet methods, eliminating the fermentation step of coffee cherries found in the wet method. Harvest → Water tank (removing impurities and unripe beans) → Pulping machine (removing pulp and impurities) → Washing pool (selecting light-weight and hard-textured beans) → Drying field (or drying machine) → Hulling machine (removing inner pericarp) → Grading (electronic bean sorter or manual selection, sieve screens, etc.) → Export.

Figure (6) Coffee cherries after pulp removal

The quality of honey-processed beans is more stable than dry-processed beans but not as good as wet-processed ones. This method of processing coffee beans has recently gained popularity among coffee enthusiasts, offering sweet taste, rich crema, and is suitable for extracting espresso base. The advantages are its ability to很好地还原 the original flavor of coffee beans, with stronger coffee sweetness and prominent red wine notes. The disadvantage is that after removing the outer skin of coffee berries during drying, coffee beans are very susceptible to contamination and may potentially mold.

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