How Does the Washed Coffee Bean Processing Method Work?

The washed method is one of the oldest and most common ways to process green coffee beans. Compared with natural sun-dried beans, washed coffee shows better cleanliness and a brighter, more lifted acidity, and it is somewhat more intensely acidic overall.

Natural sun-drying came first, but it relies on weather and easily suffers mold, rot, and insects, which kept quality unstable. Ethiopia's sun-dried beans once reached only Grade G3 before the coffee system reform. Standardized coffee bean processing, including washing, raised consistency, and Ethiopia's Yirgacheffe region shifted in flavor after the technique arrived.

The washed method is currently one of the most common and traditional ways of processing green coffee beans. Compared with natural sun-dried beans, washed coffee often has better cleanliness and a brighter, more lifted acidity. This article will systematically sort out the washed method from three angles: historical origins, the five-step processing flow, and flavor characteristics, and will also introduce the flavor transformation of Ethiopia’s Yirgacheffe region after the introduction of washed processing technology. The article also includes the pour-over parameters and flavor description for Front Street Coffee’s washed Yirgacheffe everyday drinking beans, suitable as an introductory reference for enthusiasts who are just getting into specialty coffee.

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Among the many green coffee processing methods, the washed method is the most widespread and also one of the oldest traditional processing methods. Generally speaking, coffee beans processed by the washed method have better cleanliness than natural sun-dried beans, show a brighter and more lifted acidity, and are also somewhat more intensely acidic. Taking Front Street’s bean list as an example, the quite popular Ethiopia Gedeb Worka cooperative coffee beans, Kenya Asali coffee beans, Panama Butterfly coffee beans, and Guatemala La Divina coffee beans all use the natural washed processing method.

Looking back at history, the oldest method of processing green coffee beans was actually traditional natural sun-drying. Put plainly, it means spreading freshly picked coffee cherries directly in a courtyard or on a rooftop to be exposed to the sun. This method requires almost no investment and can be done by anyone. But its drawbacks are also obvious—it relies completely on the weather, and in regions with changeable climates it is highly prone to mold and rot; in addition, because the fruit pulp is high in sugar, it easily attracts insects, making the quality of natural sun-dried coffee difficult to stabilize. Before Ethiopia’s coffee system reform, sun-dried beans could reach only Grade G3 at best.

As consumers’ pursuit of coffee quality continued to rise, while the quality of natural sun-dried processing was low and uneven, only standardized production could bring greater benefits. In 1740, the Dutch, who at the time controlled colonial coffee cultivation and the global coffee trade, began trying to process coffee beans with the washed method. They first discovered in the West Indies that soaking peeled coffee beans in water could remove the sticky mucilage layer, which could both shorten drying time and effectively prevent pests, diseases, bacteria, and mold from infecting the coffee beans. In that era, washed beans were synonymous with high quality.

In 1844, the coffee pulping machine was introduced, and the efficiency of washed processing was greatly improved as a result. However, washed processing is also costly and requires a large amount of water—on average, every 200 kilograms of green coffee beans uses 10 to 20 tons of water, so washed processing plants can only be built near water sources. It can be said that the birth of washed processing was only partly driven by flavor and mouthfeel; the main drivers were considerations of good-product rate, yield, and product standardization. To this day, the washed method is still one of the most common coffee bean processing methods on the market.

Before washing, floating selection is usually done first: pour freshly picked cherries into water and use buoyancy to pick out cherries that are not sufficiently ripe. Then use a pulper to remove the skin and pulp. At this point the coffee beans are slippery on the surface, and workers pour them into a fermentation tank to rest overnight. During mucilage fermentation, acidic substances are produced, and these substances prompt the mucilage to break down and separate from the beans. After fermentation ends, a small amount of mucilage still remains on the parchment beans, so they need to be scrubbed with tools for 30 to 60 minutes, combined with flowing water, to thoroughly clean off the pulp. Special channels plus the scouring force of water can remove low-density, poor-quality beans; then the high-quality coffee beans are drained and spread on raised beds or drying nets to dry, and once the target moisture content is reached, they can be bagged and stored.

Multiple stages of washed processing can screen out defective beans, greatly reducing the proportion of defects in the coffee, so the quality is more stable. Because the outer layer is not wrapped in pulp during drying, the flavor presents lifted acidity and higher cleanliness, and can highlight the terroir personality of a single origin. Therefore, if you want to understand the “taste of terroir” or “regional taste” of an origin, Front Street suggests starting with its washed lot. Take the well-known Yirgacheffe as an example: the Ethiopian everyday drinking beans launched by Front Street are selected from washed Yirgacheffe, using a medium-light roast, and after brewing present the fresh acidity of jasmine, citrus, and lemon, as well as honey-like sweetness.

As is well known, Ethiopia, located on the African continent, is extremely short of water resources, and traditionally coffee was naturally dried by the sun. Because the methods were rough, coffee beans were directly left to dry on mud ground or rooftops, making them prone to absorbing earthy flavors or over-fermenting due to uneven heating, ultimately dragging down coffee quality. In order to improve coffee quality, the Ethiopian government introduced more advanced washed processing technology and supporting equipment from Central and South America in 1972. This move allowed the flavor of Yirgacheffe coffee to show fresh citrus notes and elegant white floral aromas, bright and delicate overall. Yirgacheffe thus became independent from the Sidamo producing region and became the famous producing region renowned in coffee circles today.

When Front Street produces Yirgacheffe coffee beans, it usually uses the pour-over method. If you are a newcomer just entering the coffee world, Front Street recommends a washed Yirgacheffe everyday drinking bean, made from Ethiopia’s local heirloom coffee beans and medium-light roasted. Front Street’s everyday drinking bean series allows friends who have just come into contact with coffee to taste the basic flavors of the producing region at an affordable price, and the small-package design also avoids waste from not being able to finish drinking it.

Washed Yirgacheffe Pour-Over Suggestions

Dripper: V60 Water temperature: 92-93°C Dose: 15g Coffee-to-water ratio: 1:15 Grind size: fine granulated sugar size (sieve to 78% with a No. 20 sieve bowl)

For the first pour, add 30 grams of water and bloom for 30 seconds, then pour in 95 grams (the electronic scale shows about 125 grams), finishing the pour in about 1 minute. When the water level drops to 2/3 of the coffee bed, pour in the remaining 100 grams (the electronic scale shows about 225 grams), finishing the pour in about 1 minute 35 seconds. Drip filtration is completed at 2‘10”, remove the dripper, and extraction is complete.

Washed Yirgacheffe coffee flavor: on the palate there are jasmine, lemon, citrus, and green tea; as the temperature changes, there are lingering notes of berries, cream, and sugarcane, with obvious sweet aftertaste, and a clean, sweet mouthfeel.

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