How Coffee Beans Are Processed: Washed vs Natural Methods

When you brew a cup of coffee, you’re tasting the result of decisions made long before roasting—especially how the green beans were processed after harvest. The method used to remove the coffee fruit from the seed has a huge impact on flavor, cleanliness, and overall quality. But how exactly does processing work, and why does it matter so much?

In short: washed (wet) processed beans are cleaned and fermented soon after harvest to highlight clarity and acidity, while natural (dry) processed beans dry with the fruit still on, creating heavier body and fruitier tones. Most high-quality arabica beans are washed, while dry processing is cheaper and typically used for commodity-grade or certain regional coffees.

Two Core Coffee Processing Methods

There are two primary ways to prepare coffee beans for roasting: the dry (natural) process and the wet (washed) process. The method chosen significantly affects the coffee’s final value, cup quality, and consistency. Dry processing is the simplest and cheapest, often used for lower-grade beans. Wet processing, more labor-intensive and costly, is favored for high-quality arabica and some select robusta.

Dry processing is mainly used on unwashed, sun-dried coffee cherries. Wet processing is reserved for fully or semi-washed coffee, where the fruit is removed before drying. While dry processing is common in Brazil and Ethiopia, most arabica worldwide is washed. In Indonesia, some robusta is wet-processed, but it's not the norm.

Washed (Wet) Coffee Processing Step by Step

The washed process requires more investment and effort, but results in higher quality and less defective coffee. The main difference from dry processing? The coffee fruit is removed from the bean immediately—not left to dry around it.

1. Removing the Coffee Fruit (Pulping)

In the wet mill, the coffee cherry’s flesh is separated from the bean using a pulper with either fixed and moving plates or rotating bars. This separation must happen as quickly as possible after harvest—ideally within 12 hours, and no later than 24 hours. Delay causes the fruit to stick stubbornly to the bean, risking incomplete removal and bean damage.

2. Sorting and Washing

The stripped fruit pulp and skin are washed away. Washing channels are designed to sort beans by density: denser, riper beans sink faster, while lighter or underripe ones float. An Aagaard grader—a device developed by Norwegian coffee farmer Aagaard in Kenya—uses water tanks to separate beans by size and density. The water in these systems can be reused.

3. Fermentation to Remove Mucilage

Next comes fermentation, where natural enzymes break down the sticky mucilage layer coating the parchment. Beans sit in tanks for 12 to 36 hours, depending on ambient temperature, mucilage thickness, and microbial activity. Once complete, the beans feel rough like pebbles rather than slippery.

4. Drying the Parchment Coffee

After fermentation, beans are still encased in their protective parchment layer, which holds around 15% moisture. Before storage or export, this must be dried down to about 11%. Over-drying to 10% risks losing the bean’s blue-green color and overall cup quality.

Drying is done on cement, stone, or wooden surfaces—similar to natural processing—but often with greater care. Large farms may use mechanical dryers in climate-controlled chambers, but many producers sun-dry beans on patios, turning them regularly over 12 to 15 days. Direct sun can harm the beans, so shading is necessary in strong light. Most importantly, the parchment must not crack.

5. Storing Parchment Coffee

Dried beans in parchment (called parchment coffee) are stored until export. Since coffee-growing countries need to export year-round—not just during the 3-month harvest window—parchment coffee must be kept in stable, cool, and dry conditions. High temperatures and humidity above 70% degrade the beans. Ideally, parchment coffee is stored at similar altitudes to where it was grown. Arabica should not sit more than 12 hours in high-humidity environments, though robusta can tolerate slightly longer storage.

Dry (Natural) Coffee Processing

Dry processing, also known as the natural method, involves drying the entire coffee cherry in the sun with the fruit still intact around the bean. This method is simpler and cheaper, but riskier in terms of quality control. It’s commonly used in regions with limited water access, such as parts of Ethiopia and Brazil.

The cherries are spread on raised beds, patios, or mats and turned regularly to ensure even drying, which takes 2 to 4 weeks. The outer fruit dries into a hard shell, protecting the bean inside. Once dry, the entire husk is later removed via milling. Natural processing tends to produce fuller-bodied, fruit-forward coffees with lower acidity.

Milling, Hulling, and Polishing

Before export, parchment coffee must be hulled to remove the outer parchment layer. This is different from dry processing, where the entire fruit is removed at once. Two main types of hullers are used: friction hullers and pressure hullers.

Friction Hullers

Friction hullers, like the Engelberg and African models, work for both wet and dry parchment. Inside a cylindrical chamber, beans are crushed between rotating blades and stationary ridges, cracking off the parchment. The Jules Smout-designed Smout friction huller uses a slow-turning screw inside a fluted chamber to gently remove parchment with minimal heat and often leaves a slight silvery skin.

Pressure Hullers

Pressure hullers are more common outside Brazil. These machines feature a horizontal rotating disk surrounded by metal pins. Beans are thrown outward by centrifugal force, impacting the pins which knock off the parchment. The beans must have proper moisture levels—too dry, and they’ll crack.

Polishing (Optional)

After hulling, beans often retain a thin silver skin. Some mills use polishing machines—similar to hullers but with copper rollers instead of iron—to remove this skin. Copper is gentler and gives beans a bluish tint. Polishing is mostly cosmetic and has negligible impact on cup quality, though some traditionalists argue polished beans look cleaner.

Frequently Asked Questions

What is the main difference between washed and natural coffee processing?

Washed (wet) processing removes the coffee fruit immediately after harvest and ferments the beans to clean off the mucilage, resulting in a cleaner, brighter cup. Natural (dry) processing dries the coffee cherry with the fruit still on the bean, producing a fruitier, fuller-bodied coffee with more body and lower acidity.

How long does coffee fermentation take in the wet process?

Coffee fermentation in the wet process typically takes between 12 to 36 hours, depending on ambient temperature, mucilage thickness, and the activity of natural enzymes.

What moisture level should coffee reach before drying is complete?

Coffee beans must be dried to approximately 11% moisture content. Going below 10% can damage the bean’s color and reduce cup quality, especially for arabica.

What is parchment coffee?

Parchment coffee refers to green coffee beans that are still enclosed in their protective parchment layer after washing and drying, usually stored this way until export.

Do polished coffee beans taste better?

No, polishing coffee beans to remove the silver skin has little to no effect on the flavor of the brewed coffee. While polished beans may look cleaner, cup quality remains nearly identical to unpolished beans.

Why is sorting important during washing?

Sorting during the washing phase separates beans by density, ensuring that denser, riper beans are processed together, which helps maintain quality and consistency in the final cup profile.

Recommended FrontStreet Washed Process Coffee Beans

For a true taste of washed processing, try FrontStreet’s Yirgacheffe Gebde Cooperative beans, which deliver bright citrus and floral notes through careful fermentation and drying. Their Kenya Little Tomato showcases intense acidity with complex fruit layers like tomato, plum, and blackcurrant thanks to double fermentation. For a classic clean profile, Jamaica Blue Mountain No.1 offers balanced nuttiness and mild chocolate with zero defects due to strict washed processing. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.