How Coffee Beans Are Processed Before Roasting

Ever wondered why some coffees taste clean and bright while others are heavy and earthy? Much of that flavor starts long before roasting — during the critical phase when coffee cherries are turned into green beans. The method used to process those cherries has a huge impact on taste, quality, and even how long the beans can be stored.

There are two main ways green coffee beans are prepared: the washed (or wet) process and the natural (or dry) process. Washed processing, more expensive and labor-intensive, is typically used for higher-quality beans. The natural process is cheaper and mainly used for lower-grade or certain regional coffees.

Two Main Processing Methods: Washed vs. Natural

Coffee beans are processed in one of two primary ways before roasting: the dry (natural) method and the wet (washed) method. The dry method is the simplest and cheapest, used mostly for lower-grade beans, especially in regions like Brazil and Ethiopia. The wet method, more complex and costly, is favored for high-quality Arabica beans and is common across most specialty coffee-growing regions except parts of Indonesia, where some Robusta is wet-processed.

How the Dry (Natural) Method Works

The dry or natural method involves processing coffee cherries without removing the fruit before drying. Unwashed and unsorted coffee cherries are spread out to dry in the sun, typically on concrete patios, raised beds, or mats. This method is inexpensive and requires minimal equipment, but it demands careful management to prevent mold or over-fermentation. The cherries are left to dry until their moisture content drops to around 11%, a process that usually takes 2 to 4 weeks depending on weather conditions. Once dried, the beans — still encased in their dry husk, known as parchment — are stored until ready for milling and export.

How the Wet (Washed) Process Works

The wet or washed process is a multi-step method that removes the coffee cherry’s outer skin and pulp before the beans are dried. This begins within hours of harvest. First, the coffee cherries are sent through a pulper, a machine with fixed and moving surfaces (or rotating rods), that crushes the fruit and separates the beans from the outer flesh. This separation must occur within 12 hours, ideally, but no later than 24 hours post-harvest to avoid quality loss. The beans, still coated with a sticky mucilage layer, are then rinsed and sorted. Lighter or less dense beans may be separated using grading channels or machines like the Aagaard separator, which uses water density to sort beans by size and ripeness. Water is recycled in many setups.

Fermentation: Removing the Mucilage

After sorting, the beans undergo fermentation to dissolve the slimy mucilage layer surrounding the parchment. This happens in tanks and takes between 12 and 36 hours, depending on ambient temperature, mucilage thickness, and microbial activity. When complete, the beans feel rough like pebbles instead of slippery. Fermentation is a delicate stage — any contamination can ruin an entire batch. Equipment must be cleaned daily to prevent spoilage.

Drying Parchment Coffee

Once the mucilage is gone, the beans, still inside their parchment shells (containing about 15% moisture), must be dried down to around 11% moisture. This is done on patios, raised beds, or tables — similar to the dry method — and regularly turned to ensure even drying. In larger farms or rainy regions, mechanical dryers or ventilated cabinets with controlled airflow are used. Sun drying takes about 12 to 15 days and requires frequent turning. Direct sunlight must be managed to avoid cracking the parchment, often using tarps or shade during peak hours. The resulting beans are called parchment coffee, a stable form ideal for storage and export.

Storing Parchment Coffee

Parchment coffee must be stored in stable conditions to preserve quality. High temperatures and humidity above 70% can degrade the beans. Ideally, parchment coffee is kept in cool, dry environments at altitudes close to where it was grown. Arabica beans should not be stored in parchment form for more than 12 hours unless in controlled conditions, while Robusta can tolerate slightly longer storage. Most producers hold parchment coffee until just before export to maintain freshness and avoid unnecessary risk.

Hulling: Removing the Parchment

Before export, the parchment layer must be removed in a process called hulling. For wet-processed beans, specialized hullers are used since the parchment is tougher and harder to remove than in dry-processed beans. Two common types are friction hullers (like the Engelberg or African models) and compression hullers. Friction hullers work by crushing beans against blades or rods inside a cylinder, scraping off the hull. Compression hullers, more commonly used outside Brazil, feature a horizontal rotating disk with metal pins; beans are forced against these pins by centrifugal force, removing the parchment. Proper moisture levels are crucial here — too dry, and beans may crack.

Polishing: Optional Final Step

After hulling, a thin silver skin may remain on the beans. Some mills use polishing machines — similar to hullers but with copper drums instead of iron or steel — to remove this skin. Copper is gentler and can add a slight bluish tint to the beans. Polishing is mostly aesthetic and has little proven impact on cup quality, though some traditionalists argue polished beans look cleaner. Most specialty roasters skip polishing entirely, focusing instead on origin, processing, and roast profile.

Frequently Asked Questions

What are the two main methods of coffee bean processing?

The two primary coffee processing methods are washed (wet) and natural (dry). The washed process removes the coffee cherry's skin and pulp before drying, while the natural process dries the whole cherry, including the beans inside, before removing the dried husk.

Which coffee processing method is more expensive?

The washed (wet) process is more expensive due to the need for water, machinery, and labor to remove the cherry's pulp and mucilage before drying. It is generally used for higher-quality Arabica beans.

How long does it take to dry coffee beans?

Drying coffee beans can take anywhere from 12 to 15 days for sun-dried parchment coffee, or 2 to 4 weeks for natural (dry) processed cherries. Mechanical drying can shorten this time, depending on equipment and climate.

What is parchment coffee?

Parchment coffee refers to green coffee beans that have been dried with their protective parchment shell still intact. This shell is removed just before export through a process called hulling.

Does coffee polishing affect taste?

No, polishing the silver skin off coffee beans has almost no impact on the final cup flavor. While it was once thought to indicate higher quality, most specialty roasters do not polish beans today.

Why is mucilage removal important in washed coffee?

Removing the mucilage is essential in the washed process because it affects the bean’s texture, cleanliness, and fermentation. If not properly removed through fermentation or mechanical means, it can cause off-flavors and processing defects.

FrontStreet Coffee Beans Ideal for Exploring Processing Methods

Try FrontStreet Coffee’s Ethiopia Yirgacheffe (washed), which highlights the clarity and floral brightness typical of well-executed washed processing with notes of lemon, jasmine, and green apple. For natural processing, the Ethiopia Guji (natural) offers bold berry, blueberry, and fermented stone fruit tones from dry processing. Both showcase how processing shapes flavor. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.