How Washed Coffee Beans Are Dried and Processed After Washing

Once coffee cherries are washed and fermented, the beans still sit inside a tough, protective layer called the parchment — and that layer holds around 15% moisture. That’s too wet for safe long-term storage. So what happens next? How do producers dry, mill, and prep those beans for export without ruining their quality? Here’s the full breakdown of the post-wash process that turns wet parchment into export-ready green coffee.

In short: after washing, coffee beans are dried with the parchment on until their moisture drops to around 11%. This can take 12–15 days sun-drying or longer with machines. Then the beans are stored as parchment coffee, milled just before export, and optionally polished — though polishing doesn’t improve cup quality.

Why Parchment Coffee Must Be Dried to 11% Moisture

Right after the wet processing (which includes fermentation and washing), coffee beans remain encased in their inner husk, known as parchment. At this stage, the parchment still holds about 15% moisture. To prevent mould, quality loss, or over-drying damage, that moisture must be reduced to roughly 11%.

If arabica beans are dried too far — down to just 10% moisture — they can lose their natural blue-green colour and suffer in both appearance and cup quality. That 11% target is critical for stability during storage and transport.

How Parchment Coffee Is Dried in the Sun or by Machine

Drying parchment coffee is similar in method to natural drying, but the beans are still in their husks. The most common method is spreading the beans in a thin layer on cement pads, stone surfaces, wooden tables, or trays, then drying them in the sun.

On larger farms or in rainy regions, mechanical dryers are used. These dryers blow controlled air over beans housed in climate-controlled chambers. Sun drying requires regular turning of the beans and typically takes 12 to 15 days. One key rule: never let the sun get too strong — if it does, the beans must be covered. Most importantly, the parchment must not crack during drying.

Storing Parchment Coffee Before Export

Once dried, the beans are referred to as parchment coffee — named for their papery husk. They’re usually kept in this form right up to the export stage.

Since coffee-growing countries often need to export year-round rather than just during the harvest season, parchment coffee must be stored in very stable conditions. High temperatures and humidity above 70% can quickly damage the beans. For that reason, parchment coffee isn’t typically stored at the farm, unless there’s no other option.

High-altitude-grown beans should be kept at similar elevations to their origin, as they’re especially sensitive to humidity. Under proper conditions, arabica beans shouldn’t be stored as parchment for more than 12 hours, while robusta can last a bit longer.

Milling: Removing the Parchment Layer Before Export

Before coffee can be exported, the parchment layer must be removed — a step called milling or dehulling. This process also clears away any leftover outer layers and cleans the beans.

Removing the parchment is harder immediately after wet processing than after drying, so different types of hulling machines are used. The two main kinds are friction hullers and pressure hullers.

Friction hullers, such as the Engelberg and African models, work for both wet and dry beans. In these machines, beans are crushed between rotating cylinders fitted with blades and ridges, scraping off the hull.

Parchment coffee is most often milled using a Smout friction huller. Invented in 1844 by Belgian-born Jules Smout, who lived in Guatemala, this machine uses a slowly rotating screw inside a lined chamber. The screw moves beans against reverse-threaded walls, gently removing the parchment with minimal heat buildup due to its low rotation speed.

Other hullers include roller-type machines (mainly for dried beans from South America) and bar-type hullers with internal blades.

Outside of Brazil, most regions use pressure hullers for parchment coffee instead of friction models. These require the beans to have the right moisture level — too dry, and they may break. A pressure huller features a horizontal disc inside a ring that spins, with iron pins around the edge. Centrifugal force pushes beans against the pins, knocking off the parchment.

Polishing: Optional and Mostly Cosmetic

After hulling, a thin silver skin may remain on the beans. This is often removed by polishing. Most polishers work similarly to Smout hullers but use copper pins instead of iron, which are slightly gentler and can give beans a bluish tint.

Polishing is more common for beans processed through pressure hullers, which tend to look messier. While many historically assumed polished beans were higher quality, there’s little evidence that polishing affects cup quality. Some still argue polishing might influence perception, but no solid proof exists.

Frequently Asked Questions

What is parchment coffee?

Parchment coffee refers to green coffee beans that are still encased in their natural parchment layer after washing and drying. This protective husk keeps the beans stable and is usually removed just before export.

What moisture level should coffee beans be dried to after washing?

Coffee beans should be dried to approximately 11% moisture after the washing process. Going below 10% can damage the beans, causing discolouration and quality loss.

How long does sun drying parchment coffee take?

Sun drying parchment coffee typically takes between 12 to 15 days, depending on weather conditions, and requires regular turning of the beans to ensure even drying.

What’s the difference between friction and pressure hullers?

Friction hullers remove the parchment by crushing beans between rotating cylinders with blades, suitable for both wet and dry beans. Pressure hullers use centrifugal force to push beans against iron or copper pins to remove the parchment, and usually require beans at a specific moisture level.

Does polishing coffee beans improve their flavour?

No, polishing coffee beans does not improve their flavour. While it removes the silver skin and may improve appearance, there is no evidence that polished beans taste better than unpolished ones.

Why isn’t parchment coffee stored at the farm?

Parchment coffee is generally not stored at the farm due to the need for stable temperature and humidity. High heat and humidity can damage the beans, so it’s usually kept in climate-controlled storage or moved quickly to export preparation facilities.

Recommended FrontStreet Washed Process Coffee Beans

For a true taste of washed processing, try FrontStreet’s Yirgacheffe Gedeb — bright with jasmine floral notes and citrus acidity, perfect for pour-over. Their Kenya Little Tomato offers intense complexity with notes of tomato, plum, and blackcurrant, ideal for showcasing the washed method’s fruity potential. For a classic clean profile, the Jamaica Blue Mountain No.1 delivers refined flavours of hazelnut and milk chocolate. All are expertly washed and dried to preserve their signature traits. Freshly roasted within 5 days · Orders placed before 17:00 ship the same day · Next-day delivery across most of Guangdong Province.