The Different Ways of "Processing" Coffee Beans

This guide will detail the different methods of processing coffee beans to give you a good understanding of how coffee beans need to be prepared before they are roasted.

There are three different methods of processing and this page will detail the specifics of each method and leave you with an appreciation of the advantages and disadvantages of each style.

coffee production stages

The coffee fruits are processed to remove the layers of mucilage and pulp from the green seeds.

The seeds are then dried to a specific moisture content, the first stage in turning them into a product suitable for grinding and extraction into a beverage.

coffee bean diagram

The three main methods of processing coffee beans are dry, wet and semi-washed.

Dry processing is the oldest and most traditional method, where the whole fruit is dried before being hulled and sorted.

Wet processing is more popular and involves removing the fruit's skin and mucilage (inner layer) before drying.

The semi-washed method is a newer technique that combines aspects of the dry and wet methods.

The Dry or Natural Coffee Bean Processing Method

raking dry coffee beans

The dry method, also known as the natural method, is a way of processing coffee beans that is frequently used in countries with limited access to water. The coffee beans are dried completely, then roasted.

The dry method is one of the oldest and most traditional ways of processing coffee. It requires little machinery and is a simple process that can even be done at home.

When cleaning the coffee fruits, there are two ways to do it - with pressurized air or water. The unripe fruits float to the top and can easily be skimmed from the batch when cleaned with water.

The fruits are then spread out / exposed on mats and raked throughout the day. That process usually continues for several weeks until the moisture content is sufficiently low.

The dry method of processing Robusta coffee is similar to the process used for Arabica beans grown in Brazil.

The coffee cherries are dried in the sun or in mechanical dryers until they reach a moisture content of about 12%.

Some argue that the dry process results in an inferior bean and/or flavor because it increases the potential for inconsistency vs other methods.

In truth this process can actually produce a more complex bean with a full body. Often it's the case that leaving the fruit on the bean for a longer period of time enhances the taste of the coffee, making it more pronounced as more of the sweetness from the fruit passes through.

The dried beans can then be stored in silos until they are ready for the next stage of processing.

After being given time to mature the dried beans are typically moved to factories where they can be processed by milling machines.

The purpose of this step is to remove the centers of the beans from the fruits, a process typically referred to as hulling.

The Wet (or "Washed") Coffee Bean Processing Method

wet coffee bean processing

The wet method is a processing method used in wealthier coffee-growing areas. It requires a large quantity of water and expensive machinery, so it is not often used.

This method of coffee production is a more complex process that takes longer but results in a higher-quality cup of coffee.

It involves washing the coffee cherries before removing the pulp, and then soaking the beans in water for a period of time. This method is known for reducing the chances of defective beans making it into the final batch.

The coffee fruits are washed and then fed into water channels where the process of flotation separation happens.

Flotation separation basically screens out fruits based on their size and their degree of ripeness.

The fruits then pass in between a hard/fixed vs moving surface and have their pulp removed with a machine that leaves only the actual seeds and remaining mucilage.

The seeds are then passed on to tanks intended for fermentation. They're stored there, usually for at least 12 hours to ferment.

The enzymes present in the coffee fruit start to break down the left over mucilage.

In some cases water may be added at this stage but usually there's enough moisture from the actual mucilage to catalyze and maintain fermentation.

Once all the remaining mucilage has been removed the actual drying process begins.

The coffee beans are exposed and laid out in the sun, usually on drying beds, until all the moisture has been reduced so a low threshold (usually 10%-12%).

At this stage the coffee is technically transformed into what is referred to as "parchment coffee" as a result of a yellow parchment layer that attaches to the seed.

After this, one final process of hulling remains to remove that parchment and all that should remain is the green colored coffee beans within. It's at this stage the coffee is ready to be sold / transported to coffee roasters.

Cafe Imports has produced a good video detailing the washed coffee process here:

The Semi Washed Coffee Bean Processing Method

semi washed coffee beans

The pulped natural method, also referred to as "semi-washed" is a more recent way of processing coffee and is a combination of the major dry and wet methods.

Coffee cherries are harvested and then the fleshy part of the fruit is removed, leaving the coffee bean exposed.

The beans are then dried in the sun, or sometimes in mechanical dryers. This method produces coffee that has a sweeter flavor and more body than coffee processed by the other methods.

This method tends to be used for premium or specialty coffee, and came about as a result of experimentation.

The semi-washed method actually mirrors the regular washed method except that the beans are dried while the mucilage is still attached, which means they bypass any fermentation stage.

Leaving the mucilage layer in tacts means these coffee beans can't be dried mechanically and thus the process of drying them needs to be done with sun-drying.

Sun drying, as with the traditional method, results in more sweetness and less acidity.

All coffees that are dried while a layer of mucilage is retained are formally referred to as "semi-washed". That said, this method of processing can be different depending on the region. For instance, in Indonesia the process of wet hulling is sometimes considered as semi-washed even though it's a very different method than the pulped natural used in Central America.

To elaborate: in wet hulling, the coffee seeds are removed from the seed's mucilage by a machine. The seeds are then dried in the sun or sometimes in a machine.

The process can be different depending on where it is done.

Also interesting to note is that in places like Costa Rica semi-washed coffee is also known as "honeyed coffee" due to the enhanced sweetness of the bean.

The process used there includes drying the beans to a very low 10% - 12% moisture level with the mucilage still intact.

Coffee Bean Processing and Flavor

graphic of coffee production

There are quite a few nuances and minor elements of coffee processing that can be tweaked and lead to major changes in the final product.

For example drying the coffee beans more quickly in a consistent and stable environment will result in a cleaner flavor profile than those that are dried out more slowly.

Slower drying processes will tend to have more complex and fruitier flavor profiles.

The coffee processing method can be one of the single most impactful factors in developing the eventual flavor of the coffee.

Sweetness, fruitiness, and acidity are all flavors that can be affected by the processing of coffee beans. By being aware of how a coffee bean has been processed, you can select a bean that will give you the flavor you are looking for.

Did You Know?

In terms of flavor the washed method tends to produce more vibrant and clean tasting coffee beans and is also the more common method of processing. This is attributed to mainly one thing: consistency and control the style affords.

Natural processing tends to be less consistent (which means there will be more “impurities”) but has the advantage of producing a more fruity and earthy flavor.

FAQ

What is the best coffee processing method?

This is debateable but washed coffees are often considered superior because they consistently score very well in terms of quality and have fewer impurities.

 

What's the difference between washed and natural coffee?

A “washed” coffee bean will have the fruit stripped off before leaving the coffee bean dry on its own. A “natural” processed coffee will leave the coffee cherry on the fruit and it will dry while completely in tact. The seeds are removed from the cherry once they have both dried.

 

What does wet hulled coffee mean?

Wet Hulled is synonymous with “semi washed”, where the beans are left out to dry in the sun but still have their mucilage in tact.