A Guide to Coffee Processing Methods

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Have you ever wondered what the difference is between the different coffee processing methods?

Which method is better, and how exactly are they different from one another?

In this article, we will walk you through the main methods of coffee processing so you can better understand how each influences the flavour of the coffee and so you can make an educated decision when you next buy beans.

What is coffee processing?

A coffee cherry is like any other pit fruit in that it has a seed, pulp, mucilage surrounding the seed, and skin. To process coffee, we must separate its fruit flesh and skin from the seeds (the coffee beans).

Coffee processing can have a significant influence on a coffee’s quality, and the specialty coffee world is placing more and more emphasis on understanding how different processing techniques affect flavour and quality.

In addition to the impact of the quality of the beans, the processing method can also significantly influence the coffee farmer’s profitability, as some methods take significantly longer, are more labour intensive, or require special equipment.

Coffee cherries

For the most part, the world’s coffee cherries are processed in one of two ways: the dry process or the wet process.

Coffee that is processed by the dry method undergoes a longer period of fermentation by being laid out under the sun for several days to several weeks.

Coffee that is processed by the wet method has its skin and pulp removed mechanically before being fermented for 12–36 hours.

Some specialty coffees are processed by other methods, such as honey processing or wet-hulled processing, but these methods represent a small percentage of coffee’s overall production.

Natural Processing Method

Natural, or dry processing is the oldest method of processing, originating in Ethiopia. To dry process coffee, farmers pick the cherry and lay it out on raised beds or patios to dry in the sun.

They turn it periodically to ensure even drying and prevent mould or other issues that would degrade the quality of the coffee. The coffee cherries must be protected from rain or dew at night.

The dry processing method is preferred in areas where access to water is a challenge. This includes regions of Brazil, Yemen, and Ethiopia.

They will remain on these patios until the moisture content drops below 10%, after which they will be moved to “storage” areas (usually concrete warehouses).

The dried cherry is then milled to remove the dried fruit layer from the seed.

This usually happens at a central milling facility in order to keep costs down (smaller operations are less efficient than larger ones), but some farmers mill their own coffee.

The beans are then transported either by truck, boat, or train to where they will be exported from.

Dry processes typically take longer than wet processes, but produce a deeper flavour profile as sugars in the fruit have more time to caramelize.

Pros:

  • Low cost
  • Less equipment required
  • Good for dry areas with poor access to water
  • Can produce very flavourful coffee, often with fruity notes

Cons:

  • Requires suitable weather conditions
  • Can lead to inconsistencies, making them hard to replicate
  • Sometimes contain unpleasant fermented flavours

Washed Processing Method

Washed processing separates the bean from the pulp while they are still wet.

In the washed process, all of the fruit flesh is mechanically removed from the coffee beans, and this is accomplished with a machine called a depulper.

Once the outer flesh is removed, the cherries are placed in water tanks. The coffee beans are fermented in these tanks to remove the mucilage, which is the sticky pulp-like substance that remains on the bean after pulping.

The fermentation process typically lasts between 12-48 hours at which point most of the mucilage will have been broken down by natural enzymes and can be washed away.

After fermentation, the coffee cherries then go through a second round of washing in channels or clean tanks.

Once clean, the beans are then spread out to dry. During the drying phase it’s important to regularly stir and turn the beans in order to ensure even drying, which can take up to 4 weeks.

Alternatively, the coffee beans can be dried in mechanical dryers to reduce the moisture content to 11%.

Coffee cherries drying

Once they’re dried, they’re bagged up and stored before being shipped off to be roasted and brewed around the world.

The wet-processed coffees usually have cleaner tastes with more acidity than dried-processed coffees. The flavour that is derived from washed process beans requires the beans to absorb enough nutrients, as no flavour is extracted from the surrounding pulp.

Pros:

  • More consistent and reliable process
  • More pure flavour profile – highlights the notes characteristic of each variety of bean
  • Can highlight the bright or acidic flavours of the bean

Cons:

  • Requires special equipment e.g. a depulper
  • Requires much more water

Honey Processed Coffee

A process known as the honey process, or the pulped natural process, is widely used in Central American countries including El Salvador and Costa Rica (where it originated).

The name “honey processed” is a bit misleading. It sounds like the coffee has been made with honey or tastes like it, but neither is the case.

The “honey processed” process refers to the wet-milling of coffee beans before they are dried using a specific method. It gets its name because of the sticky, honey-like coating on the beans before they’re dried.

Honey processing is like a hybrid between wet and natural processing. In honey processing, the coffee cherries are depulped, but the mucilage layer is left.

The coffee is then dried with some or all of the sticky mucilage still attached to the bean.

In general, the more mucilage removed during drying, the cleaner, fruitier and more acidic the coffee will be. The less mucilage removed during drying, the heavier bodied and sweeter the coffee will be.

Honey processing can be used to varying degrees.

The amount of mucilage that gets removed before drying determines what kind of honey processing will be utilized:

Light Honey Processing: The least amount of mucilage is removed before drying. The resulting coffee’s flavour profiles are closer to natural processed coffees.

Yellow Honey Processing: More mucilage is removed than in light honey, but less than in red honey. It also results in a more complex cup than light honey, but with less brightness than red honey.

Red Honey Processing: Nearly all of the mucilage is removed from the beans. The resulting cup has higher acidity and more complex flavours than honey coffees that have less mucilage removed

The first step in honey processing is to remove the skins from the coffee cherry. This can be done in a few different ways:

  • Mechanically (with a depulper)
  • Manually with water (floating method)
  • Manually without water (dry fermentation method)

There are many different ways to process coffee. It isn’t a one-size-fits-all kind of situation. There is no right or wrong way to do it either. Each way has its advantages and disadvantages and many factors that can influence the final product.

Honey processed coffees tend to take on the best of both worlds by being both crisp and acidic but also very sweet.

Wet-Hulled Process

The wet-hulled process is also known as semi-washed.

With this method, the cherries are de-pulped, but rather than moving them straight to drying beds or patios, they are stored in plastic tanks.

While in the tanks, the mucilage breaks down and ferments a little bit before the beans are washed off. At this point, the coffee beans are still around 65% moisture content.

This method is used primarily in Indonesia, where water is scarce. It allows farmers to skip the patio-drying stage and get the coffee dried more quickly before the monsoons hit and ruin their crop.

The beans are then transferred to drying beds or patios where they dry rapidly because of their high moisture content. The very high moisture content of these beans during drying means that they do not form a hard bean shell.

While drying, the beans have their parchment removed by hand but still have their thin silver skin attached.

After a certain period of time (depending on the climate), the beans are moved to a machine that peels off the dried skin and mucilage.

If you’ve heard Sumatran coffees described as “earthy,” “dirty” or “muddy,” it’s probably because of this processing technique.

Wet-hulled coffees can have some funky flavours and aromas, but many of my customers actually like that dirty funk. You can find it in almost all Sumatran coffees if you’re looking for it.