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What Is Coffee Processing?

Updated: Jan 19

So many factors influence the flavour in a cup of coffee. But one area that may be confusing is the terminology surrounding processing, and what flavours and characteristics that typically gives. Every step from the genetic variety of coffee, terroir in which grown, ripeness when picked, storage conditions etc, are all crucial, but one area to better define is processing. After trying a variety of coffee's, you may be able to spot naturals from your fully washed coffees!

All Images in this blog, credit to Omwani, our partners and suppliers of Uganda African Moon coffee.


1. Washed Coffees

Once coffee cherries are picked from coffee trees, they can go through a variety of processing methods. The washed process means coffee cherries are stripped of their outer fruit with a depulper, placed in a trough of water where fermentation removes any outstanding flesh, washed again to clean off any debris, and layed out to dry on patios or drying tables.

Washed coffees tend to be more common in specialty coffee, given they focuses solely on the flavour characeristics of the seed. It's far less about imparting flavour onto the bean, and more about revealing every unique flavour the seed itself can bring. This hinges on the seed developing a profile of natural sugars and nutrients. In this sense, it's far more important to focus on factors like genetic varieties of seed, terroir in which coffee tree is grown, and high altitude.

For example the prized coffee variety Geisha, contains highly desirable tasting notes like floral roses, sweet cream butter, green apple, tropical fruit, kiwi, lemon tea and green grapes. Almost always this variety is fully washed to bring out these tasting notes, and mitigate any flavour interference which other processing methods may apply.


2. Natural/Dry Processed Coffee

The natural process, also known as the dry process, is the oldest coffee processing method. This involves coffee cherries, fully intact with the flesh around the seed, being thinly spread to dry on patios or drying beds. Regular turning of the coffee is required to avoid mould and unpleasant fermented tastes from developing.

Natural processing is the most popular coffee processing method and used for almost all low quality coffees in the commodity market, and rarely for specialty coffees, although this is changing. Natural processing tends to be the lowest cost option for coffee farmers, given limited water access in places like Timor-Leste and Ethiopia, however this process can become expensive for specialty coffee given the extra care and attention to achieve consistent batches.

In recent years naturally processed specialty coffees have received renewed interest for their unique flavour characteristics. If done right, naturals tend to have fruit flavours reminiscent of blueberry, strawberry and exotic fruits. Additionally naturals usually have a full body which gives a heavy thicker mouthfeel.


3. Honey/Pulped Natural Coffee

In the pulped/natural process, coffees are mechanically depulped stripping off most of the fruit flesh, and laid out to dry on patios or drying beds. This process sits somewhere in between the natural and washed process with regards to how much fruit flesh remains on the seed. The desired qualities of pulped naturals are the sweetness the small amount of fruit flesh puts into the seed.

A variation of the pulped natural process, the honey process, is the same except it refers to the extent of how much fruit flesh remains on the seeds. Despite the name, the honey process doesn't involve using honey or bees. The word honey is used because its translates from the spanish word miel. Hence miel or honey processing comes from Spanish speaking Central American countries like El Salvador and Costa Rica.

With regards to the different levels of honey process:

0-20% of mucilage remaining is white honey process

25-50% least amount of mucilage is yellow honey process

Around 50% mucilage remaining is red honey process

90% or more of the mucilage remaining is black honey process


4. New Processing Methods

A new process which has taken the specialty coffee market by storm is aenerobic fermentation. This method involves fermenting coffee cherries in an oxygen free environment, fostering microbes which break down certain carbohydrates likes sugars into acids and/or alcohols. Typically this is done in a sealed tank injected with carbon dioxide to remove all oxygen, or simply having a valve on top of the tank so as fermentation takes place, carbon dioxide pushes oxygen up and out of the tank. The 2nd method is techinally known as semi-carbonic.

Aenorobic fermentation is very difficult from the start, not only from a cost perspective, but finding a consistent recipe that works whilst controlling for factors like ph, temperature, time, varietal of coffee. The rewards however yield some remarkable flavour profiles. There are certain notes in coffees that are delicious by themselves, for examples the varietal SL-28 is renowned for its distint fruit flavours. Aenorobic can actually enhance and boost those flavour notes. These coffees certainly aren't cheap, but they demonstrate exciting new flavours on the horizon, and incentivise farmers with better pay, and resources to experiment with new methods.

A hallmark of great coffee is transparency in the processing method used, so next time you see words like 'natural' and 'fully washed' you'll better be able to spot what coffees suit your preferences!


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