Washed vs Natural Processing
by Paul Asquith·
Before we delve into the world of processing, let’s talk briefly about the anatomy of coffee. If you’re unaware, coffee doesn’t just land on the doorstep as a green or roasted ‘bean’. It is actually a seed of a cherry like fruit; most, when ripe, are bright red in colour. Behind its first layer, which is like the skin of a cherry, is a sticky layer called mucilage or pulp. Under the mucilage is a starchy pectin layer and under that, a hard layer called parchment or husk. The seed is within that, wrapped in a thin layer called silver skin.
‘Processing’ is the removal of outer layers to relieve the seed, commonly called the bean, for us to roast. The more that specialty coffee progresses, the more nuanced our understanding of these methods has become; this has led to a rise in complexity within processing systems. A solid understanding of traditional processing methods will enable us to understand variations of process; this blog describes those.
Washed Process Coffee
Washed process is the most common process in the world, making up around 50% of the coffee produced. Fundamentally, the term ‘washed process’ means that water is used to remove the fruit from the seed prior to the coffee being dried. There are many different techniques for washed processing, we’ll describe two.
In all washed processed coffees, the cherry needs to go through a depulper. This is a machine with sharp blades on a wheel that tear the outer layer and some of the fruit away from the seeds. This leaves some fruit attached to the husk. If the producer was to try to remove all the fruit in this process, the seed would be damaged. Once the fruit is removed, the seeds are sent to tanks for fermentation.
There are two types of fermentation used for washed coffee; wet fermentation and dry fermentation. The most common type of fermentation is wet fermentation. The seeds are covered in water and the fruit is allowed to ferment. This fermentation causes the fruit to fall away from the husk layer; usually taking 12-18 hours. Once ready, the seeds are sent down channels where agitation aids in removing the fruit. This type of washed coffee usually possesses clean attributes. Bright flavours like pomme fruits or citrus fruits, floral aromatics and clean, light bodies.
A slightly more complex version of the washed process coffee is dry fermentation. In this case, from the depulper, the coffee is sent to a fermentation tank but water isn’t added. The fruit is allowed to ferment for a period of 12-24 hours. Once the fruit is ready to be washed off, the seeds are added to water and agitation is used to remove the pulp. These coffees will likely possess more sweetness and body than their wet ferment counterparts.
Natural Processed Coffee
The oldest technique in coffee processing is the natural process and, in part due to that, it requires less infrastructure. Natural, or dry processed coffee is simple in that the cherry, in its entirety, is to a point where the outer layers can easily be cracked off the seed, removing the fruit and the husk easily. Natural processing relies on predictable weather conditions since the producer must use the sun to prepare the outer layers to be removed from the husk. It also carries risk as the fruit goes through changes in moisture content.
From picking, the cherries are usually floated in water to sort ripe, unripe, over-ripe and problem cherries before being sent to dry. The cherries are sent to large concrete areas or raised beds with cloth that aid airflow. Either location, the cherries will need to be turned frequently to aid even drying. During the early stages of the drying, the fruit will ferment and add to the boozy flavour natural coffee is popular for. During later stages as the fruit's moisture level drops, the extended contact time with the seed allows for higher levels of sweetness in the cup. Natural coffees usually end up with high levels of sweetness, fuller bodies and depending on the treatment of the cherries, can have boozy characteristics.
We hope that this introduction to coffee processing was both informative and clear. We, as Josie Coffee, buy a wide range of coffee processes; we wanted to convey the depth of possibilities to our customers and make the descriptions included with our coffees somewhat more tangible to those drinking them. In future posts we will cover the many spin offs of these basic techniques and aim to show the range of controls that producers have over the cup of coffee we eventually drink.