Whilst swotting up on your favourite coffees, you may well have come across the phrases ‘washed’ and ‘unwashed’, and, understandably, you may well want to know exactly what the difference is. Our Single Origin Decaf, for example, is described as ‘fully washed’ - but in an industry of winnowing, pulping and mucilage, what does that actually mean?
First things first - the Coffee Cherry
Before we go on to describe each method, it's probably worth knowing exactly why we need either of them in the first place. In short, both terms describes the process from turning a coffee cherry (pictured) into the beans that you associate with your morning cup of Joe. In fact, the roasted beans that you would be familiar with represent just 15-17% of the original fruit. The cherry is composed of an outer skin, mucilage (the flesh of the coffee fruit), parchment (the hull that envelops the bean) and silver skin (a thin layer of 'chaff' that hugs the bean) - all of which need removing before we can roast and grind the bean itself.
Washed - the 'wet process'
Without looking like we're picking side already, we’ll start with the ‘washed’ method - otherwise known as the 'wet process'. After selection, ripe cherries are put through a ‘pulper’ which peels the pulp away from the bean, leaving the mucilage and parchment intact.
Dropped into large vats, the beans are then left to ferment for 1-2 days, during which an important reaction of yeast and bacteria occurs that breaks down the sugars in the mucilage - producing acids which will later add complexity and depth to the coffee. The coffee is then transferred into a long trough of water, with the denser beans sinking to the bottom and the lighter beans floating on the top - and this is where the process gets its name. The beans that sink go on to raised beds to dry out in the sun, while the lighter beans go through the washing process again.
Following this, the coffee must dry for several days in order to reach an optimal moisture content (around 11%). Finally, when the coffee bean is dry enough and has shrunk in size, the parchment & silver skin can be peeled away, leaving you with a green bean that’s ready for storing before roasting.
Unwashed - the 'natural process'
Known to many as the 'natural process', this method relies solely on heat to separate the bean from the cherry. The coffee fruits are sorted and cleaned via a process known as ‘winnowing' (effectively using a large sieve). Those deemed to have made the cut are then laid out in the sun on brick patios and left to dry - a process that can take anywhere up to four weeks (if space and time are an issue, however, machines can be used to speed the process up). Getting this right is extremely important, as over-dried coffee beans will become brittle and crumble during hulling, whereas an overly moist coffee bean will be prone to fungi and bacterial attack.
Once dried, the cherries are stored in huge silos before being sent to the mill for hulling (a machine-led process that removes all the excess layers of the cherry), sorting and grading.
So which is best?
So why choose one method over the other? Of course, each process boasts its own pros and cons. With washed for example, the actual 'cleaning' of the pod can take just a few hours and is fairly consistent, whereas with unwashed this fermentation can take weeks; but for the farmers themselves, this choice often comes down to resource. Without the need for water and specialised equipment, the unwashed process is much cheaper - but also carries with it a much higher risk of rot and spoilage.
When thinking of taste, the preferred method is usually washed since it gives brighter, clearer and more acidic notes - whereas the unwashed process produces heavier, more complex flavours that are punchier in weight. Either way, taste is entirely subjective and it’s up to you to find out what you prefer – we aren’t here to tell you what to drink (as long as it's CRU Kafe, of course).