The way that coffee cherries are processed has a significant impact on the resulting flavour of the beans. Interestingly, most farmers are not motivated by this factor (though artisan producers who recognise this and the value it can bring, are on the increase). Their choice of processing is usually dictated by the availability of water and tradition.
Natural Processing
The oldest form of coffee processing is known as the ‘natural process’. Beans produced by this method of preservation are usually simply known as ‘naturals’. Historically in Ethiopia, the home of coffee, all crops would have been produced using the natural process. In the Yemen, they still only use this process. So, what is it?
Natural processing is named as such since it is considered a natural technique for bean removal. The ripe cherries are simply picked and then laid out on large patios or raised beds (long, drying tables) and left to dry under sunny, tropical skies. Workers must regularly turn the coffee with rakes or their hands in order for it to dry evenly and to avoid humid areas where mould could grow. The process takes around two weeks depending on air temperature and humidity, and the cherries must be protected by waterproof covers when it rains. At the start of the process, the cherries are bright red, but by the end, they’re usually black and appear gnarled and wrinkled – not unlike the way grapes become raisins.
During the drying period, experienced coffee workers constantly pick out any defective cherries that they see – those that are insect damaged, mouldy or unripe – since they can greatly impact the quality of the flavour and consequently the value of the harvest.
Once the coffee cherries are dried to a moisture content of 10 to 12 percent, they are gathered and held in storage until they are ready to be shipped. During this period the moisture content becomes even throughout the batch and the flavour improves and stabilises. Finally, the wizened cherries are milled to crack away the dried skins and the inner layer known as parchment to reveal the beans. At this stage the beans smell wonderful, in a way that is unique to naturals; fruity, boozy, rich and sweet – similar to Christmas cake mixture. Naturals can be quite divisive, with some coffee fans adoring their big, bold and upfront flavours, while others may find them too challenging. They are functional coffees especially in some espresso blends since they add a lot of body and sweetness and have flavours strong enough to kick through the milk of cappuccinos, lattes and flat whites. We’ve always used a natural Brazilian coffee as the base of our espresso blends to add body and richness.
Sound good? Check out our natural coffees here.
Washed Process
Washed coffees are often considered more refined in the cup, with greater clarity than naturals. They usually have less body but a more intense acidity. We’re a huge fan of washed Kenyan coffees – the best ones can be buttery and bright at the same time (think lemon curd)! In this case, the freshly picked cherries are initially placed into water channels where the high-quality ripe cherries sink and the lower quality, unripe cherries float. This initial process allows for effective quality sorting by density so that the good quality cherries can be processed separately.
The sorted cherries are fed into a machine known as a depulper where, most commonly, they pass through spinning barbed wheels which tear away the skins and some of the pulp. Most of the pulp, however, clings stubbornly to the beans. As such, the next stage of the process takes places in large concrete tanks, where the freshly pulped but mucilage coated beans are left to ferment for a period of around 24 hours (depending on temperature and humidity). The process of fermentation allows the coffee’s natural enzymes and yeasts to break down the mucilage so that it can easily be washed off the beans. Careful management of this process is necessary to ensure the beans don’t over ferment and turn sour and unpleasant.
The subsequent washing of the beans takes place in channels that run from the fermentation tanks. The coffee is conveyed into these channels using water and gravity. Once in the channels, wet-mill workers agitate the beans with large wooden rakes which helps to remove the loose mucilage. Of course, at this point, the beans are soaking wet so next, they must be dried. This takes place on either large patios or, for the best quality coffees, on raised beds. The latter allows for better circulation around the beans though in both cases, the coffee is regularly turned by hand or with wooden rakes to ensure good, even drying. This can take up to 15 days and when it rains, tarpaulins must be quickly placed over the coffee to stop potential spoilage from mould and mildew.
During the wet process, the beans remain covered by one of their protective layers – the parchment. After drying is complete, and the moisture level of around 10 to 12% has been achieved, the coffee goes into storage to ensure evenness of moisture and flavour is achieved. At the point of shipping, the coffee is milled to remove the parchment and at this stage quality can be further improved with the removal of imperfections such as chipped, black and insect damaged beans. It is then packed into jute or hessian sacks.
See our range of washed coffees here.
Honey Process
Most of the world’s coffee is produced by either the natural or washed process but there are a few other methods of preparation, including the honey process. Simply put, this can be thought of as somewhere in-between washed and natural since it has elements of both processes. Freshly picked coffee cherries are pulped at a wet mill but then by-pass the fermentation process and are placed on raised beds with most of the mucilage still coating the parchment and beans. Sun-drying takes place on the raised beds over the usual 12 to 15 day period resulting in beans that taste somewhere between those produced by the natural and a washed processes – so, a little fruity, light nuances of tropical fruits and the sweetness of honey – hence the name of this process. There are variations within this method such as allowing some fermentation to take place while the cherries are whole or shrouding the pulped coffee under cloth to generate excessive heat. Look out for names such as red, yellow, orange or even black honey processed coffee – the cherries darken the longer they are left to ferment.
In Indonesia, many farmers employ a different version of the honey process called Giling Basah: they remove the parchment (a process known as hulling) while the beans are still wet. This results in a uniquely chocolatey and slightly earthy flavour that provides loads of body and richness to espresso blends. It plays a key role in our Granary blend.
"New World" Processes
Nowadays, in a world of ever more demanding coffee aficionados, new processes are emerging, such as carbonic maceration, which takes its inspiration from wine producers in Beaujolais. The coffee is processed in tanks in the absence of oxygen which impacts the type of fermentation that occurs and results in different flavours. We’re fascinated by these new techniques and were lucky enough to see them in practice when we visited El Cipres in El Salvador earlier last year. That particular coffee has a great body, with dried fruit notes and a little hint of cinnamon. Elsewhere, other experiments are being conducted such as increasing fermentation times in the whole cherry before pulping, or even fermenting coffee in whiskey barrels.
A Word on Cascara
We began by talking about how the fruit of a coffee cherry is almost always discarded, but this by-product is being given a new lease of life, especially in speciality coffee circles. To produce cascara (which translates from Spanish as ‘husk’), the flesh of the cherry is dried out and can be brewed like a tea, expressing origin characteristics of its own. We’ve played with some cascara recipes recently, and it’s gone down a storm! It can be combined with a sugar syrup to make a great refreshing drink when topped up with sparkling water. Taste-wise, expect peach notes, and a huge wine gum-like sweetness.
The variations in processing techniques are part and parcel of what we love about coffee. The possibilities are endless. Even before processing begins, we know there are masses of different coffees varieties, grown on different terrains and terroirs, at varying altitudes around the tropical world. Variations in processing simply add greater variation in flavours – and that’s before we start to roast or blend the coffee, where we encounter a whole new spectrum of possibilities. It can be a hugely creative process – next time, we will delve into the world of roasting coffee.