Coffee Processing

Coffee beans grow inside the red cherries of the coffee tree. The green beans must be separated from the flesh of the cherry before being carefully dried and packed for shipping. The means of removing the fruit and preparing the beans for market is called ‘Processing’ and can be done in a variety of ways, all of which impact the end result to varying degrees.

As coffee consumption shows no sign of slowing down, more research is being done looking at different ways of processing. Experimentation continues with methods inspired by wine production, for example, looking for processing that elevates the natural flavours in coffee but also safeguards producers from issues such as mould, the need for costly equipment and reliance on very specific weather conditions. Trying different processing methods and new varietals of coffee can be risky for producers if they're not sure the end product will sell. Strong, sustained relationships with importers and, by extension, roasters, mean growers have the time and space to r&d new coffees. The choices roasters make on who to work with when sourcing green coffees has a very real impact on the speciality coffee farming industry, particularly as many growers and washing stations don't have huge farms or lots of money at their disposal when trying new processing methods out.

In speciality coffee the entire process, from picking to packing, is labour intensive, requires skilled workers and, at many points, is done by hand. We buy coffee from small-holders, family farms and cooperatives - small businesses like ourselves, working to support their families and positively impact their communities.

Let's take Rwamawantu, a family farm in Rwanda as an example. They produce half the coffee they process and sell. The rest is grown by neighbouring small-holders who bring their cherry to be processed at the Rwamawantu washing station. What happens next:

Stage 1 - coffee cherries are separated by variety, if needed.

Stage 2 - All coffee cherries are floated after collection. They are submerged in water so that any defective cherries, which float, can be removed.

Stage 3 - Processing begins. This could be the fruit immersed in running water or laid out in the sun for a long period of ferment. There are many methods of processing, the two main ones are detailed below.

Stage 4 - Drying. Once the beans have been separated from the fruit they must be dried to between 10 and 12% moisture. Too dry and they're unusable from a roasters point of view. Too moist and rot may set in during transport.

Stage 5 - Beans are packed in grain-pro bags and hessian sacks for sale and transport all over the world.

Processing

There are two main processing methods, detailed below. They have some features in common such as a carefully monitored period of fermentation and removal of the fruit and other layers around the bean, however the outcome is quite different. As a coffee drinker, you might find you prefer one style of processing over another. Washed process tends to give us a clean taste with as little added flavour as possible. Natural processing includes a much longer period of fermentation and adds a layer of funkiness to the natural flavour of the bean.

Every stage of coffee processing requires knowledge and skill. Entire crops can be lost if rot isn't spotted early enough or drying coffee is left out in inclement weather. It is a hugely labour intensive endeavour.

Washed

Coffee cherries are submerged in moving water to loosen and remove the fruit from the bean.

Beans are then put through a pulper and screening machine to remove more of the remaining flesh. This may be a hand-cranked machine or have a motor attached.

At this stage, the coffee enters a short period of fermentation. Any remaining pulp and pectin will ferment while the bean is protected by a papery layer called parchment. The fermented elements will then be washed away in running water.

The beans will be dried then put through a hulling machine to remove the parchment before being sorted by size then packed for transport.

Natural

Coffee cherries are laid out in the sun to ferment and dry on the bean. The fermentation period can be many days long and must be carefully observed. The cherries are turned throughout the process to ensure even drying and so any rotting fruit can be found and removed as quickly as possible.

After the desired fermentation period the cherries are put through a hulling machine to remove the dried fruit and other layers.

As above the beans are checked for the correct level of moisture then sorted by size and packed for transport.

Other processing methods

There are many processing methods which are mainly variations on washed or natural processes. You'll see things like 'Black Honey', 'Anaerobic Natural', 'Carbonic Natural' and more on coffee bags. These represent years of research and development in coffee processing, often informed by wine making and designed to both increase depth of flavour and other sensory experiences but also to offer producers different ways to process their coffees and offer a wider range to their customers.

Decafination

There's no escaping that the decafination process is both destructive to the natural product and not very sustainable. Again, there is on-going research into the best ways to decafinate that are less harmful to the environment and better preserve the taste of the coffee. The decaf we buy is one of the best we've come across. It is decafinated by Ethyl Acetate (EA) which is a by-product of both coffee and sugar-cane production. The washed-processed beans are submerged in an EA solution, the caffeine in the bean binds to the EA and is then washed away with the waste solution. It is also decafinated in Colombia, where it's grown, rather than sent to a different country for decafination before sale. A couple of issues with any decafination process are the amount of water required and how waste water is dealt with. This is an area of on-going research and development and we're keeping an eye out for other decafs to try.