The Many Ways of Processing Coffee

Do you drink coffee?

Do you drink it because you love the taste, or because it fuels your day? Do you drink it to wake up? Maybe you drink it because it’s a moment in your day you can get away and relax.

What if you drank it for other reasons? Are you a person that, like me, delves into as much detail as you possibly can about the origin of the coffee you’re consuming? Do you want to know the process? You could also be that person that wonders what all these hipster Baristas are on about – natural process, typica varietal, sun dried… what does it all mean? Read on and you’ll be stopping people in their tracks with new and factual information about coffee.

There are so many things that we at Seven Miles consider when selecting the coffees you drink on a daily basis, however for you, it might be a bit of a mystery. Let’s break it down, and talk about all things green bean related. In this first blog of many about green beans, I’m going to start explaining some of the factors involved in your daily cup.

All about the ‘green bean’

Pick up one of our Single Origin information cards and you’ll see ‘Process’ followed by ‘Fully Washed’ or ‘Natural’ or something else written on there; these are general descriptions of what process the coffee cherry has been through to be exported to us as seeds, or, as we know them, ‘green beans’. Coffee cherries, when they are picked, have an outer skin just like a cherry. It’s a fleshy part known as ‘mucilage’, a parchment layer that is like a shell, kind of like a thin skin we call ‘silver skin and the seed’, covering the bit we all love – the green bean. Process is the term we use to describe removing those layers prior to export.

Let’s get one simple thing out of the way. The majority of coffee cherries are picked when they are a bright, deep red colour. In some cases, the particular varietal may result in a ripe cherry- looking yellow or orange, and then in some cases, farmers may allow the fruit to darken to a purple (or even darker) to increase sugar content.

There are several different practices to remove the outer skin on the coffee cherry. Let’s take a look at each.

Washing: the most common practice

The most used practice is washing, encompassing around 50% of all coffee produced. Washing means that the fruit is washed from the parchment prior to being dried. To assist the fruit in falling from the parchment, the cherry must be fermented. First, the cherry will go through a de-pulping machine that will remove the outer layer and some of the mucilage. Then, the fruit is placed in fermentation tanks. There are two forms of fermentation; wet fermentation and dry fermentation. A washed coffee often tastes of citrus fruits or pomme fruits, and has clean finishes that can be floral and aromatic, as well as smooth in body. The acidity is usually higher in quality than other processes.

In wet fermentation, the fruit is covered with water and allowed to sit. This process can take between 12-18 hours. The producer will be watching closely for the moment that the fruit starts to fall away from the parchment easily. They will simply rub a handful of the fruit in their hands, and when the fruit falls away, it will make a sound similar to rubbing marbles together.

In dry fermentation, the producer will put the fruit into the fermentation tank, and (you’ve guessed it!) leave it. Now, this is a riskier process, as you can over ferment the coffee much more easily than in wet fermenting. An over fermented coffee can taste like alcohol – and not in a good way. To check the process, the producer will place a stick right through the middle of the bed of coffee beans and remove it. If the hole caves in, it’s not ready. If the hole stays, the beans are ready for the next process. Once fermented, they are washed to remove the fruit. They are then sent to dry – I’ll get to that bit later. Wet fermented coffees are very clean in their flavours, however dry fermented coffees can give a sweeter complexity, with a little more body than their fully washed friends.

Dry processed coffee

The next process is dry processed coffee, a seemingly simpler method. Once the cherries are picked, they are simply laid onto concrete patios or raised beds, usually known as African beds because of the origin from which this style was created. The raised bed is usually a hessian or similar material, elevated to waist height, which allows for air circulation around the cherries. In both of these methods, the producer will need to decide on how quickly the cherries are to be dried. Some variables in this process include letting the cherries sit in thick layers or bags in a warehouse first to warm them up and allow for some fermentation, then spreading them thinly. Some regions simply lay them thinly straight away. There are also varying levels of shade considerations and, in some cases, added air flow from closed side pergolas or even fans. Either way, continual raking is important to even out the drying. Once the fruit is dried and hard, the producer will use a machine that will crack the fruit layer from the parchment.

Naturally dried coffees are usually fuller bodied, with intense dried fruit or sticky fruit flavours, like stone fruits or berries. Due to no water being used, the flavours are often more intense, however in most cases, clarity is lost. The acidity can be varied and sometimes inconsistent, but it can often be amazing and easy to distinguish. Natural coffees also cut through milk more easily.

Semi-washed/pulp natural and honey processes

Now, we’ll cover two processes that are somewhere in the middle of washed and dry processed. These processes are known as semi-washed or pulp natural and honey. Often, these processes get confused for being the same, however there are some key differences. In both methods, the outer layer is removed, and then the seed with the parchment and mucilage is dried. The drying is somewhat more risky due to the fruit being intact. Long drying periods can result in fermentation, so airflow, shade cover and continual raking are important. It is the producer’s choice to start thick, to allow for a little fermentation first, before spreading them thin or going straight to the drying phase. In semi-washed coffee, the process of removing the outer layer is done with a wet pulping technique, where the removal is done with water flow. The fruit is then laid on raised beds and allowed to dry until the fruit is ready to fall off. In a honey process, the dry pulping technique is used, with the outer layer being removed without water, leaving a really sticky fruit (honey). It is then placed on raised beds for drying.

Semi washed and honey coffees have a unique crossover between the clarity and good quality acidity of washed, and some of the intensity, complexity and sweetness of a natural coffee.

The drying of the seed process

Last but certainly not least, there is the ‘drying of the seed’ process. In most cases, these beans are left in the parchment layer for an added layer of protection from the sun, however in some cases the parchment is removed to allow the seeds to dry faster. This is often a financial decision, and certainly not made with quality in mind. Some producers will leave the coffee in parchment to give the seed a protective layer, and will leave it like this right until sorting and shipment. In fact, most drying decisions are made with financial influences. The most common method is concrete patios. These will sometimes be the size of two, three or four football fields, and on any given day you will see workers raking the coffee to continually turn the seeds for even drying. Some regions will use raised beds which helps with drying the fruit evenly, due to the airflow. In some cases, closed pergolas are used, predominantly in countries with less stable weather patterns.

The machine drying process

There are also machine driers, which can be used with varying success. In low quality situations, the coffee is dried with a lot of hot air with no resting periods. This can dry the coffee fast, and when taken to rest, the coffee ends up raising in moisture levels again, usually inconsistently. This technique can damage the cell structure of the seed and end up taking away some of the quality. There are others that try to imitate a day and night of drying. The temperature of the drying is kept a lot lower, and then the seed is allowed to rest, just like it would overnight in an outdoor drying situation. This can aid in letting the seed dry much more evenly, and the resting helps in keeping the cell structure, therefore maintaining the quality of the coffee

All in all; quality over speed!

As a general rule of thumb, fast drying means the green bean will age in storage more quickly, whereas slow drying will allow the coffee a longer ageing period, allowing roasters to store the coffee for longer… but that’s another story!

Paul Asquith
With 15 years already spent committed to coffee, Paul's passion is for digesting the endless possibilities and knowledge surrounding coffee flavour development. After winning the Australasian Grand Barista Championship in 2012, Paul knows just how good coffee can be and the important role everyone plays, from grower to Barista, in developing and nurturing flavour. Captivated by coffee’s agronomy, Paul is excited to be part of a generation passionate about improving practices on farms and seeing growers produce outstanding coffee. Paul holds a pivotal role within our team. Working side by side with our cupping panel, roasters and trainers, Paul’s focus is on refining our coffee program to ensure it honours the remarkable flavour diversity coffee has to offer and supports best practice at each and every stage.