A large percentage of the world’s coffee is harvested using this method as it is quick and does not require the use of machines. Strip picking means the picker will strip the entire branch, rather than selecting the fruit which has reached full maturity. Whilst this method is certainly efficient, unfortunately it results in a mixture of ripe and unripe cherry which can be detrimental to cup quality unless it is sorted in the processing.
Most specialty coffees will have been hand-picked by either a team of pickers (on an estate) or by the farmers themselves (smallholder/cooperatives). For the coffee to be complex in the cup, it is essential that the cherries have reached maturity when they are picked. Pickers using this method should therefore only be selecting the ripe cherries, leaving any immature fruit on the tree to be harvested during another pass of the farm. Depending on the farm size, there can be up to ten passes to ensure the cherries are picked at the right time. Most pickers are paid by the weight of cherry that they deliver so most farmers have a hard time incentivizing their pickers to selectively harvest the crop, many will pay a premium for good quality ripe cherry.
The only Arabica producing country to use this method of harvesting is Brazil and that is due to the relatively flat lay of the land which allows a machine to navigate the perfectly formed rows of coffee quite easily. This method is extremely efficient and whilst the equipment is expensive, the overall labour cost of the farm is much cheaper as it only requires one person to operate the machine. This is part of the reason why Brazilian coffee can be cheaper as the costs involved in production are lower due to this reduced overhead.
A machine picker employs a similar method to strip picking whereby the entire branch is almost swallowed by the machine to absorb all of the cherries growing on it. Unless followed with rigorous post-harvest sorting, this has a detrimental effect on quality for two reasons: one being the resulting mixture of unripe and ripe cherries which will impact cup quality. The other being the numerous twigs and foreign objects that can end up in the same lot. This method is also rather unkind to the trees, though some farms have started to use gentler equipment similar to that which is used on olive plantations.
The Honey Process
This process can cause some confusion amongst roasters and consumers due to the many different forms that it can take depending on the country of origin. It is therefore a ‘hybrid’ process that is very much open to interpretation depending on the aim of the farmer.
In Brazil for example, research was carried out to try and find a processing method that would use less water than the washed process, but that would be less susceptible to defects than the natural process. The ‘Pulped Natural’ process therefore came about whereby cherries are depulped to remove the skin and much of the mucilage from the cherry, but rather than being washed to totally rid the bean of any mucilage, they are immediately dried on patios. This results in a coffee that has much of the sweetness and body expected from a natural processed bean, but there is also a rounded acidity in there too which contributes towards better clarity in the cup.
Central American countries such as El Salvador and Costa Rica have more of a focus on experimentation and therefore revert to the true ‘Honey’ process whereby ripe cherries are depulped in a controlled manner to determine exactly how much mucilage is left on the bean. It is in this way that different flavour profiles can be created due to the varying influence of fermentation. In this instance, the drying process is extremely important as there is more of a risk of mould growth and defects, so it is essential that the sticky beans are turned regularly and are protected from insect damage. You may come across terms such as ‘yellow honey process’ or ‘perla negra’ which refers to either the amount of time the bean spent in the cherry before it was depulped, or to the amount of mucilage that was left on the bean before it was dried.
The Natural Process
This is arguably the oldest and most original form of coffee processing, and was traditionally used to process cherries on a commercial scale due to the low costs involved (i.e in Brazil) or in areas with limited access to water resources (i.e Ethiopia).
After harvesting, the cherries are laid out to dry in the sun. On a commercial scale, they are usually laid on large concrete or brick patios though they are sometimes left directly on the earth to reduce the moisture content. It is for this reason that natural processed coffees will often throw up more defects in the cup. They can sometimes have an intense earthy flavour due to the soil they have been dried on! Traditionally, it has been washed coffees that have attracted higher prices due to their cleanliness and uniformity, though more specialty buyers have invested in the natural process due to the potential for flavour profile experimentation.
In some cases, we are seeing more experimentation during the fermentation of natural coffee. One form of this is with anaerobic fermentation of coffee cherries prior to drying. This process is carried out by storing coffee in a sealed container without the presence of oxygen. This causes the microorganisms responsible for fermenting the coffee to produce different acids and flavour compounds, which generates a distinct flavour profile.
If done properly whereby ripe cherries are laid on raised beds in thin layers and regularly turned to reduce the risk of mould growth, natural processed coffees can have the most incredible cup profile with flavours such as ripe strawberry, mango and blueberry being commonplace. The cherry is dried with all of the layers intact which means there is a certain amount of natural fermentation occurring in the bean in its own environment. Many enzymatic bi-products are absorbed from the mucilage into the heart of the coffee bean which can result in an incredibly distinct flavour profile. Once dry, the cherries will resemble raisins and when they have reached this state, the coffee is hulled to remove the outer layers before being sorted in a ‘dry mill’ for shipment.
Semi Washed / Wet Hulled Process
This process is most commonly associated with producing countries in Indonesia. It is known locally as ‘Giling Basah’ which, when translated, means ‘wet grinding’. In this process the coffee is picked, depulped (usually on the individual small holding) and then partly sun dried until the moisture content of the beans reaches 30-35 per cent. Unusually, the parchment beans are then hulled at this stage to tear off the outer layer protecting the inner bean revealing a whitish coloured, swollen green bean. The drying is then completed on the patio until the moisture content reduces to a level where mould formation is not a risk. After this is complete, the beans turn to a dark green/blue colour which is very distinctive and makes Indonesian beans processed in this way instantly recognisable.
However, this process does not come without its problems. Due to the fact that the protective layer is removed at an earlier state, the beans are left exposed to the elements (and insects) during a really important stage in the process. Indonesian beans (and particularly Sumatran beans) are often associated with woody, earthy or spicy flavours which are thought to be a result of this unique process. Some buyers prize these characteristics whereas others will view them as defects in the cup. When we look for a great Sumatran, we want plenty of body with heavy chocolate flavour, and a touch of tangerine funk. They can make excellent blend components adding real depth and weight to your coffee.
The Washed Process
The washed process is widely used across Latin America and parts of East Africa. It requires both the cherry and mucilage surrounding the parchment to be removed with the use of friction, fermentation and water.
Once the ripe cherries have been picked, they are delivered to a wet mill where they are loaded into a depulping machine which forces the beans out of the cherry. At this stage, the beans are contained within the pulp of the cherry, also known as the mucilage. This sticky mucilage is composed of natural sugars and alcohols, contributing massively to the sweetness, acidity and overall flavour profile of the coffee.
Once the beans have been pulped, they are put into fermentation tanks for around 12-24 hours dependent on temperature. Although farmers are now experimenting with fermentation time to develop different flavour profiles. For example, a longer fermentation means the beans have more time to absorb some of the sugars and can result in a slightly sweeter, ‘funkier’ flavour, though this can be a hard balance to strike as leave it too long and the beans become over-fermented with unpleasant vinegar-like characteristics.
Fermentation results in the mucilage being broken down, leaving the beans in their parchment which are then ready to be washed. This can either happen in tanks of clean water or, in East Africa, it is often done in channels. Once the beans have been washed they will feel gritty in your hands which means they are now ready to be dried.
At this stage, the parchment beans are taken to drying tables (raised African beds) or to patios to sit for a period of around 10-22 days where they are gently turned. It is widely accepted that a slower drying time contributes to greater balance and complexity in the cup. Some washed coffees, particularly in Central America, are dried in large ‘guardiolas’ which are mechanical dryers often used if a farm or dry mill has a lack of space. In this instance, the coffee is dried in around 3 days and we have found from experience that this can sometimes reduce the shelf life of the green coffee, allowing aged characteristics to creep in at an earlier stage.
The washed process is arguably our favourite at North Star due to the incredibly bright and clean coffees that it can produce. Washed Ethiopian and Kenyan coffees are fantastic examples of the clarity of flavour that can be coaxed out if the coffee is processed correctly.