Coffee processing is both a science and an art. It requires attention to detail and precision but also finesse and love.
How coffee is processed after harvest can have a dramatic effect on the resulting cup, so it has become an increasingly important part of how it is described and sold. The top coffee producers have flavour in mind when they choose their processing methods, but for most producers, the goal is to ensure the processing causes the least possible incidence of 'defect' and therefore no drop in the quality or the monetary value of the coffee.
After harvesting, the key steps to coffee processing are as follows:
After harvest, the coffee cherries are taken to a mill to separate the beans from the flesh and dry the beans so they are safe for storage. Coffee beans start with a moisture content of around 60% and should be dried to around 11-12% to ensure they do not rot while waiting to be sold and shipped. A mill can be anything from a small collection of equipment on an individual farm to a very large industrialized facility for processing enormous amounts of coffee.
There is no doubt that processing can have a massive impact on the cup quality of the coffee, and there is a growing trend for skilled producers to manipulate the process in order to yield specific qualities in the cup.
However, these producers are very rare on the global production scale.
The goal of processing for most is to make the coffee as profitable as possible and this is taken into account when a producer chooses which processing method to use. Some processes require more time, investment or natural resources than others, and so it is an important decision for any coffee producer.
The natural process
Also known as the dry process, this is the oldest method of processing coffee. After harvest, the coffee cherries are spread out in a thin layer to dry in the sun. Some producers spread them out on brick patios, others use special raised drying tables, which allow a better airflow around the cherry, resulting in a more even drying. The cherries must be turned regularly to avoid mould, fermentation or rotting taking place. Once the coffee is properly dry, the outer husk of skin and dried fruit are removed mechanically, and the raw coffee is then stored before export.
The natural process itself adds certain flavours to the coffee, sometimes positive but often quite unpleasant.
However, if there is no access to water this may be the only process open to the producer and is therefore common in places like Ethiopia, and also parts of Brazil.
Worldwide, the dry method is generally deemed only suitable for very low quality or unripe coffee, and the bulk of coffee produced this way is processed as cheaply as possible as it usually ends up in the domestic market and has very little value.
It seems counterintuitive that a producer would invest in the drying tables necessary for the return on offer. However, there are those who choose this method to process high - quality coffee, and they often find the process to be more expensive due to the additional labour involved in the attentive, careful drying of the cherries.
This process remains quite traditional in places, and there is certainly demand for the cup qualities that a carefully processed lot can have. The process will often add fruit flavours to the coffee, regardless of variety and terroir. These are usually described as hints of blueberry, strawberry or tropical fruit, but sometimes with negative terms like barnyard, wild, ferment and manure.
High-quality naturals polarize those who work in coffee. Many see value in coffees that taste spectacularly fruity and believe they are extremely useful for showcasing the possibilities of flavour that coffee has to offer. Others find the wild flavours unpleasant or have concerns about producers who process more of their coffee through the natural process. With such an unpredictable process, a high-quality lot could be damaged irreparably and significantly reduce the producer's income.
The washed process
The goal of the washed process is to remove all of the sticky flesh from the coffee seed (or bean) before it is dried. This greatly reduces the chance of something going wrong during drying, so the coffee is likely to be worth more. However, this particular process is much more expensive than the others, and takes the following steps:
After picking, the coffee cherry has its outer skin and most of the fruit flesh stripped off using a machine called a depulper. The coffee is then moved to a clean tank or trough of water where the remainder of the flesh is removed by fermentation.
The fruit flesh contains a lot of pectins and it is firmly attached to the seed but fermentation breaks down the remaining flesh enough for it to be washed away. Different producers use different amounts of water during the fermentation stage, and there are some environmental concerns about this method, partly due to the eventual fate of the wastewater, which can be toxic.
The amount of time that fermentation takes depends on several factors including the altitude and ambient temperature. The hotter it is, the faster this process will occur. If the coffee is left too long to ferment then negative flavours can creep in. There are many different methods for checking whether the process is finished.
Some producers rub the coffee as it will squeak if the fruit flesh has broken down, leaving the seed completely smooth. Others put a stick into the tank and if it stands up, supported by the slightly gelatinous water full of pectin, then the process is done.
After fermentation, the coffee is washed in water to remove the leftover debris, then it is ready to be dried.
Regardless of whether the natural or washed process is used, the coffee needs to be dried. This is usually done in the sun by spreading out the coffee on brick patios or raised drying tables. In the same way as the natural method described above, the coffee must be turned regularly with large rakes to ensure slow and even drying.
Where there is a lack of sunshine, excess humidity, or simply huge quantities of coffee to be dried, some producers use mechanical dryers to dry the beans down to a moisture content of around 11 - 12%. The vast majority of these driers are powered via the burning of fossil fuels such as firewood, which is collected through the unfortunate practice of deforestation. A key area where Don Maslow Coffee is different is that our dryers are powered by solar energy and biofuels which are entirely sustainable and preserve the high altitude cloud rainforest where our coffee is grown.
After drying, the beans are still enclosed in their layer of parchment (unless they have been processed by a semi-washed hybrid method). Now the moisture content is low enough for the coffee to be stored without risk of rotting. Traditionally, coffee is intentionally stored at this stage in 'reposo' (at rest) for thirty to sixty days.
The traditional practice of holding the coffee in 'reposo' has not been fully researched, although anecdotal evidence suggests that if this step is missed then the coffee can taste green and unpleasant until it has aged further. There is also evidence that this stage influences how well the coffee will age once shipped, probably linked to the moisture content within the coffee.
At the end of this period, the coffee is sold and then hulled to remove the parchment. Up until this point the parchment has provided a protective layer, but it also adds weight and bulk to the coffee so it is removed to make shipping less expensive.
The hulling is done mechanically in a dry mill (as opposed to a wet mill where the coffee was processed to remove the flesh and dry the beans). Dry mills also usually have equipment to grade and sort the coffee. Once hulled, the green coffee can be passed through a machine that examines the colour and rejects any coffee with obvious defects. The coffee can be sorted by bean size using large shaking sieves with varying hole sizes, and finally, it is graded by hand.
This time-consuming process is performed at a large table with a central conveyor, or sometimes on large patios, usually by women rather than men. They pick through their allocation of coffee and remove all the defects if they can, sometimes within a given time frame controlled by an automated conveyor. This is a slow process, adding significant cost to the coffee, but also massively increasing its quality. It is undeniably a difficult, monotonous job and it's right that high-quality coffees cost more, so that the people who do this difficult work can be better paid.
The coffee is now ready for bagging, either into 60kg (132lb) or 69kg (152lb) jute bags, depending on the country of origin. In some cases the bags are lined with a protective material, such as a multilayer polytheylene, to make them resistant to moisture, or the coffee can be vacuum-packed and shipped in cardboard boxes.
Jute has long remained the material of choice because it is cheap, accessible and has little environmental impact. However, as the speciality coffee industry is increasingly concerned with the condition of coffee during shipping and in ongoing storage, new materials are being explored.
Coffee is generally transported from its country of origin in shipping containers. Transporting coffee in container ships has a relatively low impact on the environment (certainly compared to other aspects of the coffee industry), and it's also relatively cheap.
Shipping is also a complicated process, with bureaucracy in many countries causing roasters huge amounts of stress due to the complicated paperwork required. Once Don Maslow Coffee arrives in the USA, it must pass through customs and the Food and Drug Administration (FDA) before it travels to our special storage facility to onward shipping to our final customers.