Last week, we welcomed you inside the world of coffee by taking you through the first step of the amazing journey that each one of our humble coffee beans takes. This week we move on to the next part: processing.
Once the cherries have been harvested, they are ready to be made into green coffee. There are two ways to do this:
This is the traditional method of processing coffee. The picked cherries are laid out on a large, flat concrete surface to dry in the sun. They are raked and turned regularly to prevent them spoiling and are covered at night or in bad weather to keep them dry. Some smaller farmers have been known to simply use a cleared area of earth, but this can damage the coffee and give it an unpleasant ‘earthy’ taste. Increasingly farmers are using raised platforms. This allows the air to get in underneath the cherries and keeps them off of the ground where they can be damaged or fall victim to pests. After a period of weeks (normally around 4) when the moisture in the cherries is adjudged to be at around 11%, they are collected and moved to a warehouse.
Here they are hulled by a machine. It removes the entire husk and leaves only the bean. Each cherry has twin beans inside, but every now and then, a cherry will only have one bean. This is known as a ‘peabody.’
A further step is ‘polishing.’ This is when the beans have the silver skin removed from them, resulting in a shiny, smooth bean. This is an optional step and makes little to no difference to the flavour.
Dry processed beans normally result in a full-bodied flavour. 90% of Arabica beans are processed this way.
In some countries where water is in abundance, farmers will opt for wet processing. This requires huge amounts of fresh water and so is often avoided in dry climates like Africa, since the waste can be substantial.
The cherries are placed in water to sort them. Ripe cherries will sink while unripe ones will float. The ripe cherries are then pushed through a machine that removes the skin of the fruit and most of the pulp. The leftover pulp is removed by placing the semi-exposed beans into giant water-filled fermentation tanks. Over a period of around 48 hours, the mucilage (a gluey, protein substance) dissolves in the water via a fermentation process, leaving the beans with a rough surface. This stage needs to be carefully monitored, since over-fermentation can distort the flavour of the final product. Once this process is complete, the beans are thoroughly rinsed and then dried using either the methods described above or in a drying machine. These are large rotating drums that have the benefit of sheltering the beans from weather conditions but the drawback of potentially damaging the beans.
Wet processed coffee usually results in fruitier, acidic flavours. Robusta beans are most often wet-processed.
After being through one of these processes, the beans are sorted by size, density, and quality. All of the defective beans are removed and the rest, known as ‘green coffee,’ is stored ready for export.
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