There are 3 main ways of processing the cherries, namely Fully washed, Semi-washed and Dry/Natural process (Picture above: Coffee processing).
Fully Washed process
The harvested coffee cherries are brought to a processing mill where they are soaked in water. The ripe ones will sink whilst the mature and unripe ones will float. The ripe ones will be pulped and placed in fermentation tanks for 24 – 36 hours to ferment until the mucilage can be easily washed off. It is also necessary to thoroughly wash the pulp afterwards to ensure that no fermented mucilage remains.
The coffee cherries will have their skins removed during the pulping process, but this time the sticky flesh layer of the pulp is left around the beans. The parchment coffee will subsequently be dried to a moisture content of approximately 12%. This will done by laying, turning and raking the coffee on either cement areas or tarpauline sheets.
Dry / Natural process
The cherries do not go through the pulping process at all, but are instead spread out in thin layers to dry in the sun. The drying stations can be a little different depending on the farm or region; some use brick patios, cement floors and others special raised beds (=tables), which enable air to flow around the cherries, thus more even drying. The cherries are also turned regularly to avoid mould, fermentation and rotting.
Once the cherries are properly dried, the skin and dried fruit flesh are removed mechanically and the green coffee is stored and “rested” before exporting it.
Regardless of the fermentation process used, the beans need to be dried until they reach a moisture content of around 11%-12%, which normally takes about 2 to 4 weeks (Picture above: Drying of coffee beans).
The beans also need to be raked regularly throughout the day to get them to dry evenly and ensure that no mold or bacteria develops.
MILLING AND SORTING
Milling is the next stage in the process where the parchment coffee are naturally brought out into the open with all their other layers removed. The 2 main steps in the milling process are hulling and polishing (Picture above: Coffee milling).
During hulling, the beans are poured into a Coffee Huller which removes the thin layer of parchment (endocarp) covering the beans, as well as the silver skin and any leftover dried fruit in the case of dry processed coffee. Once hulling is completed, the beans are run through a Polishing Machine, where the beans are made to look shinier and appealing by removing the silver skin around them.
The coffee beans must also be separated via Gravity Separators to distinguish the heaviest beans from the lighter beans, as the denser the coffee beans, the higher the quality.
Once milling is completed, the beans run through Coffee Sorting Machines to sort the beans in accordance to size. Another method is by hand whereby the beans are hand-picked. Screen Sizes vary from 20, 18, 16, 14, 12, 10 and 8.
Once ready, the coffee is assessed by professional coffee graders, who will grade the quality of the beans based on appearance, smell and taste. This will be done via a cupping process (Picture above: Professional coffee grader).