Natural – also called the dry method and is the oldest and simplest by requiring little machinery. Here the coffee cherries are spread out in the sun either on large concrete or brick patios or on matting raised to waist height on trestles in layers of 1 to 4 inches. i. Here they are raked or turned by hand to ensure consistent drying. Sun-drying ideally takes 2 -3 weeks before the cherries are dried to the desired 11-13% moisture content but the duration is dependent upon the ambient temperature and humidity. The dried cherries are then stored in bulk in special silos until they are sent to the mill where hulling, sorting, grading and bagging take place.
The drying process is a critical stage as it affects the final quality of the green coffee. If coffee is over-dried it will become brittle and produce too many broken beans during hulling and if not sufficiently dried it will be too moist and become prone to rapid deterioration caused by the attack of fungi and bacteria.
Almost all the worlds Robusta coffees are processed by this method and as much as 90% of Brazils Arabica coffees are dry processed too.
Using this method the coffee beans’ sharpness and vividness tends to be muted while body and other heavy notes increase. This kind of milling is ideal for making espresso blends.
Pulped Natural – the fruit’s skin is removed at once and the remaining fruit, called mucilage, is then dried along with the coffee beans. The pulped natural process is similar to the natural process although this method does not produce as much body in the coffee as the natural process it allows brighter, more floral notes to surface in coffees.