Processing

After harvesting the coffee cherries, they must be processed. There are two main methods for preparing coffee beans for roasting, known as the ‘dry method’ and the ‘wet method’.
 
The simplest, cheapest and most traditional method is known as the ‘natural’ or ‘dry method’.  Once harvested, the whole cherries (bean, mucilage and pulp) are spread over dry ground or on a concrete, brick or matted surface to be sun-dried for a period of 2-3 weeks until the moisture levels in the cherries have fallen to around 12-14%.  Making sure the beans are properly dried is crucial.  (If the moisture content remains high, there is a high possibility of mold formations, such as Ochratoxin (OTA), Acrylomide, and Furan, which is not only unhealthy, but will also produce an extremely undesirable aroma and flavour.)  After drying, the beans are stored in silos or sent for hulling. This process is mainly used for processing Robusta beans.

The second method is known as the ‘wet method’.  It is a more expensive process as it requires more equipment, labour, time and water, and is usually used to process Arabica beans.  This method helps preserve the intrinsic qualities of the beans and causes less damage. 

First, the cherries are put through a washer to clean the cherries and skim away the unripe cherries.  Then the pulping process begins. The cherries are put through a pulping machine to remove the outer layers or the pulp.  The beans are then washed in flowing water to separate the mucous from the cherries.  After being washed, the beans enter a critical step, which is the fermentation process.  The beans are sent to a fermentation tank for 12-36 hours (depending on the temperature, the thickness of mucilage and the enzymes present) for soaking.  This step separates the slippery mucilage covering the parchment from natural enzymes.  This method must be carefully monitored so as not to negatively affect the flavour of the beans.  When the process is finished, the beans are no longer slimy, but rather have a ‘pebbly’ feel.  Water is then drained and the beans spread out to sun-dry, like in the dry method.  This process takes about 12-15 days, until the moisture content reaches around 12%.  Once dried, the process is still not complete. At this stage, the beans are known as “parchment coffee” and will usually remain in this form until exported or sold.