Processing the Coffee Harvest
Despite the method of harvesting (hand-pick, hand strip, and mechanical), the processing of the coffee cherry must start on the same day as the harvest. This prompt action avoids undesirable fermentation and mould contamination, affecting the fruit pulp surrounding the coffee beans.
There are three main types of coffee cherry processing – ‘natural’, ‘pulped-natural’ and ‘washed’. Despite the method of process, it is important to wash-separate the cherries (in countries where water is freely available), to eliminate rocks and impurities along with over and under-ripe cherries before processing begins.
‘Natural or Dry Process’ – here the whole coffee cherry, made up of bean, mucilage, pulp and skin, are placed outside to dry naturally. Often dried on large ground-based patios or on raised racks covered with cloth, cherries are left out under the sun to dry-down by moisture evaporation. Turned daily to afford even drying, this process produces a good coffee with excellent body, maintained fruit character and solid aroma.
‘Washed or Wet Process’ – this mechanical process requires even-ripe cherries for best result. The mechanical pulper removes the beans from the skin and fleshy pulp, leaving a bean covered in slimy mucilage. The parchment bean is now placed in fermentation tanks where, covered with water and an enzyme accelerator, the sticky mucilage ferments and is easily washed-off. The resultant clean and wet bean is them mechanically or sun dried, down to around 11 – 12% moisture. Wet processed beans generally are more delicate and ‘clean’ flavoured, with less body and fruit characteristics than the natural process.
‘Pulped-Natural Process’ – this is an intermediate process between the natural and washed methods. Here the coffee cherries are mechanically pulped, resulting in the retention of the slimy mucilage. These parchment beans are subsequently dried-down to 11 – 12% moisture, with the mucilage still in place. Later hulling of the beans to remove the parchment covering, results in a bean with more body and natural fruit character, than the washed process delivers. Many plantations utilize several different processes to produce variable cupping characteristics from the one source. This offers the roaster a huge portfolio of beans to roast and blend with.
