Coffee processing’s main function is the separation of coffee bean from the coffee cherry and then drying it for shipping and/or roasting. Whilst all coffee must dry to a set parameter farmers can process this coffee in various ways.

Basics

All coffee received by the coffee processing mills, regardless of picking method, will contain coffee cherries (thus coffee beans) of varying ripeness. Initial reception of these cherries involves a sorting of these cherries and foreign matter. After this the coffee can be processed in various ways, the main (but not limited to) methods are:

• Natural or dry
• Washed
• Semi washed or pulped natural
• 
  

Natural or Dry.

Known as natural because it is the simplest processing method requiring little to no machinery. Coffee is received, then leaves and lighter foreign matter is separated by winnowing* or during floatation; along with the stones, over, and under ripe cherries. The ripe cherries are then taken whole, to drying beds or patios and laid to dry until moisture is 10-12%. During this process they are continually turned to maintain even drying and reduce potential rot and fungal spread.

Once Dried the coffee cherries are stored in silos that should have stable conditions so no further changes to the beans can be made. Natural coffee presents the cheapest processing option for farmers or mills to prepare their produce for sale. A extra benefit is that natural processing uses minimal water thus making it more ‘eco-friendly’.

Washed.

As with all processing washed goes through winnowing & flotation. The key difference is the method by which the cherry flesh is removed. Washed coffee, post sorting, is de-pulped to remove the cherry skin & flesh. This is done mechanically by squeezing the cherry to extract the bean incased in the parchment (protective layer). The coffee is then passed through vibrating screens to remove any imperfections.

After this the ‘parchment coffee’ is placed in tanks to ‘ferment’ remove any remaining coffee pulp. This can be as short as 8hrs or as long as 72hrs depending on local techniques & practices. The fermentation process ends when the parchment becomes rough and stone like. The coffee is then stored like this as it helps stabilize the coffee.

Semi-washed or Pulped Natural.

Existing in the space left between Washed and Natural processing, is Pulped natural. First pioneered in Brazil as “Cereja Descasccado” or CD it combines the two, resolving the issue presented by “strip picking^”.

After initial floating (as per dry process) the floaters (under ripe) are separated and dried slowly to make sure they don’t turn black. The remaining mass is then separated and the green cherries are dried in the same manor. The remaining mass of cherries (ripe) are pulped, with the option of fermentation for further flesh removal, and then dried.

*Winnowing: the act of removing foreign matter from coffee. Either by throwing the coffee in a large sieve like apparatus or mechanically

^Strip picking: when all cherries not just ripe ones are removed by hand or machine.