Coffee Processing and Storage

Most coffee beans are made up of two flat-sided seeds – the peaberry has one single small bean - which lie within the flesh of the ripe cherry.

Wet processing

Wet processing is relatively expensive, but is beneficial to the quality of the coffee, due to the fermentation process, which takes place during wet processing, imparting certain beneficial flavours to the bean. The berries are first soaked in water to remove impurities, and any unripe berries are left to sink to the bottom, leaving the ripe fruit to float on top. The ripe berries are collected after soaking and ‘depulped’ – usually with the help of a machine – to remove the outer flesh and then put into large water tanks where they are left to ferment. This process (which lasts a couple of days) removes the non-soluble parts of any remaining flesh and also imparts aroma and flavour to the bean.  On completion of this fermentation process the coffee beans are washed again.

In some areas and on some estates, machines are utilised to eliminate the fermentation stage and obviously this has some effect on the flavour. At this stage of wet processing, the beans are still covered by what is known as a parchment husk, and for this reason the beans are referred to as 'parchment coffee'.

The washed parchment coffee is next spread out on to concrete slabs or drying racks and left out in the sun to dry naturally. The beans are turned several times a day to ensure even drying. Depending on weather conditions, this process can take five or six days. Large coffee growing estates make use of drying machines - huge metal drums inside which hot air circulates - and to ensure the beans dry evenly, the drums rotate continually. This drying process lasts about 24 hours. Dried parchment coffee has an attractive golden yellow colour and is known as ‘pergamino’ (or ‘oro’) coffee.
The next stage of the story is the storage of the pergamino coffee beans in large silos prior to them being mechanically hulled (the removal of the dried outer ‘husk’) by special machines with grooved cast iron cylinders.

Coffee Dry Processing

Dry processing is utilised in Brazil and across a large part of Africa - generally for lower quality Arabica and Robusta coffee cherries. This is a simple technique, which is less labour intensive than wet processing - however cheaper production costs must be offset against a loss in quality, since the length of the drying process is dependent on the climate.  Once all twigs, leaves, and other foreign objects have been sieved out, the dry processing begins. The coffee cherries are processed immediately after harvesting, either by sun drying, solar drying or artificial drying. In sun drying, the coffee cherries are placed on a clean floor and left to dry in the open air. In solar drying, the cherries are placed in a closed cabinet in sunlight, which has ventilation holes to let moisture out. Artificial drying is used mostly during the wet season, when the low level of sunlight means the time needed for solar drying makes the cherries prone to mould. After drying, the cherries are hulled in the same way as the wet processed ones.
At the end of the hulling process the beans attain their familiar olive green colour, however some varieties have a blue shade and are the high quality so-called 'blue' coffees.
Finally the finished coffee beans are packed in to 60 kilo bags (although Colombia still insist on using 70 kilo bags) and stored in dry cool barns or warehouses.
The cultivation and processing of the coffee bean is now largely at an end, and the producer will next sell his product on to a wholesale distributor or exporter.