Processing the Beans

Processing the Beans

The beans are actually the core or seeds of the coffee cherry. There are normally two beans in each cherry, turned flat side together; each is surrounded by a thin, delicate membrane called the "silver skin", which in turn is covered by a pale parchment shell, about as hard as a fingernail. The parchment-encased beans are surrounded by the sticky yellow pulp of the fruit, whose outer coating is the red skin. The beans must be removed from the fruit, which is a demanding job.

The simplest process is that used in poorer regions where machinery is too expensive, or where there is a dearth of water. This is called the the dry process, and the beans will be described rather dubiously as "unwashed". Even so, the first step is to wash the cherries, which allows a certain amount of fermentation to occur even though they are immediately spread out on patios or drying boards. For from to three weeks they will be raked and turned (or possibly subjected to hot air machines) during the sunny days and covered at night to prevent contact with condensation. When they are thoroughly dried they will be run through hulling machines (also know as shelling or milling machines), which simply rub off all the dried outer casing, including the parchment and most of the silver skin. Next the green beans (as they are called until they are roasted) are cleaned by air-blasting and then sorted for size and color, either by hand or machine. At this stage it is important to remove, if possible, any black, broken, diseased, or generally defective beans. The dried cherry wastage is usually burnt as fuel, or occasionally used as fertilizer, and the beans are bagged and labeled.

In regions where machines and water are more accessible, coffee cherries are processed by the "wet" method. The cherries are submerged overnight in large tanks of water, which causes the cherries to burst, breaking the skins. They are floated, via a series of sluices to the pulping machines, which separate the beans and their parchment casing from the skin and most of the yellow pulp. They are soaked again in the sluices to enable the fermentation process to loosen any remaining pulp, after which they dry in the sun. Any beans destined to germinate and be seeds for new plants must be selected and removed before the beans lose their parchment and silver skin in the next machine. As with dry-processed coffee, the wet-processed beans are passed through sorting and grading machines, where they will be assessed and separated by size, density and color, and finally bagged and labeled as wet-processed, or "washed", green beans.

Whether the wet or the dry method produces the better flavor seems to be a matter of personal taste. It is often said that the wet method is more controllable, predictable and consistent, but in the rare instances of samples of washed and unwashed coffee from the same plantation being available, the unwashed coffee is just as likely to be the favorite as the washed.

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