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.
