Green-coffee processing affects cup quality as well as how one should roast beans. Once a bean has been processed, a roaster must carefully control its packaging and storage conditions to prevent degradation of quality before it's roated.
Primary Processing Methods
Washed, natural, and pulped natural are the three primary processing methods of specialty coffee.
The washed, or wet, process consists of the following steps:
1. Pulping of the cherry to remove the skin.
2. Removal of the sticky mucilage layer by fermentation or mechanical means.
3. Washing of the beans to remove loosened mucilage
4. Drying of the beans in parchment, either mechanically for 1-2 days or in the sun for 3-16 days.
The natural, or dry, process consists of partially or completely drying the coffee cherrries on the tree and then husking the cherries to remove their skins. Alternativelty, the cherries are picked when ripe and then dried before husking.
In the pulped/natural process, the cherries are pulped to remove their skin and set to dry with the mucilage layer intact. This method delivers a sweeter, cleaner cup than does the traditional natural process.
Washed processing produces cleaner, more acidic, more consistent, and generally more priced coffee than natural processing does. Washed coffees also tend to be denser and require more aggressive roasting. The dry process can take several weeks and yeilds coffe with less acidity, more body, and earthier flavors than washed coffee. Arid growing areas oftern use the natural process because it requires much less water than the washed process. Natural-processed coffees burn more easily during roasting, so one should use lower charge temperatures and gas settings when roasting those beans.