Dry processing is a method of preparing coffee fruits (also known as coffee cherries) for hulling. During dry processing, the entire coffee cherry is cleaned and then dried. This method of processing is differentiated from wet processing, which uses water and either fermentation or mechanical methods to remove the fruit from the interior coffee “bean” prior to drying and hulling.
Dry processing is the oldest method of coffee processing. Coffee made with the dry process is also known as unwashed coffee (because it is different from washed coffee) or natural coffee (because its process is more natural than washed coffee).
The dry method is used for almost all Robusta coffee, most of the coffee is produced in Ethiopia, Haiti, and Paraguay, about 90 percent of the Arabica coffee is from Brazil, and some Arabica coffees are produced in India and Ecuador.
It is very popular in part because it requires far less water than wet processing. However, it is not used in very humid or rainy coffee-producing regions, as the beans cannot dry properly due to humidity and rain there.
Dry Process Coffee Cleaning & Sorting
After harvest, dry processing begins with cleaning and sorting. This is usually done by hand winnowing, using a large sieve. Unripe, overripe, and damaged coffee cherries are removed, as are leaves, twigs, soil, and other debris. What remains on top of the sieve is that is kept. Alternately, ripe cherries can be separated out from other materials with the floatation method used in wet processing.
Dry Process Coffee Drying
After cleaning and sorting, the core task of dry processing begins. This is the task of drying the beans, and it is the most important part of dry processing in terms of the impact on quality. Eleven percent moisture is usually ideal. Coffee that is not dried enough is susceptible to mold and fungus, while coffee that is dried too much will be brittle and is likely to break during hulling (and, usually, be discarded as a result).
During drying, coffee cherries are spread out in the sun, either on large patios or on tables. As the cherries dry, they are frequently raked or turned by hand, and they are covered or moved indoors during the night and during rains. This extra care promotes even drying and prevents mildew. While wet processing is a relatively quick process, dry processing may require up to 4 weeks before the cherries are dried enough. On larger plantations, machine-drying may be used to speed up the process after the coffee has been dried in the sun for a few days.
Dry Process Coffee Storage
After drying, the coffee beans are stored in large quantities in warehouses or special silos until they are ready to be sent to a mill for the next steps of processing (which are milling, polishing, cleaning and sorting, and grading). The fruit of the coffee cherry is not removed until the milling stage (also known as hulling). Unlike the multi-step process for removing the coffee fruit from the bean that is used in wet processing, removing the fruit from dry-processed coffee only takes one step.