15/01/2019
Last week we talked about the 3 primary coffee processing methods – washed, honey, and dry. What follows is a description of washed processing.
Washed Process is by far the most labor intensive, controlled, and complicated of the three primary processing methods. It also produces a brighter, cleaner cup, and a more developed flavor profile ….and for that reason, most quality Arabica coffees are “washed”.
The process begins with the harvest by selecting only fully ripened coffee cherries. Each coffee cherry contains (usually) two seeds. These are the coffee beans. Immediately after harvest, the cherries are washed for the first time. This not only cleans the cherries, but affords the first of several flotation cycles. Defective, over ripe, and under ripe cherries will float in the water bath. All “floaters” are removed. Remaining cherries are then pulped. Pulping is a mechanical process that removes the red skin, or pulp, that surrounds the coffee beans but leaves the sweet mucilage attached. The pulp is removed to compost. Coffee beans are washed and floated a second time immediately after pulping. The denser beans sink rapidly. Others are removed. (More on bean density later.)
Following the second wash, beans are covered with water and allowed to ferment. Fermentation is a natural process that consumes the mucilage and develops flavors and aromas inherent in the coffee itself. Fermentation times vary with temperature and humidity, but are generally in the range of 16-48 hours. Under-fermented coffees lack character and are more difficult to dry. Over-fermentation produces sour notes.
When fermentation is complete, the coffee is washed to remove remaining mucilage and stop fermentation. Agitation is the key. Some use concrete channels to tumble the seeds and remove mucilage. We wash 4-5 times with high pressure water in the same containment vessel used for fermentation. Each wash produces another flotation cycle. Even though the product of these flotations is small, it further refines quality through greater bean density. Following the final wash, we employ a natural process we have developed to further enhance flavonoids and bring out unique flavors inherent in the coffee. After that process, coffee beans are moved to drying.
Drying is typically accomplished in three ways – patio, raised bed, or mechanical. Patio drying spreads the coffee on a concrete surface, raised beds are tables with a screened surface and which can be protected from rain either by panels or in a structure designed especially for drying, mechanical drying is…well…think about a giant clothes dryer. We dry on raised beds in a structure designed for drying. It is important that the coffee is protected from weather, exposed to sunlight, and vented for airflow. Temperatures must be controlled so that they never exceed 104° F and drying is completed in not less than 8 days or more than 12 days. High temperatures and rapid or over drying will kill the embryo in the coffee bean and affect taste and quality. Longer drying times produce a musty taste in the coffee.
Once fully dried to 12% moisture, beans are hulled to remove the pergamino (a hard “skin” that surrounds the seed) and the silverskin (a membrane that surrounds the seed inside the pergamino) and are then roasted. The product after hulling is known as “green coffee”. It is the most often exported, being sold to distributors, brokers, and roasters worldwide.
More next week on Honey and Dry Processing.
