Green Coffee Beans are actually the seeds from the fruit of Coffee Trees
Fresh coffee beans are green when removed from the fruit of the tree. It is the roasting process that changes them from green beans to the various shades of brown, depending on your roast preference. So in the industry, Green Coffee simply means unroasted coffee beans (that are ready for roasting).
There are two main species of coffee trees:
- Arabica - the source of our premium specialty coffees
- Robusta - a heartier, more prolific tree, with higher
caffeine (unfortunately it often has a rubbery, flat taste)
While some coffee blends do contain beans from the Robusta tree (to add caffeine, body and crema). In general, specialty grade single origin coffee comes from the Arabica plant.
The SCAA standard for Arabica Coffee is subdivided into 5 grades, distinguished primarily by the number of "defects" the coffee contains per pound. For example, grade 1 coffees must have less then 5 twigs, or broken or discolored beans, etc. per pound. In general, the coffees here at Burman Coffee Traders are grade 1 Arabica, the best coffees available.
However, sometimes we discover an excellent coffee from a region that grades their coffee differently, i.e. that contains a higher number of broken beans, etc. The Yemen Mochas and some Ethiopians are such coffees.
Processing Methods of Green Coffee
Before they can be roasted, green coffee beans must be separated from the moist, sweet cherry pulp and inner hulls, then cleaned and dried. This series of steps is known as processing or preparation (prep). The main processing methods are known as natural (dry), washed and semi-washed.
The method used for preparing beans has a dramatic effect on coffee flavor, as we’ll see below. Also, preserving the subtle, intense cup quality of Specialty beans requires processing steps far beyond the simple hulling and drying needed to prepare other coffees, seeds and grains for their markets. These extra steps, directed by expert quality management, add significant expense and value to specialty coffee beans.
Natural or Dry Processing
The traditional way of preparing coffee beans for market, it is the preferred method for many origins, especially where water is at a premium. At its most basic, ripe cherries are spread on the ground in the sun. When the fruit is dry, it’s pounded and winnowed to separate the beans away from the dried fruit and hulls; they’re then graded, weighed and bagged.
In terms of appearance, the presence of fruit pulp during drying and the pounding during cleaning mean that Natural beans are pretty varied in color and shape. Many technical quality improvements have been incorporated to prepare Naturals for the specialty market - drying patios of gravel/cement instead of earth, or elevated racks to facilitate quicker drying. Also, machinery is now commonly used to hull, separate and clean the dried beans. The result is cleaner cupping specialty Naturals with beans that have a more consistent appearance.
In the cup, Natural coffees exhibit heavier body and flavor profiles with deeper-toned and more varied fruit, chocolate, spice and savory notes than the same beans prepared by the washed method. These coffees add depth and authority when used in blends. Natural coffees tend to have more chaff when roasting.
Washed or Wet Processing
Wet processing, with its improved physical consistency, cleanliness and appearance of coffee beans, developed during the Industrial Revolution to facilitate advances in technology. It requires abundant water resources, and was pioneered in the tropical uplands of the New World.
Washed processing has 2 stages. The first “wet milling” stage starts with several washing and brushing cycles to separate the sweet pulp completely from the hull encasing coffee beans known as ‘parchment’. Next, the cleaned parchment soaks in concrete pools for several hours, allowing chemical changes that develop beans with very clean and bright flavor profiles. They are then dried; either by the sun on cement patios, or mechanically in huge rotating heaters called gardiolas.
In the second “dry milling” stage, the beans pass through a series of machines: they’re hulled and de-chaffed; graded by high-speed sorters to regularize size, color and/or density; then weighed, bagged and marked for shipping. The extremely consistent size, shape, color and flavor of beans processed by the washed method facilitates larger batch sizes and longer, darker roasting with less fire danger.
In the cup, washed coffees exhibit bright, clean flavor and aroma, with notes of fruit, citrus, floral and spice. Flavor is mainly perceived from tongue-tip through mid-mouth and up into the sinuses. Washed coffees have light to medium-heavy body, and provide a blend’s crisp, vital first impression.
Semi-dry or Semi-Washed Processing
A hybrid process used in Indonesia, Brazil and other origins with abundant water, it is used to improve the flavor and physical consistency of Natural coffees. It is used mainly for Specialty-grade beans due to its higher expense.
The process begins with removal of the outer cherry using wet pulping machines. The beans, still coated with sweet pulp, are ‘rested’ - cured for up to a day to develop the characteristic ‘Natural’ flavor profile. The pulp is again rinsed and the parchment coffee, still with traces of pulp, is fully sun-dried. Grading, weighing and bagging is accomplished in mechanized dry mills, similar to those used in wet processing.
By gently removing most of the fruit before drying, controlling the amount of pulp contact during drying, then using mechanized dry milling – coffee flavor, and especially its physical consistency, is greatly improved. The beans retain the same flavor and body as Natural process coffees.