Before being roasted, coffee is the green bean that comes from a coffee cherry. These cherries grow on large bushes in clusters that are hand picked when ripe. The bushes can grow up to 30 feet tall and have a life span of 20 – 30 years. However, they take a while to produce coffee beans; it takes nearly a year for a cherry to mature after the flowering of the white blossoms.   

There are two main species of coffee plants: Coffea Arabica and Coffea Canephora, commonly known as Arabica and Robusta.  The Arabica plant is more delicate, preferring to grow at higher altitudes—at least over 900 feet above sea level—and requires more intensive cultivation than Robusta. In contrast, Robusta coffee plants are grown at lower altitudes and sometimes in harsher environments. Unfortunately, the Robusta plants resilience produces a more astringent bean. Coffees made from Robusta beans have more caffeine, tend to have a bitter flavor, and are generally considered lower quality. However, there are a few higher quality Robusta varietals grown that are primarily used in espresso blends, especially Italian style.

It is from the Arabica species that almost all specialty coffees are derived. Unlike Robusta coffee plants, Arabica has four sets of chromosomes as compared to the two sets Robusta plants have. This allows the coffee to pick up significant flavor characteristics from the environment, explaining why coffees from different regions have different unique tastes.  Interestingly enough, all Arabica plants are descended from the original coffee trees discovered in Ethiopia but since they now grow in different environments, they display a variety of characteristics.

After ripe coffee cherries are picked, the outer cherry must be removed. There are three main techniques used to process cherries, which influence flavor and appearance: Wet, Dry or Semi-Dry.

Wet Process

In Wet Process, the outer skin of the coffee is removed with a machine exposing the sticky pulp. Coffee is then put in open tanks allowing the pulp to ferment, which literally consumes the majority of the pulp. Any pulp that has not been consumed by this process is easily washed away with water. At this point the coffee is dried by a machine or by the sun. This type of processing produces coffee with cleaner flavor but a little less body.

 
Dry Process

In Dry Process, the beans are picked then set out in the sun immediately to dry with the whole cherry attached. The cherry and skin are then removed in one single step. This process imparts a fruity flavor to the coffee. Some coffees grown in Ethiopia use this process, and is part of the reason they tend to have such strong fruit overtones.

 
Semi-Dry Process
 
The last main method is Semi-dry, a hybrid of the other two methods. Immediately following picking, the outer skin of the coffee is removed. Unlike the wet method, the pulp is not fermented, but is dried along with the silvery skin and parchment. These layers are then removed in one step by a machine. This will affect the coffee precisely how you would expect it to: cleaner than the dry method but still imparting more of the fruit flavor than the wet method does.

 
Understanding how the growing and processing of the bean affects the coffee is only the first step of coffee’s journey, but is an important one. Obviously, one cannot produce an excellent coffee with poor green beans. However, to produce a great cup of coffee, one must also be an expert in roasting and brewing.