This week in the DBMH blog we’re going to be talking about washing your coffee. That’s not to say that you should be washing your precious beans when you get them home; rather, we’re going to be looking at the differences in how coffee is processed between harvest and export. The two main methods I’ll cover are the natural process and the washed process along with a method known as the honey process, which falls somewhere in the middle.
Before we dig in, a basic understanding what coffee looks like before it is processed will be helpful. Above you’ll see a simplified cross-section diagram of a coffee cherry. The three main components I’ll be discussing are the fruit flesh or pulp, the mucilage layer, and the coffee bean itself. The differences in the processing methods come from how the beans are dried and how the fruit flesh and mucilage are removed.
The natural process, which is the oldest and perhaps simplest method of processing coffee, is still used today. The cherries are harvested from the trees and laid out in the sun on large tarps or raised beds. The cherries are turned periodically to insure even drying. One of the inherent risks to this process is that some beans may remain underneath for too long, allowing for mold to grow and ruin the flavor of the cherries. Despite the risks, this method has persisted through the years due in part to tradition, but also the fact that it requires far less water and is consequently a more viable option in arid regions where water is scarce. Once the cherries are dried, the pulp and mucilage can be easily removed from the bean which is then graded, bagged, and exported. Naturally processed coffees, when handled properly, can produce wild and exotic flavor notes such as fruit juices and floral aromas.
Fully washed is another, more popular, system used to process green coffee. Once the cherries are harvested the flesh is removed via a mechanical de-pulper, leaving the beans encased by the mucilage layer. At this stage the mucilage is difficult to separate from the beans prior to drying. With the mucilage layer still intact, the beans are placed in a large tank of water where they are subjected to a fermentation process. This process must be carefully monitored to insure that the beans do not begin to degrade in quality. When handled correctly, the fermentation causes the mucilage to loosen. The layer is then simply washed off and the beans are dried much in the same way as naturally processed coffee. From there they are also graded and exported. Fully washed coffees are much more common and provide more familiar flavor profiles such as nutty, earthy, or chocolatey.
Given that there are two layers separating the bean from it’s destiny as delicious coffee, several methods of processing have been developed that fall somewhere in between fully washed, and natural processing. The honey process is one of them. Once harvested, the cherries are depulped in the same way as the fully washed process. However, instead of washing the mucilage off, they are left out to dry and turned periodically. Once dried, the mucilage is removed and the beans are graded and exported. This method has less risk of mold during the drying stage than the natural process, though the beans still need to be diligently turned to prevent this. The resulting flavor profiles can often be fruity and floral, similar to the natural process, however, these flavors will not be as prominent.
Coffee is produced throughout the world by people of vastly different cultures. It is no wonder that a wide variety of methods exist to take an unassuming cherry and transform its seed into a nearly miraculous beverage. No method is definitively “better”. Simply, the process preferred is often determined by what are the sought out flavors or by what the geographical conditions require. Hopefully now you find yourself armed with a better understanding of what coffee goes through before it reaches your cup.
James Hoffman’s World Atlas of Coffee which contains a section dedicated to coffee processing, was used as a reference for this entry in the DBMH blog.