If you’ve just started buying green coffee beans, you may be confused by terms like “wet processing” and “dry processing.” Is one method better than the other? Which one is best for home roasting? In this article, I’ll take a look at three methods for processing unroasted coffee beans and share my thoughts with you on which one is best.
There are three ways to process the coffee cherries; wet processing, dry processing, and semi-dry processing. In all three methods, the bean/seed is separated from the cherry and dried. Each method influences the flavor of the bean in a different way.
Even after the beans are dried, they retain about 10% of their original moisture content. This is actually important, because it helps to keep the beans from becoming stale during shipment from their country of origin to your house. The beans are sorted, graded, and packed in large bags.
How Beans Are Processed
Technically coffee beans aren’t really beans at all, they’re seeds. The coffee seed grows inside a red berry about the size of an olive, which is known as a cherry. Coffee cherries are picked by hand or by machine and processed. Since different cherries on the coffee plant mature at different rates, picking by hand ensures that only ripe beans are processed. Obviously, however, picking by hand is much more labor-intensive and costly.
Dry Processing
The dry method is the oldest coffee processing method. And the dry method, Coffee cherries are spread out in a thin layer and left to dry in the sun. Each side of the bean needs to be exposed to the sun’s heat, so workers regularly rake the thin layers of beans to rotate them. This process can take 2 to 3 weeks, depending on the amount of sunlight in that region.
After the cherries are dried, the cherries are run through a machine to remove the outer flesh. This method is also known as the unwashed method, or the natural method. The resulting coffee is complex and sweet, with lots of fruity notes.
This method is often seen as the most environmentally friendly method. There are very few machines, and most of the work is done by the sun and by manual labor. This method is subject to weather, however. Heavy rain or prolonged sun exposure creates opportunities for fermentation, rot, and mold to ruin the crop.
Wet Processing
Wet processing is much more common than the dry method. In wet processing, the cherry’s outer layer is removed by a machine in a process known as pulping. The beans are then placed in a tank to ferment with bacteria and natural enzymes. This fermentation separates the sticky residue on the outside of the bean from the bean itself. The beans are washed to rinse off the residue and then dried.
Wet processing takes more water and more machines than dry processing. But wet processing is faster, usually taking less than 2 days. And the fermentation stage allows coffee farmers to produce different flavor profiles which aren’t available when using the dry method.
Semi-dry processing
As you might expect, semi-dry processing is a hybrid of dry and wet processing. And semi-dry processing, the outer skin of the cherry is removed but the sticky residue covering the bean is left intact. Coffee beans are then dried and the fruit residue removed later by machine.
Because the fruit remains in contact with the bean for longer, the beans absorb flavors from the fruit in this method. This method is also known as the “pulped natural” method.
Which method is best?
There are a lot of theories about which processing method is best and which method produces the best cup of coffee. The pulp which surrounds the coffee bean is full of different sugars. All things being equal, a dry processed bean will have a fruitier taste then an identical bean that’s wet processed due to the longer exposure of the bean to the pulp.
Whether you prefer that or not is a matter of personal taste. Even if you prefer that fruitier taste, it’s not a guaranteed result of dry processing due to variances in climate and individual coffee estates.
If your main concern is environmental impact, however, you should favor dry processed coffee because it uses fewer machines and less water. Be mindful, however, of the labor costs involved and look for coffee suppliers who pay a living wage to the farmers who are doing the back-breaking work of processing your beans.