Fermentation and coffee (EN)

Fermentation is a word which has a specific meaning in coffee, a bit different from the scientific definition used in microbiology.

In coffee when we talk about fermentation we talk mainly about a stage of coffee processing, which happens between depulping and drying. After we depulp the coffee beans from inside of the cherry, the beans are covered in a sticky sugary substance, called the mucilage.

In coffee, fermentation is process of removing this mucilage from the beans before we dry them. Commonly producers place the beans in a large tank and leave them “ferment” for a couple of hours, until the bacteria dissolve the mucilage enough that it can be washed away with water. There are many ways to do this. You can ferment coffees in tanks filled with water, so there’s low to no oxygen environment or you can ferment without adding water. When the coffee is fermenting you can seal the tank shut with a one way valve, so that no oxygen can get in and remaining oxygen is gradually pushed out. This way you create a fully anaerobic (no oxygen) environment. Additionally you can also add carbon and flush the oxygen from the tank right away, a process inspired by the wine industry, known as carbonic maceration.

The big question today is whether we can use fermentation not only to help producers process the coffee better but whether we can use fermentation to create specific flavors we want in coffee. In this regard, research is still inconclusive. It does seem to suggest, that fermentation improves aroma of coffee, but for flavor more research still needs to be done.