What Is Anaerobic Processing
Over the years, we've featured a LOT of anaerobic processed coffees in The Roasters Pack. But… what exactly is this processing? We’re here to clear up any questions, comments, or concerns.
While the name anaerobic processing sounds nouveau and fancy, it’s really just an extension of the same principles that go into most coffee processing methods. Nearly all coffee undergoes some type of fermentation whether it’s natural or non-mechanically washed. Fermentation will begin as soon as coffee is picked due to the presence of water, sugar, bacteria, and yeast. The sugars and acids in the coffee’s mucilage are then converted into different acids, CO2, ethyl alcohol, and other compounds. The beans will ferment somewhat differently depending on whether they are washed, naturals, or honeys, leading to a variety of flavours.
So what makes anaerobic processing different from the rest? The key is oxygen, or rather the lack of it. The vessels in which the coffee cherries are fermented don’t contain any oxygen at all. The oxygen is removed when the coffee is added at the beginning of the process, and valves on the tanks keep oxygen from seeping in during the process while also allowing CO2 to be released as it builds up during fermentation.
The process of anaerobic coffee starts with the coffee being pulped. The beans are removed from the coffee cherry and added to the bottom of the tank. The next step is for the coffee producer to obtain the coffee mucilage, the part of the coffee cherry that surrounds the seed and has a honey-like consistency to it. This part is squashed down to a very thick and viscous gel, which is then spread over top of the coffee beans in the tank. Then the lid is sealed and fermentation begins! This process can last anywhere from 24 to 90 hours.
One of the major upsides of anaerobic coffee is that the producer has a lot more control over the fermentation process. There is no influence from the outside environment, the quality of the air, or the humidity. Once the producer has nailed the process, the taste of the coffee can be consistent and controlled.
So what’s the outcome of this lengthy process? The coffee that has been anaerobically processed is usually fruitier and juicier than its counterparts. Some say that the additional pressure forces the juices and sugars into the bean, creating sweet and complex coffee with an extra layer of funk!