Anaerobic Processing in Specialty Coffee? What Anaerobic Processing Methods Are Used in Colombian Specialty Coffee?

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The known natural, washed, and honey processes are basic options for coffee processing. With the rise of the coffee market and the growing community of specialty coffee enthusiasts, many industry professionals have invested in developing innovative post-harvest coffee processing methods. Among these, the anaerobic fermentation processing method has gained significant exposure in recent years and is highly recommended by numerous coffee masters. At FrontStreet Coffee, a bean named "Floral Moon Night" from the El Svir Doka farm in Colombia's Huila region is processed using a variation of anaerobic processing - the anaerobic slow natural processing method. When brewed, it releases flavors that match its name, bursting with floral aromas and rich fermented wine-like notes.

The anaerobic fermentation processing method mentioned above applies the concept of winemaking to coffee bean post-harvest processing. The pioneer who achieved stable yields using this method stood out at the 2015 World Barista Championship (WBC) - none other than that year's champion, Sasa Sestic.

About Anaerobic Fermentation Processing

In fact, the anaerobic fermentation processing method was first invented by Costa Rican coffee farmer Luis Eduardo Campos, and it was several years later that WBC champion and Australian competitor Sasa Sestic promoted it worldwide. In its narrow definition, anaerobic fermentation processing is also called carbon dioxide maceration. This method originates from winemaking, where the principle is that carbon dioxide gas gradually increases during grape fermentation, entering an anaerobic state. The fermentation dominated by anaerobic bacteria converts the grapes' natural sugars into alcohol, producing wine with a smooth texture, refreshing flavors, and special aromas. Since coffee processing differs from winemaking in timeline, it requires争取ing brief coffee fermentation time. Therefore, the process directly uses pressurized carbon dioxide injected into sealed tanks, allowing coffee cherries to ferment in a completely oxygen-free environment.

The 2015 WBC champion Sasa Sestic selected a coffee bean from Colombia's La Palma y El Tucán estate, which was processed using carbon dioxide maceration. The principle involves placing complete coffee cherries (with skin and pulp intact) into a sealed stainless steel barrel, removing oxygen and injecting carbon dioxide, allowing them to remain in a completely oxygen-free environment. This forces the coffee cherries to undergo anaerobic fermentation and breakdown within their skins, while controlling variables such as pH value and temperature to ensure the final quality of the coffee.

Advantages and Disadvantages of Anaerobic Fermentation Processing

Compared to natural, washed, and honey processing methods that rely on oxygen-dependent fermentation, the oxygen-free anaerobic fermentation processing method produces more distinctive aromas. However, due to the lack of oxygen, the fermentation process is slower than traditional natural, washed, and honey methods. Once fermentation is complete, the beans are removed from the barrel and must be immediately dried to prevent continued fermentation (transitioning to aerobic fermentation). Traditional processing methods using oxygen fermentation can easily develop over-fermented acidic notes if not strictly controlled during production, whereas coffee beans fermented through oxygen-free methods produce brighter, cleaner flavors that are smooth to drink, with subtle notes of cheese, dairy products, and even wine-like aromas. The overall tasting experience can be described as refreshingly sweet and crisp.

The key to anaerobic fermentation is to minimize the impact of the external environment on coffee cherries and their fermentation process. Although it requires longer waiting times, the front, middle, and back notes, as well as the acidity and bitterness, are expressed in a more balanced and comfortable manner, while maintaining excellent aromatic richness. It is currently considered a highly regarded processing method.

With the influence of the coffee wave, global enthusiasm for specialty coffee continues to grow. From fruit growth to producing a final cup of excellent coffee, every stage is gradually being independently analyzed and controlled with greater scientific precision. Among these, besides continuously improving traditional coffee fermentation methods that have been maintained for centuries, emerging processing methods have sprung up like mushrooms after rain in recent years. In addition to the anaerobic fermentation processing method mentioned in this article, other methods still in their early stages such as anaerobic natural, anaerobic washed, and double anaerobic processing have also successively appeared. Before the stage of technical stability and maturity arrives, coffee enthusiasts have more diverse and interesting coffee flavors to try. If opportunity allows, why not analyze the flavor mysteries of these processing methods through tasting.

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