What is Anaerobic Processing? How Does it Differ from Natural and Washed Methods? What are the Characteristics of Anaerobically Fermented Coffee Beans?

What is Anaerobic Processing?

In 2015, Mr. Sasa Sestic used an anaerobically processed bean to win the World Barista Championship, completely opening the door to a new era of coffee processing methods. Since then, various anaerobic processing methods have emerged in abundance. Whether in coffee competitions or offline coffee shops, anaerobically processed coffee beans are everywhere.

However, as we can observe from our surroundings or online platforms, anaerobically processed coffee beans don't receive universal acceptance like traditionally processed beans. The reasons are twofold: one is that the flavor of anaerobic processing is too "distinctive," making it unacceptable to everyone; the other is that the anaerobic processing workflow is not well understood by many, easily leading to misconceptions. Therefore, anaerobically processed coffee beans are often a controversial subject. Today, FrontStreet Coffee will share what "anaerobic processing" actually is.

Understanding Anaerobic Processing

"Anaerobic processing," also known as "anaerobic fermentation," is a method that places coffee beans (coffee cherries) in an anaerobic or oxygen-deficient environment for a period of fermentation. In an anaerobic (oxygen-deficient) environment, the fermentation of coffee beans (coffee cherries) can be controlled, thereby producing distinctly different complex flavors. FrontStreet Coffee will briefly explain fermentation here - although it's quite common in daily life, it's extremely important! So-called "fermentation" is actually a biochemical process where microorganisms convert one substance into other substances through their life activities. For example, the fermentation of coffee beans converts the sugars in mucilage into alcohol and carbon dioxide!

However, we need to understand that not only anaerobically processed coffee beans undergo fermentation - traditional processing methods like natural, washed, and honey processing all involve fermentation of coffee beans. The difference lies in the degree, method, and direction of fermentation compared to anaerobic processing, and the flavors also change according to different fermentation levels. For example, why does washed coffee taste cleaner than natural coffee? It's quite simple - because the fermentation level of coffee beans in washed processing is not as deep as in natural processing, so relatively fewer substances are converted, resulting in a cleaner taste, but with less complexity and layers.

The Evolution and Requirements of Anaerobic Processing

Returning to our main topic, although Mr. Sasa Sestic popularized anaerobic processing, he was not the "founder" of this method. Anaerobic techniques were first used in winemaking, then applied to coffee processing by Costa Rican coffee farmer Luis Eduardo Campos, and finally used by Sasa Sestic in world competitions.

Many people might think: anaerobic fermentation processing simply involves putting coffee beans into a sealed container and letting them ferment automatically. But the reality is not as simple as imagined! Anaerobic fermentation requires not just a closed space, but a monitorable, completely opaque, and fully sealed container! Additionally, the ambient temperature where the sealed barrels are placed must also be strictly controlled! Only through this can producers control the fermentation level inside the barrels and guide the coffee flavors toward their desired target.

To achieve this, producers not only need to use carbon dioxide to expel oxygen before fermentation, but also constantly monitor temperature and pH changes during the coffee bean fermentation process. When the sugars in the mucilage and slime are completely broken down, the container must be immediately opened to stop fermentation, then other procedures must be quickly executed to avoid over-fermentation and negative consequences. Therefore, we can understand that anaerobic fermentation processing is not simply about putting beans in a sealed space - it has higher requirements than other processing methods. Thanks to this, coffee beans develop entirely new flavors distinct from traditional processing.

Besides the developed coffee flavors, anaerobically processed coffee beans also produce varying degrees of fermentation flavors depending on the fermentation level, which is another major characteristic. However, when fermentation flavors are too heavy, coffee can easily develop a strong "soy sauce" taste. The reason many people dislike anaerobically processed coffee is precisely because the "soy sauce" flavor is too overwhelming.

Variations of Anaerobic Processing

The names we see in the market, such as anaerobic natural and anaerobic washed, all refer to coffee beans that, in addition to undergoing anaerobic fermentation, also participate in traditional processing flows like natural or washed processing. Processes with "double" in their name indicate that coffee beans undergo two rounds of anaerobic fermentation during processing. In any case, merchants will directly abbreviate the general processing flow into the processing name, and we just need to understand them literally~

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