Characteristics and Flavor Profile of Anaerobic Fermentation Processed Coffee Beans - Steps and Procedures of Coffee Anaerobic Enzyme Fermentation Processing

Innovative Coffee Processing Methods

Today's coffee processing methods are emerging endlessly. After understanding the "traditional" processing methods like washed, natural, and honey, we now have "new" processing methods such as anaerobic, enzymatic, and carbonic maceration. FrontStreet Coffee has also encountered many novel and peculiar processing methods. The coffee beans produced through these methods generally exhibit "special" flavors, making people curious about how these flavors are created.

Anaerobic Processing

Anaerobic processing is a step in the treatment process. Generally, processing methods will be identified as anaerobic natural, anaerobic washed, or anaerobic honey. Essentially, the processing of these coffee beans still follows natural, washed, or honey methods, but with the addition of the anaerobic step to these traditional processing foundations.

Adding anaerobic steps during processing mainly utilizes anaerobic bacteria to break down sugars in coffee into organic acids such as lactic acid and acetic acid, as well as aromatic substances like esters and aldehydes in oxygen-deprived environments. This causes coffee beans to produce special flavors. For example, FrontStreet Coffee, when using the anaerobic natural Geisha from FrontStreet Coffee's Deborah Estate Savage series, detected not only the floral and citrus flavors inherent to Geisha but also a yogurt-like acidity.

Anaerobic fermentation steps are divided into two methods: vacuum-sealed and non-vacuum-sealed. Vacuum-sealing involves packing freshly harvested coffee cherries or depulped coffee beans in plastic bags or stainless steel barrels (sometimes plastic barrels are used), then extracting the air and sealing them for fermentation. The fermentation time depends on the estate's processing technology, mostly ranging between 36 to 168 hours.

The non-vacuum method involves filling stainless steel barrels with coffee cherries (beans) and sealing them directly. Bacterial colonies perform aerobic respiration, consuming oxygen to produce carbon dioxide and water, thereby depleting the oxygen within the sealed barrels to achieve an anaerobic effect.

Common anaerobic processing methods include anaerobic natural and anaerobic washed. Anaerobic natural processing involves placing freshly harvested coffee cherries in sealed barrels (bags) for anaerobic treatment, followed by conventional natural processing steps for the coffee cherries inside the sealed barrels.

Anaerobic washed processing involves depulping freshly harvested coffee cherries, then placing the coffee beans in sealed barrels (bags) for anaerobic treatment, followed by washing the beans inside the barrels to remove the mucilage layer attached to the coffee beans, and then proceeding with conventional drying steps.

Carbonic Maceration

Carbonic maceration processing, also known as CM processing, belongs to the category of anaerobic processing. However, because Sasa used coffee beans processed with this method to win the World Barista Championship in 2015, it drew attention to this novel processing method.

This processing method actually draws inspiration from red wine fermentation techniques, adding carbon dioxide to sealed stainless steel barrels. Therefore, in some places, carbonic maceration processing is also called the red wine processing method.

Similarly, carbonic maceration is also divided into natural and washed versions. The difference lies in the materials fermented in the barrels—the natural version uses coffee cherries, while the washed version uses depulped coffee beans.

Taking the natural version as an example, freshly harvested coffee cherries are cleaned and then placed in sealed barrels, where carbon dioxide is injected. After carbon dioxide injection, certain pressure forms inside the barrel, which will "burst" the coffee cherries, releasing juice rich in yeast and other microorganisms that help ferment the coffee beans. High concentrations of carbon dioxide inhibit the reproduction of aerobic bacteria, while anaerobic bacteria like lactobacillus and yeast multiply in large quantities.

Generally, fermentation in the barrels for 36-48 hours is sufficient to proceed to subsequent drying steps. Of course, whether the flavor of anaerobically processed coffee is good and the actual fermentation time required depends on parameters such as temperature, pH value, pressure, and sugar content during fermentation.

Enzymatic Processing

Some anaerobic processing methods include the term "enzyme," such as anaerobic enzymatic washed processing. What does this enzyme mean? Enzymes are actually proteins that can catalyze the fermentation process with the help of microorganisms like yeast. Anaerobic enzymatic washed processing actually involves adding enzymes during the anaerobic steps to help achieve better fermentation of desired flavors. The principle is similar to adding fruit pulp, coffee cherry mucilage, and pectin to coffee beans for anaerobic fermentation.

Conclusion

To summarize, anaerobic processing is just a processing step, and not all anaerobic processing requires adding catalysts (enzymes). Carbonic maceration belongs to a type of anaerobic processing. Anaerobic processing is just a general term; in actual operation, various parameters interact with each other. Naturally, even with the same anaerobic natural processing, the flavors can vary dramatically. Enzymes are catalysts that help microbial fermentation and belong to the category of proteases.

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