Anaerobic coffee processing, often referred to as "coffee fermentation", is a method of treating coffee cherries that leverages fermentation in oxygen-free environments to create distinct flavor profiles. Fermentation is not new to the world of premium products; think of how fermentation shapes the character of fine cheeses, wines, and sourdough bread. In coffee, it works similarly, breaking down sugars and compounds within the cherries and transporting them into the beans, leading to complex and often unexpected flavors.

The process starts by placing coffee cherries or beans in sealed, airtight containers. This creates an oxygen-free environment, enabling specific microorganisms, such as yeast and bacteria, to metabolize the sugars more slowly and under controlled conditions. The result is a precise transformation of flavors, textures, and aromatics that can be tailored to specific sensory outcomes.

In essence, anaerobic processing is a marriage of science and craft, allowing producers to push the boundaries of coffee processing and create truly unique flavor experiences.

Traditional Processing: Traditional methods such as natural, washed, and honey processing expose coffee to open-air environments. These approaches rely heavily on ambient microorganisms and environmental conditions, resulting in high-quality but less predictable flavor profiles.

Anaerobic Processing: In anaerobic methods, fermentation occurs in controlled, sealed environments, limiting oxygen exposure and allowing producers to regulate variables such as temperature, time, and the introduction of specific microorganisms. This precision enables the creation of distinct and reproducible flavor profiles.

Types of Fermentation:

• Non-fermented Coffee: Minimal microbial activity beyond basic drying.
• Wild Fermentation: Open fermentation with ambient microorganisms, leading to diverse but less controlled flavors. This is the case with natural coffees.
• Controlled Fermentation: Specific microbes, such as selected strains of yeast or bacteria, are inoculated to guide fermentation toward desired results.

Experimental Methods: Techniques like co-fermentation with fruits or varying fermentation stages add layers of complexity and creativity.

The fermentation process begins with freshly harvested coffee cherries, which are placed in hermetically sealed containers. These containers, often tanks, barrels, or even plastic bags, provide the controlled environment necessary for anaerobic processing. Key methods include:

• Carbonic Maceration: Whole cherries are fermented in a carbon dioxide-rich environment and under pressure, inspired by winemaking. This method accentuates wine-like acidity and creamy textures.
• Natural Anaerobic: Whole cherries undergo extended fermentation (e.g., 72 hours) in sealed environments, creating bold, boozy, and fruit-forward flavors.
• Washed Anaerobic: After depulping, beans are fermented without mucilage in oxygen-free conditions, resulting in clean yet vibrant profiles.
• Honey Anaerobic: Retaining part of the mucilage, this method combines the richness of honey processing with the complexity of anaerobic fermentation.
• Co-Fermentation: Exotic ingredients, such as fruits (pineapple, berries, mango, passion fruit,...), are added to the fermentation process to create innovative flavor notes.
• Varying Fermentation Times: Adjusting the fermentation duration—24, 48, or 72 hours—affects sweetness, acidity, and complexity.

Each method requires careful monitoring to ensure optimal results and prevent undesirable off-flavors, such as sourness or overripe notes.

Anaerobic fermentation impacts the chemical and physical properties of coffee beans in several ways:

• Aromatic Compounds: Enhanced development of esters, alcohols, and acids creates distinctive aromas and flavors.
• Appearance: Green beans often exhibit unique colors or surface textures due to fermentation byproducts.

Density and Structure: Fermented beans are denser, influencing heat absorption during roasting and requiring adjustments in roast profiles.

What does all this mean for a coffee roaster? Truth being said, fermented beans are very different from any other kinds and their behaviour during roasting is also significantly different. This is due to the physical and chemical changes that have occurred in the grain through the fermentation process. Experimentally processed beans present exciting opportunities but also challenges for roasters. Key considerations include:

• Heat Sensitivity: Fermented beans may scorch more easily due to higher sugar content and require gentler roasting curves.
• Flavor Preservation: Slow and controlled roasting helps preserve delicate fermentation-induced flavors.

Profile Customization: The roaster’s expertise is essential to highlight the unique attributes of anaerobically processed beans, such as acidity, body, and aromatic complexity.

Fermentation allows producers to unlock a wide range of sensory possibilities, offering:

• Enhanced Sweetness: Longer fermentation amplifies natural sugars.
• Distinctive Acidity: Tropical fruit notes like pineapple, mango, or passion fruit.
• Complex Aromatics: Floral, wine-like, or spiced aromas.
• Unique Textures: Creamy or yoghurt-like mouthfeel.

For consumers, this means a richer and more diverse coffee experience, often with flavors that traditional processing cannot achieve.

For coffee farmers, experimental processing offers an opportunity to increase revenue and differentiate their product. Benefits include:

• Higher Market Value: Uncommon flavor profiles command premium prices.
• Market Differentiation: Unique methods, such as co-fermentation or carbonic maceration, make coffees stand out.
• Sustainability: Methods like natural anaerobic fermentation use less water, which is crucial in resource-scarce regions.

By innovating with fermentation, producers not only improve their financial stability but also elevate the reputation of their region’s coffee on the global stage.

When you encounter a coffee labeled "anaerobic" or "fermented," you’re in for a sensory adventure. These coffees often:

• Offer bold and unexpected flavors.
• Highlight the artistry and expertise of producers and roasters.
• Come at a premium price, reflecting the intricate processes and limited availability.

At Farstad & Co, we believe every coffee tells a story. Experimentally processed beans are a testament to innovation, craftsmanship, and the endless possibilities of coffee. Whether you’re a seasoned enthusiast or just beginning your coffee journey, we invite you to explore these extraordinary flavors and discover your own favorites.