What is Fermented Coffee Processing?

Carbonic Maceration, Anaerobic Fermentation & Wine Yeast Fermentation

What is Coffee Processing?

Coffee processing encompasses the techniques employed to harvest, prepare, and convert raw coffee cherries into green coffee beans, ultimately destined for roasting. Diverse coffee processing methods exist, and each exerts a distinct influence on the final product, shaping the coffee's flavor profile. These methods wield considerable sway over the coffee's flavor, acidity, body, and overall characteristics.

Common coffee processing methods that have been around for a very long time include:

  • Dry (Natural) Processing 
  • Washed (Wet) Processing
  • Wet Hull (Giling Basah) Processing
  • Honey (Semi-Washed) Processing

To learn more about these methods, check out our this article:

Coffee Processing Methods Explained - Natural, Washed, Wet-Hulled & Honey

In recent years, the world of coffee processing has seen a surge in innovation, introducing novel methods that redefine the boundaries of flavor complexity. Three of these new techniques are:

  • Carbonic Maceration 
  • Anaerobic Fermentation
  • Wine Yeast Fermentation

These cutting-edge coffee processing methods involve controlled environments, specialized bacteria, and even wine yeast strains, offering coffee enthusiasts a glimpse into a realm of unique and intricate taste profiles.

Coffees produced via these methods are not always easy to track down. Luckily, Volcanica (one of our favorite roasters!) has a collection of Colombian beans produced by these experimental methods!

Let's take a closer look at these three new methods:


Carbonic Maceration Processed Coffee → What is Carbonic Maceration Processing?

Overview

Carbonic Maceration is a relatively modern and innovative coffee processing method that borrows techniques from winemaking.

This method involves using carbon dioxide (CO2) to control the fermentation process, resulting in unique and distinct flavor profiles. 

Process

Harvesting: Ripe coffee cherries are selectively harvested from the coffee plants. The cherries should be at their peak ripeness for optimal flavor development.

Preparation for Processing: The harvested cherries are sorted to remove any under ripe or overripe cherries. The selected cherries are then placed in airtight fermentation tanks.

Purge with Carbon Dioxide: The fermentation tanks are purged with carbon dioxide to create an anaerobic (oxygen-free) environment. This step helps to prevent the growth of aerobic bacteria and yeast, allowing for controlled fermentation.

Addition of Carbon Dioxide: Carbon dioxide is introduced into the tanks at a specific pressure. This controlled environment, often with added temperature controls, influences the fermentation process.

Fermentation: The cherries undergo a fermentation process inside the sealed tanks. Unlike traditional fermentation methods, Carbonic Maceration relies on the absence of oxygen and the influence of carbon dioxide to guide the fermentation. This process typically takes several days.

Monitoring and Control: Throughout the fermentation period, the process is closely monitored to control factors such as temperature, pressure, and the concentration of carbon dioxide. This precision allows for the manipulation of flavors in the final cup.

Drying: After the fermentation process is complete, the coffee cherries are removed from the tanks and dried. This can be done using various drying methods, such as sun drying on raised beds or mechanical drying.

Hulling and Sorting: Once the cherries are sufficiently dried, the outer layers (husk, pulp, and mucilage) are removed, revealing the green coffee beans. The beans may go through additional sorting and grading processes.

Resting: The green beans may undergo a resting period before being roasted. This allows the flavors to stabilize and develop further.

Flavor Profile

Carbonic Maceration coffees are known for their unique and complex flavor profiles. The controlled fermentation process can result in coffees with vibrant acidity, floral and fruity notes, and a distinct sweetness. The method allows for a high level of experimentation and the creation of innovative and specialty coffee offerings.

Recommendation

Colombian Milan Maypop

Roasted By: Volcanica Coffee

Carbonic Maceration Coffee

Roast: Light

Flavor Profile: Notes of pineapple, lemon, cocoa nibs, and myrrh


Anaerobic Fermentation Processed Coffee → What is Anaerobic Fermentation Processing?

Overview

Anaerobic fermentation is an innovative coffee processing method that involves fermenting coffee beans in an oxygen-free environment.

This controlled fermentation process aims to influence and enhance the flavor profile of the coffee. 

Process

Harvesting: Ripe coffee cherries are selectively harvested by hand. Only fully ripe cherries are chosen for processing to ensure optimal flavor development.

Depulping: The outer skin of the harvested cherries is mechanically removed, exposing the beans still covered in mucilage.

Transfer to Fermentation Vessels: The depulped beans, still covered in mucilage, are transferred to fermentation vessels. These vessels are sealed or flushed with inert gases to create an oxygen-free (anaerobic) environment.

Fermentation: The coffee beans undergo fermentation in the sealed or controlled environment. The absence of oxygen alters the fermentation process and influences the breakdown of sugars in the mucilage. Fermentation times can vary, and the process is closely monitored to achieve specific flavor outcomes.

Temperature Control: Temperature plays a crucial role in anaerobic fermentation. The fermentation vessels may be temperature-controlled to manage and influence the fermentation process. Some producers use cold fermentation for a longer period, while others may opt for a warmer fermentation environment.

Monitoring: Throughout the fermentation period, the process is closely monitored to ensure consistency and to prevent over-fermentation, which could negatively impact the coffee's flavor.

Drying: After the fermentation process is complete, the beans are typically dried. This can be done through various methods, including sun drying on raised beds or mechanical drying.

Hulling: Once the beans are sufficiently dried, the outer layers (husk, parchment, and dried mucilage) are mechanically or manually removed to reveal the green coffee beans.

Sorting and Grading: The green beans may undergo additional sorting and grading processes to remove any defective or undesirable beans.

Resting: The green beans may undergo a resting period before being roasted. This allows the flavors to stabilize and develop further.

Flavor Profile

Anaerobic fermentation is known to produce coffees with unique and complex flavor profiles. The controlled fermentation process can impart distinct fruity, floral, and wine-like notes to the coffee. Producers often experiment with different fermentation conditions to achieve specific and desired flavor outcomes.

Recommendation

Colombian Garden of Eden Orange Velvet Coffee

Roasted By: Volcanica Coffee

Anaerobic Fermentation Coffee

Roast: Light

Flavor Profile: Notes of maple syrup, red apple, caramel, vanilla, and white chocolate


Wine Yeast Fermentation Processed Coffee → What is Wine Yeast Fermentation Processing?

Overview

Wine yeast fermentation coffee processing is an experimental and innovative method that involves the use of wine yeast strains during the fermentation stage.

This approach aims to influence the flavor profile of coffee beans by introducing specific yeast varieties typically associated with wine fermentation. 

Process

Harvesting: Ripe coffee cherries are selectively handpicked from the coffee plants. Only fully ripe cherries are chosen for processing to ensure optimal flavor development.

Depulping: The outer skin of the harvested cherries is mechanically removed, exposing the beans still covered in mucilage.

Transfer to Fermentation Vessels: The depulped beans, still covered in mucilage, are transferred to fermentation vessels. In wine yeast processing, these vessels may be inoculated with specific wine yeast strains.

Fermentation: The coffee beans undergo fermentation in the vessels, and the introduced wine yeast strains play a crucial role in this process. The yeast consumes sugars in the mucilage, producing alcohol and influencing the coffee's flavor profile. This controlled fermentation process contributes to the unique characteristics of the coffee.

Temperature Control: Temperature is an essential factor in wine yeast fermentation. The fermentation vessels may be temperature-controlled to manage and influence the fermentation process. Different temperatures can yield varied flavor profiles.

Monitoring: The fermentation process is closely monitored to ensure consistency and to prevent over-fermentation, which could negatively impact the coffee's flavor.

Drying: After the fermentation process is complete, the beans are typically dried. This can be done through various methods, including sun drying on raised beds or mechanical drying.

Hulling: Once the beans are sufficiently dried, the outer layers (husk, parchment, and dried mucilage) are mechanically or manually removed to reveal the green coffee beans.

Sorting and Grading: The green beans may undergo additional sorting and grading processes to remove any defective or undesirable beans.

Resting: The green beans may undergo a resting period before being roasted. This allows the flavors to stabilize and develop further.

Flavor Profile

Wine yeast coffee processing is intended to impart wine-like characteristics to the coffee. Depending on the specific wine yeast strains used and fermentation conditions, the resulting coffee can exhibit fruity, floral, and even wine-like notes. The use of wine yeast introduces a layer of complexity to the flavor profile, creating a unique and distinctive cup of coffee.

Recommendation

Colombian Pradera Wine Yeast Coffee

Roasted By: Volcanica Coffee

Wine Yeast Fermentation Coffee

Roast: Light

Flavor Profile: Notes of passion fruit, pineapple, cocoa, and cugar cane


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