COFFEE PROCESSING OVERVIEW

August 29, 2024 • Drew Horton

The Importance of Coffee Processing: Unlocking the Flavors in Your Cup

When you enjoy a cup of coffee, the rich and complex flavors you taste are not just a result of the terroir where the coffee was grown, the variety of the coffee, and how it is roasted, but also how they are processed.

 

Coffee processing is a crucial step that significantly influences the final taste, aroma, and quality of your brew. Understanding the different processing methods allows you to appreciate the intricate journey from coffee cherry to cup and helps you select coffees that align with your taste preferences. Below, we'll dive into some of the most common and innovative coffee processing methods, each contributing uniquely to the coffee's flavor profile.

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Washed (Wet Process)

The washed process is a meticulous and water-intensive method that emphasizes the intrinsic qualities of the coffee bean, often resulting in a cleaner, more acidic, and vibrant cup profile. Washed coffees Here's a closer look at how it works:

  • Harvesting and Sorting: Ripe coffee cherries are selectively harvested by hand or machine and then sorted by size and density using water channels. Floated cherries, often underripe or defective, are discarded.
  • Depulping: The sorted cherries are de-pulped, removing the outer skin and most of the mucilage using a de-pulping machine. The beans, still covered in a thin mucilage layer, are then transferred to fermentation tanks.
  • Fermentation: Depending on environmental factors, beans may be left to ferment in these tanks for 12 to 72 hours. Fermentation allows natural enzymes to break down the remaining mucilage, though this step is optional.
  • Washing: After fermentation (if performed), the beans are thoroughly washed to remove any remaining mucilage, ensuring a clean and bright flavor profile.
  • Drying: The washed beans are spread out to dry on raised beds or patios, a process that can take up to 15 days.
  • Hulling and Storage: Once dried to a moisture content of 10-12%, the beans are hulled to remove the parchment layer and stored until ready for export or roasting.

Flavor Profile:

Coffees processed using the wet method are often characterized by bright acidity, a clean and balanced flavor profile, and a lighter body, highlighting the origin's terroir.

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Natural (Dry Process)

The natural process is a more traditional and less water-dependent method where the entire cherry is dried, leading to unique and intense flavor profiles:

  • Harvesting: Ripe cherries are selectively harvested, with the sorting process being crucial due to the direct influence of the fruit on the beans.
  • Drying: Whole cherries are spread out in thin layers on raised beds, patios, or concrete surfaces to dry in the sun, a process that can take 2 to 4 weeks.
  • Monitoring: The drying process requires careful monitoring to avoid mold growth or over-fermentation, especially in regions with variable weather.
  • Hulling: Once fully dried, the cherries are mechanically hulled to remove the dried skin and pulp, revealing the green beans.

Flavor Profile:

Natural processed coffees often exhibit fruit-forward flavors, with notes of berries and tropical fruits, along with a heavier body. The fermentation within the cherry during drying can impart a wine-like or jammy character to the coffee.

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Anaerobic Fermentation

Anaerobic fermentation is an advanced method that allows producers to exert more control over the fermentation process, resulting in coffees with distinct and often experimental flavor profiles:

  • Harvesting: Cherries are selectively harvested and placed into airtight fermentation tanks, either whole or after de-pulping.
  • Fermentation: In the absence of oxygen, anaerobic bacteria break down the sugars and mucilage, with producers adjusting conditions like temperature, time, and pressure to influence flavor.
  • Post-Fermentation: After fermentation, the beans are dried naturally or using other methods, depending on the desired outcome.

Flavor Profile:

Anaerobic fermentation can lead to intensely flavorful coffee, with pronounced acidity, unique fruitiness, and complex, sometimes savory notes.

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Carbonic Maceration

Carbonic maceration is a technique adapted from the wine industry, where whole cherries undergo fermentation in a carbon dioxide-rich environment:

  • Harvesting and Sealing: Whole cherries are placed in a sealed fermentation tank, which is then filled with carbon dioxide, creating an anaerobic environment.
  • Internal Fermentation: The process initiates an internal fermentation within the cherry, allowing unique flavor development.
  • Fermentation Duration: Typically ranging from a few hours to several days, this process is meticulously controlled.
  • Drying and Hulling: After fermentation, the cherries are dried and hulled to extract the green beans.

Flavor Profile:

Coffees processed using carbonic maceration are often highly aromatic, with pronounced fruity, floral, and wine-like notes. The technique tends to produce a clean, structured cup with vibrant acidity.

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Lesser-Known Processes

Acetic Process

Fermenting coffee in an oxygen-rich environment encourages acetic acid bacteria growth, resulting in fruity or floral notes at low concentrations, but potentially sour at higher levels.

Bio-Innovation

A proprietary process utilizing low-oxygen fermentation in clay pots to capture and enhance native yeast populations.

[Color]-Washed:

Washing pulped coffee with macerated cherry juice instead of water to preserve flavor intensity.

Cascara Tea

Fermenting coffee in tea made from coffee skins, adding complexity to the coffee's acidity.

Cryomaceration

A cold fermentation process enhancing flavor by placing cherries in very cold water for extended periods.

Flower Cultured

Inoculating coffee with a starter culture grown from coffee blossoms for distinct floral notes.

High Gravity

Fermentation under vacuum conditions accelerates the process, ensuring consistent moisture and metabolite distribution.

IPA Anaerobic

Combines anaerobic fermentation with IPA yeast and hops for a distinct bitterness and tropical flavor.

Koji

Applying koji mold to cherries or parchment to enhance body and sweetness.

Kombucha

Using a SCOBY to inoculate coffee during fermentation, introducing unique kombucha-like flavors.

Lactic

Promoting lactic acid bacteria in a low-oxygen environment for controlled fermentation and distinctive lactic acidity.

Molecular

Fermentation in a closed container with a starter culture grown from the farm's coffee cherries.

Natural-Hydro-Honey

A multi-step process combining natural, hydro, and honey processing methods.

Thermal Shock

Involves washing fermented coffee with hot and then cold water, influencing the final flavor.

Thermal Stroke

Combines low-oxygen fermentation and high-temperature drying to create unique flavor profiles.

Tree-Dried

Cherries are left to ripen and dry on the tree, resulting in a raisin-like flavor but with high risk and minimal quality benefits.

Yeast

Introducing selected yeast strains during fermentation to control flavor outcomes.

Yogurt

A variation of the lactic process using yogurt cultures to enhance acidity and body.

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Conclusion

The processing method plays a pivotal role in shaping the final flavor profile of your coffee. From the traditional wet and dry processes to the more experimental anaerobic fermentation and carbonic maceration, these techniques offer a wide array of flavor possibilities. Understanding these methods not only enhances your appreciation for the art of coffee-making but also guides you in selecting the coffee that best suits your taste preferences. As innovation continues in the coffee industry, we can look forward to even more diverse and exciting flavor experiences in the future.

 

For those interested in a more in-depth exploration of these coffee processes, please refer to Christopher Feran’s comprehensive glossary of coffee processes that i used as a refernce, available here.