Coffee processing: From pulp to bean

The Art of Coffee Processing: From Pulp to Bean

The processing of coffee beans is a crucial step on the journey from coffee cherry to finished bean. The choice of processing method not only influences the taste and quality of the coffee but also shapes the distinctive aromas we enjoy in every cup. Join us as we explore the different methods, their significance, and their impact on the coffee you drink.

After the harvest of the coffee cherries begins a fascinating and complex process: the processing of the beans. This step plays a decisive role in determining which aromas and flavor profiles will develop in the beans. Processing methods are diverse, ranging from traditional dry processing to innovative techniques used by specialized coffee farmers. But which method suits which coffee? How long does fermentation take, and what’s the story behind the mysterious silver skin? In this article, we dive deep into the world of coffee processing and explain how this process shapes the flavor of your coffee.

Wet and Dry Processing: The Fundamental Methods

The processing of coffee beans begins immediately after harvest and is one of the most important decisions a coffee farmer has to make. There are two main methods: wet (washed) and dry (natural) processing.

In wet processing, the pulp of the coffee cherry is mechanically removed right after harvest, and the beans are then fermented in water. This fermentation process, which can last between 12 and 72 hours, ensures that the remaining fruit mucilage is broken down and separated from the beans. After fermentation, the beans are washed and then dried. This method produces a clean and clear flavor profile, allowing the distinctive characteristics of the bean to stand out more prominently.

Dry processing, on the other hand, leaves the coffee cherries to dry whole after harvest, either in the sun or in mechanical dryers. During this process, the pulp remains in contact with the beans, leading to a fruitier and fuller-bodied flavor. This method is often used in regions where water is scarce. However, dry processing requires more patience and skill, as the cherries must be turned regularly to ensure even drying and to prevent mold formation.

The Impact of Processing on Quality and Flavor

The choice of processing method has a direct impact on the quality and flavor profile of the coffee. 

With wet processing, the result is often a clear, complex cup with lively acidity, which shines particularly well in lighter roasts. Coffees processed this way are ideal for those who prefer the pure taste of the bean without dominant fruity or earthy notes.

Dry processing, on the other hand, emphasizes the fruity and sweet notes of coffee. This method produces a more intense, full-bodied coffee with a rich flavor profile. Because the pulp stays in contact with the bean throughout drying, it often leads to flavors reminiscent of berries, dried fruits, or even chocolate.

The Role of Fermentation: Time and Technique

Fermentation is a crucial step in wet processing. During this phase, microorganisms break down the pulp that still clings to the beans.

The length of fermentation varies depending on climate, altitude, and the desired flavor profile, but it can last anywhere from 12 to 72 hours. However, if fermentation goes on too long, it can lead to undesirable flavors, which is why careful monitoring of this process is essential.

Specialty coffees often benefit from carefully controlled fermentation, which enhances the beans’ natural aromas. Some innovative coffee farmers even experiment with extended fermentation times or different fermentation techniques to create unique flavor profiles.

Modern Processing Methods: Innovations for Specialty Coffee

While wet and dry processing are the most common methods, newer techniques are also being used, especially for specialty coffees. 

One such method is honey processing, a hybrid of wet and dry processing. In this process, part of the pulp is removed from the cherry, and the beans are dried with some of the mucilage still attached. Depending on how much pulp remains on the bean, the process is referred to as White, Yellow, Red, or Black Honey. This method produces complex flavors that highlight both fruity and sweet notes.

The Silver Skin: What It Is and Why It Matters

The silver skin is a thin layer that surrounds the coffee bean and often remains attached even after processing.

During drying and storage up until shipping from the country of origin, the silver skin acts as a natural barrier against moisture, mold, and pests. It protects the bean from external factors that could compromise its quality.

Can You See the Difference After Roasting Between Wet and Dry Processing?

After roasting, experienced coffee roasters and tasters can detect differences that stem from the type of processing (wet or dry). These differences are mainly expressed in the flavor and texture of the beans.

Flavor Differences:

• Wet Processing (Washed): Coffees processed using the wet method tend to taste cleaner, fruitier, and more acidic. They often have a clearer flavor structure and less body compared to dry-processed beans.
• Dry Processing (Natural): These coffees tend to be heavier and fuller-bodied, with more intense, often sweeter and fruitier notes. They can also exhibit a more “earthy” flavor, which is less common in wet-processed beans.

Visual and Tactile Differences:

• Wet Processing: The beans are generally more uniform and lighter in color, with a smoother surface.
• Dry Processing: The beans can be less uniform in color, often darker, and sometimes with small residues of pulp or pectin, giving them a slightly rougher appearance.

While these differences are visible and perceptible to professionals, they can be more difficult for the average coffee drinker to identify without a focused tasting.

Ultimately, understanding the different processing methods and their impact on coffee contributes significantly to appreciating the complexity of the coffee world. Each method comes with its own challenges but also brings unique flavor profiles that add to the charm and diversity of coffee.