Coffee Bean Processing Methods: A Step-by-Step Guide and Flavor Differences Between Natural, Washed, and Honey Processing

From the perspective of specialty coffee today, we can distinguish between washed and natural processed coffee beans based on their flavor profiles. Under normal circumstances, washed processed coffee exhibits a cleaner profile with more pronounced acidity, while natural processed coffee showcases more distinct fermented sweetness and richer, more complex textural layers.

Given this, today we can choose coffee beans that suit our personal taste preferences. But why do different processing methods result in different coffee flavors?

This turns out to be related to the fermenting substances involved in coffee processing. As FrontStreet Coffee shared in previous articles about processing methods, the structure of a coffee cherry can be divided into skin, pulp, mucilage, parchment, silver skin, and seeds (coffee beans).

Natural processing involves directly drying fresh coffee cherries. During this 3-4 week drying process, the entire coffee cherry participates in fermentation, allowing the coffee beans to absorb sugars from the mucilage layer and pulp, resulting in a sweeter flavor expression in the coffee.

Washed processing involves removing the skin from fresh coffee cherries, then placing them in fermentation tanks for stirring and soaking for 36 hours to separate the mucilage layer, followed by thorough rinsing with clean water before drying. During most of the drying time, only the coffee beans themselves participate in fermentation. With fewer fermenting substances, the coffee appears cleaner and simultaneously expresses more acidic flavors (in light roasts).

Visually, we can also clearly distinguish between washed and natural beans. In their raw state, washed beans tend to be light green in color, while natural beans appear pale yellow. In their roasted state, washed beans display a "white center line," whereas natural beans do not.

The Historical Origins of Coffee Processing Methods

In reality, when these processing methods were first developed, flavor was not the primary objective. The most ancient coffee processing method is traditional natural processing - simply placing fresh coffee cherries in courtyards or on rooftops for sun drying. This method required minimal cost and could be done by anyone.

However, problems soon emerged: it was entirely dependent on weather conditions. In regions with unstable weather, mold and rot could easily develop, and the sugar-rich pulp was extremely attractive to insects, making it difficult to guarantee the quality of natural processed coffee. Before Ethiopia's coffee system reforms, naturally processed coffee beans could only achieve a maximum grade of G3.

Washed processing emerged as a product of industrial standardization. Faced with the poor quality and inconsistency of natural processing, standardized production was needed to achieve greater efficiency. In 1740, the Dutch, who controlled colonial coffee cultivation and global coffee trade, began using the washed method to process coffee beans. They initially discovered in the West Indies that soaking peeled coffee beans in water could remove the sticky mucilage layer, reducing drying time and effectively preventing pest and fungal infections. Consequently, washed beans became a symbol of high quality during that period.

Later, the invention of the coffee pulping machine in 1844 also made washed processing more efficient. However, washed processing is very costly, requiring large amounts of water - on average, 200 kilograms of green coffee beans consume 10-20 tons of water. Therefore, processing plants could only be established near water sources. It could be said that the emergence of washed processing was driven more by considerations of yield rate, production volume, and product standardization rather than flavor profile, which played only a minor role.

Adaptation and Innovation in Processing Methods

However, washed processing is not universally applicable. In countries with underdeveloped water resources, such as the mountainous regions of Costa Rica and the highland areas of Brazil, adaptive methods like honey processing and semi-natural processing emerged. In Indonesia's humid regions, wet-hulling processing developed. These methods were all invented to suit local conditions and achieve high yields and good quality rates, while indeed incorporating unique flavors imparted by the processing methods.

From the introduction of the specialty coffee concept in the 1970s to the present, processing methods have continuously been researched for flavor development. For example, renowned farms like Hacienda La Palmira and Hacienda El Roble, Paradise Farms, and 90+ Plus are dedicated to researching new processing techniques to uncover different flavor profiles in coffee beans.

Natural processing has also continuously improved. For instance, using African raised beds for natural drying helps avoid pest infestations and ground contamination. Shade cloths are used to control the degree of sun exposure. Enhanced personnel management includes turning coffee cherries regularly and sorting out defective coffee cherries, among other improvements.

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