How does washed coffee processing differ from double washed?

Washed coffee processing, also called the wet process, removes the outer skin and mucilage from green coffee beans before the seeds are dried, which gives the cup its notable cleanliness. The method began in the West Indies in the 19th century and developed in Jamaica, where it was known as the West Indian process and suited humid, rainy regions.

As specialty coffee grew, producers added labels such as double washed, K72 washed, and dry fermentation washed to highlight traceability and selling points. These variants differ mainly in how the fermentation stage is handled and repeated, and that stage shapes the acidity and sweetness in the finished cup. Front Street Coffee draws on its own production experience to explain those differences.

As the most classic method of processing green coffee beans, the washed method has won the favor of many coffee enthusiasts with its outstanding cleanliness. With the development of specialty coffee, new names such as double washed, K72 washed, and dry fermentation washed have emerged on the market. How exactly do they differ from conventional washed? This article will start from the historical origins of the traditional wet process and gradually break down the operational procedures and flavor characteristics of these derived techniques to help you clarify the logic behind different washed methods. Front Street Coffee will also combine its own production experience to help you understand how the fermentation stage shapes the acidity and sweetness of a cup of coffee.

The washed method is one of the most traditional and also most common methods of processing green coffee beans. The process of depulping and washing not only greatly improves production quality, but also gives the coffee in the cup good cleanliness, making it a green bean processing form favored by countless coffee enthusiasts, including Front Street Coffee, of course.

With the gradual popularization of specialty coffee, more and more consumers have begun to pay attention to the traceability information of single-origin coffee. Therefore, in order to highlight certain selling points, many producers add prefixes and modifiers to the names of processing methods, such as "double washed method," "K72 washed method," "dry fermentation washed method," and so on. So how are they different from conventional washed?

Before understanding these "new-style" processing methods, Front Street Coffee believes it is necessary to first sort out the origins of traditional washed processing for everyone.

Washed Method

Also called the wet process, translated from "Wet Process," it is a method of obtaining processed green beans by removing the outer skin and mucilage before the seeds are dried.

According to the relevant materials consulted by Front Street Coffee, this wet process began in the West Indies in the 19th century and developed in Jamaica. At that time it was called WIP (West Indian process), and it was mainly suitable for humid and rainy regions. Corresponding to it was OIB (Oost Indische Bereiding, or East Indies preparation), which referred to traditional natural sun-drying.

Before the 1850s, people processed coffee cherries using the oldest natural sun-drying method. Only with the arrival of the Industrial Revolution did this "first depulping" coffee processing technology appear. In the mid-19th century, Jamaica became one of the world's largest coffee-producing countries, producing about 70,000 tons of green beans each year. Because this place has an island-type climate, the cherries are not easy to dry, so natural sun-drying was not very advantageous on this land.

In 1845, the invention of the world's first coffee pulper machine was patented by James Meacock from Kingston, Jamaica. This was a machine used to peel off the outer skin of coffee cherries and also to sort coffee. In this way, more and more inventions related to coffee pulpers were born one after another, and the washed method was officially applied to coffee production.

The steps of the traditional wet process are not complicated: flotation → depulping → fermentation → washing → drying → hulling → packaging. However, its implementation requires an ample supply of water, and because it relies heavily on mechanical assistance, producers who adopt washed processing must also have sufficient funds to invest in purchasing machinery. The rise of the washed method happened to coincide with the early American plantations built by capital, which had enough operating funds, and together with the invention of various pulpers/hullers created in response to the needs of the times, this drove the spread of the washed method throughout the Americas.

Double Washed

The original wet process washed the fermented coffee beans once with clean water, rinsed off the mucilage, and then sent them directly to the drying yard to dry and be packed. But in Kenya, after one round of washing, the coffee is soaked again in a pool of clean water, then taken out and washed again before being sent to the drying yard for dehydration.

The reason Kenya initially changed conventional washed processing into "secondary soaking" was actually not to pursue flavor, but because the local drying yards were insufficient. Kenya is a typical cooperative operation model in Africa. During every harvest season, smallholders bring the cherries they pick to the processing factory all day long. The depulping and fermentation steps are relatively simple and not time-consuming, but drying each batch of fermented beans takes at least 5 to 7 days. Sometimes, when the volume to be processed is too large, there will be no place to dry the washed beans. So people had no choice but to pour the wet beans back into the pool and let them "cool off" first to avoid spoilage or contamination, until the drying yard was emptied and they could be scooped out.

This form of washed processing with a second soaking is called "Double Washed," and in producing regions it is also called "Fully Washed," "Double Fermentation," and so on, meaning fully washed. Because Kenya was the earliest region where this processing method became popular, this type of washed processing is also called "Kenyan Process." Later, people discovered that this twice-fermented washed coffee, adapted to local conditions, not only helped stabilize quality control in production, but also brought coffee a layered, rich fruity acidity. Today, coffee produced by some American estates also uses this Kenyan-style washed processing.

K72 Washed Method

That is, the Kenyan 72-hour washed processing method, which can be understood as an additional extension of ordinary washed and double washed.

This washed procedure emphasizes control of fermentation time. First, it undergoes 24 hours of washed fermentation, then the detached mucilage is cleaned off, and it is fermented for another 24 hours in a clean tank. Next, the remaining components are cleaned off again, and it is introduced into a trough filled with clean water for the final 24 hours of fermentation, totaling 72 hours. This technique also gives Kenyan coffee a bright and clean high-quality fruity acidity. The Azalia that Front Street Coffee produces daily uses exactly this washed technique, giving the brewed coffee an acidity like cherry tomatoes and smoked plums.

Dry Fermentation (Washed) Method

Because the original wet process requires the use of large amounts of pure water, and the wastewater after fermentation has already become acidified, discharging it into rivers or soil will have an impact on the ecological environment. Therefore, also in response to environmental protection and to save water resources, the more water-saving dry fermentation washed method began to be advocated.

So-called "dry fermentation" means that after removing the fruit skin, the parchment beans are poured directly into a fermentation tank and left to rest, maintained for about 6 to 8 hours. This step is actually very similar to the honey processing that everyone is more familiar with. The difference is that after dry fermentation is completed, the coffee still needs to be rinsed once with water to completely remove the sticky substances that have broken down and fallen off. In terms of flavor, conventional washed coffee often has a brighter mouthfeel, while dry-fermented washed coffee usually has a rounder sweetness than wet-processed coffee (because it is similar to honey processing).

It is not difficult to find that fermentation is an essential step in washed processing, so no matter which washed method it is, the difference is ultimately just the soaking time and number of times during fermentation, whether it is high temperature or low temperature, aerobic or anaerobic, and whether any additional additives are involved, and so on.

- END - FrontStreet Coffee

No. 10, Baoqian Street, Yandun Road, Dongshankou, Yuexiu District, Guangzhou City, Guangdong Province

The above content is compiled by CoffeeHunters, a coffee news website.