This year, we will be offering two Ethiopian Arabica varieties from the Yirgacheffe region for filter brewing. One is a "natural" coffee, the other a "washed" one. In a multi-part series for PRESSE, we will delve into the background of these processes and how they affect the coffee in your cup.
What happens to freshly harvested coffee cherries? Ideally, the beans inside the cherries are fully ripe after harvesting, but they are not yet ready for storage, transport, and roasting. This requires careful post-harvest processing, the so-called "post-harvest process." A great deal of energy and expertise is invested in this process to ensure roasters have a good raw material base for their roasting. After harvesting, the cherry and the two coffee beans inside it have a moisture content of up to 65%. For storability, the beans must be dried to a level of 10-12%. Various methods are used in coffee production for this. The two most common methods are the "natural" or "dry process" and the "washed" or "wet process." Other methods include the "honey process," "semi-washed," and various "anerobial processes."

Graphic: Structure of the coffee bean. 220GRAD
Why are there different methods? – There are several reasons. One very important factor is the prevailing weather during harvest, or more generally, the microclimate of the region. The "natural" process is generally used in regions with a dry climate during and after harvest. "Washed" coffees are often produced in areas with a humid microclimate.
The different methods influence the composition of the ingredients and thus ultimately the cup profile. However, the foundation remains the careful handling of the coffee plants and an eye for ripeness at harvest.
“I don’t believe in crazy experimental coffees. The post-harvest process can maintain the quality but not create it. For me, working on quality starts at the plantation.” This quote comes from coffee producer Teo Englhardt from Guatemala. The art of the post-harvest process lies in preserving the unique qualities of each coffee bean from the field into a dry, storable form. With “natural” or “dry processed” coffees, the coffee cherries are washed after harvesting, freed from foreign matter, and sorted according to ripeness.

Image: African Highbeds. Vietnam Coffee Origin Trip 2023
Afterward, the cherries are laid out on so-called "African beds" to dry. The advantage of these beds over concrete surfaces is that the cherries are also ventilated from below. The cherries are turned regularly to ensure even drying. The major challenge in drying lies in maintaining the correct pace. If the cherries remain moist for too long, they risk rotting, which negatively impacts the quality of the coffee. However, there is also the risk of drying too quickly. The Brazilian scientist Flavio Borém describes the damage caused by excessively rapid drying as the destruction of the coffee bean's cell structure, thus initiating bean death processes. In addition to sun-drying, the large quantities of coffee cherries in Brazil are also dried in drum dryers. Based on his observations, Flavio Borém has formulated the following formula for drying coffee in these processes: 13g of water per kilogram of coffee per hour at a temperature between 35 and 40°C. This drying rate best preserves the cell integrity of the coffee beans. The formula sounds simple, but in practice it requires a great deal of experience and knowledge of local conditions. The drying process takes between two and three weeks. Afterwards, the beans, along with the dried pulp, are taken to the mill.
Here, the pulp and parchment layer are removed, and the beans are sorted by density and size. Defective beans are discarded again. The green beans typically remain in a warehouse with a defined temperature and humidity for a while. Here, the beans "rest" to ensure they are at equilibrium for transport. It's important to remember that the life process is still ongoing in green coffee beans. Therefore, the storage and age of green coffee have a significant impact on the quality in the cup. Many hands and minds are involved before the beans reach their final stage of processing, and we should appreciate this with every good cup.