The coffee drying process is paramount, for a successful coffee operation. No matter which drying method selected, attentiveness and timing are key. Yet, the best way to dry coffee is open to debate.
Whether the coffee cherries are washed or unwashed during the processing phase, they still need to be dried accordingly. Each coffee bean must reduce its moisture content from around 60% to to 10 -12%, in order to develop quality flavour profiles for the end consumer.
It’s often argued that the lengthier (or slower) the drying time, the more complex the cup. However, as it happens, there are various coffee drying methods which can influence the final flavour result.
How is coffee dried?
Historically, coffee will have been left out to dry, on an open earth surface, underneath the baking sun. However, more recently, modern methods have been spawned to enhance drying times and flavours.
Results will have differed over the years, and trial and error will have majorly influenced the variety of coffee drying methods we witness today.
Depending on the origin, the farmer, and the requests of the buyer, coffee drying can be as complex as you make it but it’s often a balance of affordability and practicality.
Key factors also include: humidity, stirring, airflow and the avoidance of additional water.
What are the methods for drying coffee?
Coffee drying has taken on many formats, from traditional patio and terrace drying to hybrid mechanical dryers. The structure and location of these facilities has a great influence on their performance.
For instance, the surface on which the coffee is dried can impact upon the final flavour. Therefore, farmers have grown to be experimental with cement, brick, bamboo mats, asphalt and wood as they look to harness certain flavour attributes to their regions.
Raised tables with wire mesh, or other technologies that allow for a rapid and convenient method of protection from rain, are found in regions where showers are frequent during harvest. Movable roofs, movable floors or plastic tarpaulins are also employed, in this regard.
Farmers are heavily reliant on the weather in their region, readily available labour and affordable technology, to determine the best outcomes for their coffee.
A lot of Colombian farmers relied on Elbas for drying their coffee. An Elba is basically the flat roof of a house (usually the farmer’s own premises). This coffee drying method guarantees direct sunlight, is convenient for ease of maintenance and adds an element of security. The downfall is the exposure to rain and morning dew. To combat this, moveable parts were engineered with steel and corrugated panels, protecting the coffee from any downpour.
Compacted earth is widely used across the globe as a method for drying coffee but it does have its obvious flaws. For one, it generally takes longer, especially if there’s rainfall. Contamination is also another risk farmers face. Despite this, coffee buyers are requesting soil dried coffee, as a route to more earthy flavour notes which consumers seem to enjoy.
Similar to Elbas, patios and terraces are widely available and easy to access. However, maintenance can be tricky. The coffee cherries must be turned frequently and raked, to prevent bacterial damage. With a thick layer of coffee, stirring and raking needs to occur at least four times each day. Space to spread the harvest to a thinner layer is a major constraint, as well as nature’s elements.
Raised beds (drying tables) are mainly used in areas with rainfall occurring throughout the drying period. The elevation allows for air to circulate and moisture to drain away, quickening the overall drying process. Although this protects the coffee from showers and floods, the wood they’re built with is expensive and open to rot, fungi and termites. Also, poorly maintained beds can sag under the weight of coffee, creating uneven layers and inconsistent drying speeds.
An obvious and cheap way to avoid rainfall is a plastic tarp. Not only will this protect the coffee from rainfall up top, it prevents contact with the soil below too. However, condensation is likely to occur, accumulating liquid water. This can evaporate in the hotter, upper regions of the layered coffee but will it condense elsewhere.
Today, there are variations of mechanical coffee dryers available. Some require electrical power and energy to power fans and trommels, making them costly and tricky to install in coffee growing environments. Essentially, huge tumble dryers speed up the entire coffee drying process. Although these modern methods are quick, they can be unreliable when it comes to an evenly dried batch of coffee. There are cheaper machines available that do not require such power or labour and utilise natural convection to transfer heat.
There’s no doubt that the drying stage in coffee processing is of critical importance for delivering the characteristics of the coffee itself. It’s probably due to this reason that the best method for drying coffee cannot be determined.
The end-user now dictates the type of coffee they prefer and this is often an educated pallet searching for a unique flavour. This means, coffee producers are more willing to go to extreme lengths of experimentation to yield the most unusual results.
Finally, the origin has to be taken into consideration. Some regions benefit from flat lands that can cater for heavy machinery whereas other, more mountainous regions do not have the structures in place. Each climate plays its part too. As does the economical side of things with labour and cost of materials playing their part.