We use the term processing in coffee to describe the methods used to remove the seeds i.e. the green beans, from the coffee fruit, or cherry. At some stage during processing, the beans will need to be dried, and this opens up a whole range of options for producer.
The reasons for choosing a particular drying method can range from the simple to the complex. For some producers a wetter climate during the drying period necessitates the use of mechanical methods, while for others tradition dominates the way in which they work. Some producers are now experimenting with drying methods to produce better results which can ultimately result in a better price for their coffee.
The purpose of drying coffee is to lower its moisture content to a stable level, ready for shipping. Typically this would be around 9 – 12% moisture (the moisture content of the ripe cherry is 50-70%).
There are three basic methods for drying coffee, though each has many variations.
Patio drying is a very common method and involves spreading the beans on concrete patios. To ensure even drying the beans will need to be turned
regularly. Washed coffees are drying dried for around 6-7 days while natural coffees take around a fortnight. On some farms the coffee will be raked together and covered overnight to protect from moisture. On other farms the patios will be located to ensure they are shaded during the hottest part of the day. Where space is at a premium we have even seen patios located on the roof of the farmhouse!
Often called African beds, this method of drying is often used where there is a risk of rainfall during the drying period. Raised beds allow air to circulate under the coffee often resulting in a more even drying. Coffee dried or raised beds still needs to be turned regularly and the beds are often built at waist height to allow the beans to be sorted/ inspected throughout the drying period.
It takes between 10 and 28 days for coffee to dry on raised beds.
RAISED BED VARIATIONS
SHADE: some producers choose to cover their raised beds with some form of roofing, keeping them open at the sides. This allows them to control the amount of sunshine to which the beans are exposed.
PARABOLIC: similar to shade, parabolic beds are covered in plastic tunnels. This allows light in but protects the beans from rainfall. These types of structures are popular where there is more rainfall during the drying period.
STACKED BEDS: for some producers space is a premium, particularly if they are located on steep hillsides! Beds can be stacked to create multi-level drying platforms. Each level will be exposed to differing amounts of sunlight so coffee is often moved around during the drying period.
Mechanical dryers are essentially huge tumble dryers which speed up the drying process. They are often used where the climate prevent other methods from being used, or where large volumes of coffee need drying. Mechanical dryers can reduce the drying time down to 2-3 days. Traditionally these dryers can be costly to run and some believe they deteriorate the quality of the coffee. In many instances mechanical dryers will be used in conjunction with other methods.
Who would have thought that the simple process of drying coffee could be so varied and complex. It is one of the many factors which makes the world of coffee so interesting. Everyone is trying to achieve a stable 9-12% moisture level but how this is achieved varies from producer to producer. Many farms and mills are now experimenting with drying methods to achieve even better outcomes.