African beds are wooden structures built up off the ground in which coffee cherries or beans can be dried with good air circulation. This is important to prevent mould.
For example, to “naturally” process a coffee, the entire cherry is dried in a raised African bed. This allows for a lengthy fermentation period during which fructose is absorbed into the beans, yielding an intense tasting coffee.
For washed coffees, where the fruit flesh has been “washed” away, producers run the risk of over-drying the coffee. The moisture content of the beans therefore needs to be constantly measured. This can be controlled by covering the beds with nets or tarps, making the drying process slower and more consistent in the shade. Too dry beans are brittle and could break later in the process, which would count as a defect. This would decrease the value of the crop, or, in the worst case, these beans might not be useable at all.