Preliminary study of drying of natural coffee by cyclical pressure changes

Abstract A “special coffee” is obtained with an adequate drying process, which allows the preservation of volatile substances responsible for excellent cup quality. The aim was to carry out preliminary studies of drying of natural coffee by implementing a Cyclic Pressure Changes (CPCD) dryer, comparing it with solar drying and with a mechanical drying system by forced convection of low-temperature air. The drying times and rates of the systems used were compared, as well as the respective valuation of the cup quality. Drying times were 767 h for solar drying system, without reaching the desired moisture content; 153.5 h for mechanical drying system and 449 h for the CPCD system. However, the global cup tests showed a better quality of the grain obtained with the CPCD system (87 points), than the one obtained with the mechanical drying at 35°C (84 points).