Abstract
The drying process is the key to the quality of the coffee produced. The allowable moisture content of coffee beans is 12%. The air mass flux, specific humidity, and the drying temperature are varied using a bed dryer drying system combined with a double condenser refrigeration system. Robusta coffee beans are used in this research to obtain the characterization of coffee beans. The highest drying rate constant is obtained by 2.44 × 10-4 s-1 directly proportional to the increased air mass flux and drying air temperature, with a value of 1.701 kg/s m2 and 80 °C, but inversely proportional to the specific humidity, with a value of 7.01 g/kg d.a. The lowest activation energy value was 31.88 kJ/mol when the air mass flux was 1.701 kg/s m2, the drying air temperature was 80 °C, and the average specific humidity was 7.01 g/kg d.a. In this work, the developed correlation is proposed to practically predict the activation energy (EA) and the pre-exponential factor (A) with equation and respectively. Based on Ea and A correlation equation, it can be used for designing a bed dryer type coffee drying system for a larger scale.
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