The Effect of Variations in Drying Room Temperature on a Rotary Dryer with a 5 rpm Cylinder Rotation on Changes in Mass and Water Content of Coffee Beans

Abstract

Drying is a critical stage in post-harvest handling of coffee that directly affects the final quality and shelf life. This study aims to analyze the performance of a horizontal cylindrical rotary dryer at various drying chamber temperatures (40°C, 50°C, 60°C, and 70°C) on two main parameters: moisture content and mass of coffee beans. The method used is experimental with robusta coffee bean samples dried in a laboratory-scale rotary dryer unit. Data collection was carried out every 30 minutes until reaching a drying time of 360 minutes. The results showed that drying temperature significantly affected the reduction in moisture content and mass. At a temperature of 70°C, coffee beans reached the lowest final moisture content of 28% within 360 minutes, followed by temperatures of 60°C (29%), 50°C (50%), and 40°C (50%). Higher temperatures (60°C and 70°C) also result in a much faster mass loss than lower temperatures (40°C and 50°C), where the final mass at 360 minutes for a temperature of 70°C is 2600 grams, while at 40°C it is still 3600 grams. However, increasing the temperature needs to be carefully considered to avoid thermal damage to the beans that can reduce quality. A temperature of 60°C provides the optimal combination of drying time efficiency and the potential to maintain coffee bean quality in a horizontal rotary cylinder dryer system.