Effect of Bean Size and Moisture Content on the Physical and Aerodynamic Characteristics of Gayo Coffee

This study evaluated the physical and aerodynamic characteristics of Gayo Arabica and Robusta coffee beans as influenced by bean diameter and moisture content. Samples from the Gayo Highlands (900–1,700 m above sea level) were arranged in a Completely Randomized Design with two factors: diameter (<6 mm, 6–7 mm, >7 mm) and moisture content (10–15%), with three replications. Parameters measured included sphericity, mass per 100 beans, bulk and true density, porosity, terminal velocity, and drag coefficient. ANOVA and Duncan’s test (95%) were applied for statistical analysis. Bean diameter significantly affected most properties, with larger beans showing higher mass, sphericity, porosity, and terminal velocity but lower bulk density and drag coefficient. Moisture content significantly influenced mass, true density, bulk density, and aerodynamic behavior; higher moisture increased mass and terminal velocity while reducing porosity and drag coefficient. True density was unaffected by diameter. Overall, diameter governed structural, while moisture content mainly modified mass-related and aerodynamic responses.