Comparing the Effects of Convective, Infrared and Combined Convective–Infrared Dryers on the Characteristics of the Dried Eucalyptus Leaves and Optimising the Drying Process With Response Surface Methodology

Despite the widespread use of eucalyptus leaves in pharmaceutical and food industries, optimising their drying process to preserve bioactive compounds while minimising energy consumption remains a critical challenge. This study systematically investigates the drying of eucalyptus leaves using convective, infrared and combined convective–infrared dryers under varying temperatures (40°C–60°C), air velocities (0.5–1.5 m/s) and infrared powers (700–1500 W), with experiments designed via response surface methodology (RSM) based on a central composite design (CCD). Results revealed that increasing temperature, air velocity and infrared power simultaneously reduced drying time (t) and energy consumption (E), while total phenolic compounds (TPC) and antioxidant activity (DPPH) initially increased to a peak before declining. Optimal conditions were identified as 53°C and 1.2 m/s (convective), 1397 W (infrared) and 48°C, 0.7 m/s and 1137 W (combined), achieving balanced outcomes for t , E , TPC and DPPH. These findings provide actionable insights for industrial‐scale drying processes, ensuring energy efficiency and maximal retention of bioactive compounds. Future research could explore hybrid drying techniques or scalability to other medicinal plants.