Integrated Multi – Response Optimization of Direct – Heat Rotary Drying for Palm Sugar: Drying Performance and Physicochemical Quality

This study aims to optimize palm sugar rotary drying using Response Surface Methodology and Central Composite Design, with inlet temperature (50–70 °C), air velocity (1.0–2.0 ms−1), drum speed (4–6 rpm), and mass (3–5 kg). Responses were drying rate, efficiency, yield, moisture content, reducing sugar, and browning index. Second-order models fit well (R2 = 0.83–0.94) with non-significant lack of fit. Temperature affected moisture, drying rate, and yield (p < 0.0001); drum speed affected all responses (p ≤ 0.0205), while mass and velocity affected selected responses (p ≤ 0.0114). Optimization minimized moisture, reducing sugar, browning, and yield while maximizing drying rate and efficiency. Optimum conditions were 73°C, 1.5 ms−1, 4 rpm, and 6 kg, yielding 1.326% (wb) moisture, 4.613% reducing sugar, 18.71 browning index, 3.63% h−1 drying rate, 18.79% efficiency, and 96.45% yield. Validation errors were <10%, supported by SEM. The process balanced drying performance and physicochemical quality, supporting pilot-scale development and further scale-up.