Optimization of dehumidified cold air drying process on antioxidant activity and physicochemical properties of marungga leaf powder ( Moringa oleifera ) using response surface methodology

Moringa leaves contain valuable antioxidant-rich bioactive compounds, yet these compounds are easily degraded by heat during drying. This study aimed to optimize a low-temperature drying method using dehumidified cold air to better preserve antioxidant stability while improving the physicochemical quality of moringa leaf powder. Optimization was performed using Response Surface Methodology with a Central Composite Design, involving two variables—drying temperature (35–45 °C) and time (4–6 hours). The responses evaluated included moisture content, yield, antioxidant activity, total flavonoids, protein content, solubility, and color. The model predicted optimal conditions at 37.75 °C for 4 hours, yielding moisture content of 10.418%, yield of 31.192%, antioxidant activity of 88.321%, total flavonoids of 44.281 mg GAE/g extract, protein content of 25.44%, solubility of 14.7%, and color value (a*) of 52.00 with SMER value of 0.73 kg/kWh. Both temperature and duration significantly affected most parameters (p < 0.05). The findings indicate that dehumidified cold air drying effectively maintains phytochemical stability and enhances the functional quality of moringa leaf powder, offering a promising approach for processing heat-sensitive plant materials.