Microwave drying of turmeric ( Curcuma longa L.): RSM-based optimization of microwave power and thickness

This study aimed to examine the repercussion of microwave (MW) power and slice thickness on drying characteristics and biochemical properties turmeric. The experiment studies were designed using response surface methodology (RSM). 13 experiments were conducted with thicknesses between 2 and 6 mm and MW powers ranging from 250 to 650 W. Furthermore, RSM was used to obtain turmeric-optimizing conditions. Quadratic models were used to fit the biochemical parameters including moisture content (MC), protein, total phenolic content (TPC), total carbohydrate, total oil, crude fibre and antioxidant activity (AA); additionally, slice thickness (mm) and MW power (W) were also taken into consideration. The models were fitted using a central composite rotatable design (CCRD). The findings of the analysis of variance (ANOVA) statistical test suggested that the optimal dried turmeric qualities were reached at a MW power of 514.68 W and a slice thickness of 2.5 mm, resulting in a drying time of 35.376 min, MC of 9.135%, total carbohydrate of 55.962%, true protein of 9.455 g/100 g, crude fibre of 5.521%, total oil of 6.522%, TPC of 374.628 mg GAE/100 g and AA of 46.106%. The close agreement between experimental and predicted values validated the model’s effectiveness. These findings have practical implications for improving turmeric product quality, extending shelf life and reducing drying time and energy consumption, thereby promoting sustainable and efficient spice processing practices.