Drying Kinetics of Zingiber cassumunar Roxb. by Far-Infrared Radiation under Vacuum Condition

Abstract

This research aimed to investigate the drying kinetics of Zingiber Cassumunar Roxb. (ZC), the optimal drying models, and quality assessment of 5 mm thick ZC samples by using far-infrared (FIR) radiation at different intensities of 4,929, 6,550, 8,541 and 10,955 W/m² under a vacuum condition of 5 kPa (an absolute pressure). The initial moisture content of ZC was 3.58±0.04 g water/g dry matter, and was expected to reach a final moisture content of 0.10±0.02 g water/g dry matter after drying process. The drying times obtained were 145, 85, 55, and 35 min for the respective radiation intensities. The drying process exhibited a decreasing drying rate under all conditions. The model accuracy was assessed using experimental data from five drying models, employing the coefficient of determination (R²) and the root mean squared error (RMSE). The drying model proposed by Midilli et al. (2002) yielded the most accurate drying predictions, with the highest R² value and the lowest RMSE value. The effective moisture diffusion coefficient ranged from 0.59x10^-7–2.75x10^-7 m²/s, and the activation energy of ZC was 17.97 kJ/mol. Regarding the quality of the dried ZC, it was observed that the yellowness (b*) decreased with increasing drying intensity. The bulk density values ranged from 0.19 to 0.31 g/cm³, and shrinkage values ranged from 77.57-93.47 percentages. An increase in radiation intensity led to an increase in both bulk density and %shrinkage values. However, no significant difference was observed between the drying conditions using radiation intensities of 4,929 and 6,550 W/m².