Modelling of air drying of fresh and blanched sweet potato slices

Effects of blanching, drying temperatures (50-80 °C) and thickness (5, 10 and 15 mm) on drying characteristics of sweet potato slices were investigated. Lewis, Henderson and Pabis, Modified Page and Page models were tested with the drying patterns. Page and Modified Page models best described the drying curves. Moisture ratio vs. drying time profiles of the models showed high correlation coefficient (R² = 0.9864-0.9967), and low root mean squared error (RMSE = 0.0018-0.0130) and chi-squared (χ² = 3.446 x 10⁻⁶-1.03 x 10⁻²). Drying of sweet potato was predominantly in the falling rate period. The temperature dependence of the diffusion coefficient (Deff) was described by Arrhenius relationship. Deff increased with increasing thickness and air temperature. Deff of fresh and blanched sweet potato slices varied between 6.36 x 10⁻¹¹-1.78 x 10⁻⁹ and 1.25 x 10⁻¹⁰-9.75 x 10⁻⁹ m² s⁻¹, respectively. Activation energy for moisture diffusion of the slices ranged between 11.1 and 30.4 kJ mol⁻¹.