Drying characteristics and mathematical modeling of hot air drying of cooked sweet potatoes

To provide a theoretical foundation for the industrial production of dried sweet potato, the hot air drying characteristics of sweet potato slices were examined under different temperatures (60, 70 and 80℃), air velocities (0.8, 1.2 and 1.6 m/s) and slice thickness (0.6, 0.9 and 1.2 cm), respectively. The drying data were fitted to different semi-theoretical models, such as Newton, Page, modi?ed Page, Henderson and Pabis, Logarithmic, two-term, Wang and Singh, Thomson, diffusion approach, Werma, et al., modi?ed Henderson and Pabis, and two term exponential models. As a result, the Wang and Singh model gave better predictions than other models with the decision coefficient (R2) of 0.998, chi-square (χ2) of 0.000168 and root mean square error (RMSE) of 0.0117. The effective moisture diffusivity and activation energy were also computed. The results indicated that Deff increased with the increasing of drying temperature, air velocity and material thickness, and activation energy of drying was 40.103 kJ/mol. The results can provide technical bases for the control of drying process of sweet potato.