Effects of pre-treatments on drying kinetics of sweet potato slices

Abstract

 In this study, thin layer drying kinetics of sweet potato slices was investigated by using a hot air convective dryer operated at 50, 60, 70 and 80℃.  Different treatments were given to samples of sweet potato slices: some were blanched in hot water at 100℃ (WAT), others were dipped in sodium meta-bisulphite (SMB), while the rest were left untreated (UNT).  The experimental drying data were fitted to four well known drying models: the Modified Page 1, Wang and Singh, Two Term Exponential and Approximation of Diffusion.  Among the four models considered, the Modified Page 1 was found to best describe the drying kinetics of sweet potato slices.  The effective moisture diffusivity of the samples was in the range from 7.76×10^-9 m²/sto 1.2×10^-8 m²/s.  The values for activation energy, the energy necessary for the onset of the drying process, were 9.13 kJ/mol, 11.25 kJ/mol and 17.5 kJ/mol for WAT, SMB and UNT, respectively, indicating that it was easier to induce the water release process in the WAT and the SMB compared to the UNT samples.

Keywords: sweet potato, pre-treatment, drying kinetics, drying models