Experimental analyses of drying characteristics of selected food samples

Abstract

The objective of this work was to separately study the various aspects of drying. Agricultural produce were selected across various categories and their drying curves, prediction of the drying rates during constant rate periods of drying, the critical moisture contents and finally whether drying in the falling rate was capillary controlled or diffusion controlled were studied. Palm candy solution was included in the study to analyze the diffusivity values for a solution. Drying experiments were conducted with convective hot air flow in cabinet tray dryer. In case of palm candy solution and potato slices, drying was mainly capillary controlled in the falling rate period. The constant drying rate Rc in case of palm candy solution and potato slices were 2.986 x 10^-4 kg H₂O m^-2s^-1 and 2.5 x 10^-4 kg H₂O m^-2s^-1, respectively.In case of mango pulp and banana slices the drying was diffusion controlled in the falling rate period and the constant drying rate Rc for the mango pulp and banana slices were 2.44 x 10^-4 kg H₂O m^-2s^-1and 2.00 x 10^-4 kg H₂O m^-2s^-1 respectively. The diffusion coefficients D_eff for mango pulp and banana slices were 3.655 x 10^-10 m^-2 s^-1and 3.428 x 10^-10 m^-2 s^-1, respectively.  Paddy drying properties were studied at different temperatures and it was observed that with elevation of temperature both constant drying rate Rc and diffusion coefficient D_eff increased.