The effects of air temperature, sphere diameter and puffing with Co2 on the drying of potato spheres

An experimental air dryer was used to investigate the effects of air temperature, sphere diameter and puffing with CO2 on the drying of potato spheres. Accordingly, the experimental results showed only falling-rate behaviour and hence drying completely controlled by internal mass transfer was interpreted on the basis of Fick's diffusional model for non-steady state diffusion. Drying rate increased with increasing air temperature, and also increased with decreasing diameter of sphere. By considering the diffusion coefficients at different diameters, it was established that the drying occurred by a diffusion mechanism as opposed to a capillary mechanism. It was also found that CO2 puffing had a positive effect on the drying rate.