Image analysis and dynamic modeling of thin-layer drying of osmotically dehydrated pumpkin

This study was conducted to investigate the effect of osmotic dehydration as a pretreatment on hot-air drying kinetics of pumpkin, to evaluate the best model for hot-air drying of pumpkin and to apply a computer vision system to study the color changes during drying. Pumpkin cubes were treated in 50% w/w sorbitol or sucrose solutions at 50C for up to 6 h, followed by hot-air drying at 60C and air velocity of 1 m/s. Drying data were fitted to 11 drying kinetic models. The goodness of fit was determined using the coefficient of determination (R-2), reduced chi square (chi(2)), root mean square error (RMSE) and percent mean relative deviation modulus (E%). Hot-air dried samples pretreated with sorbitol had an improved lightness (higher L* values) compared to the hot-air drying while that pretreated with sucrose exhibited lower L* values. The total color changes (Delta E* values) increased during drying in a sequence of Delta E-sucrose solution* < Delta E-Sorbitol solution* < Delta E-sucrose+hot air(*) & < Delta Esorbitol+hot air*.