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 (χ 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 (ΔE* values) increased during drying in a sequence of ΔE* _{sucrose solution} < ΔE* _{sorbitol solution} < ΔE* _{sucrose+hot air} & < ΔE* _{sorbitol+hot air}. PRACTICAL APPLICATIONS The combined treatment of pumpkins using osmotic dehydration followed by hot-air drying may provide a practical method for the preservation of pumpkin and the production of dehydrated pumpkin products.