IMAGE ANALYSIS AND DYNAMIC MODELING OF THIN-LAYER DRYING OF OSMOTICALLY DEHYDRATED PUMPKIN

Abstract

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 (R2), reduced chi square (χ2), 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 ofΔE*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.