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

摘要

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 (X~2), wot 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)~* & < ΔE_(sorbitol+hot air)~*.