Drying and Rehydration Behaviors of Convection Drying of Green Peas

Abstract

The drying behaviors of green peas were examined in a convection dryer for a temperature range of 55-70 degrees C with a constant air velocity of 2.1 m/s. The green peas were pretreated with ethyl oleate and citric acid solutions and blanched with hot water at 85 degrees C before drying. The drying process was continued until sample moisture fell to 0.3 kg water/kg dry matter (dm). The blanched samples dried faster than those in other pretreatments and control conditions. Moreover, rehydration capacities of the pretreatments were higher than control samples. The experimental results illustrated the absence of a constant rate drying period and the drying process took place in the falling rate period. Moisture transfer from green peas was described by applying Fick's diffusion model, and the effective moisture diffusivity was calculated. The calculated effective diffusivity ranged from 8.059 x 10(-11) to 1.973 x 10(-10) m(2)/s for the studied temperature range. The values of activation energy (E-a) were 22.01, 26.86, 30.31, and 30.99 kJ/mol for samples pretreated with citric acid, control samples, samples pretreated with ethyl oleate, and blanched samples, respectively. Drying data were fitted to four thin-layer drying models; namely, Lewis, Henderson and Pabis, logarithmic, and Page. The performance of the models was evaluated by comparing the coefficient of determination (R-2), reduced chi-square (chi(2)), and root mean square error (RMSE). The models that best represented green pea drying were the logarithmic and Page models.