Modeling Mass Transfer Kinetics and Mass Diffusivity During Osmotic Dehydration of Blanched Carrots

Osmotic dehydration of 3.5 mm thick blanched carrot slices was carried out in order to study the effect of sucrose concentration, solution temperature and time on mass transfer kinetics and mass diffusivity. The experiments were conducted at the combinations of four sucrose concentration (30, 40, 50 and 60% w/w) and four solution temperatures (25, 37.5, 50 and 62.5°C). At each combination, nine time intervals (10, 20, 30, 40, 50, 60, 80, 100 and 120 min) were selected to determine the moisture loss and sucrose gain. Sample-to-solution ratio was kept 1:10 w/w through all the experiments. It was found that sucrose concentration and time of osmosis increased mass transfer whereas; solution temperature showed effect only on solid gain. Azuara’s models were used to determine the mass transfer kinetics and variable mass diffusivity coefficients. The average moisture diffusivity and solid diffusivity values were in the range 2.23×10-8 to 12.85×10-8 m2/s and 1.20×10-8 to 7.64×10-8 m2/s, respectively. Also, at each concentration, the values of activation energies for moisture loss and solid gain were found to be in the range 12.46 to 24.98 kJ K-1 mol-1 and 9.68 to 31.27 kJ K-1 mol-1, respectively.