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Temperature Dependent Dehydration Kinetics and Effective Diffusivity of Spinach Leaves

Prasad K and Ankita P

The drying of spinach leaves was investigated in a laboratory dryer maintained at different isothermal temperatures ranging from 50°C to 90°C with an interval of 10°C. The effect of blanching and dehydration temperature on drying time and drying rate was studied. It was found that the dehydration kinetics of spinach leaves is temperature dependent and blanching has affected the dehydration characteristics. To an extent of 60% shortening of drying time has been found to yield the dehydrated leaves when dried at 80°C as compared to 50°C. Double stage drying of fresh spinach leaf is suggested with one hour initial drying at 80°C with the finishing the dehydration with 60°C further to obtain the quality dehydrated produce. Fitting of basic dehydration model confirmed the applicability of Page model in predicting the dehydration kinetics effectively. Effective moisture diffusivity was found to be temperature dependent and varied in the range 1.380 × 10-11 to 4.720 × 10-10 m2/s and 2.204 × 10-11 to 4.303 × 10-10 m2/s over considered dehydration range of temperature for untreated and blanched spinach leaves, respectively. The temperature dependence effective moisture diffusivity in form of activation energy was found to be 39.74 kJ/mol for untreated and 19.23 kJ/mol for blanched spinach.