Effect of microwave treatment on dehydration kinetics and moisture diffusivity of Asiatic Himalayan black carrot

Abstract

Drying as preservation technique is an old process involving simultaneous heat and mass transfer resulting in reduction of moisture to lower water activity levels. The removal of unbound moisture by dehydration lowers down the water activity levels. Present study determines the effect of microwaves on dehydration characteristics (operated at 2450 MHz) of carrot shreds at different intervals of time (1, 2 and 3 min). The microwave treatment resulted in decrease of overall dehydration time with higher treatment time combination decreasing it more profusely than lower treatment time combination. The decrease in dehydration time after three minutes of microwave treatment followed by drying at 50, 60 and 70 °C temperatures was approximately 18, 35 and 48%, respectively with respect to untreated carrots. The experimental data points were fitted to different mathematical models for determining the best fit model for the process. Experimental values were proficiently fitted by page model as evident from its higher R2 and lower RMSE (Root Mean Square Error) values. Imparting microwave treatment to shreds provided stimulus for increasing the drying rates. Effective moisture diffusivity was lowest for untreated carrot shreds and highest for 3 min treated shreds. Activation energy of drying process by virtue of microwave application decreased from 36.31 to 14.24 kJ/mol.