Mathematical modeling and quality characteristics of microwave dried medicinal borage leaves

The leaves of Indian Borage (Coleus aromaticus) are very rich in nutritional as well as medicinal qualities. The present study is an effort to explore the possibility of effective utilization of the leaf which is perishable, for which dehydration is an essential method of preserving the leaves with minimum spoilage. Drying characteristics of Coleus leaves have been studied in microwave drying. To determine the kinetic parameters, the drying data were fitted to various models based on the moisture ratios versus drying time. Among the models proposed, the semi-empirical Midilli model gave the best fit for all drying conditions applied. The goodness of fit was determined using the coefficient of determination (R²), residual sum square (RSS).The effect of the microwave power levels (180 to 900 W, at 180 W interval) on quality characteristics (total phenolics, antioxidant activity and sensory parameters) of the dried leaves has been studied. Considering the total drying time, therapeutic and sensory attributes of the dried leaves, it is proposed to dry the leaves at 540 W in a microwave dryer to obtain an acceptable product.