Evaluation of drying methods with respect to drying kinetics, mineral content and colour characteristics of rosemary leaves

Rosemary leaves (Rosmarinus officinalis L., Lamiaceae) were dried by using sun, oven (50 degrees C) and microwave oven (700 W, 2450 MHz) drying methods. Microwave oven drying shortened the drying time more than 99% when compared to the sun and oven drying methods. K, Ca, Na, Mg and P were the most abundant elements in the rosemary samples. The mineral content of oven dried rosemary leaves was higher than that of the sun and microwave dried samples. The logarithmic and Midilli and Kucuk models were shown to give a good fit to the sun and oven drying. The Page, Modified Page and Midilli and Kucuk models have shown a better fit to the experimental microwave oven drying data of rosemary leaves. Microwave oven drying revealed optimum colour values. Oven drying resulted in a considerable decrease in the colour quality of the rosemary leaves. (C) 2007 Published by Elsevier Ltd.