Microwave drying characteristics and qualities of dried orthosiphon aristatus leaves

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Vorapong Klungboonkrong
Singhanat Phoungchandang


Orthosiphon aristatus (OA) is widely used in Southeast Asia as a traditional remedy for various illnesses, such as kidney stones, high blood pressure, diabetes, rheumatism, arthritis, gout and possibly others ailments. Vacuum blanched and unblanched OA leaves were dried in a microwave dryer (MWD) at 450, 720 and 900 W. Drying data were fitted to four thin layer drying models to describe microwave drying characteristics of the OA leaves. Physical and chemical properties were evaluated. The results revealed that a three‑parameter model was the most suitable drying model to describe the drying of AO leaves. It had the highest coefficient of determination (R2) as well as the lowest standard error of estimate (SEE) and root mean square error (RMSE). The drying times of unblanched and vacuum blanched AO leaves could be reduced by 66.7% and 50.0%, respectively, when the microwave outputs were increased from 450 W to 900 W. Dried OA leaves using MWD at 720 and 900 W in both treatments (vacuum blanched and unblanched) had the least color change. Vacuum blanched and dried OA leaves using MWD at 900 W were more porous and had less cell damage than other treatments. Vacuum blanched and dried OA leaves using MWD at 900 W showed the highest total phenolics, sinensetin and eupatorin contents. Processing OA leaves by vacuum blanching and then subjecting them to MWD at 900 W is the recommended drying method.



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