Drying of steamed Asian ginseng (Panax ginseng) roots by microwave-hot air combination

Steamed Asian ginseng (Panax ginseng) roots were dried by a combined microwave-hot air method in a modified experimental microwave oven. Hot air drying was used as a reference method. The drying time to achieve the desired moisture level (10%) as well as the ginsenoside contents and the color of the final product were determined. The ginsenosides Rb1, Rb2, Rc, Rd, Re, Rf, Rg1 and Ro were analyzed by HPLC. Compared with hot air drying, the combined microwave-hot air drying method resulted in a substantial decrease (approximately 30-40%) in drying time and had little influence on the ginsenoside contents and the color of the final product.