Quality of Korean ginseng dried by a prototype continuous flow dryer using far infrared radiation and hot air

This study was performed to examine the effects of infrared (IR)/hot-air combination drying on some quality attributes of Korean white ginseng. Medium-sized ginseng roots were dried in a dryer where both the far infrared radiation and hot air were available as energy sources for drying. Diametral shrinkage, external color, total saponin content, and ginsenosides and free sugar composition of the IR/hot-air combination dried ginseng were measured and compared with those of commercial white ginseng products. The external color became lower in lightness and higher in saturation as the IR radiating plate temperature increased. IR/hot-air combination dried white ginseng at IR plate temperature of 100°C was comparable to the commercial white ginseng products in color characteristics. Diametral shrinkage ratios of ginseng roots during drying ranged from 20 to 36% and appeared to be independent of the different drying methods used in the study. No definite evidence could be found whether the IR/hot-air combination drying and the conventional hot-air drying practice resulted in white ginseng having different ginsenoside contents and compositions. IR/hot-air combination dried ginseng showed a decrease in sucrose content and an increase in fructose, glucose, and especially maltose content as the IR plate temperature increased. No conclusion could be made in whether the various drying treatments used in the study affected the free sugar contents and compositions of white ginseng.