Forced-air drying of ginseng root: 1. Effects of air temperature on quality

The dried roots of American ginseng (Panax quinquefolius) are highly valued by Asian cultures as an herbal medicine. In Ontario, there is smallscale, commercial processing of ginseng, typically using modified tobacco kilns to dry freshly harvested root to about 10% moisture. The objective of our research is to improve control of the drying process so that quality factors (e.g., ginsenoside content, colour and shape) are preserved and drying time is reasonable. The first part of this research showed that three-stage (38-50-38 degreesC) temperature control reduced drying time by 40% relative to conventional practice which sets a maximum drying air temperature of 38 degreesC. Quality in terms of root colour and ginsenoside concentrations was comparable for the three-stage and constant 38 degreesC processes. Red striations (i.e., "red" root) did not develop on root surfaces as long as the drying air temperature was low when moisture content was above 55% (wet basis). Internal colour, measured as average L-* values of root cross-sections, was not significantly different for the two drying processes. Dried roots contained about 75% of the total ginsenoside levels of fresh roots but there was no significant difference between the two drying processes. The two ginsenoside fractions with substantial reductions were the Re fraction (50% lower in dried roots) and Rb1 fraction (18% reduction). (C) 2003 Elsevier Ltd. All rights reserved.