Drying features of microwave and far-infrared combination drying on white ginseng slices.

In this study microwave and far-infrared combination drying were conducted to investigate the effect of microwave and far-infrared heating mode switching point water content (SW), ginseng slice thickness, and far-infrared drying temperature on drying indicators (surface colour difference, ginsenosides content, and surface shrinkage rate) and drying efficiency (drying time) during the process of drying white ginseng slices. Regarding microwave drying, the microwave drying time cannot exceed 150 s, and the ginseng slice water content cannot be less 50%. For the combination drying, SW, far-infrared drying temperature and slice thickness increased, the colour difference and surface shrinkage rate first decreased and then increased, and the content of ginsenosides first increased and then decreased. In addition, the combination drying showed faster drying rate, higher ginsenosides contents value, colour difference (ΔE) value and lower surface shrinkage rate than single far-infrared drying.