Thin-layer air impingement drying enhances drying rate of American ginseng (Panax quinquefolium L.) slices with quality attributes considered

• Air impingement drying enhances drying rate compared with other drying methods.
• The drying temperature and sample thickness had a significant effect on the color.
• Ginsenoside Rg1 and Re decreased with increasing of the drying temperature.
• Drying temperature, air velocity, and thickness had a negative effect on the RR.
• Optimum drying conditions were proposed considering drying time and quality.

The effect of drying temperature, air velocity, and sample thickness on thin-layer air impingement drying characteristics and quality of American ginseng slices in terms of color parameters (L*, a*, and b*), ginsenosides content (Rg1, Re, and Rb1), rehydration ratio (RR), and microstructure were investigated. Results indicated that thin-layer air impingement drying enhances drying rate dramatically compared with other drying methods, and that the drying time was principally affected by drying temperature followed by sample thickness and air velocity. Quality evaluation revealed that both drying temperature and sample thickness had significant effects on the change of color, whereas, air velocity did not have any significant effect. It was also observed that ginsenosides Rg1 and Re decreased with increasing drying temperature. Drying temperature, air velocity, and sample thickness had significant negative effects on the RR of dried slices. Microstructure comparison illustrated that starch gelatinization occurred at a drying temperature of 65 °C and that a gel layer was formed on the sample's surface. On the basis of the drying time and quality of the dried products, the most favorable drying conditions were recommended.

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