Plasma drying effect and quality evaluation of fresh Codonopsis pilosula slices

Due to the high sugar and water content of freshly harvested herbs, they are easily affected by pests and mildew. Therefore, timely drying of herbs after harvesting is a key aspect to ensure the quality of herbs. With the improvement of living standards, the drying of herbal slices (especially mid- and high-end herbs) is in urgent need of new drying technologies with high retention rate of medicinal ingredients and long shelf life. Plasma is considered as a non-thermal drying technology with great potential to retain active medicinal components to a greater extent. In this paper, we used plasma technology to dry the slices of fresh Codonopsis pilosula as the research object. We investigated the effects of discharge gap, slice thickness and oblique cutting angle on the drying process of codonopsis slices. The differences in color between natural dried codonopsis and plasma dried codonopsis were also compared and analyzed, and the content of lobetyolin in codonopsis was determined by high performance liquid chromatography (HPLC). The results showed that different discharge gap, slice thickness and oblique cutting angle would affect the drying process of codonopsis slices. The color analysis showed that the plasma-dried codonopsis slices were lighter in color and did not undergo significant browning compared with natural dried. HPLC analysis showed that plasma-dried codonopsis contained about three times higher lobetyolin than natural dried ones. In conclusion, plasma technology performed well in drying codonopsis slices.