Drying characteristics and efficacy index evaluation for main root of Yunnan panax notoginseng

Abstract: In foreign countries, the research of drying characteristics about medicinal plants mainly includes ginseng and American ginseng. In China, the study on Yunnan panax notoginseng mainly focuses on the physiological property and effects of ginsenosides on human bodies, but the research on processing technology is superficial. According to the national standard in China, the main efficacy index of panax notoginseng is the panax notoginsenoside(PNS) content. However, there are no reports on the effect of drying methods and drying conditions to PNS content. In order to study the influence of drying process to PNS content of Yunnan panax notoginseng, Yunnan panax notoginsengs and their slices were dried by three different methods (natural drying, oven drying and hot-air drying) in this work. The drying curves and drying rate curves of these methods were obtained. The drying kinetics models of main roots within different temperatures in oven drying were established. Meanwhile, the PNS contents of main roots dried by these methods were tested through High-performance Liquid Chromatography(HPLC), and the regression equation about temperature and time to PNS content was established and optimized. Results showed that oven drying had a shorter drying time and faster drying rate compared with natural drying. The PNS contents of dried products within natural drying, oven drying and hot-air drying were 7.246%, 11.305%, 8.259%, respectively. It showed that the oven drying kept the PNS content of panax notoginseng higher. Through drying curves and drying rate curves of panax notoginseng, it could be found that there was only falling rate period and no constant rate period during the drying process. The parameters of Lewis model, Page model and Henderson-Pabis model were evaluated through R2. Page model was found to be more suitable in describing the drying characteristics of panax notoginseng. The drying kinetics equation was MR=exp-0.0037exp(0.0623T)t1.5336exp(-0.0156T). It firstly put forward the relationship among moisture ratio, drying temperature and drying time at the drying process of main roots, and it provided a basis for the control of drying process of panax notoginseng. The effective moisture diffusivity of main roots dried at different temperatures was among 3.073×10-10m2/s-1.291×10-9m2/s. The results of significance analysis showed that the drying temperatures had a highly significant impact on the effective moisture diffusivities. The regression equation about temperature and time to PNS content of main roots was y=-606-61.875T+36.625t+0.7559T2-0.1641Tt-0.1096t2. Through response analysis and equation optimization, under the condition of safe moisture content, the better drying temperature (50℃-60℃) and time (106-144 h) were obtained. Although main roots' slices had a shorter drying time compared with the whole main roots, the PNS contents of them were lower than the main roots'. To sum up, in order to keep the active ingredients(PNS) of panax notoginseng better, the whole main roots are more fit for the drying process. This result are meaningful to guide the actual production of Yunnan panax notoginseng.