Research On Drying Characteristics And Mass Transfer Model Of Yunnan Panax Notoginseng

Panax notoginseng is a traditional Chinese medicine. In recent years, its plantings and requirements are increased, and the traditional artificial processing methods cannot meet the needs, while the mechanical processing should be done. So it is necessary to research the processing technology. In this work, the main roots of Yunnan panax notoginseng were researched. First of all, some of its basic physical properties (the qualities, the length, the diameters, the volumes and the particle densities) were determined, and their changes along with moisture content were tested. Secondly, the main roots and their slices were dried by three different methods (natural drying, oven drying and hot-air drying). The panax notoginsenoside(PNS) contents of main roots dried by these methods were tested through High-performance Liquid Chromatography (HPLC), and the regression equation about temperatures and times to PNS contents was established and optimized. Meanwhile, four different drying kinetics models (the Lewis, Page, Henderson-Pabis and Wang-Singh models) were used and selected to describe the drying process of main roots. Finally, through the fractal theory, the mass transfer model was established and verified. The conclusions were as follow:(1) The individual differences of main roots of fresh panax notoginseng were significant. Its average values of the quality, the length, the diameter and the volume were 25.39g、68.58mm、26.74mm、9.77cm3, respectively. In the drying process, while the moisture contents were reduced, the quality, the length, the diameter and the volume were reduced. Meanwhile, the regression equations among with these basic physical properties and moisture contents were obtained, the results can provide a theoretical basis for the inner mass transfer.(2) The artificial drying had a shorter drying time and faster drying rate compared with natural drying, and it kept the PNS content of panax notoginseng higher. In the drying process, the drying temperatures and drying times had a significant impact on the PNS content. Through the regression equation, the drying temperatures should be chosen among 50 to 60 ℃, while the PNS content can be kept better. Under the condition of experiment, 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’. In the actual production, the whole main roots are more fit for the drying process.(3) Four different drying kinetics models (the Lewis, Page, Henderson-Pabis and Wang-Singh models) were used and selected to describe the drying process of main roots, using R2, RMSE and χ2 to evaluate the fitting results. Results showed that the Page model had a highly R2 value, low RMSE and χ2 values, and it was fit for describing the drying process of main roots. The drying kinetics equation was MR=exp[-0.0037exp(0.0623T)t1.5336exp(-0.0156T)] The ANOVA showed that temperatures had a significant impact on this model.(4) Central xylem and outer skin of the main roots were modeled respectively. Through the mathematical method, the one-dimensional mass transfer model was obtained. The paraffin sections were got based on the paraffin methods. Using microscope, the fractal dimensions, the effective moisture diffusivities of center xylem and outer skin within different temperatures(40 ℃、50 ℃、60 ℃、70 ℃、80℃) were obtained. This model was verified through 55 ℃. The results provide a theoretical basis for the drying characteristics of main roots of panax notoginseng.