Effects of different drying methods on appearance and internal components of Notoginseng Radix et Rhizoma / 中草药

ABSTRACT

Objective: The effects of different drying methods (drying-in-the-shade, sun-drying, freeze-drying and hot air drying) on the appearance traits, internal structure and quality of the main roots of Notoginseng Radix et Rhizoma (NRR) were revealed, which provided a theoretical basis for screening the drying methods suitable for the primary processing of NRR. Methods: In this study, the effect of four different drying methods on drying rate, rehydration rate, appearance traits, alcohol extracts and internal components (dencichine, saponin component notoginsenoside R1 and ginsenoside Rg1, Rb1, Rd, Re, and reducing sugar, total sugar) of NRR were compared. Results: Fresh NRR was dried by drying-in-the-shade method, and the drying rate was slow, which took about 473 h. However, the appearance quality of the medicinal materials was excellent with firm texture, slow rehydration rate, and high content of total saponins and dencichine. The drying rate of materials under sun drying method was also slow, and due to the long drying cycle, the starch and sugar of the medicinal materials were more decomposed, resulting in the whitening part of the medicinal materials of NRR. When fresh NRR was dried by hot air, the drying rate was faster and the time was shortened. When the temperature was 40 ℃, the appearance of the medicine was not much different from that of the drying-in-the-shade method. After drying, the material was firmer, except for the content of dencichine, the content of saponin had no difference between that of drying-in-the-shade; Due to the high drying temperature at 50 ℃ and 60 ℃, the excessive dehydration rate led to the hollowness of the NRR, and medicinal material was not solid; The rehydration rate was fast, and the content of NRR spilled out, resulting in sugar coking, and the color of the cross section of the medicinal material changed into deeper with the increase of the drying temperature, which resulted in the decomposition of starch, and the significant increase of total sugar and reducing sugar content. The lyophilized medicinal material had a very fast rehydration rate, and the internal texture was loose and porous, and the texture became light, but the saponin component and dencichine were the highest active ingredients. Conclusion: Considering the aspects of appearance, medicinal ingredients and cost, fresh NRR dried by drying-in-the-shade method obtained solid material, compacted internal structure, good appearance and high content of medicinal ingredients. The primary processing method of NRR should be drying-in-the-shade. If the processing volume of the medicinal material is large, it needs to shorten the drying time, and the primary processing method of NRR should be hot air drying process at about 40 ℃. If the high-content medicinal ingredients are the purpose, it is recommended to use freeze-drying.