Abstract: The root tuber of wild asparagi radix was used as raw material for the extraction of asparagi radix polysaccharide (ARP) by water extraction and alcohol precipitation method. The physicochemical and rheological properties of ARP were studied. The purity, the average molecular weight (Mw), the esterification degree and the chemical composition of polysaccharides were determined. Additionally, the crystallization properties, thermal properties and the effects of different factors on the apparent viscosity and shear stress of ARP were also been studied. In the meantime, the dynamic rheological properties of ARP were explored. The results indicated that the content of total polysaccharide, the total uronic acid content, the esterification degree and the average molecular weight of polysaccharide were (93.75±1.68)%, (26.99±0.97)%, (38.2±0.14)% and 730 kDa respectively. ARP was composed of six monosaccharides (Rha, Ara, Gal, Glc, Xyl, Man) and two uronic acids (GalA, GlcA) in a molar ratio of 0.27∶1.39∶4.42∶12.66∶0.50∶0.50∶4.83∶0.29. The results of scanning electron microscope and atomic force microscope showed that the conformation of ARP was spherical and aggregated, and the surface was compact and smooth. Moreover, X-ray diffraction illustrated that the crystallinity of ARP was low. The thermal properties suggested that ARP had high thermal stability. In addition, the rheological analysis demonstrated that temperature, mass concentration, type and concentration of salt ions (Na+ and Ca2+) had an influence on the changes of the viscosity and shear stress, and their mechanisms were different. As the shear rate increased, the viscosity of ARP solution decreased. The phenomenon of shear-thinning indicated that ARP solution belonged to a non-Newtonian fluid. The analysis results are expected to provide a theoretical basis for the development and utilization of Asparagi radix polysaccharide in food and medicine fields.
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