Physicochemical, rheological and thermal properties of Mesona chinensis polysaccharides obtained by sodium carbonate assisted and cellulase assisted extraction.

Mesona chinensis has been used as a Chinese folk medicine and main ingredient used to make "black bean jelly" in Asia for hundreds of years. In this study, two polysaccharides (MCP-C and MCP-S) from Mesona chinensis were extracted by using cellulase assisted extraction (CAE) and sodium carbonate assisted extraction (SAE), separately. Then the different physicochemical characteristics, rheological and thermal properties of two polysaccharides were analyzed by ion chromatography, high-performance gel permeation chromatography (HPGPC), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), rheological and thermogravimetric analysis. Results indicated that the contents of total sugar and uronic acid of MCP-C were higher than MCP-S, while the protein content and molecular weight was lower than that of MCP-S. MCP-S and MCP-C had differences in the surface morphology by SEM, while they all had the typical IR spectra characteristic and amorphous morphology of polysaccharides. The rheological experiments showed that MCP-C and MCP-S exhibited typical pseudoplasticity fluids behavior. The apparent viscosity (η), storage modulus (G') and complex viscosity (η*) of MCP-S were higher than MCP-C. The three-stage decomposition patterns were observed in MCP-C and MCP-S. MCP-S was more stable and had higher initial decomposition temperature (Ti) than MCP-C.