Jelly Gels Based On The Interactions Of Mesona Chinensis Benth Polysaccharides And Sweet Potato Starch And Its Film-forming Properties

Starch is one of the most abundant carbohydrates in nature,and it is widely used as gelling agent,thickener,stabilizer,etc.in food,but there are problems such as easy aging,water separation,and thermal instability after starch pasting.The physical mixing of hydrocolloids such as non-starch polysaccharides and starch as a green and pollution-free method can improve the above disadvantages of starch and have obvious improvement on the gelation properties such as pasting and texture of starch.In this paper,Mesona chinensis Benth polysaccharide（MCP）was obtained by alkali extraction and alcohol deposition method,and MCP was mixed with sweet potato starch（SPS）to comprehensively study the effect of MCP on the gel properties of SPS such as pasting,rheological and texture,and the interaction mechanism between MCP and SPS was investigated by infrared spectroscopy,low field NMR and interaction force test.The effects of different edible alkali on the gel properties of SPS-MCP gels were also investigated to provide a comprehensive and objective understanding of the roles of MCP and edible alkali in the gel properties of SPS and to provide a theoretical reference for the study of SPS-based foods.In addition,the improvement effects of MCP and sodium carbonate on SPS films were also investigated to provide some theoretical references for the further application of MCP and sodium carbonate in starch films.The main studies were as follows:（1）Different concentrations of MCP（0.01%,0.05%,0.1%,0.3%and 0.5%,w/v）were compounded with SPS（6%,w/v）to investigate the effects of MCP on the gel properties such as pasting,rheology and texture of SPS.The results of pasting experiments showed that MCP could significantly increase the peak viscosity,breakdown viscosity and setback viscosity of SPS-MCP gels.Rheological experiments revealed that SPS-MCP gels have shear thinning properties.The dynamic rheological results showed that MCP could effectively increase the viscoelasticity of SPS-MCP gels.Textural analysis results found that the addition of MCP could improve the gel strength and hardness of SPS-MCP gels.The IR results and interaction force tests indicated that the interaction between SPS and MCP might be mainly maintained by hydrogen bonding and electrostatic force,which had significant effects on the physicochemical and rheological properties of SPS-MCP gels.The scanning electron microscopy results showed that the addition of0.1%MCP improved the network structure of SPS-MCP gels.（2）The effects of Na₂CO₃ and NaHCO₃ addition on the pasting,textural and rheological properties of SPS-MCP gels were investigated.The main conclusions are as follows:Na₂CO₃ and NaHCO₃ can reduce the pasting viscosity（peak viscosity,trough viscosity,and breakdown viscosity）of SPS-MCP gels,but the addition of high concentrations of Na₂CO₃ and NaHCO₃ can increase the final viscosity of SPS-MCP gels.The results of rheological and textural tests showed that alkali increased the apparent viscosity,viscoelasticity and textural properties of SPS-MCP gels.LF-NMR tests indicated that alkali reduced the water mobility of SPS-MCP gels and helped them retain water.IR spectroscopy also demonstrated that alkali could enhance the hydrogen bonding interaction between SPS and MCP.Scanning electron microscopy results showed that alkali could make the pores smaller and the microstructure more dense.These results can help to understand the interaction between alkali and starch-hydrocolloid system and promote the application of alkali in food industry.（3）The effects of MCP and Na₂CO₃ on the improvement of physical,optical,mechanical and thermal properties and microstructure of SPS films were investigated.The rheological results showed that the addition of MCP and Na₂CO₃ improved the apparent viscosity and viscoelasticity of the film-forming solution.MCP and Na₂CO₃ can improve the solubility and swelling of SPS film.The tensile test showed that MCP and Na₂CO₃ could enhance the tensile strength and elongation at break of SPS film,and MCP could improve the UV blocking ability of the film by increasing the chromaticity of SPS film.The results of thermogravimetric analysis showed that MCP and Na₂CO₃ could improve the thermal stability of SPS film.The results of scanning electron microscopy and atomic force microscopy showed that SPS and MCP had good compatibility and formed smooth and flat surfaces of SPS film.These results indicated that MCP and Na₂CO₃ can improve the physicochemical properties of starch films and provide a theoretical basis for the application of SPS films in food packaging.