The Evolution Mechanism Of PH-induced Soy Hull Polysaccharides O/W Interface Adsorption Behavior

Polysaccharide has good emulsifying properties and can be used as an emulsifier in the food field.Its interface adsorption behavior is very important for the stability of food emulsions,but it has not been revealed yet.This paper takes Soy Hull Polysaccharide(SHP)as the research object,explored the influence of pH on the microstructure,rheological properties and thermal stability of SHP,and clarified the evolution mechanism of its interface adsorption behavior.And it was that laid a theoretical foundation for revealing the mechanism of polysaccharides affecting emulsion stability.The main research results are as follows:1.In an aqueous solution,the distribution of carboxyl and carbonyl groups on the surface of SHP molecules were induced by pH changes the amphiphilicity of SHP.At pH2.0-4.0,the adsorption capacity of SHP at the oil/water interface was enhanced.It was decreased at pH 5.0-7.0,and increased at pH 8.0-9.0.In addition,at pH 2.0-4.0,SHP has a compact structure,high bound water content,easy phase transition,and low thermal stability.2.At pH 2.0-4.0,the electrostatic repulsion between SHP molecules was weakened,and the droplets aggregate.The particle diameters were all above 30 ?m,which was significantly arger than other samples and the surface structure was loose,and non-polar molecules such as amino acid residues move to the hydrophobic direction.At pH 5.0-7.0,the electrostatic repulsion between SHP molecules increases,the particle size decreases,the surface structure was dense,and the amino acid residues move toward the hydrophilic direction.At pH 8.0-9.0,the Zeta-potential of SHP molecules decreases,but the particle size does not change significantly,the surface structure is loose,and non-polar molecules move in the hydrophobic direction.3.The pH-induced change of the surface affinity of the SHP emulsion interface layer had a significant effect on its interface rheology and thermal stability.At pH 2.0-4.0,the order structure of ?-helix,?-sheet and ?-turn in SHP were increased,which leads to the weakening of its molecular directional movement ability and the increase of the viscosity of the interface layer.The hydrophobicity of amino acid residues on the peptide chain increases,which improves the interface adsorption capacity of SHP and enhances the stability of the interface layer.In the 300-500 ?,the enthalpy change of the interface layer was significantly greater than pH 5.0-9.0,and were greater than 120 J/g,indicating that the thermal stability of the interface layer was reduced.Above all,at pH 2.0-4.0,electrostatic interaction was the main factor that induced the evolution of SHP molecular conformation and interface behavior.At pH 5.0-9.0,the surface affinity of SHP molecules was the main reason for the evolution of its adsorption behavior at the oil/water interface.