Abstract:In order to prepare a high solubilizing and emulsibity rice protein，the method wet-heating grafting reaction of extruded rice protein and dextran was ultilized to study the influence of barrel temperature，the material moisture content and screw speed on the degree of substitution.The optimal process conditions were determined through single factor experiment analysis：barrel temperature 90℃，35%moisture content of material，screw speed 200 r/min，Under this condition，the degree of substitution reached at（17.6±0.3）%.The solubility and emulsification，surface hydrophobicity of extruded rice protein-dextran conjugates on the degree of substitution of（17.6±0.3）%was investigated，the results showed that compared with the native rice protein，the solubility of extruded rice protein and dextran conjugates increased significantly in a wide range，increased by 8.4%-76.6%，the emulsification activity and emulsification stability increased by 62.2%and 73.9%，respectively，the surface hydrophobicity decreased by 69.5%.Meanwile，experiment analyzed subunit structure and molecular weight changes and apparent characterization of rice protein by the methods and means of Fourier infrared spectrum and SDS-PAEG electrophoresis and SEM，the results analysis showed that extrusion and grafting reaction changed the structure of protein subunits significantly，the content of α-helix and β-turn and random coil increased by 24.4%，26.0%and 19.9%，respectively，and β-sheet structure content decreased by 15.0%，significantly，SDS electrophoresis analysis results showed that the extruded rice protein and dextran conjugates the line of 51.0 ku and 80 ku-82 ku become blurred，a high molecular weight appeared in the region between acrylamide separating gel with acrylamide stacking gel，indicated molecular weight have happened a big weight aggregates of covalent connection，the SEM analysis of the apparent structure，indicated the graft reaction and s extrusion modified protein structure significantly.