Effect Of Enzymolysis On Structure And Functional Properties Of Soybean Protein And Preparation Of Protein With High Emulsibility And Foamability

In this study, enzymolysis modification technology was applied to improve the functional properties of protein with biochemical and spectroscopic method, the effect of enzymolysis modification on structure and functional properties of SPI was explored in this research from the perspective of conformation and solution properties to develop soybean protein products with excellent functional properties. This research will provide a theoretical basis for intensive processing and further application.Through this research, we obtained the following conclusions:(1)The enzymolysis on SPI by three proteases from strongly to weakly was Alcalase alkaline protease>AS1.398neutral protease>papain.The solubility of SPI hydrolysate was improved which related with the greatly increase of solubility of11S globulin. The emulsibility of SPI which was hydrolyzed by alkaline protease or papain was increased remarkable which was related with the increase of soy β-conglobulin.The effect of neutral protease emulsibility of SPI was weak.The foamability of SPI hydrolysate was improved which related with the increase of foamability of both soy globulin and soy β-conglobulin.However,the foam stability was declined.The surface hydrophobicity of SPI which was hydrolyzed by alkaline protease or papain was improved.(2)Random coil structure content of SPI with enzymolysis increased with the decrease of α-helix and β-sheet structure content. More random coil structure provided more flexible protein structural units for SPI with high surface properties and emulsion stability.The peptide pond broke after the SPI was hydrolyzed, the particle size was decreased gradually.The absolute value of ε-potential of SPI hydrolyzed by alkaline protease or papain showed a tend of first increased and then decreased with time.The degree of hydrolysis of soy β-conglobulin was higher than that of soy globulin after the SPI was hydrolyzed for15min. The degree of hydrolysis of soy β-conglobulin and soy globulin both changed remarkable after the SPI was hydrolyzed for60min..(3)It was determined a method to prepare of SPI with high emulsibility and high foamability The method includes two-step hydrolysis with alkaline protease and papain. The optimal enzymatic hydrolysis conditions for alkaline protease were:alkaline protease dosage1.78%, hydrolysis time53.1min, hydrolysis pH9.1,hydrolysis temperature45.6℃. The optimal enzymatic hydrolysis conditions for papain were:papain dosage1.15%, hydrolysis time61.9min, hydrolysis pH7.1, hydrolysis temperature50.3℃.Under these conditions, the emulsibility of SPI was59.33m2/g which was increased by67.1%compared with blank sample, the foamability was243.41%which was increased by196.8%compared with blank sample.