A Preliminary Study Of Soybean Protein On The Structure And Surface Activity Relationship

Soy protein7S,11S was extracted by acid-alkali precipitation and the surface activityproperities was measured to study the relationships between proteins structure andsurfactants of soybean protein. The effect of disulfide bonds on the structure and surfaceactivity of soybean protein was researched by disulfide bonds opening. Finally, the twomajor soy protein disulfide-containing ingredient basic7S globulin and soybean globulinare simulated by molecular dynamics simulations to explain the effect of soy proteindisulfide bonds on the surface-active.The mian results of the paper are showed as followed:1. Soy protein7S,11S was extracted by acid-alkali precipitation. The extraction ratewas analysised by gel electrophoresis. GIS1D gel analysis system displays digital showedthat the7S and11S extraction rate was61.2%and62.5%. Finally the surface activity wasmeasured and the results are followed: Isolated soy protein and its components havedifferent properties.7S has a better emulsification and emulsification stability.7S has abetter foaming and foaming stability than11S. The ultraviolet spectrum scans and thefluorescence spectrum scans showed that the phenylalanine content of11S is highest, thetyrosine and tryptophan content is lower.2. Peracetic acid was used to oxidate soybean protein to prepare surfactant, the effectof disulfide bonds on the structure and surface activity of soybean protein was researched.The amount of peracetic acid, temperature and time was investigated. The optimumconditions of peracetic acid oxidation of soybean protein were as follows: the amount ofperacetic acid:20%; temperature:-10?; time:4h by orthogonal test. At this time,disulfide bond was opened68.53%, foaming properties of soy protein was improved60.17%, emulsification was increased100.1%. Surfactants improved. Scanning electronmicroscopy showed that: the internal oxidation of the modified soy protein appears moregaps, indicating that soy protein structures in the oxidation process changed.3. Molecular dynamics simulation of two major disulfide-containing components insoybean: basic7S globulin and soybean globulin. Analyze the effect of soy protein surfaceactivity by disulfide bonds. The simulation results showed that: a disulfide bond breakagelead protein serious instability, the breakage of iner disulfide bond is the main reasonwhich make the protein instability. The external disulfide bonds have a poor influence tothe instability. The structure of the basic7S globulin changed after the disulfide bondbreakage, the internal hydrophobic residues exposed after the disulfide bond breakage, which lead the surface tension reduce. Surfactants improved.The breakage of the outerdisulfide bond is the main reason which make the surface tension reduce. After breakingdisulfide bonds, the dynamics parameters of basic7S globulin and soybean globulinchanged. But it has no effect on protein secondary structure. Protein tertiary structurechanged.