The Research Of Soybean Dregs Protein Extraction, Structure And Properties

The researching on soybean by-products domestic and foreign are concentrated on soybeanafterextracting oil wich are soybean meal, but the soybean residue in this article is by-products that haveprocessed tofu, soymilk and skin of beancurd, etal, people tend to ignore such by-product utilization.Domestic soybean food industry annually produces wet residue millions of tons, wich contain higherconcentrations of polysaccharides from soybean residue, dietary fiber, isoflavones, protein and othernutrients, the resources of soybean residue were used by the advanced technology and prevented thepollution of the environment, wich is the contemporary scientists need solve problems.In order to improve soybean dreg，sprotein yield, alkali extraction, ultrasonication and acidprecipitation were used for extraction of soybean dreg，s protein. Material-liquid ratio, ultrasonic timeand ultrasonic power were main factors with protein yield as response value by ultrasonic treatment.The response surface and excellent frequency chosen analysis by Design-Expert showed that the orderof factors which affected the soybean dreg，s protein yield was ultrasonic time> ultrasonic power>temperature> material-liquid ratio. Each parameter values range were material-liquid ratio20.5～22.1g/mL,temperature51.0～53.4℃, ultrasonic time28.8～30.7min, ultrasonic power398.1～399.3Wwhile the soybean dreg，s protein yield was high.The yield of soybean dreg，s protein yield could reach80.19%after repeated verification tests.Almost every kind of biomass structure determines properties,so firstly preliminarily identificatedthe internal structure of the protein. Detecting thermal stability of soybean residue protein,both of thedenaturation temperature were98.65℃,the enthalpy values respectively is20.09J/g and19.39J/g;thoughthe analysis amino acid composition of soybean residue,it shows the yield of glutamateis about17.65%,aspartic acid is about9.91%, and then after that is leucine at about7.58%;when pH is5.5,thehydrophobic of soybean residue protein respectively reaches the maximum value1265,1120;detectingthe SDS-PAGE gel electrophoresis of soybean residue protein,it shows the electrophoresis in separatinggel is similar, molecular weight had no change, the differences of colour shades are notobvious;detecting the secondary structure of soybean residue protein by FT-IR,it finds ultrasonic timehave greatly impact on the α-helix and the β-effect of folded which is soybean residue protein secondarystructure.The soybean residue protein functional properties including soybean residue protein solubility,absorption of oil, emulsion and emulsion stability were testing. Comparing the PDI and NSI of soybean dreg，s protein by the single alkali soluble acid sinkingmethod with the ultrasonic assisted alkali soluble acid sinking, latter was more than the former,theresultof orthogonal test is when the concentration of soybean residue protein is6%,pH is11,the temperatureis50℃, PDI values is up to50.26; when the concentration of soybean residue protein is6%,pH is10,thetemperature is40℃, NSI values is up to33.56. In the absence of other factors affecting cases,theconcentration of soybean residue protein have significant impacts on the PDI and NSI, pH is affectedsignificantly on the NSI value of soybean dregs protein by ultrasonic-assisted extraction method.Itshows that ultrasonic treatment can undermine the degree of integration between the protein and fiber,make it easy for some proteins to dissolve, far greater than the quantity of insoluble,so the degenerationdegree is not significant; and the research provides the theoretical basis and reference for functionalproperties of soybean dregs protein.With pH value, temperature and time as the single factor, soybean residue protein absorption of oil,emulsion and emulsion stability as the goal value.The research shows that when pH is7, temperature is70℃,the time is40min, oil absorption derived of soybean residue protein by ultrasonic is up to4.10mL/g; when pH is11, the temperature is40℃, the time is50min, the emulsion and emulsionstability of soybean residue protein by ultrasonic-assisted is87.22mL/g and92.54min.Literature searches have yet to find any research on extracting protein from soybean dregs byultrasonic-assisted;it provides a theoretical basis for comprehensive utilization of the soybean residue,adds new research ideas to increase the rate of the extraction of soybean residue protein, band providethe basic theory research on functional properties of soybean residue protein.