Composite Enzyme To Amide 11S Globulin Modification Mechanism

Natural 11S soybean globulin molecules containing a large number of hydrophobic groups, which is the main reason leading to its limitation in the food industry.Research to improve the method of high surface hydrophobicity and discuss the modification mechanism,is an important topic in the field of 11S globulin. This experiment mainly studied the changes of 11S' internal structure under different degrees of enzymatic hydrolysis, from the molecular level and the microstructure, discussed the modification mechanism of 11S globulin.Firstly, 11S globulin was extracted by isoelectric point cold extraction method from soybean protein. Secondly, used Alcalase and pepsin, on the basis of single enzyme hydrolysis, according to the method of step by step to complex the two different enzymes. The results showed that under the same conditions, changed the order of the two enzymes, the degree of hydrolysis only has little change, and it didn't affect the results of the experiment. Optimum process parameters:used pepsin to hydrolyze 1 h under the condition of temperature 35 ?, pH 3.0, enzyme adding amount of 1500 U/g, then adjusted to a temperature of 50 ?, pH 10, Alcalase adding amount of 12000 U/g, hydrolyzed 5 h and killed enzyme. Obtained the degree of hydrolysis was 19.65% of enzyme solution. And it can be seen from the results of compound enzyme hydrolysis, this method is more beneficial to the hydrolysis of 11S soybean globulin. Further added transglutaminase, used fluorescence spectrophotometer to determine the surface hydrophobicity of the enzymatic hydrolysate of soybean 11S globulin, used the response surface test to discuss the four single factors which affected molecular crosslinking and interaction between each factors. Finally, get three groups of optimal combination which has lower hydrophobicity. The samples were prepared by spray drying.By scanning electron microscopy, the samples' particle size, morphology and aggregation had been observed, during protease enzyme-complex polymerization process,11S globulin molecules change from compact arrangement?maldistribution to uniform size and loose distribution, the irregular surface of the potholes has improved, and after the polymerization, the small particle state after compound enzymatic hydrolysis has changed, the aggregation degree between the molecules is greatly increased, and the adhesion state of the particles can be clearly seen.By means of X-ray, it can prove that the extracted 11S globulin has little crystal, but they are destroyed after fully enzymatic hydrolysis by complex enzymes, which leads to the disappearance of diffraction peaks, but after crosslinking reaction, the original absorption peaks appear again but the intensity has weakened, reflects the overall amorphous.The thermal denaturation temperature and enthalpy change had been determined by DSC, results show that, the thermal stability of the modified 11S globulin increased first and then declined, but overall was the upward trend, due to the Tp values and surface hydrophobicity exists significant negative correlation, so the surface hydrophobicity decreased first significantly and then increased, but overall improve the high hydrophobic surface properties of natural 11S globulin.The changes of amino acid composition and content of modified 11S globulin had been known by amino acid analyzer, modification improved the content of essential amino acid, to a certain extent, the nutritional value of 11S globulin increased. Meanwhile, it can be seen from the changes of total hydrophobic amino acid content in the sample, the surface hydrophobicity reduced greatly first and then increased, but still lower than before, indicates that this modified method succeeded in improving the characteristics of high surface hydrophobic property of natural 11S globulin.This experiment had been revealed the internal structure changes of modified 11S globulin from different point of views by 4 kinds of high technology means, proves that the surface hydrophobicity is decreased together, and has carried on the quantitative assurance in order to get the ideal 11S globulin. The results of this study provide a lot of theoretical support for the further research of 11S globulin and industrial production of specific functional properties soy protein powder.