Studies On The Construction Of Protease Engineering Strains And Modification Of SPI Applied To The Pork Sausage

Soy protein isolate is the most refined form of soy protein, containing eight essential amino acids. as a ingredient in the food ,it has extensive and important application, because of its high protein content and good functional properties in some food systems.Technology of modification can improve the functionality of soy protein isolate and nutrition, so that it can better apply in food. In this subject, we used genetic engineering techniques to produce high-yield strains of alkaline protease,and systematically studying the impact of modified process conditions on the functional properties of soy protein isolate, and haved in-depth discussions in the application of pigs Sausage, the main contents and conclusions are as follows:(1) The apr primers were synthesized according to apr E gene sequence with Bacillus subtilis genomic DNA, by studying cloning and expression with the Alkaline protease gene,we successfully constructed an alkaline protease high-yield strain.By inducing and identificating it,we determined the optimal induction time of 4 h, optimum induction temperature of 37℃, enzymatic activity of 18100 U·g-1 by using Folin method.(2) As indicators of the soy protein isolate gelation,we obtained optimum conditions by single factor experiments: SPI concentration of 12 %, the modified time of 3h, modified temperature of 30℃, pH 9.0 modified, the enzyme activity concentration of 600 U / g.We obtained the impact of degree of each factor to gelation of soy protein isolate: pH > substrate concentration> enzyme concentration. On the basis of single factor, using the second rotation design and response surface optimization, we got the production process of high gel of soy protein isolate:enzyme concentration of 563.32 U / g, pH 8.91, substrate concentration of 11.81%, the gelation of soy protein isolate of 10.46.(3) By analyzing texture of sausage, we got that when soy protein isolate of gelation is added to 4 %, the cohesiveness of sausagehe reaches maximum. Hardness,elasticity and chewiness gets maximum with protein addition level of 6 %.So we come to the conclusion that when the gelation of soy protein isolate addition level is 6 %, the sausage has the best texture features. The yield of sausages added to 8 % protein and starch is similar, and the sausages yield increases with the increase of addition of soy protein isolate.When soy protein isolate addition level is 6 %,the shape,color,feel,organization status, texture and taste is all improved by sensory analysis.