Construction Of High Emulsifying Properties Of Soy Protein Isolate Modified Gene Engineering Strains And The Application Research Of Modification Of SPI

Soy protein isolate rich in protein, with high nutritional value, and it also has many important functionalproperties, these properties make soy protein isolate have a broader application in food. And because of thegood price advantage and potential functional properties of soybean, soy protein structure modification as wellas to further improve the functional properties has been a hot topic of research at home and abroad. The subjectto Bacillus subtilis gene as template, we used genetic engineering techniques to produce strains of neutralprotease, Modified by the neutral protease produced by soy protein isolate, The modification process by asingle factor and the rotating combination design principles, and products used in ice cream, the determinationof the optimal replacement rate in its ice cream. The main contents and conclusions are as follows:(1)Experiment with genomic DNA of Bacillus subtilis as template, according to nprE gene sequence,synthesis of primers, the neutral gene was amplified by PCR, and inserted into the vector pGM-T in thedigestion and sequencing to identify the correct recombinant plasmids were digested, ligation,constructedexpression plasmid pET-npr, The recombinant plasmid was then transformed into E.coli BL21(DE3), wesuccessfully constructed an neutral protease strain.and induce and identificate it. Enzymatic activity of was257.63U/mL..(2) As the main raw material, Soy protein isolated was maken use of to hydrolyze by the neutral proteaseenzyme. The effects of pH valueand, mass fraction of soybean protein isolated, enzyme dosage, reactiontemperature and hydrolysis time on emulsifying activity were investigated by single factor and Centralcomposite design In the meantime, Response Surface Methods was adopted to analysis the optimalfermentation conditions. The results was also demonstrated that the optimal conditions as follows: value of pHwas7.1, mass fraction of soybean protein isolated was5.6%,enzyme dosage was5000U/mL, reactiontemperature was51℃, and hydrolysis time was117min respectively. With these conditions, emulsificationactivity of soy protein isolated was reached1.390, emulsion stability was reached135.67min.(3) The influence to the quality of icecream is explored when non modified soybean protein isolate andemodified soybean protein isolate is partly replace Milk powder.Results shows,when the modified soybeanprotein isolated replacement rate is5%，Viscosity, swelling, and sensory quality of the ice cream were thehighest, while the minimum of the melting rate, this condition produced the most excellent ice cream.