Study On The Construction And Main Properties Of Soybean Protein Isolate And Whey Protein Mixture System

Soy Protein Isolates（SPI）contain eight essential amino acids,and Whey Protein（WP）contains many bioactive components.The ratio of essential amino acids to total amino acids is close to the international reference mode.Soy protein isolate and whey protein double protein have the advantages of both animal protein and plant protein,and can achieve nutritional complementarity.In this study,soybean protein isolate and whey protein were used as raw materials,and international nutritional dietary standards were used as reference values.Grey correlation analysis method was used to determine the optimal double protein ratio conforming to human nutritional evaluation,and fuzzy recognition method and amino acid scoring method were used to study their nutritional char acteristics.Single factor test and response surface methodology were used to design and optimize the optimal treatment conditions for the stability of the two-protein solution system,and the properties of the optimized optimal ratio of two-protein and single protein were compared.The main research results are as follows:SPI:WP=3:7 was determined as the optimal double protein ratio based on the essential amino acid pattern stipulated in FAO/WHO mode as the reference value.The nutritional complementarity of the double protein was studied based on the optimal ratio.The protein closeness of the double protein in FAO/WHO mode was 0.9894,and that of the whole egg protein mode was 0.9928.The ratio coefficient score（SRC）of amino acids was 79.43,and the digestibility was 73.12%in vitro by simulating human gastrointestinal environment,which was in line with the range of human digestion and absorption.The amino acid score modified by digestibility was 82.64,and the amino acid score modified by digestibility was higher than the other two single proteins.The optimal amount of water was determined to be 50 m L/5 g,and the influences of p H value,Ca²⁺concentration,heat treatment temperature and ultrasonic treatment time on the stability of the two-protein solution were investigated by single factor test.Response surface method was used to optimize the optimal treatment conditions for the stability of the two-protein solution:Under the conditions of p H 7.2,Ca²⁺concentration of 4.1 mmol/L,heat treatment temperature of 80℃and ultrasonic treatment time of 15 min,the stability coefficient of the two-protein mixed solution was 0.7807,which was significantly higher than that of the untreated group.Through the comparative study of the properties of double protein and single protein,the solubility,foaming ability and emulsification stability of double protein are in the middle of the two proteins,emulsification activity is higher than single protein,gel properties are better than single protein,with better function.The surface viscosity of the solution gradually decreases and tends to be stable,and the shear stress gradually increases.The fitting equation isτ=0.01152γ^0.56713,R²=0.9935,the viscosity coefficient is 2.12486 Pa.s,the fluid index n=0.50694.It indicates that the two-protein solution is a pseudoplastic fluid.Compared with single protein,the two-protein solution had the best color sensitivity and taste sensitivity,and the Zeta-potential,surface hydrophobicity and surface sulfhydryl groups increased,while the particle size decreased,indicating that the two-protein solution had higher stability.The free radical scavenging ability was increased,and the antioxidant activity was stronger.The total number of bacteria,coliform bacteria and pathogenic bacteria all meet the national food safety standards.