The Stability Of Mixed Protein System

In this paper, soybean protein isolate(SPI), casein(CS), whey protein isolate(WPI) and milk protein concentrate(MPC) were used as material, SPI mixed with CS, WPI, MPC respectively. Researched on mixed protein system, the interaction between two mixed proteins had the stability system of mixed protein. Centrifugal sedimentation rate, centrifugal suspension than, stability coefficient R and amount of natural precipitation as the evaluation indexes. Optimization formula the mixed protein system- between the SPI and three kinds of milk protein-respectively. Provide the theoretical and technical support for Mixed animal and plant protein products industry. The main findings are as follows:(1)SPI+CS protein mixed system optimization formula was: the ratio of SPI and CS was 1:1, the total protein concentration of was 1%, the concentration of Ca2+ was 3mmol/L. SPI+WPI protein mixed system optimization formula was: the ratio of SPI and WPI was 2:1, the total protein concentration of was 2%, the concentration of Ca2+ was 3mmol/L. SPI+MPC protein mixed system optimization formula was: the ratio of SPI and MPC was 2:1, the total protein concentration of was 2%, the concentration of Ca2+ was 2mmol/L.(2)SPI+CS protein mixed system optimal conditions was: the p H was 7, the heat treatment temperature was 100℃ 15 min, under the conditions of 400 W 50℃ ultrasonic treatment was 30 min. SPI+WPI protein mixed system optimal conditions was: the p H was 7.5, the heat treatment temperature was 90℃ 15 min, under the conditions of 400 W 50℃ ultrasonic treatment was 20 min. SPI+MPC protein mixed system optimal conditions was: the p H was 7, the heat treatment temperature was 90℃ 15 min, under the conditions of 400 W 50℃ ultrasonic treatment was 25 min. Under this conditions, the kinds of three mixed proteins system achieved stable equilibrium.(3)The experiment explored particle size analysis, zeta potential, transmission electron microscopy(TEM) of three kinds of mixed protein system. Analysis of the Interaction between the two proteins and their impact on system stability. The results show, two kinds of mass ratio, the protein concentration, the concentration of Ca2+, p H, ultrasonic treatment and heat treatment had a certain influence on the the stability mixed protein. After a series of processes that p H, ultrasonic treatment and heat treatment, the stability coefficient and centrifugal suspension ratio of mixed protein system has a certain degrees of improvement, centrifugal sedimentation rate has decreased, the particle size analysis has increased., the absolute value of the zeta potential has increased. As the particle proteins in solution repulsion increased, more conducive to protein particles in a dispersed state. Transmission electron microscopy(TEM) observation, Compared with untreated hybrid protein system, After treatment of formulation optimization, adjust the pH, ultrasound and heat the microstructure of the mixed protein solution has changed, protein molecule chain was opened, macromolecular protein of protein system occured depolymerization and recombine; particle size analysis shows that the protein molecule were more uniform distribution in mixed protein system. So as to enhance the stability of the system.