Ultrasound-assisted Soybean Protein Isolation Improve Emulsification Of Egg Yolk

Egg yolk(EY)is a natural emulsification system formed by the assembly of water,lipids and protein.It is often used as an important component of emulsified foods such as salad dressing and mayonnaise.However,egg yolks are easily affected by processing factors,causing delamination and oil separation.Therefore,finding ways to improve the emulsification of egg yolks and studying the emulsifying properties of modified egg yolks play an important role in broadening the application of egg yolks in the food industry.This thesis uses soy protein isolate(SPI)supplemented with ultrasonic treatment to explore the effects of different ultrasonic powers on soy protein isolate's improvement in the emulsification of egg yolk emulsion and the performance of egg yolk protein,combined with fourier transform infrared spectroscopy(FTIR)and polyacrylamide coagulation.Gel electrophoresis(SDS-PAGE),interface protein adsorption,surface hydrophobicity,zeta potential and other methods,studied the effect of SPI combined with ultrasonic treatment on the structure and surface properties of egg yolk particles and low-density lipoprotein.The results of the study are as follows:(1)Using emulsification activity,emulsification stability,particle size,interface adsorption capacity,the effect of different ultrasonic power on the improvement of SPI emulsification of egg yolk was explored.The results show that adding SPI to EY can significantly improve the emulsification activity(EAI)and emulsification stability(ESI)of EY(p<0.05);ultrasonic treatment can further improve the emulsification of EY-SPI,under 150 W ultrasonic treatment,the ESI of the EY-SPI emulsion was significantly higher than that of the other groups(p<0.05),the particle size and emulsification index were significantly reduced(p<0.05),the amount of interface protein adsorption was significantly increased(p<0.05),and the electrostatic repulsion was significantly enhanced(p<0.05),the emulsion droplets were more evenly distributed.(2)Under the condition of ultrasonic power of 150 W,the effect of SPI supplemented by ultrasonic treatment on the emulsification characteristics of egg yolk particles was further studied.The results show that adding SPI to the egg yolk particles can significantly improve the emulsifying activity and emulsification stability of the egg yolk particles(p<0.05);SPI supplemented by ultrasonic treatment can effectively improve the emulsification of the egg yolk particles,so that the ESI and EAI of the egg yolk particles can reach the largest,the highest protein adsorption at the oil-water interface in the emulsion,the strongest electrostatic repulsion between oil droplets,and the smallest emulsion particle size.The results of FTIR showed that SPI supplemented with ultrasonic treatment,the hydrogen bond between the yolk particles was strengthened,the surface charge was exposed,and the absolute value of the zeta potential increased.The increase in calcium ion concentration indicates that SPI is supplemented by ultrasonic treatment,the yolk particles are dissociated,and the calcium phosphate bridge connecting high-density lipoprotein(HDL)and phosphoprotein(Pv)is destroyed,exposing many groups and enhancing the surface The density of the charge.(3)The effect of SPI supplemented by ultrasonic treatment on the emulsification of low-density lipoprotein(LDL)of egg yolk was studied.The results of SEM and surface hydrophobicity show that SPI is supplemented by ultrasonic treatment,the aggregation state of LDL changes,the protein particles become smaller,the surface becomes softer and stretchable,and the hydrophobic groups and ionizable groups are exposed.The results of FTIR showed that ultrasonic treatment assisted SPI without affecting the secondary structure of LDL.Fluorescence microscope and particle size analysis showed that the particle size of the emulsion was significantly reduced by SPI supplemented by ultrasonic treatment,the distribution of emulsion droplets was uniform,and the emulsification stability and emulsification activity of LDL reached the maximum.