Research On The Structure And Properties Of Soy Protein Particles Based On Different Preparation Methods

Soy protein isolate is a high-quality plant protein.Compared with milk protein or animal protein,its solubility is poor.Therefore,its functional properties are easily restricted in food processing.This article uses twin-screw extrusion technology and high-pressure homogenization technology,combined with different drying methods to prepare nano-level soy protein particles.The effects of different preparation conditions on the functional and structural properties of soy protein particles were investigated,and the structure-activity relationship was established.The soy protein particle dispersion is used as the raw material to prepare the protein film,and the difference in the film-forming characteristics of the protein particles of different particle sizes obtained under different preparation conditions is explored.The results show:(1)The soy protein particles obtained by the twin-screw extrusion technology have a particle size of about 21 times smaller than that of natural soy protein isolate,the solubility is increased by 71%,the emulsification activity is increased by about 57.43%,and the emulsification stability is increased by about 98%,and the oil retention increased by 23.72%.The protein morphology is transformed from the inwardly concave spherical aggregation state to the fragmented state and the surface is smooth,which destroys the spherical compact structure of the protein molecule,exposes the hydrophobic groups,and enhances the electrostatic repulsion between particles.After infrared fitting,?-sheets can be obtained.And the random coil is converted to ?-helix and ?-turn.(2)When using high-pressure homogenization combined with freeze-drying to prepare soy protein particles,when the pressure is 100 MPa,the particle size is reduced by 1632.50% compared with natural soy protein isolate,the solubility is increased by172.98%,and the emulsifying activity is increased by about 77.82%.When the pH is10,the particle size reaches theminimum and is reduced by 40%,the solubility is increased by 25%,the emulsification activity is increased by 105%,the emulsification stability is increased by about 20%,and the water holding capacity is increased by120%.The protein particles have a highly open pore structure,a large number of hydrophobic groups are exposed,the surface hydrophobicity increases,and the electrostatic repulsion increases.(3)Using high-pressure homogenization combined with spray drying to obtain soy protein particles,when the pressure is 80 MPa,the particle size is reduced by 7.7 times compared with natural soy protein isolate,the solubility is increased by 160%,the emulsifying activity is increased by about 100%,and the pressure is 80 MPa.At 60 MPa,the emulsion stability increased by about 71%,and the oil retention increased by20.41%.When the pH is 10,the particle size reaches theminimum value and is reduced by 0.56 times,the solubility is increased by 40%,the emulsification activity is increased by 56.75%,the emulsification stability is increased by about 29.44%,and the water holding capacity is increased by 64%.The protein particles maintain a spherical and concave surface.The greater the pressure,the more protein particles under the same area.(4)The protein film was prepared with the soy protein particle dispersion as the raw material.With the increase of homogenization pressure,pH and material ratio,the expansion rate of the protein film decreased by 43.63%,145%,107%,and the water solubility decreased by 25.81%,77.14%,60.40%,thus improving the water resistance of the protein film.After the high-pressure homogenization treatment,the molecular force between the proteins is enhanced,and the exposed hydrophobic groups and sulfhydryl groups can form new disulfide bonds,which can form a uniform threedimensional network membrane structure.Therefore,with the homogenization pressure,pH and materials,the tensile strength of the protein membrane increased by 50%,250%,and 147%,and the elongation at break increased by 50%,394%,and 312%.The micronized soy protein isolate provides new thinking and new ideas for the optimization of functional properties and structure.