Effect of different heating process on the protein solubility and urease activity of proteins in soymilk

In order to explore the effect on protein characteristics of soymilk by heating processes including traditional heating, microwave heating and high temperature with pressure heating, the protein NSI value, urease activity, surface hydrophobicity, free sulfhydryl and transmission electron microscope were studied. The results showed that, compared with the NSI value of protein of raw soymilk was 69.03% ± 0.82%, the NSI value of protein was 81.62% ± 1.07% by traditional heating at 90 ℃ for15 min.After microwave heating, the NSI value of protein was 75.35% ± 0.65% at 650 W for 40 s.The NSI value of protein of high temperature with pressure heating was 91.31% ± 1.5% at 100 ℃ for 3 min.Urease activity was inhibited by the processing of traditional heating, microwave heating, high temperature with pressure heating.Compared with raw soymilk, the free sulfhydryl content of protein was remarkably declined by traditional heating, microwave heating and high temperature with pressure heating ( p < 0.05) , but the surface hydrophobicity of protein was remarkably higher ( p < 0.05) , respectively. The microscopic structure analysis of the soymilk showed that soymilk protein and oil droplets cosolvent had uniform distribution and better dispersion.Thus, the improvement of protein solubility of soymilk after different heating processes was achieved by the deep change of protein structure.