Mechanism of Ultra-high Pressure and TG Enzyme Modified Thermally Induced Gels of Egg White Protein

Aiming to improve the gel property of egg white proteins, in this research, taking egg white protein (EWP) as the research object, the changes in texture, water-holding ratio, molecular forces, Fourier transform infrared chromatography, circular dichroism spectrum, particle size, potential, sulphydryl content, surface hydrophobicity, and scanning electron microscopy were analyzed to explore the mechanism and structural changes of heat-induced gel of EWP after the treatments of Ultra-high Pressure (UHP), Transglutaminase (TG) and Ultra-high Pressure Synergistic Transglutaminase (UTG). The results showed that the hardness, elasticity and water holding capacity of UHP-EWP, TG-EWP and UTG-EWP were all improved, and hydrophobic interaction was the main force to maintain gel. The α-helix content of UHP-EWP, TG-EWP and UTG-EWP decreased, while the β-fold content increased. The average particle size and absolute potential of UHP-EWP decreased, while the changes of TG-EWP and UTG-EWP were opposite. The content of free sulfhydryl groups in UHP-EWP, TG-EWP, and UTG-EWP increased, the content of total sulfhydryl groups decreased, and the surface hydrophobicity increased. The gel structure was more compact and smooth, and the flatness was improved. This research provides a theoretical basis and research ideas for the heat induced gel modification of EWP.