Changes in Transglutaminase Activity and Its Contribution to Gelation Properties of Low-Salt Myosin Under Ultrasound

This study explored the changes in cross-linking of low-salt myosin mediated by microbial transglutaminase (MTGase) under high intensity ultrasound (HIU). HIU activated the fish endogenous transglutaminase by 14.11%. Meanwhile, HIU induced the conformational changes in low-salt myosin with decrease of α-helix and increase of β-sheet structures. At 0.1 mol/L salt, compared to solely treated MTGase/solely treated myosin, the most ε-(γ-Glu)-Lys bonds were formed in HIU-treated MTGase + myosin, evidenced by the lowest solubility. Correspondingly, the G’ showed the highest increase rate. Consequently, the samples formed regular and continuous protein matrix structures. Specifically, the microstructures of HIU-treated MTGase + myosin samples at 0.1 mol/L salt were even more compact than those of control samples at 0.3 mol/L salt. Besides, HIU-treated MTGase + myosin improved the water holding capacity by 18.28%. In summary, HIU promoted the cross-linking between low-salt myosin mediated by MTGase through activating the enzyme, improving substrate dispersion, or both, with the largest improvement degree observed for HIU-treated MTGase + myosin group.