Protein-glutaminase-mediated functional modification of fish myofibrillar protein and its gelation mechanism

Protein-glutaminase (PG; EC 3.5.1.44) effectively enhances protein solubility and functionality through targeted deamidation. Current strategies for improving textural properties of low-sodium myofibrillar protein (MP) gels predominantly rely on salt addition, which conflicts with health-driven sodium reduction demands. This study demonstrated that PG-induced deamidation significantly increased the net negative charge of MP, promoting filament dissociation and consequently enhancing solubility in neutral aqueous solutions. Volatile compound profiling revealed that deamidation substantially modified the flavor characteristics of MP, particularly reducing key fishy odor compounds, such as hexanal, nonanal, and 1-octen-3-ol. The deamidated MP (DMP) exhibited unique thermally reversible gelation behavior that could be melted through heating and reconstituted into a stable gel upon refrigeration. Notably, DMP gels showed improved gel properties, including water holding capacity (WHC) and springiness, along with improved umami taste perception. Sensory evaluation confirmed intensified umami perception in DMP gels, correlating with increased umami amino acid levels. These findings established a theoretical foundation for developing low-sodium MP gel products with improved textural properties, reduced off-flavors, and enhanced palatability.