Frozen storage-induced structural transitions govern the flavor-binding capacity of tilapia myofibrillar protein

Flavor deterioration in frozen tilapia is closely linked to conformational changes in myofibrillar protein (MP). This study dynamically investigated the effects of frozen storage (0-60 days) on MP structure and its binding to four characteristic flavor compounds (heptanal, hexanal, nonanal, 1-octen-3-ol). The binding capacity exhibited a time-dependent biphasic trend, peaking at day 10 before declining. Aldehydes, especially nonanal > heptanal > hexanal, were bound with significantly higher affinity than 1-octen-3-ol. The initial enhancement (0-10 days) was driven by MP unfolding, which caused a 241.07% increase in surface hydrophobicity, thereby strengthening hydrophobic interactions. In contrast, prolonged storage (30-60 days) induced protein oxidation (50.48% sulfhydryl loss) and aggregation, leading to a 51.03% reduction in hydrophobicity and an α-helix-to-β-sheet transition. Fluorescence quenching and molecular docking confirmed that heptanal binding in fresh MP was mediated by hydrophobic interactions and hydrogen bonds, whereas prolonged storage shifted the driving force toward weaker electrostatic interactions, reducing binding stability. These findings reveal a structural mechanism underpinning flavor deterioration, providing a mechanistic basis for targeted quality control strategies in frozen aquatic products.