Mechanisms of rutin-mediated protection of grass carp myofibrillar protein under combined heat and linoleic-acid oxidation

During thermal processing, heat and unsaturated lipids oxidize fish myofibrillar protein (MP) and weaken gel quality. We built a dual-oxidation model with grass carp MP combining heating and linoleic acid (LA), and evaluated rutin at 0-160 μmol g -1 protein. Rutin in 20–40 μmol g -1 protein lowered carbonyls, limited aggregation, maintained a higher α-helix proportion, and gave gels with higher strength, elasticity, and water-holding capacity (WHC). In contrast, rutin greater than 40 μmol g -1 protein increased particle size and turbidity, producing coarse networks with lower WHC and strength. Spectroscopy and thermodynamics showed mainly static, hydrophobic binding of rutin to oxidized MP to form stable complexes; docking supported higher affinity for MP than LA, suggesting site competition. In summary, these results elucidate how rutin mitigates oxidation of grass carp myofibrillar protein under concurrent linoleic acid and heat, and provide practical guidance for its application in thermally processed fish products. • Dual-oxidation model combining heating and linoleic acid for grass carp MP • Rutin (20-40 μmol/g) reduced oxidation, preserved structure, and improved gel quality • Excess rutin (>40 μmol/g) caused over-crosslinking and coarser gel networks • Rutin bound noncovalently to MP mainly through hydrophobic and hydrogen interactions