Mild oxidation- and L-Cysteine-mediated disulfide bond modulation restores gelation performance of freeze-damaged myofibrillar protein.

Freeze-thaw-induced protein oxidation and aggregation detrimentally compromise myofibrillar protein (MP) gelation. This study systematically elucidated the regulatory role of L-Cysteine (L-Cys, 0-450 μmol/g) in the gelation behavior of native and freeze-thaw-damaged MP (FMP) under both non-oxidative and oxidative conditions. L-Cys treatment elicited extensive, concentration-dependent structural remodeling, culminating at 300 μmol/g, as evidenced by markedly elevated fluorescence intensity, surface hydrophobicity, and disulfide bond formation, insinuating enhanced thiol-disulfide exchange and intermolecular interactions. Notably, these effects were further potentiated under mild oxidative stress. Consequently, L-Cys supplementation, especially when combined with mild oxidation, accelerated gelation kinetics and triggered a favorable secondary structural transition from α-helix to β-sheet, while driving disulfide bonds toward a highly stable g-g-g conformation. This structural realignment facilitated the construction of a more compact, interconnected, and homogenous gel network with superior water-immobilizing capacity. Ultimately, the resultant gels exhibited markedly improved viscoelasticity and mechanical strength, effectively counteracting freeze-thaw-induced functional deterioration.