Abstract: To investigate the effect of static magnetic field (SMF)-assisted freezing on water distribution and myofibrillar protein (MP) structural properties in thawed beef, this study employed different magnetic field intensities (0, 2, 4, 6, 8, 10 mT) to assist beef freezing at -20 ℃. After the internal temperature reached –18 ℃, the beef was thawed in air at 4 ℃ for 24 hours. Subsequently, beef quality, myofibrillar protein properties, protein oxidation, and protein conformation were measured. Results indicated that compared with the 0 mT group, magnetic field treatment significantly shortened the phase transition time and freezing time of beef (P < 0.05), thereby significantly improving post-thaw beef quality. Magnetic field treatment increased the content of immobilized water and enhanced water distribution uniformity in beef. Specifically, magnetic field treatment at all intensity levels except at 8 mT significantly reduced thawing loss (P < 0.05). Compared with the non-magnetic field frozen group, the magnetic field-treated groups exhibited significantly increased myofibrillar protein solubility (P < 0.05) and reduced turbidity (P < 0.05); protein particle size decreased in the 2 mT group, and surface hydrophobicity was significantly lowered in the 2, 6, and 8 mT treatment groups (P < 0.05). Moreover, magnetic field treatment effectively suppressed oxidative protein damage. Compared with the 0 mT group, the magnetic field-frozen groups exhibited significantly reduced carbonyl content (P < 0.05) and the total sulfhydryl content was significantly increased in all groups except the 4 mT group (P < 0.05). Protein conformation analysis revealed that the β-sheet content decreased as magnetic field strength increased. Magnetic field treatment increased the intrinsic fluorescence intensity and ultraviolet-visible absorbance, with the 2 mT group exhibiting the least disruption of MP tertiary structure. Taken together, magnetic field treatment reduced freezing damage in beef and reduced the oxidation and denaturation of MP, thereby enhancing the eating quality of frozen beef. The 2 mT magnetic field exhibited the most effective quality preservation during freezing.

Key words: static magnetic field-assisted freezing; beef; myofibrillar protein; beef quality