Effect of Magnetic Field Assisted Freezing on the Properties and Quality Characteristics of Myofibrillar Protein in Prepared Pork

To investigate the effects of magnetic field-assisted (MF) freezing on the protein properties and quality characteristics of prepared pork, experiments used fresh prepared pork as the experimental material. The effects of conventional freezing (refrigerator freezing at −20±2 ℃) and three types of magnetic field-assisted freezing (at magnetic field intensities of 3, 4, and 5 mT, at a temperature of −20±2 ℃) on freezing rate, thawing loss, centrifugal loss, pH, TBARS value and myofibrillar protein (MP) characteristics of the prepared pork were compared. The results showed that the freezing time was significantly reduced under MF treatment compared to the control group (238 min), with reductions of 132.25, 143.75, and 115.25 min, respectively. Additionally, the various MF treatment groups exhibited a significant inhibition of protein oxidative denaturation. Specifically, total sulfhydryl content was significantly higher than that in the control group, while carbonyl content and surface hydrophobicity were significantly lower than that in the control group (P<0.05). Moreover, the relative of α-helix in the MP secondary structure was notably higher, reaching 55.36% for the MF4 group, compared to 16.33% for the control group. The total protein solubility for the MF groups was also significantly higher than that of the control group (P<0.05). In comparison to the control group (with thawing loss of 6.82% and centrifugal loss of 26.11%), the water-holding capacity of the muscle significantly increased after MF treatment (thawing loss of 4.43% for MF4, centrifugal loss of 18.88%) (P<0.05). Moreover, at a magnetic field intensity of 4 mT, both protein and lipid oxidation levels were at their lowest, and the freezing time was also minimized. In comparison to the other freezing methods, the protein's secondary structure exhibited greater stability. Consequently, the 4 mT magnetic field-assisted freezing treatment is more suitable for the freezing of prepared pork.