Effect of Mg²⁺ on the Structure and Gel Properties of Mutton Myofibrillar Protein

In this study, the effect of Mg²⁺ on the physiochemical, structural and gel properties of mutton myofibrillar protein was studied. The results indicated that with an increase in Mg²⁺ concentration (0, 0.01, 0.02, 0.03, 0.04 and 0.05 mol/L), the physicochemical properties of mutton myofibrillar protein (MP) including solubility, emulsification activity, emulsion stability and particle size increased significantly (P < 0.05), the absolute value of the zeta potential decreased, the proportion of β-sheet increased significantly (P < 0.05), and surface hydrophobicity increased significantly (P < 0.05). The endogenous fluorescence intensity of tryptophan was largest at a Mg²⁺ concentration of 0.04 mol/L. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that the band intensity of myosin and relevant light chain proteins increased. Rheological analysis showed that the storage modulus (G’) first increased and then decreased. Compared with the control group, MP gel strength increased by 70.49% at a 0.03 mol/L Mg²⁺ concentration. Gel cooking loss and water-holding capacity (WHC) were negatively correlated with Mg²⁺ concentration (P < 0.05). Low-field nuclear magnetic resonance (NMR) analysis showed that with increasing Mg²⁺ concentration, immobilized water in the MP gel was transformed into free water. Microstructure observed by scanning electron microscopy (SEM) showed that the higher the concentration of Mg²⁺, the more porous the gel. Correlation analysis showed that Mg²⁺ concentration was highly correlated with the structure and gel characteristics of MP. Therefore, Mg²⁺ can significantly improve the gel properties of mutton MP.