Effects of Purslane Extract on the Gel Properties of Isolated Porcine Myofibrillar Proteins under Oxidative Stress

This study examined the effects of purslane extract (PE) at varying concentrations (0, 0.05, 0.10, 0.15, 0.20, 0.40 mg/mL) on the gelling properties of pork myofibrillar proteins (MPs) under a Fenton oxidation system, with 0.02 mg/g BHA serving as a positive control. The results showed that both BHA and PE (with 0.20 mg/mL showing the optimal effect) could alleviate the deterioration of gel performance caused by oxidation, including suppressing the increase in cooking loss, the reduction in water-holding capacity, and the deterioration of gel texture characteristics. The MPs gel exhibited improved elasticity, cohesiveness, gumminess, and resilience when the PE concentration is 0.20 mg/mL. Rheological analysis revealed that the storage (G') and loss (G'') modulus of the gels reached their maximum values at a PE concentration of 0.20 mg/mL, indicating that the gel elasticity was optimal. The results of low-field nuclear magnetic resonance (LF-NMR) demonstrated that oxidation triggered significant migration of water molecules from an immobilized state to a free state in gels, and the addition of BHA and an appropriate concentration of PE mitigated this change. The immobilized water content in the gel was significantly higher (P < 0.05) at a PE concentration of 0.20 mg/mL than in the oxidized and BHA groups, indicating that PE effectively improved the gel network structure. Microstructural analysis demonstrated that the addition of 0.20 mg/mL PE under oxidative conditions provided optimally improved the three-dimensional network structure of of MPs gels. However, when the PE concentration increased further to 0.40 mg/mL, all gel properties deteriorated significantly, revealing a concentration-dependent regulatory effect of PE on MPs gel characteristics. Therefore, the addition concentration of PE must be carefully optimized in practical applications. These findings provide a theoretical basis for the application of purslane extract (PE) as a natural antioxidant in gel-type meat products.