Oxidation-Initiated Myosin Subfragment Cross-Linking and Structural Instability Differences between White and Red Muscle Fiber Types

Both white and red muscles are commonly used in meat processing, and protein cross-linking, which may be affected by oxidants, is a key factor affecting the product quality. In this study, myofibrillar proteins (MPs) extracted from postrigor chicken Pectoralis major (PM, predominantly white) and Gastrocnemius (GN, predominantly red) muscles were subjected to a •OH-oxidizing system (10 μM FeCl₃, 0.1 mM ascorbic acid, with 0, 5, 10, or 20 mM H₂O₂) at pH 6.2, 4 °C for 18 h. The solubility of nonoxidized (control) PM MPs (63%) was higher than that of control GN MPs (41%). After oxidation with •OH generated at 5 mM H₂O₂, protein solubility decreased by 46% and 21% for PM and GN, respectively, due to aggregation. Chemical and electrophoretic analyses indicated H₂O₂-dose-dependent losses of sulfhydryls and the concomitant formation of disulfides which were more pronounced in PM protein samples. Oxidation favored cross-linking of myosin rod or tail in PM MPs compared to an equal susceptibility of myosin subfragment-1 (s-1) and rod to •OH in GN MPs. Both Ca- and K-ATPase activities in GN myosin were more sensitive to •OH than their PM counterparts, indicating a less stable s-1 region of GN myosin to oxidation. The uncoiling of rods from PM myosin was more rapid than that in GN myosin during heating. Oxidation induced cross-linking via disulfide bonds hindered the unfolding of rod, particularly in PM myosin. These data revealed the molecular events that underscore the necessity of meat processing and formulation control based on muscle fiber types.