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 center dot OH-oxidizing system (10 M FeCl3, 0.1 mM ascorbic acid, with 0, 5, 10, or 20 mM H2O2) at pH 6.2, 4 degrees C for 18 h. The solubility of nonoxidized (control) PM MPs (63%) was higher than that of control GN MPs (41%). After oxidation with center dot 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 center dot OH in GN MPs. Both Ca- and K-ATPase activities in GN myosin were more sensitive to center dot 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. Practical Application Myofibrillar proteins from white (type IIB) muscle fibers have higher gelling potential than red (type I) muscle fibers during meat processing, and the difference is generally attributed to their distinct chemical and structural properties. Understanding their sensitivity to processing conditions would help with ingredient selection for producing high-quality meat products.