Protein oxidation enhances hydration but suppresses water-holding capacity in porcine longissimus muscle

Pork longissimus muscle was oxidized at 4 °C by mixed 10 μM FeCl₃/100 μM ascorbate with 1, 5, 10, 20, 30, 40, or 50 mM H ₂O₂ (pH 6.2). Oxidation with >1 mM H₂O ₂ for 40 min significantly (P < 0.05) enhanced hydration of muscle samples, whereas oxidation with 40 and 50 mM H₂O₂ for 2 min or with 20 mM H₂O₂ for 40 min caused pronounced declines in water-holding capacity and product yield. The changes coincided with marked increases in the protein carbonyl content, TBARS formation, and cross-linking of both myofibrillar and sarcoplasmic proteins. Dye-tracing tests showed that the enhanced hydration at >1 mM H₂O₂ was due to facilitated water diffusion into muscle tissue. This result was strongly corroborated by microscopic images that illustrated enlargements of intercellular spacing, that is, gaps, in oxidized muscle tissue, which served as canals for water diffusion.