Porcine myofibrillar proteins (MP) with or without sodium pyrophosphate (PP) were oxidatively stressed in hydroxyl radical (˙OH)-generating systems (10 μM FeCl₃, 100 μM ascorbic acid, and 0, 0.5, 3, 10 mM H₂O₂) at 4 °C for 12 h. The results showed significant protein oxidation under the ˙OH stress, indicated by the modification of amino acid side chain groups and the aggregation of MP, which led to losses in gelling properties of MP especially at high dosages of H₂O₂ (3–10 mM). The PP addition effectively suppressed ˙OH induced lipid oxidation (as evidenced by TBARS values) in MP, but the inhibitory effect on protein oxidation was limited. In fact, the PP treatment with a high level of H₂O₂ (10 mM) tended to promote protein unfolding and aggregation in the tested systems. However, a significantly (P < 0.05) improved protein solubility was found in all tested systems with added PP. The PP treated MP gels exhibited a more compact and orderly microstructure, which may explain the reduced cooking loss and improved gel strength.