Effects of nitrite on the protein stability and nitrosation of myofibrillar protein from minced pork subjected freeze-thaw cycles

• NaNO 2 has a concentration-dependent dual effect on myofibrillar protein oxidation. • NaNO 2 (100 mg/kg) effectively improved the cooking yield and water-holding capacity. • Freeze-thaw (F-T) cycles promoted protein nitrosation, regardless of the NaNO 2 dose. • NaNO 2 enhanced textural properties and mitigated color deterioration caused by F-T. • NaNO 2 has a dose-dependent effect on the quality of minced pork during F-T cycles. This study systematically investigated the effects of NaNO 2 concentrations (0, 100, 200, 300, and 400 mg/kg) on the oxidative stability, emulsification capacity, gel properties, and nitrosation of minced pork myofibrillar proteins (MPs) subjected to freeze-thaw (F-T) cycles. The results demonstrated the concentration-dependent dual effects of NaNO 2 on MP in minced pork. At low concentrations, NaNO 2 inhibited F-T induced protein oxidation by increasing free amino levels, reducing carbonyl and dityrosine formation. High NaNO 2 concentrations promoted radical-mediated oxidation, significantly elevating dityrosine and 3-nitrotyrosine formation. Although NaNO 2 could not reverse the loss of solubility and emulsification capacity induced by protein conformational changes during F-T cycles, low concentration (100 mg/kg) effectively improved cooking yield (23.64%) and water holding capacity (14.21%) by facilitating moderate protein cross-linking. Additionally, NaNO 2 significantly ( P < 0.05) enhanced textural properties, increasing hardness, gumminess, and chewiness, while also mitigating color deterioration caused by F-T. The presence of NaNO 2 counteracted the F-T induced detrimental effects on the quality of minced pork.