Protein Oxidation and Protein Nitration Influenced by Sodium Nitrite in Two Different Meat Model Systems

The effect of NaNO2 on protein oxidation was studied in isolated myofibrillar protein isolates (100 and 1000 mg NaNO2/kg) and in porcine patties (18 and 180 mg NaNO2/kg). In addition, the potential use of 3-nitrotyrosine as a specific marker for reactive nitrogen species mediated nitration was investigated. Overall, no distinct pro- or antioxidant effect of NaNO2 against carbonyl formation was observed in the isolates or in the patties. However, in the isolates, higher protein carbonyl concentrations were found in the NaNO2-treated samples compared to the treatment without added nitrite immediately after the addition of oxidants and NaNO2. Addition of 180 mg NaNO2/kg to patties resulted in significantly lower thiol concentrations at 4 and 7 days of illuminated chilled display compared to the treatments with 0 and 18 mg/kg NaNO2, whereas no effect was observed in the isolates. No effect of NaNO2 was found on the protein solubility of either meat model. 3-Nitrotyrosine was present in all samples, but no clear effect of NaNO2 addition or oxidation time was observed.