Potential of peroxynitrite to alter the color of myoglobin in muscle foods

Superoxide anion and nitric oxide can react to form the highly oxidizing species peroxynitrite. The objective of this research was to determine if peroxynitrite can promote the discoloration of myoglobin under conditions expected in muscle foods. Reagent peroxynitrite (25-100 muM) caused rapid and extensive formation of metmyoglobin from oxymyoglobin with the majority of metmyoglobin formation occurring during the first 5-10 min of incubation. Carbon dioxide caused a small decrease in the ability of peroxynitrite to oxidize oxymyoglobin, and peroxynitrite-promoted conversion of oxymyoglobin to metmyoglobin increased with decreasing pH (5.5-7.0). Differential scanning calorimetry suggested that peroxynitrite caused minimal changes in myoglobin structure. These results indicate that peroxynitrite can promote the conversion of oxymyoglobin to metmyoglobin under the conditions expected in muscle foods.