46G-1 |
Peroxynitrite-induced color change in myoglobin |
B. J. CONNOLLY1, R. G. Brannan, and E. A. Decker. (1) Department of Food Science, University of Massachusetts, Chenoweth Lab, Amherst, MA 01003 The desirable red color in meat is produced by oxymyoglobin. Oxidation of oxymyoglobin to metmyoglobin in meat results in an undesirable color change to brown. Meat that shows signs of browning must be either marked down for a quick sale, or ground and marketed as a lower value product. Peroxynitrite is a strong oxidizing agent formed by the reaction of nitric oxide, an intracellular messenger, with superoxide, a byproduct of cellular respiration. The objective of this research was to study the effect of peroxynitrite on the oxidation of oxymyoglobin as affected by peroxynitrite concentration, varying pH, temperature, and carbon dioxide. Peroxynitrite-oxymyoglobin reactions contained 25-100 µM of peroxynitrite and 15 mM oxymyoglobin. The state of myoglobin was determined spectrophotometrically at 450 – 600 nm. Peroxynitrite-oxymyoglobin reactions were determined over the pH and temperature range of 5.5-7.0 and 4-35°C, and in the presence and absence of carbon dioxide. Differential scanning calorimetry (DSC) analysis was used to evaluate how peroxynitrite affected myoglobin structure. Peroxynitrite (25-100 µm) caused rapid and extensive formation of metmyoglobin with metmyoglobin increasing with increasing peroxynitrite concentrations. Addition of a combination of 1 mM carbon dioxide and 50 µM reagent peroxynitrite decreased oxymyoglobin oxidation slightly with metmyoglobin concentrations being 4-10% less than oxidation by peroxynitrite alone at pH 7.0. Peroxynitrite-promoted conversion of oxymyoglobin to metmyoglobin increased with decreasing pH and increasing temperatures. DSC analysis showed that peroxynitrite caused denaturation of myoglobin. These results suggest that peroxynitrite promotes the discoloration of oxymyoglobin in vitro, a factor that would decrease the quality and value of muscle foods. Understanding the factors that impact peroxynitrite promoted myoglobin discoloration could lead to new strategies to increase the shelf-life of meat products.
Session 46G, Muscle Foods I
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