Oxymyoglobin oxidation and membranal lipid peroxidation initiated by iron redox cycle

Oxymyoglobin is the main pigment in muscle tissues, responsible for the bright red color of fresh meat. Oxidation of the heme iron from the ferrous to the ferric metmyoglobin produces the brownish color that consumers find undesirable in fresh meat. The aim of this study was to elucidate the mechanism of oxymyoglobin oxidation in muscle tissues by using a model system containing oxymyoglobin and muscle membranes oxidized by an iron redox cycle. Oxidation of oxymyoglobin was determined from the decrease in absorption of the solution measured by a spectrophotometer at 582 nm. Lipid peroxidation was determined by accumulation of TBARS and conjugated dienes. The higher rates of oxidation of oxymyoglobin (20 muM) and lipid oxidation were achieved by using ferric iron and ascorbic acid at concentrations of 50 and 200 muM, respectively. Increasing the concentration of ascorbic acid to 2000 muM switched its effect to antioxidative. Increasing the concentration of oxymyoglobin from 20 to 80 muM inhibited lipid peroxidation by > 90% and partially prevented oxymyoglobin oxidation.