Lipid oxidation in a chicken muscle model system: Oxidative response of lipid classes to iron ascorbate or methemoglobin catalysis

Catalysis by iron ascorbate and activated methemoglobin generated different oxidative responses in chicken muscle model systems. In iron ascorbate sys tems, large increases in hydroperoxides and thiobarbituric acid-reactive su bstances (TBARS) occurred during the initial stage of incubation. Thereafte r, iron ascorbate catalysis led to a slow increase in the oxidation of tria cylglcyerol (TG) and sarcoplasmic reticulum (SR) membrane lipids. By the en d of incubation, 24, 36, and 32% of the initial content of n-3 fatty acids in free fatty acids, TG, and SR single-lipid model systems catalyzed by iro n ascorbate had been lost. Reduced losses of n-3 fatty acids were observed in the SR and TG fractions (0 and 24%, respectively) when iron ascorbate mo del systems contained all three lipid fractions (mix). Hydroperoxides and T BARS in mode systems catalyzed by activated methemoglobin were characterize d by a lag phase during most of the incubation. Consistent with their role as antioxidants, losses of alpha-tocopherol (42-49%), gamma-tocopherol (36- 42%), and protein sulfhydryls (41-52%) were observed in model systems catal yzed by activated methemoglobin. SR and mix model systems were 30-50% slowe r to oxidize than TG model systems when activated methemoglobin served as t he catalytic agent.