LIPID-PEROXIDATION INDUCED BY H2O2-ACTIVATED METMYOGLOBIN AND DETECTION OF A MYOGLOBIN-DERIVED RADICAL

The aim of this work was to better understand the oxidative processes which regulate lipid and myoglobin oxidation during an 8-day storage p eriod of two bovine muscles: Longissimus lumborum (LL), stable from vi ewpoint of color stability, and Psoas major (PM), unstable. Lipid pero xidation (TBA-RS accumulation), induced by a H2O2-activated MetMb syst em, was greater in microsomal membranes from Psoas major muscle than f rom Longissimus lumborum muscle and particularly after 8 days of meat storage. These results could be pertly explained by the differences in the phospholipids and fatty acids composition of microsomal fractions of two studied muscles. To better understand these oxidative processe s in relation to muscle type and post-mortem storage time, it was meas ured in vitro, by optical and ESR spectroscopy, the formed radicals in a H2O2-activated MetMb system with or without microsomes. By optical spectroscopy, it was shown that the decay rate constant of the ferrylm yoglobin radical into ferric myoglobin was enhanced (6-fold) after add ition of the microsomal membranes. No muscle effect was noted. With ES R spectroscopy, it was shown that a tyrosine peroxyl radical was forme d. After addition of the microsomal membranes, the increase of the dec ay rate constant was very low (1.4-fold) but was greater when the micr osomal fraction was extracted after 8 days of meat storage.