A MECHANISM FOR THE INVOLVEMENT OF NADH-DRIVEN METMYOGLOBIN REDUCING ACTIVITY IN MEDIATING LIPID OXIDATION IN MUSCLE POST-MORTEM

摘要

IntroductionThe reduction of metmyoglobin is an important physiological phenomenon in live animals and is also important in maintaining a fresh colour in meat during post-mortem storage depending on the availability of cofactors. Metmyoglobin reduction was identified in skeletal muscle through the microsomal NADH-dependent electron transfer involving NADH-cytochrome b5 reductase and cytochrome bs (Arihara et al., 1989; 1997). However, other enzymatic and non-enzymatic systems may be involved (Bekhit and Faustman, 2005). In an earlier study (Bekhit et al., 2005), myofibrillar myoglobin reducing activity (MMRA) and total myoglobin reducing activity (TMRA) - that is the sum of reducing activities present in the sarcoplasmic and myofibrillar fractions of the muscle - were found to be correlated to lipid oxidation as measured by thiobarbituric acid reactive substances (TEARS) [r = 0.407 (P < 0.001) and r = 0.367 (P < 0.001) for MMRA and TMRA, respectively]. However, in the presence of zinc ions (an antioxidant), oxidative processes were delayed. The current study was conducted to evaluate the mechanisms involved in meat lipid oxidation through two different free radical detecting systems.