The effect of pH and aging on mitochondrial reduction of bovine myoglobin's affinity for oxygen.

In skeletal muscles, mitochondria have been shown to decrease the oxygen affinity of myoglobin. In this study, we investigated whether the mitochondrial function of decreasing myoglobin affinity for oxygen persists and operates at the final pH of postmortem bovine skeletal muscle. The oxygen affinity and myoglobin consumption in the presence of mitochondria obtained from fresh and wet-aged beef were evaluated and compared at pH 5.1, 5.6, and 5.7. The results showed that mitochondria obtained from fresh beef preserved myoglobin oxygen consumption and affinity interference, whereas those obtained from wet-aged beef did not. Oxygen consumption and affinity interference were mostly absent at pH 5.1 and were higher at pH 5.7 than those at pH 5.6. Our findings suggest that mitochondria contribute both to an increase in the oxygen affinity of myoglobin in aged meat and a decrease in the oxygen affinity of myoglobin in high-pH meat, such as dark-cutting beef.