EFFECTS OF POSTMORTEM TIME AND ELECTRICAL STIMULATION ON HISTOCHEMICAL MUSCLE FIBER STAINING AND pH IN THE MIDDLE GLUTEAL MUSCLE FROM BEEF CATTLE

The purpose of this study was to investigate the histochemical staining properties of the myosin ATPase (pH 9.4) and succinate dehydrogenase (SDH) stains as functions of muscle for electrical stimulation and postmortem time. Muscle blocks, 2 cubic centimeters in volume, were removed from the gluteus medius of five electrically stimulated (ES) and five nonstimulated (NS) contralateral beef carcass sides at 0, 2 and 24 h after stimulation. The pH of the gluteus medius decreased significantly in both the ES (5.86) and NS (6.14) sides within two hours postmortem and the 24 h pH values were 5.76 and 5.72, respectively. Muscle histochemical staining characteristics for myosin ATPase (pH 9.4) did not change (P > .05) within 24 h postmortem for either ES or NS muscle. A change in the staining characteristics for SDH was found for both ES and NS at 24 h postmortem. No difference in histochemical staining characteristics was found as a result of ES.