HIGH TEMPERATURE EFFECTS ON LYSOSOMAL ENZYME DISTRIBUTION AND FRAGMENTATION OF BOVINE MUSCLE

Abstract

ABSTRACTBovine muscle samples were fractionated and assayed to assess the effects of high postmortem temperatures on lysosomal enzymes and muscle fragmentation values. Samples of the longissimus dorsi muscle were excised from both sides of six animals. One muscle was held at 37°C (HT) and the other was maintained at 2°C as control (C). The pH of the muscles was determined at 1, 4, and 12 hr postmortem. After 12 hr the muscles were homogenized and centrifuged to separate sedimen‐table and unsedimentable fractions which were assayed for β‐glucuronidase and cathepsin C activities. A fragmentation value was also determined for each sample. The pH of the HT samples dropped more rapidly and was significantly lower at both 4 and 12 hr. No detectable difference in total β‐glucuronidase activity was observed between HT and C samples but the distribution was markedly altered as shown by significant differences in the percent of total activity that was unsedimentable (HT > C, P < 0.025) and specific activities of the sedimen‐table (HT > C, P < 0.025) and unsedimentable (HT > C, P < 0.025) fractions. For cathepsin C there was a significant drop in total enzyme activity (HT > C, P < 0.005) resulting from an apparent degradation of the unsedimentable enzyme which had been released by the HT treatment. The fragmentation values were significantly different showing that the HT samples had probably undergone limited proteolysis resulting in a reduction of muscle fragment size after homogenization. These results add support for the role of lysosomal enzymes in postmortem tenderization.