Post‐Mortem Changes in Muscle III. Histochemical Observations in Beef and Pork

SUMMARY The activity of 17 or 18 specific enzymes in the longissimus dorsi muscle of five beef and 18 pork carcasses was followed by histochemical procedures. Beef samples were removed from carcasses within 10 min up to 20 days port‐mortem, and pork samples within 16 min up to 24 and/or 48 hr post‐mortem. The beef carcasses were submitted to so‐called normal cooling procedures. However, one side of each of 13 pork carcasses was placed at –29°C, while the other side was subjected to 37°C for the first 41/2–5 hr post‐mortem. In beef muscle, the histochemical activity of lactate dehydrogenase, alpha‐glycerophosphate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase, TPN diaphorase, and DPN diaphorase showed a steady decrease with increasing time post‐mortem. Reactions for both alcohol dehydrogenase and glutamate dehydrogenase were very weak or entirely absent at 48 hr post‐mortem and all subsequent sampling periods. Positive reactions for glucose‐6‐phosphate dehydrogenase and beta‐hydroxybutyrate dehydrogenase were observed in the initial samples only. No acid phosphatase, leucine amino peptidase, or 6‐phosphogluconate dehydrogenase activity was detected in any of the samples. In pork muscle, the activity of lactate dehydrogenase, alpha‐glycerophosphate dehydrogenase, succinate dehydrogenase, isocitrate dehydrogenase, and DPN diaphorase was slightly weaker at both 0 and 24 hr post‐mortem than similar activity in beef muscle. Alcohol dehydrogenase activity was weaker than that observed for the above enzymes, while the activity of glutamate dehydrogenase was of intermediate intensity. Traces of glucose‐6‐phosphate dehydrogenase and 6‐phosphogluconate dehydrogenase activity were observed in only a portion of the initial samples. Similarly, weak reactions for beta‐hydroxybutyrate dehydrogenase were observed only at 0 hr post‐mortem. None or only weak activity was observed for malic dehydrogenase, and TPN diaphorase activity was unexplainably absent from all samples. Moderate levels of cytochrome oxidase activity were observed at both 0 and 24 hr post‐mortem. LTDPG‐glycogen transferase was completely inactivated by the 37°C treatment post‐mortem, but the treatment had a less marked effect upon phosphorylase and branching enzyme. The presence of acid and alkaline phosphatase activity in muscles of 7 carcasses suggested that a degenerative condition existed in these muscles.