Ultrastructural Changes During Autolysis of Red and White Porcine Muscle

This investigation was undertaken to determine the ultrastructural changes in porcine muscle due to autolysis and their relationship to muscle fiber type. The red and white portions of aseptic porcine semitendinosus muscle were sliced, placed in sterile petri dishes, and stored at 10°C. Samples were taken periodically for pH measurements, bacterial counts and electron microscopic examination. No bacterial growth or significant pH changes were observed in the experimental tissues. White fibers appeared to be slightly more labile to autolysis than red fibers. However, the ultrastructural changes occurred in the same sequence for both fiber types. Mitochondria underwent cristae aggregation with a subsequent loss of cristae material. Nuceli were found to progressively shrink in size during storage with a concomitant concentration of the chromatin material. The I‐band was the area of the myofibril most susceptible to autolytic breakdown and vesicular structures were observed in all areas of myofibrillar degradation.