Effects of Postmortem pH and Temperature Muscle Structure and Meat Tenderness

ABSTRACT Bovine longissimus muscles with postmortem pH in the range 5.5 ‐ 7.0 were subjected to different postmortem temperatures of 1°, 4°, 25° and 37°C. Intact beef sides with different postmortem pH were also subjected to two different environmental temperatures of 1° and 25°C. High pH muscles exhibited an extensive degradation of Z‐lines, whereas low pH muscles showed a preferential degradation of M‐lines and myosin heavy chains. Intermediate pH muscles did not show much degradation of muscle proteins, resulting in tougher meat than either low or high pH muscles. High postmortem temperatures enhanced the degradation of muscle proteins in excised and incubated muscle strips, but the delayed chilling of intact beef sides at 25°C for 8‐hr did not affect either the structural changes or meat tenderness.