Biochemistry of Pork Muscle Structure. 1. Rate of Anaerobic Glycolysis and Temperature Change versus the Apparent Structure of Muscle Tissuea

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Abstract
SUMMARY: Continuous recordings of pH and temperature changes, during postmortem chilling, were made on 20 Danish Landrace carcasses. The continuous recordings from these carcasses depicted at least four distinct types of post‐mortem pH patterns: 1) a slow gradual decrease to an ultimate pH of 5.7–6.3; 2) a gradual decrease to about 5.7 at 8 hr, with an ultimate pH of 5.3–5.7; 3) a relatively rapid decrease to about 5.5 at 3 hr, with an ultimate pH of 5.3–5.6; 4) a sharp, significant decrease to a pH of about 5.1 at 11/2 hr, and a subsequent elevation to 5.3–5.6. The first 3 types were acceptable in structure, color, and water retention, whereas type 4 represented pale, exudative tissue with soft, inferior structure. The violent nature of the post‐mortem changes in tissue with the type 4 pH pattern were discussed, as well as the possibility of a more rapid onset of rigor mortis in this tissue. Although the pH values of the pale, exudative tissue were elevated during chilling, it appeared that they remained generally lower, ultimately, than the normal tissue. On the basis of comparisons between muscles, it is suggested that in addition to chemical composition, the chilling rate of the individual muscle may also be an important factor in determining pH pattern and ultimate muscle structure.