Abstract
The morphological changes in myofibrils closely related to meat tenderness were determined quantitatively by measuring both the weakening of rigor linkages formed between actin and myosin and the weakening of Z-disks in chicken, rabbit and porcine skeletal muscles during postmortem aging at 5°C. The weakening of both myofibrillar structures rapidly progressed at almost the same postmortem time in each animal species; it was 6-36 hours, 1-4 days and 5-8 days in chicken pectoral, rabbit back and porcine back muscles, respectively. On the other hand, the result of tenderness evaluation by mechanical testing reached a minimum value after 24 hours, 3 days and 7 days postmortem in chicken pectoral, rabbit back and porcine back muscles, respectively. Therefore, it was concluded that the weakening of myofibrillar structures during postmortem aging coincided with the tenderization of meat in all animal species examined, and that those changes occurred in the order of chicken, rabbit and porcine muscles. With regard to the differences in rate of meat tenderization among animal species, it is suggested that the mechanism can be reasonably explained by' the calcium theory of meat tenderization' rather than by proteolysis due to proteases endogenous to skeletal muscle cells.
