Structural changes in endomysium and perimysium during post-mortem aging of chicken Semitendinosus muscle-Contribution of structural weakening of intramuscular connective tissue to meat tenderization.

Post-mortem changes in endomysium and perimysium were investigated during aging of chicken semitendinosus muscle at 4°C. Although the shear-force value of raw meat decreased rapidly within 5 h post mortem and gradually thereafter, the solubility of collagen and the ratio of each chain of soluble collagen remained unchanged during 24 h post mortem. Light microscopic studies showed that structures of endomysium and perimysium disintegrated into several thin sheets within 12 h post mortem, and that many gaps opened in the cross-section of endomysium and perimysium. While endomysium and perimysium were not stained by periodic acid Schiff reagent in fresh muscle, they were markedly stained in muscle 12 h post mortem. These results provide direct evidence for the structural weakening of endomysium and perimysium during post-mortem aging of chicken. Therefore, we conclude that the structural weakening of the intramuscular connective tissue is closely related to tenderization of chicken.