RESUMEN
In this study, the semitendinosus of horse meat was used as the raw material. The study assessed the variation of the tenderness of horse meat during postmortem aging through the injection of papain, bromelain and fungal protease. The cooking loss of the horse meat became worse during postmortem aging. Low concentration of protease improved water retention properties of horse meat. Papain, bromelain and fungal protease had significant influence on MFI and shear force. MFI increased obviously but the shear force decreased significantly with the addition of more protease (p <0.05). During postmortem aging, many small molecules popeptide appeared in treatment group. Myosin light chain 2, 20 KDa, 32 KDa and 75 KDa bands appeared at first, however later they disappeared in the group with high concentration of protease treatment in addition to the disappearance of Desmin and Troponin I. The muscle fiber, perimysium and endomysium were degraded because of papain, bromelain and fungal protease treatment. More muscle fiber fragments appeared during postmortem aging.Thus, the tenderness and eating quality of horse meat were improved by adding three kinds of protease.