Effects of Postmortem Storage on Muscle Protein Degradation: Analysis by SDS-Polyacrylamide Gel Electrophoresis

Changes in myofibrillar proteins of bovine longissimus and semitendinosus muscles were examined during 14 days of postmortem storage at 2°C by SDS-Polyacrylamide gel electrophoresis. Major changes in both muscles were: (1) appearance of a 95,000-dalton component; (2) gradual disappearance of troponin-T and gradual appearance of a 30,000-dalton component; (3) gradual increase in intensity of a protein around 55,000-daltons; and (4) gradual appearance of a 110,000-dalton component. With the exception of the 95,000-dalton component, the other changes have been reported previously by other authors. At the present time we have no knowledge of the origin of the 95,000-dalton component, but it is known that calcium-activated factor (CAF) is responsible for degradation of troponin-T. Appearance of the 95,000-dalton component during postmortem storage suggests involvement of CAF for increasing tenderness during postmortem storage.