EFFECTS OF IONIZING RADIATION ON THE ENZYME ACTIVITIES AND ULTRASTRUCTURAL CHANGES OF POULTRY

摘要

Enzyme-catalyzed changes are generally recognized as one of the major reasons for fresh meat deterioration after irradiation. In this study, the effects of ionizing radiation and storage on the enzyme activities of poultry as well as the ultrastructural change of muscle were evaluated. When chicken breasts were irradiated at 4℃ and -20℃, both Ca~(2+)-dependent protease and cathepsin D showed some degree of resistance to irradiation. The activities of those two enzymes decreased with the increase of irradiation doses. During storage, Ca~(2+)-dependent proteases showed a marked decrease in activity. On the other hand, the cathepsin D activity was not significantly changed at either 4℃ or -20℃ after 20 days. Transmission electron microscope examination showed no structural changes of the myofibrils with a radiation dose of up to 10 kGy at either 4℃ or -20℃. Freezing protected the irradiated chicken breasts from autolytic enzymes damage during storage. In contrast, considerable sarcomere degradation occurred in Z-line for irradiated samples when stored at 4℃ for 20 days. The action of the proteolytic enzymes may have been responsible for the sarcomere degradation in irradiated chicken breasts.