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

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 activitie s of poultry as well as the ultrastructural change of muscle were eval uated. When chicken breasts were irradiated at 4 degrees C and -20 deg rees C, both Ca2+-dependent protease and cathepsin D showed some degre e of resistance to irradiation. The activities of those two enzymes de creased with the increase of irradiation doses. During storage, Ca2+-d ependent proteases showed a marked decrease in activity. On the other hand, the cathepsin D activity was not significantly changed at either 4 degrees C or -20 degrees C after 20 days. Transmission electron mic roscope examination showed no structural changes of the myofibrils wit h a radiation dose of up to 10 kGy at either 4 degrees C or -20 degree s C. Freezing protected the irradiated chicken breasts from autolytic enzymes damage during storage. In contrast, considerable sarcomere deg radation occurred in Z-line for irradiated samples when stored at 4 de grees C for 20 days. The action of the proteolytic enzymes may have be en responsible for the sarcomere degradation in irradiated chicken bre asts.