EFFECT OF IRRADIATION AND STORAGE ON CELL-WALL STRUCTURE OF GOLDEN DELICIOUS AND EMPIRE APPLES

Apples (Golden Delicious and Empire) were irradiated by a Co-60 radiat ion source (0, 1 and 2.5 kGy doses) then stored for 6 weeks at 16 degr ees C. The rate of autolysis of apple cortex of cell wall materials (G olden Delicious, Empire) increased significantly (P less than or equal to 0.05) as a function of increasing radiation dose (1-2.5 kGy) and s torage time. The amount of neutral carbohydrates released from the ins oluble cell wall fraction increased significantly (P less than or equa l to 0.05) higher with 2.5 kGy irradiation. The activity of polygalact uronase enzyme increased and that of beta-galactosidase decreased as a function of increasing radiation dose and storage time. Irradiation c aused significant (P less than or equal to 0.05) softening of Golden D elicious and Empire apple. Empire apple cultivar was more sensitive to irradiation and less storable than Golden Delicious cultivar. The ult rastructure of stored apple cortex tissues was different in the invest igated cultivars as observed by scanning (SEM) and transmission electr on microscopy (TEM). While the cells in cortex tissues of the stored E mpire apple shrunk and collapsed, the cortex tissue cell of stored Gol den Delicious cultivar did not differ from those of the fresh one. The cells in the irradiated (1 and 2.5 kGy) apples shrunk and collapsed. The striation pattern on the cell wall of apple cortex tissues with 2. 5 kGy irradiation also changed from the parallel to branch-like indica ting the decomposition of cell wall materials.