RESUMEN
Pistachio nuts [Pistachia vera L.] variety Halapy, family Anacardiaceae were obtained from Aleppo City, Arab Republic of Syria. The investigated pistachios were kept in perforated standard carton boxes of 45 x 30 x 12 cm dimensions under good ventilation conditions. Irradiation treatments were applied using cobalt-60 facilities "Egypt Mega Gamma 1" model AECL 6500 and the dose levels were 250, 500 and 2000 Gy. The irradiated samples were stored at 20C for six months, through which the activities of peroxidase [POD/EC 1.11.1.7] and pectin methylesterase [PME/EC 3.1.1.11] were followed. The kinetic parameters in terms of Km, Vmax, angle of activity, catalytic efficiency, slope of activity and inhibition levels were considered within a storage period of six months. Amino acids and fatty acids profiles of irradiated pistachio were also given. Experiments proved the preference of a dose of 500 Gy for inhibiting both of the two tested enzymes in the investigated pistachios during the whole period of storage