Velocity of specific selective enzymes in mango [Mangifera indica L.] treated with y- Rays

This study aimed to investigate to what extend the velocities of polyphenol oxidase [PPO], peroxidase [POD] and pectinmethylesterase [PME] are affected by irradiation. To reach such target, the investigated mango fruits were irradiated with different doses of gamma-rays; namely, 500, 1000, 1500, 2500 and 5000 Gy produced from Co60. The velocity reaction of the aforementioned enzymes in relation to different substrate and enzyme concentrations were studied. The kinetic properties in terms of affinity, maximum velocity, activity coefficient and slope of reaction were calculated through a specific computer program [enzyme kinetics]. The changes in the velocity patterns of the investigated enzymes as affected by storage for three weeks at 20 +/- 2C were also studied. On the basis of the obtained results, it was found that a dose of 2500 Gy could be recommended to reach a higher inhibition level of the three tested enzymes, a pattern which improves the quality and extends the shelf-life of mango fruit

Peroxidase, pectin methylesterase and some constituents of pistachio nuts [Pistachia vera L.] treated with and- Rays

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