Gamma Radiation Effects on the Pectic Substances in Citrus Fruits

SUMMARY— Exposure of citrus fruits to gamma radiation at doses of 150 and 300 krad increased the water- and oxalate-soluble pectins and decreased the protopectin in component parts of Valencia oranges and Duncan grapefruit. The quantities of water-soluble pectin and protopectin in the peel and membrane were affected the most by irradiation. Degradation of the pectins as measured by jelly grade increased in all components of the irradiated fruits. The greatest decrease in jelly grade occurred in the March samples when the Brix/acid ratio was least. Methoxyl contents of the pectins from the peel of oranges and grapefruit decreased, while this characteristic decreased only slightly in pectins from the membrane of irradiated fruits. Pectinesterase activity in the peel of both oranges and grapefruit decreased with increased dosages, while the activity in the membrane of both fruits increased.