Studies on Maturation Changes in Fruits Induced by Ionizing Radiation

Part IV. Effects of gamma radiation on the firmness and some chemical constituents of bartlett pears

Abstract

The Bartlett pears at the stages of pre-climacteric and climacteric-onset were irradiated at 250-1000 Krad with gamma rays and stored at 20°C. The yellowing of irradiated pears was delayed and high doses of irradiation (above 500 Krad) prevented normal coloring; the 500 Krad-fruits became only yellowish green and the 1000 Krad-fruits did not develop yellowish color. The organoleptic evaluation showed that the acceptability of the irradiated fruits lowered with high dose. Irradiation caused the softening of the tissue immediately after irradiation but the subsequent change was smaller in irradiated fruits than that in unirradiated ones. The decreasing rates of protopectin and water soluble pectin during storage were slower in the irradiated fruits than that in unirradiated ones. Particularly, the flesh of the 1000 Krad-fruits was mealy and atypical. The activities of pectin methylesterase and polygalacturonase during ripening were lower in the 1000 Krad fruits than in control sample.
The characteristic flavor of pears was not given by the fruits which were irradiated at the doses of 500 Krad and 1000 Krad, while in the ripe fruits of 250 Krad-samples the flavor was produced.