Impact of Gamma Irradiation on Post-harvest Disorders in 'Bartlett' Pears
The goal of this research was to determine the effect of irradiation on post-harvest disorders and ripening quality of ‘Bartlett’ pears stored for 3 months in air. ‘Bartlett’ pears were treated at 470 and 940 Gy and held at -1 - 0 ˚C at 95 % humidity. At 0, 45, and 90 days following treatment, the pears were brought to room temperature and allowed to ripen. The pears were then monitored for changes in respiration rate and ethylene production. After reaching the climacteric peak, pears were evaluated for incidence of post-harvest disorders, ACS and ACO enzyme activities, and quality factors such as color, texture, titratable acidity and soluble solids content. While irradiation delayed ripening as evident by a delay in the climacteric peak and color change from green to yellow, the longer that pears were stored, the shorter the duration of ripening during each testing period. A delay in ripening was observed in an increased respiration rate and lowered ethylene production during all testing periods in irradiated samples, however, ACS and ACO enzyme activities did not correlate with ethylene production. The levels of compounds associated with superficial scald, α-farnesene and conjugated trienes, were lower in the irradiated pears, however, the incidence of superficial scald was higher in irradiated samples with 28 % and 32 % in 470 and 940 Gy treated pears, respectively, compared to 17 % in control pears, but it must be noted that the superficial scald index was very low for this set of pears. In contrast to superficial scald, the occurrence of senescent scald, core browning and mold incidence was reduced by irradiation. Though there was no statistical significance in color or texture, a delay in degreening and softening was observed in the ripening process of the irradiated fruit. There were no notable differences in quality attributes of titratable acidity and total soluble solids due to irradiation. Our study shows that low dose irradiation, below 1000 Gy, can be an effective method to delay ripening and suppress post-harvest disorders in ‘Bartlett’ pears without impairing the quality of the fruit.
a-farnesene, core browning, ethylene, respiration rate, superficial scald, Food Science
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