Irradiation as a postharvest quarantine treatment for a new pluot cultivar

Abstract

The effects of irradiation treatment on the quality of ‘Flavor Fall’ pluots (Prunus salicina×armeniaca Lindl.) were tested to determine if this is a feasible alternative postharvest mitigation treatment to disinfest fruit of quarantine pests. Packed cartons of fruit were treated with three doses of irradiation (400, 900 and 1400Gy) where after the fruit was cold stored for 42d with a dual temperature regime and then 7d to simulate shelf-life conditions. The effect of two different bag types used inside the carton was also tested; a high density polyethylene perforated bag used commercially to package grapes, and a low-density polyethylene insect-proof bag with much smaller perforations. Respiration rates and ethylene production were determined at various time points during the trial, and quality parameters such as hue angle, shrivel, flesh firmness, decay and gel breakdown were measured throughout the process. The results indicated that the respiration rate of the fruit generally increased as the irradiation dose increased, except after shelf-life where it decreased after reaching a maximum at 400Gy. Even at the highest dose most of the quality parameters measured at the end of cold storage were above the minimum arrival standards for overseas markets, except for shrivel, a condition that is common in the ‘Flavor Fall’ cultivar. Shrivel was higher than the maximum allowed, and although fruit contained in the insect-proof bags had half the amount of shrivel than fruit in the commercial bag, it was still above the maximum 10% allowed for export fruit. After further optimization of the approach, a system using insect-proof bags and irradiation would be an effective non-toxic alternative to currently used mitigation treatments for plums.