Ionizing radiation and packaging effects on respiratory behavior, fungal growth, and storage-life of peaches, Prunus persica

Abstract

Investigations were conducted in 1960 to study effects of fast electron and gamma radiations and packaging films on respiratory rate, control of fungal deterioration, and subsequent refrigeration life of peaches. The fungi responsible for deterioration of peaches were also studied in vitro to determine if they were susceptible or resistant to ionizing (fast electron and gamma) radiations. Respiratory behavior of the fruits under normal as well as modified conditions was assessed with a Claypool and Keefer-type respirometer and Orsat-type gas analyzer. Two kinds of polyethylene films were used for packaging fruits. The fruits after treatments and packaging were stored at 40°F and 85 per cent relative humidity and at 75°F and 35 per cent relative humidity. Effects of ionizing radiations Peaches (var. Elberta) Fast electron and gamma radiation increased respiration and controlled fungus growth. A fungus study in vitro was conducted at ambient (75°F) temperature and relative humidity (35 per cent). The results obtained with fast electron radiation showed that the fungus inhibition effect of radiation was directly proportional to the dosage applied. Effects of ionizing radiations and packaging films Peaches (vars. Elberta and Gem) Peaches (var. Elberta) were packaged in Duratite (type of polyethylene) film and then were irradiated with fast electrons, while peaches (var. Gem) were irradiated with gamma rays before they were packaged in Duratite and another polyethylene film. In fast electron radiation experiments the CO 2 accumulation inside the Duratite bags increased with the increasing radiation dosages; whereas in gamma radiation, dosages applied behaved similarly for both the films except that the levels of CO 2 maintained in polyethylene film were lower than in Duratite film. At radiation dosage of 5 × 10 5 rad, injuries on peaches (var. Gem) were shown as brown areas on the surface of the fruit. Fast electron radiation dosages of 1 × 10 5 and 3 × 10 5 rad were effective in controlling fugus growth and in keeping fruit for longer periods of time than in controls and 5 × 10 5 rad treatment. The evaluation of marketable quality of the fruits in gamma radiation experiments was similar to that obtained with fast electron radiation with the exception that the gamma radiation dosage of 3 × 10 5 rad was best in controlling spoilage by fungi while the fast electron treatment of 1 × 10 5 rad was the best protective dosage. In general, fruits packaged in polyethylene seemed to be better protected than fruits packaged in Duratite bags. The fungi observed on peaches were predominantly Penicillium and Rhizopus species. In general it can be summarized that ionizing radiations (dose 1 to 3 × 10 5 rad) in conjunction with packaging in polyethylene bags increased the refrigerated life of fresh peaches by 15 to 20 days.