IRRADIATION AS A METHOD FOR IMPROVED STORAGE AND TRANSPORTATION OF MANGOES

Ionizing radiation has been successfully employed to augment shelflife of a variety of perishable foods. Biochemical and physiological investigations have shown that these effects are brought about by controlling respiration in the case of fruits.

Initial studies were carried out to ascertain the optimum radiation dose required to delay ripening in the mango fruit.

Mature olive green Alphonso mangoes were irradiated in the preclimacteric stage by 12, 25, 50, 75, 100 and 200 Krad. Optimum radiation dose, as determined by maximum delaying effect and minimum damage, was found to be 25 Krad and resulted in extension of storage life of about 10 days at ambient temperatures (25–32°C). A combination of skincoating with a 6 per cent emulsion of "Myvacet", an acetylated monoglyceride and irradiation (25 Krad) gave additional extension in storage of about 6 days.

Storage of control and irradiated (25 Krad) mango fruits at °C, gave 100 per cent marketable fruits at the end of 30 and 50 days respectively, when fruits were kept open to atmosphere; when fruits were wrapped in paper and packed in boxes with dry paddy grass or paper cuttings, storage for 50 and 70 days, respectively, could be achieved. This effect could be traced to an optimum build up of carbon dioxide in proportion to air in the packaged fruits.

There was excessive inhibition of respiratory rate due to skin-coating or storage at sub-room temperatures (5°, 10° or 15°C); this could be off-set by a dose of 25 Krad because of the spurt in respiration immedia tely after irradiation, which decreased after 48 hours to optimum values. Control fruit, either skin-coated or stored at 5°C, did not show high organoleptic ratings, while the irradiated fruit was highly acceptable. Irradiation influenced permeability changes caused by skin-coatings, thus respiratory rate of mango irradiated and coated was much lower than when skin-coated and then irradiated. Skin-coating followed by irradiation therefore gave best results.

Railroad transportation over a total distance of 1500 miles showed 0, 66, 100 per cent marketable fruits on the 15th day after irradiation for control, irradiated (25 Krad) and skin-coated-irradiated mango respectively. Packaging was done in baskets and, during the journey, ambient temperature rose to 42°C. Treated fruits were also air-freighted to the University of Florida and to the Massachussetts Institute of Technology and were reported to have been in excellent conditions.