Effect of γ-radiation on post-harvest storage life and quality of onion bulb under ambient condition

Different doses of gamma Irradiation (0 Gy, 10 Gy, 60 Gy, 100 Gy and 200 Gy) were evaluated as potential treatment to extend the storage period and maintain the quality attributes of onion bulbs (cv. Punjab Noraya) at ambient temperature for a period of 144 days. It was observed that storage parameters such as physiological loss in weight, sprouting percentage, rotting percentage and quality traits like total soluble solids, firmness, color parameters, ascorbic acid and pyruvic acid varied significantly (p < 0.05) during storage period with respect to doses of irradiation. No rotting and sprouting were observed upto 24 days and 84 days, respectively in both gamma irradiated and un-irradiated bulbs. At 5 months of storage, the physiological loss in weight varied from 28.5 to 63.6% in all treatments. Physiological weight loss and rotting percentage were higher in the untreated (control) as well as bulbs radiated @ 10 Gy and 200 Gy. Firmness was better retained in the bulbs irradiated with gamma rays @ 120 Gy bulbs upto 84 days of storage. However, no clear-cut pattern for colour changes (L, a, b values) was observed with respect to the irradiation doses. TSS in bulbs decreased upto 36 days of storage and thereafter increased upto 48th day of storage irrespective of the dose of gamma irradiation. Ascorbic acid content of bulbs decreases significantly in all the irradiation treatments during storage but pyruvic acid initially increased, then decreased and again increased at the end of the storage period in un-irradiated and irradiated treatments. It is concluded that onion bulbs irradiated with gamma rays @ 120 Gy resulted in minimum loss in weight, rotting and sprouting while maintained best quality for 3 months of storage at ambient storage conditions.