Application of gamma radiation in order to improve post harvest life and preserve quality of onion cultivars during prolonged storage

A factorial experiment was conducted to determine the effects of different doses of gamma irradiation on post harvest life and quality of bulbs of four Iranian onion cultivars (White-Ghom, White-Neyshabour, Red-Ridge-Lump, Red-Ray-Corrugated) during 120 days storage at 10-15 °C and 70% relative humidity. Interactive effects of cultivar and irradiation dose significantly affected sprouting, weight loss, firmness, soluble solids content (TSS), and contents of reducing sugars and pyruvic acid of the bulbs after 120 days of storage. Sprouting of the bulbs ranged between 10-100%. The untreated bulbs showed the highest sprouting and weight loss. Gamma irradiation (30-150 Gy) significantly restricted the sprouting percentage and decreased bulb weight loss. Firmness of the irradiated bulbs (90-150 Gy) was higher than the control bulbs. Weight loss of the bulbs was positively correlated with sprouting and negatively correlated with bulb firmness. The irradiation treatments increased the TSS (30-150 Gy) and a reduction in the sugar content of the bulbs (60-150 Gy). The untreated bulbs had the lowest pyruvic acid content at the end of the experiment. Exposure to 90-150 Gy irradiation doses resulted in the highest pyruvic acid content in the bulbs. In summary, the application of 90 to 120 Gy of gamma adiation for improving post-harvest shelf life and quality of onions can be considered as a general guideline.