Pilot-scale studies on irradiation and storage of onions

Irradiation of onions (shallots) on a pilot scale and storage under various conditions was carried out in four separate studies in the years 1981-1984. The results show complete inhibition of both external and internal sprouting with a dose of 50-80 Gy gamma radiation if treated within two weeks of harvest. Late irradiation results in gradual death of the primordial buds leaving a distinct dark patch in the budding region. Storage losses owing to dehydration and rotting were significantly reduced in irradiated onions stored for 8-10 months at ambient conditions (20-37 deg. C and 70-90% r.h.) and in cold storage (15 deg. C). Periodical evaluations of the relevant physical properties revealed that onions irradiated within the optimum time (2 weeks of harvest) and in bulk storage on shelves have superior keeping qualities compared with the corresponding unirradiated samples. Low-temperature storage of irradiated onions does not appear to reduce storage losses to the extent expected if the relative humidity inside the cooler is not properly controlled. Onion varieties have been observed to respond differently to irradiation treatment and storage with regard to storage losses. Evaluation of organoleptic properties of unirradiated and irradiated onions stored under different conditions showed favourable ratings for the irradiated samples. Consumer acceptance tests and limited marketing conducted during and after termination of storage indicated consumer preference for irradiated onions. (author)