Effect of prolonged storage in controlled atmospheres on the conservation of the onion (Allium cepa L.) quality

The onion is a low perishability product, but in long-term storage, postharvest losses occur due to some phytopathological and sprouting factors. The aim of this study was to evaluate the effect of storage in controlled atmospheres (CA) on onion cultivar “Sierra Blanca” for seven months. The onions were subjected to three treatments: 1 % O2 + 1 % CO2 (T1), 3 % O2 + 5 % CO2 (T2), both at 2.5 °C and 60-75 % relative humidity (RH), and in environmental atmosphere (control treatment, CT) at 2.5 °C without controlled RH. Changes in enzymatic pyruvic acid (EPA) content, total soluble solids (TSS), dry matter (DM), firmness and sprouting during storage were evaluated. The results showed effect (p≤0.05) of treatment and storage time on all parameters. Changes in preserved bulbs in CA were minimal compared to those in the CT. The EPA was reduced on T1 onions while in T2 and CT onions it was increased at the end of storage. The TSS and firmness decreased in the three treatments, DM remained constant in T1 and T2 onions and in CT onions decreased in the sixth month by 19 %. T1 and T2 onions showed no sprouting, while CT onions, presented internal sprouts in 20 % of sampled bulbs, reaching 100 % from the third month till the end of storage. In conclusion, storage in CA is the best way to preserve the quality of onion “Sierra Blanca” for seven months, which is evidenced by the positive changes in quality.