Effect of nitrous oxide (N2O) on respiration rate, soluble sugars and quality attributes of onion bulbs Allium cepa cv. Rouge Amposta during storage

Effects of nitrous oxide (N2O) on respiration rate (RR), soluble sugars, and organic acids during treatment, and sprouting and rotting during storage of onion bulbs (Allium cepa cv. Rouge Amposta) were investigated. Concentrations of 50, 80 and 100 kPa of N2O were applied for 5, 10 and 15 days at 18 degreesC and compared to control (atmospheric air) samples and samples kept under 100 kPa N-2. RRs reduced by 50% after 5 days were restored progressively and the difference between control and N-2 and N2O treated bulbs was approximately 17 and 25% less after 10 and 15 days, respectively. Soluble sugars were slightly higher in treated onions and averaged 6.97% under 100 kPa N-2, and 7.17, 6.18 and 6.58% under 50, 80 and 100 kPa N2O. However in control bulbs, soluble sugars averaged 5.33%. During treatments of bulbs with N2 and N2O, organic acid contents increased and accumulation was observed throughout the time of exposure. After 5, 10 and 15 days of treatment, five acids-citric acid, succinic acid, fumaric acid, malic acid and oxalic acid-increased in both N-2 and N2O treated bulbs. Large variability and randomized levels of sprouting of treated bulbs were observed, but no significant difference was noted between control and N2O or N-2 treated samples. N2O effectively reduced rotting of bulbs; those kept under N-2 showed higher rotting than control and N2O treated bulbs. (C) 2003 Elsevier B.V. All rights reserved.