Postharvest aspects on bioactive compounds in yellow onion (Allium cepa)

A study was carried out to investigate the effects of lifting time and subsequent curing, drying and storage on the content of quercetin glycosides in yellow onion, grown in Oland, Sweden, in 2002. Half of the onions were lifted at 50% leaf fall (soft necks) and the other half at 90% leaf fall to maximize potential differences. After lifting, the onions were left in the field for curing in 10 days. After further drying in wooden bins at ambient temperature (5-15 deg C), the onions were sorted and stored at 0 deg C and 70% relative humidity (RH) for 5 months. Samples of onions were taken at lifting, after curing, after drying and after 3 and 5 months of storage. Lifting at different stages of leaf fall did not affect the content of quercetin 4'-glucoside. The amounts of quercetin 4'-monoglucoside increased during field curing. During subsequent drying, the content significantly decreased, but was still higher than in onions directly from the field. No significant changes of quercetin 4'-glucoside content occurred during the 5 months of storage at 0 deg C and 90% RH