Quercetin content in stored onions (Allium cepa l.): effects ot storage conditions, cultivar, lifting time and nitrogen fertiliser level

Storage experiments with commercial cultivars of onion (Allium cepa L.) were performed at low constant temperature (1 degrees C) and at higher variable temperature (similar to 8 degrees C). Cultivar differences in quercetin glucoside content were significant, but neither nitrogen fertiliser level nor lifting time had more than minor effects at start of storage or after 3 or 5 months of storage. The role of onion size for quercetin glucoside content and composition was in-consistent but seemed to be of minor importance. Irrespective of storage conditions, the content of quercetin glucosides only showed minor reduction and the composition was unchanged. After 5 months of storage, onion sprouting was recorded during a shelf-life period of 9 weeks at room temperature. Early lifting resulted in onions with low sprouting and good storage abilities without negative effects on quercetin glucoside content. The results suggest that it may be possible to minimise nitrogen fertiliser levels without negative effects on onion yield, quercetin glucoside content or storage capacity.