INFLUENCE OF STORAGE CONDITIONS ON FLAVONOIDS CONTENT AND ANTIOXIDANT ACTIVITY OF SELECTED SHALLOT (ALLIUM CEPA VAR. ASCALONICUM BACKER) HYBRID CULTIVARS

The aim of this study was to determine changes in the content of flavonoids in fleshy scales of shallot bulbs in relation to different compositions of atmosphere during storage. Also antioxidant activity of the bulbs was determined. Bulbs of shallot cvs. Bonilla F1, Conservor F1 and Matador F1 were stored in two storage seasons at the normal atmosphere (NA) and controlled atmosphere (CA) of the 4 compositions: 5% CO2 + 5% O2, 5% CO2 + 2% O2, 2% CO2 + 5% O2, 2% CO2 + 2% O2. The temperature of storage was 0-1oC and RH 65%. Before and after 7-month storage the bulbs were examined in respect of flavonoids content and antioxidant activity (AA). Flavonoids were identified in methanolic extracts with HPLC, AA was determined with FRAP and DPPH assays. Three flavonoid compounds were identified in the plants extracts. Quercetin 3,4’ di-O-glucoside and quercetin 4’-glucoside (spiraeoside) were present in the highest amounts. CA conditions influenced content of flavonoids in the bulbs. The highest content after storage was observed at gas composition of 5% CO2 + 5% O2. Two major flavonoid compounds, quercetin 3,4’-di-O-glucoside and quercetin 4’-O-glucoside (spiraeoside) showed the increasing tendency, however not all changes were significant. No significant differences were observed between cultivars, but ‘Bonilla’ F1 showed slightly higher flavonoids content than the other ones. Investigated cultivars did not differ in respect of AA, measured both with DPPH and FRAP assay. There was no significant influence of storage conditions on DPPH level, while FRAP level was influenced significantly. Bulbs from 5% CO2 + 2% O2 composition were characterized by the highest FRAP values and the bulbs stored at normal atmosphere – by the lowest.