Quercetin content in onion (Allium cepa L.), represented mainly by 3,40
-O-quercetin diglucoside (3,40
-
Qdg) and 40
-O-quercetin glucoside (40
-Qmg), was examined in five cultivars before and after three cooking
treatments (sauteing, baking, and boiling). Baking and saut ! eing produced a 7–25% gain in quercetin !
concentration, while boiling produced an 18% decrease in quercetin concentration. Ratios of 3,40
-Qdg to
40
-Qmg in tissues ranged from 1:1.3 and 1:1.7, and combined the two conjugates represented 89–90% of
total flavonol content in treatment and raw control means indicating heat stability of the flavonols.
Changes in flavonol concentrations as a result of cooking method were consistent across all five cultivars.