Change in flavonoids and radical-scavenging activity during processing of onion extract

Abstract

This study focused on the high radical-scavenging activity of onion extract (onion-flavor seasoning made from onion) and aimed to clarify its changing profile. Radical-scavenging activity, amount of major flavonoids, and browning degree during onion extract processing were measured. In heat processing of concentrated onion juice, radical-scavenging activity and browning degree significantly increased, and most flavonoids disappeared. The principal component of the radical-scavenging activity of onion extract was found to be melanoidin. The fractionation of onion extract using solidphase extraction based on hydrophobic interaction showed that the fraction exhibiting higher hydrophobicity had higher radical-scavenging activity and browning degree.