Composition of Sulfur-Containing Components in Onion and Their Flavor Characters.

Sulfur-containing components in an ethanol extract and boiled water extract of onion (Allium cepa L.) were analyzed by HPLC. Trans-(+)-S-propenyl-l-cysteine sulfoxide (PeCSO) and its γ-glutamyl peptide (γ-Glu-PeCSO) were the major constituents in the ethanol extract, whereas cycloalliin was the most abundant one in the boiled water extract. The large amount of cycloalliin found in the boiled water extract was mostly derived from PeCSO by heating. PeCSO and γ-Glu-PeCSO showed a characteristic kokumi flavor (continuity, thickness, and mouthfulness) by a sensory test in an umami solution containing 0.05% (w/v) each of monosodium glutamate and disodium inosinate.