NOVEL FLAVOR COMPONENTS IDENTIFIED IN THE STEAM DISTILLATE OF ONION (ALLIUM-CEPA L)

Constituents of volatile steam-distilled onion oil were analysed by gas chromatography and gas chromatography/mass spectrometry. Among 49 identified components, 1-(methylthio)1-propanethiol, 1-(propyl-thio)1-propanethiol, 5,6-dihydro-2-methyl-4,6-diethyl-4H-1,3,5-dithiazine, 5,6-dihydro-6-methyl-2,4-diethyl-4H-1,3,5-dithiazine, 5,6-dihydro-2,4,6-triethyl-4H-1,3,5-dithiazine and 2,4,6-triethyl-1,3,5-trithiane are reported in the oil of onion (Allium cepa L.) for the first time. They account for 18.6% of the total volatiles. Reactions of fatty aldehydes, hydrogen sulphide, thiols and ammonia, induced by the distillation process, may be responsible for the formation of these compounds.