Distribution of S-Alk(en)ylcysteine sulfoxides in some Allium species. Identification Of a new flavor precursor: S-ethylcysteine sulfoxide (Ethiin).
The content of S-alk(en)ylcysteine sulfoxides, important nonvolatile flavor precursors, was determined in 15 different Allium species by means of gas chromatography. The method employed is based on derivatization of S-alk(en)ylcysteine sulfoxides with ethyl chloroformate followed by their reduction with sodium iodide. The total content of S-alk(en)ylcysteine sulfoxides varied considerably in the wide range between 0.02 and 1.3% fresh weight. Not only the total content but also relative proportions of individual derivatives varied to a great extent. A novel S-alkylcysteine derivative, S-ethylcysteine sulfoxide (ethiin), not previously reported to occur in Allium species, was found in most of the samples examined in trace amounts. None of the other S-alk(en)ylcysteine sulfoxides, for example, isopropyl, (Z)-1-propenyl, butyl, or pentyl, were detected in any of the samples analyzed, limiting possible levels of each of these components to </=1 ppm in fresh weight.
Kubec
R
R
Department of Food Chemistry and Analysis, Institute of Chemical Technology (ICT), Technická 1905, 166 28 Prague, Czech Republic.
Svobodová
M
M
Velísek
J
J
D000490:Allium / Q000737:chemistry*; D002849:Chromatography, Gas; D003545:Cysteine / Q000031:analogs & derivatives* / Q000737:chemistry; D008956:Models, Chemical
C406690:ethiin; D003545:Cysteine