SULFUR-CONTAINING AND NITROGEN-CONTAINING VOLATILE COMPONENTS OF KOHLRABI (BRASSICA-OLERACEA-VAR-GONGYLODES-L)

Volatiles from the edible part of kohlrabi (Brassica oleracea var. gongylodes) were isolated by means of a dynamic headspace sampling device and separated by capillary gas chromatography. For identification samples were subjected to element-specific detection (Flame photometric and nitrogen-phosphorus detectors) and mass spectral analyses. Major volatile products are: 3-methylthiopropyl, 4-methylthiobutyl and allyl isothiocyanate. The two corresponding organic, cyanides 3-methylthiopropyl and 4-methylthiobutyl cyanides and dimethyl, trimethyl and tetramethyl disulphides are also present in higher amounts. n-Nonenal, (E)-2-hexenal, (E,E)-2,4-heptadienal and some isothiocyanates of unknown structure appear in the volatile fraction as minor constituents. The sulphur- and nitrogen-containing components could be related to the enzymic cleavage (myrosinase) of glucosinolates, naturally occurring precursors in brassica plants. Some of the volatile products possess antimicrobial and antithyroid effects and have been identified in different plants of the cruciferae family. The possible role of the isothiocyanates, cyanides, sulphides and aldehydes to the flavour of kohlrabi is discussed.