Steam Volatile Isothiocyanates of Raw and Salted Cruciferous Vegetables Yasuhiko MAEDA, Yoshio OZAwA* and Yasushi UDA Laboratory of Food Chemistry, Faculty of Agriculture, The University of Utsunomiya, Utsunomiya-shi, Tochigi 320 *Gunma Women's Junior College, Takasaki-shi, Gunma 370 The steam volatile isothiocyanates occurring in raw cruciferous vegetables and salted products thereof were investigated by a combination of gaschromatography and mass spectrometry. From the raw products the glucosinolates were extracted and subjected to enzymic hydrolysis by addition of mustard seed myrosinase and L-ascorbate ; subsequently, steam distillation of the enzymically hydrolyzed glucosinolate extracts was performed. 2-Butyl, 3-butenyl, 4-pentenyl, 2- phenethyl and 5-methylthiopentyl isothiocyanate were found in all raw materials. In addition, allyl, 4-methylpentyl and 4-methylthiobutyl isothiocyanate were present in the distillates from species of Brassica campestris L. ssp. rapifera ; allyl, pentyl and 3-methylthiopropyl isothiocyanate in the volatile fraction from species of B. juncea (L.). In a parallel study, the salted materials which had undergone autolysis during the process of salting at their unadjusted ph, were subjected to steam distillation. A relatively large percentage of total isothiocyanates was observed in the steam volatile fractions obtained from the salted materials except for the product Zasai-zuke'. The isothiocyanates found as characteristic minor components in the raw materials were not detected in the salted ones. (Received April 10, 1979)
Table I. Identified Steam Volatiles from Enzymically Hydrolyzed Glucosinolate Extracts of Raw Japanese Cruciferous Vegetables (I ` \a) a Characterizes the raw materials : (I ), Hakusai-leaves ; ( U), Hiroshimana-leaves ; ( V), Nozawanaleaves; ( W), Hinonakabu-roots; (V), Tennojikabu-roots; ( Y), Kanamachikokabu-roots; Takana-leaves; ( [), Zasai-stalks ; ( \), Zaona-leaves. b To separate the components of this peak a 5% PEG -4000 column was used ; three components were found, and the identified compounds in this peak, arising in the volatiles from (I), ( U), ( V), (V), and ( Y), were : ethyl acetate, 3-butenyl cyanide, and 4-pentenyl cyanide ; in those from ( Z), ( [), and ( \) : ethyl acetate, allyl cyanide, and 3-butenyl cyanide (cf. Fig. 2, Table II.). The percentage of the peak area is expressed as a total of the components. Identified by peaks at m/e (rel. intens. %) 143 (M+, 34), 128(10), c 117(11), 97(31) (100), 55(40), 47(16), 41(34). d Tentatively identified. e Unidentified., 69(28), 61, ( W)
Fig. 1. Gas Chromatograms of the Identified Steam Volatiles in Enzymically Hydrolyzed Glucosinolate Extracts of Raw Japanese Cruciferous Vegetables (I ` \a). Column: 5% SE-30 on chromosorb W AW (60 `80 mesh), 3mm (i.d.) ~1m, glass. N2 flow rate : 30ml/min. Detector : FID. Column temp.: Programmed from 60 KC to 160 KC at a rate of 5 KC/min, after 5 min at 60 KC. See footnote a to Table I. a
Table II. Identified Steam Volatiles from Salted Japanese Cruciferous Vegetables (X `XVa) a Denotes the following salted materials (X), Hiroshimanazuke (leaves) ; (XI), Nozawanazuke leaves) ; (X U), Hinonakabuzuke (roots) (X V), Takanazuke (leaves) ; (X W), Takanafuruzuke ( (leaves) ; (XV), Zasaizuke (stalks). b Identified by peaks at m/e (rel. intens. %):81 (M+,18), 80(5), 67(20), 66(10), 54(25), 53(9), 41(100). c Identified by peaks at m/e (rel. intens.%): 95 (M+, 13), 94(7), 80(5), 68(24), 67(18), 55(100), 41(78). d Uuidentified.
Fig. 2. Gas Chromatograms of the Identified Steam Volatiles from Salted Japanese Cruciferous Vegetables (X `XVa). Column : 5% PEG-4000 on chromosorb G NAW (60 `80 mesh), 3mm (i.d.) ~2m, glass. N2 flow rate : 20ml/min. Detector : FID. Column temp.: Programmed from 100 KC to 160 KC a rate ate of 3 KC/min, after 10 min at 100 KC. a See footnote a to Table II.
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