IDENTIFICATION OF THE VOLATILE SULFUR COMPONENTS OF COOKED CABBAGE AND THE NATURE OF THE PRECURSORS IN THE FRESH VEGETABLE^a

Abstract

It is well known that cabbage contains thermolabile sulfur compounds which evolve sulfurous odors. Simpson and Halliday (22) investigated the volatile sulfur produced by boiling cabbage during the period of cooking. The formation of hydrogen sulfide was attributed to the hydrolysis of allyl isothiocyanate, the mustard oil of the thioglucoside sinigrin. Masters and Garbutt (16) similarly described the volatile sulfur as sulfide sulfur, but made no identification of the volatile organic sulfur.The present investigation identifies the volatile divalent sulfur compounds of cooked cabbage. For this purpose a train of absorption traps is utilized modifying the procedure of Challenger and Rawlings (7).It is also shown that the major volatile sulfur component of cooked cabbage is derived from L-S-methylcysteine sulfoxide, a free amino acid occurring in cabbage, first described by Synge and Wood (24), and reported to account for a substantial proportion of the organic sulfur of cabbage.The relationship between therniolabile precursors and volatile sulfur is of considerable importance to flavor, if one accepts the supposition that odors commonly described as disagreeable may contribute to an acceptable flavor, and be considered normal constituents of the aroma, when present in trace amounts. Examples of such a possible role for sulfur compounds are: hydrogen sulfide and mercaptans in beer (51, the brothlike flavor of 3-methylmercaptopropionaldehyde (17), ethyl 3-niethylthiopropionate in pineapple (12), allyl isothiocyanate in mustard ( l l ) , etc. EXPERIMENTALVolatile sulfur, train analysis. The train of traps illustrated in Figure 1 was used for qualitative identification of volatile sulfur compounds. A head of cabbage (600 g.) was dispersed in a Waring blender with 150 ml. of distilled water. A 250 g. aliquot of the slurry was placed in a 500 ml. round-bottom flask, to which was fitted an adapter with gas inlet and a 20 cm. Allihn condenser. The train of traps consisted of (a) anhydrous calcium chloride, (b) lead acetate (s.) (Pb(C?HsO,)? * 3H20), (c) 4% mercuric cyanide (aq.), and (d) 3% mercuric chloride (aq.). The calcium chloride and lead acetate traps separated hydrogen sulfide from organic sulfur (20). The slurry was aerated with commercially purified nitrogen at the rate of 100 ml./min. by applying a vacuum a t the end of the train. After 6 hours no precipitate was observed in the mercury salt solutions. The slurry was then boiled under reflux and aeration continued overnight.Lead sulfide was formed in the lead acetate trap in a few minutes. I n 20 to 50 minutes '

Comparison of three methods for accurate quantification of hydrogen sulfide during fermentation

“…Similarly, exposure to methyl mercaptan did not affect the result of the H 2 S analysis. This result is consistent with the observations of Dateo et al [23], who described the selective reaction of lead acetate with H 2 S in the presence of mercaptans and absence of moisture. No interference from similar concentrations of SO 2 and mercaptans was observed for silver nitrate tubes, in agreement with previous findings using silver nitrate paper strips [17] and membranes [16].…”

“…However, in the presence of high concentration of other sulfur containing compounds, interferences can be observed [23], resulting in erroneous readings. In fermentation, yeast metabolisms results in the accumulation of namely SO 2 , sulfides, and mercaptans.…”

Changes in volatile compounds of pickled mustard tuber (Brassica junceavar. tsatsai) during the pickling process

“…It was well known that the major volatile sulphur component of cooked cabbage is derived from l ‐S‐methylcystein sulphide, a free amino acid occurring in cabbage. It was reported that l ‐S‐methylcysterine sulfoxide was more readily degraded to form dimethyl disulphide in cooked cabbage (Dateo et al. , 1997).…”

The Volatile Sulfur Components of Cabbagea

“…Components were identified by analysis of the fragmentation patterns in accordance with established direct-method techniques (Dunning, 1955;Rock, 1951).…”