Methanethiol-related volatile sulfur

Figure 2. Formation of methanethiol-related volatile sulfur compounds from S-methyl-L-cysteine sulfoxide via the action of cysteine sulfoxide lyase (C-S lyase) in cruciferous vegetables.

Methanethiol-related volatile sulfur compounds are derived from methyl methanethiosulfinate via nonenzymic chemical reactions. Methanethiol and dimethyl trisulfide are readily formed in a model system composed of methyl methanethiosulfinate and hydrogen sulfide (Figure 3 21,22) which is also a volatile component in disrupted tissues of cruciferous vegetables (4,5,17). Additionally, dimethyl disulfide has also been shown to be formed facilely from methyl... 

GC-FPD analysis of freshly-opened commercial caraway-spiced and comparable unspiced sauerkraut samples (70 g drained sauerkraut) were conducted. These samples were contained in 120-mL serum-type vials (Supelco Co., Bellefonte, PA) closed with Mininert valves (Supelco). Samples were warmed to 30°C in a water bath for 10 min before withdrawing headspace gases (4 mL) for GC-FPD analysis. Data in Table II show that caraway-spiced sauerkraut had lower quantities of dimethyl disulfide than the unspiced sauerkraut, whereas dimethyl sulfide was present in comparable amounts in both samples. Methanethiol and dimethyl tiisulfide were not detected in the caraway-spiced sauerkraut, but they were present in significant amounts in the unspiced samples. These results showed that caraway seed modified the flavor of unspiced sauerkraut by suppression of the formation of methanethiol-related volatile sulfur compounds rather than simply masking the undesirable flavors in sauerkraut with spice flavoring. 

Unpleasant sulfurous odors associated with methanethiol-related volatile sulfur compounds limit consumer acceptance and the use of modified atmosphere technologies to extend the shelf life of cruciferous vegetables. Studies have revealed that both enzymic and nonenzymic systems which are present in caraway seed extracts... 

Volatile sulfur compounds are found in most cheeses and can be important flavor constituents. The origin of sulfur-containing compounds is generally thought to be the sulfur-containing amino acids methionine and cysteine (Law, 1987). As Cys is rare in the caseins (occurring at low levels only in Os2- and K-caseins, which are not extensively hydrolyzed in cheese), the origin of sulfur compounds must be primarily Met. Sulfur compounds formed from Met include H2S, dimethylsulfide, and methanethiol. The importance of methanethiol and related compounds in cheese aroma is discussed by Law (1987). 

Methionine metabolism Sulfur compounds, responsible for aroma in wine and typically related to the grape variety, are released by yeast during the AF. In addition, the metabolism of the sulfur-containing amino acid methionine has an impact on wine aroma. Lact. brevis, Lact. plantarum, and O. oeni strains, using a pathway similar to dairy LAB, catabolize methionine producing light volatile sulfur molecules such as methanethiol and dimethyldisulfide, and heavy volatile molecules such as 3-(methylsulphanyl) propan-l-ol and 3-(methylsulphanyl) propionic acid (Pripis-Nicolau et al. 2004 Weimer et al. 1999 VaUet et al. 2008). In wine, O. oeni strains produce more heavy compounds, mainly 3-(methylsulphanyl) propionic acid, than lactobacilli. In water 3-(methyl-sulphanyl) propionic acid descriptors are chocolate and roasted but these notes are not found in wine where they are replaced by red fruit and earthy odors probably because of interactions with other wine components (Pripis-Nicolau et al. 2004). 

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