[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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[in Japanese]

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We have previously reported that notable amounts of cis–vaccenic acid(an oleic acid isomer), scarcely distributed in agricultural products, were detected in fruit vinegars. In ther present study, capillary GC analysis showed that cis–vaccenic acid with 1.6%–15.9% whole fatty acid components was present in five samples from three specimens of commercial rice vinegar, their ratios of cis–vaccenic acid to oleic and cis–vaccenic acids(Vaccenic Acid Value, VAV)being 0.21–0.54. In polished rice, the liquid fraction of saccharified mash and the liquor fraction after alcoholic fermentation as well as the proportions of cis–vaccenic acid were extremely low compared with those of oleic acid, which is one of the major fatty acids in these products. However, the component fatty acid in two acetic acid bacteria, Acetobacter used for rice vinegar production(a factory culture)and the culture(Acetobacter lovaniensis NBRC 3284), grown during a model fermentation examination, was mostly cis–vaccenic acid. Rice vinegars experimentally manufactured were shown to have high VAV(0.22 and 0.47 in vinegars made by the factory culture and the NBRC strain, respectively). In commercial rice vinegars, cis–vaccenic acid was found to be concentrated within the polar lipid fraction, mainly consisting of membrane lipids. These data strongly suggest that the origin of cis–vaccenic acid would be fragments of Acetobacter membrane, transferred into the fermenting liquid during acetate fermentation, indicating the detection of fatty acid components in the dispersed membrane.

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Using the sake samples presented at a sake contest in 2006, we investigated the relationships between concentrations of nitrogen⁄sulfur compounds before the storage of sake and concentrations of polysulfides(DMTS, DMDS)which are the main aroma compounds responsible for “hineka” in sake after the storage of sake, for a month at 50°C. The concentrations of total nitrogen in the sakes exhibited significantly positive correlations with the concentrations of sulfur compounds in the sakes. This result appeared to show that most of the sulfur compounds are derived from rice proteins. The ratio of sulfur of the amino acid formed against total sulfur averaged. 27.6%(min.17∼max.45%)in the sake samples. After storing the sake samples, the concentrations of DMDS were below the detection threshold in all samples, and those of DMTS were above the detection threshold in half of the samples. The concentrations of polysulfides in the sakes after storing showed significant positive correlations with concentrations of sulfur compounds in the sakes before storing. Moreover, a partial correlation analysis showed that the concentration of amino acid containing sulfur had a significant positive correlation with that of polysulfide. These results suggest that sake containing high concentrations of sulfur compounds can produce a high concentration of polysulfide after storage for long periods.

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