Iizuka-Furukawa Sachiko, Isogai Atsuko, Kusaka Kazutaka, Fujii Tsutomu, Wakai Yoshinori
Kizakura Co. Ltd., 223 Shioya-machi, Fushimi-ku, Kyoto 612-8046, Japan; National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-hiroshima 739-0046, Japan.
National Research Institute of Brewing, 3-7-1 Kagamiyama, Higashi-hiroshima 739-0046, Japan.
J Biosci Bioeng. 2017 Feb;123(2):209-215. doi: 10.1016/j.jbiosc.2016.09.002. Epub 2016 Oct 20.
The grassy characteristic aroma perceived in brewed sake made from low-glutelin rice (Oryza sativa L. Mizuhonoka) was examined by gas chromatography-olfactometry and gas chromatography-mass spectrometry. By comparing the odor properties and Kovats retention indices to those of standard compounds, 4-mercapto-4-methylpentan-2-one (4MMP) was found to contribute to the characteristic aroma. Sake brewing using Mizuhonoka, low-glutelin rice, and Gin-ohmi (a control) revealed that 4MMP concentrations in Mizuhonoka sake samples were higher than those in Gin-ohmi samples over the fermentation period. The concentration in final Mizuhonoka sake was twice that of Gin-ohmi. To investigate the mechanism of 4MMP formation, the putative precursors, 4-S-cycteinyl-4-methylpentan-2-one (cys-4MMP) and 4-S-glutathionyl-4-methylpentan-2-one (glut-4MMP), in sake and its materials (rice and koji) were analyzed by ultra-performance liquid chromatography tandem mass-spectrometry. Cys-4MMP was not detected in all samples, while glut-4MMP was present in sake and its materials. The glut-4MMP concentration in sake was lower than that in Gin-ohmi over nearly the entire fermentation period, suggesting that conversion of the precursors to 4MMP was more effective in the mash of low-glutelin rice Mizuhonoka than in Gin-ohmi. The release of 4MMP during alcoholic fermentation from a model medium containing its precursors was examined. While no 4MMP release was observed in the control (no addition), with the addition of its precursors, the release of 4MMP increased as fermentation progressed. It was suggested that 4MMP was generated from both cys- and glut-4MMP by sake yeast. The perception threshold of 4MMP in sake was determined as 1.2 ng/L.
通过气相色谱 - 嗅觉测量法和气相色谱 - 质谱分析法，对由低谷蛋白大米（水稻品种“水之穗”）酿造的清酒中所具有的青草般的特征香气进行了研究。通过将气味特性和科瓦茨保留指数与标准化合物进行比较，发现4 - 巯基 - 4 - 甲基戊 - 2 - 酮（4MMP）对这种特征香气有贡献。使用“水之穗”这种低谷蛋白大米以及“吟大见”（对照品种）进行清酒酿造，结果表明，在整个发酵期间，“水之穗”清酒样品中的4MMP浓度高于“吟大见”样品中的浓度。最终“水之穗”清酒中的浓度是“吟大见”的两倍。为了研究4MMP的形成机制，通过超高效液相色谱串联质谱分析法，对清酒及其原料（大米和酒曲）中的假定前体物质4 - S - 半胱氨酰 - 4 -甲基戊 - 2 - 酮（cys - 4MMP）和4 - S - 谷胱甘肽基 - 4 - 甲基戊 - 2 - 酮（glut - 4MMP）进行了分析。在所有样品中均未检测到cys - 4MMP，而glut - 4MMP存在于清酒及其原料中。在几乎整个发酵期间，清酒中glut - 4MMP的浓度低于“吟大见”中的浓度，这表明在低谷蛋白大米“水之穗”的醪液中，前体物质向4MMP的转化比在“吟大见”中更有效。研究了在酒精发酵过程中，从前体物质模型培养基中释放4MMP的情况。在对照（不添加）中未观察到4MMP的释放，而添加前体物质后，随着发酵的进行，4MMP的释放量增加。这表明清酒酵母可从cys - 4MMP和glut - 4MMP两者生成4MMP。测定了清酒中4MMP的感知阈值为1.2 ng/L。
