Hashiguchi Tomokazu, Izu Hanae, Sudo Shigetoshi
National Research Institute of Brewing, Higashi-hiroshima, Hiroshima, Japan.
Biosci Biotechnol Biochem. 2012;76(1):148-52. doi: 10.1271/bbb.110656. Epub 2012 Jan 7.
Ethyl carbamate concentrations in oak barrel-aged ume (Prunus mume) liqueurs were measured, and possible explanations for elevated levels were examined. The average concentration was 0.30 mg/L, significantly higher than in ume liqueurs not aged in oak (0.08 mg/L). Oak powder extracts were prepared from both untoasted and toasted oak powder by extraction with aqueous ethanol, and these were used to make ume liqueurs. Relative to a no-oak control, the ethyl carbamate concentrations were 3.8 and 11 times higher in the ume liqueur made with the untoasted and toasted oak powder extracts respectively. The extracts were loaded onto a C18 column, washed with water, and eluted with methanol. The (13)C-NMR spectra for the main constituents of the methanol elution fractions were consistent with those for lignin or fragments thereof. The methanol fractions were added to ume liqueur which was stored for 3 months. Relative to a control, the ethyl carbamate concentrations in the 3-month old liqueurs were found to be 1.2 and 4.6 higher for the untoasted oak-powder and the toasted oak-powder respectively. Ethyl carbamate was formed when lignin was added to a 40% aqueous ethanol solution that contained potassium cyanide. These observations suggest that lignin or fragments thereof promote the formation of ethyl carbamate.
测定了橡木桶陈酿的青梅利口酒中氨基甲酸乙酯的浓度，并对其含量升高的可能原因进行了研究。平均浓度为0.30mg/L，显著高于未在橡木桶中陈酿的青梅利口酒（0.08mg/L）。通过用乙醇水溶液萃取，从未烘烤和烘烤过的橡木粉中制备了橡木粉提取物，并用于制作青梅利口酒。相对于无橡木对照，用未烘烤和烘烤过的橡木粉提取物制成的青梅利口酒中氨基甲酸乙酯的浓度分别高出3.8倍和11倍。将提取物加载到C18柱上，用水洗涤，并用甲醇洗脱。甲醇洗脱级分主要成分的(13)C-NMR光谱与木质素或其片段的光谱一致。将甲醇级分添加到青梅利口酒中并储存3个月。相对于对照，发现3个月陈酿的利口酒中，未烘烤橡木粉和烘烤橡木粉制成的利口酒中氨基甲酸乙酯的浓度分别高出1.2倍和4.6倍。当将木质素添加到含有氰化钾的40%乙醇水溶液中时，会形成氨基甲酸乙酯。这些观察结果表明，木质素或其片段促进了氨基甲酸乙酯的形成。
