FORMATION OF THE CHARACTERISTIC AROMA COMPONENTS OF MISO BY YEASTS AND THERMAL DEGRADATION OF THESE COMPONENTS

从化学分析和统计分析的结果证实了HEMF（4-羟基-2（或5）-乙基-5（或2）-甲基- 1-3(2H)-呋喃酮）对大米味噌香气的感官评价有显著的贡献。通过对未添加预培养酵母（Zygosaccharomyces rouxii）和未添加预培养酵母（miso）的miso进行比较，研究了miso中HEMF的形成与酵母生长的关系。在添加酵母的味噌中，制备后第7天，虽然酵母细胞数量为1.6X10^5个细胞/g，但未检测到HEMF。在无酵母味噌中，当酵母细胞数为2.2X10^3个细胞/g时，检测到0.06 ppm的HEMF。在这些misos中检测到HEMP时的pH值分别为5.57和5.59。这些结果表明，在含有高浓度还原糖和NaCl的味噌中，当pH值低于5.6时，会产生HEMF。据报道，HEMF纯化后是不稳定的。据报道，蛋氨酸会导致味噌加热时产生难闻的气味。以HEMF和蛋氨酸为原料，研究了味噌加热后香气变化的机理。加热后的味噌悬浮液中HEMF浓度在加热初期呈下降趋势。加入HEMF的模型溶液中，HEMF浓度在加热初期呈下降趋势，为。经实验证实，添加了hemf的模型溶液经加热可生成2-丙酮和2,3-己二酮。加热后的味噌悬浮液中蛋氨酸的浓度没有变化。在加热后的味噌悬浮液中鉴定出甲基硫醚。在添加了甲硫乙醇的模型溶液中，加热后的甲硫乙醇无法检测到甲硫乙醇。在加热味噌混悬液中检测到的Methonol不是味噌混悬液中Methonol的产物。

HEMF(4-hydroxy-2(or 5)-ethyl-5(or 2)-methy1-3(2H)-furanone) was confirmed to contribute remarkably to sensory evaluation of rice-miso aroma from the results of chemical and statistical analyzes.The relationship between the formation of HEMF and the growth of yeasts in miso was investigated, comparing miso to which precultured-yeasts(Zygosaccharomyces rouxii) were added with miso to which they were not added. In yeast-added miso, HEMF was not detected by the 7th day after the preparation although the number of yeast cells was 1.6X10^5 cell/g. In miso without yeast, 0.06 ppm HEMF was detected when the number of yeast cells was 2.2X10^3 cell/g. The pH levels when HEMP was detected in these misos were 5.57 and 5.59 respectively. These results suggest that in miso containing a high concentration of reducing sugar and NaCl, HEMF was produced when the pH level fell to less than 5.6.HEMF was reported to be unstable when it was purified. Methionol was reported to contribute to the unpleasent odor produced by heating of miso. The meckanisms of the change of aroma in miso by heating were investigated with regard to HEMF and Methionol. The concentration of HEMF in the heated miso suspension decreased in the initial time of heating. The concentration of HEMF in the HEMF-added model solution decreased in the initial time of heating, to. 2-Propanone and 2,3-hexandione were confirmed to be produced from the HEMF-added model solution by heating. The concentration of Methionol in the heated miso suspension did not changed. Methional was identified in the heated miso suspension. Methional was not able to be detected in the Methionol-added model solution which was heated. Methional which was identified in the heated miso suspension was confirmed to be not product from Methonol in miso suspension.