Formation Mechanism of Tea Aroma and Search for Precursor

从茶叶热水浸提液中得到糖苷部分作为丁醇浸提液，经乙酰化分离各化合物。通过硅胶柱，薄层色谱显示BA-6和BA-7两个组分为单一化合物。前者经光谱分析鉴定为(Z)-3-己基- β - d -葡萄糖吡喃苷四乙酸酯。后者与合成的四乙酸苄- β - d -葡萄糖苷在物理和光谱方面完全相同。用新鲜茶叶制备的丙酮粉和市售的β - d -葡萄糖苷酶对绿茶进行酶解，得到粗糖苷部分。用盐酸进行非酶解也有应用。不同水解方式形成的挥发性化合物几乎相同，但β - d -葡萄糖苷酶水解后得到大量的苯甲醇和(Z)-3-己烯醇。这一结果与这些挥发物中β - d -糖苷作为香气前体在新鲜茶叶中的存在一致。

From the hot water extract of tea leaves, glycoside fraction was obtained as butanol extract, which was acetylated to separate each compounds. Through silica gel column, two fractions, BA-6 and BA-7, were shown to be single compound on the thin layer chromatogram.The former was identified with (Z)-3-hexenyl-beta-D-glucopyranoside tetraacete based on the spectrometric analyses. The latter was identical with synthetic benzyl-beta-D-glucopyranoside tetraacetate in all physical and spectrometric aspects.The crude glycoside fraction was also isolated from green tea which was enzymatically hydrolyzed with acetone powder prepared from fresh tea leaves and commercial beta-D-glucosidase. Non-enzymatic hydrolysis with hydrochloric acid was also applied. The volatile compounds formed after different hydrolysis were almost same, however, large amounts of benzyl alcohol and (Z)-3-hexenol were obtained after the hydrolysis with beta-D-glucosidase. This result is consistent with the presence of beta-D-glucosides of these volatiles in fresh tea leaves as aroma precursor.