Formation Mechanism of Tea Aroma and Search for Precursor

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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.