Formation of terpenoids contributing to tea aroma.

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Terpene alcohols are main components in tea aroma, which are formed during tea processing. The estimation for the aroma compound precursor in tea leaf and the formation of the alcohols by enzymatic reaction are investigated. 1) Geranyl- -D-glucoside has been supposed to be one of the precursor of geraniol formation. This glycoside was synthesized and its structure was established from chemical and spectrometric analyses.2) In order to use a crude tea enzyme system, the aceton powder of tea leaf were prepared. The -glucosidase activity in the powder was measured by p-nitrophenol method and its activity was 0.8u/g.3) To certify the presence of aroma precursor, hot water extract of green tea was prepared, from which volatile aroma compounds were taken off by steam distillation under the reduced pressure and by the solvent extraction.4) The water extract was treated with tea leaf aceton powder in sodium citrate buffer solution. The newly formed aroma volatiles are separated and identified by GC and GC-MS equipped with capillary column. With the expecting terpene alcohols such as linalool, linalool oxide and geraniol, benzyl alcohol and phenylethyl alcohol are identified, which are known as main component of tea aroma. These results suggest that all main components in tea aroma are formed their precursors by enzymatic reaction.5) The synthesized geraniol- -D-glucoside was also hydrolysed by tea leaf aceton powder under the same condition described above. The product was shown to be 2:1 mixture of geraniol and its isomer, nerol. The yield of terpene alcohols from the glucoside was culculated to be 10.6% from their peak area on GC.