In Taiwan, the manufacturing of black tea has become prosperous year after year and its progress is very remarkable. However, we must acknowledge the superiority of the tea made in India and Ceylon to that which is made in Taiwan. The quality of black tea is due to its colour, taste, and flavour in the liquors. In the process of manufacturing, that is, in the operation. of withering, rolling and fermentation, tannin is oxidized by enzyme and it is said tat the unique colour, flavour and taste are thus produced. We intend to contribute to the improvement of the quality of black tea from both sides by studying tannin and enzyme, which are the chief ingredients of raw tea-leaves.
About the tannin of tea leaves, several reports⁽¹⁾ have been published up to the present time. One of the writers, Osima⁽²⁾ has made a report about the tannin of Taiwan raw tea leaves. There are the reports by, Mann and Aso about the enzyme of tea leaves, while about the oxidizing enzyme of Taiwan raw tea leaves Hayasi⁽³⁾ has made a report. While recently very, interesting results are reported by Lamb and Roberts.⁽⁴⁾
Now when we make the enzyme solution of tea leaves act on the pure colourless tannin, the tannin becomes reddish brown, like the infusion of black tea. Thus we can infer that the colour of black tea is produced, by the change of tannin by enzyme. Moreover, by separating the substance produced by the change of tannin we can ascertain that it is an oxidated product. We have just taken the first step in this study and report the results which have been obtained so far.

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