It was formerly derived by fermentation of carbohydrates but is now made synthetically by aldol condensation of acetaldehyde or by oxidation of petroleum gases.

以前它是由碳水化合物发酵得到，现在由乙醛醛醇缩合或石油气体氧化的合成方法制得。

youdao

Results of enzymatic oxidation showed that the highest content of theaflavins (15.05%) was formed at 80 minutes fermentation with polyphenol oxidase.

酶促氧化结果表明，发酵80分钟时，茶黄素的生成量最高(为15.05%)。

youdao

It is worth mentioning that the drink without the oxidation of tea fermentation, the effect is more obvious, it is because of these active ingredients in tea tea to retain more of the reason.

值得一提的是，饮用未经氧化、发酵的普洱茶，其效果更为明显，这是因为这类茶叶保留茶叶中活性成份较多的缘故。

youdao