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Catechin is one of the substance in the tea leaves. Catechin was used to be categorized as tannin, since their components are almost the same (85% of the components are the same). However, there are some difference, like the plants contains tannin can be used for tanning leather, but catechin do not have that function . Catechin has bitterness in its taste, which is believed to be a center of green tea taste. Tea contains 10- 20% of catechin, which is the largest aqueous component in tea. There are more than 10 types of catechin, but the epigallokatechinegallete (EGCG) takes half of the catechin compornets. Epigallocatechin, epicatechingallate, and epicatechin are also contained. Catechin kills bacteria and odor, blocks the development of cancer, and lowers the blood pressure. During the fermentation of black tea, catechin is oxidized and develops its color to orange-red. The balance of catechin and amino acid is very important for the taste of tea. For green tea, if catechin is contained excessively high, the taste becomes too bitter. However, for black tea, it is better to have more catechin.

(Muneyuki Nakagawa)