Nitrogen in Black Tea Tannin

Abstract

The purified two tannin, fractions, which were formed by the oxidation and polymerization of catechins, were isolated from black tea. One fraction contained 1.02% of nitrogen and the other 8.33%.
It is, therefore, supposed that the oxidized quinone-type tannin made a melanoidin pigment as the result of the combination with amino acid and protein and spoiled the quality of black tea.