Abstract
Black tea has the second-highest tannin content among teas, following gyokuro. Tannins are extracted during brewing to produce a pleasant, astringent, and beautiful color. Therefore, the tannin content is closely related to the quality of black tea. However, excessive consumption of foods containing tannins may be harmful to health; therefore, it is desirable to reduce tannin intake in people who consume large amounts of black tea daily. However, because tannins in tea are easily extracted using hot water, they must be removed after tea extraction to reduce the tannin content in black tea. One method of removing tannins after tea extraction involves adsorption using chitin and chitosan derived from crustacean shells. Tannins are plant-derived, high-molecular-weight compounds, and it has been reported that most tannins can be removed by treating tannin extracts from grapes and loquats with chitin. In this study, we investigated the adsorption behavior of black tea tannins on chitin and chitosan and evaluated their effectiveness in reducing the tannin content. The results showed that the addition of chitin and chitosan reduced the concentrations of polyphenols and tannins in black tea, indicating that both were effective for tannin removal. In addition, the adsorption isotherm results revealed a tendency for chitin to adsorb more tannins. These findings suggest that chitin and chitosan are effective agents for reducing tannin contents in black tea.
