Antioxidant Activity and Key Components of Three Grades of Black Tea
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Abstract:
Three grades of black tea were investigated to determine their antioxidant activity and main chemical components. The results showed that the antioxidant activity of black tea samples increased with increasing tea grade, with a significant difference between special-grade and second-grade black teas (p<0.05). In addition, antioxidant activity also varied significantly among five different categories of black tea. Composition analysis revealed that the levels of caffeine, polyphenols, catechins, non-ester catechins, gallic acid, and theaflavins increased gradually with increasing tea grade; whereas the polyphenol and ester catechin levels were consistent with the changes in antioxidant activity among the five different categories of black tea samples. Correlation analysis indicated that the antioxidant activity of black tea was significantly positively correlated with the levels of polyphenols, catechin, non-ester catechin, ester catechin, gallic acid, and theaflavins. Among them, the correlation of polyphenols with the four indicators of antioxidant activity were highly significant (p<0.01), and the correlation coefficients with T-AOC and DPPH exceeded 0.9. In conclusion, the grade of black tea can influence its antioxidant activity, while polyphenols and its derivatives can serve as key components for determining the grade and antioxidant activity of black tea.
