Comparative Evaluation of Functional Components and Antioxidant Activity between Green and Black Tea Extracts
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Abstract:
As one of the globally recognized nonalcoholic beverages, tea and their products have high nutritional values and unique health benefits. In this study, the antioxidant activities of two types of tea, homemade green and black teas, were measured and compared using the 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl (DPPH), oxygen radical absorbance capacity (ORAC), and cellular antioxidant activity (CAA) methods. The difference between the contents of the functional components of green and black tea extracts was also measured. The results showed that both the homemade tea extracts had high antioxidant activity; however, their antioxidant activity decreased with increasing fermentation time. IC50 of DPPH ingreen tea (14.58 μg DM/mL) was lower that in black tea (24.14 μg DM/mL); while ORAC and CAA values of green tea (5313.92 ± 318.75 μmol TE/g DM and 26.23 ± 0.43 μmol QE/100 mg DM, respectively) were higher than those of black tea (3684.14 ± 233.59 μmol TE/g DM and 16.41 ± 0.17 μmol QE/100 mg DM, respectively). The results indicated that with increasing fermentation time, the total dry matter of tea extracts decreased; in particular, the amount of tea polyphenols (TP) showed the highest decrease among the functional components. Thus, tea polyphenols are the major functional components that affect the antioxidant activity of tea extracts.
