effect of different brewing times on antioxidant activity and polyphenol content of loosely packed and bagged black teas (camellia sinensisl.)

objective: determination and comparison of the effect of infusion time on the antioxidant activity and total polyphenol contents of bagged and loosely packed black teas. materials and methods: for twenty loosely packed and eleven bagged tea samples, the antioxidant activity and total polyphenol content were analyzed using frap and folin-ciocalteau methods, respectively. the anova with tukey post-hoc test and independent t-test were used for statistical analysis. results: the antioxidant activity and polyphenol content of various brands of tea samples were significantly different. there were significant differences in the antioxidant activity of loosely packed teas between 5, 15(p=0.03), 30(p=0.02) and 60(p=0.007) minutes of brewing times. besides, there was a significant difference in antioxidant activity of bagged samples infused for 1 minute with four other infusion time points (p<0.001). in the case of polyphenol content, in loosely-packed tea samples, there were not significant differences between different brewing times (p=0.15). however, in bagged samples, the polyphenol contents of samples that were brewed for 1 minute were significantly lower than samples brewed for 3, 4, and 5 minutes (p<0.05). the antioxidant activity and polyphenol content of tea bags were significantly higher than those ofloosely-packed forms of the same brands at 5-min of brewing time (p<0.001). conclusion: the infusion time and the form of tea (loosely packed or bagged) were shown to be important determinants of the antioxidant activity and polyphenol content of black tea infusions in addition to the variety, growing environment and manufacturing conditions.