title: Effect of different brewing times on antioxidant activity and polyphenol content of loosely packed and bagged black teas (Camellia sinensis L.).
abstract: 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.
  
  
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Liver and Gastrointestinal disease research center, Tabriz University of medical sciences, Tabriz-Iran.
authors.forename: Zeinab
authors.initials: Z
authors.lastname: Nikniaz
authors.affiliation: Nutrition Research Centre, Tabriz University of Medical Sciences, Tabriz-Iran.
authors.forename: Reza
authors.initials: R
authors.lastname: Mahdavi
authors.affiliation: Nutrition Research Centre, Tabriz University of medical sciences, Tabriz-Iran.
authors.forename: Seyed Jamal
authors.initials: SJ
authors.lastname: Ghaemmaghami
authors.affiliation: Student Research Committee, Tabriz University of medical sciences, Tabriz-Iran.
authors.forename: Neda
authors.initials: N
authors.lastname: Lotfi Yagin
authors.affiliation: Tabriz Health Services Management Research Center, Tabriz University of Medical Sciences, Tabriz-Iran.
authors.forename: Leila
authors.initials: L
authors.lastname: Nikniaz
keywords: Antioxidant; Infusion time; Polyphenol; Tea