Development of antioxidants rich herbal tea bags and determination of the effect of infusion conditions on antioxidant activities

Abstract

Antioxidants protect cells from oxidative damage. The study was aimed to develop antioxidant-rich herbal tea bags and determine the effect of infusion conditions on antioxidant potential. Herbal tea bags were prepared by incorporating different proportions of Osbeckia octandra (Heen bovitiya) leaves, Camellia sinensis (green and black tea) leaves, Vanilla planifolia (Vanilla) pods, Zingiber officinale (Ginger) rhizomes and Allium sativum (Garlic) bulbs. Extracts were obtained at 80 ⁰C, 90 ⁰C and 100 ⁰C for 7 minutes and at 100 ⁰C for 3, 5 and 7 minutes. Total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric-reducing antioxidant power (FRAP) assays were determined for each extract. Data was analyzed with one sample t-test. It was found that TFC, TPC and antioxidant activity were significantly different at different infusion conditions (p<0.05). At constant infusion time (7 minutes), TFC, TPC and antioxidant activity of O. octandra incorporated black tea bags were higher when brewed at 100 ⁰C compared to 80 ⁰C and 90 ⁰C while they were higher for O. octandra incorporated green tea bags when infused at 80 ⁰C compared to 90 ⁰C and 100 ⁰C. At constant infusion temperature (100 ⁰C), values for black tea bags were higher when brewed for 3 minutes compared to 5 and 7 minutes whereas it was higher for green tea bags when infused for 7 minutes compared to 3 and 5 minutes. Hence, it was concluded that antioxidant activity of each extract was significantly higher than tea samples developed without addition of O. octandra leaves. Further, to obtain antioxidant rich tea, O. octandra incorporated black tea should be brewed in boiling water (100 ⁰C) for a short period (3 minutes) and O.octandra incorporated green tea should be brewed for a long period (7 minutes) at a low temperature (80 ⁰C).