The Effect of Brewing Time on the Antioxidant Activity of Tea Infusions

Many studies have found that tea has an antioxidant, anti-inflammatory, anti-cancer, anti-obesogenic and anti-diabetic effect, mostly associated with the content of anti-oxidant compounds. Polyphenols, being the main secondary metabolites in tea, are often considered the physiological markers determining a tea’s quality. Apart from the tea production process and tea components, brewing conditions can also influence the levels of antioxidants in tea. This study aimed to verify whether the brewing time of various tea types (5, 10 and 15 min) affects the level of extraction of antioxidant compounds into infusions and their antioxidant activity. We examined 11 types of tea: green leaf tea, green tea bags, white tea bags, black tea bags, red tea bags, black leaf tea, yerba mate, raspberry tea bags, butterfly pea flower (Clitoria ternatea) tea, white lychee plum tea and hibiscus flower tea. Total polyphenol (TPC), flavonoids and anthocyanins content, as well as determination of antiradical and antioxidant capacity with DPPH radical and ABTS radical cation, were determined using spectrophotometric assays. Due to the antioxidant activity of tea infusions, the optimum brewing time for green tea (leaf and bags), black tea (leaf and bags), butterfly pea flower tea, white tea, white lychee plum tea, raspberry tea and yerba mate is 15 min. Red tea brewing time should be ten minutes, and for hibiscus flower tea it should be five minutes. The results refer to the brewing temperature recommended by tea manufacturers.