# The Effect of Brewing Time on the Antioxidant Activity of Tea Infusions
###### Abstract  
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 terntau_) 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.  
antioxidants; tea; DPPH; polyphenols; ABTS +
Footnote †: journal: Medical  
showed that polyphenols contained in tea reduce the rate of absorption and toxicity of toxic metals due to their capacity to chelate these metals and increase the antioxidant potential of the exposed organism [12; 14; 15; 16]. Polypphenols, being the main secondary metabolites in tea, are often considered the physiological markers determining tea quality [2].  
In addition to the manufacturing process, several factors, including the addition of fruits, spices and herbs also containing active antioxidants, have an influence on the content of antioxidants in tea [17; 18; 19]. The market offers beverages that do not contain tea leaves but, since they are brewed before drinking, are referred to as teas as well [20]. They contain, for instance, dried fruits, flower petals and pieces of herbs [17]. Such beverages are very popular on account of their taste and functional effects, which are also largely due to the polyphenol content [18].  
Apart from the tea production process and tea components, brewing conditions can also influence the levels of anti-oxidants in tea. Some studies show that phenolic compounds are relatively thermally stable; the rate of their degradation at 60 \({}^{\circ}\)C, 80 \({}^{\circ}\)C and 100 \({}^{\circ}\)C is 15-30% after four hours of exposure [21]. However, black tea infusions brewed at 70 \({}^{\circ}\)C contained less tannins than those brewed at 90 \({}^{\circ}\)C [22]. By contrast, [PERSON] et al. [23] demonstrated that brewing time and temperature affect the polyphenols content of black and green teas. Studies described in the available literature refer to the most often consumed teas--green tea and black tea. However, there is little information on the effect of brewing time on the antioxidant content of other types of tea, including herbal tea and fruit tea. Examining the effect of brewing time on the anti-oxidant activity of tea is justified since consumers should be aware of the optimum infusion brewing time to promote the healthy effects of tea. The 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 anti-oxidant activity. This study was carried out in conditions recommended by tea manufacturers (temperature and water volume).