# The Effect of Brewing Time on the Antioxidant Activity of Tea Infusions
## 4 Discussion  
Infusion preparation conditions determine the health-promoting values of tea as they affect the content of active ingredients. Tea brewing time has a decisive influence on the TPC of the infusion [23]. The presented results of our research have shown that extending the brewing time from 5 to 10 or 15 min increased the TPC of infusions from green, white, yerba mate, raspberry and white lychee plum tea infusions. Over 50% of polyphenols infuse into the brew within the first five minutes of brewing [23; 26]. Theoretically, health benefits associated with drinking tea stem from polyphenols present in the infusion, so longer tea brewing time is beneficial to consumers. However, the content of polyphenols, and in particular tannins, affects the taste of tea infusions, and, if excessive, can make tea too astrinert [27; 28]. Therefore, the maximum recommended infusion time for commercial teas is five minutes. Studies by [PERSON] et al. [29] demonstrated that TPC in non-fermented, semi-fermented and fermented tea infusions increased to 15 min of brewing, but afterwards decreased. The increase of TPC within 15 min can be attributed to the release of polyphenols into hot water, but following this interval TPC may decrease because polyphenols are destroyed due to prolonged thermal processing or because phenolic compounds in tea have different solubility [30]. [PERSON] and [PERSON] [31] found that TPC in tea infusions increased with longer brewing time. Simultaneously, these authors observed that most polyphenols present in infusions after ten minutes of brewing were extracted during the initial five minutes, irrespective of tea type (black, green, white, yellow, oolong or Pu-erh). [PERSON] et al. [11] did not find any significant increase in the polyphenols content of infusions after five and ten minutes of brewing for black, green, white, chamomile and mixed berry/hibiscus teas. In contrast, [PERSON] et al. [27] observed the highest TPC in green tea infusions brewed for ten minutes at 100 \({}^{\circ}\)C. Similarly, according to [PERSON] et al. [32], ten minutes of brewing time is necessary to achieve the maximum polyphenols content and antioxidant activity of the infusion. Flavonoids leach into the tea infusion also largely depends on tea brewing time but also the content and structure of flavonoids in the plant raw material [30], as demonstrated by our own research. For instance, myricetin levels are higher in green tea than in black tea. Its content likely decreases with an increase in fermentation, but also with longer brewing time [30]. [PERSON] et al. [29] recorded the maximum flavonoid content of non-fermented, semi-fermented and fermented tea infusions after 15 min of brewing. The increase and decrease in the flavonoid content of infusions after 10 and/or 15 min of brewing can be both due to their different release rates and different solubility. Excessive flavonoids content of the infusion can adversely affect taste, as some flavonoids (e.g., naringin and neohesperidin) are very bitter, while others (e.g., hesperidin) have no distinct taste [18]. The taste of flavonoids depends on the glycosidic chain structure. Anthocyanins are natural dyes categorised as flavonoids responsible for the blue, purple or red colour of fruits and flowers [33]. These compounds have low stability due to their sensitivity to many environmental factors [34]. Brewing time, but also water temperature, determines the content of anthocyanins in tea infusions, as demonstrated by [PERSON] et al. [35]. Their study revealed a linear increase in the anthocyanins content of fruit teas (blackberry, rose hip and bilberry) when the brewing time was extended to 12 min. We found that, generally, after ten minutes of brewing, the level of anthocyanins in tea infusions increased insignificantly or remained unchanged.