Within this graduation thesis we determined the antioxidant capacity (AOC) and total phenolic compounds (TPC) in black tea. We have examined how different methods of preparing tea infusions affect AOC and TPC. The basic tea infusion was prepared with 2.0 g of each tea sample and 20 mL of tap water at 100 °C. We left the samples in the water for 3 minutes. We than changed the parameters of tea preparation and compared the AOC and TPC of such samples with the ones from the basic tea infusions. The AOC was determined using the DPPH• radical scavenging capacity assay and TPC were determined by the Folin – Ciocalteu method. We found out that some preparation procedures have a greater influence on the AOC and TPC than others. We determined that a longer extraction time has a positive effect on both, the AOC and TPC of a tea infusion. The use of distilled water has a small but positive effect on most of the tea samples. The addition of milk negatively affected both, the AOC and TPC. The preparation of tea infusions using different amounts of water (different tea – to – water ratio) did not show any significant effect on the AOC or TPC. Based on the overall results of all the analyses of the preparation of tea infusions, we came to the conclusion that the easiest way to increase values of AOC and TPC is by prolonging the extraction time.
|
