Assessment of Elements in Black Tea Infusions by Brewing Method in Terms of their Nutritional Value

Tea infusions contain many valuable bioactive compounds and elements. The research is aimed at examining them in terms of nutritional value and determining the optimal conditions for their preparation. The study determined the content of Ca, Cu, Fe, K, Mg, Mn, Na, Zn, and Al in infusions of black tea, including bagged and loose leaf. An atomic absorption spectrometer was used for quantitative instrumental analysis. The obtained results were subjected to statistical analysis including PCA (Principal Components Analysis). The brewing time was 5, 10 and 20 min, and the pH value of the infusions was 2 and 6. It was found that, generally, both parameters increased the content of elements in infusions. The amount of elements extracted from 1 g of tea was within the range: Ca- ND (not detected)-7.23 mg, K- 15.1-32.3 mg, Mg- 0.11-0.86 mg, Na- ND-2.85 mg, and Al- ND- 1028 µg, Cu- 1.24-11.02 µg, Fe- ND-36.13 µg, Mn- 97.3-541.6, and Zn- 6.18-22.43 µg. These data were compared with the results for green tea infusions presented in a previous study. The results of this study suggest that the amount of Al and Mn in tea infusions should be controlled.