Elemental composition of green tea infusions depending on the method of their brewing

Abstract

Green tea infusions are a source of many bioactive compounds as well as elements, both nutrients and toxic ones. In this study, we assessed the content of elements in green tea infusions depending on the brewing time and their pH values. In instrumental analysis we used atomic absorption spectrometry. Elements such as Ca (calcium), Cu (copper), K (potassium), Mg (magnesium), Na (sodium), Fe (iron), Mn (manganese), Zn (zinc), and toxic Al (aluminium) were quantified in green tea infusions with pH = 6 and pH = 2, and after infusion times of 5, 10, and 20 min. The mean value of the elements in 250 mL of beverage was the following: (mg) K—114.68 ± 33.27, Ca—18.48 ± 334.24, Na—4.00 ± 0.92, Mg—2.71 ± 0.65, and (µg) Al 1266.53 ± 0.56, Mn—488.19 ± 320.46, Zn—46.65 ± 5.18, Fe—34.30 ± 10.96, Cu—5.00 ± 0.01. From 1 g of raw material, the following amounts of elements were leaching, µg/g: Al—ND-1479.89, Ca—190.42–7650.09, Fe—9.52–42.30, K—42108.07–108337.90, Mg—661.14–1760.73, Mn—58.82–931.19, Na—ND-1959.09, Zn—2.50–16.83. Cu content was at the LOD of the method. Based on the statistical analyses, significant differences between the sample series were found. Al and Mn significantly positively correlated with most of the elements studied. Both pH and brewing times affected the amount of extracted elements, especially in the case of Al, Ca, and Mn. The amount of K did not change much during the preparation of the brews. The acidic environment allows a large amount of leaching of Al and Mn into the infusion.