Differences in aluminium content of various tea powders (black, green, herbal, fruit) and tea infusions

Trace elements play an important role in human health. Some trace elements are essential, but some are harmful – especially in higher concentrations. Aluminum is not considered as an essential element for human beings, but has, in contrary, been correlated with various human pathologies for example Dementia, Parkinson and Alzheimer disease. Its uptake is mainly via food products for example tea, in the form of a food additive or via coming in contact with aluminium containing devices used during food processing and storage. The permissible weekly dose for an adult is 60 mg of aluminium. Although no limit concentration for aluminium is given in the Codex Alimentarius Austriacus, the determination of the aluminium content in food and beverages is of great concern. In this study, different kinds of tea (black tea, green tea, fruit tea and herbal tea) were analyzed for their aluminium contents. The powders were brought into solution with a microwave assisted digestion unit at temperatures up to 220°C with diluted nitric acid as digestion medium. Furthermore, the aluminium concentrations have been determined in freshly prepared tea infusions in order to examine the extractable amount. The aluminium content in all solutions has been determined with ICP-OES (inductively coupled plasma-optical emission spectroscopy). Statistically significant differences between the different kinds of tea could be found, whereas the real tea types (green and black tea) contain more aluminium than fruit or herbal teas. The mean values of total concentrations of aluminium found were (0.91 ± 0.31) g/kg for green tea, (0.76 ± 0.38) g/kg for black tea, (0.23 ± 0.09) g/kg for herbal tea and (0.22 ± 0.08) g/kg for fruit tea. For the tea infusions (4.33 ± 0.35) mg/L for green tea, 4.40 mg/L for black tea, 0.52 mg/L for herbal tea and (0.12 ± 0.02) mg/L for fruit tea. These results are in good agreement with literature data.