Major minerals in teas (green, black, fruit, herbal)

Tea is, next to water, the most widely consumed beverage worldwide. It contains many important substances and elements for the human health. Around 20-30% of the dry mass of tea leaves are flavonoids (polyphenols, tanning agents). In this group the catechines are the major group. They are especially useful for enhancing health as they reduce the cholesterol-content and are further known as antibacterial and show anti-oxidant behavior. Especially green tea contains higher amounts of catechines. One of the main ingredients in black and green tea is caffeine, a stimulating substance which improves the mood, enhances the cognition and has analgic funtion. 1-4% of dry tea leafs of black or green tea are amino acids (especially Theanin, responsible for the fresh and good taste of tea, also acting comforting). Further ingredients are vitamins (A, B1, B2, C and K), volatile oils and several minerals as aluminium, calcium, fluorine, iron, sodium, magnesium, manganese, potassium and zinc. Especially green tea contains a lot of potassium, an element important for healthy muscles (also for a strong heart), magnesium and manganese (important as activators for enzymes in the cell metabolism) and zinc (for the right functioning of the metabolism). Aluminium, though, is in contrast to the stimulating effect of plant growth, a powerful neurotoxicant for humans. In this investigation the mineral content of several samples of different kinds of tea (black tea, green tea, fruit tea and herbal tea) have been determined. Tea powder from tea bags have been used as raw materials. The dry mass content has been measured. After a microwave assisted digestion with nitric acid and water at temperatures up to 220°C, the element concentrations have been measured with ICP-OES (inductively coupled plasma-optical emission spectroscopy) as it is a fast and reliable method with low detection limits. All samples have been prepared in duplicate. Additionally the element concentrations have also been determined in freshly prepared tea infusions. In all samples high amounts of calcium and magnesium could be found. And, as expected, differences in the elemental composition could be seen between the different classes of teas. Green and black tea contain more aluminium and manganese than fruit or herbal teas. Sodium is contained especially in herbal tea. This research results have been produced in cooperation with other universities – one of them even in another country.