Concentrations of selected metals (Cu, Mn, Zn, Cd) in tea leaves were investigated. Samples included black, green, and other (red, white, yellow, and oolong) teas. They were purchased on a local market but they covered different countries of origin. Beverages like yerba mate, rooibos, and fruit teas were also included in the discussion. Metal determinations were performed using atomic absorption spectrometry. In black teas, Mn/Cd ratio was found to be significantly higher (48,091 ± 35,436) vs. green (21,319 ± 16,396) or other teas (15,692 ± 8393), while Cd concentration was lower (31.4 ± 18.3 μg/kg) vs. other teas 67.0 (67.0 ± 24.4). Moreover, Zn/Cu and Cu/Cd ratios were, respectively, lower (1.1 ± 0.2 vs. 2.2 ± 0.5) and higher (1086 ± 978 vs. 261 ± 128) when comparing black teas with other teas. Intake of each metal from drinking tea was estimated based on the extraction levels reported by other authors. Contributions to recommended daily intake for Cu, Mn, and Zn were estimated based on the recommendations of international authorities. Except for manganese, tea is not a major dietary source of the studied elements. From the total number of 27 samples, three have shown exceeded cadmium level, according to local regulations.
Tea is an infusion prepared from Camellia sinensis leaves originating from China and some parts of India. Nowadays, this evergreen shrub is grown in many other countries, such as Japan, Indonesia, Sri Lanka, Kenya, and Vietnam. The conditions of growing tea shrub, e.g., location, climate, and soil, have an impact on the taste and properties of the final beverage [1].
Tea is the one of the most popular beverages in the world. Six types of tea are distinguished as follows: green, white, yellow, oolong (blue tea/semi-fermented tea), red, and black. These types differ in terms of oxidation level, color of leaves, and infusion. The oxidation level of tea determines the color of leaves and infusion and it depends on the way the fermentation was carried out. The most popular types of tea are the following: green tea, which preserves the properties of fresh leaves to the highest degree, and black tea, which is obtained after full fermentation of fresh leaves.
Among other components, tea leaves consist of tanning agents, alkaloids, amino acids, pigments, and trace amounts of mineral compounds. Trace elements present in tea leaves play an important role in human metabolism [2]. They can be released from leaves to the infusion. Thus, tea leaves may become the source of metals in human diet. Some of the metallic elements, such as copper, manganese, and zinc are essential for basic processes in the human body while others (like cadmium) are toxic. The main aim of our study was to determine the content of copper, manganese, zinc, and cadmium in tea leaves and to find out if there are any significant differences among the teas of different types and countries of their original
Concentrations of selected metals (Cu, Mn, Zn, Cd) in tea leaves were investigated. Samples included black, green, and other (red, white, yellow, and oolong) teas. They were purchased on a local market but they covered different countries of origin. Beverages like yerba mate, rooibos, and fruit teas were also included in the discussion. Metal determinations were performed using atomic absorption spectrometry. In black teas, Mn/Cd ratio was found to be significantly higher (48,091 ± 35,436) vs. green (21,319 ± 16,396) or other teas (15,692 ± 8393), while Cd concentration was lower (31.4 ± 18.3 μg/kg) vs. other teas 67.0 (67.0 ± 24.4). Moreover, Zn/Cu and Cu/Cd ratios were, respectively, lower (1.1 ± 0.2 vs. 2.2 ± 0.5) and higher (1086 ± 978 vs. 261 ± 128) when comparing black teas with other teas. Intake of each metal from drinking tea was estimated based on the extraction levels reported by other authors. Contributions to recommended daily intake for Cu, Mn, and Zn were estimated based on the recommendations of international authorities. Except for manganese, tea is not a major dietary source of the studied elements. From the total number of 27 samples, three have shown exceeded cadmium level, according to local regulations.
Introduction
Tea is an infusion prepared from Camellia sinensis leaves originating from China and some parts of India. Nowadays, this evergreen shrub is grown in many other countries, such as Japan, Indonesia, Sri Lanka, Kenya, and Vietnam. The conditions of growing tea shrub, e.g., location, climate, and soil, have an impact on the taste and properties of the final beverage [1].
Tea is the one of the most popular beverages in the world. Six types of tea are distinguished as follows: green, white, yellow, oolong (blue tea/semi-fermented tea), red, and black. These types differ in terms of oxidation level, color of leaves, and infusion. The oxidation level of tea determines the color of leaves and infusion and it depends on the way the fermentation was carried out. The most popular types of tea are the following: green tea, which preserves the properties of fresh leaves to the highest degree, and black tea, which is obtained after full fermentation of fresh leaves.
Among other components, tea leaves consist of tanning agents, alkaloids, amino acids, pigments, and trace amounts of mineral compounds. Trace elements present in tea leaves play an important role in human metabolism [2]. They can be released from leaves to the infusion. Thus, tea leaves may become the source of metals in human diet. Some of the metallic elements, such as copper, manganese, and zinc are essential for basic processes in the human body while others (like cadmium) are toxic. The main aim of our study was to determine the content of copper, manganese, zinc, and cadmium in tea leaves and to find out if there are any significant differences among the teas of different types and countries of their origin.
Materials and Methods
Tea samples (n = 27) were purchased on a local market in southern Poland. All samples were based on pure tea leaves, without additives or flavors. The set of samples included teas in the form of loose leaves as well as ground ones in tea bags. Samples were divided according to their type and country of origin. Among the samples, there were 12 samples of black tea, eight samples of green tea, two samples of red tea, two samples of white tea, two samples of oolong tea, and one sample of yellow tea.
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