Multi-Element Determination of Japanese Green Tea Leaves and Tea Infusions

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[Abstract] Tea is one of the most consumed beverages in the world. Tea can be divided into three kinds by whether it is made to ferment. In Japan, about 90,000tons of green tea were consumed in 2009. It is well known that there are many metals in tea leaves; however, few reports have determined the metal concentrations in tea infusions under drinking conditions, such as by extraction t imes. The aim of the present study was to quantify the concentrations of the elements of tea infusions after both one-minute and overnight extraction and to compare the contents between tea infusions and tea leaves. Tea leaves were obtained from five different production regions in Japan, Fukuoka, Kagoshima, Kyoto, Mie, and Shizuoka The concentrations of Ca, Cu, Fe, K, Mg, P, S, Zn, and 16 rare earth elements in green tea leaves, one-minute and overnight extractions were measured, but Cu was not detected in one-minute and overnight extractions. Major elements such as Ca, Fe, K, Mg, P, S, and Zn were extracted at 4.2, 3.8, 75.4 62.9, 29.0, 28.6 and 78.5％ in the one-minute extraction, and 3.3, 2.7, 89.0, 923, 38.1, 34.5 and 96.7％ in the overnight extraction, respectively. Therefore, as compared with one-minutee extraction, K , Mg, P, S, and Zn were extracted 118.6, 148.8, 131.8, 120.5, and 123.9％ by overnight extraction; however, the extractions of Ca and Fe were 76.9 and 71.5％. When sixteen rare earth elements in green teas were measured by ICP-MS, all elements were detected in the tea leaves from Fukuoka, Kagoshima, and Shizuoka, but seven elements were found in Mie and twelve in Kyoto. Sc was detected in one-minute and overnight extractions in all production regions. Ce, La, and Y in Kyoto tea and Ce, La, Nd, and Y in Fukuoka tea were detected from one-minute extraction, and Ce, Gd, La, Sm, and Y in Kyoto tea and Ce, Nd, La, and Y in Fukuoka tea were detected by overnight extraction. However, no elements except Sc were detected in one-minute and overnight extractions of tea from Kagoshima, Mie, and Shizuoka. In conclusion, Japanese green tea leaves include high contents of Ca, K, Mg, and P and about 2 to 5％ of Ca and Fe are extracted by one-minute extraction, although over 50％ Mg, K and Zn were extracted. In contrast, low concentrations of rare earth elements, except Sc, were extracted by both one-minute and overnight extractions.

Multi-Element Determination of Japanese Green Tea Leaves and Tea Infusions

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