Changes in Metal Contents during the Manufacturing Process of Sencha and in Different Positions of the Tea Shoot

Changes in metal contents during the manufacturing process of Sencha and in different positions of the tea shoot were investigated using inductively coupled plasma (ICP)-mass spectrometry (MS) and ICP-AES (atomic optical emission spectrometry) methods. The contents of Ba, Cu, Fe, Ni and Zn increased after the primary drying process, while that of Sr decreased after the final rolling process. Only Zn showed significant difference at 5% level between the contents of fresh leaves and crude tea, suggesting that the increase of Zn should be taken into consideration for the differentiation of the geographic origin of the tea. The contents of Al, Ba, Ca, Co, Mn and Sr were richer in the lower position of the tea shoot, while those of Cu, Fe, Mg, Ni, P and Zn were richer in the upper position of the tea shoot. The contents of K and Rb hardly changed regardless of the position. The stem showed a unique metal composition compared to that of the leaf. This result suggests that a tea sample processed from the stem should not be used for the differentiation of the geographic origin of the tea.