为明确当前我国茶叶中稀土氧化物总量(∑REOs)的现状及其溶出特性,分析了2007~2010年全国各地1245只茶叶中∑REOs的现状,并对不同含量及不同加工方式的茶叶进行溶出特性研究,结果表明:我国的茶叶中∑REOs中值约为2mg/kg,含量范围介于未检出至13.80mg/kg之间;90%以上的茶叶∑REOs小于5mg/kg,∑REOs残留量小于2mg/kg的茶叶比例为45%~65%;乌龙茶∑REOs残留量小于2mg/kg的茶叶比例低于50%,其他茶类如绿茶、花茶等,其∑REOs残留量小于2mg/kg的茶叶比例均在70%以上。当茶叶磨碎后其稀土浸出率均显著高于原样。茶叶加工过程中对芽叶的挤压程度可能是影响稀土浸出率的一个主要因素,各类茶的稀土浸出率为:针形茶<扁形茶<卷曲形茶<粉茶。茶汤中∑REOs以第1次冲泡最高,随着冲泡次数增加而递减。3次冲泡的总浸出率以乌龙茶粉最高,约为60%;其次是乌龙整茶,约为50%;针形绿茶的稀土浸出率最低,仅为5%。即使对总浸出率最高的乌龙茶粉而言,当乌龙茶粉干物质中的∑REOs达到6mg/kg,茶汤中的∑REOs也仍低于饮用水的限量指标。
In order to figure out the status of total amount of REE oxides(∑REOs) in tea and its leaching characteristics, the statues of ∑REOs in 1245 tea samples from 2007 to 2010 were statistical analyzed, and the leaching characteristics on the different ∑REOs with different processing technology were studied. The results showed that the Median of the ∑REOs in Chinese tea was about 2mg/kg, and the ranges were from ND to 13.80mg/kg, about over 90% of tea were under 5mg/kg. The ∑REOs in over half of Oolong teas were more than 2mg/kg, but for the other tea such as green tea, scented tea, less than 30% of those teas were more than 2mg/kg. When the tea was grinded, the leaching rate of the ∑REOs was increased significantly than the original tea. And the processing technology maybe was the major factor to impact on the leaching rate of the ∑REOs. There were some rules about the leaching rate followed by low to high: needle-shaped tea< flat-shaped tea (such as Longjin tea)< Curl-shaped tea < powdered tea. The ∑REOs was highest in the first brew, and then was decreased along with the 2nd and the 3rd brews. The Powdered Oolong tea has the highest leaching rate about the ∑REOs, the leaching rate was about 60%, but even the ∑REOs in the powdered Oolong tea has reached to 6mg/kg,the ∑REOs in the brew still under the limited value about the standard in drinking water. The needle-shaped tea has the lowest leaching rate about the
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