红茶、青茶和绿茶茶汤中硒溶出动态特性研究

Dynamic Characteristics of Selenium Dissolution in Infusions of Black Tea, Oolong Tea and Green Tea

为提供含硒茶的正确饮用方式,以红茶、青茶和绿茶作为研究对象,建立微波消解-原子荧光光谱法检测茶叶和茶汤中硒元素的定量分析方法,并揭示室温(25±2)℃下沸水浸泡的茶叶茶汤中硒元素溶出率随浸泡时间的变化规律。结果表明,茶叶和茶汤中硒元素检测的准确度、精密度、检出限、标准曲线线性范围和线性关系均符合定量分析方法学要求。所选红茶、青茶(乌龙茶)和绿茶中的硒元素含量分别为104.27、149.48μg/kg和179.93μg/kg。在室温(25±2)℃下,当茶水比为1∶200(g/mL),用沸水浸泡时,红茶、青茶(乌龙茶)和绿茶中硒溶出率达到峰值的时间分别为20、60 min和120 min,溶出率分别为68.31%、65.44%和67.51%。随着浸泡时间的延长,水温有规律下降的同时,茶汤中硒的质量浓度也以不同速率下降。当浸泡时间达到5 h时,红茶和青茶中硒的质量浓度分别下降到10.09μg/kg和10.35μg/kg,而绿茶中硒的质量浓度为83.31μg/kg。

The selenium in infusions of black tea,oolong tea and green tea was determined by microwave digestion-atomic fluorescence spectrometry to find a correct way for drinking selenium-rich tea.Meanwhile,the law of the rate of selenium dissolution in tea infused in boiling water changing with the time was investigated at(25±2)℃.The result showed that the accuracy,precision,limit of detection and linear range and correlation of standard curve of the determination of selenium in tea infusions were in accordance with the requirements of quantitative analysis methodology.The content of the selenium in black tea,oolong tea and green tea infusions was 104.27,149.48μg/kg and 179.93μg/kg,respectively.When the tea/water ratio was 1∶200(g/mL),selenium dissolution in black tea,oolong tea and green tea brewed in boiling water at(25±2)℃peaked at 20,60 min and 120 min,and dissolution rate was 68.31%,65.44%and 67.51%,respectively.The water temperature decreased regularly and the selenium concentration in tea infusions reduced at different rates over time.After 5 h,the selenium concentration in black tea,oolong tea,and green tea infusions decreased to 10.09,10.35μg/kg and 83.31μg/kg,respectively.