本研究应用一种更为快速、准确、无损的低场核磁共振技术来测定茶叶的含水量。实验通过标定6种不同质量的纯水标样的FID信号幅值,拟合出水分含量与FID信号幅值的直线方程,再选取5个茶叶样分别测量其FID信号幅值,根据拟合直线换算成茶叶含水量,同时将核磁共振法测得的含水量结果与国家标准的103℃恒重法比较分析。实验结果表明：应用低场核磁共振测定茶叶含水量方便迅速,结果稳定准确,通过与国家标准的茶叶含水量103℃恒重法对比发现,核磁共振法测得的含水量偏高不到1%,这是由于烘干法无法将茶叶内部的结合水完全烘干所致,而核磁共振法测量的是茶叶内部游离水和结合水的总和。

Research on the determination of water content of tea by using low field NMR instrument has been conducted. The purpose is to develop a more rapid, accurate and nondestructive method to measure the water content of tea. In this experiment, six pure water samples with different weights were prepared as standard samples to test their FID signals. FID signal data were fitted to a line equation. Five tea samples were prepared to test their FID signals and calculate the water content of tea by the fitting equation, then compare the results with national standard method. Result showed that the determination of water content of tea by low field NMR could obtain a more rapid and accurate result. The result by low field NMR is about 1% higher than that of the national standard method, because the drying method can’t dry the bound water completely,but the NMR measures both the content of free water and bound water.