低场核磁共振法测定烘烤过程中烤烟主脉的水分

摘要

为了准确掌握烘烤过程中烟叶主脉水分变化情况，利用低场核磁共振法测定了烘烤过程中烤烟主脉含水率及水分状态，并与烘箱干燥法含水率检测结果进行对比分析。结果表明：①鲜烟叶及烘烤过程中烟叶主脉含有结合水T21（1～10 ms）和自由水T22（100～1000 ms）；随着烘烤进程的推进，自由水信号幅值M22与水分总信号幅值M20呈现降低趋势，结合水信号幅值M21呈现先升高后降低趋势。②线性回归分析表明，反演谱曲线总信号幅值分别与主脉水分质量、干基含水率呈极显著线性正相关（决定系数分别为R2=0.9979，R2=0.9983，P＜0.01），由回归方程可得到烘烤干燥过程中主脉含水率。③与烘箱法相比，低场核磁共振法检测结果稳定性较好，适用于烘烤过程中烟叶主脉含水率的快速、准确检测。%In order to study the moisture variations in midrib of tobacco leaves during flue-curing, low-field nuclear magnetic resonance(LF-NMR) was used to determine the content and state of moisture, and the results were compared with those determined by a conventional oven method. The results showed that: 1) The moisture in midrib of fresh green tobacco leaves included bound water T21(1-10 ms) and free water T22(100-1 000 ms). During flue-curing, the signal amplitude of free water M22 and total water M20 decreased, and the signal amplitude of bound water M21 increased first then decreased. 2) Linear regression analysis indicated that the total signal amplitude of inversion spectrum positively correlated to the moisture content and dry weight base moisture content at a significant degree (coefficient of determination R2=0.997 9, R2=0.998 3, P<0.01). The moisture content in leaves during flue-curing could be obtained by the regression equation obtained. 3) Comparing with the oven method, the stability of LF-NMR was better. LF-NMR is thus suitable for the rapid and accurate determination of moisture contents in midrib of tobacco leaves during flue-curing.