Determination of Moisture in Tobacco Leaves during Curing Process by Low-field NMR

In order to fully understand the change of moisture content in different positions of tobacco leaves during curing process,and to improve the moisture detection efficiency of tobacco leaf during curing,using the upper leaf of Qinyan96 as test material,Low-field NMR was used to determine the moisture content in lamina and midrib.The results were compared with those determined by a conventional oven method.The results showed that:(1) The map of different positions of tobacco leaves showed that there were 3 states of water in lamina,bound water T₂₁(0.1-1 ms),semi-bound water T₂₂(1-10 ms) and free water T₂₃(100-1000 ms).There were 2 states of water in midrib,bound water T₂₁(1-10 ms) and free water T₂₂(100-1000 ms).(2) The inversion spectrum of lamina and midrib has an extremely significant positive correlation with the water mass and moisture content of dry base (the coefficient of determination are in turn 0.9847,0.9929,0.9952,P<0.01).(3) Comparing with the conventional oven method,the stability of Low-field NMR was better,which is suitable for rapid and accurate detection of the lamina and midrib moisture content of tobacco leaves during curing.