In order to find out the occurrence state of moisture in tobacco materials, the inversion spectra of spin-spin relaxation time (T2) of cut strips, cut stems, cut reconstituted tobacco were analyzed by low-field nuclear magnetic resonance (LF-NMR). The effects of moisture content and microstructure of the tobacco materials on the relaxation time and peak area of relaxation signal of water molecules in T2 inversion spectra were investigated as well. The results showed that: 1) Within the moisture content range of 10%-35%, there typically existed 2-4 proton signal peaks in T2 inversion spectra of tobacco materials, of which the T21 peak having the relaxation time of 0.01-10 ms reflected the relaxation signal intensity of hydrogen proton of moisture. 2)With the increase of moisture content in tobacco materials, the relaxation time of peaks T21 for cut strips, cut stems and cut reconstituted tobacco gradually increased from 0.183 to 1.430, from 0.166 to 1.560 and from 0.166 to 1.650 ms, respectively. It reflected that the augmentation of the proportion of active migration moisture. 3) A significant linear correlation existed between the T21 relaxation peak area and the moisture content in tobacco material, it suggested that the T2 inversion signal could be used in the quantitative analysis of moisture content in tobacco materials. 4)Once the pores larger than 30 μm in natural tobacco material were damaged, the relaxation time of moisture reduced significantly, it indicated that the occurrence state of moisture in natural tobacco material was obviously affected by its microporous structure.%为探讨不同烟草材料内部水分赋存状态,采用低场核磁LF-NMR手段分析了叶丝、梗丝、再造烟叶丝3种烟草材料的自旋-自旋弛豫时间T2反演谱,并分析了不同烟草材料含湿量、微观结构对T 2反演谱中水分子信号峰弛豫时间、弛豫峰面积的影响规律.结果表明:①在10%~35%含水率范围内烟草材料的T2反演谱图通常呈现2~4个质子信号峰,其中弛豫时间在0.01~10 ms范围T21峰可反映烟草中水分的氢质子弛豫信号强度.②随着烟草材料含水率的增大,叶丝、梗丝、再造烟叶丝的T21峰弛豫时间在0.183~1.430、0.166~1.560、0.166~1.650 ms范围内逐渐增大,烟草材料中迁移性较强的水分比例增大.③T21弛豫峰面积与不同烟草材料含水率均存在显著的线性相关,该T2反演信号可用于烟草材料含水率的定量分析.④天然烟草材料中30μm以上细胞尺度上的孔隙被破坏后,水分弛豫时间明显减小,表明天然烟草材料中水分赋存状态受其微观多孔结构影响明显.
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