Application of Low-Field NMR Technology in Moisture Analysis of Cut Tobacco

Moisture in tobacco materials is a key indicator closely monitored in the tobacco industry. It plays a critical role in cigarette processing, storage and transport, as well as sensory evaluation. Moisture is one of the most important parameters reflecting the physical properties of tobacco, strongly influencing characteristics such as filling capacity, processability, density, elasticity, and combustion behaviour of cigarettes. It also serves as the main basis for process control and adjustment during thermal and moisture treatments such as conditioning and drying. Therefore, studying the state of water in tobacco is essential to understanding these processing phenomena and the changes in tobacco’s physical properties.

Low-field nuclear magnetic resonance (LF-NMR), as a real-time, non-destructive, and non-invasive quantitative measurement technique, can reveal multiple parameters from a microscopic perspective, including the moisture content of agricultural products. LF-NMR can be applied to investigate moisture content, water distribution, water activity, ripeness, and moisture diffusion during drying. By analysing the spin–spin relaxation time T₂ of hydrogen protons in water molecules, LF-NMR reflects differences in the degree of binding between water and materials through physical or chemical interactions. This makes NMR an effective tool for predicting moisture content and assessing water activity in agricultural and related materials.

LF-NMR can be used to study water distribution and binding states in shredded tobacco, stems, and reconstituted tobacco leaves under different moisture conditions.

T₂ inversion spectra of shredded tobacco before and after drying, and with 20% petroleum ether extract added

[Reference: Analysis of moisture distribution in different tobacco materials using low-field nuclear magnetic resonance. Tobacco Science & Technology, 2017, 04(v.50;No.360):71–77+108.]