Moisture sorption thermodynamic and kinetic analyses of commercial tobacco filaments and in-situ prediction

The fine control over the moisture content of tobacco filaments is critical for the manufacture of cigarettes in the tobacco industry, which is one of the most important factors affecting tobacco quality. In this work, the hygroscopic properties of four types of tobacco filaments were investigated on a multi-sample dynamic sorption and desorption apparatus under the conditions mimicking the production environment, and moreover, their surface and cross-sectional morphologies were examined using scanning electron microscopy. Results show that four tobacco filaments differ significantly in the surface and pore structures. The rate of hygroscopicity increases with the relative humidity. The rate of moisture absorption is primarily governed by diffusion within the pore structure of the tobacco; the greater the humidity, the more pronounced the effect. Moreover, the moisture adsorption process of tobacco is an exothermic process based on isothermal results, fitted using different models, among which GAB and Oswin models were found to be two of the most suitable for fitting the adsorption results with GAB having the slightly better goodness-of-fit. Our findings provide a thermodynamic and kinetic basis for optimizing the tobacco processing technology. Specifically, the equilibrium moisture content of tobacco can be predicted using the Oswin model, which is closely dependent on the pore structure of tobacco filaments.