Volumen 21 (2004): Edición 1 (March 2004)

Based on the unique temperature and oxygen profiles in a burning cigarette, a novel approach is proposed in this paper to use a single oxidant/catalyst in the cigarette filler for simultaneous removal of carbon monoxide (CO) and nitric oxide (NO) in mainstream smoke. A nanoparticle iron oxide is identified as a very active material for this application due to its multiple functions as a CO catalyst, as a CO oxidant, and in its reduced forms as a NO catalyst. The multiple functions of the nanoparticle iron oxide are characterized in a flow tube reactor and the working mechanisms of these multiple functions for CO and NO removal in a burning cigarette are explained. The effect of smoke condensate on the catalyst are examined and discussed. The advantage of in situ generation of the catalyst during the cigarette burning process is illustrated. The test results of nanoparticle iron oxide for CO and NO removal in cigarettes are presented.

Protein transfer in tobacco smoke has been studied using the protease, Savinase™, as a model protein. Mainstream and sidestream smoke were collected from cigarettes to which Savinase had been added at various concentrations. Savinase was extracted from the smoke condensate with an organic solvent system before being precipitated and further identified by denaturing polyacrylamide gel electrophoresis (SDS-PAGE) and Western immunoblotting. The detection limit of the method, based on addition of Savinase to the smoke condensate, was 25 µg in mainstream and 100 µg in sidestream smoke. At a Savinase concentration of 6000 µg per gram of tobacco, the methodology allows the detection of protein transfer as low as 0.009% and 0.054% in mainstream and sidestream smoke, respectively. Using this approach, it was shown that there is no detectable Savinase in the mainstream and sidestream smoke of filtered and unfiltered cigarettes containing up to 6000 µg of Savinase per gram of tobacco. These facts strongly suggest that there is no significant transfer of protein from tobacco into cigarette smoke.

The moisture content of cigarettes has a significant impact on the shelf life and the taste of the products as well as various physical properties of cigarettes including loose ends, burning rate, hardness, and pressure drop. To prepare better products it would be helpful to develop proper mathematical models for the simulation of moisture diffusion characteristic dynamics in a cigarette. In this work, four mathematical models have been developed with appropriate assumptions adequate to analyze the dynamics of moisture diffusion in cigarettes. The simulation of the derived models was also carried out in this work. When the theoretical values produced from each model were compared with the corresponding experimental data, it was found that three models (I-II, II, III) can be used to explain the behavior of moisture in cigarettes. Convective mass transfer coefficients and effective moisture diffusivities that fit best were obtained by a regression analysis of the model using the experimental values. The simulation of the models revealed that there is no significant positional dependence of moisture content inside a tobacco column because most of the moisture dries out radially through the cigarette wrapper. The drying rate of moisture in a tobacco column is rarely affected by effective moisture diffusivity, but strongly influenced by convective mass transfer. To prevent quality deterioration of the cigarettes during long-term storage, it is concluded that improvement of the cigarette wrapper and air tightness of the package, which are directly related to the convective mass transfer, is very important.

The goal of this study is to investigate whether the permeability of the tipping/plugwrap system, the permeability of the cigarette paper and the draw resistances of the filter and tobacco rod can be calculated from measurements of the degree of filter ventilation and of the open and closed draw resistance. This issue is investigated for a linear and a non-linear model of the flow in unlit cigarettes. At first it is proven that there exist experimental conditions to which the cigarette can be exposed such that the problem has at least a unique solution. The problem is then solved by least-squares optimisation for a linear and a non-linear model of the air flow in unlit cigarettes with various noise levels on the output quantities. The error sensitivity of the optimisation problem is estimated by calculation of the condition number.

From the simulation several facts can be concluded. Firstly, for the linear model varying the flow velocity at the mouth end of the cigarette does not provide enough information to uniquely determine the properties of the cigarette's components. Secondly, estimates of these properties from the linear model have low standard deviations but a high bias, which makes the linear model useless for the estimation task. Thirdly, estimates from the non-linear model are more reliable if the pressure at the cigarette tip is varied instead of the flow velocity at the mouth end. Fourthly, the measurements of the degree of filter ventilation and of the open and closed draw resistance need to be at least 10 to 20 times more accurate than the desired accuracy of the estimate. Several methods to improve this situation are proposed.

Various techniques have been employed in the analysis of volatile organic compounds (VOCs). However, these techniques are insufficient for the precise analysis of tobacco smoke VOCs because of the complexity of the operating system, system instability, or poor sensitivity. To overcome these problems, a combined system of VOC preconcentrator, gas chromatograph, and olfactometer has been developed. The performance of this new system was evaluated in the analysis of VOCs in tobacco smoke and applied to the odor profiling of sidestream smoke (SSS) that has not been sufficiently investigated in the past.

A VOC sample in a gas-sampling bag was injected into a gas chromatograph through a preconcentrator, where it was concentrated, dehydrated, and cryo-focused. Separated VOCs were introduced into a mass spectrometer (for qualitative and quantitative analysis) and a sniffing port (for odor profiling) by a splitting device. In addition to the conventional Gas Chromatography-Olfactometry (GC-O) technique that was used for describing the odor quality of each compound, the odor intensity was estimated based on the dilution ratio of the sample, Aroma Direct Dilution Analysis (ADDA). Also, the contribution of each VOC to the overall SSS odor was estimated by sensory evaluation.

This system permitted adequate characterization of the VOCs. The reproducibility of quantification was also good enough with Coefficient of Variation (CV) values less than about 5% (n = 5). With the GC-O technique, we obtained an SSS odor profile composed of over 30 odorants. ADDA indicated that seven odorants were sufficient to characterize SSS odor. In addition, the omit-test revealed that three odor attributes, (‘metallic’, ‘potato-like’, and ‘popcorn-like’) were most important for the characterization of SSS odor.

Canadian tobacco was flue-cured using two different heating systems: direct-fired in which the exhaust gases were in contact with the tobacco and indirect in which only hot air, via a heat exchanger, contacted the tobacco. The concentrations of tobacco-specific nitrosamines (TSNAs) in tobacco cured by indirect heating did not increase during curing and were in the range 0.25-0.35 ppm. There were no changes in TSNA concentrations (range 0.13-0.3 ppm) in tobacco cured by direct firing during the first six days (0-144 h) of curing. However between 168 and 264 h, significant increases in TSNAs occurred (up to 1.91 ppm). TSNA concentrations in leaves at the bottom of the plant were significantly higher than in those found at higher plant position. There were no significant differences in TSNA concentrations in tobacco cured on different farms. The TSNA concentrations in tobacco cured by indirect heat were 87% ± 5% lower than in tobacco cured by direct heat. Subsequent processing of tobacco did not change the relative concentrations of TSNAs.