Volume 20 (2002): Edizione 4 (December 2002)

Since the beginning of 2003, BeiträgezurTabakforschung International/Contributions to Tobacco Research is available on the Internet at www.beitraege-bti.de.

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We think the website of Beiträge is an improvement of the service for all present readers and might also help to enlarge the readership of the Journal in the future. We all know that nothing is perfect and everything (particularly new things) can be improved. The Editorial Office of Beiträge would be grateful for any suggestions regarding improvement of the website.

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The mainstream smoke filtration performance of activated carbon, silica gel and polymeric aromatic resins for gas-phase components was evaluated using a puff-by-puff multiplex gas chromatography-mass spectrometry (GC-MS) analysis method (1). The sample 1R4F Kentucky reference cigarettes were modified by placing the adsorbents in a plug/space/plug filter configuration. Due to differences in surface area and structural characteristics, the adsorbent materials studied showed different levels of filtration activities for the twenty-six constituents monitored. Activated carbon had significant adsorption activity for all the gas-phase smoke constituents observed except ethane and carbon dioxide, while silica gel had significant activities for polar components such as aldehydes, acrolein, ketones, and diacetyl. XAD-16 polyaromatic resins showed varied levels of activity for aromatic compounds, cyclic dienes and ketones.

A modern infrared camera was used to observe the peripheral burning of cigarettes during puffing and smouldering. The computer-controlled infrared system captured thermal images with recording rates up to 50 Hz at 8-bit (256-colour) resolution. The response time was less than 0.04 s at ca. 780 °C. The overall performance of the system was superior to most infrared systems used in previously reported investigations. The combined capacity allowed us to capture some faster, smaller high-temperature burning events on the periphery of a cigarette during puffing, which was first described by Egertion et al. in 1963 using an X-ray method. These transient burning events were caused by tobacco shreds near the coal surface experiencing the maximum air influx. The temperature of these transient burning events could be ca. 200 to 250 °C higher than the average peripheral temperature of the cigarette. The likelihood of these high-temperature burning events occurring during smouldering was significantly less. Some other details of the cigarette's combustion were also observed with improved simplicity and clarity.

A mathematical model for a smoldering cigarette has been proposed. In the analysis of the cigarette combustion and pyrolysis processes, a receding burning front is defined, which has a constant temperature (~450 °C) and divides the cigarette into two zones, the burning zone and the pyrolysis zone. The char combustion processes in the burning zone and the pyrolysis of virgin tobacco and evaporation of water in the pyrolysis zone are included in the model. The hot gases flow from the burning zone, are assumed to go out as sidestream smoke during smoldering. The internal heat transport is characterized by effective thermal conductivities in each zone. Thermal conduction of cigarette paper and convective and radiative heat transfer at the outer surface were also considered. The governing partial differential equations were solved using an integral method. Model predictions of smoldering speed as well as temperature and density profiles in the pyrolysis zone for different kinds of cigarettes were found to agree with the experimental data. The model also predicts the coal length and the maximum coal temperatures during smoldering conditions. The model provides a relatively fast and efficient way to simulate the cigarette burning processes. It offers a practical tool for exploring important parameters for cigarette smoldering processes, such as tobacco components, properties of cigarette paper, and heat generation in the burning zone and its dependence on the mass burn rate.

Materials generated by combustion and pyrolysis in a lit cigarette move through the tobacco rod and filter sections in two phases, the particulate phase and the gas phase. Some particles are removed while moving through the rod and filter sections. The gas-phase materials include the vapor of many volatile compounds. While moving through the rod and filter sections, part of the vapor are removed by adsorption and condensation.

In this study, a puff-by-puff delivery model for cigarettes is developed to calculate “tar”, water, and nicotine in smoke on a puff-by-puff basis. A number of parameters can be obtained by the best fit to the experimental results of some cigarettes with different filter lengths. The parameters include the materials generated at the coal for each puff, the particle and vapor removal constants for tobacco rods and filters. The parameters may be useful in understanding some characteristics of cigarette smoke.

Examination of extensive laboratory data collected during the past four decades, particularly those unpublished data generated in the 1950s and 1960s, indicates that none of the materials used as casing materials (sugars, licorice, cocoa) and humectants (glycerol, propylene glycol, other glycols) on smoking tobacco products, particularly cigarettes, imparts any significant adverse chemical or biological properties to the mainstream smoke (MSS) from cased and humectant-treated tobacco, a conclusion reached by Doull et al. (1) in their assessment of available information on nearly 600 flavorant, casing material, and humectant ingredients variously used as cigarette tobacco additives in the U.S. Tobacco Industry. Addition of casing materials and humectants to the cigarette tobacco blend produced no significant increase in the cigarette MSS of either the total polycyclic aromatic hydrocarbon (PAH) or the benzo[a]pyrene (B[a]P) content, MSS components that have been of considerable interest for many years. Examination of the transfer of humectants from the humectant-treated tobacco to cigarette MSS indicates that the humectants act as significant diluents to the remaining MSS particulate-phase components generated from the tobacco during the smoking process. This dilution decreases the effects observed in several bioassays, e.g., mutagenicity determined in the Ames Salmonella typhimurium test.

The results of our experiments executed to obtain tobacco male sterile lines through interspecific hybridization are summarized. Ten wild species from the genus Nicotiana: N. excelsior (exc), N. amplexicaulis (amp), N. rustica (rus), Nicotianaglauca (gla), N. velutina (vel), N. benthamiana (ben), N. maritima (mar), N. paniculata (pan), N. longiflora (lon) and N. africana (afr) were used as cytoplasmic donors and N. tabacum, cv. HarmanliiskaBasma (HB) as a donor of the nucleus. Genetic effects of cytoplasmic-nuclear interaction of the studied species are discussed. Our results suggested that cytoplasmic male sterility (CMS) was expressed when the cytoplasms of the above mentioned wild Nicotiana species were combined with the nucleus of N. tabacum. The 10 sources of CMS obtained in tobacco were characterized by altered flower phenotypes. Flowers are classified into types according the stamen, pistil and corolla modification. All these CMS sources were backcrossed to Oriental tobaccos, cvs. Tekne, Nevrokop B-12, Kroumovgrad 90 and Djebel 576, to develop corresponding CMS lines. The investigated cytoplasms produced compete male sterility in all those cultivars. The CMS lines preserved flower types, specific for every “sterile” cytoplasm. The extent of male organ modifications varied from apparently normal (but pollenless) stamens in CMS (pan), (afr), some plants of (vel) (mar) through different degrees of malformations (shriveled anther on shortened filaments (lon), pinnate-like anthers on filaments of normal length (amp), petal - (ben), pistil- or stigma-like structures (rus), (gla)) to lack of male reproductive organs in (exc) and in some plants of (vel), (mar), (rus) and (gla). Most of the above mentioned cytoplasms had normal female gametophyte and good seed productivity. Alterations of the pistils were observed in CMS (rus), (exc) and (ben) causing reduction of the seed set. Electrophoresis of seed proteins of the tobacco cultivars and their CMS lines also suggested that the nuclei of wild species was entirely displaced by the nucleus of N. tabacum. CMS lines with cytoplasms of N. velutina, N. maritima, N. paniculata, N. longiflora and N. amplexicaulis were selected as suitable for seed production in tobacco.