Volume 22 (2006): Issue 2 (July 2006)

Whether ammonia-forming ingredients added to tobacco and ammonia in smoke affect the ability of the Cambridge filter pad to trap nicotine in the Federal Trade Commission (FTC) method was examined. Three commercial cigarettes, two industry reference cigarettes, and four specially designed test cigarettes were used in this study to represent cigarettes with different construction and mainstream (MS) smoke yield characteristics. One of the commercial cigarettes, a US 1998 Marlboro Lights¯ King Size cigarette, was used as a control cigarette for the four experimental test cigarettes. The test cigarettes differed from the control cigarette as follows: first, a reduction in ammonia-forming ingredients added to the reconstituted tobaccos; second, no ammonia-forming ingredients added to the reconstituted tobacco; third, no ingredients at all added to the reconstituted tobaccos; and fourth, no ingredients at all added to the entire tobacco blend. An XAD-4 tube was placed downstream of the standard Cambridge filter pad in the FTC method to trap the gas-vapor phase nicotine for subsequent analysis. The Cambridge filter pad used in the FTC method was determined to provide greater than 99% trapping efficiency for MS smoke nicotine from cigarettes with widely different soluble ammonia levels in filler and MS smoke ammonia yields.

In some parts of the USA and in Canada smouldering cigarettes are required to extinguish if placed on a certain number of layers of filter paper. This is usually achieved by the use of bands on the cigarette paper, which reduce oxygen diffusion into the cigarette. From a smoker's perspective, however, it is desirable that a cigarette does not extinguish if left to smoulder, for example, in an ash tray. To facilitate the design of papers for such cigarettes the influence of various cigarette parameters on self-extinguishment is investigated by numerical simulation of a one-dimensional cigarette model, which describes the main thermodynamic behaviour of smouldering cigarettes. The tobacco density, the tobacco heat capacity, the width of the bands on the cigarette paper and the heat released during combustion are chosen as parameters whose influence on the required oxygen diffusion constant of the bands on the cigarette paper is investigated. As these parameters are subject to a certain variation, it is assumed that the parameters are independently normally distributed. Based on this assumption the probability that a cigarette with given mean parameter values will extinguish, is calculated numerically.

The results show that the admissible range of diffusion constants for the bands on the cigarette paper is in general quite small and it is reduced even further if statistical variations of the cigarette parameters are considered.

The results provide guidelines for the appropriate choice of the diffusion constant of the bands on the cigarette paper such that the cigarettes comply with legal requirements and do not extinguish during normal smoking.

The low-temperature catalytic oxidation of CO has been reviewed, targeting its possible application to cigarette smoke. The treatment of CO in smoke by using a filter-packed catalyst is extremely complicated by the presence of a variety of chemically active gaseous compounds, a particulate phase, the high velocity of pulsing smoke flow, and ambient temperature. The relevant mechanisms of catalysis and the catalyst preparation variables that could help to overcome these problems are considered. Possible contributors to the overall kinetics that must include variety of diffusion processes were briefly discussed. The chemisorption of O₂, CO and CO₂ on Pd, Pt and Au and on partially reducible supports, surface reactions and oscillations of the CO oxidation rate were analyzed. The effects of the surface structure and electronic properties of the catalyst support, preparation conditions and presence of a second transition metal on the projected CO oxidation activity of the catalysts in smoke are also discussed. The reviewed catalyst preparation approaches can solve the low-temperature catalyst activity problem. However, more work is required to stabilize this activity of an air-exposed catalyst to provide a necessary shelf life for a cigarette. The greatest challenge seems to be a particular phase - exclusive selectivity that would not contradict with the necessary fast diffusion of gases through the catalyst pores.

A total of 51 doubled haploid (DH) derivatives of the flue-cured true-breeding tobacco variety Wislica were obtained via anther culture and colchicine-induced chromosome doubling. Of that number eight DH lines showed morphological aberrations and/or reduced vigour that made them unfit to be grown in the field. The remaining 43 DH lines were grown in 2001 under regular flue-cured tobacco management and evaluated for principal growth indicators, yield, curability and gross money returns from unit area. In 2002, the evaluation was scaled down to include 13 best performing DH lines of 2001. The DH lines showed a considerable variation for basic growth parameters. Usually, the DH lines had more leaves but were shorter than the parental genotype mostly due to shorter internodes. The majority of DH lines showed delayed flowering compared to the parental cultivar. Yields of cured leaves varied extensively, some of the DH lines yielding above and some below cv. Wislica. Curability measured as percentage of light (1st to 3rd) grades was generally lower in DH lines compared to that in cv. Wislica. However, because of the high leaf yield some of the DH lines were not inferior to the parental cultivar with respect to money returns from unit area.

An expressed sequence tags (EST) resource for tobacco plants (Nicotianatabacum) was established using high-throughput sequencing of randomly selected clones from one cDNA library representing a range of plant organs (leaf, stem, root and root base). Over 5000 ESTs were generated from the 3’ ends of 8000 clones, analyzed by BLAST searches and categorized functionally. All annotated ESTs were classified into 18 functional categories, unique transcripts involved in energy were the largest group accounting for 831 (32.32%) of the annotated ESTs. After excluding 2450 non-significant tentative unique transcripts (TUTs), 100 unique sequences (1.67% of total TUTs) were identified from the N. tabacum database. In the array result two genes strongly related to the tobacco mosaic virus (TMV) were obtained, one basic form of pathogenesis-related protein 1 precursor (TBT012G08) and ubiquitin (TBT087G01). Both of them were found in the variety Hongda, some other important genes were classified into two groups, one of these implicated in plant development like those genes related to a photosynthetic process (chlorophyll a-b binding protein, photosystem I, ferredoxin I and III, ATP synthase) and a further group including genes related to plant stress response (ubiquitin, ubiquitin-like protein SMT3, glycine-rich RNA binding protein, histones and methallothionein). The interesting finding in this study is that two of these genes have never been reported before in N. tabacum (ubiquitin-like protein SMT3 and methallothionein). The array results were confirmed using quantitative PCR.

Three field experiments were conducted at the experimental station of the Tobacco Institute Zagreb in Pitomaca during the years 1990 and 1992, 1993-1996 and 1999-2000 to determine the effects of irrigation at different soil moisture levels [40-100%, 60-100%, 80-100% of plant available water, (PAW)], of different starting times of irrigation (vegetative phase, early flowering stage, continuously), and of irrigation combined with nitrogen nutrition (0, 20, 40, 60 kg/ha N) on the yields and quality of flue-cured tobacco. The first two experiments involved block methods, the third involved the split-plot method.

In the first experiment, irrigation led to an increase in yield (3-38%), in price/kg (15-69%) and in reducing sugar content (18-89%) and a reduction of nicotine content (20-39%) in the flue-cured leaves. Additional irrigation at the early flowering stage and constant maintenance of soil moisture at a higher level resulted in somewhat lower yields but better visually estimated tobacco quality and, as expected, had a marked influence on the contents of nicotine and reducing sugars.

In the second experiment, irrigated tobacco gave higher yields in two of the four trial years, which were significant in 1995 (13-21%), higher reducing sugar levels in 1994 (20-34%) and a marked reduction of nicotine content in cured leaves in all years (11-56%). Under conditions identical with or similar to those used in this research, irrigation may be started at the early flowering stage.

In the third experiment, in both years irrigated tobacco showed significantly higher yields, price/kg and reducing sugar levels and significantly lower nicotine content. Averaging the two years indicated increases of 17%, 12% and 26% and a decrease of 29%, respectively. Higher amounts of nitrogen fertilizer promoted yield (up to 32%) and nicotine content (up to 76%), while decreasing reducing sugar levels (by up to 52%). Also, the price/kg of tobacco fertilized with more than 20 kg/ha of nitrogen dropped by as much as 26%.