Volume 19 (2001): Issue 6 (July 2001)

A propagation model of cigarette static burn at the cigarette periphery is proposed. Propagation of cigarette static burn is characterized by intermittent burn of the cigarette paper. The burning rate depends on the period of flash burn of the paper and is independent of the burning width. By measuring the local temperature near the front line of the burning propagation, the rate-determining step was identified as the time required to ignite the paper. A mathematical analysis was performed by calculating the heat transfer at the periphery during the paper heating period, and it was revealed that the thermal properties of the cigarette are the dominant factors of cigarette static burn. Modeling results showed good agreement with measured data.

The thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) results presented in this report clearly show that the thermal stability and the endothermic peak nicotine release temperatures are different for different nicotine salts and these temperatures appear to be linked to the general microstructural details of the salt itself. In addition, the peak nicotine release temperatures are highly dependent upon the sample size used. The heat of vaporization for neat (non-protonated) nicotine is also sample-size dependent. The TGA data showed that the least stable of the salts tested at elevated temperatures was the liquid salt nicotine triacetate followed by the crystalline materials (e.g., nicotine gallate) and finally, the amorphous salts (e.g., nicotine alginate). The DSC results revealed that the liquid and crystalline salts exhibit nicotine release endotherms that are strongly related to the sample weight being tested. The amorphous salts show nicotine endotherm peak temperatures that are nearly independent of the sample weight. The range of peak nicotine release temperatures varied depending upon the specific salts and the sample size from 83 oC to well over 200 oC. Based on these results, the evolution of nicotine from the nicotine salt should be expected to vary based on the composition of the salt, the details of its microstructure, and the amount of nicotine salt tested.

Recent studies demonstrated a relationship between mass burn rates of straight-grade cigarettes and heats of combustion of the tobacco materials. In the present work, relationships between measured heats of combustion and elemental composition of the tobacco materials were further analyzed. Heats of combustion measured in oxygen were directly correlated with the carbon and hydrogen content of the tobacco materials tested. Ash content of the materials was inversely related to the heats of combustion. The water insoluble residues from exhaustively extracted tobacco materials showed higher heats of combustion and higher carbon content than the non-extracted materials, confirming a direct relationship between carbon content and heat of combustion. A value for the heat of formation of tobacco was estimated (1175 cal/g) from the heat of combustion data and elemental analysis results. The estimated value for heat of formation of tobacco appears to be constant regardless of the material type. Heat values measured in air were uniformly lower than the combustion heats in oxygen, suggesting formation of CO and other reaction products. Gases produced during bomb calorimetry experiments with five tobacco materials were analyzed for CO and CO₂ content. When the materials were burned in oxygen, no CO was found in the gases produced. Measured heats of combustion matched estimates based on CO₂ found in the gas and conversion of the sample hydrogen content to water. Materials burned in air produced CO₂ (56% to 77% of the sample carbon content) and appreciable amounts of CO (7% to 16% of the sample carbon content). Unburned residue containing carbon and hydrogen was found in the air combustion experiments. Estimated heat values based on amounts of CO and CO₂ found in the gas and water formed from the hydrogen lost during combustion in air were higher than the measured values. These observations indicate formation of products containing hydrogen when the materials were burned in air. CO and CO₂ formation during combustion in air were related to the composition of the tobacco materials. Materials with high carbon and low ash content showed evidence of higher CO₂ formation. Amounts of unburned residue also varied with material composition. Thus, energy released during tobacco combustion in air is related to material-dependent formation of reaction products in addition to the carbon oxides and to the quantity of unburned material.

Cytoplasms of several Nicotiana species - N. amplexicaulis, N. bigelovii, N. debneyi, N. eastii, N. exigua, N. glauca, N. glutinosa, N. goodspeedii, N. knightiana, N. occidentalis, N. plumbaginifolia, N. raimondii, N. suaveolens, N. undulata - were bred into the N. tabacum genomic background of flue cured tobacco cv. Zamojska 4. The collection includes also a cytoplasmic male sterile (cms) analogue of cv. Zamojska 4 with mutated cytoplasm of N. tabacum. Some of the alloplasmics were originally obtained in this laboratory (N. amplexicaulis, N. eastii, N. exigua, N. glauca, N. knightiana, N. raimondii). The remaining ones were acquired from other laboratories and backcrossed into Zamojska 4. All alien cytoplasms except that of N. knightiana produced full male sterility in Zamojska 4. The extent of male organ modifications varied from complete absence of stamens (N. suaveolens, N. tabacum) to petaloid and stigmatoid structures (most common effect) to malformed stamens (N. amplexicaulis, N. glauca) to apparently normal stamens (N. raimondii, N. knightiana). The majority of the alloplasmics showed response to tentoxin that was compatible with the cytoplasm donor. The exceptions were those involving N. exigua, N. raimondii, (N. raimondii I), and the cytoplasmic mutant of N. tabacum. There was some variation in growth and morphology among the alloplasmic variants of Zamojska 4. Under field infestation alloplasmics with the cytoplasm of N. plumbaginifoliaand N. eastiishowed symptoms of blue mold whereas the remaining alloplasmics and cv. Zamojska 4 were highly tolerant of that disease.

The purpose of this study was to investigate the changes in higher fatty acids and related biochemical characteristics of flue-cured tobacco during the process of aging. The concentration of total lipids in flue-cured tobacco decreased gradually during natural aging, but the concentration of individual principal higher fatty acids in flue-cured tobacco changed much differently during aging. Myristic acid (C₁₄:0) increased constantly during the whole aging process. Stearic acid (C₁₈:0) and oleic acid (C₁₈:1) increased at the initial stages of aging and reached maximum contents after one year of aging, but decreased thereafter. Palmitic acid (C16:0), linoleic acid (C₁₈:2), and linolenic acid (C₁₈:3) decreased constantly throughout aging, especially the linolenic acid content which decreased drastically. Furthermore, the ratio of unsaturated fatty acids (C18:1; C₁₈:2; C₁₈:3) and saturated fatty acids (C₁₄:0; C₁₆:0; C₁₈:0) decreased continuously during aging, from 1.00 at the initial stage to 0.43 at the end of aging, when it seemed to be stabilized. The maximum rate of decrease of the ratio was between 12 to 18 mo during aging. The activity of lipoxygenase (LOX) and peroxidation value (POV) initially increased and reached their highest levels after 6 mo of aging, but steadily decreased thereafter. The acid value (AV) and malondialdehyde (MDA) content increased during the first 12 mo of aging, then decreased rapidly after 12 and 18 mo, respectively.