Volume 14 (1987): Issue 1 (December 1987)

Two systems of genetic control are involved in the quality and level of total alkaloids in tobacco (Nicotianatabacum L.). A single locus controls the conversion of nicotine to nornicotine and two loci control total alkaloid levels. These levels may be further modified by minor genes or quantitative factors. Breeding lines and cultivars of flue-cured tobacco have been developed with varying levels of total alkaloids (nicotine). Levels of nicotine in tobacco range from near zero in cigar strains up to 4.5 % in Burley varieties. Within the collection of N. tabacumgermplasm and Nicotiana species maintained by the Agricultural Research Service of the U.S. Department of Agriculture, total alkaloid levels range from 0.20 % to 7.87 %. Flue-cured lines of tobacco with varying levels of total alkaloids have been developed and characterized. In general the high alkaloid lines had the highest grade indexes. All of the extremely low alkaloid lines were also lower in grade index indicating that total alkaloids do have some relationship with the grade index. The high total alkaloid lines were lower in yield. However, it is believed that the levels of total alkaloids reported do not result from yield variation. N. rustica generally has considerably higher total alkaloid levels, based on percent dry weight, than N. tabacum. With the stabilizing of a low total alkaloid line of N. tabacum (0.20 %) it was feasible to introgress the gene(s) for alkaloid production from N. rustica into N. tabacum. Indications are that more than one gene is responsible for total alkaloid production in this material. Also preliminary indications are that the genes for total alkaloid production in N. rustica may be the same as those in N. tabacum.

A quantitative model describing the effects of puffing conditions on the level of filter ventilation was developed and evaluated. The development of the model was based on a quadratic flow-pressure drop relationship which was validated with experimental measurements for numerous plug wraps, tipping papers, and combinations of the two. This relationship was used to derive an equation describing the level of filter ventilation as a function of the flow rate of air exiting the filter. This equation was shown to accurately predict the measured ventilations of six brands of commercial cigarettes over a range of continuous flow rates. The instantaneous ventilation values predicted by the equation were utilized to model ventilation during a puff by integrating the equation with respect to flow rate over the duration of the puff. This method for predicting the effects of specific puffing conditions on ventilation was demonstrated for sinusoidally shaped puffs spanning a wide range of volume and duration. Finally, the effects on the flow dependence of ventilation of different combinations of plug wrap and tipping papers were described qualitatively based on experimental measurements of paper flow-pressure drop linearity.

Neutron radiography was used to study the density of tobacco rods. Density variations in individual rods caused by local packing variations and the presence of more dense materials in the blend were easily discernible in both static and real-time radiographs. A density resolution of 0.35 mm was observed in the real-time system. By averaging center line density scans for several rods with the aid of an image processor, large scale variations in the density such as the increased packing at the rod ends could be measured. Comparison of the results from neutron radiography with those obtained by cutting rods into sections and weighing the sections showed good agreement. Both methods indicated the lighting end was approximately 9 % more dense than the middle of the rod. This work has demonstrated that neutron radiography can be used to provide accurate density information about cigarette rods with considerably greater resolution and in much less time than sectioning and the commercial beta ray gauging technique.

Tobacco-specific N-nitrosamines [TSNA] and tobacco alkaloids were determined in green mature tobacco leaves, sun-dried leaves and processed tobacco from the species N. rustica and N. tabacum cultivated in two different locations. Analyses showed the presence of TSNA in green mature tobacco leaves and the levels of TSNA increased further upon sun-drying and processing. N. rustica showed relatively higher amounts of nornicotine as well as of N’-nitrosonornicotine [NNN]. A clear correlation between the amount of nicotine and nornicotine and the use of fertilizers was not found.

Eight genetically diverse tobacco types (Tsebelia of Agrinion, Samsun, Basma, Kabakulak, Burley, Virginia and Havana, belonging to Nicotianatabacum, and Brasilia belonging to N. rustica) were grown in pots in the greenhouse where lead acetate had been added to the soil at the rates of 0, 0.1, 1.0 and 10.0 g Pb/kg soil. In the field, 20 g Pb/m² in two forms (nitrate and acetate) were applied to Burley and Kabakulak types. The greenhouse experiment showed that only the highest rate of lead addition to the soil reduced the leaf yield significantly. The higher yielding types (Havana and Samsun) were found to be the least tolerant, while Brasilia was the most tolerant. At all levels of lead addition to the soil the lead concentration in leaf was found to be highest in the first of the three harvests which were made. The relationship between log (lead level in the soil) and log (leaf lead concentration) seemed exponential. Although control treatments in the field and the greenhouse experiment showed comparable leaf lead concentrations, leaf lead concentrations at 20 g Pb/m² in the field experiment were found to be higher than those at 1.0 g/kg soil in the greenhouse experiment.

Methoprene, a synthetic juvenile hormone analogue, was shown to have the capability of preventing the cigarette beetle Lasiodermaserricorne (F.) from propagating when applied to the outside of packaged Oriental tobacco bales. Control was achieved for a 33-month’ storage period when methoprene was applied at 40 mg/m² and 80 mg/m² to either the burlap sheathing or to the outer surface of the tobacco following removal of the burlap sheath.

Commercially available cigarette smoking machines are designed to operate at a standard set of smoking parameters and offer little scope for changing the smoking pattern. This paper describes a Programmable Smoking Machine (PSM) which operates in a way that no current commercial machine can. It can smoke cigarettes in a non-standard manner and obtain information useful for the examination of the influence of smoke generation patterns on the smoke yields as an aid to the design of cigarettes. The PSM consists of a stepper motor driven glass syringe and three-way valve controlled by microcomputer. Suitable programs create the desired smoking patterns and control the operation of the smoking machine via a microcomputer port. Precautions must be taken to prevent stepper motor pulses affecting the puff profiles. Smoking can be performed in a restricted or open mode with calibrated clearing puffs, and the vapour phase collected is directed on a puff-by-puff basis to a gas analyser or trapping medium at a controlled rate. It is also possible to generate whole smoke should this be a requirement.

Cigarettes with closely matched physical characteristics were subjected to static burns inside a modified bell-jar apparatus in order to investigate the effects of variations in cigarette construction and composition on the odor of sidestream smoke. Cambridge filter pads moistened with mineral oil and suspended inside the bell-jars were highly effective transfer materials which captured the sidestream smoke odors. Triangle-test odor evaluations of the exposed Cambridge pads established significant differences at the 95 % confidence level between sidestream odors from cigarettes made with 100 % Burley, flue-cured, or Oriental tabacco. Differences were also found between sidestream odors from tobacco grades within a single tobacco type and between equal blends of two tobacco types. Consistent with studies of sidestream menthol delivery and menthol levels needed to detect a just noticeable difference, no significant sidestream odor differences were found between menthol and non-menthol versions of the same cigarette.