Volume 14 (1989): Issue 5 (October 1989)

Inherently porous cigarette paper consists of an interlocking network of cellulose fibres interspersed with chalk particles. Spaces in this matrix are of the order of 1 AAµm wide which is small compared to the paper thickness (usually 20 AAµm to 40 AAµm). However, when cigarette paper is perforated after the paper-making process, e.g. by an electrostatic or mechanical process, the perforation holes are relatively large, usually having mean diameters of the same order of magnitude as the paper thickness. The total flow of air through perforated cigarette paper thus consists of two components: viscous flow through the porous structure of the paper inherent from the paper-making process, and inertial flow through the perforation holes. Since the air flow / pressure relationships due to these two components of flow differ and since the two components are additive, the total flow through perforated paper may be expressed as: Q = Z A P + Z’ A Pn, where Q is the air flow (cm3 min-1), A is the area of paper (cm2) exposed to the flowing air, P is the pressure difference across the paper (kilopascal), Z is the base permeability of the paper due to viscous flow through the spaces inherent from the paper-making process (cm min-1 kPa-1 or Coresta unit), Z’ is the permeability of the paper due to inertial flow through the perforation holes (cm min-1 kPa-1/n) and n is a constant for a given set of perforation holes. This equation adequately describes gas flow through a variety of perforated cigarette and tipping papers. By using different gases, it is confirmed that Z depends on viscous forces and Z’ depends on inertial forces. By examining the flow of air through a large number of papers with perforation holes of different sizes, it is shown that Z’ is dependent on the total area of perforation holes, and that a jet-contraction effect occurs as the air travels through the paper. The parameter n is shown to have a value between 0.5 and 1.0, and this value is related to mean perforation-hole size. The permeability of cigarette paper is defined as the flow of air through the paper when the pressure across the paper is 1 kilopascal. Thus from the above equation the “total permeability” of perforated cigarette paper is equal to Z + Z'.

This paper presents an evaluation of a fractionation procedure for use with tobacco. Correlation coefficients calculated from the weights of the polymer fractions obtained and data obtained with classical wet-chemical methods show that these parameters have a low resolving power, which precludes any detailed distinction between tobaccos and tobacco-derived fractions. Pyrolysis mass spectrometry combined with multivariate analysis is presented as a promising approach for investigating the variability in the chemical composition of tobacco. Multivariate analysis performed on the pyrolysis mass-spectrometric fingerprints of all tobacco fractions indicates that the differences between the individual tobaccos are smaller than the differences induced by the fractionation procedure. Multivariate analysis of subfiles of the pyrolysis mass-spectrometric fingerprints of separate polymer fractions is an excellent method for classifying tobaccos. Leaf and stem material can easily be distinguished. A further differentiation is made between the flue-cured and Burley-type tobaccos. The strong clustering of tobacco samples after treatment with potassium hydroxide points to a uniform cell-wall skeleton. The greater variability in the ethanolized tobacco samples, and samples subjected to hot-water extraction or amylase digestion, is related to the cytosol characteristics. These fractions appear to reflect both the dissimilarities between the distinct tobacco types and phenotypic variations due to differences in cultural management. Pyrolysis mass spectrometry of the Klason lignin residues points to a large variety of chemical constituents unrelated to lignin. Pyrolysis gas-chromatography mass-spectrometric data on the Klason lignin residues of a Burley tobacco showed that the correlation made between the organic-nitrogen content and the protein content of this fraction might be misleading. As a consequence the maximum value for the lignin content of this tobacco is estimated incorrectly.

The distribution of six radiolabelled model flavourants in cigarette smoke has been described. The possibility of pyrolytic products occurring in the mainstream smoke has been thoroughly examined. Of the six flavourants used four showed no detectable decomposition. Anisaldehyde underwent some decomposition that was detectable in the mainstream smoke. Even so the major radiolabelled smoke product was unchanged anisaldehyde (91.4 %). Vanillin decomposition, although suspected, was only detected in the sidestream gases in these experiments.

Radiolabelled [18-¹⁴C]octatriacontane (C₃₈H₇₈) was used as a model compound to study the transfer of compounds from tobacco into smoke. Non-filter cigarettes were made from Kentucky reference 2R1 cigarette tobacco filler oversprayed with alkane and were smoked on a single-port total recovery smoking machine. Of the recovered activity nearly 60 % was found in the mainstream and sidestream particulate phases of smoke, 5 % in the gaseous phase and 35 % in the butt. Reverse-phase high-performance liquid radiochromatography and thin-layer radiochromatography were used effectively to analyse the cyclohexane extracts of the filler, mainstream and sidestream total particulate matter, and butt. No degradation of the alkane was observed prior to smoking. The radioactivity in the mainstream total particulate matter extracts consisted mostly of intact [¹⁴C]octatriacontane. Sidestream total particulate matter extracts contained both intact octatriacontane and breakdown products. The radioactivity in butt extracts consisted almost entirely of intact octatriacontane, indicating that excess radioactivity in the butt is due to filtration of the intact alkane by the filler rod. The transfer of octatriacontane into mainstream smoke without pyrolytic degradation parallels that of the tobacco alkane dotriacontane.

Quantitative X-ray microanalysis for nine elements has been carried out on frozen, fully hydrated fracture faces of upper and lower epidermis, palisade and spongy mesophyll cells in leaf tissue of Nicotianatabacum L. cv. Coker 319 taken from plants at five different stages of growth. Although concentrations of aluminium, silicon and chlorine generally fell below the minimum-detection limit, the values for sodium, magnesium, phosphorus, sulphur, potassium and calcium were consistently higher and showed differences among tissue types and stages of growth. The general trend was for elemental concentrations to increase up to the mature and ripe stages of growth and then to decrease as the leaf ages further. The sodium values were highest at the beginning and end of the five stages of growth, with higher amounts in the epidermal tissues. As the leaves age, the levels of magnesium fell in the photosynthetic tissues but increased in the epidermal tissues. Such changes could be correlated with higher concentrations of potassium at the early stages of growth and with much lower values at the late stages. The sulphur levels showed only small differences between tissue types at all stages of growth. The calcium levels increased with age and there were consistently higher concentrations in the photosynthetic tissues than in the two epidermal layers. The levels of phosphorus were low in all tissue types and decreased with age. There is an increasing positive correlation between phosphorus and magnesium and a decreasing positive correlation between phosphorus and potassium during growth and senescence.

Factors influencing solanesol concentration in Burley tobacco have been investigated. A fivefold difference in solanesol concentration was found among genetic lines and the growing season effected a tenfold difference of this nonaprenol for certain tobacco genotypes. Soil-moisture deficits enhanced solanesol concentration at least fourfold. Irrigation of the stressed tobacco decreased the solanesol level. Data for the 1984 and 1985 growing seasons substantiated this observation and showed that solanesol may be a good indicator of small soil-moisture deficits. In 1984 and 1985 the solanesol concentration increased dramatically after topping for the top stalk position and there were smaller increases for the bottom and middle stalk positions. Nitrogen fertilization had only a minimal influence on solanesol concentration. The data show that it is possible to control solanesol concentration through genetic selection and, more importantly, through production practices.

A microwave generator and a closed-circuit wind tunnel were used to measure the thermal diffusivity of tobacco (Nicotianatabacum L.) stems in vivo by the unsteady-state method. A simple mathematical model for heat flow, based on Fourier's heat-conduction equation and Newton's law of cooling, was used in this study. The microwave method was found to be relatively rapid as both heating and cooling of a cylindrical stem in an air stream could be completed in approximately 30 minutes for thermal-diffusivity determinations. Thermal-diffusivity value of the tobacco stems, containing 94 % moisture and a mean stem temperature of 30°C, was found to be (1.38 ± 0.06) × 10^-7 m² s^-1. The coefficient of variation for the measurements did not exceed 1.4 % as determined through the analysis of cooling curves for five different air-flow rates over the stems. This study showed that the microwave technique could be effectively used to determine both accurately and reliably the thermal diffusivity of tobacco stems in vivo.