BAT Science - Novel tobacco processing

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Novel tobacco processing

10103_tobaccoblend_30
Tobacco blend prior to novel processing

As part of our continuing investigation into tobacco harm reduction ( developing tobacco products that reduce a smokers exposure to smoke toxicants), we have developed a novel tobacco-modification process[1].

This process has been developed to remove proteins and polyphenols from tobacco without affecting its physical structure.  Proteins are targeted because they are thought to be precursors of many of the nitrogen containing tobacco smoke toxins such as hydrogen cyanide and the mutagenic aromatic amines, while the tobacco polyphenols are believed to be precursors for phenolic smoke toxicants.  Because the integrity of the tobacco’s physical structure is maintained during the process, this modified tobacco can be used in conventional manufacturing processes to produce reduced toxicant prototype cigarettes.

The first step of the process involves extracting conventional (Virginia) tobacco shreds with water.  This produces an aqueous tobacco extract and tobacco fibre, which are separated by centrifugation.  The liquid containing the water-soluble tobacco components is treated with adsorbents (bentonite to remove soluble proteins, and polyvinylpolypyrollidone to remove polyphenols) and concentrated for later return to the tobacco fibre.  The spin-dried tobacco fibre is treated with a proteolytic enzyme solution to fragment and solubilise the water-insoluble proteins.  After spin-drying, the fibre is autoclaved to inactivate any remaining enzyme. 

Compared with a control blend, a treated flue-cured blend was found to have reduced levels (w/w) of protein nitrogen (59%), chlorogenic acid (33%), rutin (79%), scopoletin (78%) and caffeic acid (53%).  Nicotine levels were found to be reduced by 12%, whereas as a consequence of the process, sugar levels increased by 16%.

9mg ISO tar yield cigarettes were made with a single segment cellulose acetate filter and were analysed under Health Canada Intense smoking conditions. Compared with control cigarettes made with the untreated tobacco, cigarettes with treated tobacco gave lower yields of tar (16%), nicotine (17%) and carbon monoxide (20%).  Of the 43 toxicants analysed there were significantly lower yields of ammonia (40%), 1-aminonaphthalene (45%), 2-aminonaphthalene (48%), 3-aminobiphenyl (45%), 4-aminobiphenyl (49%), hydrogen cyanide (51%), the tobacco specific nitrosamines (NNN, 26%; NAT, 25%; NAB, 32%; NNK, 27%), phenol (52%), o-cresol (25%), m-cresol (23%), p-cresol (46%), catechol (24%), resorcinol (56%), hydroquinone (36%), pyridine (36%), quinoline (35%), benzene (16%), toluene (25%), acrylonitrile (33%) and cadmium (34%). There were significantly increased yields of formaldehyde (49%) and isoprene (17%).

A comparison of tobacco constituents for treated and untreated tobacco can be found in table 1 below[1].

Group

Analytes

Untreated tobacco (SD)

Treated tobacco (SD)

 (%) Difference

Aromatic Amines

1-Aminonaphthalene (ng/cig)

10.9 (0.9)

5.95 (0.51) -45.5 
2-Aminonaphthalene (ng/cig) 7.19 (0.59) 3.73 (0.27) -48.1 
3-Aminobiphenyl (ng/cig) 1.7 (0.12) 0.93 (0.11) -45.3 
4-Aminobiphenyl (ng/cig) 1.35 (0.07) 0.69 (0.04) -48.9 

Carbonyls

Methyl ethyl ketone (μg/cig) 67.7 (4.56) 65.3 (4.09) -3.6 
Acetaldehyde (μg/cig) 535 (35.5) 514 (20.7) -3.9 
Acetone (μg/cig) 276 (17.8) 257 (14.3) -6.9
Acrolein (μg/cig) 60.3 (3.54) 62.9 (1.76)  4.3
Butyraldehyde (μg/cig) 32.1 (1.89) 24.3 (1.2) -24.1 
Crotonaldehyde (μg/cig) 17.1 (1.3) 15.8 (0.61) -7.4
Formaldehyde (μg/cig) 31.2 (4.0) 46.3 (2.7) 48.6 
Propionaldehyde (μg/cig) 47 (2.82) 47.1 (2.04) 0.2 

Phenols

Catechol (μg/cig) 76.2 (1.63) 57.6 (3.76) -24.4 
Hydroquinone (μg/cig) 65.2 (1.75) 42.0 (2.8) -35.5 
m+p-Cresol (μg/cig) 10.69 (0.21) 6.55 (0.41) -61.2 
o-Cresol (μg/cig) 3.82 (0.1) 2.85 (0.18) -25.4 
Phenol (μg/cig) 16.2 (0.47) 7.78 (0.54) -51.9 
Resorcinol (μg/cig) 1.04 (0.04) 0.46 (0.02)

-55.8 

Polycyclic Aromatic Hydrocarbon (PAH)

Benzo[a]pyrene (ng/cig) 5.68 (0.3) 5.34 (0.25) -6.0 

Inorganics

Ammonia (μg/cig) 5.85 (0.27) 3.51 (0.27) -40.0 
Hydrogen Cyanide (μg/cig) 96.3 (5.84) 47.2 (1.58) -51.0 
Nitric Oxide (μg/cig) NM NM
Carbon Monoxide (mg/cig) 11.3 (0.28) 9 (0.22) -20.4 

Organics

Acrylonitrile (μg/cig) 7.73 (0.36) 5.17 (0.72) -33.1 

Volatile Hydrocarbons

1,3-Butadiene (μg/cig) 27.8 (1.92) 27.4 (1.8) -7.1 
Benzene (μg/cig) 38.6 (1.51) 32.6 (1.96) -15.7 
Isoprene (μg/cig) 148 (13.6) 173 (10.8) 16.9 
Toluene (μg/cig) 60.2 (7) 45.2 (4.54) -24.9 
Styrene (μg/cig) 9.73 (0.38) 7.82 (0.52) -19.6 

Nitrogen Heterocyclics

Pyridine (μg/cig) 5.25 (0.22) 3.34 (0.21) -36.4 
Quinoline (μg/cig) 0.32 (0.05) 0.208 (0.02) -35.0 
Nicotine (mg/cig) 0.93 0.77 -17.2 

Metals & Metalloids

Arsenic (ng/cig) 7.4 (1.4) 5.56 (1.58) -24.9 
Cadmium (ng/cig) 32.2 (3.27) 21.1 (1.38) -34.3 
Chromium (ng/cig) 2.02 (0.35) 2.37 (0.74) 17.3 
Lead (ng/cig) LOQ LOQ
Mercury (ng/cig) LOQ LOQ
Nickel (ng/cig) LOQ LOQ
Selenium (ng/cig) LOQ LOQ

Tobacco Specific Nitrosamines (TSNAs)

NAB (ng/cig) 1.5 (0.08) 1.02 (0.1) -32.0 
NAT (ng/cig) 21.4 (1.76) 16.0 (0.81) -25.2 
NNK (ng/cig) 8.27 (1.23) 6.06 (0.4) -26.7 
NNN (ng/cig) 8.34 (0.51) 6.2 (0.29) -25.7 

'Tar'

Nicotine-free-dry-particulate-matter (mg/cig) 9.5 (0.39) 8 (0.28) -15.8 

* SD = Standard deviation

Sidestream smoke yields were also measured. Tar, nicotine and CO were not significantly altered by the tobacco treatment process; in contrast, yields of the nitrogen containing smoke toxicants were significantly reduced for the treated tobacco cigarette. Sidestream yields of several carbonyls, benzo(a)pyrene and isoprene were increased.  

A full description of the process and its effects on tobacco chemistry and the chemistry of smoke from cigarettes made with this tobacco has now been published [1].  Work is ongoing to design cigarettes using this tobacco in combination with adsorbent filters to reduce the smoke concentrations of formaldehyde and isoprene that are increased by the process. The effects of smoke from these cigarettes on the results of short-term biological assays and on uptake of smoke constituents  during human smoking are currently being investigated.

Clinical studies

This year we hope to report the results of our first clinical study of prototype reduced toxicant products. This study involves testing prototype cigarettes modified to produce reduced levels of specific toxicants compared with conventional cigarettes. The aim is to determine whether smokers who switch to the prototype products have lower levels of markers of toxicant exposure in their biological fluids than the smokers who continue with their regular cigarettes. Non-smokers act as a control for the markers of toxicant exposure.

Study Title: “To compare the exposure levels of selected smoke constituents as determined by biomarkers of exposure, filter analysis, sensory perception and other parameters when smokers using commercial cigarettes are switched to novel cigarettes”.

 Study registration: (http://www.controlled-trials.com/ISRCTN72157335).


  1. Chuan Liu, Yves DeGrandpré, Andrew Porter, Alexander Griffiths, Kevin McAdam, Richard Voisine, France Côté and Christopher Proctor  (2011) The use of a novel tobacco treatment process to reduce the yields of toxicants in cigarette smoke. Food and Chemical Toxicology, In Press - online ahead of print. Abstract: The use of a novel tobacco treatment process... Opens new window
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