Enzymatic treatment of washed and extracted tobacco to reduce smoke toxicant levels

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Enzymatic treatment of washed and extracted tobacco to reduce smoke toxicant levels
News release

01 April 2011

A novel process using an enzyme, a clay powder used in wine production and a food additive has been successfully used to reduce levels of certain toxicants in tobacco smoke.

The development of “safer” tobacco products is the Holy Grail of tobacco research. This is why scientists at British American Tobacco are trying to develop innovative technologies to reduce toxicant levels in smoke. This is an essential step in a research programme that seeks to reduce toxicant exposure in smokers and then determine whether this reduction has any impact on health risks related to smoking.

A number of the toxicants in tobacco smoke are generated by burning proteins and polyphenols found naturally in the tobacco leaf. Imperial Tobacco Canada, a subsidiary of British American Tobacco, developed a multi-step process that reduces the levels of some of these proteins and polyphenols. Scientists at British American Tobacco have scaled-up and optimised the process described in the journal Food and Chemical Toxicology.

The first step is an extraction of tobacco with water, which produces solids and a liquid extract that are then separated from each other. The solids are treated with a proteolytic enzyme which works by breaking down insoluble proteins into peptides. These are soluble in water and are easily removed. The same principle applies to brewing and food processing industries where protein is degraded to peptides and to biological washing detergents and dishwasher powders that remove protein-based stains like egg, gravy and grass.

The liquid extract contains soluble proteins and polyphenols and is treated separately. It is treated with Bentonite, which removes proteins. Bentonite is also used to remove the proteins that make wine cloudy. The filtrate is then passed through a filter containing cross-linked polyvinylpyrrolidone, a food additive often used as a stabiliser. In this case, it is used to remove polyphenols.

There is then a recombination step, during which the liquid extract and the solid extract are recombined and dried. To remove the active enzyme prior to recombination the solid extract is put through a rinsing procedure and a subsequent heat treatment prior to recombination. After drying, the processed tobacco is then suitable for use in cigarette manufacture. Smoking machine tests reveal that when prototype cigarettes containing the treated tobacco are burned there are substantial reductions in the levels of most aromatic amines, hydrogen cyanide and some tobacco specific nitrosamines.

Of 43 toxicants tested, there were reductions seen in 23. There were, however, increased levels of formaldehyde and isoprene.

Chris Proctor, Chief Scientific Officer at British American Tobacco, cautions, however, that: ‘Even if you can reduce the levels of a significant number of toxicants in tobacco smoke, there is no guarantee that this will result in reduced exposure in people or result in a reduction in health risks.’ This is why scientists at British American Tobacco are testing prototype cigarettes made using treated tobacco in clinical studies in Germany to determine whether reductions in toxicant levels seen in smoking machine tests translate to reduced exposure levels in smokers.



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