HK1154761B - Method for the treatment of tobacco, tobacco and smoking article - Google Patents

Description

Method of treating tobacco, tobacco and smoking article

Technical Field

The present invention relates to the treatment of tobacco and, in particular, to the extraction of selected components from tobacco, for example, in order to reduce specific smoke constituents.

Background

The tobacco material can be treated and processed to produce an improved mixture that, when combusted, produces smoke having specific smoke constituents selectively reduced or removed as compared to untreated tobacco. However, the sugar and nicotine content of tobacco preferably remains substantially unaffected by this process to maintain the mouthfeel and smoking performance of the tobacco.

Means for removing or at least reducing selected constituents from tobacco are known in the art. Such a process may include an extraction stage in which the tobacco material is extracted by an aqueous or organic solvent; a separation stage in which the extraction liquid is separated from the insoluble tobacco residue by filtration, concentration or the like; and a treatment stage in which the extract is treated to remove specific components. The treated tobacco extract is then recombined with the extracted tobacco to ensure that certain components of the tobacco are retained in the reconstituted tobacco material.

U.S. patent nos. 5,311,886 and 5,601,097 describe methods for removing proteins from tobacco, which methods comprise extracting tobacco material with an aqueous solvent consisting of a surfactant and optionally a proteolytic enzyme. The aqueous extract (including dissolved tobacco components) is separated from the insoluble tobacco residue and treated to remove any unwanted components, typically including surfactants and polypeptides. The treated tobacco extract is concentrated and recombined with the washed and dried tobacco residue, thus ensuring that certain components of the tobacco, such as hydrolyzed flavour components and nicotine, are retained in the final product.

U.S. patent No. 5,601,097 further describes sequential extraction of tobacco using a surfactant and proteolytic enzymes that reduce the protein in tobacco more than was observed in a single extraction.

European patent application No. 1623634 describes a fractionation method of a tobacco extract and discriminately treats the fractionated portions according to the contained components. The fractionated part including the desired component is recombined with the extracted tobacco, while the fractionated part including the undesired component is discarded or partially recombined with the extracted tobacco. The reconstituted tobacco material thus remains containing all the required components (such as nicotine) but substantially excludes the undesired components (e.g. nitrates and amines).

In the examples of European patent application No. 0517407, the tobacco extract is separated from insoluble tobacco residue and contacted with another tobacco extract obtained by extracting tobacco with an alkaline solution. The combination of extracts is then applied to extract tobacco to produce a reconstituted product.

In the process described in us patent 5,243,999, the tobacco extract is subjected to a temperature treatment to cause some components to crystallize or precipitate out of solution. The extraction fluid may alternatively or additionally be contacted with activated carbon particles to remove additional selected components therefrom. The extract is then processed to recombine with the extracted tobacco to produce a product containing lower levels of potassium nitrate and acetaldehyde.

European patent application No. 0535834 describes a method for extracting tobacco by removing any essentially insoluble components by filtration and centrifugation. The extracted tobacco is treated with a vehicle that releases gums from the tobacco material, processed into a predetermined shape and then the treated tobacco extract is applied thereto.

The prior art methods have successfully provided reconstituted tobacco with lower amounts of undesirable constituents than untreated tobacco. However, they are not without drawbacks.

Methods known in the art include extraction in a conventional batch reactor, followed by separation of the aqueous extract from the insoluble tobacco residue using conventional filtration, centrifugation or using one or more mixing channels through a screw extruder or the like. The productivity of such extraction and separation processes is obviously limited by the maximum production energy of the selected plant. Furthermore, as the size of the mixer in a batch reactor increases, it becomes difficult to maintain turbulent mixing at the vessel edges. The amount of extraction and the processing steps are therefore limited by the size of the container that can be effectively used in practice.

The efficiency of the separation process also depends on the particular filtration technique being performed. This means that while such an extraction process is effective, it will not be suitable for operation on an industrial scale.

Therefore, there is a need to maintain a high throughput process that can be used to efficiently separate tobacco extracts from insoluble tobacco residues and to efficiently extract undesirable constituents from tobacco.

The invention described herein overcomes the difficulties of the prior art by using a horizontal belt filter for the processing of tobacco. The process may be a continuous process with a very significant improvement in efficiency over batch processing techniques known in the art. The described process can thus be provided for industrial use, allowing tobacco processing processes to increase throughput beyond what has been achieved. The described process also does not require the use of a surfactant, which obviously avoids the need to remove the surfactant from the tobacco residue in a subsequent step of the treatment process.

In the process described herein, the extraction of tobacco and separation of the tobacco extract from the tobacco residue may be performed using a horizontal belt filter.

Horizontal belt filters are well known in industries unrelated to the tobacco industry, including the mining, mineral and metallurgical industries. In fact, these filters have been used for the dewatering of raw materials such as ore, iron ore, coal and lead-zinc concentrate, because of their flexibility in operation, adaptability to corrosive slurries and suitability for handling large production volumes.

Horizontal belt filters include an endless recirculation belt configured to allow filtrate to drain toward the holes in the belt. The belt may be made of rubber with transverse grooves for drainage, or it may be made of Polyetheretherketone (PEEK)^TM) A mesh woven loose enough to allow drainage. Other raw materials and drainage means are also possible. A raw slurry to be separated is fed onto a belt. The filtrate is discharged through holes in the belt by vacuum assistance during the transport of the slurry, but may alternatively be carried out under gravity alone, and finally discharged out of the dewatering mat.

Horizontal belt filters are efficient and reliable liquid/solid separation devices for heavy machinery. Recent technological improvements have led to the creation of large belts of high mechanical strength. Such belts, in conjunction with improvements in the mechanical techniques required to support the heavy belts during operation, can produce high throughput filters. Modern horizontal belt filters can reach belt speeds in excess of 50 meters per minute and can produce very short cycle times.

Since filtration using horizontal belt filters can also work with vacuum assistance, separating the liquid from the insoluble residue left on the belt is a very efficient process.

Furthermore, the sequence of operations in the filtering process is such that: the aqueous solvent is applied to the retentate towards the end of the filter, and the filtrate is collected and recycled by application to the feed at a point upstream of the belt. This means that the final wash filtrate, which is collected after the final counter-current washing stage, increases the concentration of soluble material compared to the filtrate collected by conventional filtration.

However, the suitability of horizontal belt filters for the tobacco industry is by no means obvious. These filters are designed to separate liquids from heavy or thick raw materials and, therefore, nothing indicates that they can be used for tobacco treatment.

However, the applicant has found that horizontal band filters are in fact suitable for the extraction of tobacco and perform surprisingly well in separating tobacco extracts from insoluble residues. Most notably, the amount of soluble tobacco components that ultimately appear in the aqueous extract is increased over that observed by simple batch extraction.

The use of a horizontal belt filter thus increases the effectiveness of the tobacco extraction and separation process and enables higher throughput.

Disclosure of Invention

Accordingly, in a first aspect of the invention, there is provided a process for the treatment of tobacco using a horizontal belt filter.

In one embodiment of the invention, the process comprises extracting tobacco using an aqueous or organic solvent and filtering the extracted product. Either or both of the extraction or filtration steps operate on a horizontal belt filter. The extracted tobacco may be continuously fed onto the horizontal belt filter and the extraction and filtering steps may be continued as the tobacco is transported along the filter. This filtrate can be recycled and utilized as the extraction solvent for the tobacco being fed to the horizontal belt filter. In a preferred embodiment, the filtrate to be recycled is from one or more downstream counter-current washing stages.

In another embodiment, the process of the invention additionally comprises treating the tobacco with an enzyme. In a preferred embodiment, the enzyme is a proteolytic enzyme.

The process additionally includes rinsing the enzyme treated tobacco with a saline solution. This step is essentially an extraction step, since the residual enzyme is extracted from the tobacco fibres. The salt rinse stage is preferably performed on a horizontal filter. The enzyme-treated tobacco may be washed twice with a salt solution, wherein both salt washing steps are performed on separate horizontal belt filters. In the preferred embodiment, the salt rinse is preferably continuous as the tobacco is transported along the filter, and the filtrate from the second salt rinse is preferably recycled and used as the salt solution of the tobacco first salt rinse that is passed onto the horizontal belt filter of the first salt rinse.

In another embodiment, the process further comprises inactivating enzymes in the tobacco. The inactivation may occur in steam treatment, heat treatment or chemical treatment of the tobacco. The inactivation is preferably carried out on tobacco on a horizontal belt filter.

Thus, in one embodiment, the process operates using multiple horizontal band filters and is a continuous process.

In another embodiment, the process comprises extracting tobacco using an aqueous or organic solvent, treating the tobacco with an enzyme, rinsing the enzyme-treated tobacco with a salt solution and inactivating the enzyme in the tobacco, wherein one or more of the steps is performed on a horizontal belt filter. In another embodiment, all of these steps are performed on a horizontal belt filter.

In a preferred embodiment, the tobacco extract from the extraction step is treated to remove proteins therefrom, preferably with bentonite. The tobacco extract may alternatively or additionally be treated to remove polyphenols therefrom, preferably by treatment with polyvinylpolypyrrolidone (PVPP).

The process of the present invention preferably additionally comprises the recombination of the extracted tobacco with the treated tobacco extract.

In a second aspect of the invention, there is provided a tobacco product obtainable by the process of the invention.

In a third aspect of the invention, there is provided a smoking article comprising tobacco obtainable by the process of the invention.

Drawings

Figure 1 shows the sequence of operations for tobacco extraction and recycling of the washing filtrate when transporting tobacco on a horizontal belt filter.

Figure 2 shows the sequence of operations for salt washing the extracted tobacco with a horizontal belt filter.

Figure 3 shows the sequence of operations for the second saline flush of extracted tobacco and the recirculation of the washing filtrate as the tobacco is transported on the horizontal belt filter.

FIG. 4 shows a sequence of operations for washing tobacco with clean water using a horizontal belt filter to remove salt and inactivate enzymes.

Figure 5 shows a tobacco treatment process in which tobacco extraction and subsequent washing is treated using a plurality of horizontal belt filters in series. The tobacco is then combined with the extracted and treated tobacco.

Detailed Description

In one embodiment of the invention, the tobacco material to be extracted is stemmed, cut, shredded or ground tobacco. In a preferred embodiment, the tobacco is shredded tobacco. However, other forms of tobacco may also be extracted using the methods described herein.

The tobacco material may be mixed with a solvent for extraction to form a slurry. The solvent may be added to the tobacco material in a specific gravity of between 10: 1 and 50: 1, preferably between 20: 1 and 40: 1 and most preferably between 25: 1 and 30: 1. In a particularly preferred embodiment, the solvent added to the tobacco material is a specific gravity of 27: 1.

The solvent may be an organic solvent, but is preferably an aqueous solvent or water. At the very beginning of the extraction process, the solvent is usually water, but may also contain an alcohol such as ethanol or methanol, or it may contain a surfactant. Other solvents may also be used, depending on the particular ingredients extracted from the tobacco.

The slurry may first be formed in a tobacco mixing tank before being pumped into a second tank, using for example a plug flow reactor or a continuously stirred tank reactor for extraction.

The extraction can be carried out at 15-85 deg.C, and preferably at 65 deg.C. The slurry is preferably continuously agitated during the extraction process so that the tobacco remains suspended. The extraction is preferably carried out between 15 minutes and two hours. In a preferred embodiment, the extraction is performed for about 20 minutes.

During the extraction process, soluble tobacco components are removed from the tobacco material and enter the solution. These ingredients include nicotine, sugar, some proteins, amino acids, gums, polyphenols and flavors. Up to about 55% of the first weight tobacco is dissolved.

It is important that the gum in the tobacco fibers remain cross-linked during the extraction and processing to maintain the fibrous structure of the tobacco. Thus, calcium may be added to the solvent used to extract the tobacco as well as any solution used in downstream processing.

After extraction, the slurry from the extraction cylinder enters the belt of a first horizontal belt filter. The filtrate is discharged through the holes in the belt during the transport of the slurry. These filtrates ("mother filtrates") were collected.

At the same time, the insoluble tobacco residue remaining on the belt of the horizontal belt filter can be counter-currently washed during transport for further extraction, so that as much of the soluble components as possible are removed from the tobacco.

The sequence of operations of tobacco extraction as it travels along the horizontal belt filter is such that: fresh solvent may be applied to the tobacco towards the end of the filter and this filtrate ("wash filtrate") is collected.

The washing filtrate can be recycled by being applied at an upstream point on the tobacco residue entering on the belt. The collection of the washing filtrate and the further application of the washing filtrate upstream of the incoming tobacco residue may be repeated several times, preferably three times, four times or even five times. Thus, in the wash filtrate that is eventually collected at the head of the belt, the soluble tobacco components that are removed as they travel the length of the filter are concentrated.

The protocol for the sequence of operations for extracting tobacco and recycling the wash filtrate as it travels along the horizontal belt filter is shown in figure 1.

The final wash filtrate can be further recycled by adding it to fresh tobacco to form a tobacco slurry ready for extraction. For example, the final wash filtrate can be added to a tobacco mixing vat, wherein the tobacco slurry is formed prior to the extraction process.

The extraction process can thus be a continuous process in which fresh tobacco is extracted using recycled wash filtrate. The tobacco is extracted with fresh solvent only at the beginning of the extraction process. Once the extraction process has started, no fresh solvent is used anymore in the extraction, but this solvent is constituted only by the recycled washing filtrate.

As the extraction process continues, the extraction solution thereby becomes an increasingly concentrated soluble tobacco component. These include those entering solution in the primary extraction stage (forming the mother filtrate) which is carried out in an extraction cylinder, and those entering solution in the secondary extraction stage (forming the wash filtrate) which is carried out on a horizontal belt filter.

The final filtrate thus comprises the mother filtrate and the washing filtrate. In this way, the tobacco residue formed after filtration is completely free of components that are dissolved in the solvent used in the extraction process.

The extracted tobacco may be pressed at the end of the filtration to remove any excess liquid. The extracted tobacco therefore exits the horizontal belt filter, usually in the form of a dewatering mat.

The final filtrate, referred to hereinafter as tobacco extract, may be subsequently treated to remove those components that are not desired in the final tobacco product. Undesirable components include proteins, polypeptides, amino acids, polyphenols, nitrates, amines, nitrous acid and colored mixtures. However, the levels of desirable ingredients such as sugar and nicotine should remain unaffected so that the flavor and smoking properties of the extracted tobacco are comparable to those of the original raw materials.

In a preferred embodiment, the tobacco extract is treated to remove proteins, polypeptides and/or amino acids. Up to 60% of the protein contained in the raw tobacco material is removed using an insoluble adsorbent such as hydroxyapatite or a fuller's earth mineral such as attapulgite or bentonite.

The tobacco extract is preferably treated with bentonite to remove polypeptides therefrom. Bentonite may be added to the extract in an amount of 2-4% by weight of the tobacco from which it was originally extracted. Alternatively, the tobacco extract may be delivered into a vat containing a slurry of bentonite. One suitable slurry includes about 7kg bentonite (per hour) in about 64kg water, for example, 64.18kg bentonite (per hour) in 7.13kg water. In any case, the bentonite concentration should be high enough to reduce the proteins contained in the tobacco extract sufficiently, but not so high as to moreover absorb nicotine therefrom.

The bentonite treatment is also effective in removing colored compounds from the tobacco, which compounds have a tendency to darken the extract after concentration if not removed. When the extract is treated with a large amount of bentonite, the reduction in the amount of the coloring mixture allows the product to be made without excessively darkening in appearance.

After bentonite treatment, the tobacco extract may be purified from the slurry by centrifugation and/or filtration.

The tobacco extract may also, or alternatively, be treated to remove polyphenols therefrom. Polyvinylpolypyrrolidone (PVPP) is an insoluble adsorbent for polyphenols, which is commonly used in the brewing industry to remove polyphenols from beer. PVPP may be added to the extract in an amount of 5-10% by weight of the tobacco originally extracted. This amount of PVPP can remove 50% to 90% of the polyphenols in the solution.

The optimum pH for removing polyphenols from tobacco extracts with PVPP is about 3. The efficiency of absorption by PVPP can thus be increased by lowering the pH of the extract by adding a suitable acid, such as hydrochloric acid.

As an alternative to using PVPP to absorb polyphenols, one or more enzymes may be added to the tobacco extract to degrade polyphenols therefrom. A suitable enzyme is laccase (urushiol oxidase).

However, the present invention is not limited to methods for removing proteins and/or polyphenols from tobacco alone. Alternatively or additionally, enzymes, vehicles, or adsorbents may be used to remove undesired components from other tobacco components from the tobacco extract. Additional examples of undesirable tobacco constituents that may be removed from the extract include nitrates, amines, and nitrosamines.

If multiple components are to be removed from the tobacco extract, multiple cylinders may be assembled in series, each including a different enzyme, vehicle or sorbent, to remove selected portions of the undesired components. Alternatively, a single vat may contain multiple enzymes, vehicles or adsorbents so that the unwanted components are removed in a single step. For example, a bentonite or PVPP reservoir may include one or more additional enzymes, vehicles, or adsorbents to remove not only proteins or phenols from tobacco, but also one or more undesirable constituents.

After treating the tobacco extract to remove selected undesirable constituents, the extract is preferably concentrated to a solids concentration of between about 20 to 50% by weight. Concentration of up to 10% of the solids is most effectively achieved by using reverse osmosis. Another concentration to about 40% solids can be obtained by falling film evaporators. Other methods of concentration may be used and are well known to those skilled in the art.

The concentrated tobacco extract can then be recombined with the extracted tobacco.

However, the tobacco that has been extracted in an aqueous solution as described above is preferably further extracted to remove one or more other undesirable constituents prior to recombination with the concentrated tobacco extract.

Further extraction of tobacco may use specially selected enzymes to remove selected components.

In a preferred embodiment, the enzyme is a proteolytic enzyme that removes proteins from tobacco. The enzyme is preferably a bacterial or fungal enzyme, more preferably a commercial enzyme in the food and detergent industries. The enzyme can be derived from protease (Savinase)^TMNeutral protease (Neutrase)^TM，(Enzobake)^TMAnd alkaline protease (Alcalase)^TMSelected from the group consisting of all of which are available from Nove Inc. (Nove Inc.).

The proteolytic enzyme is preferably added to the tobacco in an amount of between 0.1 and 5% by weight of the tobacco material. For example, proteases^TMAdded to tobacco in an amount of about 1% by weight.

The tobacco may be reslurried in a solution of the selected enzyme. The ratio of water to tobacco in the slurry should be between 10: 1 and 50: 1, preferably between 20: 1 and 40: 1, and most preferably between 25: 1 and 30: 1. In a particularly preferred embodiment, the solvent added to the tobacco material is a specific gravity of 27: 1 by weight.

The pH of the tobacco/enzyme mixture should be such that it reaches an optimum activity value. Thus, the tobacco dewatering mat from the first horizontal belt filter is fed into a vat in which the pH is adjusted, for example by adding an alkali such as sodium hydroxide. The pH adjusted tobacco can then be transported to an enzyme metering tank to be mixed with the selected enzyme. The tobacco/enzyme mixture may then be transported to a plug flow reactor where enzyme extraction is performed.

The enzyme extraction should be carried out at a temperature that promotes the enzyme to reach an optimal activity value. Preferably, it is carried out at a narrow temperature range, e.g., 30-40 ℃, to prevent enzyme denaturation.

When the protease is^TMThe optimum working conditions were chosen to be 57 ℃ and pH 9-11.

The enzyme extraction should be performed for at least 45 minutes; any continuous time shorter than this is considered insufficient for proteolytic enzymes to degrade tobacco proteins.

Of course, if there are multiple components to be removed from the tobacco, multiple enzyme extractions are possible. This may be done in a series of treatments or multiple enzymes may be added to the tobacco in a single treatment step.

It is also possible to add the enzyme just during the first extraction step of the process, instead of forming a subsequent separate extraction step.

After enzyme extraction, the tobacco/enzyme mixture may be transported to a second horizontal belt mixer and the mother filtrate collected and disposed of as waste. The insoluble tobacco residue may be washed with a salt solution, preferably sodium chloride solution, to rinse off the enzymes. The salt wash may be performed in a sequential counter-current manner, similar to the tobacco extraction applied on the first horizontal belt filter.

The salt solution can thus be applied to the last tobacco filtered. This washing filtrate can be recycled and used to wash the tobacco residue travelling on the belt at an upstream point. The collection and upstream reuse of the washing filtrate for the input tobacco residue may be treated several times, preferably three times, four times or even five times. The final wash filtrate collected at the head of the belt was disposed of as waste. As shown in fig. 2.

The salt-washed tobacco may be pressed at the end of the belt to remove excess liquid therefrom.

The tobacco is then conveyed to a salt flush mixing tank and plug flow reactor or a continuously stirred tank reactor for recombination with the salt solution in the second salt flush.

The mixture may be conveyed to a third horizontal belt filter and the mother filtrate collected. This filtrate is disposed of as waste and is not recycled. Fresh saline solution, preferably sodium chloride solution, may be applied to the tobacco towards the end of the filter. As before, this washing filtrate can be recycled and used to wash the tobacco residue travelling on the belt at an upstream point. The collection of the washing filtrate and the upstream reapplication of the washing filtrate to the incoming tobacco residue may be repeated several times, preferably three times, four times or even five times. The wash filtrate finally collected at the head of the belt is recycled and used for the first salt rinse. As shown in fig. 3.

The salt-washed tobacco is pressed at the end of the belt to remove excess moisture therefrom. It is then preferable to combine with a fresh batch of saline to ensure near complete removal of the enzyme from the tobacco. A mixing cylinder and plug flow reactor or a continuously stirred tank reactor may be used for this purpose.

To remove the salt from the salt-washed tobacco, a clean water wash may be performed. The salt-washed tobacco can be transported to a fourth horizontal belt filter belt and the mother filtrate collected and recycled for the first or second salt wash. Clean water may then be applied to the tobacco towards the end of the filter. This washing filtrate can be recycled and used to wash the tobacco residue travelling on the belt at an upstream point. The collection of the washing filtrate and the upstream reapplication of the washing filtrate to the incoming tobacco residue may be repeated several times, preferably three times, four times or even five times. The wash filtrate eventually collected at the head of the strip was returned to each brine flush storage. As shown in fig. 4.

However, saline and water washing may not remove all of the enzymes from the tobacco. It is important that the final tobacco product is completely free of enzymatic activity to avoid the risk to the process operator of any adverse reactions associated with the enzymes in the final product.

The washed tobacco can thus be treated in subsequent saline and water rinses to inactivate any residual enzymes remaining in the tobacco. This can be done by steaming the tobacco to inactivate the enzymes sufficiently, but not so much as to prevent the tobacco from losing its fibrous structure. In one embodiment, the steam treatment is carried out at 98 ℃ for four minutes, but the retention time can be increased to around 10 minutes if desired. Alternatively, the tobacco may be heat treated to inactivate the enzymes, for example using microwaves or cured tobacco. In another embodiment, the enzyme is inactivated during chemical denaturation; however, a step of removing chemicals from the tobacco is required.

If the tobacco is steamed, this may be done while the tobacco is near the end of the fourth horizontal belt filter, as shown in FIG. 4. Excess liquid may be removed from the tobacco by pressing.

Thus, the process may include a series of separation steps, one or more of which may be performed using a horizontal band filter. In one embodiment, all of the steps are performed using a single horizontal band filter. The process may thus be a continuous process in which fresh tobacco is continuously fed onto the first horizontal belt filter and treated tobacco is continuously produced downstream. In one embodiment, the tobacco extraction, salt washing and enzyme inactivation steps are performed separately on each horizontal belt filter and multiple filters may be provided in series for this purpose. As shown in fig. 5.

The treated tobacco may then be further treated to render it suitable for recombination with a tobacco extract. In a preferred embodiment, the tobacco is transported to a shredder that breaks the matted tobacco into free-flowing fibers.

The treated tobacco may then be recombined with the concentrated tobacco extract. The treated extract is added back to the extracted tobacco to ensure retention of water soluble flavor components and nicotine of the tobacco in the final product. The recombination thus produces a tobacco product that contains a physical structure and shape, taste and smoking properties similar to the original material, but with greatly reduced levels of protein, polyphenol and other selected ingredients.

Recombination can be achieved by spraying tobacco extract onto the tobacco. The amount of the original extract recombined with the treated tobacco depends on the total flow loss of the treatment process in which the extract is treated to remove selected constituents and varies from one type of tobacco to another.

Standard drying procedures can be used to dry the tobacco, either before, during or after recombination with the treated tobacco extract. The initial moisture content of the tobacco is generally about 70-80%. In a preferred embodiment, the humidity after drying should be about 14%.

Thermal dryers, such as curtain dryers, may be used to reduce the moisture content of the tobacco to about 30%. A second thermal dryer, such as an air dryer, may then be used to further reduce the moisture content to about 14%.

The final dried product may then be processed to a final form, such as flakes, which may be shredded to form all or part of a cigarette filler.

However, since nearly 30% of the original tobacco components are removed from the tobacco during extraction and processing, the concentration of retained components per unit weight of tobacco in the final product is increased over the original raw material. These ingredients include cellulose, which together with sugars and starches can produce harmful volatile substances in the smoke upon combustion, such as acetaldehyde and formaldehyde.

To compensate for this problem, a particular type of filter may be incorporated into smoking articles containing treated tobacco. U.S. patent No. 4,033,361 describes a suitable filter comprising a macroporous amine-type anion exchange resin containing only a significant number of primary amine groups as an adsorbent for volatile tobacco smoke constituents. The filter may also contain carbon.

Claims (23)

1.A method of treating tobacco comprising extracting tobacco with an aqueous or organic solvent and filtering the extract, wherein both the extracting and filtering steps are performed on a horizontal belt filter.

2.A method according to claim 1, wherein the tobacco to be extracted is continuously fed onto a horizontal belt filter and the extraction and filtration steps are performed continuously as the tobacco is transported along the filter.

3.A process according to claim 2, wherein the filtrate is recycled and used as a solvent in the extraction of tobacco delivered to the horizontal belt filter.

4.The method of any one of claims 1-3, further comprising treating the tobacco with an enzyme.

5.A process according to claim 4, wherein the enzyme is a proteolytic enzyme.

6.The method of claim 4, further comprising rinsing the enzyme-treated tobacco with a saline solution.

7.The method of claim 6 wherein the salt rinse step is performed on a horizontal belt filter.

8.A process according to claim 6, wherein the enzyme-treated tobacco is washed twice with the salt solution.

9.The method of claim 8 wherein the two salt rinse steps are performed on separate horizontal belt filters.

10.A method according to claim 7 or claim 9, wherein the salt rinsing is carried out continuously as the tobacco is transported along the filter.

11.The method of claim 10, wherein the filtrate from the second salt rinse is recycled and used as the salt solution for the first salt rinse of tobacco transported to the first salt rinse horizontal belt filter.

12.The method of claim 4, further comprising inactivating the smokeEnzymes in grass.

13.The method of claim 12, wherein the inactivation is performed by steam treatment, heat treatment, or chemical treatment of the tobacco.

14.The method of claim 13, wherein the inactivation is performed on tobacco on a horizontal belt filter.

15.The process of claim 1 wherein a plurality of horizontal band filters in series are used.

16.The method of claim 1, further comprising:

(a) treating tobacco with an enzyme;

(b) rinsing the enzyme-treated tobacco with a saline solution; and

(c) inactivating enzymes in the tobacco;

wherein one or more of steps (a) through (c) are performed on a horizontal belt filter.

17.The method of claim 1, further comprising treating a tobacco extract obtained from the extraction of tobacco to remove proteins therefrom.

18.The method of claim 17, wherein the tobacco extract is treated with bentonite.

19.The method of claim 1, further comprising treating the tobacco extract obtained from tobacco extraction to remove polyphenols therefrom.

20.According to claim19, wherein the tobacco extract is treated with polyvinylpolypyrrolidone (PVPP).

21.The method of any one of claims 17-20, further comprising recombining the extracted tobacco with the treated tobacco extract.

22.Tobacco obtainable by a process according to any one of claims 1 to 21.

23.A smoking article comprising the tobacco of claim 22。