KR20020075808A - Tobacco treatment - Google Patents

Abstract

The present invention relates to a method of treating tobacco for reducing or eliminating nitrosamines. The method involves the use of a supercritical fluid extraction medium at elevated temperature and pressure to selectively remove nitrosamines as compared to nicotine removal. The nitrosamine content of all tobacco types can be reduced.

Description

TOBACCO TREATMENT}

Tobacco-specific nitrosamines include N'-nitrosonornicotine, 4- (methylnitrosamino) -1- (3-pyridyl) -1-butanone, N'-nitrosoanathabin and N'-nitrosoa Navasin is included.

Various methods are known for removing nitrosamines from tobacco. In US 5,803,081 and WO 98/58555, green leaf tobacco (ie, tobacco before curing) is subjected to microwave irradiation, convection heating or lyophilization to kill microorganisms believed to be the cause of nitrosamine production during the curing of tobacco. All. A disadvantage of this method is that it involves the need for a specific curing run for tobacco, where a curing run is performed after the initial stage tobacco harvest.

It is an object of the present invention to provide an improved method of reducing nitrosamines in tobacco.

It is a further object of the present invention to provide an improved selective reduction method of nitrosamines in tobacco.

The present invention relates to a method of treating tobacco for reducing or eliminating the content of nitrosamines, in particular the nitrosamines peculiar to tobacco.

Reference will now be made to the accompanying schematic diagrams by way of example in order that the present invention may be clearly understood and readily practiced, wherein:

1 shows an apparatus for performing a machining process according to the first aspect of the present invention;

2 shows an apparatus for carrying out a machining process according to an alternative aspect of the invention.

The device shown in FIG. 1 is a closed system comprising a first chamber 1 and a second chamber 2, wherein the first chamber and the second chamber 1, 2 are connected to the interconnecting pipe 3. Interconnected by The closure system further comprises a fluid transport means, ie a pump 4. The apparatus further comprises a storage tank 5 interconnected with the first chamber 1 via a duct 6. A valve 7 operable to close the tank 5 is located in the duct 6.

The present invention provides a method for treating tobacco in which tobacco is subjected to treatment with a supercritical fluid extraction medium to extract nitrosamines from the tobacco.

Preferably, nitrosamine is separated from the supercritical fluid extraction medium by adding the extraction medium to the nitrosamine removal process.

Suitably, the nitrosamine removal process may comprise a chemisorption step. Preferably, the chemisorption step may comprise the use of ion exchangers.

Alternatively, the nitrosamine removal process may comprise an adsorption step. Suitable adsorbents may be selected from one or more of the group consisting of glass beads, activated carbon, aluminum silicates and zeolites. Other suitable adsorbents known to those skilled in the art can also be used.

In a further alternative, the nitrosamine removal process may comprise treatment of the extraction medium with ultraviolet light (UV) resulting in the destruction of nitrosamine in the extraction medium.

Further alternatives include extracting nitrosamines from the extraction medium; By adding the extraction medium to nitrosamine specific enzyme destruction; Or removal of nitrosamines by chromatography or other separation methods known to those skilled in the art.

The nitrosamine removal process from the extraction medium may comprise one or more of the nitrosamine removal processes outlined above. In certain circumstances, at least the use of various removal processes (including multi-treatment together) will result in increased specificity of nitrosamine removal. For example, the nitrosamine removal process can be a multi-treatment comprising a chemisorption step with treatment with UV radiation or a treatment with UV radiation after chemisorption step. To remove the nitrosamines from the chemisorption medium, a washing step may be necessary prior to UV ray treatment, which is then applied to the wash. Water, acids, salt solutions or alcohols may suitably be used in the washing step.

Suitably, an extraction medium having some, but not all, nitrosamine removed may contact the tobacco, such that the extract (s) other than nitrosamine in the medium may be incorporated or reincorporated in the tobacco. Such extract (s) may include, for example, nicotine and / or flavoring agents.

Even more preferably, other supercritical fluids known to those skilled in the art may be suitable, but the supercritical fluid used is supercritical carbon dioxide.

Suitably, an acid, preferably an organic acid, may be added to the tobacco prior to treating the tobacco with a supercritical fluid. Alternatively, the acid may be incorporated with the supercritical fluid. In addition, if an ion exchanger or adsorbent material is present, the acid may be incorporated with the ion exchanger or adsorbent. Suitable acids may be organic acids or salt derivative (s) thereof selected from one or more of the group consisting of malonic acid, ascorbic acid, succinic acid, glutaric acid, adipic acid, malic acid, tartaric acid, mucin acid and citric acid. Preferably, the organic acid is potassium citrate, for example citric acid salt. Other suitable acids can be inorganic acids such as sulfuric acid and phosphoric acid. Suitably, when acid is applied to tobacco, the acid is in solution form. Such solutions can be applied by spraying. Advantageously, the application of acid to tobacco can take place in casing cylinders commonly used in the tobacco industry for applying casing to tobacco.

For example, other modifiers such as organic solvents or alcohols may alternatively or additionally be used.

Preferably, the extraction process of the tobacco into the supercritical fluid takes place at elevated pressure and elevated temperature. Suitably, if the supercritical fluid is carbon dioxide, a pressure in the range of 100 to 350 bar can be used, preferably a pressure of about 200 to 300 bar, more preferably about 240 to 260 bar. Preferably, the temperature used is higher than about 35 degrees Celsius, more preferably in the range of about 35 degrees Celsius to about 140 degrees Celsius, even more preferably from about 35 degrees Celsius to about 90 degrees Celsius.

Advantageously, during the extraction process into the supercritical fluid, the tobacco is placed in a closed chamber or bomb.

The heating can be carried out by heat transfer or electromagnetic radiation (ie microwave or high frequency heating). If electromagnetic radiation is used, of course, the closed chamber or bomb will have to be made of a non-electromagnetic wave absorbing material, ie a non-metallic material capable of withstanding operating pressure. Such suitable materials may for example be made of polyfluorohydrocarbon materials such as Teflon ™.

The technical effect of removing tobacco-specific nitrosamines by processing tobacco into supercritical fluids is unknown. Even more preferably, the conditions under which the extraction process of tobacco into the supercritical fluid takes place is biased by the extraction of nitrosamine into the supercritical fluid as compared to other tobacco specific compounds such as, for example, nicotine. Advantageously nicotine is not removed at all or very slightly from the tobacco with the extraction medium. Conditions that encourage nitrosamine extraction (compared to nicotine extraction) include tobacco pH of less than about 6.5, preferably less than about 5.5.

Preferably, when tobacco is subjected to the processing of the present invention, the ratio of nitrosamine reduction percentage to nicotine reduction percentage in tobacco is from about 1.1: 1 to about 18: 1, more preferably from about 1.3: 1 to about 10: 1. And even more preferably in the range of about 2: 1 to about 6: 1.

For example, for a given set of processing conditions that includes the mass flow rate of the extraction medium per unit mass of tobacco, the percentage of (more) nitrosamine extraction and (less) after a certain time interval from the start of processing There will be a maximum difference between the percentage of nicotine extract. Accordingly, it may be desirable to stop the extraction process at this point.

Suitable mass flow rates of the supercritical fluid extraction medium per kilogram of tobacco range from about 1 kg / h to about 55 kg / h and depend on processing conditions such as tobacco packing density and chamber size in the chamber. While these numbers depend on the desired product characteristics, advantageously the mass flow rate of the supercritical fluid extraction medium per kg of tobacco is in the range of 10 to 40 kg / h, more advantageously in the range of 15 to 35 kg / h, Even more advantageously about 30 kg / h.

Advantageously, the tobacco treated according to the processing of the invention is chopped tobacco which is chopped lamina and / or chopped stem tobacco. Alternatively, or in addition, the tobacco may be one or more of whole leaf tobacco, tobacco dust and reconstituted tobacco.

If deemed appropriate, tobacco treated according to the inventive process may be subjected to a conditioning step such that after treatment the tobacco has a moisture content of less than about 15%, preferably less than 13%.

After treatment of the tobacco with the supercritical fluid, the nitrosamine is separated from the supercritical fluid extraction medium by adding the medium to a nitrosamine removal process, preferably by causing the medium to flow around the closed system.

Suitably, the closed system may comprise a first chamber for the treatment of tobacco with the supercritical fluid and a second chamber in which the nitrosamine removal process takes place, wherein the first chamber and the second chamber are interconnecting means, eg For example, interconnected by pipe (s). Such a system further includes a fluid transport means operable to cause the extraction medium to flow around the closed system. Nitrosamine removal materials such as ion-exchange resins or adsorbents may be present in the second chamber, such that the supercritical fluid extraction medium is transported through the interconnecting means to the second chamber where nitrosamine is completely or substantially removed after treatment of the tobacco. do. The supercritical fluid extraction medium from which nitrosamine has been removed may then return to the tobacco in the first chamber.

Suitably, a plurality of interconnected chambers may be provided for the treatment of tobacco with the supercritical fluid and / or a plurality of interconnected chambers may be provided for the nitrosamine removal process. In this case, if one or more chambers are provided for the treatment of tobacco, the nitrosamine removal process, or both, the supercritical fluid can flow continuously through the chamber.

Alternatively, the closure system may comprise a single chamber or a first chamber having an inlet and an outlet, wherein the interconnecting means interconnects the inlet of the chamber with the outlet. Suitably, the interconnecting means may be used to transport the supercritical fluid extraction medium from the outlet of the chamber to the nitrosamine removal process location and through the nitrosamine removal process location to the inlet of the chamber under the operation of the fluid transport means. Preferably, the amount of fluid in the interconnection means is kept to a minimum. Nitrosamine removal materials, such as ion exchangers or adsorbents, may be contained in suitable permeable containers to provide a means for fluid to pass through the container and a means for preventing tobacco from contacting the nitrosamine-removing material.

Alternatively, the nitrosamine removal process can consist of transporting the medium through, for example, a UV light source. In this case, the interconnecting means must transmit UV rays.

Suitably, a plurality of interconnected chambers may be provided for treatment of the tobacco with the supercritical fluid.

In addition to treating tobacco with supercritical fluid to extract nitrosamines from tobacco, tobacco can be subjected to microbial killing processes. As mentioned above, Enterobacter agglomerans , Bacillus spp , Fusarium equisetti , Cladosporium cladosporoide , Altenaria alternata ( Microorganisms , including Altenaria alternata ) and Acremonium arxii , are thought to contribute to or contribute to nitrosamine production during the curing of tobacco. Indeed, it is contemplated that microorganisms may also be a contributing factor in producing nitrosamines in tobacco during storage of cured tobacco. Thus, the reduction of microbial activity in tobacco by the microbial killing process reduces the likelihood of nitrosamine reformation in tobacco after extraction. The microbial killing process may be carried out before or after adding tobacco to the treatment with the supercritical fluid. A further alternative is to add tobacco to the supercritical fluid under microbial killing conditions such that microbial killing and extraction occurs simultaneously.

Suitably, the microbial killing process may include pasteurization wherein the tobacco is heated to a certain temperature and then maintained for a set time at that temperature. By way of example, the tobacco may be heated from about 30 seconds to about 2 minutes to a temperature in the range of about 70 degrees Celsius to about 150 degrees Celsius. The heating can be carried out, for example, by convection heating, microwave heating or high frequency heating by contacting the tobacco with a gas heating medium.

Suitably, the moisture content of the tobacco added to the sterilization process is adjustable in stages before and after conditioning.

Alternatively, for example, tobacco ionization, UV irradiation, freeze drying or treatment with an electron beam to kill microorganisms may be used as the microbial killing process.

In addition to treatment of tobacco with supercritical fluid to extract nitrosamines from tobacco, tobacco may also be subjected to a nitrite / nitrate removal process. Nitrite is an important precursor of nitrosamines, while nitrates are precursors of nitrites. It is believed that the nitrite remaining in the tobacco after nitrosamine removal can also react freely with the alkaloids present in the tobacco to reform nitrosamines. The nitrite / nitrate removal process may suitably include solvent extraction to remove nitrite / nitrate from tobacco, followed by an ion exchange step of binding nitrite / nitrate. Alternatively, nitrite can be removed by an oxidation step. In a further alternative, a method of removing nitrite / nitrate using microorganisms such as those described in GB 1 440 171, GB 1 585 024, US 4709,710 or GB 2 014 031 can be used.

In addition to the microbial killing process, the nitrite / nitrate removal process can be performed before, after or during the treatment of the tobacco with the supercritical fluid. If the nitrite / nitrate removal process is carried out concurrently with the treatment of the tobacco with the supercritical fluid, processing to remove the nitrite from the tobacco, for example, treats the tobacco with ascorbic acid before treating the tobacco with the supercritical fluid. Applying; Incorporating ascorbic acid with the supercritical fluid; Or in the presence of an ion exchanger or adsorbent material, incorporating ascorbic acid with the ion exchanger or adsorbent. Ascorbic acid has the effect of scavenging nitrite from tobacco.

The nitrite / nitrate removal process can be performed as an alternative to or in conjunction with the microbial killing process.

The processing of the present invention provides Burley tobacco with an initial nitrosamine content in the range of about 0.3 ppm to about 30 ppm after curing and at least 45% less nitrosamine content after processing. If the tobacco is Burley tobacco having a nitrosamine content of 5-6 ppm, the content after processing is preferably 3.6 ppm or less.

The processing of the present invention also provides Virginia tobacco having an initial moisture content of less than 8.5 ppm after curing and at least 45% less nitrosamine content after processing.

Preferably the Burley or Virginia processed tobacco has a nitrosamine content of at least 60% less than its original content.

The inventive treatment also has an original nicotine content in the range of 0.10-2.0% and nitrosamine content in the range of 0.10-1.2 μg / g, and after processing the nitrosamine reduction percentage to nicotine reduction percentage in the range of 1: 1 to 10: 1. It provides a US blended tobacco having.

The processing of the present invention also has an original nicotine content in the range of 0.30-2.15% and nitrosamine content in the range of 0.10-1.5 μg / g, and after processing the nitrosamine reduction percentage to nicotine reduction percentage in the range of 1: 1 to 10: 1. Provides Virginia blended tobacco with sentiment.

Preferably, the ratio is in the range of at least 5: 1, more preferably in the range of at least 8: 1.

Example 1

In the operation of the device of FIG. 1, about 30 kg (see Table 1) of cut tobacco having a water content of about 14% or 25% is placed in a first chamber 1 having a volume of 150 liters. An ion exchanger having a weight of 4.4 kg, i.e. an acidic ion exchange resin (obtained from Bayer GmbH), is placed in the second chamber 2 having a volume of 150 liters. The ion exchanger is mixed with about 500 g of solid potassium citrate granules. Filling the storage tank 5 with carbon dioxide, the carbon dioxide is then maintained at a constant air pressure by a pump (not shown) and interconnected with the first and second chambers 1, 2 from the storage tank 5 by the pump. (3) are transported until the required extraction conditions are achieved, i.e. a pressure of about 250 bar and a temperature of about 70 ° C At this point the carbon dioxide storage tank is closed with a closing valve 7. Supercritical carbon dioxide is then interconnected via the operation of the pump 4 via the first chamber 1 (and thus the tobacco contained therein) and the second chamber 2 (and thus the ion exchange resin therein). Circulation is carried out by the pipe 3. Supercritical carbon dioxide extraction media circulate around the closed system for 1.5 hours or 3 hours. The first chamber and the second chamber 1, 2 are then opened to depressurize and open the chamber.

The nicotine and nitrosamine content of the tobacco thus treated is then evaluated using appropriate standard laboratory tests.

This tobacco extraction process has been found to remove significant amounts of tobacco-specific nitrosamines from treated tobacco. Table 1 describes the reduction percentage of nicotine and nitrosamine in tobacco after treatment of the tobacco outlined above. The total amount of CO ₂ used for this example is 2190 kg.

Enforcement number Tobacco m.c. Extraction time (h) Nicotine Reduction (%) Nitrosamine Reduction (%) One 14% 1.5 67 90 2 14% 3.0 78.5 94 3 25% 1.5 65.5 93.5 4 25% 3.0 77 95

Treatment for 1.5 hours results in a greater difference between the percentage of nitrosamine extraction and the percentage of nicotine extraction compared to the treatment for 3 hours.

Example 2

It is contemplated that the extraction time outlined above does not substantially affect the percentage of nitrosamine reduction, while being further shortened while further reducing the percentage of nicotine reduction. For example, the extraction time may be about 15 minutes to about 1.5 hours, preferably about 20 minutes to about 1 hour, more preferably about 25 minutes to about 40 minutes, even more preferably about 30 minutes.

The extraction conditions are preferably further biased against the extraction of nitrosamines into the supercritical fluid, compared to other tobacco specific compounds such as nicotine. Various other methods of extraction biased with nitrosamine removal compared to other tobacco specific compounds can be used together or separately from the adjustment of extraction time. For example, the pH of tobacco can be maintained at less than about 6.5, preferably at about 5.5. According to a further alternative, the supercritical fluid extraction medium may be saturated or substantially saturated with tobacco specific compounds other than nitrosamine or similar chemicals on the market before the extraction medium contacts the tobacco. If the supercritical fluid is carbon dioxide, a further alternative is to cool the tobacco to a temperature below about 35 ° C., so that the general effectiveness of the extraction process when the supercritical carbon dioxide is pumped to the chamber containing the tobacco is to remove tobacco-specific compounds other than nitrosamines. On the contrary, it may be selectively biased to be reduced. Skew into nitrosamine extraction may also be effected by varying (ie, increasing) the packing density of the tobacco in the extraction chamber.

In addition, the bias may be effected by varying, i.e., reducing the mass flow rate of the supercritical fluid extraction medium per unit mass of tobacco. For example, the flow rate of supercritical fluid per kg tobacco is reduced to less than 30 kg / h. Compared to other tobacco specific compounds, the method of biasing the extraction to nitrosamine removal can be performed separately or in conjunction with each method outlined above.

Optionally, in addition to the process described above, the ion exchange resin located in the second chamber 2 after depressurization of the closed system is flushed or washed with water. The wash is then treated with UV rays from a UV light source (not shown). Exposure of the wash to UV radiation results in degradation of nitrosamines in the wash. The extract (s) other than nitrosamine in the wash is then reincorporated into tobacco. Other extract (s) may include, for example, nicotine and / or flavoring agents. In this way, the end result is that nitrosamine is selectively removed from the cigarette without adversely affecting the taste of the cigarette.

Some examples of the foregoing changes are described in Table 2 below.

In view of the variability of the nicotine and nitrosamine content in each batch of tobacco, 300 g from each batch is retained as a control for the batch. Nicotine and nitrosamine levels for each control from 4 batches sampled are shown in Table 3 below.

Trial / Trial Cigarette Type & Weight Nicotine% in Blend Nicotine Reduction% Total TSNA μg / g in blend TSNA Reduction Rate% Extraction time ₂ kg total CO Other process variables 1 enforcement 2 238/35 kg 0.53 78.46 0.14 94.33 3 hours 2190 15% moisture tobacco 1 enforcement 4 238/35 kg 0.56 77.24 0.12 95.14 3 hours 2190 25% moisture tobacco 1 enforcement 5 238/35 kg 0.33 86.59 0.15 93.93 3 hours 2190 Add 500 g of citrate to the ion exchanger 1 enforcement 7 USB / 35 kg 0.17 91.58 0.12 97.12 3 hours 2190 15% moisture tobacco 1 enforcement 9 USB / 35 kg 0.14 93.07 0.20 95.20 3 hours 2190 25% moisture tobacco 4 enforcement 1 USB / 3 kg 1.47 20.11 1.13 61.69 2 hours 40 Original pH (5.44) 4 enforcement 3 USB / 3 kg 1.7 7.61 1.08 63.39 2 hours 40 Reduced Tobacco pH (4.1-4.3) 4 enforcement 4 238/3 kg 1.96 14.78 0.72 70.49 2 hours 40 4 enforcement 6 238/3 kg 2.12 7.83 1.36 44.26 2 hours 10 3 enforcement 11 238/15 kg 2.1 8.7 0.65 73.36 15 minutes 200 5 enforcement 3 USB / 3 kg 1.4 22.65 1.11 66.57 2.5 hours 40 Glass Beads, Ion Exchanger

Batch number Nicotine Content (%) Nitrosamine Content (µg / g) USB 238 USB 238 One 2.02 2.46 4.17 2.47 4 1.84 2.30 2.95 2.44 3 1.84 2.29 2.95 2.44 5 1.77 Not recorded 3.32 Not recorded

Example 3

The apparatus shown in FIG. 2 is also a closed system, which comprises a chamber 1 having an inlet 8 and an outlet 9, an interconnecting pipe 10 (pipe 10 being the inlet of the chamber 1). 8) with the outlet 9) and the fluid transport means, i.e. the pump 4). The device further comprises a storage tank 5 interconnected with the chamber 1 by a duct 6. The valve 7 located in the duct 6 closes the tank 5. The UV light source is located in an adjacent position of the pipe 10.

In operation of the apparatus of FIG. 2, about 100 kg of cut tobacco having a suitable moisture content is placed in the chamber 1. The storage tank 5 is filled with carbon dioxide, and the carbon dioxide is then maintained at a constant air pressure by a pump (not shown) and the extraction conditions required by the pump from the storage tank 5 to the chamber 1 and the pipe 10, i. It is transported until a pressure of 250 bar and a temperature of about 50 degrees Celsius are achieved. The tank 5 is then closed by closing the valve 6. Supercritical carbon dioxide then circulates through the chamber 1 (and thus the tobacco contained therein) and the pipe 10 under the operation of the pump 4. The UV light source 11 irradiates the supercritical carbon dioxide extraction medium in the pipe 10. As a result, nitrosamine in the supercritical carbon dioxide decomposes. Decomposition products can then be removed, for example, by passing supercritical carbon dioxide through a metal mesh (not shown). The pipe 10 consists of a material, for example a high-pressure quartz window, which is transparent to UV radiation at least near the UV light source 11. The amount of supercritical carbon dioxide in the interconnect pipe 10 is kept to a minimum by the use of a pipe 10 having a short diameter (ie, a diameter of about 1 cm). After exposure to UV radiation, supercritical carbon dioxide returns to the chamber 1 and again contacts the tobacco therein. Supercritical carbon dioxide circulates for 30 minutes. The chamber 1 and the pipe 10 are then depressurized by opening a vent (not shown). Tobacco treated in this way is free or substantially free of nitrosamines, while the nicotine content of the tobacco is substantially the same before and after treatment.

A further alternative device (not shown) comprises the device shown in FIG. 2 with the nitrosamine removal material held substantially in a fluid permeable container in chamber 1. The fluid may be recycled through the system prior to removal of nitrosamine and for any subsequent removal time thereof.

Claims (66)

A method of treating tobacco wherein tobacco is subjected to treatment with a supercritical fluid extraction medium to extract nitrosamines from the tobacco. The process of claim 1 wherein the nitrosamine is separated from the supercritical fluid extraction medium by adding the extraction medium to a nitrosamine removal process. The method of claim 2, wherein the nitrosamine removal process comprises a chemisorption step. 4. The method of claim 3, wherein the chemisorption step comprises the use of ion exchangers. 3. The method of claim 2, wherein the nitrosamine removal process comprises an adsorption step. 6. The process of claim 5 wherein the adsorbent in the adsorption step is selected from one or more of the group consisting of glass beads, activated carbon, aluminum silicate and zeolite. 3. The method of claim 2, wherein the nitrosamine removal process comprises treatment of the extraction medium with ultraviolet (UV). The method of claim 2, wherein the nitrosamine removal process comprises precipitating nitrosamine from the extraction medium, subjecting the extraction medium to nitrosamine-specific enzyme disruption, or chromatographic separation of the nitrosamines from the extraction medium. The method of claim 2, wherein the nitrosamine removal process comprises various removal processes. 10. The method according to any one of claims 2 to 9, wherein after the nitrosamine removal process, an extraction medium free or substantially free of nitrosamines is contacted with the tobacco so that the extract (s) other than nitrosamine in the extraction medium can be incorporated into or reintroduced in the tobacco. That way. The method of claim 10, wherein the extract (s) comprise nicotine and / or flavoring agents. The method of claim 1, wherein the supercritical fluid extraction medium is supercritical carbon dioxide. The method of claim 1, wherein the acid is added to the tobacco prior to treatment with the tobacco supercritical fluid; A method of adding tobacco to a supercritical fluid prior to treatment with the supercritical fluid. The process according to claim 4 or 5, wherein the acid is added to the ion exchanger or adsorbent. The process according to claim 1, wherein at least one of an organic solvent or an alcohol is added together with or as an alternative to the acid. The method of claim 15, wherein the acid is an organic acid. 17. The method of claim 16, wherein the acid is an organic acid selected from one or more of the group consisting of malonic acid, ascorbic acid, succinic acid, glutanoic acid, adipic acid, malic acid, tartaric acid, mucin acid and citric acid or salt derivatives thereof. 18. The method of claim 17, wherein the organic acid is a citric acid salt. 19. The method of claim 18, wherein the citric acid salt is potassium citrate. 20. The method of any one of claims 1 to 19, wherein the extraction of the nitrosamines from the tobacco into the supercritical fluid occurs at elevated pressure and temperature. The method of claim 20, wherein the supercritical fluid is supercritical carbon dioxide and the pressure is in the range of 100 to 350 bar. The method of claim 21, wherein the pressure is about 200 to 300 bar. The method of claim 22, wherein the pressure is about 240 to 260 bar. The method of claim 20, wherein the temperature is higher than about 35 degrees Celsius. The method of claim 24 wherein the temperature is in a range from about 35 degrees Celsius to about 140 degrees Celsius. 27. The method of claim 25, wherein the temperature is in the range of about 35 degrees Celsius to about 90 degrees Celsius. 27. The method of any one of claims 1 to 26, wherein the tobacco is located in a chamber or cylinder that is closed during the extraction process into its supercritical fluid. 28. The method of any one of claims 20 to 27, wherein the elevated temperature is carried out by heat transfer or electromagnetic radiation. 29. The method of any one of claims 1 to 28, wherein the extraction medium does not remove or very slightly remove nicotine from the tobacco. 30. The method of any one of claims 1 to 29 wherein the pH of the tobacco is less than about 6.5. 31. The method of claim 30, wherein the pH of the acid is less than about 5.5. 32. The method of any one of claims 1-31, wherein the ratio of nitrosamine reduction percentage to nicotine reduction percentage is in the range of about 1.1: 1 to about 18: 1. 33. The method of claim 32, wherein the ratio is in the range of about 1.3: 1 to about 10: 1. The method of claim 33, wherein the ratio is in the range of about 2: 1 to about 6: 1. 35. The method of any one of claims 1 to 34, wherein a suitable mass flow rate of supercritical fluid extraction per kg tobacco is about 1-55 kg / h. 36. The method of claim 35, wherein the mass flow rate is in the range of 10-40 kg / hr. 37. The method of claim 36, wherein the mass flow rate is in the range of 15-35 kg / hr. 38. The method of claim 37, wherein the mass flow rate is about 30 kg / h. 39. The method according to any one of claims 1 to 38, wherein the tobacco treated according to the process is cut tobacco and / or leaf whole tobacco, tobacco powder or reconstituted tobacco. 40. The method of any one of claims 1 to 39, wherein the tobacco is subjected to a microbial killing process. 41. The method of claim 40, wherein the microbial killing process comprises a pasteurization process. 42. The method of claim 41, wherein the tobacco is heated for 30 seconds to 2 minutes to a temperature in the range of about 70 ° C to about 150 ° C. 42. The method of claim 41, wherein the pasteurization process is performed by heating the tobacco by convection heating, microwave heating or high frequency heating by contacting the tobacco with a gas heating medium. 44. The method of any one of claims 40 to 43, wherein the moisture content of the tobacco subjected to the microbial killing process is adjustable by steps before and after conditioning. 42. The method of claim 41, wherein the microbial killing process comprises ionization irradiation, UV irradiation, freeze drying or the use of an electron beam. 46. The method of any of claims 1-45, wherein the tobacco is subjected to a nitrite / nitrate removal process prior to, during or after treatment of the tobacco with the supercritical fluid. 47. The method of claim 46, wherein the nitrite / nitrate removal process comprises a solvent extraction step for removing nitrite / nitrate from tobacco, followed by an ion exchange step for binding nitrite / nitrate. 47. The method of claim 46, wherein the nitrite removal process comprises an oxidation step or the use of microorganisms. 49. The method of any of claims 46-48, wherein ascorbic acid is applied to tobacco and incorporated with a supercritical fluid or with a chemisorption medium. 50. A nitrosamine extraction device used according to any of the preceding claims, wherein the device comprises a first chamber for the treatment of tobacco with supercritical fluid, a second chamber in which the nitrosamine removal process takes place And the chamber is interconnected by interconnecting means, wherein the device is a supercritical fluid supply means for supplying a supercritical fluid, a fluid transport means operable to cause the supercritical fluid to flow around a closed system and a second A nitrosamine extraction device further comprising a nitrosamine removal material present in the chamber. 51. The apparatus of claim 50, wherein the fluid transport means is a pump. 51. The apparatus of claim 50, wherein the fluid transport means is a pressure differential system. 53. The apparatus of any one of claims 50-52, wherein a plurality of interconnected chambers are provided for the treatment of tobacco with supercritical fluid and / or a plurality of interconnected chambers is provided for the nitrosamine removal process. 54. The apparatus of claim 53, wherein the supercritical fluid flows continuously through the chamber. 50. A nitrosamine extraction device for use according to any of claims 1 to 49, wherein the device is a closed system, the closed system having a inlet and an outlet connected by interconnecting means, fluid transport means and nitrosamine removal. Nitrosamine extraction device comprising a means. 56. The apparatus of claim 55, wherein the nitrosamine removal means comprises an ion exchanger or adsorbent held in a supercritical fluid permeable container in the chamber. 59. The closed system of claim 56, wherein the interconnecting means is used for the transport of the supercritical fluid extraction medium from the outlet of the chamber to the inlet of the chamber through the nitrosamine removal process location under the operation of the fluid transport means. 50. A Burley tobacco having an initial nitrosamine content in the range of about 0.3 ppm to about 30 ppm after curing, wherein the Burley tobacco has at least 45% less nitrosamine content after being treated according to the method of any one of claims 1 to 49. Eggplant is Burley tobacco. A Virginia tobacco having an initial nitrosamine content of less than 8.5 ppm after curing, wherein the Virginia tobacco has a nitrosamine content of at least 45% less after it has been treated according to the method of any one of claims 1-49. 61. The Burley or Virginia tobacco of claim 59 or 60, wherein the nitrosamine content is at least 60% less than the original content. 50. A Burley cigarette having an initial nitrosamine content of 5-6 ppm, wherein the burrow tobacco is 3.6 ppm or less after the nitrosamine content has been treated according to any one of claims 1-49. A US blended tobacco having an original nicotine content in the range of 0.10-2.0% and a nitrosamine content in the range of 0.10-1.2 μg / g, wherein the blend is 1: 1 after processing according to any one of claims 1 to 49. US blended tobacco having a ratio of nitrosamine reduction percentage to nicotine reduction percentage in the range of from 10: 1. In a Virginia tobacco blend having an original nicotine content in the range of 0.10-2.0% and a nitrosamine content in the range of 0.10-1.2 μg / g, the blend is processed after processing according to any one of claims 1 to 49. Virginia tobacco blend having a ratio of nitrosamine reduction percentage to nicotine reduction percentage in the range of 1 to 10: 1. 64. A tobacco blend according to claim 62 or 63, wherein the ratio is preferably at least 5: 1. 64. A tobacco blend according to claim 62 or 63, wherein the ratio is preferably at least 8: 1. A method of treating tobacco substantially the same as described above with reference to FIGS. 1 and 2.