Reduction of constituents in tobacco

Abstract

Methods of selectively reducing constituents in tobacco as well as the tobacco obtained by such methods are disclosed. Subcritical fluids, e.g., liquid carbon dioxide, serve as the reduction media.

Claims

1. A tobacco containing a reduced amount of a constituent processed by a method comprising the steps of: (a) providing a vessel containing a tobacco comprising said constituent; (b) contacting said tobacco with a subcritical fluid consisting of carbon dioxide under conditions so that said amount of said constituent dissolves in said subcritical fluid, wherein said subcritical fluid is carbon dioxide at 0-24 C. and 1000-2200 psi and the tobacco of step (a) has a moisture content of at least 30%; and (c) removing said subcritical fluid from said vessel, thereby producing a processed tobacco containing a reduced amount of said constituent, wherein said constituent is a secondary alkaloid.

2. A tobacco containing a reduced amount of secondary alkaloid relative to a primary alkaloid processed by a method comprising the steps of: (a) providing a vessel containing a tobacco comprising said secondary alkaloid and said primary alkaloid; (b) contacting said tobacco with a subcritical fluid under conditions so that a greater amount of said secondary alkaloid relative to said primary alkaloid dissolves in said subcritical fluid, wherein said subcritical fluid is carbon dioxide at 0-24 C. and 1000-2200 psi and the tobacco of step (a) has a moisture content of at least 30%; and (c) removing said subcritical fluid from said vessel, thereby producing a processed tobacco containing a reduced amount of said secondary alkaloid relative to said primary alkaloid, wherein said secondary alkaloid is 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK).

3. A tobacco containing a reduced amount of a polycyclic aromatic hydrocarbon (PAH) processed by a method comprising the steps of: (a) providing a vessel containing a tobacco comprising said PAH; (b) contacting said tobacco with a subcritical fluid under conditions so that said amount of said PAH dissolves in said subcritical fluid, wherein said subcritical fluid is carbon dioxide at 0-24 C. and 1000-2200 psi and the tobacco of step (a) has a moisture content of at least 30%; and (c) removing said subcritical fluid from said vessel, thereby producing a processed tobacco containing a reduced amount of said PAH, wherein said PAH is benzo(a)pyrene.

4. A tobacco containing a reduced amount of a polycyclic aromatic hydrocarbon (PAH) relative to a primary alkaloid processed by a method comprising the steps of: (a) providing a vessel containing a tobacco comprising said PAH and said primary alkaloid; (b) contacting said tobacco with a subcritical fluid under conditions so that a greater amount of said PAH relative to said primary alkaloid dissolves in said subcritical fluid, wherein said subcritical fluid is carbon dioxide at 0-24 C. and 1000-2200 psi and the tobacco of step (a) has a moisture content of at least 30%; and (c) removing said subcritical fluid from the vessel, thereby producing a processed tobacco containing a reduced amount of said PAH relative to said primary alkaloid, wherein said PAH is benzo(a)pyrene.

5. A tobacco containing a reduced amount of a constituent processed by a method comprising the steps of: (a) providing a system comprising a plurality of connected vessels containing a tobacco comprising said constituent; (b) contacting tobacco in a first vessel with a subcritical fluid under conditions so that said amount of said constituent dissolves in said subcritical fluid, wherein said subcritical fluid is carbon dioxide at 0-24 C. and 1000-2200 psi and the tobacco of step (a) has a moisture content of at least 30%; (c) removing said subcritical fluid from said first vessel; and (d) directing said subcritical fluid to a second vessel, thereby producing a processed tobacco containing a reduced amount of said constituent, wherein said constituent is a secondary alkaloid.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic representation of a system suitable for an industrial setting, utilizing, e.g., liquid carbon dioxide under subcritical conditions to reduce the amount of a constituent in tobacco.

(2) FIG. 2 is a schematic representation of a laboratory-scale apparatus, e.g., utilizing liquid carbon dioxide under subcritical conditions to reduce the amount of a constituent in tobacco.

DETAILED DESCRIPTION OF THE INVENTION

(3) Laboratory scale and suitable industrial scale methods of selectively reducing the amount of certain constituents in tobacco are described along with test data detailing the effectiveness of such methods. Notably, these methods are performed on tobacco itself. In addition, the tobacco can be from any source, including dried, cured, or processed, and can further be in the form of finished products, e.g., cigarettes, snuff (moist or dry), and cigars. These methods can reduce the amount of one or more constituents without substantially removing tobacco attributes.

(4) As shown in FIG. 1, an industrial type system utilizing, e.g., liquid carbon dioxide under subcritical conditions, can be used to reduce the amount of one or more constituents in tobacco. Although only one vessel 6 is shown in FIG. 1, it is understood that a plurality of such vessels can be utilized, in series, in a large-scale system.

(5) As further shown in FIG. 1, tobacco 5 is charged to vessel 6, which is then sealed so as to be able to operate under elevated pressure conditions, e.g., necessary to maintain a subcritical fluid as a liquid therein. Subcritical fluid 2, e.g., carbon dioxide, initially stored as shown in supply vessel 1, is directed through and is pumped to a desired pressure by inlet pump 3. After pressurized subcritical fluid 2 passes through inlet pump 3, the liquid proceeds, via circulation pump 4 into vessel 6 and through the charge of tobacco 5. As the liquid subcritical fluid 2 flows through tobacco 5, the amount of constituents in tobacco 5 is reduced. After exiting vessel 6, a subcritical fluid stream, which at this point may be gaseous, flows into and through separator vessel 7. The separator vessel may contain a substance 8, which traps basic constituents and, thereby, depletes the subcritical fluid of any dissolved or suspended constituents. The substance 8 can be drained from separator vessel 7 via drain valve 9, particularly after the solution accumulates a significant amount of constituents. A suitable substance 8 is an aqueous citric acid solution. Other possible substances effective for separating out constituents include, for example, solid magnesium silicate or any other such solution or solid capable of binding the desired constituents.

(6) The subcritical fluid, once depleted of any dissolved or suspended constituents may be recirculated to the vessel 6, as shown, via line R. Circulation pump 4 may be designed such that subcritical fluid entering its inlet from line R may, once again, be pressurized so as to liquefy before entering vessel 6. Those having ordinary skill in the art will recognize that pump 4 may thus act to re-pressurize the subcritical fluid entering pump 4 from either supply vessel 1 or line R. Following completion of the reduction process, the system may be depressurized and constituent-reduced tobacco 5 removed. The process time may vary depending on a variety of processing parameters. One of ordinary skill in the art will readily be able to determine suitable process times. Ranges of appropriate process times are discussed below in connection with trial runs performed on a laboratory-scale system.

(7) The virtually continuous circulation of subcritical fluid and the inherent capability of reducing constituents from multiple charges of tobacco residing in a plurality of vessels are two clear advantages to be exploited. Elimination of costly down time brought about by emptying and recharging of a single vessel 6 is achievable with use of several (typically three or four) valved vessels 6 operating in series. Vessels may also be operated in parallel. As noted above, subcritical fluid is pumped in series through the several vessels 6. When the charge of tobacco in one of the vessels has become constituent-reduced and is ready to be removed, the subcritical fluid can be diverted from that vessel to another vessel containing tobacco or a separation vessel. This subcritical fluid may still be effective for reducing constituents from other charges of tobacco in other vessels. The vessel from which tobacco is ready to be removed may be isolated from the system without interfering with on-going reductions in other vessels. New tobacco may then be placed into the vessel, and the process can continue without overall system interruption.

(8) Preferably, treated tobacco substantially retains the taste and aroma of untreated tobacco. Alternatively, any flavor or aroma compounds removed during treatment may be re-deposited in the tobacco, e.g., after removal of any constituents from the subcritical fluid. The flavor and aroma content of tobacco can be determined by taste and smell tests.

(9) The following examples illustrate various embodiments of the present invention and are not intended to be limiting in any way.

Example 1. Reduction of Constituents Using Subcritical Carbon Dioxide

(10) FIG. 2 shows a schematic representation of a laboratory-scale system that can be used to produce reduced constituent content in tobacco. The representative data of Table 1 were developed using such a system, which was operated in the following manner. A sample of tobacco 16 was placed in vessel 15, and the vessel was sealed. Gaseous subcritical fluid 12 was supplied from cylinder 11 and admitted to the system. When pressure (as measured by gauges A and B) reached cylinder pressure, compressor pump 13 was energized to liquefy the fluid 12. Temperature was adjusted and controlled using preheater 14 and was measured with thermocouples C and D. Flow of subcritical fluid 12 was then started using adjustable flow control valve 17 that was set so as to operate at a selected flow rate measured by flow meter 19. The range of flow rate may be between about 5 grams/min to 150 grams/min; for convenience 20-30 grams/min rate was chosen for the experimental runs. Pressure was reduced across valve 17, resulting in the gaseous subcritical fluid passing into filter flask 18 into which constituent-rich extract could be collected. Alternatively, the subcritical fluid was vented to a waste vessel. The total flow of subcritical fluid 12 passed through the charge of tobacco 16 during the duration of a run was measured by dry test meter 20. In this laboratory system, no separation vessel was used to facilitate recirculation of subcritical fluid 12. Vessel 15 was a stainless steel tube having a length of 10 inches, an outside diameter of 1 inch, and a volume of about 60 ml. After treatment, the tobacco 16 was analyzed for its constituent content and the percent reduction of constituent content. The run time necessary to produce such tobacco may be anywhere between about 2 and 14 hours, preferably in the range of about 4-8 hours.

(11) The carbon dioxide utilized according to the present invention should be a subcritical fluid (critical point 31 C. and 1070 psi), e.g., a liquid. In practicing the process of the present invention, carbon dioxide temperature, pressure, or both can be adjusted to ensure that it is a subcritical fluid, for example, by an inlet heat exchanger (not shown). The run pressure was held essentially constant (in the range of between about 1000 and 2200 psi) for a given run. Runs were performed at essentially constant temperatures ranging between about 0 C. and 24 C. Although a range of mass of subcritical fluid:mass of tobacco ratios can be used, typically between 21 to 50 grams of carbon dioxide per gram of tobacco were used to reduce the maximum amount of constituent.

(12) Table 1 shows data on the reduction of constituents in tobacco employing the laboratory-scale system described above. As shown in Table 1, the process is selective for the reduction of secondary alkaloids relative to primary alkaloids.

(13) TABLE-US-00001 TABLE 1 Reduction of constituents in tobacco with carbon dioxide % % Mass of Moist- Secondary % Primary Conditions CO.sub.2: Mass ure Alkaloids Alkaloids Sample ( C./psi) pH of Tobacco Content Reduction Reduction 1 17/1200 6 21 15 39 4 2 17/1200 6 23 30 81 0 3 14/1200 6 24 52 74 0 4 19/1200 8 50 58 91 2

Example 2. Reduction of Constituents Using Subcritical Freon 22

(14) Additional experiments according to the method of Example 1 were carried out using Freon 22 (chlorodifluoromethane) (critical point 96 C., 716 psi) instead of carbon dioxide. The data are shown in Table 2. Exemplary conditions for use of Freon 22 include 0 to 50 C., 100 to 2000 psi, and a mass of Freon 22 to mass of tobacco ratio of 20 to 100.

(15) TABLE-US-00002 TABLE 2 Reduction of constituents in tobacco with Freon 22 Mass of % Freon 22: % Secondary % Primary Conditions Mass of Moisture Alkaloids Alkaloids Sample ( C./psi) pH Tobacco Content Reduction Reduction 1 27/1200 6 53 15 65 52 2 6 55 98 77 3 34/1000 8 33 55 95 44

Example 3. Reduction of Secondary Alkaloids Using Subcritical Propane

(16) Additional experiments according to the method of Example 1 were carried out using propane (critical point 96.7 C., 617 psi) instead of carbon dioxide. The data are shown in Table 3. In general, the conditions for use of propane are 0 to 50 C., 100 to 2000 psi, and a mass of propane to a mass of tobacco ratio of 20 to 100.

(17) TABLE-US-00003 TABLE 3 Reduction of secondary alkaloids in tobacco with propane Mass of % Propane: % Secondary % Primary Conditions Mass of Moisture Alkaloids Alkaloids Sample ( C./psi) pH Tobacco Content Reduction Reduction 1 20/1200 6 22 15 13 10 2 20/1200 6 22 60 58 3 3 20/1200 8 25 60 51 67

Example 4. Reduction of PAHs Using Subcritical Propane

(18) Table 4 shows data from an experiment according to Example 1 on the reduction of PAHs in tobacco by treatment with subcritical propane.

(19) TABLE-US-00004 TABLE 4 Reduction of PAHs in tobacco with propane Mass of Propane: % % Primary Conditions Mass of Moisture % PAHs Alkaloids Sample ( C./psi) pH Tobacco Content Reduction Reduction 1 30/1000 6 24 16 77 14

Example 5. Reduction of Constituents Using Other Subcritical Fluids

(20) The amount of constituents in tobacco may also be reduced using the methods of the invention by employing ethane (critical point 32.2 C., 708 psi) or nitrous oxide (critical point 36.5 C., 1046 psi). Exemplary conditions for use of ethane include 0 to 30 C., 500 to 2000 psi, and a mass of ethane to a mass of tobacco ratio of 20 to 100. Exemplary conditions for use of nitrous oxide include 0 to 35 C., 500 to 2000 psi, and a nitrous oxide to tobacco ratio of 20 to 100.

Other Embodiments

(21) The description of the specific embodiments of the methods and tobacco obtained therefrom is presented for the purposes of illustration. It is not intended to be exhaustive nor to limit the scope of the invention to the specific forms described herein. Although the invention has been described with reference to several embodiments, it will be understood by one of ordinary skill in the art that various modifications can be made without departing from the spirit and the scope of the invention, as set forth in the claims.

(22) Other embodiments are within the claims.