METHOD OF MAKING A TOBACCO EXTRACT

Abstract

Embodiments described herein include a method of making a tobacco extract comprising; (a) contacting tobacco with an extraction solvent at a first temperature and first pressure which are selected such that the extraction solvent is supercritical, such that tobacco flavor and/or aroma components are extracted from the tobacco into the solvent; (b) separating the residual tobacco solids from the supercritical extraction solvent containing tobacco components; (c) exposing the extraction solvent containing tobacco components to conditions in a vessel at which the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, (d) contacting the residual tobacco solids with an extraction solvent at a second temperature and second pressure which are selected such that the extraction solvent is supercritical, such that nicotine are extracted from the tobacco into the extraction solvent; and wherein the second temperature and/or second pressure is higher than the respective first temperature or first pressure; (e) separating the residual tobacco solids from the supercritical extraction solvent containing tobacco components; (f) exposing the extraction solvent containing tobacco components to conditions in a vessel at which the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, wherein during step (f), the vessel contains an entrapment solvent which dissolves the tobacco components released from the extraction solvent, and wherein the entrapment solvent comprises an aerosol generating agent.

Claims

1. A method of making a tobacco extract, the method comprising: (a) contacting tobacco with an extraction solvent at a first temperature and first pressure which are selected such that the extraction solvent is supercritical, such that tobacco flavor and/or aroma components are extracted from the tobacco into the solvent; (b) separating the residual tobacco solids from the supercritical extraction solvent containing tobacco components; (c) exposing the extraction solvent containing tobacco components to conditions in a vessel at which the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, (d) contacting the residual tobacco solids with an extraction solvent at a second temperature and second pressure which are selected such that the extraction solvent is supercritical, such that nicotine are extracted from the tobacco into the extraction solvent; and wherein the second temperature and/or second pressure is higher than the respective first temperature or first pressure; (e) separating the residual tobacco solids from the supercritical extraction solvent containing tobacco components; (f) exposing the extraction solvent containing tobacco components to conditions in a vessel at which the extraction solvent is subcritical, thereby releasing the tobacco components from the extraction solvent, wherein at (f), the vessel contains an entrapment solvent which dissolves the tobacco components released from the extraction solvent, and wherein the entrapment solvent comprises an aerosol generating agent.

2. The method according to claim 1, wherein an entrapment solvent is present in the vessel at (c).

3. The method according to claim 2, wherein the same entrapment solvent is used at (c) and (f).

4. The method according to claim 1, wherein the extraction solvent comprises carbon dioxide.

5. The method according to claim 4 wherein at (a), the temperature is in the range of about 308-473K, preferably about 328-350K, and the pressure is in the range of about 8-85 MPa, preferably about 20-30 MPa.

6. The method according to claim 1, wherein the entrapment solvent comprises a polyol, such as glycerol and/or propylene glycol.

7. The method according to claim 1, further comprising: (g) mixing the liquid fraction resulting from (c) with the liquid fraction resulting from (f).

8. The method according to claim 1, further comprising providing the entrapment solvent containing dissolved tobacco components in a cartridge, wherein the cartridge is configured for use in a smoking article.

9. A tobacco extract obtainable by a method according to claim 1.

10. A cartridge configured for use in a smoking article, the cartridge containing a tobacco extract according to claim 9.

11. A smoking article containing a tobacco extract according to claim 9.

12. Use of a tobacco extract obtainable by a method according to claim 1 to generate an inhalable aerosol.

13. Use of a tobacco extract according to claim 12, wherein the tobacco extract is used in a smoking article.

Description

DETAILED DESCRIPTION

[0037] For the avoidance of doubt, the term “tobacco extract” as used herein refers to the liquid output resulting from any of steps (c), (f) and (g) above. Typically, the extract will be tobacco components dissolved in the entrapment solvent.

[0038] The phrase “nicotine is not substantially dissolved/extracted” may, in some cases, mean that less than 15 wt %, suitably 12 wt %, 10 wt %, 8 wt %, 6 wt % or 4 wt %

[0039] (calculated based on the tobacco dry weight) of the nicotine in the tobacco starting material is dissolved in the extraction solvent.

[0040] The extraction solvent may comprise or may be a supercritical fluid in some steps of the method described herein. A supercritical fluid is any substance where, at a temperature and pressure above its critical point, distinct liquid and gas phases do not exist. Supercritical fluids can effuse through solids like a gas, and dissolve materials like a liquid. Supercritical fluids have a higher fluid density than gases and therefore have a higher solvent capacity.

[0041] In some cases, one or more flavors may be added to the tobacco extract. As used herein, the term “flavor” refers to materials which, where local regulations permit, may be used to create a desired taste or aroma in a product for adult consumers.

[0042] They may include extracts (e.g., licorice, hydrangea, Japanese white bark magnolia leaf, chamomile, fenugreek, clove, menthol, Japanese mint, aniseed, cinnamon, herb, wintergreen, cherry, berry, peach, apple, Drambuie, bourbon, scotch, whiskey, spearmint, peppermint, lavender, cardamom, celery, cascarilla, nutmeg, sandalwood, bergamot, geranium, honey essence, rose oil, vanilla, lemon oil, orange oil, cassia, caraway, cognac, jasmine, ylang-ylang, sage, fennel, piment, ginger, anise, coriander, coffee, or a mint oil from any species of the genus Mentha), flavor enhancers, bitterness receptor site blockers, sensorial receptor site activators or stimulators, sugars and/or sugar substitutes (e.g., sucralose, acesulfame potassium, aspartame, saccharine, cyclamates, lactose, sucrose, glucose, fructose, sorbitol, or mannitol), and other additives such as charcoal, chlorophyll, minerals, botanicals, or breath freshening agents. They may be imitation, synthetic or natural ingredients or blends thereof. They may be in any suitable form, for example, oil, liquid, or powder.

[0043] As used herein, an “aerosol generating agent” is an agent that promotes the generation of an aerosol on heating. An aerosol generating agent may promote the generation of an aerosol by promoting an initial vaporization and/or the condensation of a gas to an inhalable solid and/or liquid aerosol.

[0044] In general, suitable aerosol generating agents include, but are not limited to: a polyol such as sorbitol, glycerol, and glycols like propylene glycol or triethylene glycol; a non-polyol such as monohydric alcohols, high boiling point hydrocarbons, acids such as lactic acid, glycerol derivatives, esters such as diacetin, triacetin, triethylene glycol diacetate, triethyl citrate or myristates including ethyl myristate and isopropyl myristate and aliphatic carboxylic acid esters such as methyl stearate, dimethyl dodecanedioate and dimethyl tetradecanedioate. In some cases, the aerosol generating agent comprises one or more of glycerol, propylene glycol, triacetin and isopropyl myristate, suitably glycerol and/or propylene glycol.

[0045] The weight ratio of aerosol generating agent to tobacco (dry weight) may be from about 2:1 to about 1:3, suitably from 3:2 to about 1:2, suitably about 1:1.

[0046] The method according to the invention may additionally comprise an initial step of adding water to the tobacco. The amount of water added may be from about 2% to about 20% based on the dry weight of tobacco, suitably from about 2%, 5% or 8% to about 12%, 15%, 18% or 20%. This pre-treatment with water increases the transfer of polar tobacco components (such as flavors) from the tobacco to the entrapment solvent.

[0047] In the process according to the invention, a higher pressure and temperature under supercritical conditions increases the solvent capacity and increases the efficiency of extraction. However, more energy is required to achieve and maintain higher pressures and temperatures and such conditions can lead to decomposition of volatile tobacco components, such as flavors and aromas.

[0048] Thus, the supercritical conditions in steps (a) and (d) are suitably selected to balance these conflicting requirements.

[0049] The transfer to subcritical conditions reduces the fluid density of the extraction solvent and consequently results in precipitation of the tobacco components. The conditions must be such that the pressure is below the critical pressure of the extraction solvent and/or the temperature is below the critical temperature of the extraction solvent. For thermal efficiency, the conditions are suitably such that the pressure is below the critical pressure of the extraction solvent while the temperature remains above the critical temperature.

[0050] The efficiency of separation of the tobacco components and the extraction

[0051] solvent improves as the conditions move further below the critical point of the extraction solvent. However, the extraction solvent will typically be collected and stored after separation (requiring compression); in some cases, it may be recycled into an extraction chamber. Thus, the subcritical conditions are suitably not too far below the critical point to improve energy efficiency. The subcritical conditions are suitably selected to balance these conflicting requirements. Where the extraction solvent comprises carbon dioxide, the pressure at which extraction occurs may, in some cases, be from about 3 MPa, 4 MPa, 5 MPa or 5.5 MPa to about 7.3 MPa, 7 MPa, 6.5 MPa, 6 MPa, 5.5 MPa or 5 MPa, suitably from 3-7.3 MPa, or 4-6 MPa. Where the extraction solvent comprises carbon dioxide, the temperature of the subcritical conditions under which separation occurs may, in some cases, be from about 280K, 300K, 320K or 330K to about 473K, 430K, 390K or 350K, suitably from 308-473K, 308-430K, or 328-350K.

EXAMPLES

[0052] Analytical Methods

[0053] Water activity values reported below were measured at 24.9-25.2° C. using the Aqualab Prewater Activity meter. The values were determined using the dewpoint method.

[0054] Viscosity values reported below were measured at 25° C. using a Gemini Rheometer from Bohlin Instruments.

[0055] Pre-Extraction (Pre-Treatment of Tobacco):

[0056] Ground Virginia tobacco leaf of the particle size ranging from 355 μm to 3.5 mm was pre-treated by addition of water (10% of total tobacco weight). The mixture of tobacco and water was left for equilibration for 15 minutes post water addition (which is sufficient time for the water to be fully absorbed).

[0057] The pre-treated tobacco (1.2 kg plus 10 wt % water) was placed in a stainless steel extraction basket and the basket placed in an extraction vessel (5 L autoclave). The basket was closed at its ends by sinter metal plates (pore diameter 100 μm, pressure drop across the plate is no more than 1 bar), which distributed the supercritical fluid at the entrance and prevented egress of solid particles at the exit. The use of the basket also allowed the fast charge and discharge of the extraction vessel. The basket was sealed against the extraction vessel wall in order to prevent flow of the supercritical fluid around it.

Example 1: Example of Process According to the Invention

[0058] The extraction vessel was linked to a separation vessel by a transfer line. A pressure regulation valve was present in the line. Carbon dioxide may suitably be

[0059] pumped through the system at the rate 5-23 kg/hr. In this case, carbon dioxide was pumped through the system at the rate of 10 kg/hr. 1.2 kg of glycerol was provided in the separation vessel. The separation chamber was maintained at 4.5 MPa and 318K.

[0060] During a first extraction step, the conditions in the extraction vessel were 10 MPa and 318K. The first extraction conditions were maintained for 1 hour. The glycerol was then drained from the separation chamber.

[0061] Supercritical CO2 at these conditions has a density of approximately 628.7 kg/m.sup.3. This solvent has a relatively low solvent power resulting in a gentle extraction of the volatile (low molecular weight) compounds. At such a low temperature the volatiles decomposition is minimized. These conditions also minimize the extraction of nicotine and non-volatiles and avoids the co-extraction of the high-molecular weight compounds.

[0062] Gaseous CO2 exited the separator after passing through a liquid/gas divider (which removed any remaining liquid extract that was entrained in the gas). The CO2 was collected and recycled into the extraction chamber.

TABLE-US-00001 Water Virginia Nicotine Water NNN NNK Viscosity Density activity tobacco (mg/g) (wt %) (ng/g) (ng/g) (Pa s) pH (g/cm.sup.3) (Aw) Extracted 0.62 1.53 21.8 12 0.66 5.59 1.26 0.07 at 10 MPa and 318K

[0063] A further 1.2 kg of fresh glycerol was then placed in the separation chamber in preparation for the second extraction step. During the second extraction step, the conditions in the extraction vessel were 26 MPa and 338K. These conditions were maintained for 2 hours, after which the entire system was depressurized and the extract was drained from the separation chamber.

[0064] The second extraction step is completed at this higher pressure and for longer time than the first extraction step in order to extract the maximum amount of nicotine from tobacco leaves.

[0065] Supercritical CO2 at these conditions has the density of approximately 771.2 kg/m.sup.3. This increased density means that the solvent power is increased, and higher molecular weight compounds are extracted.

[0066] Gaseous CO2 exited the separator after passing through a liquid/gas divider (which removed any remaining liquid extract that was entrained in the gas). The CO2 was collected and recycled into the extraction chamber.

TABLE-US-00002 Water Virginia Nicotine Water NNN NNK Viscosity Density activity tobacco (mg/g) (wt %) (ng/g) (ng/g) (Pa s) pH (g/cm.sup.3) (Aw) Extracted 7.25 5.85 175 85 0.33 6.83 1.24 0.2 at 26 MPa and 338K

[0067] Further, the inventors observed that the extract obtained by extraction under the first set of conditions has a pale yellow color. The extract obtained by extraction under the second set of conditions has a darker yellow color because it contains more nicotine.

Example 2: Example of Process According to the Invention

[0068] The pre-extraction treatment and the subsequent processing steps of example 1 were repeated, except that Burley tobacco was used as the starting material. The resulting extracts are characterized below:

TABLE-US-00003 Nicotine Water NNN NNK Burley tobacco (mg/g) (wt %) (ng/g) (ng/g) Extracted at 10 MPa 1.95 1.32 691 49.2 and 318K Extracted at 26 MPa 19.443 6.09 2187 266 and 338K

[0069] Comparative Test

[0070] A comparative test was run using the same apparatus as in example 1. However, the conditions were supercritical (26 MPa and 338K) throughout the apparatus and the extraction was completed in a single step. All other aspects of the comparative test were the same as in example 1.

[0071] The comparative test is a representative example of the processes described generally in EP1915064.

TABLE-US-00004 Water Virginia Nicotine Water NNN NNK Viscosity Density activity tobacco (mg/g) (wt %) (ng/g) (ng/g) (Pa s) pH (g/cm.sup.3) (Aw) Comp. 4.7 5.5 71.1 49.1 0.32 6.73 1.25 0.24 test

[0072] Similar results have been observed when using Oriental or Burley starting tobaccos.

[0073] The various embodiments described herein are presented only to assist in understanding and teaching the claimed features. These embodiments are provided as a representative sample of embodiments only, and are not exhaustive and/or exclusive. It is to be understood that advantages, embodiments, examples, functions, features, structures, and/or other aspects described herein are not to be considered limitations on the scope of the invention as defined by the claims or limitations on equivalents to the claims, and that other embodiments may be utilized and modifications may be made without departing from the scope of the claimed invention. Various embodiments of the invention may suitably comprise, consist of, or consist essentially of, appropriate combinations of the disclosed elements, components, features, parts, steps, means, etc., other than those specifically described herein. In addition, this disclosure may include other inventions not presently claimed, but which may be claimed in future.