Method for producing improved liquid tobacco extract

Abstract

A method for producing a liquid tobacco extract includes preparing a tobacco material, heating the tobacco material at an extraction temperature of 100°C to 160°C for at least 15 minutes, collecting volatile compounds released from the tobacco material during the heating step, and forming a liquid tobacco extract containing the collected volatile compounds. The tobacco material is microwave heated during at least one step of the method.

Description

[Technical Field]

[0001] The present invention relates to methods for producing liquid tobacco extracts and to the liquid tobacco extracts produced by such methods. [Background technology]

[0002] Aerosol generation systems for delivering aerosols to a user are known, each comprising an atomizer configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine formulation. Some known aerosol generation systems include a thermal atomizer, such as an electric heater, configured to heat and vaporize the liquid formulation to generate the aerosol. One popular type of electrically heated aerosol generation system is an electronic cigarette. Other known aerosol generation systems include non-thermal atomizers configured to generate an aerosol from the liquid formulation, for example, using impinging jet, ultrasonic, or vibrating mesh technology.

[0003] Several methods are known for producing liquid tobacco extracts from tobacco material. Liquid tobacco extracts can be produced by a high-temperature extraction process in which nicotine and other volatile flavor compounds are extracted from the tobacco material and collected in a suitable solvent to form a natural liquid tobacco extract.

[0004] Maceration methods are also known, in which tobacco material is held in suspension in an extraction liquid for periods of up to several weeks or even months. The resulting slurry is then filtered, and the collected liquid phase can be used to produce a vaporizable liquid formulation. In one such method, the so-called "cold maceration method," there is generally no way to control the extraction conditions (e.g., temperature and pressure). For example, in a variant of the maceration method described in U.S. Patent No. 2012 / 192880, the slurry is heated to above 100 degrees Celsius.

[0005] The liquid phase collected during filtration of the slurry represents the primary product of the maceration process and tends to be highly diluted and low in non-polar tobacco flavor species. Furthermore, the liquid phase typically contains little or no nicotine. Therefore, the liquid extract obtained by maceration generally needs to be supplemented with additional ingredients, such as nicotine salts and glycerin, before it can be used in vaporizable liquid formulations.

[0006] An alternative process is known in which tobacco material is essentially boiled in water for several hours or even days to form a vapor phase, and the distillate obtained by condensation of the vapor phase is continuously collected in a vessel. Over time, an oily, waxy layer containing a high proportion of non-polar compounds builds up on the surface of the distillate.

[0007] Meanwhile, a waxy layer accumulates, and the aqueous portion containing nicotine and other water-soluble compounds is recycled to the boiler. To increase the extraction yield, a non-polar co-solvent may optionally be fed to the boiler along with the aqueous portion. Meanwhile, the waxy phase is collected and ultimately forms the primary product of one such steam distillation process. This product, often referred to as "tobacco essential oil," contains a high proportion of non-polar compounds present in tobacco, such as fatty acids and neophytadiene. Tobacco essential oil obtained by one such method typically does not contain nicotine.

[0008] It is also known to subject tobacco materials to extraction processes involving the use of volatile non-polar solvents. Examples of suitable solvents include short alkanes, either cyclic or acyclic, and chlorinated solvents such as dichloromethane. In one such process, excess solvent can be evaporated by controlled heating under vacuum. Typically, this is done in the presence of ethanol, which has a higher boiling point than the extraction solvent, so that even traces of the extraction solvent can be detected.

[0009] One primary product of such solvent-assisted extraction processes, often referred to as "tobacco absolute," may contain traces of ethanol. This is a waxy product that contains a concentrated mixture of most non-polar compounds that can be extracted with a particular solvent, including nicotine, which is generally present in relatively high concentrations.

[0010] An alternative extraction process involves contacting tobacco material with a solvent under supercritical conditions, such as supercritical carbon dioxide. One such process, disclosed in U.S. Patent No. 2013 / 160777, relies on the principle that volatile substances within a feed material contacted with a supercritical fluid can be separated into a supercritical phase. After dissolution of any soluble materials, the supercritical fluid containing the dissolved substances can be removed, and the dissolved components of the feed material can be separated from the supercritical fluid. The primary product of a supercritical extraction process is substantially similar to the "tobacco absolute" of a solvent-assisted extraction process carried out at lower temperatures and pressures; it contains no residual solvent, typically has high levels of waxy, non-polar compounds, and generally contains nicotine, which is present in relatively high concentrations.

[0011] However, all tobacco extracts obtained by methods known in the art tend to have very low, if any, levels of compounds associated with heated tobacco flavor, such as furaneol.

[0012] Generally, as discussed above, liquid tobacco extracts obtained by these known extraction processes may have low levels of nicotine. Furthermore, liquid tobacco extracts obtained by these extraction processes may have low levels and a limited variety of flavor species. Liquid tobacco extracts obtained by these extraction processes may also have high levels of undesirable compounds. Generally, the concentrations of nicotine, flavor species, and undesirable compounds obtained by these extraction processes may be significantly affected by the type or types of tobacco used as the starting material.

[0013] It is an object of the present invention to alleviate one or more of the disadvantages of liquid tobacco extracts obtained by known processes. In particular, it would be desirable to provide new and improved methods for the production of liquid tobacco extracts. It would be especially desirable to provide a method for producing liquid tobacco extracts that can be performed more efficiently than existing processes. Summary of the Invention

[0014] The present disclosure relates to a method for producing a liquid tobacco extract from a tobacco material. The method may include preparing a tobacco material. The tobacco material may be heated to an extraction temperature of about 100 to about 160 degrees Celsius. Heating may be carried out for at least 15 minutes. The method may further include collecting volatile compounds released from the tobacco material during the heating step. The method may further include forming a liquid tobacco extract containing the collected volatile compounds. The tobacco material may be microwave heated during at least one step of the method.

[0015] According to the present invention, there is provided a method for producing a liquid tobacco extract, the method comprising the steps of preparing a tobacco material, heating the tobacco material at an extraction temperature of about 100° C. to about 160° C. for at least about 15 minutes, collecting volatile compounds released from the tobacco material during the heating step, and forming a liquid tobacco extract containing the collected volatile compounds. According to the present invention, the tobacco material is microwave heated during at least one step of the method.

[0016] According to the present invention there is further provided a liquid tobacco extract produced by the method of the present invention as defined above.

[0017] As used herein in connection with the present invention, the term "liquid tobacco extract" refers to the direct product of an extraction process performed on tobacco material. Therefore, tobacco extracts typically include a mixture of natural components separated from, removed from, or derived from natural tobacco material using tobacco extraction processing conditions and techniques. Thus, in one such process, extracted tobacco components are removed from the natural tobacco material and separated from unextracted tobacco components. According to the present invention, an extraction process for producing a liquid tobacco extract involves heating a tobacco material under specific heating conditions and collecting the resulting volatile compounds. The volatile compounds become gaseous upon release from the tobacco material. Thus, a liquid tobacco extract consists of a mixture of natural tobacco components derived from the tobacco material and extracted or formed during the extraction process, typically combined with one or more materials other than the tobacco material, such as the non-aqueous extraction solvent used during the extraction process. As described in more detail below, volatile compounds released from the starting tobacco material can be collected using absorption techniques, in which the volatile compounds are trapped in the non-aqueous extraction solvent. As an example, an inert gas stream containing the volatile compounds may be directed toward a container of non-aqueous extraction solvent. The non-aqueous extraction solvent is preferably an aerosol former.

[0018] The present invention relates to novel microwave extraction methods that include a step of microwave heating a tobacco material at any stage during the extraction process. As explained in more detail below, the tobacco material can be microwave heated prior to the heating step, during which the tobacco material is heated to a temperature of 100°C to 160°C, or microwave heating can occur during the heating step.

[0019] The inclusion of a microwave heating step in the extraction method of the present invention has been found to significantly increase nicotine extraction yields, in some cases by up to 600 percent, compared to comparable extraction methods without the microwave heating step. This effect is believed to be due to the way microwaves heat tobacco from the inside by rapidly heating water molecules within tobacco cells. As the water within tobacco cells boils, the volume within the cells rapidly expands, eventually rupturing the cell walls. This increases the permeability of the plant material and, importantly, releases components contained within the cell walls, such as nicotine. These components are then more readily extracted during the heating step, increasing the yield of these components.

[0020] Microwave heating typically provides greater penetration depth and more rapid heating of the tobacco material than conventional resistance heating methods, which can advantageously result in a reduction in the time required to carry out the extraction method. For example, the inclusion of a microwave heating step has been found by the inventors to result in a reduction of up to 80 percent in the duration of the heating step. Furthermore, it can result in a reduction in energy usage of up to 40 percent. Overall, the inclusion of a microwave heating step allows the extraction process to be carried out very efficiently in terms of both energy and time.

[0021] As mentioned above, the method of using microwaves to heat the tobacco material from within the tobacco cells also allows for more uniform heating of the tobacco material compared to traditional heating methods such as resistance heating, which can only heat the tobacco material from the outside.

[0022] Microwave heating of tobacco material can be carried out using relatively simple, low-cost equipment, which can be easily incorporated into existing extraction equipment and methods.

[0023] In addition to the benefits provided by the microwave heating process, the extraction method of the present invention advantageously provides an improved liquid tobacco extract with a significantly improved balance of desirable and undesirable compounds by using an extraction temperature within a specific range in combination with a specifically defined heating time. In particular, the extraction method of the present invention provides a liquid tobacco extract in which the ratio of undesirable compounds to desirable compounds in the tobacco material is maximized. For example, by using a specific combination of a defined extraction temperature and time, it is possible to optimize the level of nicotine compounds while minimizing the level of undesirable compounds such as furans, carbonyls, phenols, and TSNAs.

[0024] The inventors of the present invention have found that, in contrast to the existing extraction processes described above, the method according to the present invention advantageously provides a liquid tobacco extract that is significantly higher in the content of compounds associated with the flavor of heated tobacco, such as furaneol. These compounds are substantially absent or present in trace amounts in tobacco extracts obtained by maceration processes, and typically contain little or no nicotine. These compounds are also generally absent or present in trace amounts in tobacco extracts obtained using solvents, including under supercritical conditions. Similarly, tobacco essential oils obtained by distillation processes also typically contain very low, if any, content of such compounds associated with the flavor of heated tobacco.

[0025] The liquid tobacco extracts obtained by the methods of the present invention exhibit significant compositional differences compared to tobacco extracts obtained by existing extraction processes and can be used as e-liquids or for the preparation of e-liquids that, upon heating, produce aerosols with different compositional and flavor characteristics than currently available e-liquids. In particular, the liquid tobacco extracts obtained by the methods of the present invention can be used to produce aerosols that provide a heated tobacco taste that is more similar to aerosols produced by conventional cigarettes, or aerosols produced when heating tobacco in a heated non-combustion device, compared to available aerosols produced from existing liquid nicotine compositions.

[0026] The extraction method of the present invention allows for the production of liquid tobacco extracts with optimized levels of nicotine and flavor compounds without adding such compounds after extraction. Thus, the resulting liquid tobacco extract can be advantageously used directly to provide a nicotine composition. The resulting liquid tobacco extract can also be modified by one or more additional processing steps or mixed with one or more additional ingredients to form a nicotine composition. The nicotine composition may be intended for use in electronic cigarettes or other aerosol-generating systems.

[0027] As noted above, aerosol generation systems for delivering an aerosol to a user are known that include an atomizer configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine composition.

[0028] The method for producing a liquid tobacco extract of the present invention can be effectively used with all types and grades of tobacco, including burley, flue-cured, and oriental tobacco. The steps of the method can be easily adjusted to provide a consistent liquid tobacco extract for various blends of tobacco types. The extraction method is also suitable for various forms of tobacco material.

[0029] In some cases, the tobacco material can be heated without the need for significant pre-treatment steps, and therefore the method can be carried out efficiently.

[0030] During the method of the present invention, the tobacco material is heated directly and is not suspended in a liquid solvent for the heating step, as is the case with many types of prior art extraction processes. This allows for greater control over the heating conditions of the tobacco material, making the extraction process more efficient. During heating, volatile compounds are released from the tobacco material in gaseous form.

[0031] As defined above, in the method according to the present invention, the tobacco material is microwave heated at some stage during extraction, preferably before or during the heating step to optimize the effect of microwave heating on the extraction yield.

[0032] In certain embodiments of the present invention, the step of preparing the tobacco material includes pretreating the tobacco material by microwave heating to rupture the tobacco cells prior to the heating step. In methods according to these embodiments, microwave heating of the tobacco material is therefore performed as a pretreatment step prior to the main extraction. As described above, microwave heating disrupts the cell walls of the tobacco material and releases nicotine from within the tobacco cells, making the nicotine more available during the following heating step.

[0033] Preferably, during the pre-treatment step, the tobacco material is microwave heated to a temperature of from about 90 degrees Celsius to about 160 degrees Celsius, more preferably from about 95 degrees Celsius to about 110 degrees Celsius.

[0034] Preferably, during the pretreatment step, microwave heating is carried out for about 1 minute to about 5 minutes.

[0035] Optionally, in methods according to the invention in which the tobacco material is pretreated by microwave heating, the tobacco material is cooled to ambient temperature (22 degrees Celsius) before the start of the heating step to optimize the effectiveness of the main heating step. In some methods according to the invention, there may be no cooling step between microwave pretreatment and the heating step. This may improve the efficiency of the process, as the tobacco material may enter the main heating step at a high temperature.

[0036] Optionally, the tobacco material is microwaved during the pretreatment step in a stream of inert gas, such as nitrogen, which is believed to maintain humidity at a relatively low level so that microwave propagation can be optimized, thereby maximizing the positive impact of microwaves on the extraction of nicotine and other compounds.

[0037] As noted above, in embodiments in which the tobacco material is pretreated by microwave heating prior to the main heating step, the step of heating the tobacco material to a temperature of 100°C to 160°C may be carried out by conventional heating, e.g., resistive heating or steam heating. Conventional heating may be carried out, for example, in a conventional oven or dryer. In some embodiments, the tobacco material may be further subjected to microwave heating during the heating step, instead of or in combination with conventional heating, as described in more detail below.

[0038] Alternatively or in addition to including a pre-treatment step involving microwave heating, the step of heating the tobacco material to a temperature of 100°C to 160°C may include microwave heating the tobacco material. In such embodiments, microwave heating of the tobacco material is carried out during the main extraction step, during which volatile compounds are extracted in gaseous form from the tobacco material by heating. Thus, microwave heating is used to increase the temperature of the tobacco material to volatilize the tobacco compounds and to rupture the tobacco cells, as described above, to release components from the tobacco cells.

[0039] In such an embodiment, the step of heating the tobacco material to a temperature of 100 degrees Celsius to 160 degrees Celsius may be carried out solely by microwave heating.

[0040] Alternatively, and preferably, the step of heating the tobacco material to a temperature of 100°C to 160°C involves a combination of microwave heating and conventional heating, such as resistive heating or steam heating. In such methods, microwave heating is used in addition to a conventional heating step, and the tobacco material is simultaneously heated by microwaves and conventional heating means, such as resistive heating or steam. This combination of heating methods has been found to be particularly effective in increasing extraction yields (especially nicotine) because it appears to optimize the effects of microwave heating. Furthermore, by combining microwave heating with conventional heating in the main heating step, the heating step can advantageously be carried out significantly faster and with less energy, thus optimizing the efficiency of the extraction process. In certain methods, it may be easier to carry out certain heating steps using conventional heating means than using microwave heating alone, so retaining conventional heating in combination with microwave heating is useful. For example, if the tobacco material is heated in a flow of inert gas, the inert gas may need to be heated by resistive heating means.

[0041] Preferably, when a combination of heating methods is used, microwave heating preferably provides about 50 percent to about 90 percent of the heating power to heat the tobacco material to the desired extraction temperature.

[0042] Microwave heating of the tobacco material can be carried out using any suitable means for generating microwaves. One example of an apparatus suitable for microwave heating of tobacco material is the LABATRON™ ES3 Integrated Reactor and Microwave Transmission System by SAIREM, which can be used to carry out a microwave extraction process using a batch or continuous-flow microwave reactor. This apparatus is suitable for embodiments in which the tobacco material is heated simultaneously by microwaves and conventional heating, as described above.

[0043] Microwave power should be controlled to achieve the desired temperature of the tobacco material depending on the mass of the tobacco material being heated.

[0044] Preferably, the tobacco material is continuously circulated or agitated during microwave heating. This can be achieved, for example, by heating the tobacco material in a tumble dryer. Continuous circulation of the tobacco material avoids the formation of hot spots within the tobacco material, thereby improving heating uniformity so that extraction yield can be optimized.

[0045] Preferably, the moisture content of the tobacco material at the start of the microwave heating step is at least about 10 weight percent, more preferably at least about 20 weight percent. The moisture content of the tobacco material at the start of the microwave heating step can be up to about 70 weight percent, more preferably up to about 50 weight percent, more preferably up to about 40 weight percent, more preferably up to about 30 weight percent. For example, the moisture content of the tobacco material at the start of the microwave heating step can be between about 10 weight percent and about 70 weight percent, or between about 10 weight percent and about 50 weight percent, or between about 10 weight percent and about 40 weight percent, or between about 10 weight percent and about 20 weight percent.

[0046] Of course, the "moisture content in the tobacco material" can include both water inherently present in the tobacco material as well as any added water.

[0047] The presence of water in the tobacco material is important for optimizing the extraction effect of microwave heating, because the water molecules in the tobacco cells boil, causing the cells to rupture and release nicotine and other compounds. Therefore, the moisture content of the tobacco material is preferably maintained at a level of at least 10 weight percent. In particular, drying the tobacco material before microwave heating is not preferred, as the cell rupture mechanism has been found to operate more effectively without drying the tobacco material before microwave heating. Eliminating the drying step at this stage during the extraction process is advantageous because it reduces the time and energy required to prepare the tobacco material for extraction, thereby further improving the overall efficiency of the process compared to prior art extraction methods.

[0048] In certain embodiments, the method further comprises adding water to the tobacco material prior to the microwave heating step to increase the moisture content of the tobacco material, preferably to at least 10 weight percent. For example, the tobacco material may be sprayed with liquid water or contacted with steam to increase the moisture content prior to microwave heating.

[0049] In embodiments of the present invention in which the tobacco material is pretreated by microwave heating before the main heating step, as described above, the method according to the present invention further comprises adding water to the tobacco material after the microwave heating step and before the main heating step to increase the moisture content of the tobacco material, preferably to 10 weight percent. The microwave pretreatment step likely reduces the moisture content of the tobacco material due to evaporation of water from within the tobacco cells during heating. It is advantageous to restore the lost moisture from the tobacco material and return the moisture content to at least 10 weight percent so that the subsequent heating step to extract volatile compounds is optimized and any combustion of the tobacco material is avoided.

[0050] Optionally, in the method according to the present invention, moisture lost during the microwave pretreatment step can be captured by subjecting the off-gas produced during the pretreatment step to a condensation step, which can advantageously also capture valuable volatile components of the tobacco that may be lost during the pretreatment step. The collected water and volatile components can then be used in rehumidifying the pretreated tobacco, thereby rehumidifying the tobacco and reducing the potential loss of valuable volatile components.

[0051] As defined above, in the method of the present invention, tobacco material is heated under specific heating conditions to release volatile tobacco components, which are collected and formed into a liquid tobacco extract.

[0052] During the heating process, the tobacco material is heated to an extraction temperature of about 100° C. to about 160° C. Below this range, insufficient concentrations of nicotine and certain flavor compounds are released from the tobacco material, causing the resulting liquid tobacco extract to lack the desired flavor characteristics. On the other hand, if the tobacco material is heated to a temperature above this defined range, unacceptably high levels of certain undesirable tobacco compounds may be released.

[0053] Preferably, the extraction temperature is at least about 110 degrees Celsius, more preferably at least about 115 degrees Celsius, more preferably at least about 120 degrees Celsius, and more preferably at least 125 degrees Celsius.

[0054] Preferably, the extraction temperature is about 150 degrees Celsius or less, more preferably about 145 degrees Celsius or less, even more preferably about 140 degrees Celsius or less, and most preferably about 135 degrees Celsius or less.

[0055] For example, the extraction temperature may be from about 110° C. to about 150° C., or from about 120° C. to about 140° C., or from about 125° C. to about 135° C., or about 130° C. An extraction temperature of about 130° C. has been found to result in a particularly optimized ratio of desirable to undesirable compounds in the liquid tobacco extract.

[0056] The extraction temperature can be from about 110 degrees Celsius to about 130 degrees Celsius, or from about 115 degrees Celsius to about 125 degrees Celsius, or about 120 degrees Celsius.

[0057] The extraction temperature may be from about 125 degrees Celsius to about 155 degrees Celsius, more preferably from about 135 degrees Celsius to about 145 degrees Celsius, or about 140 degrees Celsius.

[0058] The tobacco material is heated at the extraction temperature for at least about 15 minutes, preferably at least about 20 minutes, more preferably at least about 25 minutes, more preferably at least about 30 minutes, more preferably at least about 40 minutes, more preferably at least about 50 minutes, and more preferably at least about 60 minutes. This extraction time is sufficiently long to efficiently extract the desired tobacco flavor compounds and provide a liquid tobacco extract capable of producing an aerosol having the desired flavor characteristics. As noted above, the inclusion of a microwave heating step in the extraction method of the present invention allows the heating step to be carried out relatively quickly, with heating durations that are much shorter than those typically required in prior art extraction processes.

[0059] Preferably, the tobacco material is heated at an extraction temperature for 180 minutes or less, more preferably for about 120 minutes or less.

[0060] For example, the heating time can be from about 15 minutes to about 180 minutes, or from about 15 minutes to about 120 minutes, or from about 20 minutes to about 180 minutes, or from about 20 minutes to about 120 minutes, or from about 25 minutes to about 180 minutes, or from about 25 minutes to about 120 minutes, or from about 30 minutes to about 180 minutes, or from about 30 minutes to about 120 minutes, or from about 40 minutes to about 180 minutes, or from about 40 minutes to about 120 minutes, or from about 50 minutes to about 180 minutes, or from about 50 minutes to about 120 minutes, or from about 60 minutes to about 180 minutes, or from about 60 minutes to about 120 minutes.

[0061] The heating times set forth above correspond to the duration of time that the tobacco material is heated at the extraction temperature, and do not include the time it takes to raise the temperature of the tobacco material to the extraction temperature.

[0062] The extraction temperature and heating time can be selected within the ranges defined above depending on factors such as the type of tobacco, other possible components of the tobacco material, the desired level of nicotine, or the desired composition of the liquid tobacco extract. By controlling the combination of extraction temperature and time, the composition of the liquid tobacco extract can be adjusted depending on the desired properties of the aerosol produced from the liquid tobacco extract. In particular, the proportion of specific tobacco compounds within the liquid tobacco extract can be adjusted to some extent through the selection of extraction parameters to maximize the ratio of desirable to undesirable tobacco compounds within the liquid tobacco extract.

[0063] For a particular tobacco compound, the variation in the release level of the compound with the extraction temperature during the extraction process can be easily determined for any given tobacco material. For example, it has been found that the level of nicotine released from tobacco materials typically increases with increasing extraction temperature. The rate of increase has been found to vary depending on the type of tobacco.

[0064] It has also been found that the levels of desirable tobacco flavor compounds, such as β-damascenone and β-ionone, released from tobacco materials increase as the extraction temperature increases up to a certain peak extraction temperature, after which the levels begin to decrease. The peak extraction temperature for such flavor compounds is typically within the range of 100° C. to 160° C., so that the extraction methods of the present invention can effectively optimize the levels of desirable flavor compounds.

[0065] Many undesirable tobacco compounds are found to increase slowly as the extraction temperature increases up to a threshold temperature, above which a rapid increase is observed. This applies, for example, to the levels of phenolic compounds, TSNAs, and pyrazines, and in the case of bright tobacco, to the levels of furans and formaldehyde. In many cases, the threshold temperature is within the range of 100°C to 160°C, and therefore, the levels of undesirable compounds can be effectively controlled in the extraction methods of the present invention.

[0066] Preferably, the extraction temperature and extraction time are selected to provide a nicotine content in the liquid tobacco extract of at least 0.1 weight percent, more preferably at least about 0.2 weight percent.

[0067] Preferably, the extraction temperature, or extraction time, or both the extraction temperature and extraction time, are selected to provide a weight ratio of (β-ionone+β-damascenone) to (phenol) in the liquid tobacco extract of at least about 0.25.

[0068] β-damascenone and β-ionone are desirable compounds associated with tobacco flavor. It has also been found that the amount of β-damascenone and β-ionone released from tobacco materials increases as the extraction temperature increases up to a certain peak extraction temperature, after which the levels begin to decrease. The peak extraction temperature for such flavor compounds is typically within the range of 100°C to 160°C, allowing the extraction method to effectively adjust and control the levels of the desired flavor compounds.

[0069] Preferably, the extraction temperature, or the extraction time, or both the extraction temperature and the extraction time, is at least about 5x10 -4 The compound is selected to provide a weight ratio of (Furaneol + (2,3-diethyl-5-methylpyrazine) * 100)) to (nicotine).

[0070] As mentioned above, the heating step can be carried out by conventional heating, microwave heating, or a combination of conventional and microwave heating.

[0071] Suitable heating methods for carrying out conventional heating of tobacco material are known to those skilled in the art and include, but are not limited to, dry distillation, steam distillation, vacuum distillation, flash distillation, and thin film steam distillation.

[0072] The heating step is preferably carried out in an inert atmosphere. A flow of inert gas, such as nitrogen, is preferably passed through the tobacco material during the heating step. In some cases, a combined flow of inert gas and water or steam may be used. The addition of water or steam to the tobacco during extraction has been found to increase the yield of extracted components. However, adding too much water or steam can lead to processing difficulties, such as stickiness of the tobacco material.

[0073] Volatile tobacco compounds are released into the inert gas stream during the heating process, so that the inert gas (or a combination of the inert gas and water or steam) acts as a carrier for the volatile components. The inert gas flow rate may be optimized based on the size and shape of the extraction chamber. A relatively high inert gas flow rate may advantageously improve the efficiency of extraction from the tobacco material.

[0074] Generally, when the tobacco material is heated, any moisture present in the tobacco material is released along with volatile compounds in the form of vapor.

[0075] The flow of inert gas serves to carry away vapors produced by evaporation of the moisture content of the tobacco material, and volatile compounds, including in particular nicotine and / or flavor-related compounds, from the extraction device. Furthermore, in methods in which the tobacco material is heated by microwave heating during this process, the flow of inert gas has been found to advantageously maintain humidity within the extraction chamber at a relatively low level, thereby maximizing microwave transmission through the tobacco material.

[0076] Furthermore, the use of a flow of inert gas (such as nitrogen) under a slight overpressure within the extraction equipment has the advantage of preventing the presence of oxygen within the extraction equipment. This is desirable in that it prevents the risk of even partial combustion of the tobacco material during the heating process. Uncontrolled combustion of the tobacco material would clearly be undesirable, as it would pose a major safety risk within the manufacturing environment. However, the inventors have found that even limited and partial combustion of the tobacco material may lead to a deterioration in the quality of the tobacco extract obtainable by the present method, which would be undesirable.

[0077] Without wishing to be bound by theory, it is understood that by preventing the combustion of the tobacco material, the formation of any undesirable combustion by-products is also prevented. Furthermore, when conditions that would promote the combustion of the tobacco material are prevented, the tobacco material is effectively heated under conditions that mimic, to some extent, the conditions under which tobacco-containing substrates (e.g., homogenized tobacco material) are typically heated in "heat-and-burn" articles. As a result, the selective extraction of flavorful volatile species responsible for the taste consumers associate with heated tobacco is advantageously supported.

[0078] Therefore, by carrying out the heating step in an inert atmosphere, extraction efficiency, product quality, and manufacturing safety are advantageously enhanced.

[0079] Heating the tobacco material in a stream of inert gas has the added benefit that the stream of inert gas containing the volatile compounds can be more easily directed into a vessel containing an extraction solvent, such as a non-aqueous extraction liquid solvent.

[0080] Optionally, the heating step may be carried out under vacuum, which removes any oxygen present in the extraction chamber, which may advantageously prevent the tobacco material or volatile compounds produced during heating from reacting with the oxygen. Removal of oxygen also prevents any combustion of the tobacco material, as discussed above.

[0081] The method according to the present invention may further comprise the step of spraying atomized water into the extraction chamber during the heating step. This has been found to improve heat exchange during the heating step, which is believed to be due to the turbulence generated in the extraction chamber as a result of the evaporation of the atomized water. As a result of the improved heat exchange, it has been found that including the step of spraying water into the extraction chamber during the heating step results in further improvements in nicotine yield and an increase in the yield of certain desirable flavor compounds from the tobacco material. When the heating step includes microwave heating, as described above, the presence of water also optimizes the effect of microwaves on the tobacco material.

[0082] The atomized water spray may be generated and dispensed into the brewing chamber using any suitable means.

[0083] The flow rate at which the atomized water is sprayed into the extraction chamber can be adjusted, for example, depending on the flow rate of the tobacco material in the extraction chamber. For example, the average flow rate at which the atomized water is sprayed into the extraction chamber can be about 3 percent to about 30 percent of the flow rate of the tobacco material.

[0084] Preferably, the atomized water is sprayed at a pressure of at least about 1 bar, more preferably at least about 2 bar, more preferably at least about 3 bar.

[0085] Methods for atomizing water will be known to those skilled in the art. In some embodiments, the water may be atomized with a stream of compressed inert gas, such as air. In other embodiments, the water may be atomized without a gas stream due to the pressure within the atomizing nozzle.

[0086] The liquid tobacco extract may be produced from a tobacco material consisting of a single type of natural tobacco. Alternatively, the tobacco material may contain a blend of two or more natural tobaccos. The ratio of different tobacco types may be adjusted depending on the desired characteristics of the aerosol produced from the liquid tobacco extract. For example, if it is desired to provide a relatively high level of nicotine, the proportion of burley tobacco may be increased.

[0087] The term "natural tobacco" is used herein in the context of the present invention to describe any part of any plant member of the genus Nicotiana, including, but not limited to, the leaves, midrib, stem, and petiole. In particular, natural tobacco may include flue-cured tobacco material, burley tobacco material, Orient tobacco material, Maryland tobacco material, dark tobacco material, dark flue-cured tobacco material, Rustica tobacco material, as well as other rare or specialty tobacco-derived materials, or blends thereof. As described in more detail below, the tobacco material may be whole (e.g., whole tobacco leaf), shredded, cut, or ground.

[0088] When it is desired to produce a liquid tobacco extract from a combination of two or more different types of tobacco, the tobacco types may be heated separately at different extraction temperatures within a defined range of 100°C to 160°C, or a mixture of tobacco types may be heated together at a single extraction temperature within that range.

[0089] The tobacco material may be a solid tobacco material such as a powder, leaf scraps or pieces, or intact leaves. Alternatively, the tobacco material may be a liquid tobacco material such as a dough, gel, slurry, or suspension.

[0090] The tobacco material may be derived from any suitable tobacco material, including, but not limited to, tobacco leaf, tobacco stem, reconstituted tobacco, cast tobacco, extruded tobacco, or tobacco-derived pellets.

[0091] In the process of preparing the tobacco material, the tobacco is preferably milled or chopped to reduce the size of the tobacco particles within the tobacco material, which may advantageously improve the uniformity of heating of the tobacco material and the efficiency of extraction.

[0092] The tobacco material may optionally be dried prior to the heating step to reduce the moisture content of the tobacco material. Drying of the tobacco material may be carried out by any suitable chemical or physical drying process. Alternatively, and preferably, water may be added to the tobacco material prior to the heating step to increase the moisture content of the tobacco material, particularly if microwave heating is used at this stage.

[0093] In certain embodiments of the present invention, the step of preparing a tobacco material may include impregnating the tobacco material with an aerosol former. If this impregnation of the tobacco material is performed before the heating step, it may advantageously increase the amount of certain desirable tobacco compounds released from the tobacco material upon heating. For example, impregnation of a tobacco material with glycerin has been found to advantageously increase the amount of nicotine extracted from the tobacco material. In another example, impregnation of a tobacco material with a non-aqueous extraction solvent that is also an aerosol former, such as propylene glycol, vegetal glycerin, 1,3-propanediol, triacetin, or a mixture thereof, has been found to advantageously increase the amount of flavor compounds extracted from the tobacco material.

[0094] In some embodiments, the tobacco material comprises natural tobacco that has not been subjected to any pre-treatment process, e.g., to adjust its moisture content. As such, the moisture content of the tobacco material may be about 10-20 weight percent (the moisture content typically found in natural tobacco materials). In other embodiments, the tobacco material may contain added water, as described above.

[0095] Alternatively or additionally, the tobacco material may include one or more additional components, such as, for example, a non-aqueous solvent. Examples of suitable solvents include propylene glycol.

[0096] Thus, the tobacco material may comprise at least about 40 weight percent natural tobacco material, or at least about 60 weight percent natural tobacco material, or at least about 80 weight percent natural tobacco material, or at least about 90 weight percent natural tobacco material, or at least about 95 weight percent natural tobacco material.

[0097] In some embodiments, the non-aqueous solvent content may be at least about 5 weight percent, or at least about 10 weight percent, or at least about 15 weight percent, or at least about 20 weight percent, or at least about 25 weight percent, or at least about 30 weight percent, or at least about 35 weight percent, or at least about 40 weight percent.

[0098] Optionally, the tobacco material may be enzymatically digested prior to the heating step, which has been found to provide a significant increase in the yield of certain flavor compounds from the tobacco material.

[0099] In certain embodiments, it is preferred that in the process of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to change the pH of the tobacco. In particular, in the process of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to significantly increase the pH of the tobacco.

[0100] In other embodiments, the method further comprises the step of subjecting the tobacco material to an alkaline treatment prior to the heating step. If the method comprises the pre-treatment step of microwave heating the tobacco material, the alkaline treatment is preferably carried out prior to microwave heating. During the alkaline treatment, an alkaline solution is preferably applied to the tobacco material to provide an alkalized tobacco material, which is then used for extraction.

[0101] It has been found that including an alkali treatment step prior to heating the tobacco material results in a further significant increase in the yield of nicotine obtained during extraction.

[0102] Preferably, the pH of the alkalized tobacco material is at least about 8.5, more preferably at least about 9.0, more preferably at least about 9.5. Preferably, the pH of the alkalized tobacco material is 11 or less.

[0103] "pH of alkalized tobacco material" refers to the pH of an aqueous suspension of alkalized tobacco material formed by suspending alkalized tobacco material in water at a ratio of 1:20. The pH of the suspension is measured after a 30-minute steeping period.

[0104] As described above, in the alkaline treatment step, an alkaline solution is applied to the tobacco material before heating. A suitable alkaline solution can be selected, for example, depending on the desired pH of the tobacco material. The alkaline solution is preferably an aqueous solution of an alkaline agent. A preferred example of an alkaline solution suitable for the alkaline treatment step is an aqueous solution of potassium carbonate. Other suitable alkaline solutions for use in the present invention include, but are not limited to, sodium hydroxide, sodium carbonate, and hydrogen peroxide.

[0105] The tobacco material may optionally be analyzed prior to the heating step to determine its composition, e.g., alkaloid and reducing sugar content. This information regarding composition may be usefully used to select an appropriate extraction temperature.

[0106] During heating of the tobacco material, volatile compounds are released from the tobacco material in gaseous form. The volatile compounds are collected using any suitable technique. As described above, when the tobacco material is heated in a flow of inert gas, the volatile compounds are collected from the flow of inert gas. Different collection methods will be known to those skilled in the art.

[0107] In certain preferred embodiments, the step of collecting the volatile compounds uses an absorption technique to trap the volatile compounds in a non-aqueous extraction liquid solvent. For example, an inert gas stream containing the volatile compounds may be directed into a container of the non-aqueous extraction liquid solvent. The non-aqueous extraction liquid solvent is preferably an aerosol former, such as triacetin, glycerin, 1,3-propanediol, propylene glycol, or a combination thereof. Using an aerosol former as the liquid solvent is potentially beneficial because it can be retained as a diluent in the final liquid tobacco extract. This means that an additional step to remove the non-aqueous extraction solvent is not necessarily required.

[0108] As used herein with respect to the present invention, the term "aerosol former" refers to a compound or mixture of compounds that, in use, facilitates the formation of an aerosol and preferably is substantially resistant to thermal decomposition at the operating temperature of the aerosol-generating article or device. Examples of suitable aerosol formers include polyhydric alcohols (such as propylene glycol, triethylene glycol, 1,3-propanediol, glycerin, etc.), esters of polyhydric alcohols (such as glycerol monoacetate, diacetate, or triacetate), and aliphatic esters of mono-, di-, or polycarboxylic acids (such as dimethyl dodecanedioate, dimethyl tetradecanedioate, etc.).

[0109] The non-aqueous liquid solvent is preferably kept at a temperature below 0 degrees Celsius to optimize the transfer of volatile compounds to the liquid solvent. The non-aqueous extraction solvent is preferably kept at a temperature above -10 degrees Celsius. Temperatures below these values ​​may result in undesirable freezing phenomena.

[0110] In an alternative preferred embodiment, the step of collecting the volatile compounds may be carried out using a condensation technique in which the volatile compounds are condensed and the condensate is collected. Condensation of the volatile compounds may be carried out using any suitable device, for example in a cooling column. Preferably, the resulting condensate is added to a liquid aerosol former, preferably propylene glycol.

[0111] The addition of a liquid aerosol former, particularly propylene glycol, during the collection process can advantageously prevent condensed volatile compounds from separating into two phases or forming an emulsion, as some tobacco components tend to do. Without intending to be bound by theory, the inventors have observed that the solubility of a tobacco component in the aqueous extract (i.e., the aqueous fraction of a naturally-occurring liquid tobacco extract) depends primarily on its polarity, concentration, and the pH of the aqueous extract (hydrolate), which can vary depending on the tobacco type. As a result, if the amount of aerosol former is insufficient, an oily layer tends to form on the surface of the naturally-occurring liquid tobacco extract. This oily material may aggregate at different locations in the collection and drying equipment where the third and further steps of the method are performed, respectively. The addition of a liquid aerosol former, such as propylene glycol, helps prevent the formation of such a layer and is advantageous for homogenizing the naturally-occurring liquid tobacco extract. This in turn helps to prevent the loss of desirable flavor-related compounds during the fourth (drying) step, during which such compounds may undesirably build up on equipment surfaces.

[0112] Furthermore, liquid aerosol formers advantageously serve to capture flavor-related compounds regardless of their polarity and volatility, and during any subsequent drying step, liquid aerosol formers advantageously serve to prevent loss of the most volatile fractions and selectively remove excess water from naturally-derived liquid tobacco extracts to obtain concentrated tobacco extracts.

[0113] The use of propylene glycol as an aerosol former in the collection process has the additional advantage that propylene glycol exerts antimicrobial activity by lowering the water activity of the aqueous solution. Thus, by adjusting the propylene glycol content in the liquid tobacco extract, it is possible to ensure that the extract is substantially free of microbial activity.

[0114] As a further alternative, the step of collecting the volatile compounds can be carried out using adsorption techniques in which the volatile compounds are adsorbed onto the surface of a solid adsorbent material, such as activated carbon, and the adsorbed compounds are then transferred into a liquid solvent.

[0115] In the methods of the present invention, the next step is to form a liquid tobacco extract from the collected volatile compounds. The nature of this step may depend on the collection method. "Collected volatile compounds" typically comprises a solution of tobacco-derived volatile compounds in a liquid solvent or carrier.

[0116] As described above, when volatile compounds are collected by absorption with a non-aqueous extraction solvent, the extraction method provides a liquid tobacco extract that may include greater than about 25 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract may include greater than about 30 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract, or greater than about 35 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0117] The liquid tobacco extract may comprise about 65 percent or less of a non-aqueous extraction solvent based on the weight of the liquid tobacco extract, hi some embodiments, the liquid tobacco extract may comprise 60 percent or less by weight of a non-aqueous extraction solvent based on the weight of the liquid tobacco extract, or 55 percent or less by weight of a non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0118] In some embodiments, the liquid tobacco extract may comprise from about 25 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 25 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 60 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 25 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0119] In other embodiments, the liquid tobacco extract may comprise from about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 60 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0120] In further embodiments, the liquid tobacco extract may comprise from about 35 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 35 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 60 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract may comprise from about 35 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 weight percent of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. Preferably, the non-aqueous extraction solvent is triacetin, glycerin, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0121] In a preferred embodiment, the weight ratio of (β-ionone + β-damascenone) to (phenol) in the liquid tobacco extract is at least about 0.25.

[0122] In a preferred embodiment, the weight ratio of (Furaneol + (2,3-diethyl-5-methylpyrazine)*100) to (nicotine) in the liquid tobacco extract is at least about 5x10 -4 is.

[0123] As noted above, when volatile compounds are collected by absorption in a liquid solvent, the step of forming a liquid tobacco extract preferably includes drying the solution of volatile compounds in the liquid solvent to concentrate the solution. This may be performed, for example, to reach a desired concentration of nicotine or flavor compounds. Drying may be performed using any suitable means, including, but not limited to, desiccation, molecular sieving, freeze-drying, phase separation, distillation, membrane permeation, controlled water crystallization and filtration, reverse hygroscopicity, ultracentrifugation, liquid chromatography, reverse osmosis, or chemical drying.

[0124] In a preferred embodiment, the solution of the volatile compound in the liquid solvent is concentrated by drying.

[0125] In other words, the solution of volatile compounds in the liquid solvent is heated to evaporate at least a portion of the water to obtain a concentrated tobacco extract. To this end, the solution of volatile compounds in the liquid solvent may be heated to a temperature and for a period of time such that the water content in the tobacco extract is reduced by at least about 60 percent.

[0126] The partially dried concentrated tobacco extract can be considered the primary product of the method of the present invention. The exhausted tobacco material, from which the majority of the volatile species and moisture content have been extracted upon heating in the second step, can be considered a by-product of the method. Such exhausted tobacco material can typically have a moisture content of about 1-5 weight percent, preferably about 2-3 weight percent.

[0127] In one embodiment, the solution of volatile compounds in the liquid solvent is heated under vacuum, preferably at a temperature of at least about 70°C. In another embodiment, the solution of volatile compounds in the liquid solvent is heated under airflow, preferably airflow having a relatively low humidity, at a temperature of at least about 35°C. Thus, a naturally-derived concentrated tobacco extract can be obtained by the method according to the present invention. One such naturally-derived concentrated tobacco extract typically contains less than about 20 weight percent water.

[0128] Alternatively, if the volatile compounds are collected by condensation, the step of forming the liquid tobacco extract may include adding the condensate to a liquid solvent, such as an aerosol former.

[0129] Optionally, the step of forming a liquid tobacco extract comprises a filtering step.

[0130] Optionally, the step of forming the liquid tobacco extract comprises a blending step in which extracts derived from different tobacco materials are combined.

[0131] Optionally, the step of forming the liquid tobacco extract includes adding one or more additives, such as an organic acid, to the solution of volatile compounds, although in many cases the liquid tobacco extract is suitable for use without additives.

[0132] The present invention further provides a liquid tobacco extract produced by the method according to the first aspect of the invention as described in detail above. As noted above, the method of the present invention advantageously produces a natural liquid tobacco extract having a highly desirable ratio of desirable tobacco compounds, such as nicotine and flavor compounds, to undesirable tobacco compounds.

[0133] Liquid tobacco extracts are particularly suitable for the production of nicotine compositions, such as liquid or gel nicotine compositions, for use in aerosol generating systems, in which the nicotine composition is typically heated within the aerosol generating device.

[0134] As used herein, the term "aerosol-generating device" refers to a device including a heater element that interacts with a nicotine composition incorporating a liquid tobacco extract, such as that obtained by the method according to the present invention, to produce an aerosol. During use, volatile compounds are released from the nicotine composition by heat transfer and are entrained in air drawn through the aerosol-generating device. As the released compounds cool, they condense to form an aerosol, which is inhaled by the consumer.

[0135] Upon heating of a nicotine composition comprising a liquid tobacco extract according to the present invention, an aerosol containing volatile compounds collected from the tobacco material during the extraction process is released. By controlling the composition of the liquid tobacco extract through control of the extraction parameters, it is possible to tailor the composition and characteristics of the resulting aerosol produced from the liquid tobacco extract and delivered to the consumer.

[0136] The nicotine composition may be a liquid tobacco extract resulting from an extraction process according to the present invention without the addition of further nicotine. The nicotine composition may be a liquid tobacco extract resulting from an extraction process according to the present invention without the addition of further flavour compounds. The nicotine composition may be a liquid tobacco extract resulting from an extraction process according to the present invention without the addition of further furaneol. The nicotine composition may be a liquid tobacco extract resulting from an extraction process according to the present invention without the addition of further solvents.

[0137] Alternatively, the liquid tobacco extract may be subjected to additional processing steps to form a nicotine composition, and even if subjected to such additional steps, the nicotine composition may be formed without the need to add additional nicotine or flavor compounds.

[0138] Preferably, the liquid tobacco extract may be concentrated in a drying process as described above to form a concentrated tobacco extract, which may be used to form a nicotine composition.

[0139] Preferably, the concentrated tobacco extract comprises between 8 percent and 15 percent water by weight, based on the weight of the concentrated tobacco extract.

[0140] The drying step provides a concentrated tobacco extract that may have a non-aqueous extractant content of about 65 to about 95 weight percent, preferably about 65 to 85 weight percent, and most preferably about 75 to 85 weight percent. The non-aqueous extractant is preferably triacetin, glycerin, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0141] The drying process provides a concentrated tobacco extract that may have a nicotine content of at least about 0.2 weight percent nicotine, preferably from about 0.5 weight percent to about 12 weight percent nicotine, and most preferably from about 2 weight percent to about 8 weight percent nicotine.

[0142] Preferably, an additional non-aqueous solvent may be added to the liquid tobacco extract or concentrated tobacco extract to form the nicotine composition.

[0143] The nicotine composition may be a liquid nicotine composition or a gel nicotine composition.

[0144] The nicotine composition may comprise at least about 10 weight percent liquid tobacco extract. Preferably, the nicotine composition comprises at least about 20 weight percent liquid tobacco extract. More preferably, the nicotine composition comprises at least about 30 weight percent liquid tobacco extract. In preferred embodiments, the nicotine composition comprises at least about 40 weight percent liquid tobacco extract, more preferably at least about 50 weight percent liquid tobacco extract, and even more preferably at least about 60 weight percent liquid tobacco extract. In particularly preferred embodiments, the nicotine composition comprises at least about 65 weight percent liquid tobacco extract, more preferably at least about 70 weight percent liquid tobacco extract, even more preferably at least about 75 weight percent liquid tobacco extract, and most preferably at least about 80 weight percent liquid tobacco extract.

[0145] In some embodiments, the liquid tobacco extract is a concentrated tobacco extract. The nicotine composition may comprise at least about 10 weight percent of concentrated tobacco extract, at least about 20 weight percent of concentrated tobacco extract, at least about 30 weight percent of concentrated tobacco extract, at least about 40 weight percent of concentrated tobacco extract, at least about 50 weight percent of concentrated tobacco extract, preferably at least about 60 weight percent of concentrated tobacco extract, more preferably at least about 70 weight percent of concentrated tobacco extract, even more preferably at least about 75 weight percent of concentrated tobacco extract, and most preferably at least about 80 weight percent of concentrated tobacco extract.

[0146] In some embodiments, the nicotine composition comprises from about 40 weight percent to about 95 weight percent liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 weight percent to about 95 weight percent liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 50 weight percent to about 95 weight percent liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 weight percent to about 95 weight percent liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 weight percent to about 95 weight percent liquid tobacco extract, and even more preferably from about 80 weight percent to about 95 weight percent liquid tobacco extract.

[0147] In some embodiments, the nicotine composition comprises from about 40 weight percent to about 90 weight percent liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 weight percent to about 90 weight percent liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 50 weight percent to about 90 weight percent liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 weight percent to about 90 weight percent liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 weight percent to about 90 weight percent liquid tobacco extract, and even more preferably, from about 80 weight percent to about 90 weight percent liquid tobacco extract.

[0148] In some embodiments, the nicotine composition comprises about 40 weight percent to about 85 weight percent liquid tobacco extract. More preferably, the nicotine composition comprises about 40 weight percent to about 85 weight percent liquid tobacco extract. Even more preferably, the nicotine composition comprises about 85 weight percent to about 90 weight percent liquid tobacco extract. Most preferably, the nicotine composition comprises about 60 weight percent to about 85 weight percent liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises about 70 weight percent to about 85 weight percent liquid tobacco extract, and even more preferably, about 80 weight percent to about 85 weight percent liquid tobacco extract.

[0149] The nicotine composition may comprise up to about 100 weight percent liquid tobacco extract. In some embodiments, the nicotine composition may be formed directly from the liquid tobacco extract without the need for the addition of additional non-aqueous solvents, flavorings, or nicotine. That is, the nicotine composition may comprise 100 weight percent liquid tobacco extract. In some embodiments, the liquid tobacco extract is a concentrated tobacco extract, and the nicotine composition may comprise 100 weight percent concentrated tobacco extract. In embodiments in which the nicotine composition comprises 100 weight percent liquid tobacco extract or 100 weight percent concentrated tobacco extract, no additional non-aqueous solvent is present.

[0150] Alternatively, in some embodiments, the nicotine composition comprising the liquid tobacco extract may include an additional non-aqueous solvent. The additional non-aqueous solvent is a non-aqueous solvent added after the extraction process. The additional non-aqueous solvent is a solvent that supplements the non-aqueous extraction solvent present in the liquid tobacco extract. In embodiments where the liquid tobacco extract is a concentrated tobacco extract, the nicotine composition comprising the concentrated tobacco extract may include an additional non-aqueous solvent.

[0151] The additional non-aqueous solvent may be an aerosol former. Preferably, the additional non-aqueous solvent is triacetin, glycerin, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0152] In embodiments in which the nicotine composition includes an additional non-aqueous solvent, the nicotine composition may include 90 weight percent or less of the additional non-aqueous solvent. Preferably, the nicotine composition includes 80 weight percent or less of the additional non-aqueous solvent. More preferably, the nicotine composition includes 70 weight percent or less of the additional non-aqueous solvent. In preferred embodiments, the nicotine composition includes about 60 weight percent or less of the additional non-aqueous solvent, more preferably about 50 weight percent or less of the additional non-aqueous solvent, and even more preferably about 40 weight percent or less of the additional non-aqueous solvent. In particularly preferred embodiments, the nicotine composition includes about 35 weight percent or less of the additional non-aqueous solvent, more preferably about 30 weight percent or less of the additional non-aqueous solvent, even more preferably about 25 weight percent or less of the additional non-aqueous solvent, and most preferably about 20 weight percent or less of the liquid tobacco extract.

[0153] In nicotine compositions prepared by means of the method according to the present invention, at least 50 weight percent of the nicotine content in the nicotine composition, based on the total weight of the nicotine composition, can be obtained from tobacco extract rather than being added after extraction. In a preferred embodiment, at least 80 weight percent of the nicotine content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from tobacco extract rather than being added after extraction. Even more preferably, at least 90 weight percent of the nicotine content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from tobacco extract rather than being added after extraction.

[0154] In nicotine compositions prepared by means of the method according to the present invention, at least 50 weight percent of the non-aqueous extractant content in the nicotine composition, based on the total weight of the nicotine composition, can be obtained from the tobacco extract rather than being added after extraction. In a preferred embodiment, at least 80 weight percent of the non-aqueous extractant content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from the tobacco extract rather than being added after extraction. Even more preferably, at least 90 weight percent of the non-aqueous extractant content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from the tobacco extract rather than being added after extraction.

[0155] In nicotine compositions prepared by means of the method according to the present invention, at least 50 weight percent of the water content in the nicotine composition, based on the total weight of the nicotine composition, can be obtained from the tobacco extract rather than being added after extraction. In a preferred embodiment, at least 80 weight percent of the water content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from the tobacco extract rather than being added after extraction. Even more preferably, at least 90 weight percent of the water content in the nicotine composition, based on the total weight of the nicotine composition, is derived from the tobacco extract rather than being added after extraction.

[0156] In nicotine compositions prepared by means of the method according to the present invention, at least 50 weight percent of the desired tobacco flavor species content in the nicotine composition, based on the total weight of the nicotine composition, can be obtained from the tobacco extract rather than being added after extraction. In a preferred embodiment, at least 80 weight percent of the desired flavor species content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from the tobacco extract rather than being added after extraction. Even more preferably, at least 90 weight percent of the desired flavor species content in the nicotine composition, based on the total weight of the nicotine composition, is obtained from the tobacco extract rather than being added after extraction.

[0157] The total content of non-aqueous solvents in the nicotine composition includes the non-aqueous extraction solvent and, if present, additional non-aqueous solvents. The nicotine composition may contain a total content of non-aqueous solvents of about 10 weight percent to about 95 weight percent. The nicotine composition preferably contains a total content of non-aqueous solvents of about 50 weight percent to about 95 weight percent, e.g., about 65 weight percent to about 95 weight percent, more preferably about 70 weight percent to about 90 weight percent, and most preferably about 80 weight percent to about 90 weight percent. The non-aqueous solvent is preferably triacetin, glycerin, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0158] The nicotine composition may comprise a total propylene glycol content of about 10 weight percent to about 95 weight percent. The nicotine composition may comprise a total propylene glycol content of about 20 weight percent to about 95 weight percent, e.g., about 50 weight percent to about 95 weight percent, or about 65 weight percent to about 95 weight percent, about 70 weight percent to about 90 weight percent, or about 80 weight percent to about 90 weight percent.

[0159] The nicotine composition may comprise a total triacetin content of about 10 weight percent to about 95 weight percent, e.g., about 20 weight percent to about 95 weight percent, e.g., about 50 weight percent to about 95 weight percent, about 70 weight percent to about 90 weight percent, or about 65 weight percent to about 95 weight percent, or about 80 weight percent to about 90 weight percent.

[0160] The nicotine composition may comprise a total glycerin content of about 10 weight percent to about 95 weight percent. The nicotine composition may comprise a total glycerin content of about 20 weight percent to about 95 weight percent, e.g., about 50 weight percent to about 95 weight percent, or about 65 weight percent to about 95 weight percent, about 70 weight percent to about 90 weight percent, or about 80 weight percent to about 90 weight percent.

[0161] The nicotine composition may comprise a total 1,3-propanediol content of about 10 weight percent to about 95 weight percent. The nicotine composition may comprise a total 1,3-propanediol content of about 20 weight percent to about 95 weight percent, e.g., about 50 weight percent to about 95 weight percent, or about 65 weight percent to about 95 weight percent, or about 80 weight percent to about 90 weight percent.

[0162] The nicotine composition of the present invention contains at least 0.2 weight percent nicotine. More preferably, the nicotine content of the nicotine composition liquid tobacco extract is at least about 0.4 weight percent. The nicotine composition may have a nicotine content of about 12 weight percent or less, for example, about 10 weight percent or less, preferably about 8 weight percent or less, more preferably about 5 weight percent or less, and preferably about 3.6 weight percent or less. Most preferably, the nicotine composition contains about 0.4 weight percent to 3.6 weight percent nicotine, based on the weight of the nicotine composition.

[0163] The nicotine composition may comprise from 1 weight percent to 85 weight percent water. The nicotine composition may comprise from 2 weight percent to 50 weight percent water. The nicotine composition may comprise from 3 weight percent to 30 weight percent water. The nicotine composition may comprise from 5 weight percent to 25 weight percent water. The nicotine composition may comprise from 8 weight percent to 20 weight percent water. The nicotine composition preferably comprises from 10 weight percent to 15 weight percent water.

[0164] In some embodiments, the nicotine composition may include one or more water-soluble organic acids. As used herein in connection with the present invention, the term "water-soluble organic acid" refers to an organic acid having a water solubility of about 500 mg / ml or greater at 20°C.

[0165] One or more water-soluble organic acids can advantageously bind to nicotine in the liquid tobacco extract through the formation of one or more nicotine salts. The one or more nicotine salts can advantageously be dissolved and stabilized in water present in the liquid tobacco extract or in the non-aqueous solvent. This can advantageously reduce nicotine adsorption in the upper respiratory tract and enhance nicotine delivery and retention in the lungs, as discussed above.

[0166] Preferably, the nicotine composition contains water-soluble organic acids at about 2 weight percent or greater. More preferably, the nicotine composition contains water-soluble organic acids at about 3 weight percent or greater.

[0167] The water-soluble organic acid may be acetic acid.

[0168] Exogenous acetic acid is acetic acid that has been added from a source other than the tobacco plant material, and is not acetic acid that is naturally present in the tobacco plant that has been separated, removed, or derived from the tobacco plant material using extraction processing conditions and techniques.

[0169] When acetic acid is added to a liquid tobacco extract to form a nicotine composition, the total content of acetic acid in the nicotine composition, including both exogenous and endogenous acetic acid, is preferably about 0.01 weight percent to about 8 weight percent, e.g., about 0.03 weight percent to about 8 weight percent, about 0.3 weight percent to about 8 weight percent, about 2 weight percent to about 8 weight percent, or about 3 weight percent to about 8 weight percent. More preferably, the total content of acetic acid is about 0.01 weight percent to about 6 weight percent, e.g., about 0.03 weight percent to about 6 weight percent, about 0.3 weight percent to about 6 weight percent, about 2 weight percent to about 6 weight percent, or about 3 weight percent to about 6 weight percent.

[0170] Preferably, the nicotine composition contains no more than about 8 weight percent water-soluble organic acids. More preferably, the nicotine composition contains no more than about 6 weight percent water-soluble organic acids.

[0171] Preferably, the water-soluble organic acid content of the nicotine composition is about 2 weight percent to about 8 weight percent. For example, the water-soluble organic acid content of the nicotine composition may be about 2 weight percent to about 6 weight percent.

[0172] More preferably, the water-soluble organic acid content of the nicotine composition is about 3 weight percent to about 8 weight percent. For example, the water-soluble organic acid content of the nicotine composition may be about 3 weight percent to about 6 weight percent.

[0173] The nicotine composition may include one or more non-tobacco derived flavorants. Suitable non-tobacco derived flavorants include, but are not limited to, menthol.

[0174] Preferably, the nicotine composition has about 4 weight percent or less of non-tobacco-derived flavorants. More preferably, the nicotine composition has about 3 weight percent or less of non-tobacco-derived flavorants. For example, the liquid tobacco extract produced by the methods of the present invention can be used to make a nicotine composition containing 10-20 mg of nicotine per milliliter without the need for added nicotine.

[0175] A nicotine composition suitable for use in an aerosol-generating system may comprise a liquid tobacco extract produced by a method according to the present invention in combination with water and additional aerosol formers. The nicotine composition may comprise, for example, about 10 percent to about 20 percent water by weight.

[0176] The nicotine composition comprising a liquid tobacco extract according to the present invention may be provided in a cartridge for use in an aerosol generation system. The cartridge may include an atomizer configured to generate an aerosol from the nicotine composition. The atomizer may be a thermal atomizer configured to heat the nicotine composition to generate the aerosol. The thermal atomizer may include, for example, a heater and a liquid transport element configured to transport the nicotine composition to the heater. The liquid transport element may include a capillary wick. Alternatively, the atomizer may be a non-thermal atomizer configured to generate an aerosol from the nicotine composition by means other than heating. The non-thermal atomizer may be, for example, an impingement jet atomizer, an ultrasonic atomizer, or a vibrating mesh atomizer.

[0177] The cartridges containing the nicotine compositions formed from the liquid tobacco extracts of the present invention may be used in conjunction with any suitable aerosol-generating device that includes a housing configured to receive at least a portion of the cartridge, and may include a battery and control electronics.

[0178] Specific embodiments of the present invention will now be described further, by way of example only.

[0179] In a first embodiment of the extraction method, a tobacco material is prepared from flue-cured bright tobacco material. The tobacco material is cut to form shredded tobacco having a maximum dimension of 2.5 mm x 2.5 mm, and the shredded tobacco is pretreated by microwave heating until the tobacco cells rupture. The pretreated shredded tobacco is cooled and then placed in a humidity chamber to increase the moisture content to approximately 10 weight percent. The shredded tobacco is then fed, without compression, into an extraction chamber at a tobacco flow rate of 30 kg per hour. The tobacco material is heated to a temperature of 130°C in the extraction chamber for two hours. During heating, a stream of nitrogen passes through the extraction chamber at a flow rate of approximately 20 liters per minute.

[0180] Volatile compounds released from the tobacco material during the heating process are condensed and collected at 0 degrees Celsius and added to a liquid solvent formed from polypropylene glycol.

[0181] The propylene glycol solution with the collected volatile compounds is concentrated in a drying process to reduce the moisture level of the liquid tobacco extract to about 15 percent.

[0182] In a second embodiment of the extraction method, a tobacco material is prepared from flue-cured bright tobacco material. The tobacco material is cut to form shredded tobacco having dimensions of 2.5 mm x 2.5 mm, and water is added to the tobacco material to increase the moisture content to approximately 20 weight percent. The shredded tobacco is loaded into an extraction chamber without compression. The tobacco material is heated to a temperature of 130°C in the extraction chamber for 30 minutes. Heating is achieved by a combination of microwave heating and resistive heating, with the microwave heating providing at least 50 percent of the power used to heat the tobacco material. During heating, a stream of nitrogen is passed through the extraction chamber at a flow rate of approximately 40 liters per minute.

[0183] Volatile compounds released from the tobacco material during the heating process are condensed and collected at 0 degrees Celsius and added to a liquid solvent formed from polypropylene glycol. The propylene glycol solution with the collected volatile compounds is concentrated in a drying process to reduce the moisture level of the liquid tobacco extract to approximately 15 percent.

Claims

1. 1. A method for producing a liquid tobacco extract, comprising: preparing a tobacco material; heating the tobacco material at an extraction temperature of 100 degrees Celsius to 160 degrees Celsius for at least 15 minutes, wherein the tobacco material is directly heated; collecting volatile compounds released from the tobacco material during the heating step; and forming a liquid tobacco extract containing the collected volatile compounds; A method wherein the tobacco material is microwave heated during at least one step of the method.

2. 10. The method of claim 1, wherein the step of preparing the tobacco material comprises pretreating the tobacco material with microwave heating to rupture the tobacco cells prior to the heating step.

3. 3. The method of claim 2, wherein said step of heating said tobacco material to an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius is carried out by conventional heating.

4. 4. The method of any of claims 1 to 3, wherein the step of heating the tobacco material to an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius comprises microwave heating the tobacco material.

5. 5. The method of claim 4, wherein said step of heating said tobacco material to an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius comprises heating said tobacco material by a combination of microwave heating and conventional heating.

6. The method of any of claims 1 to 5, wherein the tobacco material, if present, is heated in a flow of inert gas during at least one of the heating and pre-treatment steps.

7. The method of any of claims 1 to 6, wherein the tobacco material has a moisture content of at least 10 percent by weight at the start of the microwave heating.

8. 8. The method of any of claims 1 to 7, further comprising the step of adding water to the tobacco material prior to the microwave heating step to increase the moisture content of the tobacco material to at least 10 weight percent.

9. The method of any preceding claim, wherein the tobacco material is continuously circulated during the microwave heating.

10. The method of any of claims 1 to 9, wherein the tobacco material is heated to an extraction temperature of between 125 degrees Celsius and 160 degrees Celsius.

11. 11. The method of any of claims 1-10, wherein the extraction temperature is selected to provide a liquid tobacco extract having a nicotine content of at least 0.2 weight percent on a dry weight basis.

12. The method of any of claims 1 to 11, further comprising the step of subjecting the tobacco material, if present, to an alkaline treatment prior to the heating step and prior to the pre-treatment step.

13. 13. The method of any of claims 1 to 12, further comprising the step of spraying atomized water onto the tobacco material during the heating step.

14. The method of any of claims 1 to 13, further comprising the step of drying or concentrating the collected volatile compounds.

15. A liquid tobacco extract produced by the method of any one of claims 1 to 14.