Improved process for producing liquid tobacco extract

Abstract

A method of producing a liquid tobacco extract includes the steps of preparing a tobacco material; heating the tobacco material in an extraction chamber at an extraction temperature between 120 degrees Celsius and 160 degrees Celsius for at least 90 minutes; collecting volatile compounds released from the tobacco material during the heating step; and forming a liquid tobacco extract including the collected volatile compounds. The method further includes the step of spraying atomized water into the extraction chamber during the heating step.

Description

[0001] The present invention relates to a method of producing a liquid tobacco extract and a liquid tobacco extract produced by such a method.

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

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

[0004] So-called "cold steeping methods" are also known in which the tobacco material is kept suspended in the extraction liquid for a period of several weeks or even months. The liquid phase thus collected can be used to make a vaporisable liquid formulation. In one such method, there is generally no way to control the extraction conditions (e.g. temperature and pressure). In a variation of the steeping method, which has been described in, for example, US 2012 / 192880, the slurry is heated to a temperature of 100 degrees Celsius or higher.

[0005] The liquid phase collected upon filtration of the slurry, which represents the main product of the steeping process, is highly diluted and tends to have a low content of non-polar tobacco flavour species. In addition, the liquid phase is generally almost free or free of nicotine. Therefore, the liquid extract obtained by the steeping method generally needs to be supplemented with additional ingredients, such as nicotine salts and glycerol, before use in a vaporisable liquid formulation.

[0006] An alternative method is known in which the tobacco material is brought to essentially boil in water for a period of several hours or even days to form a vapour phase, and the distillate obtained by condensation of the vapour phase is continuously collected in a container. Over time, an oily waxy layer containing a high proportion of non-polar compounds accumulates on the surface of the distillate.

[0007] On the other hand, the upper accumulated wax layer and the aqueous portion containing nicotine and other water-soluble compounds are recycled to the boiler. Optionally, a non-polar co-solvent can be fed to the boiler along with the aqueous portion to increase the extraction yield. On the other hand, the wax phase is collected and ultimately forms one of the main products of such a hydrodistillation process. Such a product is often referred to as "tobacco absolute" and contains a high proportion of non-polar compounds found in tobacco, such as fatty acids, neophytadienes, etc. The tobacco absolute obtained by one such process typically does not contain nicotine.

[0008] It is also known to subject tobacco material to an extraction process involving the use of a volatile, non-polar solvent. Examples of suitable solvents are cyclic or acyclic short alkanes, as well as 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 trace amounts of extraction solvent can be detected.

[0009] The main product of one such solvent-assisted extraction process is often referred to as "tobacco absolute" and can contain trace amounts of ethanol. It is a waxy product and contains a highly concentrated mixture of most of the non-polar compounds extractable with the particular solvent, often including nicotine, which is typically present in relatively high concentrations.

[0010] An alternative extraction process involves contacting the tobacco material with a solvent under supercritical conditions, such as supercritical carbon dioxide. One such process is disclosed in US 2013 / 160777 and relies on the principle that volatile substances within the feed material in contact with the supercritical fluid can partition into the supercritical phase. After dissolution of any soluble material, 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 main product of a supercritical extraction process is essentially similar to the "tobacco absolute" of a solvent-assisted extraction process run at lower temperatures and pressures, free of residual solvent, typically having high levels of waxy, non-polar compounds and including nicotine, which is typically present in relatively high concentrations.

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

[0012] Generally, liquid tobacco extracts obtained by such known extraction processes can have low levels of nicotine. Furthermore, liquid tobacco extracts obtained by such extraction processes can have low levels of flavour species and low flavour species diversity. Liquid tobacco extracts obtained by such extraction processes can also have high levels of undesirable compounds. Typically, the concentrations of nicotine, flavour species and undesirable compounds obtained by such extraction processes can be significantly influenced by the type(s) of tobacco used as starting material.

[0013] It is an object of the present invention to alleviate one or more of the drawbacks of liquid tobacco extracts obtained by known processes. In particular, it is desirable to provide a method for producing a novel and improved liquid tobacco extract. It would be especially desirable to provide such a method for producing such a liquid tobacco extract which can be carried out more efficiently than existing processes.

[0014] The present disclosure relates to a method for producing a liquid tobacco extract from a tobacco material. The method can comprise the step of preparing the tobacco material. The tobacco material can be heated in an extraction chamber at an extraction temperature of between about 120 degrees Celsius and about 160 degrees Celsius. The heating can be carried out for at least 90 minutes. The method can further comprise the step of collecting volatile compounds released from the tobacco material during the heating step. The method can further comprise the step of forming a liquid tobacco extract comprising the collected volatile compounds. The method can further comprise the step of spraying atomised water into the extraction chamber during the heating step.

[0015] According to the present invention, there is provided a method of producing a liquid tobacco extract, the method comprising the steps of: preparing a tobacco material; heating the tobacco material in an extraction chamber at an extraction temperature of between about 120 degrees Celsius and about 160 degrees Celsius for at least about 90 minutes; collecting volatile compounds released from the tobacco material during the heating step; and forming a liquid tobacco extract comprising the collected volatile compounds. According to the present invention, the method further comprises the step of spraying atomised water into the extraction chamber during the heating step.

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

[0017] As used herein in connection with the present application, the term "liquid tobacco extract" describes the direct product of an extraction process performed on a tobacco material. Thus, a tobacco extract generally comprises a mixture of natural components isolated, removed 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 application, the extraction process used to produce the liquid tobacco extract comprises heating the tobacco material under specific heating conditions and collecting the generated volatile compounds. The liquid tobacco extract thus consists of a mixture of natural tobacco components derived from the tobacco material and extracted or formed during the extraction process, generally in combination with one or more materials that are not tobacco materials, for example in combination with a non-aqueous extraction solvent used during the extraction process. As will be described in greater detail below, the volatile compounds released from the starting tobacco material can be collected using absorption techniques, wherein the volatile compounds are trapped in the non-aqueous extraction solvent. For example, a stream of inert gas containing the volatile compounds can be directed into a container of the non-aqueous extraction solvent. The non-aqueous extraction solvent is preferably an aerosol former.

[0018] As used herein in connection with the present application, the term "atomized water" refers to water that has been reduced to a plurality of small droplets. Thus, the atomized water is in an aerosol form, wherein a plurality of water droplets are suspended in air or another gas. In connection with the method of the present application, the term "spraying" refers to the step of expelling a flow or stream of atomized water into the extraction chamber at or above atmospheric pressure.

[0019] Thus, the method of the present application provides a novel heating step, wherein atomized water is sprayed into the extraction chamber during the step of heating the tobacco material to extract volatile compounds. In prior art extraction processes, the tobacco material is generally dried prior to the heating step, as this was believed to provide a more concentrated extract that requires less drying. However, the inventors of the present application have surprisingly found that the inclusion of the water spraying step defined above actually provides a significant improvement in the extraction yield of certain components, far exceeding any dilution effect.

[0020] In particular, it has been unexpectedly found that the inclusion of the water spraying step very significantly increases the yield of nicotine and other flavour compounds during extraction. For example, it has been found that in certain cases, the inclusion of the water spraying step can increase the extraction yield of nicotine by up to 130% compared to an equivalent extraction performed without the water spraying.

[0021] It has been found that this improvement in extraction yield is specifically related to the use of an atomised water spray. As demonstrated in the comparative examples below, when water is applied directly to the tobacco material prior to the heating step, or when water or steam is added to the extraction chamber without atomisation, the same improvement in nicotine yield is not observed. Without wishing to be bound by theory, it is believed that the improvement in extraction yield is due to the turbulent gas flow established in the extraction chamber as a result of the evaporation of the droplets in the atomised water spray, which results in improved heat exchange. In particular, the high gas velocities generated at a microscopic level during the expansion of the water droplets from the atomised water into the gas phase are believed to strongly influence the behaviour at the tobacco surface and drive an increase in mass transfer of volatile compounds such as nicotine. This enables nicotine and certain other volatile compounds to be extracted from the tobacco material more efficiently, thereby resulting in an improved extraction yield.

[0022] The equipment required to carry out the water spraying step is readily available and can be incorporated into existing extraction equipment without significant modification.

[0023] In addition to providing an improved nicotine yield, the extraction method of the present application uses an extraction temperature within a specific range in combination with a well-defined heating duration, which advantageously provides an improved liquid tobacco extract with a significantly improved balance of desirable compounds to undesirable compounds. In particular, the extraction method of the present application provides a liquid tobacco extract having a maximum ratio of desirable compounds to undesirable compounds for the tobacco material. For example, the use of specific combinations of extraction temperature and time as defined enables the level of nicotine compounds to be optimised, whilst also minimising the level of undesirable compounds such as furans, carbonyl compounds, phenols and TSNA.

[0024] The inventors of the present application have found that the method according to the present application advantageously provides a liquid tobacco extract having a significantly higher content of compounds associated with the flavour of heated tobacco, such as dimethylhydroxyfurfural, compared to the existing extraction processes discussed above. In tobacco extracts obtained by infusion processes, these compounds are essentially absent or present in trace amounts, and the extracts are also typically almost free or free of nicotine. In tobacco extracts obtained using solvents, including those obtained under supercritical conditions, these compounds are also typically absent or present in trace amounts. Similarly, tobacco essences obtained by distillation processes also typically have very low, if any, content of such compounds associated with the flavour of heated tobacco.

[0025] The liquid tobacco extract obtained by the process according to the present application exhibits significant compositional differences relative to tobacco extracts obtained by prior extraction processes and can be used as an e-liquid or for the preparation of an e-liquid which, when heated, generates an aerosol having different compositional and flavour characteristics to currently available e-liquids. In particular, the liquid tobacco extract obtained by the process according to the present application can be used to generate an aerosol which provides the taste of heated tobacco which more closely resembles the aerosol generated by conventional cigarettes or when tobacco is heated in a heat-not-burn device than the available aerosols produced from prior liquid nicotine compositions.

[0026] The extraction process of the present application enables the production of a liquid tobacco extract having optimised levels of nicotine and flavour compounds without the need to add such compounds after extraction. Thus, the resulting liquid tobacco extract can be used directly to provide a nicotine composition. The resulting liquid tobacco extract can also be modified by one or more further processing steps or mixed with one or more further ingredients to form a nicotine composition. The nicotine composition can be used in an e-cigarette or other aerosol generating system.

[0027] As noted above, aerosol-generating systems for delivering an aerosol to a user are known, the systems including an atomiser configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine composition.

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

[0029] In some cases, the tobacco material can be heated without the need for significant pre-treatment steps. Thus, the process can be effectively carried out.

[0030] As defined above, in the process of the present application, the tobacco material is heated under specific heating conditions to release volatile tobacco components which are collected and form a liquid tobacco extract.

[0031] During the heating step, the tobacco material is heated to an extraction temperature of between about 120 degrees Celsius and about 160 degrees Celsius. It has been found that below this range, the levels of nicotine and certain flavour compounds released from the tobacco material are insufficient, such that the resulting liquid tobacco extract lacks the desired flavour characteristics. On the other hand, if the tobacco material is heated to a temperature above this defined range, then unacceptably high levels of certain undesirable tobacco compounds can be released.

[0032] Preferably, the extraction temperature is at least about 125 degrees Celsius, more preferably at least about 130 degrees Celsius.

[0033] Preferably, the extraction temperature is no more than about 155 degrees Celsius, more preferably no more than about 150 degrees Celsius.

[0034] For example, the extraction temperature can be between about 125 degrees Celsius and 155 degrees Celsius, or between about 130 degrees Celsius and about 150 degrees Celsius. It has been found that an extraction temperature of approximately 150 degrees Celsius provides a particularly optimised ratio of desirable compounds to undesirable compounds in the liquid tobacco extract.

[0035] The tobacco starting material is heated at the extraction temperature for at least about 90 minutes, more preferably at least about 120 minutes. This extraction time is long enough to enable effective extraction of the desirable tobacco flavour compounds to provide a liquid tobacco extract that can produce an aerosol having the desired flavour characteristics.

[0036] Preferably, the tobacco starting material is heated at the extraction temperature for no more than about 270 minutes, more preferably no more than about 180 minutes.

[0037] For example, the tobacco starting material can be heated for between about 90 minutes and about 270 minutes, or between about 120 minutes and about 180 minutes.

[0038] The heating times described above correspond to the duration of heating of the tobacco material at the extraction temperature, and do not include the time taken to raise the temperature of the tobacco material to the extraction temperature.

[0039] The extraction temperature and heating duration can be selected within the ranges defined above, depending on factors such as the type of tobacco, possible other 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 characteristics of the aerosol generated from the liquid tobacco extract. In particular, the proportions of particular tobacco compounds within the liquid tobacco extract can be adjusted to some extent by selection of the extraction parameters to maximise the ratio of desirable tobacco compounds to undesirable tobacco compounds within the liquid tobacco extract.

[0040] For particular tobacco compounds, the level of release of the compound during the extraction process can be readily determined for any given tobacco material as a function of the extraction temperature. For example, it has been found that the level of nicotine released from tobacco material will generally increase as the extraction temperature is increased. The rate of increase has been found to differ for different tobacco types.

[0041] It has also been found that the levels of desirable tobacco flavour compounds released from the tobacco material, such as beta-damascenone and beta-ionone, will increase with increasing extraction temperature until a certain peak extraction temperature is reached, after which the levels will start to decrease. The peak extraction temperature for such flavour compounds is typically in the range of 120 to 160 degrees Celsius, such that the levels of desirable flavour compounds can effectively be optimised in the extraction process of the present application.

[0042] It has been found that many undesirable tobacco compounds slowly increase with increasing extraction temperature until a threshold temperature is reached, beyond which a rapid increase is observed. This applies to the levels of, for example, phenolic compounds, TSNA's and pyrazines, and in the case of light tobacco to the levels of furans and formaldehyde. In many cases, the threshold temperature is in the range of 120 to 160 degrees Celsius, and thus, the levels of undesirable compounds can effectively be controlled in the extraction process of the present application.

[0043] Preferably, the extraction temperature and extraction time are selected to provide a nicotine content of at least 0.1 wt.%, more preferably at least about 0.2 wt.% in the liquid tobacco extract.

[0044] Preferably, the extraction temperature or extraction time or both the extraction temperature and extraction time are selected to provide a weight ratio of (beta-ionone + beta-damascenone) to (phenol) of at least about 0.25 in the liquid tobacco extract.

[0045] Beta-damascenone and beta-ionone are desirable compounds associated with tobacco flavour. It has been found that the amount of beta-damascenone and beta-ionone released from the tobacco material will increase with increasing extraction temperature until a certain peak extraction temperature is reached, after which the levels will start to decrease. The peak extraction temperature for such flavour compounds is typically in the range of 120 to 160 degrees Celsius, such that the levels of desirable flavour compounds can effectively be tailored and controlled in the extraction process.

[0046] Preferably, the extraction temperature or extraction time or both the extraction temperature and extraction time are selected to provide a weight ratio of (dimethylhydroxyfuranone + (2,3-diethyl-5-methylpyrazine) * 100) to (nicotine) of at least about 5 x 10 -4 in the liquid tobacco extract.

[0047] It has been found that in the process according to the present application in which the extraction temperature is selected to provide a ratio in the above-mentioned range, particularly good organoleptic properties can be obtained when a nicotine composition prepared from the liquid tobacco extract is heated to generate an aerosol.

[0048] Suitable heating methods for carrying out heating of the tobacco material will be known to the skilled person and include, but are not limited to: dry distillation, water distillation, vacuum distillation, flash distillation and thin film water distillation.

[0049] As mentioned above, according to the present application, atomised water is sprayed into the extraction chamber during the heating step. Preferably, the atomised water is sprayed into the extraction chamber to create a turbulent gas flow within the extraction chamber.

[0050] Preferably, spraying is commenced once a desired extraction temperature within a defined range of 120 degrees Celsius to 160 degrees Celsius has been reached within the extraction chamber.

[0051] The atomised water spray can be generated using any suitable means and dispensed into the extraction chamber. The atomised water spray can be generated by a single spray nozzle directed into the extraction chamber, or by a plurality of spray nozzles arranged at different locations around the extraction chamber. The spray nozzles can be adapted to provide a desired type of spray, such as a jet or mist of atomised water.

[0052] The atomised water can be continuously sprayed into the extraction chamber during the heating step. Alternatively, the atomised water can be intermittently sprayed into the extraction chamber during the heating step. Spraying can be continuous throughout the heating step, or can be only for a portion of the heating step. For example, spraying can be stopped when a defined maximum volume of water has been sprayed into the extraction chamber.

[0053] For example, the flow rate of atomised water sprayed into the extraction chamber can be adjusted depending on the flow rate of the tobacco material within the extraction chamber. For example, the average flow rate of atomised water sprayed into the extraction chamber can be between about 3% and about 30% of the flow rate of the tobacco material, more preferably between about 5% and about 20% of the flow rate of the tobacco material, more preferably between about 7.5% and about 15% of the flow rate of the tobacco material. The flow rate of atomised water sprayed into the extraction chamber can also need to be controlled depending on other parameters, such as the total volume of water desired to be sprayed into the extraction chamber during the heating step.

[0054] Maintaining the flow rate of water at a level of no more than 30% of the tobacco flow rate ensures that the amount of water sprayed into the extraction chamber does not become so high that the temperature within the extraction chamber cannot be maintained due to excessive energy loss caused by evaporation of the atomised water. Maintaining the flow rate of water sprayed into the extraction chamber at this level also helps to prevent the tobacco material from becoming too viscous, which can cause the tobacco material to clump, thereby adversely affecting the efficiency of the extraction.

[0055] Preferably, the atomised water is sprayed into the extraction chamber at an average flow rate of at least about 0.2 grams per second, more preferably at least about 0.4 grams per second, more preferably at least about 0.6 grams per second.

[0056] Preferably, the atomised water is sprayed into the extraction chamber at an average flow rate of no more than about 1.6 grams per second, more preferably no more than about 1.4 grams per second, more preferably no more than about 1.2 grams per second. For example, the atomised water can be sprayed into the extraction chamber at a flow rate of between about 0.2 grams per second and about 1.6 grams per second, between about 0.4 grams per second and about 1.4 grams per second, or between about 0.6 grams per second and about 1.2 grams per second.

[0057] These values of flow rate refer to the average flow rate over the duration of the heating step. In the case of intermittent spraying of atomised water during the heating step, the actual flow rate during the intermittent spraying will therefore be higher than the average flow rate.

[0058] Preferably, the atomised 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.

[0059] Preferably, the atomised water is at room temperature (22 degrees Celsius) when it is sprayed into the extraction chamber. Since the temperature within the extraction chamber will be at least 120 degrees Celsius, the atomised water will evaporate rapidly once inside the extraction chamber.

[0060] The shape of the spray of atomised water can be adjusted by selecting the spray nozzle apparatus. Preferably, the atomised water is sprayed in a conical shape so as to disperse the atomised water as much as possible through the internal space within the extraction chamber. Alternatively, the atomised water can be sprayed into the extraction chamber as a mist without a defined shape.

[0061] The direction of the spray of atomised water can be adjusted by selecting the position and orientation of the spray nozzle. Preferably, the atomised water is sprayed generally parallel to the flow of tobacco within the extraction chamber.

[0062] The method of atomising the water will be known to the skilled person. In some embodiments, the water can be atomised in a stream of compressed inert gas, for example air. In other embodiments, the water can be atomised without a stream of gas due to the pressure within the spray nozzle.

[0063] The tobacco material is preferably circulated or agitated during the heating step so as to optimise the effect of the sprayed atomised water. This can be achieved, for example, by providing a stream of inert gas through the tobacco material during heating, as described below. Alternatively or additionally, the heating step can take place in an extraction chamber adapted to keep the tobacco material moving, for example a rotary dryer.

[0064] The heating step is preferably carried out in an inert atmosphere. Preferably, a stream of inert gas, for example nitrogen, is passed through the tobacco material during the heating step. In some cases, a combined stream of inert gas and water or steam can be used. The addition of water or steam to the tobacco during extraction has been found to increase the yield of extracted components. However, excessive addition of water or steam can lead to processing difficulties such as stickiness of the tobacco material.

[0065] The volatile tobacco compounds are released into the inert gas stream during the heating step, such that the inert gas acts as a carrier for the volatile components. The inert gas flow rate can be optimized based on the scale and geometry of the extraction chamber. A relatively high inert gas flow rate can advantageously increase the efficiency of extraction from the tobacco material.

[0066] Generally, when heating the tobacco material, any moisture present in the tobacco material is also released in the form of steam together with the volatile compounds.

[0067] The inert gas stream facilitates the transport of the steam generated by the evaporation of the moisture content of the tobacco material and the volatile compounds, in particular including nicotine or flavour-related compounds or both, out of the extraction apparatus.

[0068] Furthermore, the use of an inert gas stream, such as a nitrogen gas stream, under a slight overpressure in the extraction apparatus has the benefit of preventing the presence of oxygen within the extraction apparatus. This is desirable because it will prevent the risk of any, even partial, combustion of the tobacco material during the heating step. Uncontrolled combustion of the tobacco material is obviously undesirable because it represents a major safety risk within the manufacturing environment. However, the present inventors have found that even limited, partial combustion of the tobacco material can result in a decrease in the quality of the tobacco extract obtainable by the method, which would be undesirable.

[0069] Without wishing to be bound by theory, it will be appreciated that by preventing combustion of the tobacco material, the formation of any undesirable combustion by-products is also prevented. Furthermore, since conditions conducive to combustion of the tobacco material are prevented, the tobacco material is effectively heated under conditions that mimic the conditions under which tobacco-containing substrates, such as homogenized tobacco material, are typically heated in "heat-not-burn" articles. As a result, the selective extraction of flavour-bearing volatile species that result in tastes that consumers associate with heated tobacco is advantageously preferred.

[0070] Thus, by carrying out the heating step in an inert atmosphere, extraction efficiency, product quality and manufacturing safety will advantageously be enhanced.

[0071] Heating the tobacco material in an inert gas stream has the additional benefit that the inert gas stream containing the volatile compounds can be more easily directed into a container containing the extraction solvent, for example a non-aqueous extraction liquid solvent.

[0072] Optionally, the heating step can be carried out under vacuum. This removes any oxygen present within the extraction chamber, which removal can advantageously prevent the reaction of the tobacco material or the volatile compounds generated upon heating of the tobacco material with oxygen. As mentioned above, the removal of oxygen will also prevent any combustion of the tobacco material.

[0073] Preferably, the amount of nicotine extracted from the tobacco material during the heating step corresponds to at least about 2 grams per kilogram of dry tobacco material, more preferably at least about 2.2 grams per kilogram of dry tobacco material, due to the inclusion of the water spraying step in the extraction method of the present application. As demonstrated in the examples below, this nicotine extraction yield is significantly higher than the possible nicotine extraction yield using an equivalent extraction method but without the spraying step.

[0074] The liquid tobacco extract can be produced from a tobacco material consisting of a single type of natural tobacco. Alternatively, the tobacco material can comprise a blend of two or more types of natural tobacco. The ratio of different tobacco types can be adjusted according to the desired characteristics of the aerosol generated from the liquid tobacco extract. For example, where it is desired to provide a relatively high level of nicotine, the proportion of burley tobacco can be increased.

[0075] The term "natural tobacco" as used herein in relation to the present application describes any part of any member of the Nicotiana genus, including but not limited to leaves, midribs, stems and stalks. In particular, the natural tobacco can comprise fire-cured Virginia tobacco material, burley tobacco material, Oriental tobacco material, Maryland tobacco material, dark tobacco material, dark air-cured tobacco material, yellow tobacco material as well as material from other rare or specialty tobaccos or blends thereof. As will be described in more detail below, the tobacco material can be whole (e.g. whole leaves), shredded, cut or ground.

[0076] Where it is desired to produce the liquid tobacco extract from a combination of two or more different tobacco types, the tobacco types can be heated separately at different extraction temperatures within a defined range of 100 degrees Celsius to 160 degrees Celsius, or a mixture of the tobacco types can be heated together at a single extraction temperature within this range.

[0077] The tobacco material can be a solid tobacco material, such as a powder, leaf crumb or shreds or whole leaves. Alternatively, the tobacco material can be a liquid tobacco material, such as a pellet, gel, slurry or suspension.

[0078] The tobacco material can be derived from any suitable tobacco material, including but not limited to tobacco leaves, tobacco stems, reconstituted tobacco, cast tobacco, extruded tobacco or tobacco-derived pellets.

[0079] Preferably, in the step of preparing the tobacco material, the tobacco is ground or cut so as to reduce the size of the tobacco particles within the tobacco material. This can advantageously improve the heating uniformity and extraction efficiency of the tobacco material.

[0080] The tobacco material can optionally be dried prior to the heating step in order to reduce the water content of the tobacco material. Drying of the tobacco material can be carried out by any suitable chemical or physical drying process. Alternatively, water can be added to the tobacco material prior to the heating step in order to increase the water content of the tobacco material.

[0081] In certain embodiments of the application, the step of preparing the tobacco material can comprise the step of impregnating the tobacco material with an aerosol-forming agent. When this impregnation of the tobacco material is carried out prior to the heating step, this can advantageously increase the amount of certain desirable tobacco compounds released from the tobacco material on heating. For example, it has been found that impregnating the tobacco material with glycerol advantageously increases the amount of nicotine extracted from the tobacco material. In another example, it has been found that impregnating the tobacco material with a non-aqueous extraction solvent which is also an aerosol-forming agent, such as propylene glycol, phytoglycerol, 1,3-propanediol, glyceryl triacetate or mixtures thereof, advantageously increases the amount of flavour compounds extracted from the tobacco material.

[0082] Alternatively or additionally, the tobacco material can comprise one or more additional ingredients, such as a non-aqueous solvent. An example of a suitable solvent is propylene glycol.

[0083] Thus, the tobacco material can comprise at least about 40% by weight of natural tobacco material or at least about 60% by weight of natural tobacco material or at least about 80% by weight of natural tobacco material or at least about 90% by weight of natural tobacco material or at least about 95% by weight of natural tobacco material.

[0084] The water content of the tobacco starting material can be at least about 3% by weight. Preferably, the water content of the tobacco starting material is at least about 5% by weight. More preferably, the water content of the tobacco starting material is at least about 5% by weight. It will be appreciated that the "water content of the tobacco starting material" can include water which is inherently present in the natural tobacco material as well as any added water.

[0085] The water content of the tobacco starting material can be less than or equal to about 60% by weight. Preferably, the water content of the tobacco starting material is less than or equal to about 20% by weight. More preferably, the water content of the tobacco starting material is less than or equal to about 12% by weight.

[0086] In some embodiments, the water content of the tobacco starting material can be from about 3% to about 60% by weight, more preferably from about 3% to about 20% by weight, even more preferably from about 3% to about 12% by weight. In other embodiments, the water content of the tobacco starting material can be from about 5% to about 60% by weight, more preferably from about 5% to about 20% by weight, even more preferably from about 5% to about 12% by weight. In further embodiments, the water content of the tobacco starting material can be from about 8% to about 60% by weight, more preferably from about 8% to about 20% by weight, even more preferably from about 8% to about 12% by weight.

[0087] In some embodiments, the non-aqueous solvent content can be at least about 5 wt% or at least about 10 wt% or at least about 15 wt% or at least about 20 wt% or at least about 25 wt% or at least about 30 wt% or at least about 35 wt% or at least about 40 wt%.

[0088] Optionally, the tobacco material can be enzymatically digested prior to the heating step. This has been found to provide a significant increase in the yield of certain flavour compounds from the tobacco material.

[0089] In certain embodiments, in the step 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 step of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to significantly increase the pH of the tobacco.

[0090] In other embodiments, the method further comprises the step of subjecting the tobacco material to an alkali treatment prior to the heating step. Where the method comprises a pre-treatment step of microwave heating the tobacco material, the alkali treatment is preferably carried out prior to the microwave heating. During the alkali treatment, an alkali solution is preferably applied to the tobacco material to provide an alkali tobacco material, and the extraction is then carried out using the alkali tobacco material.

[0091] It has been found that including an alkali treatment step prior to heating the tobacco material provides a further significant increase in the yield of nicotine obtained during the extraction.

[0092] Preferably, the pH of the alkali 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 alkali tobacco material is no more than 11.

[0093] By "the pH of the alkali tobacco material" is meant the pH of an aqueous suspension of the alkali tobacco material formed by preparing an aqueous suspension of the alkali tobacco material at a ratio of 1 :20. The pH of the suspension is measured after a soak time of 30 minutes.

[0094] As described above, in the alkali treatment step, an alkali solution is applied to the tobacco material prior to heating. A suitable alkali solution can be selected, for example, depending on the desired pH of the tobacco material. Preferably, the alkali solution is an aqueous solution of an alkali agent. A preferred example of a suitable alkali solution for use in the alkali treatment step is an aqueous solution of potassium carbonate. Other suitable alkali solutions for use in the present application include, but are not limited to, sodium hydroxide, sodium carbonate and hydrogen peroxide.

[0095] Prior to the heating step, the tobacco material can optionally be analysed in order to determine the composition, for example the reducing sugar content of the alkaloids. This information about the composition can be helpful in selecting an appropriate extraction temperature.

[0096] The method according to the invention may further include a step of microwave heating the tobacco material during at least one step of the method. The tobacco material may be microwave heated during a pretreatment step prior to the heating step. Alternatively or additionally, the tobacco material may be microwave heated during the main heating step, in place of conventional heating or in combination with conventional heating.

[0097] It has been found that including a microwave heating step in the extraction method of the present invention provides a further improvement in the nicotine extraction yield.

[0098] During the heating of tobacco material, volatile compounds are released from the tobacco material in gaseous form. These volatile compounds are collected using any suitable technique. As mentioned above, when the tobacco material is heated in an inert gas stream, the volatile compounds are collected from the inert gas stream. Different collection methods will be well known to those skilled in the art.

[0099] In some preferred embodiments, the step of collecting volatile compounds utilizes an absorption technique in which the volatile compounds are trapped in a non-aqueous extraction liquid solvent. For example, an inert gas stream containing the volatile compounds can be directed into a container of the non-aqueous extraction liquid solvent. The non-aqueous extraction liquid solvent is preferably an aerosol forming agent such as glyceryl triacetate, glycerol, 1,3-propanediol, propylene glycol, or combinations thereof. Using an aerosol forming agent as the liquid solvent is potentially advantageous because the aerosol forming agent can be retained as a diluent in the final liquid tobacco extract. This means that an additional step of removing the non-aqueous extraction solvent is unnecessary.

[0100] As used herein in conjunction with the invention, the term "aerosol forming agent" refers to a compound or mixture of compounds that will promote the formation of aerosols during use and is preferably substantially resistant to thermal degradation at the operating temperature of the aerosol-generating article or apparatus. Examples of suitable aerosol forming agents include: polyols such as propylene glycol, triethylene glycol, 1,3-propanediol, and glycerol; esters of polyols such as glycerol monoacetate, glycerol diacetate, or glycerol triacetate; and aliphatic esters of mono-, di-, or polycarboxylic acids such as dimethyl dodecanoate and dimethyl tetradecanoate.

[0101] Preferably, the non-aqueous liquid solvent is maintained at a temperature below 0 degrees Celsius to optimize the transfer of volatile compounds into the liquid solvent. The non-aqueous extraction solvent is preferably maintained at a temperature not lower than -10 degrees Celsius. Temperatures below such values ​​may result in undesirable freezing phenomena.

[0102] In an alternative preferred embodiment, the step of collecting the volatile compounds can be performed using a condensation technique in which the volatile compounds are condensed and the condensate is collected. The condensation of the volatile compounds can be performed using any suitable equipment, such as in a refrigerated column. Preferably, the obtained condensate is added to a liquid aerosol forming agent, preferably propylene glycol.

[0103] The addition of a liquid aerosol former, in particular propylene glycol, in the collecting step can advantageously prevent the split of condensed volatile compounds into two phases or the formation of an emulsion, as some tobacco components tend to do. Without wishing to be bound by theory, the present inventors have observed that the solubility of tobacco components in a hydrolysate (i.e. the aqueous fraction of a liquid tobacco extract of natural origin) mainly depends on its polarity, its concentration and the pH of the hydrolysate, which can vary with the tobacco type. As a result, an oily layer tends to form at the surface of the liquid tobacco extract of natural origin if the amount of aerosol former is insufficient. Such oily material can accumulate at different locations on the trapping and dewatering equipment where the third and further steps of the process are respectively carried out. The addition of a liquid aerosol former such as propylene glycol helps to prevent the formation of such a layer and favours the homogenization of the liquid tobacco extract of natural origin. This in turn helps to prevent any loss of desirable flavour-related compounds during the fourth (dewatering) step, during which such compounds can undesirably deposit on the surface of the equipment.

[0104] In addition, the liquid aerosol former advantageously helps to trap flavour-related compounds, irrespective of their polarity and volatility. Moreover, the liquid aerosol former helps to prevent the loss of the most volatile fractions during any subsequent drying step and favours the selective removal of excess water from the liquid tobacco extract of natural origin to obtain a concentrated tobacco extract.

[0105] The use of propylene glycol as an aerosol former in the collecting step has the further advantage that propylene glycol exerts an antimicrobial activity by reducing the water activity of the aqueous solution. By adjusting the content of propylene glycol in the liquid tobacco extract, it is thus also possible to ensure that the extract does not substantially undergo any microbial activity.

[0106] As yet another alternative, the step of collecting the volatile compounds can be carried out using an adsorption technique in which the volatile compounds are adsorbed onto the surface of a solid adsorbent material such as activated carbon. The adsorbed compounds are then transferred into a liquid solvent.

[0107] In the process of the present application, the next step is to form a liquid tobacco extract from the collected volatile compounds. The nature of this step can depend on the collecting process. The "collected volatile compounds" generally comprise a solution of tobacco-derived volatile compounds in a liquid solvent or carrier.

[0108] As described above, when volatile compounds are collected by absorption in a non-aqueous extraction solvent, the extraction process provides a liquid tobacco extract that can include greater than about 25% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract can include greater than about 30% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract or greater than about 35% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0109] The liquid tobacco extract can include less than or equal to about 65% of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract can include less than or equal to 60% of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract or less than or equal to 55% of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0110] In some embodiments, the liquid tobacco extract can include from about 25% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract can include from about 25% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 60% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract can include from about 25% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0111] In other embodiments, the liquid tobacco extract can include from about 30% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract can include from about 30% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 60% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract can include from about 30% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55% by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

[0112] In further embodiments, the liquid tobacco extract can comprise from about 35 wt% non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 65 wt% non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract can comprise from about 35 wt% non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 60 wt% non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The liquid tobacco extract can comprise from about 35 wt% non-aqueous extraction solvent based on the weight of the liquid tobacco extract to about 55 wt% non-aqueous extraction solvent based on the weight of the liquid tobacco extract. The non-aqueous extraction solvent is preferably triacetin, glycerol, propylene glycol, 1,3-propanediol or a mixture thereof.

[0113] In preferred embodiments, the weight ratio of (beta-ionone + beta-damascenone) to (phenol) in the liquid tobacco extract is at least about 0.25.

[0114] In preferred embodiments, the weight ratio of (dimethylhydroxyfuranone + (2,3-diethyl-5-methylpyrazine) * 100)) to (nicotine) in the liquid tobacco extract is at least about 5 x 10 -4 .

[0115] When the volatile compounds are collected by absorption in a liquid solvent, as described above, the step of forming the liquid tobacco extract preferably comprises drying the solution of volatile compounds in the liquid solvent to concentrate the solution. This can be done, for example, to achieve a desired nicotine concentration or flavour compound concentration. The drying can be performed using any suitable measure, including but not limited to dehydration, molecular sieves, freeze-drying, phase separation, distillation, membrane permeation, controlled crystallization and filtration of water, reverse hygroscopicity, ultracentrifugation, liquid chromatography, reverse osmosis or chemical drying.

[0116] In preferred embodiments, the solution of volatile compounds in the liquid solvent is concentrated by dehydration.

[0117] In other words, the solution of volatile compounds in the liquid solvent is heated to evaporate at least some of the water and to obtain a concentrated tobacco extract. To this end, the solution of volatile compounds in the liquid solvent can be heated to a certain temperature for a certain time such that the water content in the tobacco extract is reduced by at least about 60%.

[0118] The partially dehydrated concentrated tobacco extract can be considered the main product of the method according to the present application. The depleted tobacco material from which the volatile species and the bulk of the moisture content have been extracted when heated during the second step can be considered a by-product of the method. Such depleted tobacco material can typically have a moisture content of about 1 to 5 wt%, preferably about 2 to 3 wt%.

[0119] In one embodiment, the solution of volatile compounds in liquid solvent is heated under vacuum, preferably at a temperature of at least about 70 degrees Celsius. In another embodiment, the solution of volatile compounds in liquid solvent is heated under a stream of air, preferably a stream of air having a relatively low humidity, at a temperature of at least about 35 degrees Celsius. Thus, a naturally derived concentrated tobacco extract can be obtained by the method according to the present application. One such naturally derived concentrated tobacco extract contains less than about 20% water by weight.

[0120] Alternatively, where the volatile compounds are collected by condensation, the step of forming a liquid tobacco extract can comprise adding the condensate to a liquid solvent such as an aerosol former.

[0121] Optionally, the step of forming a liquid tobacco extract comprises a filtration step.

[0122] Optionally, the step of forming a liquid tobacco extract comprises a blending step in which extracts derived from different tobacco materials are combined.

[0123] Optionally, the step of forming a liquid tobacco extract comprises adding one or more additives to the solution of volatile compounds, such as an organic acid. However, in many cases, the liquid tobacco extract is suitable for use without the inclusion of additives.

[0124] The present application also provides a liquid tobacco extract produced by a method according to the first aspect of the application as described in detail above. As described above, the method of the present application advantageously produces a natural liquid tobacco extract having a highly desirable ratio of desirable tobacco compounds, such as nicotine and flavour compounds, to undesirable tobacco compounds.

[0125] The liquid tobacco extract is particularly suitable for producing a nicotine composition, such as a liquid nicotine composition or a gel nicotine composition, for use in an aerosol-generating system. In such an aerosol-generating system, the nicotine composition is typically heated within an aerosol-generating device.

[0126] As used herein, the term "aerosol-generating device" refers to a device comprising a heater element that interacts with a nicotine composition incorporating a liquid tobacco extract, such as a liquid tobacco extract obtained by a method according to the present application, to produce an aerosol. During use, volatile compounds are released from the nicotine composition by heat transfer and entrained in air drawn through the aerosol-generating device. When the released compounds cool, they condense to form an aerosol that is inhaled by a consumer.

[0127] Upon heating the nicotine composition comprising the liquid tobacco extract according to the present application, an aerosol is released containing volatile compounds collected from the tobacco material during the extraction process. By controlling the parameters of the extraction parameters to control the composition of the liquid tobacco extract, the composition and characteristics of the resulting aerosol generated from the liquid tobacco extract and delivered to the consumer can be adjusted.

[0128] The nicotine composition can be the liquid tobacco extract produced by the extraction process according to the present application without the addition of more nicotine. The nicotine composition can be the liquid tobacco extract produced by the extraction process according to the present application without the addition of more flavor compounds. The nicotine composition can be the liquid tobacco extract produced by the extraction process according to the present application without the addition of more dimethylhydroxyfurfural. The nicotine composition can be the liquid tobacco extract produced by the extraction process according to the present application without the addition of more solvent.

[0129] Alternatively, the liquid tobacco extract can be subjected to additional processing steps to form the nicotine composition. Even when subjected to such additional steps, the nicotine composition can be formed without the need for the addition of more nicotine or flavor compounds.

[0130] Preferably, the liquid tobacco extract can be concentrated in a dewatering step as described above to form a concentrated tobacco extract, and the concentrated tobacco extract can be used to form the nicotine composition.

[0131] Preferably, the concentrated tobacco extract comprises from 8% to 15% by weight water based on the weight of the concentrated tobacco extract.

[0132] The dewatering step provides a concentrated tobacco extract that can have a non-aqueous extraction solvent content of from about 65% to about 95% by weight, preferably from about 65% to 85% by weight, most preferably from about 75% to about 85% by weight. The non-aqueous extraction solvent is preferably triacetin, glycerol, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0133] The dewatering step provides a concentrated tobacco extract that can have a nicotine content of at least about 0.2% by weight nicotine, preferably from about 0.5% to about 12% by weight nicotine, most preferably from about 2% to about 8% by weight nicotine.

[0134] Preferably, additional non-aqueous solvent can be added to the liquid tobacco extract or the concentrated tobacco extract to form the nicotine composition.

[0135] The nicotine composition can be a liquid nicotine composition or a gel nicotine composition.

[0136] The nicotine composition can include at least about 10% by weight of liquid tobacco extract. Preferably, the nicotine composition includes at least about 20% by weight of liquid tobacco extract. More preferably, the nicotine composition includes at least about 30% by weight of liquid tobacco extract. In preferred embodiments, the nicotine composition includes at least about 40% by weight of liquid tobacco extract, more preferably at least about 50% by weight of liquid tobacco extract, even more preferably at least about 60% by weight of liquid tobacco extract. In particularly preferred embodiments, the nicotine composition includes at least about 65% by weight of liquid tobacco extract, more preferably at least about 70% by weight of liquid tobacco extract, even more preferably at least about 75% by weight of liquid tobacco extract, most preferably at least about 80% by weight of liquid tobacco extract.

[0137] In some embodiments, the liquid tobacco extract is a concentrated tobacco extract. The nicotine composition can include at least about 10% by weight of concentrated tobacco extract, at least about 20% by weight of concentrated tobacco extract, at least about 30% by weight of concentrated tobacco extract, at least about 40% by weight of concentrated tobacco extract, at least about 50% by weight of concentrated tobacco extract, preferably at least about 60% by weight of concentrated tobacco extract, more preferably at least about 70% by weight of concentrated tobacco extract, even more preferably at least about 75% by weight of concentrated tobacco extract, most preferably at least about 80% by weight of concentrated tobacco extract.

[0138] In some embodiments, the nicotine composition includes about 40% to about 95% by weight of liquid tobacco extract. More preferably, the nicotine composition includes about 40% to about 95% by weight of liquid tobacco extract. Even more preferably, the nicotine composition includes about 50% to about 95% by weight of liquid tobacco extract. Most preferably, the nicotine composition includes about 60% to about 95% by weight of liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition includes about 70% to about 95% by weight of liquid tobacco extract, even more preferably about 80% to about 95% by weight of liquid tobacco extract.

[0139] In some embodiments, the nicotine composition includes about 40% to about 90% by weight of liquid tobacco extract. More preferably, the nicotine composition includes about 40% to about 90% by weight of liquid tobacco extract. Even more preferably, the nicotine composition includes about 50% to about 90% by weight of liquid tobacco extract. Most preferably, the nicotine composition includes about 60% to about 90% by weight of liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition includes about 70% to about 90% by weight of liquid tobacco extract, even more preferably about 80% to about 90% by weight of liquid tobacco extract.

[0140] In some embodiments, the nicotine composition includes about 40% to about 85% by weight of the liquid tobacco extract. More preferably, the nicotine composition includes about 40% to about 85% by weight of the liquid tobacco extract. Even more preferably, the nicotine composition includes about 85% to about 90% by weight of the liquid tobacco extract. Most preferably, the nicotine composition includes about 60% to about 85% by weight of the liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition includes about 70% to about 85% by weight of the liquid tobacco extract, even more preferably about 80% to about 85% by weight of the liquid tobacco extract.

[0141] The nicotine composition can include up to about 100% by weight of the liquid tobacco extract. In some embodiments, the nicotine composition can be formed directly from the liquid tobacco extract without the addition of additional non-aqueous solvent, flavorant, or nicotine. That is, the nicotine composition can include 100% by weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract is a concentrated tobacco extract, such that the nicotine composition can include 100% by weight of the concentrated tobacco extract. In embodiments where the nicotine composition includes 100% by weight of the liquid tobacco extract or 100% by weight of the concentrated tobacco extract, there is no additional non-aqueous solvent.

[0142] Alternatively, in some embodiments, the nicotine composition including the liquid tobacco extract can include an additional non-aqueous solvent. The additional non-aqueous solvent is a non-aqueous solvent that has been added after the extraction step. 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 including the concentrated tobacco extract can include an additional non-aqueous solvent.

[0143] The additional non-aqueous solvent can be an aerosol former. Preferably, the additional non-aqueous solvent is triacetin, glycerol, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0144] In embodiments where the nicotine composition includes an additional non-aqueous solvent, the nicotine composition can include 90% or less by weight of the additional non-aqueous solvent. Preferably, the nicotine composition includes 80% or less by weight of the additional non-aqueous solvent. More preferably, the nicotine composition includes 70% or less by weight of the additional non-aqueous solvent. In preferred embodiments, the nicotine composition includes about 60% or less by weight of the additional non-aqueous solvent, more preferably about 50% or less by weight of the additional non-aqueous solvent, even more preferably about 40% or less by weight of the additional non-aqueous solvent. In particularly preferred embodiments, the nicotine composition includes about 35% or less by weight of the additional non-aqueous solvent, more preferably about 30% or less by weight of the additional non-aqueous solvent, even more preferably about 25% or less by weight of the additional non-aqueous solvent, most preferably about 20% or less by weight of the additional non-aqueous solvent.

[0145] In the nicotine composition prepared by the method according to the present application, at least 50% by weight of the nicotine content in the nicotine composition based on the total weight of the nicotine composition can come from the tobacco extract rather than being added after extraction. In preferred embodiments, at least 80% by weight of the nicotine content in the nicotine composition based on the total weight of the nicotine composition comes from the tobacco extract rather than being added after extraction. Even more preferably, at least 90% by weight of the nicotine content in the nicotine composition based on the total weight of the nicotine composition comes from the tobacco extract rather than being added after extraction.

[0146] In the nicotine composition prepared by the method according to the present application, at least 50% by weight of the non-aqueous extraction solvent content in the nicotine composition based on the total weight of the nicotine composition can come from the tobacco extract rather than being added after extraction. In preferred embodiments, at least 80% by weight of the non-aqueous extraction solvent content in the nicotine composition based on the total weight of the nicotine composition comes from the tobacco extract rather than being added after extraction. Even more preferably, at least 90% by weight of the non-aqueous extraction solvent content in the nicotine composition based on the total weight of the nicotine composition comes from the tobacco extract rather than being added after extraction.

[0147] In the nicotine composition prepared by the method according to the present application, at least 50% by weight of the water content in the nicotine composition based on the total weight of the nicotine composition can come from the tobacco extract rather than being added after extraction. In preferred embodiments, at least 80% by weight of the water content in the nicotine composition based on the total weight of the nicotine composition comes from the tobacco extract rather than being added after extraction. Even more preferably, at least 90% by weight of the water content in the nicotine composition based on the total weight of the nicotine composition comes from the tobacco extract rather than being added after extraction.

[0148] In the nicotine composition prepared by the method according to the present application, at least 50% by weight of the desired tobacco flavour species content in the nicotine composition, based on the total weight of the nicotine composition, can come from the tobacco extract rather than being added after extraction. In preferred embodiments, at least 80% by weight of the desired tobacco flavour species content in the nicotine composition, based on the total weight of the nicotine composition, comes from the tobacco extract rather than being added after extraction. Even more preferably, at least 90% by weight of the desired tobacco flavour species content in the nicotine composition, based on the total weight of the nicotine composition, comes from the tobacco extract rather than being added after extraction.

[0149] The total content of non-aqueous solvent in the nicotine composition includes the non-aqueous extraction solvent and the additional non-aqueous solvent, if present. The nicotine composition can include a total content of non-aqueous solvent of about 10% to about 95% by weight. The nicotine composition preferably includes a total content of non-aqueous solvent of about 50% to about 95% by weight, for example about 65% to about 95% by weight, more preferably about 70% to about 90% by weight, most preferably about 80% to about 90% by weight. The non-aqueous solvent is preferably triacetin, glycerol, propylene glycol, 1,3-propanediol, or a mixture thereof.

[0150] The nicotine composition can include a total content of propylene glycol of about 10% to about 95% by weight. The nicotine composition can include a total content of propylene glycol of about 20% to about 95% by weight, such as about 50% to about 95% by weight, or about 65% to about 95% by weight, about 70% to about 90% by weight, or about 80% to about 90% by weight.

[0151] The nicotine composition can include a total content of glycerol triacetate of about 10% to about 95% by weight. The nicotine composition can include a total content of glycerol triacetate of about 20% to about 95% by weight, such as about 50% to about 95% by weight, about 70% to about 90% by weight, or about 65% to about 95% by weight, or about 80% to about 90% by weight.

[0152] The nicotine composition can include a total content of glycerol of about 10% to about 95% by weight. The nicotine composition can include a total content of glycerol of about 20% to about 95% by weight, such as about 50% to about 95% by weight, or about 65% to about 95% by weight, about 70% to about 90% by weight, or about 80% to about 90% by weight.

[0153] The nicotine composition can include a total content of 1,3-propanediol of about 10% to about 95% by weight. The nicotine composition can include a total content of 1,3-propanediol of about 20% to about 95% by weight, such as about 50% to about 95% by weight, or about 65% to about 95% by weight, or about 80% to about 90% by weight.

[0154] The nicotine composition of the present application includes at least 0.2% by weight nicotine. More preferably, the nicotine content of the nicotine composition liquid tobacco extract is at least about 0.4% by weight. The nicotine composition can have a nicotine content of about 12% or less by weight, for example about 10% or less by weight, preferably about 8% or less by weight, more preferably about 5% or less by weight, preferably about 3.6% or less by weight. Most preferably, the nicotine composition includes between about 0.4% and 3.6% by weight nicotine based on the weight of the nicotine composition.

[0155] The nicotine composition can include between 1% and 85% by weight water. The nicotine composition can include between 2% and 50% by weight water. The nicotine composition can include between 3% and 30% by weight water. The nicotine composition can include between 5% and 25% by weight water. The nicotine composition can include between 8% and 20% by weight water. The nicotine composition preferably includes between 10% and 15% by weight water.

[0156] In some embodiments, the nicotine composition can include one or more water-soluble organic acids. As used herein in connection with the present application, the term "water-soluble organic acid" describes an organic acid having a water solubility greater than or equal to about 500 mg / ml at 20 °C.

[0157] The one or more water-soluble organic acids can advantageously bind with nicotine in the liquid tobacco extract by forming one or more nicotine salts. The one or more nicotine salts can advantageously dissolve and stabilize in the water or non-aqueous solvent present in the liquid tobacco extract. As described above, this can advantageously reduce nicotine adsorption in the upper airway and enhance pulmonary nicotine delivery and retention.

[0158] Preferably, the nicotine composition has a water-soluble organic acid content greater than or equal to about 2% by weight. More preferably, the nicotine composition has a water-soluble organic acid content greater than or equal to about 3% by weight.

[0159] The water-soluble organic acid can be acetic acid.

[0160] Exogenous acetic acid is acetic acid added from a source other than tobacco plant material and is not naturally occurring in the tobacco plant isolated, removed or derived from the tobacco plant material using extraction processing conditions and techniques.

[0161] If acetic acid is added to the liquid tobacco extract to form the nicotine composition, the total acetic acid content in the nicotine composition, including exogenous acetic acid and endogenous acetic acid, is preferably about 0.01 wt% to about 8 wt%, for example between about 0.03 wt% to about 8 wt%, about 0.3 wt% to about 8 wt%, about 2 wt% to about 8 wt%, or about 3 wt% to about 8 wt%. More preferably, the total acetic acid content is about 0.01 wt% to about 6 wt%, for example between about 0.03 wt% to about 6 wt%, about 0.3 wt% to about 6 wt%, about 2 wt% to about 6 wt%, or about 3 wt% to about 6 wt%.

[0162] Preferably, the nicotine composition has a water-soluble organic acid content of less than or equal to about 8 wt%. More preferably, the nicotine composition has a water-soluble organic acid content of less than or equal to about 6 wt%.

[0163] Preferably, the nicotine composition has a water-soluble organic acid content of between about 2 wt% to about 8 wt%. For example, the nicotine composition can have a water-soluble organic acid content of between about 2 wt% to about 6 wt%.

[0164] More preferably, the nicotine composition has a water-soluble organic acid content of between about 3 wt% to about 8 wt%. For example, the nicotine composition can have a water-soluble organic acid content of between about 3 wt% to about 6 wt%.

[0165] The nicotine composition can include one or more non-tobacco derived flavorants. Suitable non-tobacco derived flavorants include, but are not limited to, menthol.

[0166] Preferably, the nicotine composition has a non-tobacco derived flavorant content of less than or equal to about 4 wt%. More preferably, the nicotine composition has a non-tobacco derived flavorant content of less than or equal to about 3 wt%. For example, the liquid tobacco extract produced by the method of the present application can be used to make a nicotine composition that includes 10 to 20 mg of nicotine per milliliter without the need to add nicotine.

[0167] A nicotine composition suitable for use in an aerosol-generating system can include the liquid tobacco extract produced in the method according to the present application in combination with water and an additional aerosol former. The nicotine composition can include, for example, between about 10 wt% to about 20 wt% water.

[0168] A nicotine composition comprising a liquid tobacco extract according to the present application can be provided in a cartridge for use in an aerosol-generating system. The cartridge can comprise an atomiser configured to generate an aerosol from the nicotine composition. The atomiser can be a heat atomiser configured to heat the nicotine composition to generate an aerosol. The heat atomiser can comprise, for example, a heater and a liquid delivery element configured to deliver the nicotine composition to the heater. The liquid delivery element can comprise a capillary wick. Alternatively, the atomiser can be a non-heat atomiser configured to generate an aerosol from the nicotine composition by non-thermal means. The non-heat atomiser can be, for example, a shockwave jet atomiser, an ultrasonic atomiser or a vibrating mesh atomiser.

[0169] A cartridge containing a nicotine composition formed from a liquid tobacco extract of the present application can be used in conjunction with any suitable aerosol-generating device comprising a housing configured to receive at least a portion of the cartridge. The aerosol-generating device can comprise a battery and control electronics.

[0170] Embodiments of the present application will now be further described by way of example only.

[0171] Comparative Example

[0172] In the process of the present application, tobacco material is cut to form tobacco shreds having a maximum dimension of 2.5 millimetres by 2.5 millimetres and the tobacco shreds are loaded into an extraction chamber without compression. The tobacco material is heated to a temperature of 140 degrees Celsius within the extraction chamber for a period of 120 minutes. During the heating, a stream of nitrogen gas is passed through the extraction chamber at a flow rate of about 20 litres per minute. The tobacco flow rate is 30 kilograms per hour and the extraction chamber is rotated at a speed of 1 rpm in order to circulate the tobacco.

[0173] During the heating step, atomised water is continuously sprayed into the extraction chamber at a rate of approximately 0.5 grams per second, with a pressure of 1 bar and a temperature of 22 degrees Celsius.

[0174] Volatile compounds released from the tobacco material during the heating step are collected by condensation at 0 degrees Celsius and dissolved in propylene glycol.

[0175] Nicotine composition 1 shown in the table below is a liquid tobacco extract obtained directly from the extraction process according to the present application with the water spraying step.

[0176] In a second comparative extraction process, the tobacco material is maintained at a moisture content of about 10% oven volatiles (o.v.) and the tobacco material is extracted under the same conditions as described above, except that the water spraying step is omitted. Thus, the second extraction process is not in accordance with the present application. Nicotine composition 2 shown in the table below is a liquid tobacco extract obtained directly from this second extraction process.

[0177] In a third comparative extraction method, the tobacco material was moistened to a moisture content of 20% oven volatiles (o.v.) prior to the heating step, and the moistened tobacco material was extracted under the same conditions as described above, except that the water spray step was omitted. Thus, the third extraction method does not according to the present application. Nicotine composition 3 shown in the table below is a liquid tobacco extract obtained directly from this third extraction method.

[0178] Each nicotine composition was analysed to measure the nicotine content, and the nicotine yield was calculated based on the total dry weight of the tobacco material. The extraction yield of certain flavour compounds was also measured. The results of this analysis are shown in the table below.

[0179]

[0180] As is clear from the table above, the inclusion of the water spray step in the method according to the present application provides a significant increase in the extraction yield of nicotine compared to the method in which the water spray step is omitted. Comparison between the nicotine yields of nicotine compositions 1 and 3 also demonstrates that the improvement in nicotine yield is provided specifically by the spray of atomised water, as the same increase in nicotine yield was not observed when the tobacco material was moistened prior to heating, as in the third comparative method above. As also shown in the table above, the inclusion of the water spray step provides a significant improvement in the extraction yield of certain flavour compounds, including: sotolone 68%, 2-phenylethanol 16%, 3-methylbutanoic acid 15% and 2-methylbutanoic acid 3%.

Claims

1. A method for producing a liquid tobacco extract, the method comprising the following steps: Preparation of tobacco materials; The tobacco material is heated in the extraction chamber for at least 90 minutes at an extraction temperature between 120°C and 160°C. Collect volatile compounds released from the tobacco material during the heating step; and This forms a liquid tobacco extract containing the collected volatile compounds. The method further includes the step of spraying atomized water into the extraction chamber during the heating step.

2. The method according to claim 1, wherein the spraying of atomized water in the extraction chamber generates a turbulent gas flow.

3. The method according to claim 1 or 2, wherein atomized water is continuously sprayed into the extraction chamber during the heating step.

4. The method according to claim 1 or 2, wherein the atomized water is sprayed into the extraction chamber at a rate of at least 0.2 g / s.

5. The method according to claim 1 or 2, wherein the average flow rate of the atomized water sprayed into the extraction chamber during the heating step is between 3% and 30% of the flow rate of the tobacco material through the extraction chamber.

6. The method according to claim 1 or 2, wherein the atomized water is atomized in a compressed inert gas stream.

7. The method according to claim 1 or 2, wherein the atomized water is sprayed into the extraction chamber at a pressure of at least 1 bar.

8. The method according to claim 1 or 2, wherein the tobacco material is continuously circulated in the extraction chamber during the heating step.

9. The method according to claim 1 or 2, wherein the amount of nicotine extracted from the tobacco material during the heating step corresponds to at least 2 grams per kilogram of dry tobacco material.

10. The method according to claim 1 or 2, wherein the tobacco material is heated in an inert gas stream during the heating step.

11. The method according to claim 1 or 2, wherein the tobacco material is heated at an extraction temperature between 130 degrees Celsius and 150 degrees Celsius.

12. The method according to claim 1 or 2, further comprising the step of subjecting the tobacco material to alkali treatment prior to the heating step.

13. The method according to claim 1 or 2, wherein the tobacco material is microwave heated during at least one step of the method.

14. The method according to claim 1 or 2, further comprising the step of drying the collected volatile compounds.

15. The method according to claim 1 or 2, further comprising the step of concentrating the collected volatile compounds.

16. A liquid tobacco extract, said liquid tobacco extract being produced by the method according to any of the preceding claims.

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