RU2845695C1 - Method of producing liquid tobacco extract - Google Patents

Abstract

FIELD: smoking accessories.

SUBSTANCE: invention relates to a method of producing a liquid tobacco extract. Method includes following steps: preparing tobacco material; heating the tobacco material at an extraction temperature of 100 °C to 160 °C for at least 15 minutes, wherein tobacco material is directly heated; collecting volatile compounds released from the tobacco material during the heating step; and formation of liquid tobacco extract containing collected volatile compounds. Tobacco material is heated under the effect of microwaves during at least one step of the method.

EFFECT: invention allows to increase nicotine extraction yield.

14 cl

Description

The present invention relates to a method for producing a liquid tobacco extract and to a liquid tobacco extract obtained using such a method.

Aerosol generating systems for delivering an aerosol to a user are known, which comprise an atomizer configured to generate an inhalable aerosol from a liquid composition, such as a liquid nicotine-based composition. Some known aerosol generating systems comprise a thermal atomizer, such as an electrical heater, configured to heat and vaporize a liquid composition 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 atomizer configured to generate an aerosol from a liquid composition using, for example, jet stream, ultrasound, or vibrating mesh technologies.

There are several known methods 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.

Maceration methods are also known in which the tobacco material is kept in suspension in an extraction liquid for a period of up to several weeks or even months. The resulting pulp is then filtered, and the liquid phase thus collected can be used to produce an evaporated liquid composition. In one such method - the so-called "cold maceration method" - there is usually no way to control the extraction conditions (e.g., temperature and pressure). In one variant of the maceration method, which has been described, for example, in US 2012/192880, the pulp is heated to 100 degrees Celsius or higher.

The liquid phase collected from the pulp filtration, which is the primary product of the maceration process, is highly dilute and tends to have low levels of apolar tobacco flavor compounds. Additionally, the liquid phase typically contains little or no nicotine. Thus, liquid extracts obtained by the maceration process typically require the addition of additional ingredients such as nicotine salts and glycerin before use in the vaporized liquid formulation.

Alternative processes are known in which the 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 large proportion of apolar compounds accumulates on the surface of the distillate.

On the one hand, the aqueous portion, over which the waxy layer accumulates and which contains nicotine and other water-soluble compounds, is returned by recirculation to the water heater. An apolar auxiliary solvent may optionally be fed to the water heater with the aqueous portion to increase the yield of the extraction product. On the other hand, the waxy phase is collected and eventually forms the primary product of one such hydrodistillation process. Such a product is often called "tobacco essential oil" and contains a large proportion of apolar compounds found in tobacco, such as fatty acids, neophytadiene, etc. Tobacco essential oil obtained by one such process usually does not contain nicotine.

It is also known to subject the tobacco material to an extraction process involving the use of a volatile apolar 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 may be evaporated by controlled heating under vacuum. Typically, this is carried out in the presence of ethanol, which has a higher boiling point than the extraction solvent, so that even very small amounts of extraction solvent can be detected.

The primary product of one such solvent extraction process is often referred to as "tobacco absolute" and may contain very small amounts of ethanol. It is a waxy product and contains a highly concentrated mixture of most of the apolar compounds that can be extracted with a particular solvent, usually including nicotine, which is usually present in relatively high concentrations.

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 operates on the principle that volatiles in a feed material that is contacted with a supercritical fluid can be separated into the supercritical phase. After any soluble material has dissolved, the supercritical fluid containing the solutes can be removed and the dissolved components of the feed material can be separated from the supercritical fluid. The primary product of the supercritical extraction process is substantially similar to the "tobacco absolute" from the solvent extraction process, occurring at lower temperature and lower pressure, contains no residual solvent, and typically has a high level of waxy apolar compounds and includes nicotine, which is typically present in relatively high concentrations.

However, all tobacco extracts obtained by methods known in the art tend to have very low levels of compounds associated with heated tobacco aroma, such as furaneol, or none at all.

In general, as discussed above, liquid tobacco extracts obtained by such known extraction processes may have a low level of nicotine. In addition, liquid tobacco extracts obtained by such extraction processes may have a low level and low variety of flavor compounds. Liquid tobacco extracts obtained by such extraction processes may also have a high level of undesirable compounds. In general, the concentration of nicotine, flavor compounds and undesirable compounds obtained by such extraction methods can be significantly affected by the type or types of tobacco used as a starting material.

An object of the present invention is to alleviate one or more disadvantages of liquid tobacco extracts obtained by known methods. In particular, it would be desirable to provide a method for producing a new and improved liquid tobacco extract. It would be especially desirable to provide a method for producing this liquid tobacco extract that could be carried out more efficiently than by existing methods.

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

According to the present invention, a method for producing a liquid tobacco extract is included, wherein the method comprises the steps of: preparing a tobacco material; heating the tobacco material at an extraction temperature of from about 100 degrees Celsius to about 160 degrees Celsius 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 heated under the influence of microwaves during at least one step of the method.

According to the present invention, further included is a liquid tobacco extract obtained by the method of the present invention described above.

In the context of this document, in relation to the present invention, the term "liquid tobacco extract" describes the direct product of an extraction process carried out on a tobacco material. Thus, a tobacco extract typically includes a mixture of natural components that are separated, extracted or obtained from the natural tobacco material using tobacco processing conditions and techniques by extraction. Thus, in one such process, extracted tobacco components are removed from the natural tobacco material and separated from non-extracted tobacco components. According to the present invention, an extraction process for producing a liquid tobacco extract includes heating the tobacco material under specific heating conditions and collecting the generated volatile compounds. The volatile compounds will be in gaseous form when released from the tobacco material. Accordingly, the liquid tobacco extract consists of a mixture of natural tobacco components that have been obtained from a tobacco material and have been extracted or formed during an extraction process, typically in combination with one or more materials other than the tobacco material, such as a non-aqueous extraction solvent used during the extraction process. As will be described in more detail below, the volatile compounds released from the original tobacco material can be collected using an absorption technique in which the volatile compounds are trapped in a non-aqueous extraction solvent. As an example, an inert gas stream containing the volatile compounds can be directed into a container with a non-aqueous extraction solvent. The non-aqueous extraction solvent is preferably an aerosol forming agent.

The present invention relates to a new method of extraction by microwave action, which includes a step of heating tobacco material by microwave action at a certain stage during the extraction method. As described in more detail below, the tobacco material may be heated by microwave action before the heating step, during which the tobacco material is heated to a temperature of from 100 degrees Celsius to 160 degrees Celsius, or the heating by microwave action may occur during the heating step.

It has been found that the inclusion of a microwave heating step in the extraction method of the present invention significantly increases the extraction yield of nicotine, in some cases by as much as 600 percent, compared to an equivalent extraction method without the microwave heating step. It is believed that this effect is due to the way in which microwaves heat the tobacco from the inside, by rapidly heating the water molecules in the tobacco cells. When the water inside the tobacco cells boils, the volume inside the cell rapidly expands and the cell wall eventually ruptures. This increases the permeability of the plant material and, importantly, releases components that are contained in the cell wall, such as nicotine. These components are then more accessible for extraction during the heating step, so that the yield of these components is increased.

Microwave heating traditionally provides greater penetration and faster heating of the tobacco material than traditional resistive heating methods, and this can advantageously lead to a reduction in the time required to carry out the extraction method. For example, the inclusion of a microwave heating step, as found by the present inventors, leads to a reduction of up to 80 percent in the duration of the heating step. In addition, it is possible to provide a reduction in energy consumption of up to 40 percent. In general, the inclusion of a microwave heating step thus allows the extraction method to be carried out very efficiently with respect to both energy and time.

Because of the way microwaves heat the tobacco material from within the tobacco cells as described above, more uniform heating of the tobacco material can also be achieved compared to traditional heating methods such as resistive heating, which can only heat the tobacco material from the outside.

Microwave heating of tobacco material can be accomplished using a relatively simple and low-cost device that can be easily incorporated into existing extraction equipment and methods.

In addition to the benefit provided by the microwave heating step, the extraction method of the present invention employs an extraction temperature in a specific range in combination with a specific heating duration, which advantageously provides

an improved liquid tobacco extract characterized by a significantly improved ratio of desirable compounds to undesirable compounds. In particular, the extraction method of the present invention provides for the production of a liquid tobacco extract with a maximum ratio of desirable compounds to undesirable compounds for the tobacco material. For example, the use of a specific combination of a certain temperature and extraction time provides the ability to optimize the levels of nicotine compounds while simultaneously minimizing the levels of undesirable compounds such as furans, carbonyls, phenols and TSNA.

The inventors of the present invention have found that, in contrast to the existing extraction processes discussed above, the processes of the present invention advantageously provide a liquid tobacco extract characterized by a significantly higher content of compounds associated with heated tobacco flavor, such as, for example, furaneol. These compounds are substantially absent or present in insignificant amounts in tobacco extract obtained by a maceration process, which also typically contains little or no nicotine. These compounds are also typically absent or present in insignificant amounts in solvent-derived tobacco extract, including that obtained under supercritical conditions. Likewise, tobacco essential oil obtained by a distillation process also typically has very low, if any, content of such compounds associated with heated tobacco flavor.

Liquid tobacco extracts obtained by the methods according to the present invention present significant differences in composition compared to tobacco extracts obtained by existing extraction methods, and they can be used as a liquid for electronic cigarettes or for the production of a liquid for electronic cigarettes, which, when heated, generates an aerosol having a different composition and flavor characteristics compared to currently available liquids for electronic cigarettes. In particular, liquid tobacco extracts obtained by the method according to the present invention can be used to generate an aerosol providing a taste of heated tobacco, which is more similar to the aerosol generated by traditional cigarettes or by heating tobacco in a device for heating without combustion, compared to available aerosols obtained from existing liquid compositions based on nicotine.

The extraction method according to the present invention enables the production of a liquid tobacco extract characterized by optimized levels of nicotine and flavor compounds without the need to add these compounds after extraction. Thus, the obtained liquid tobacco extract can be advantageously used directly to produce a nicotine-based composition. The obtained 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-based composition. The nicotine-based composition can be intended for use in an electronic cigarette or other aerosol-generating system.

As described above, aerosol generating systems for delivering an aerosol to a user are known, which comprise an atomizer configured to generate an inhalable aerosol from a liquid composition, such as a liquid nicotine-based composition.

The method for producing a liquid tobacco extract according to the present invention can be effectively applied to all types and grades of tobacco, including Burley tobacco, fire-cured tobacco and oriental tobacco. The stages of the method can be easily adjusted to provide a liquid tobacco extract of a constant composition for various tobacco mixtures. The extraction method is further suitable for various forms of tobacco material.

In some cases, the tobacco material can be heated without the need for significant pre-treatment steps. Thus, the method can be carried out efficiently.

In the process of the present invention, the tobacco material is heated directly, rather than suspended in a liquid solvent for the heating step, as in many types of extraction processes of the prior art. This provides greater control over the conditions under which the tobacco material is heated, and also makes the extraction process more efficient. When heated, volatile compounds are released from the tobacco material in gaseous form.

As defined above, in the method according to the present invention, the tobacco material is heated by microwaves at a certain stage during the extraction. The heating by microwaves is preferably carried out before or during the heating step in order to optimize the effect of the heating by microwaves with respect to the extraction yield.

In some embodiments of the present invention, the step of preparing the tobacco material comprises preheating the tobacco material by heating under the action of microwaves, causing the rupture of tobacco cells, before the heating step. In the methods according to such embodiments, microwave heating of the tobacco material is thus carried out as a pretreatment step before the main extraction. Heating under the action of microwaves ruptures the cell walls of the tobacco material and releases nicotine from the tobacco cells, as described above, so that nicotine becomes more accessible during the subsequent heating step.

Preferably, during the pre-treatment step, the tobacco material is heated by microwaves 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.

Preferably, during the pre-treatment step, the microwave heating is carried out for from about 1 minute to about 5 minutes.

Optionally, in the methods of the present invention, in which the tobacco material is pre-treated by heating under the action of microwaves, the tobacco material is cooled to the ambient temperature (22 degrees Celsius) before the heating step is started, in order to optimize the efficiency of the main heating step. In some methods of the present invention, there may be no cooling step between the pre-treatment under the action of microwaves and the heating step. This may increase the efficiency of the method, since the tobacco material can enter the main heating step at an elevated temperature.

Optionally, the tobacco material is heated by microwaves during the pre-treatment stage in a flow of inert gas such as nitrogen. This is believed to allow the humidity to be maintained at a relatively low level, which results in the optimization of the propagation of the microwaves. In this way, the positive effect of the microwaves on the extraction of nicotine and other compounds can be maximized.

In embodiments in which the tobacco material is pre-treated by heating with microwaves before the main heating step as described above, the step of heating the tobacco material to a temperature of from 100 degrees Celsius to 160 degrees Celsius can be carried out by conventional heating, such as resistive heating or steam heating. Conventional heating can be carried out, for example, in a conventional oven or dryer. In some embodiments, the tobacco material can be subjected to additional heating with microwaves during the heating step, instead of conventional heating or in combination with conventional heating, as described in more detail below.

As an alternative or in addition to including a pre-treatment step comprising heating with microwaves, the step of heating the tobacco material to a temperature of from 100 degrees Celsius to 160 degrees Celsius may comprise heating the tobacco material with microwaves. In such embodiments, heating the tobacco material with microwaves occurs during a main extraction step in which volatile components are extracted in gaseous form from the tobacco material by heating. Heating with microwaves is thus used to increase the temperature of the tobacco material to vaporize tobacco compounds, and to rupture the tobacco cells to release components from the tobacco cells, as described above.

In such embodiments, the step of heating the tobacco material to a temperature of from 100 degrees Celsius to 160 degrees Celsius may be carried out by microwave heating alone.

Alternatively and preferably, the step of heating the tobacco material to a temperature of from 100 degrees Celsius to 160 degrees Celsius comprises 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 the conventional heating step, and the tobacco material is heated simultaneously by microwaves and conventional heating means, such as resistive heating means or steam. This combination of heating methods has been found to be particularly effective in increasing the extraction yield (in particular nicotine), since the effect of microwave heating appears to be optimized. In addition, 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. The efficiency of the extraction method is thus optimized. In some methods, it is useful to retain conventional heating in combination with microwave heating, rather than using microwave heating alone, since it may be easier to perform some heating steps using conventional heating means. For example, if the tobacco material is heated in a stream of inert gas, it may be necessary to heat the inert gas using resistive heating means.

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

Heating the tobacco material by microwaves can be carried out using any suitable means for generating microwaves. An example of a suitable device for heating the tobacco material by microwaves is the LABATRON™ ES3 integrated reactor and microwave transmission system from SAIREM, which can be used to carry out microwave extraction methods using a batch or continuous microwave reactor. This device is suitable for embodiments in which the tobacco material is heated simultaneously with microwave heating and conventional heating, as described above.

The microwave power should be controlled to achieve the required temperature of the tobacco material depending on the mass of tobacco material to be heated.

Preferably, a continuous circular motion or shaking of the tobacco material is provided during the heating under the influence of microwaves. This can be achieved, for example, by heating the tobacco material inside a rotary dryer. The continuous provision of a circular motion of the tobacco material prevents the formation of hot spots in the tobacco material and thus improves the homogeneity of the heating, so that the extraction yields can be optimized.

Preferably, the water content of the tobacco material at the start of the microwave heating step is at least about 10 percent by weight, more preferably at least about 20 percent by weight. The water content of the tobacco material may be no more than about 70 percent by weight at the start of the microwave heating step, more preferably no more than about 50 percent by weight, more preferably no more than about 40 percent by weight, more preferably no more than about 30 percent by weight. For example, the water content of the tobacco material at the start of the microwave heating step may be from about 10 percent to about 70 percent by weight, or from about 10 percent to about 50 percent by weight, or from about 10 percent to about 40 percent by weight, or from about 10 percent to about 20 percent by weight.

It should be understood that "water content of tobacco material" may include both the water originally present in the tobacco material and any added water.

The presence of water in the tobacco material is important for optimizing the effect of microwave heating on extraction, since boiling of water molecules in the tobacco cells will cause the cells to rupture and release nicotine and other compounds. The water content of the tobacco material is thus preferably maintained at a level of at least 10 percent by weight. In particular, it is undesirable to dry the tobacco material prior to microwave heating, since the cell rupture mechanisms have been found to be more effective if the tobacco material is not dried prior to microwave heating. Elimination of the drying step at this stage of the extraction process is advantageous since it reduces the time and energy required to provide the tobacco material for extraction and thus further improves the overall efficiency of the process compared to prior art extraction processes.

In some embodiments, the methods of the present invention may further comprise a step of introducing water into the tobacco material prior to the microwave heating step to increase the water content of the tobacco material, preferably to at least 10 percent by weight. For example, the tobacco material may be sprayed with liquid water or contacted with steam to increase the water content prior to microwave heating.

In embodiments of the present invention, in which the tobacco material is pre-treated by heating with microwaves before the main heating step, as described above, the method according to the present invention may further comprise the step of introducing water into the tobacco material after the step of heating with microwaves and before the main heating step to increase the water content of the tobacco material, preferably to at least 10 percent by weight. The step of pre-treatment with microwaves is likely to reduce the water content of the tobacco material as a result of evaporation of water from the tobacco cell during heating. This is advantageous to restore the loss of water from the tobacco material and bring the water content back to at least 10 percent by weight to ensure that the subsequent heating step for extraction of volatile compounds is optimized and any combustion of the tobacco material is avoided.

Optionally, in the methods according to the present invention, the water lost in the pre-treatment step under the influence of microwaves can be captured by subjecting the exhaust gas obtained during the pre-treatment step to a condensation process. In this way, valuable volatile components of the tobacco, which may also be lost during the pre-treatment step, can also be advantageously captured. The collected water and volatile components can then be used in re-humidifying the pre-treated tobacco. This can provide both re-humidification of the tobacco and a reduction in the potential loss of valuable volatile components.

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

During the heating step, the tobacco material is heated to an extraction temperature of about 100 degrees Celsius to about 160 degrees Celsius. It has been found that below this range, insufficient levels of nicotine and certain flavor compounds are released from the tobacco material, so that the resulting liquid tobacco extract lacks the desired flavor properties. On the other hand, if the tobacco material is heated to a temperature above this specific range, unacceptably high levels of certain undesirable tobacco compounds may be released.

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, more preferably at least about 125 degrees Celsius.

Preferably, the extraction temperature is no more than about 150 degrees Celsius, more preferably no more than about 145 degrees Celsius, more preferably no more than about 140 degrees Celsius, most preferably no more than about 135 degrees Celsius.

For example, the extraction temperature may be from about 110 degrees Celsius to 150 degrees Celsius, or from about 120 degrees Celsius to about 140 degrees Celsius, or from about 125 degrees Celsius to about 135 degrees Celsius, or about 130 degrees Celsius. It has been found that an extraction temperature of about 130 degrees Celsius provides a particularly optimal ratio of desirable and undesirable compounds in the liquid tobacco extract.

The extraction temperature may 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.

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

The tobacco material is heated at the extraction temperature for at least about 15 minutes, preferably for at least about 20 minutes, more preferably for at least about 25 minutes, more preferably for at least about 30 minutes, more preferably for at least about 40 minutes, more preferably for at least about 50 minutes, more preferably for at least about 60 minutes. This extraction time is long enough to effectively extract the desired tobacco flavor compounds to produce a liquid tobacco extract that can form an aerosol with the desired flavor properties. As described above, the inclusion of a microwave heating step in the extraction method of the present invention allows for a relatively rapid heating step, with a heating duration that is significantly shorter than typically required in prior art extraction methods.

Preferably, the tobacco material is heated at the extraction temperature for no more than about 180 minutes, more preferably no more than about 120 minutes.

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.

The heating time specified above corresponds to the length of time the tobacco material is heated at the extraction temperature and does not include the time required to raise the temperature of the tobacco material to the extraction temperature.

The extraction temperature and heating duration can be selected within the above ranges determined depending on factors such as the type of tobacco, possible other components of the tobacco material, the desired nicotine level or the desired composition of the liquid tobacco extract. By controlling the combination of temperature and extraction time, the composition of the liquid tobacco extract can be adjusted depending on the desired characteristics of the aerosol obtained from the liquid tobacco extract. In particular, the proportion of certain tobacco compounds in the liquid tobacco extract can be adjusted to a certain extent by selecting the extraction parameters to maximize the ratio of desired tobacco compounds and undesirable tobacco compounds in the liquid tobacco extract.

For a given tobacco compound, the change in the release rate of the compound as a function of the extraction temperature in the extraction method for any given tobacco material can be readily determined. For example, it has been found that the level of nicotine released from a tobacco material will generally increase with increasing extraction temperature. The magnitude of the increase has been found to vary among different types of tobacco.

It has also been found that the level of desirable tobacco flavor compounds, such as β-damascenone and β-ionone, which are released from the tobacco material will increase with increasing extraction temperature up to a certain peak extraction temperature, after which the level will begin to decrease. The peak extraction temperature for such flavor compounds is typically in the range of 100 degrees Celsius to 160 degrees Celsius, so that the level of desirable flavor compounds can be effectively optimized in the extraction method of the present invention.

It has been found that the level of many undesirable tobacco compounds increases slowly as the extraction temperature increases up to a certain threshold temperature, above which a rapid increase is observed. This applies, for example, to the level of phenolic compounds, TSNA and pyrazines, and in the case of light grade tobacco, to the level of furans and formaldehyde. In many cases, the threshold temperature is in the range from 100 degrees Celsius to 160 degrees Celsius, and thus the level of undesirable compounds can be effectively controlled in the extraction method of the present invention.

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

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

β-damascenone and β-ionone are desirable compounds associated with the aroma of tobacco. It has been found that the amount of β-damascenone and β-ionone released from the tobacco material will increase with increasing extraction temperature up to a certain peak extraction temperature, after which the level will begin to decrease. The peak extraction temperature for such flavor compounds is typically in the range of 100 degrees Celsius to 160 degrees Celsius, so that the level of desirable flavor compounds can be effectively adjusted and controlled in the extraction process.

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

As discussed above, the heating step can be carried out using conventional heating, microwave-assisted heating, or a combination of conventional heating and microwave-assisted heating.

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, hydrodistillation, vacuum distillation, flash distillation, and thin film hydrodistillation.

The heating step is preferably carried out in an inert atmosphere. Preferably, a stream of inert gas, such as nitrogen, is passed through the tobacco material during the heating step. In some cases, a stream of a mixture of inert gas and water or steam may be used. It has been found that adding water or steam to the tobacco during extraction increases the yield of extracted components. However, excessive addition of water or steam complicates the processing, such as causing the tobacco material to become sticky.

Volatile tobacco compounds are released into the inert gas stream during the heating stage, so that the inert gas (or a combination of inert gas with water or steam) acts as a carrier for the volatile components. The flow rate of the inert gas can be optimized based on the scale and geometry of the extraction chamber. A relatively high flow rate of inert gas can advantageously increase the extraction efficiency from the tobacco material.

Typically, when the tobacco material is heated, any moisture present in the tobacco material is also released along with the volatile compounds in the form of steam.

The inert gas flow assists in transporting the vapor generated by evaporation of moisture contained in the tobacco material and volatile compounds, including, in particular, nicotine or aroma-related compounds, or both, from the extraction equipment. Furthermore, in methods where the tobacco material is heated by heating under the influence of microwaves during this step, the inert gas flow has been found to advantageously maintain the humidity in the extraction chamber at a relatively low level, so that maximum propagation of microwaves through the tobacco material is ensured.

In addition, the use of a flow of inert gas, such as nitrogen, under slightly elevated pressure in the extraction equipment has the advantage of preventing oxygen from entering the extraction equipment. This is desirable because it prevents the risk of any, even partial, combustion of the tobacco material during the heating step. Obviously, uncontrolled combustion of the tobacco material would be undesirable because it would pose a major safety hazard in the production environment. However, the inventors have found that even limited, partial combustion of the tobacco material can lead to a deterioration in the quality of the tobacco extract obtained by the method, which would be undesirable.

Without being limited by any theory, it is believed that by preventing combustion of the tobacco material, the formation of any undesirable combustion by-products is also prevented. In addition, because conditions conducive to combustion of the tobacco material are prevented, the tobacco material is effectively heated under conditions that somewhat mimic the conditions under which a tobacco-containing substrate (e.g., homogenized tobacco material) is typically heated in "heat-not-burn" products. As a result, selective extraction of the aromatic volatile compounds that contribute to the flavor that consumers associate with heated tobacco is advantageously promoted.

Therefore, by implementing the heating step in an inert atmosphere, the extraction efficiency, product quality and production safety are mainly improved.

Heating the tobacco material in an inert gas stream has the additional advantage that the inert gas stream containing the volatile compounds can be more easily directed into a container containing an extraction solvent, such as a non-aqueous liquid extraction solvent.

Optionally, the heating step may be carried out under vacuum. This removes any oxygen present in the extraction chamber, which may advantageously prevent the tobacco material or volatile compounds generated by heating the tobacco material from reacting with oxygen. The removal of oxygen will also prevent any combustion of the tobacco material, as described above.

The methods according to the present invention may further comprise a step of spraying atomised 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 turbulent flow that is established in the extraction chamber as a result of the evaporation of the atomised water. As a result of the improved heat exchange, the inclusion of a step of spraying water into the extraction chamber during the heating step has been found to provide a further improvement in the yield of nicotine, as well as an increase in the yield of certain desirable flavour compounds from the tobacco material. If the heating step comprises heating under the influence of microwaves, as described above, then the presence of water also optimises the effect of microwaves on the tobacco material.

A jet of atomized water can be generated and distributed into the extraction chamber by any suitable means.

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 from about 3 percent to about 30 percent of the flow rate of the tobacco material.

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

Methods for atomizing water will be known to those skilled in the art. In some embodiments, water can be atomized in a stream of compressed inert gas, such as air. In other embodiments, water can be atomized without a gas stream by using pressure inside the spray nozzle.

The liquid tobacco extract may be prepared from a tobacco material consisting of a single type of natural tobacco. Alternatively, the tobacco material may comprise a mixture of two or more types of natural tobacco. The ratio of the different types of tobacco may be adjusted depending on the desired characteristics of the aerosol generated from the liquid tobacco extract. For example, if a relatively high nicotine level is desired, the proportion of Burley tobacco may be increased.

The term "natural tobacco" is used herein with reference to the present invention to describe any part of any plant belonging to the genus Nicotiana, including but not limited to leaves, leaf midribs, stems, and petioles. In particular, natural tobacco may include fire-cured tobacco material, Burley tobacco material, Oriental tobacco material, Maryland tobacco material, dark tobacco material, dark fire-cured tobacco material, shag tobacco material, and material from other rare or special types of tobacco or mixtures thereof. As will be described in more detail below, the tobacco material may be whole leaf (e.g., in the form of whole tobacco leaves), shredded, cut, or ground.

If it is desired to obtain 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 certain range from 100 degrees Celsius to 160 degrees Celsius, or a mixture of tobacco types may be heated together at a single extraction temperature within a certain range.

The tobacco material may be a solid tobacco material such as powder, tobacco pill, tobacco leaf pieces or intact leaves. Alternatively, the tobacco material may be a liquid tobacco material such as a paste, gel, slurry or suspension.

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

Preferably, in the stage of preparing the tobacco material, the tobacco is ground or cut to reduce the particle size of the tobacco in the tobacco material. This can advantageously improve the uniformity of heating of the tobacco material and the extraction efficiency.

The tobacco material may optionally be dried prior to the heating step to reduce the water content of the tobacco material. Drying of the tobacco material may be accomplished by any suitable chemical or physical drying method. Alternatively and preferably, water may be added to the tobacco material prior to the heating step to increase the water content of the tobacco material, particularly where microwave heating is employed during this step.

In certain embodiments of the present invention, the step of preparing the tobacco material may include the step of impregnating the tobacco material with an aerosol forming agent. If such impregnation of the tobacco material is performed prior to the heating step, it may advantageously increase the amount of certain desirable tobacco compounds released from the tobacco material upon heating. For example, it has been found that impregnating the tobacco material with glycerin 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 that is also an aerosol forming agent, such as propylene glycol, vegetable glycerin, 1,3-propanediol, triacetin, or mixtures thereof, advantageously increases the amount of flavor compounds extracted from the tobacco material.

In some embodiments, the tobacco material consists of natural tobacco that has not undergone any pre-treatment steps, such as adjusting the water content. Thus, the water content of the tobacco material may be approximately 10-20 percent by weight (the water content typically present in natural tobacco material). In other embodiments, the tobacco material may contain added water, as described above.

Alternatively or additionally, the tobacco material may contain one or more additional ingredients, such as, for example, a non-aqueous solvent. An example of a suitable solvent is propylene glycol.

Thus, the tobacco material may contain at least about 40 percent by weight of natural tobacco material, or at least about 60 percent by weight of natural tobacco material, or at least about 80 percent by weight of natural tobacco material, or at least about 90 percent by weight of natural tobacco material, or at least about 95 percent by weight of natural tobacco material.

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

Optionally, the tobacco material may be fermented prior to the heating step. This has been found to provide a significant increase in the yield of certain flavor compounds from the tobacco material.

In some embodiments, at the stage of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to change the pH of the tobacco. In particular, at the stage of preparing the tobacco material, the tobacco is not subjected to any treatment adapted to significantly increase the pH of the tobacco.

In other embodiments, the method further comprises a step of subjecting the tobacco material to an alkaline treatment before the heating step. If the method comprises a step of pre-treating by heating the tobacco material under the influence of microwaves, the alkaline treatment is preferably carried out before the microwave heating. During the microwave treatment, an alkaline solution is preferably applied to the tobacco material to provide an alkaline tobacco material, and the alkaline tobacco material is then used for extraction.

The inclusion of an alkaline treatment step prior to heating the tobacco material has been found to provide a further significant increase in the yield of nicotine obtained during extraction.

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 no more than 11.

"pH of alkalized tobacco material" means the pH of an aqueous suspension of alkalized tobacco material, which is formed by suspending the alkalized tobacco material in water at a ratio of 1:20. The pH of the suspension is measured after a soaking time of 30 minutes.

As described above, in the alkali 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.

Preferably, the alkaline solution is an aqueous solution of an alkaline agent. A preferred example of a suitable alkaline solution 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.

The tobacco material may optionally be analyzed prior to the heating step to determine composition, such as reducing sugars or alkaloids. This compositional information may be useful for selecting an appropriate extraction temperature.

During the heating of the tobacco material, volatile compounds in gaseous form are released from the tobacco material. The volatile compounds are collected using any suitable technique. If the tobacco material is heated in an inert gas stream, as described above, the volatile compounds are collected from the inert gas stream. Various collection methods are well known to those skilled in the art.

In certain preferred embodiments, the volatile compound collection step employs an absorption technique in which the volatile compounds are captured in a non-aqueous extraction liquid solvent. For example, an inert gas stream containing the volatile compounds can be directed into a container with a non-aqueous extraction liquid solvent. The non-aqueous extraction liquid solvent is preferably an aerosol former such as triacetin, glycerol, 1,3-propanediol, propylene glycol, or combinations thereof. The use of an aerosol former as a liquid solvent is potentially advantageous because the aerosol former 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 not necessary.

In the context of this document, in relation to the present invention, the term "aerosol former" refers to a compound or mixture of compounds that, when used, facilitate aerosol formation and are preferably substantially resistant to thermal degradation 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 and glycerol; esters of polyhydric alcohols such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids such as dimethyl dodecanedioate and dimethyl tetradecanedioate.

Preferably, the non-aqueous liquid solvent is maintained at a temperature of less than 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 of at least -10 degrees Celsius. Temperatures below these may result in undesirable freezing processes.

In alternative preferred embodiments, the step of collecting 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 device, such as in a cooled column. Preferably, the resulting condensate is added to a liquid substance for forming an aerosol, preferably propylene glycol.

The addition of a liquid aerosol former in the collection step, and in particular the addition of propylene glycol, can advantageously prevent the separation of the condensed volatile compounds into two phases or the formation of an emulsion, to which some tobacco constituents are prone. Without being limited by any theory, the inventors have found that the solubility of tobacco constituents in the hydrolate (i.e. the aqueous fraction of the liquid tobacco extract of natural origin) primarily depends on their polarity, concentration and pH of the hydrolate, which can vary depending on the type of tobacco. As a result, if the amount of the aerosol former is insufficient, an oily layer usually forms on the surface of the liquid tobacco extract of natural origin. Such oily material can accumulate in various areas of the collection and dehydration equipment in which the third and subsequent steps of the method are respectively carried out. The addition of an aerosol former, such as propylene glycol, helps prevent the formation of such a layer and promotes the homogenization of the liquid tobacco extract of natural origin. In turn, this helps prevent any loss of desirable aroma-related compounds during the fourth stage (dehydration), during which such compounds may undesirably deposit on equipment surfaces.

In addition, the liquid aerosol former helps to preferentially capture the aroma-related compounds regardless of their polarity and volatility. In addition, during any subsequent drying step, the liquid aerosol former helps to prevent the loss of the most volatile fraction and also facilitates the selective removal of excess water from the liquid tobacco extract of natural origin in order to obtain a concentrated tobacco extract.

The use of propylene glycol as an aerosol forming agent at the collection stage has the additional advantage that, by reducing the activity of water in aqueous solutions, propylene glycol exerts an antimicrobial effect. Therefore, by adjusting the propylene glycol content of the liquid tobacco extract, it is also possible to ensure that there is essentially no microbial activity in the extract.

As a further alternative, the volatile compound collection step 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 to a liquid solvent.

The next step of the method of the present invention is to obtain a liquid tobacco extract from the collected volatile compounds. The nature of this step may depend on the method of collection. The "collected volatile compounds" will typically comprise a solution of volatile compounds derived from tobacco in a liquid solvent or carrier.

If the volatile compounds are collected by absorption in a non-aqueous extraction solvent as described above, the extraction method provides a liquid tobacco extract that may contain more than about 25 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract may contain more than about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract or more than about 35 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

The liquid tobacco extract may contain about 65 percent or less of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract may contain about 60 percent or less of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract, about 55 percent or less of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract.

In some embodiments, the liquid tobacco extract may comprise from about 25 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 25 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 25 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.

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.

In additional embodiments, the liquid tobacco extract may comprise from about 35 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 35 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 35 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. The non-aqueous extraction solvent is preferably triacetin, glycerol, propylene glycol, 1,3-propanediol or a mixture thereof.

In preferred embodiments, the liquid tobacco extract has a weight ratio of (β-ionone + β-damascenone) to (phenol) of at least about 0.25.

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

If the volatile substances are collected by absorption in a liquid solvent as described above, the step of forming a liquid tobacco extract preferably includes drying a solution of the volatile compounds in the liquid solvent in order to concentrate this solution. This can be done, for example, to achieve a desired concentration of nicotine or flavor compounds. Drying can be accomplished using any suitable means, including, but not limited to, dehydration, molecular sieves, freeze-drying, phase separation, distillation, membrane permeation, controlled water crystallization and filtration, reverse hygroscopicity, ultracentrifugation, liquid chromatography, reverse osmosis, or chemical drying.

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

In other words, the solution of volatile compounds in the liquid solvent is heated to evaporate at least some of the water and produce a concentrated tobacco extract. To do this, the solution of volatile compounds in the liquid solvent may be heated to a certain temperature and for a certain time so as to reduce the water content of the tobacco extract by at least about 60 percent.

The partially dehydrated, concentrated tobacco extract may be considered the primary product of the process according to the present invention. The depleted tobacco material, from which the volatile compounds and most of the moisture content have been extracted during the heating in the second stage, may be considered a by-product of the process. Such depleted tobacco material may typically have a moisture content of about 1-5 weight percent, preferably about 2-3 weight percent.

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

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

Optionally, the step of forming the liquid tobacco extract includes a filtration step.

Optionally, the step of forming a liquid tobacco extract includes a mixing step in which extracts obtained from different tobacco materials are combined.

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. However, in many cases, the liquid tobacco extract is suitable for use without the inclusion of additives.

The present invention further comprises a liquid tobacco extract obtained by the method according to the first aspect of the present invention, as described in more detail above. As described above, the method according to the present invention advantageously produces a natural liquid tobacco extract characterized by a highly desirable ratio of desirable tobacco compounds, such as nicotine and flavor compounds, to undesirable tobacco compounds.

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

As used herein, the term "aerosol generating device" means a device comprising a heating element that interacts with a nicotine-based composition comprising a liquid tobacco extract, such as produced by the method of the present invention, to produce an aerosol. During use, volatile compounds are released from the nicotine-based 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 that is inhaled by the user.

When a nicotine-based composition containing a liquid tobacco extract according to the present invention is heated, an aerosol is released, which contains volatile compounds collected from the tobacco material during the extraction process. The composition and properties of the resulting aerosol obtained from the liquid tobacco extract and delivered to the consumer can be controlled by controlling the composition of the liquid tobacco extract using the control of parameters in the form of an extraction parameter.

The nicotine-based composition may be a liquid tobacco extract obtained by the extraction process according to the present invention, without adding additional nicotine. The nicotine-based composition may be a liquid tobacco extract obtained by the extraction process according to the present invention, without adding additional flavor compounds. The nicotine-based composition may be a liquid tobacco extract obtained by the extraction process according to the present invention, without adding additional furaneol. The nicotine-based composition may be a liquid tobacco extract obtained by the extraction process according to the present invention, without adding additional solvent.

Alternatively, the liquid tobacco extract may undergo additional processing steps to form the nicotine-based composition. Even with these additional steps, the nicotine-based composition may be formed without the need for adding additional nicotine or flavoring compounds.

Preferably, the liquid tobacco extract can be concentrated in the dehydration step as described above to form a concentrated tobacco extract, and the concentrated tobacco extract can be used to form a nicotine-based composition.

Preferably, the concentrated tobacco extract contains from 8 weight percent to 15 weight percent water, based on the weight of the concentrated tobacco extract.

The dehydration step produces a concentrated tobacco extract that may have a non-aqueous extraction solvent content of from about 65 percent by weight to about 95 percent by weight, preferably from about 65 percent by weight to 85 percent by weight, most preferably from about 75 percent by weight to about 85 percent by weight. The non-aqueous extraction solvent is preferably triacetin, glycerol, propylene glycol, 1,3-propanediol, or a mixture thereof.

The dehydration step produces a concentrated tobacco extract that may have a nicotine content of at least about 0.2 percent by weight nicotine, preferably from about 0.5 percent by weight to about 12 percent by weight nicotine, most preferably from about 2 percent by weight to about 8 percent by weight nicotine.

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

The nicotine-based composition may be a liquid nicotine-based composition or a gel nicotine-based composition.

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

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

In some embodiments, the nicotine-based composition comprises from about 40 weight percent to about 95 weight percent of a liquid tobacco extract. More preferably, the nicotine-based composition comprises from about 40 weight percent to about 95 weight percent of a liquid tobacco extract. Even more preferably, the nicotine-based composition comprises from about 50 weight percent to about 95 weight percent of a liquid tobacco extract. More preferably, the nicotine-based composition comprises from about 60 weight percent to about 95 weight percent of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine-based composition comprises from about 70 weight percent to about 95 weight percent of a liquid tobacco extract, even more preferably from about 80 weight percent to about 95 weight percent of a liquid tobacco extract.

In some embodiments, the nicotine-based composition comprises from about 40 weight percent to about 90 weight percent of a liquid tobacco extract. More preferably, the nicotine-based composition comprises from about 40 weight percent to about 90 weight percent of a liquid tobacco extract. Even more preferably, the nicotine-based composition comprises from about 50 weight percent to about 90 weight percent of a liquid tobacco extract. More preferably, the nicotine-based composition comprises from about 60 weight percent to about 90 weight percent of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine-based composition comprises from about 70 weight percent to about 90 weight percent of a liquid tobacco extract, even more preferably from about 80 weight percent to about 90 weight percent of a liquid tobacco extract.

In some embodiments, the nicotine-based composition comprises from about 40 weight percent to about 85 weight percent of a liquid tobacco extract. More preferably, the nicotine-based composition comprises from about 40 weight percent to about 85 weight percent of a liquid tobacco extract. Even more preferably, the nicotine-based composition comprises from about 85 weight percent to about 90 weight percent of a liquid tobacco extract. More preferably, the nicotine-based composition comprises from about 60 weight percent to about 85 weight percent of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine-based composition comprises from about 70 weight percent to about 85 weight percent of a liquid tobacco extract, even more preferably from about 80 weight percent to about 85 weight percent of a liquid tobacco extract.

The nicotine-based composition may comprise up to about 100 weight percent of a liquid tobacco extract. In some embodiments, the nicotine-based composition may be formed directly from the liquid tobacco extract without the need for adding additional non-aqueous solvent, flavors, or nicotine. That is, the nicotine-based composition may comprise 100 weight percent of a liquid tobacco extract. In some embodiments, the liquid tobacco extract is a concentrated tobacco extract, and then the nicotine-based composition may comprise 100 weight percent of the concentrated tobacco extract. In embodiments in which the nicotine-based composition comprises 100 weight percent of a liquid tobacco extract or 100 weight percent of a concentrated tobacco extract, the additional non-aqueous solvent is absent.

Alternatively, in some embodiments, the nicotine-based composition comprising the liquid tobacco extract may comprise an additional non-aqueous solvent. The additional non-aqueous solvent is a non-aqueous solvent that was added after the extraction step. The additional non-aqueous solvent is a solvent that is auxiliary to the non-aqueous extraction solvent present in the liquid tobacco extract. In embodiments in which the liquid tobacco extract is a concentrated tobacco extract, the nicotine-based composition comprising the concentrated tobacco extract may comprise an additional non-aqueous solvent.

The additional non-aqueous solvent may be an aerosol forming agent. Preferably, the additional non-aqueous solvent is triacetin, glycerol, propylene glycol, 1,3-propanediol, or a mixture thereof.

In embodiments in which the nicotine-based composition comprises an additional non-aqueous solvent, the nicotine-based composition may comprise 90 weight percent or less of the additional non-aqueous solvent. Preferably, the nicotine-based composition comprises 80 weight percent or less of the additional non-aqueous solvent. More preferably, the nicotine-based composition comprises 70 weight percent or less of the additional non-aqueous solvent. In preferred embodiments, the nicotine-based composition comprises about 60 weight percent or less of the additional non-aqueous solvent, about 50 weight percent or less of the additional non-aqueous solvent, even more preferably about 40 weight percent or less of the additional non-aqueous solvent. In some particularly preferred embodiments, the nicotine-based composition comprises about 35 percent by weight or less of the additional non-aqueous solvent, more preferably about 30 percent by weight or less of the additional non-aqueous solvent, even more preferably about 25 percent by weight or less of the additional non-aqueous solvent, most preferably about 20 percent by weight or less of the liquid tobacco extract.

In a nicotine-based composition obtained by the method according to the present invention, at least 50 weight percent, based on the total weight of the nicotine-based composition, of the nicotine content of the nicotine-based composition may originate from the tobacco extract, and not added after extraction. In preferred embodiments, at least 80 weight percent, based on the total weight of the nicotine-based composition, of the nicotine content of the nicotine-based composition originates from the tobacco extract, and not added after extraction. Even more preferably, at least 90 weight percent, based on the total weight of the nicotine-based composition, of the nicotine content of the nicotine-based composition originates from the tobacco extract, and not added after extraction.

In a nicotine-based composition obtained by the method according to the present invention, at least 50 weight percent based on the total weight of the nicotine-based composition of the content of the non-aqueous extraction solvent in the nicotine-based composition may originate from the tobacco extract and not be added after extraction. In preferred embodiments, at least 80 weight percent based on the total weight of the nicotine-based composition of the content of the non-aqueous extraction solvent in the nicotine-based composition originates from the tobacco extract and not be added after extraction. Even more preferably, at least 90 weight percent based on the total weight of the nicotine-based composition of the content of the non-aqueous extraction solvent in the nicotine-based composition originates from the tobacco extract and not be added after extraction.

In a nicotine-based composition obtained by the method according to the present invention, at least 50 weight percent based on the total weight of the nicotine-based composition of the water content in the nicotine-based composition may originate from the tobacco extract and not be added after extraction. In preferred embodiments, at least 80 weight percent based on the total weight of the nicotine-based composition of the water content in the nicotine-based composition originates from the tobacco extract and not be added after extraction. Even more preferably, at least 90 weight percent based on the total weight of the nicotine-based composition of the water content in the nicotine-based composition originates from the tobacco extract and not be added after extraction.

In a nicotine-based composition obtained by the method according to the present invention, at least 50 weight percent, based on the total weight of the nicotine-based composition, of the content of desirable tobacco flavor compounds in the nicotine-based composition may originate from the tobacco extract, and not added after extraction. In preferred embodiments, at least 80 weight percent, based on the total weight of the nicotine-based composition, of the content of desirable tobacco flavor compounds in the nicotine-based composition originates from the tobacco extract, and not added after extraction. Even more preferably, at least 90 weight percent, based on the total weight of the nicotine-based composition, of the content of desirable tobacco flavor compounds in the nicotine-based composition originates from the tobacco extract, and not added after extraction.

The total content of non-aqueous solvent in the nicotine-based composition includes the non-aqueous extraction solvent and the additional non-aqueous solvent, if present. The nicotine-based composition may provide a total content of non-aqueous solvent from about 10 percent by weight to about 95 percent by weight. The nicotine-based composition preferably includes a total content of non-aqueous solvent from about 50 percent by weight to about 95 percent by weight, such as from about 65 percent by weight to about 95 percent by weight, more preferably from about 70 to about 90 percent by weight, most preferably from about 80 percent by weight to about 90 percent by weight. The non-aqueous solvent is preferably triacetin, glycerol, propylene glycol, 1,3-propanediol or a mixture thereof.

The nicotine-based composition may have a total propylene glycol content of from about 10 weight percent to about 95 weight percent. The nicotine-based composition may have a total propylene glycol content of from about 20 weight percent to about 95 weight percent, such as from about 50 weight percent to about 95 weight percent or from about 65 weight percent to about 95 weight percent, from about 70 weight percent to about 90 weight percent or from about 80 weight percent to about 90 weight percent.

The nicotine-based composition may be characterized by a total triacetin content of from about 10 weight percent to about 95 weight percent. The nicotine-based composition may be characterized by a total triacetin content of from about 20 weight percent to about 95 weight percent, such as from about 50 weight percent to about 95 weight percent, from about 70 weight percent to about 90 weight percent, or from about 65 weight percent to about 95 weight percent, or from about 80 weight percent to about 90 weight percent.

The nicotine-based composition may be characterized by a total glycerin content of from about 10 weight percent to about 95 weight percent. The nicotine-based composition may be characterized by a total glycerin content of from about 20 weight percent to about 95 weight percent, such as from about 50 weight percent to about 95 weight percent or from about 65 weight percent to about 95 weight percent, from about 70 weight percent to about 90 weight percent or from about 80 weight percent to about 90 weight percent.

The nicotine-based composition may be characterized by a total 1,3-propanediol content of from about 10 weight percent to about 95 weight percent. The nicotine-based composition may be characterized by a total 1,3-propanediol content of from about 20 weight percent to about 95 weight percent, such as from about 50 weight percent to about 95 weight percent or from about 65 weight percent to about 95 weight percent, or from about 80 weight percent to about 90 weight percent.

The nicotine-based composition according to the present invention comprises at least 0.2 weight percent nicotine. More preferably, the nicotine content of the liquid tobacco extract of the nicotine-based composition is at least about 0.4 percent by weight. The nicotine-based composition may have a nicotine content of about 12 weight percent or less, such as about 10 weight percent or less, preferably about 8 weight percent or less, more preferably about 5 weight percent or less, preferably about 3.6 weight percent or less. More preferably, the nicotine-based composition comprises from about 0.4 weight percent to 3.6 weight percent nicotine, based on the weight of the nicotine-based composition.

The nicotine-based composition may contain from 1 weight percent to 85 weight percent of water. The nicotine-based composition may contain from 2 weight percent to 50 weight percent of water. The nicotine-based composition may contain from 3 weight percent to 30 weight percent of water. The nicotine-based composition may contain from 5 weight percent to 25 weight percent of water. The nicotine-based composition may contain from 8 weight percent to 20 weight percent of water. The nicotine-based composition preferably contains from 10 weight percent to 15 weight percent of water.

In some embodiments, the nicotine-based composition may comprise one or more water-soluble organic acids. As used herein in connection with the present invention, the term "water-soluble organic acid" describes an organic acid characterized by a solubility in water at 20°C that is greater than or equal to about 500 mg/mL.

One or more water-soluble organic acids may advantageously bind nicotine in the liquid tobacco extract by forming one of the nicotine salts. The one or more nicotine salts may advantageously be dissolved and stabilized in water present in the liquid tobacco extract or non-aqueous solvent. This may advantageously reduce nicotine adsorption in the upper respiratory tract and improve nicotine delivery to and retention in the lungs, as discussed above.

Preferably, the nicotine-based composition is characterized by a water-soluble organic acid content that is greater than or equal to about 2 weight percent. More preferably, the nicotine-based composition is characterized by a water-soluble organic acid content that is greater than or equal to about 3 weight percent.

The water-soluble organic acid may be acetic acid.

Exogenous acetic acid is acetic acid that has been added from a source other than tobacco plant material and is other than acetic acid naturally present in the tobacco plant that has been isolated, extracted, or produced from tobacco plant material using extraction processing conditions and techniques.

If acetic acid is added to the liquid tobacco extract to form the nicotine-based composition, the total acetic acid content of the nicotine-based composition, including both exogenous and endogenous acetic acid, is preferably from about 0.01 weight percent to about 8 weight percent, such as from about 0.03 weight percent to about 8 weight percent, from about 0.3 weight percent to about 8 weight percent, from about 2 weight percent to about 8 weight percent, or from about 3 weight percent to about 8 weight percent. More preferably, the total acetic acid content is from about 0.01 weight percent to about 6 weight percent, such as from about 0.03 weight percent to about 6 weight percent, from about 0.3 weight percent to about 6 weight percent, from about 2 weight percent to about 6 weight percent, or from about 3 weight percent to about 6 weight percent.

Preferably, the nicotine-based composition is characterized by a water-soluble organic acid content that is less than or equal to about 8 weight percent. More preferably, the nicotine-based composition is characterized by a water-soluble organic acid content that is less than or equal to about 6 weight percent.

Preferably, the nicotine-based composition is characterized by a water-soluble organic acid content of from about 2 weight percent to about 8 weight percent. For example, the nicotine-based composition can be characterized by a water-soluble organic acid content of from about 2 weight percent to about 6 weight percent.

More preferably, the nicotine-based composition is characterized by a water-soluble organic acid content of from about 3 weight percent to about 8 weight percent. For example, the nicotine-based composition can be characterized by a water-soluble organic acid content of from about 3 weight percent to about 6 weight percent.

The nicotine-based composition may contain one or more flavoring agents not derived from tobacco. Suitable flavoring agents not derived from tobacco include, but are not limited to, menthol.

Preferably, the nicotine-based composition has a non-tobacco flavoring content of less than or equal to about 4 weight percent. More preferably, the nicotine-based composition has a non-tobacco flavoring content of less than or equal to about 3 weight percent. For example, the liquid tobacco extract obtained by the method of the present invention can be used to prepare a nicotine-based composition containing 10 mg to 20 mg of nicotine per milliliter, without the need for added nicotine.

A nicotine-based composition suitable for use in an aerosol-generating system may comprise a liquid tobacco extract obtained by the method of the present invention in combination with water and an additional aerosol-forming substance. The nicotine-based composition may comprise, for example, from about 10 percent by weight to about 20 percent by weight of water.

A nicotine-based composition comprising a liquid tobacco extract according to the present invention may be presented in a cartridge for use in an aerosol-generating system. The cartridge may comprise an atomizer configured to generate an aerosol from the nicotine-based composition. The atomizer may be a thermal atomizer configured to heat the nicotine-based composition to generate an aerosol. The thermal atomizer may comprise, for example, a heater and a liquid-moving element configured to move the nicotine-based composition toward the heater. The liquid-moving element may comprise a capillary wick. Alternatively, the atomizer may be a non-thermal atomizer configured to generate an aerosol from the nicotine-based composition in a manner other than heating.

A non-thermal nebulizer may be, for example, a falling jet nebulizer, an ultrasonic nebulizer, or a vibrating mesh nebulizer.

A cartridge containing a nicotine-based composition formed from a liquid tobacco extract according to the present invention can be used in combination with any suitable aerosol-generating device that contains a housing configured to accommodate at least a portion of the cartridge. The aerosol-generating device can contain a battery and an electronic control circuit.

Specific embodiments of the present invention will now be described by way of example only.

In the extraction method according to the first embodiment, the tobacco material is obtained from light fire-cured tobacco. The tobacco material is cut to form tobacco pieces with a maximum size of 2.5 millimeters by 2.5 millimeters, and the tobacco pieces are pre-treated by heating under the influence of microwaves until the tobacco cells are ruptured. The pre-treated tobacco pieces are cooled and then placed in a humidification chamber to increase the water content to about 10 percent by weight. The tobacco pieces are then fed into an extraction chamber, without compression, at a tobacco flow rate of 30 kg per hour. The tobacco material is heated in the extraction chamber to a temperature of 130 degrees Celsius for a period of 2 hours. During the heating, a nitrogen stream is passed through the extraction chamber at a flow rate of about 20 liters per minute.

The volatile compounds released from the tobacco material during the heating step are collected by condensation at 0 degrees Celsius and added to a liquid solvent formed from propylene glycol.

The propylene glycol solution with collected volatile compounds is concentrated in a dehydration process to reduce the moisture content of the liquid tobacco extract to approximately 15 percent.

In the extraction method according to the second embodiment, the tobacco material is obtained from light fire-cured tobacco. The tobacco material is cut to form tobacco pieces of 2.5 millimeters by 2.5 millimeters, and water is introduced into the tobacco material to increase the water content to about 20 percent by weight. The tobacco pieces are loaded into an extraction chamber without compression. The tobacco material is heated in the extraction chamber to a temperature of 130 degrees Celsius for a period of 30 minutes. The heating is carried out using a combination of microwave heating and resistive heating, wherein the microwave heating provides at least 50 percent of the power for heating the tobacco material. During the heating, a nitrogen stream is passed through the extraction chamber at a rate of about 40 liters per minute.

The volatile compounds released from the tobacco material during the heating step are collected by condensation at 0 degrees Celsius and added to a liquid solvent formed from propylene glycol. The propylene glycol solution with the collected volatile compounds is concentrated in a dehydration process to reduce the moisture content of the liquid tobacco extract to approximately 15 percent.

Claims (19)

1. A method for producing a liquid tobacco extract, wherein the method includes the following stages: preparation of tobacco material; heating the tobacco material at an extraction temperature of 100 to 160°C for at least 15 minutes, wherein the tobacco material is heated directly; collecting volatile compounds released from the tobacco material during the heating stage; and formation of a liquid tobacco extract containing the collected volatile compounds, wherein the tobacco material is heated under the influence of microwaves during at least one step of the method. 2. The method according to claim 1, wherein the step of preparing the tobacco material comprises preheating the tobacco material by heating under the influence of microwaves, causing the rupture of tobacco cells, before the heating step. 3. The method according to claim 1, wherein the step of heating the tobacco material to an extraction temperature of 100 to 160°C is carried out by resistive heating or heating with steam. 4. The method according to claim 1, wherein the step of heating the tobacco material to an extraction temperature of from 100 to 160°C comprises heating the tobacco material under the influence of microwaves. 5. The method of claim 1, wherein the step of heating the tobacco material to an extraction temperature of from 100 to 160°C comprises heating the tobacco material using a combination of microwave heating and resistive heating or steam heating. 6. The method of claim 1, wherein the tobacco material is heated in a stream of inert gas during at least one of the heating step and the pre-treatment step, if present. 7. A method according to any one of the preceding claims, wherein the tobacco material has a moisture content of at least 10 percent by weight at the start of the microwave heating. 8. The method of any one of the preceding claims, further comprising the step of introducing water into the tobacco material prior to the microwave heating step to increase the moisture content of the tobacco material to at least 10 percent by weight. 9. A method according to any of the preceding claims, wherein the tobacco material is continuously provided with a circular motion during heating under the influence of microwaves. 10. A method according to any of the preceding claims, wherein the tobacco material is heated at an extraction temperature of from 125 to 160°C. 11. A method according to any one of the preceding claims, wherein the extraction temperature is selected to obtain a liquid tobacco extract having a nicotine content of at least 0.2 percent by weight, calculated on a dry weight basis. 12. The method according to any one of the preceding claims, further comprising the step of subjecting the tobacco material to an alkali treatment before the heating step and before the pre-treatment step, if present. 13. The method of any one of the preceding claims, further comprising the step of spraying water onto the tobacco material during the heating step. 14. The method according to any of the preceding claims, further comprising the step of drying or concentrating the collected volatile compounds.