US20240016199A1

US20240016199A1 - Improved method of producing a liquid tobacco extract

Info

Publication number: US20240016199A1
Application number: US18/255,389
Authority: US
Inventors: Sebastien LANASPEZE; Stefan Lauenstein; Simon Nussbaumer; Alain SCIBOZ; Morris Kevin HOOIJMANS
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2020-12-09
Filing date: 2021-12-06
Publication date: 2024-01-18
Also published as: CN116528698A; EP4258907A1; WO2022122651A1; BR112023010505A2; KR20230118622A; JP2023553598A

Abstract

A method of producing a liquid tobacco extract, the method including the steps of: preparing a tobacco material; applying an alkaline solution to the tobacco material to produce an alkalised tobacco material; heating the alkalised tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 30 minutes, the alkalised tobacco material being heated in a flow of inert gas or in a flow of a combination of an inert gas with water or steam, and a water content of the alkalised tobacco material, prior to the heating step, being between 10 percent by weight and 20 percent by weight; condensing volatile compounds released from the alkalised tobacco material during the heating step and collecting condensate of the volatile compounds; and forming a liquid tobacco extract comprising the condensate of the volatile compounds.

Description

The invention relates to a method of producing a liquid tobacco extract and to a liquid tobacco extract produced by such a method.
Aerosol-generating systems for delivering an aerosol to a user that comprise an atomiser configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine formulation, are known. Some known aerosol-generating systems comprise a thermal atomiser such as an electric heater that is configured to heat and vaporise the liquid formulation to generate an aerosol. One popular type of electrically heated aerosol-generating system is an e-cigarette. Other known aerosol-generating systems comprise a non-thermal atomiser that is configured to generate an aerosol from the liquid formulation using, for example, impinging jet, ultrasonic or vibrating mesh technologies.
Several methods for producing liquid tobacco extracts from tobacco material are known. Liquid tobacco extracts may be produced by a high temperature extraction process in which nicotine and other volatile flavour compounds are extracted from tobacco material and collected in a suitable solvent to form a natural liquid tobacco extract.
Maceration methods are also known, wherein a tobacco material is kept in suspension in an extraction liquid for a period of up to several weeks or even months. The resulting slurry is subsequently filtered, and the liquid phase thus collected can be used to manufacture a vaporisable liquid formulation. In one such method—so-called “cold maceration method”—there is generally no way of controlling the extraction conditions (e.g. temperature and pressure). In a variant of a maceration method, which has been described for example in US 2012/192880, the slurry is heated to 100 degrees Celsius or more.
The liquid phase collected upon filtration of the slurry, which represents the primary product of a maceration process, is highly diluted, and tends to have a low content of apolar tobacco flavour species. Additionally, the liquid phase typically contains little to no nicotine. As such, liquid extracts obtained by a maceration method generally need to be supplemented with additional ingredients, such as nicotine salts and glycerin, before being used in a vaporisable liquid formulation.
Alternative processes are known, wherein a tobacco material is substantially boiled in water for a period of hours or even days to form a vapour phase, and a distillate obtained by condensation of the vapour phase is continuously collected in a vessel. Over time, an oily, waxy layer containing a high proportion of apolar compounds builds up on the surface of the distillate.
On the one hand, the aqueous portion, above which the waxy layer builds up, and which contains nicotine and other water-soluble compounds, is recycled to the boiler. An apolar co-solvent may optionally be fed into the boiler with the aqueous portion in order to increase the extraction yield. On the other hand, the waxy phase is collected and ultimately forms the primary product of one such hydro-distillation process. Such product is often referred to as “tobacco essential oil”, and contains a high proportion of apolar compounds found in tobacco, such as fatty acids, neophytadiene, etc. The tobacco essential oil obtained by one such method typically contains no nicotine.
It is also known to subject tobacco material to an extraction process involving use of a volatile apolar solvent. Examples of suitable solvents are cyclic or acyclic short alkanes, as well as chlorinated solvents like dichloromethane. In one such process, the excess solvent may 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, such that even traces of the extraction solvent can be detected.
The primary product of one such solvent-aided extraction process is often referred to as “tobacco absolute”, and may contain traces of ethanol. It is a waxy product and contains a highly concentrated mixture of most of the apolar compounds that can be extracted with the specific solvent, generally including nicotine, which is generally present at relatively high concentrations.
An alternative extraction process involves contacting a 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 a feed material contacted with a supercritical fluid may 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 matter can be separated out from the supercritical fluid. The primary product of a supercritical extraction process is substantially similar to the “tobacco absolute” of a solvent-aided extraction process run at lower temperature and pressure, contains no residual solvent and typically has a high level of the waxy, apolar compounds and includes nicotine, which is generally present at relatively high concentrations.
However, all the tobacco extracts obtainable by methods known in the art tend to have a very low level—if any—of compounds associated with the flavour of heated tobacco, such as furaneol.
In general, as discussed above, liquid tobacco extracts obtained by such known extraction processes may have a low level of nicotine. Further, liquid tobacco extracts obtained by such extraction processes may have a low level and low variety of flavour species. Liquid tobacco extracts obtained by such extraction processes may also have a high level of undesirable compounds. In general, the concentration of nicotine, flavour species and undesirable compounds obtained by such extraction processes may be significantly impacted by the type or types of tobacco used as a starting material.
A purpose of the invention is to alleviate one or more of the drawbacks of the liquid tobacco extracts obtained by known processes. In particular, it would be desirable to provide a method for the production of a novel and improved liquid tobacco extract. It would be particularly desirable to provide such a method for producing such a liquid tobacco extract that could be carried out more efficiently than existing processes.
The present disclosure relates to a method for producing a liquid tobacco extract from a tobacco material. The method may include the step of preparing a tobacco material. An alkaline solution may be applied to the tobacco material to produce an alkalised tobacco material. The alkalised tobacco material may be heated at an extraction temperature of between about 100 degree Celsius and about 160 degrees Celsius. The heating may be carried out for at least 30 minutes. The alkalised tobacco material may be heated in a flow of inert gas or in a flow of a combination of an inert gas with water or steam. The method may further comprise the step of condensing the volatile compounds released from the alkalised tobacco material during the heating step and collecting the condensate of the volatile compounds. The method may further comprise the step of forming a liquid tobacco extract comprising the condensate of the volatile compounds.
The present disclosure further relates to an alternative method of producing a liquid tobacco extract from a tobacco material. The method may include the step of preparing a tobacco material. The tobacco material may be heated at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 90 minutes. The method may further comprise the steps of collecting the volatile compounds released from the tobacco starting material during the heating step and forming a first liquid tobacco extract comprising the collected volatile compounds from the tobacco starting material. The method may further comprise the step of applying an alkaline solution to the residual tobacco material from the heating step to produce an alkalised tobacco material. The alkalised tobacco material may be heated at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius. The method may further comprise the steps of collecting the volatile compounds released from the alkalised tobacco material during the heating step and forming a second liquid tobacco extract comprising the collected volatile compounds from the alkalised tobacco material.
According to a first aspect of the present invention there is provided a method of producing a liquid tobacco extract, the method comprising the steps of: preparing a tobacco material; applying an alkaline solution to the tobacco starting material to produce an alkalised tobacco material; heating the alkalised tobacco material at an extraction temperature of between about 100 degrees Celsius and about 160 degrees Celsius for at least about 30 minutes, wherein the alkalised tobacco material is heated in a flow of inert gas or in a flow of a combination of an inert gas with water or steam; condensing the volatile compounds released from the alkalised tobacco material during the heating step and collecting the condensate of the volatile compounds; and forming a liquid tobacco extract comprising the condensate of the volatile compounds.
According to a second aspect of 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 at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 90 minutes; collecting the volatile compounds released from the tobacco starting material during the heating step; forming a first liquid tobacco extract comprising the collected volatile compounds from the tobacco starting material; applying an alkaline solution to the residual tobacco material from the heating step to produce an alkalised tobacco material; heating the alkalised tobacco material in an extraction chamber at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius; collecting the volatile compounds released from the alkalised tobacco material during the heating step; and forming a second liquid tobacco extract comprising the collected volatile compounds from the alkalised tobacco material.
According to the present invention there is further provided a liquid tobacco extract produced by the methods of the present invention, as defined above.
As used herein with reference to the invention, the term “liquid tobacco extract” describes the direct product of an extraction process carried out on a tobacco material. Thus, the tobacco extract typically includes a mixture of natural components separated from, removed from, or derived from, a natural tobacco material using tobacco extraction processing conditions and techniques. Thus, in one such process extracted tobacco components are removed from the natural tobacco material and separated from unextracted tobacco components. According to the present invention, the extraction process for producing the liquid tobacco extract comprises heating the tobacco material under specific heating conditions and collecting the volatile compounds generated. The liquid tobacco extract therefore consists of the mixture of natural tobacco components that have derived from the tobacco material and have been extracted or formed during the 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 starting tobacco material may be collected using an absorption technique in which the volatile compounds are trapped in a non-aqueous extraction solvent. By way of example, an inert gas flow containing the volatile compounds may be directed into a container of a non-aqueous extraction solvent. The non-aqueous extraction solvent is preferably an aerosol former.
The present invention provides novel extraction methods including an alkaline treatment step during which an alkaline solution is applied to the tobacco material. In accordance with the first aspect of the invention, the alkaline treatment step may be carried out on the tobacco material prior to the heating step. The inclusion of an alkaline treatment step prior to heating, in combination with the defined conditions for heating, has been found to provide a very significant increase in the yield of nicotine. For example, the inclusion of the alkaline treatment step has been found in certain cases to provide an increase of up to 900 percent in the extraction yield of nicotine compared to an equivalent extraction carried out without the alkaline treatment step. The inclusion of the alkaline treatment step prior to heating has also been found to bring about a favourable change in the balance of flavour compounds in the resultant extract. In particular, the yield of certain desirable flavour compounds, such as certain pyrazine compounds, may be improved. Advantageously, these increases in the yield of nicotine and other flavour compounds is provided without any increase in the yield of TSNAs. Overall, the ratios of desirable to undesirable compounds in the extract can therefore be increased.
Without wishing to be bound by theory, it is believed that the alkaline treatment of the tobacco material facilitates the transition of nicotine from a protonated form to a free-base form, which in turn helps to transfer the nicotine into the gas phase more efficiently during the heating step.
In alternative methods according to the second aspect of the invention, the alkaline treatment step is carried out on the residual tobacco material that remains after the heating step. The alkalised tobacco material is then subjected to a second heating step to extract further volatile compounds which may optionally be added to the volatile compounds collected from the first heating step. Such methods therefore involve two separate heating steps to be carried out on the same batch or sample of tobacco material.
The “residual tobacco material” refers to the tobacco material that is left behind after the extraction that is carried out during the first heating step as defined above, in which the tobacco material is heated to a temperature of between 100 degrees and 160 degrees. The residual tobacco material is therefore the same tobacco material as used in the heating step, but which has had a proportion of volatile compounds removed from it already as a result of the extraction.
The inclusion of the alkaline treatment step at this stage in the extraction method, after the first heating step, has been found to further optimise the composition of the liquid tobacco extract that can be produced by the extraction method. The alkaline treatment of the residual tobacco material prior to a second extraction enables the second heating step to extract a higher proportion of the nicotine from the tobacco material such that the overall level of nicotine extracted can be maximised. This is for the same reasons as described above in relation to other embodiments of the invention.
The extraction of the additional nicotine is carried out in a separate, subsequent step to the first extraction of volatile compounds, so that the first extraction is unaffected by the alkaline treatment step. This allows the first extraction to be optimised in relation to the yield of the desirable flavour compounds from the tobacco material, whilst the second extraction advantageously enhances the overall nicotine yield.
The alkaline treatment step can advantageously be carried out within the existing extraction apparatus, so that the overall impact of the alkaline treatment step on the efficiency of the extraction process can be minimised. The alkaline treatment step can be carried out with readily available apparatus, which can be incorporated into existing extraction apparatus without the need for significant modification.
In addition to providing an improved yield of nicotine as a result of the inclusion of the alkaline treatment step, the extraction method of the present invention uses specific extraction conditions to advantageously provide an improved liquid tobacco extract having a significantly improved balance of desirable compounds to undesirable compounds. In particular, the extraction method of the present invention provides a liquid tobacco extract having a maximised ratio of desirable compounds to undesirable compounds for the tobacco material. For example, the use of the specific combination of extraction temperature and time as defined enables the levels of nicotine compounds to be optimised whilst also minimising the levels of undesirable compounds such as furans, carbonyls, phenols and TSNAs.
The inventors of the present invention have found that, in contrast to the existing extraction processes that have been discussed above, methods in accordance with the present invention advantageously provide a liquid tobacco extract that has a significantly higher content of compounds associated with the flavour of heated tobacco, such as for example furaneol. These compounds are substantially absent, or are present in trace amounts, in a tobacco extract obtained by a maceration process, which also typically contains little to no nicotine. These compounds are also generally absent or present in trace amounts in a tobacco extract obtained using a solvent, including under supercritical conditions. Similarly, a tobacco essential oil obtained by way of a distillation process also typically has a very low content—if any—of such compounds associated with the flavour of heated tobacco.
The liquid tobacco extracts obtained by methods in accordance with the invention present significant compositional differences with respect to tobacco extracts obtained by the existing extraction processes, and can be used as an e-liquid or for the preparation of an e-liquid that, when heated, generates an aerosol having a distinct composition and flavour characteristics compared with currently available e-liquids. In particular, liquid tobacco extracts obtained by a method in accordance with the invention may be used to generate an aerosol that provides a heated tobacco taste which more closely resembles an aerosol generated by conventional cigarettes or upon heating tobacco in a heat-not-burn device relative to available aerosols produced from existing liquid nicotine compositions.
The extraction method of the present invention enables a liquid tobacco extract to be produced which has optimised levels of nicotine and flavour compounds without the need for addition of such compounds after extraction. The resultant liquid tobacco extract can therefore advantageously be used directly to provide a nicotine composition. The resultant 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 for use in an e-cigarette or other aerosol-generating system.
Aerosol-generating systems for delivering an aerosol to a user that comprise an atomiser configured to generate an inhalable aerosol from a liquid formulation, such as a liquid nicotine composition, are known, as described above.
The method of producing a liquid tobacco extract of the present invention can be used effectively for all types and grades of tobacco, including Burley tobacco, flue-cured tobacco and Oriental tobacco. The method steps can be readily adjusted in order to provide a consistent liquid tobacco extract for a variety of blends of tobacco type. The extraction method is additionally suitable for a variety of forms of tobacco material.
As described above, the methods of the present invention incorporate an alkaline treatment step, which is carried out on the tobacco material prior to heating, or on the residual tobacco material. In either case, the alkaline treatment step may be carried out in the same way and any reference below to alkaline treatment of the tobacco material should be considered to also apply to alkaline treatment of the residual tobacco material, unless stated otherwise.
The alkaline treatment is carried out by applying an alkaline solution to the tobacco material to produce an alkalised tobacco material. Preferably, the alkaline solution is sprayed onto the tobacco material, such that the alkaline solution can be distributed as evenly as possible throughout the tobacco material.
In methods according to the first aspect of the invention, the alkaline solution may be applied to the tobacco material within the extraction chamber that the heating step is carried out in, or within a different, separate apparatus.
In methods according to the second aspect of the invention where the alkaline treatment step is carried out on the residual tobacco material from the first heating step, the alkaline solution may be applied to the residual tobacco material within the extraction chamber that the first heating step has taken place in. Alternatively, the residual tobacco material may be collected from the extraction chamber that the first heating step has taken place in and the alkaline solution may be applied to the residual tobacco material within a different apparatus. Alternatively again, the alkaline solution may be applied to the residual tobacco material as it is transferred from a first extraction chamber within which the first heating step takes place, to a second extraction chamber within which the second heating step takes place.
Preferably, the tobacco material is continuously circulated or agitated during application of the alkaline solution, so that there is a homogenous distribution of the alkaline solution. This optimises the effect of the alkaline solution on the nicotine yield from the alkalised tobacco material.
Preferably, the pH of the alkalised 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 alkalised tobacco material is no more than 11.
The “pH of the alkalised tobacco material” refers to the pH of an aqueous suspension of the alkalised tobacco material which is formed by making a suspension of the alkalised tobacco material in water at a ratio of 1:20. The pH of the suspension is measured after 30 minutes soaking time.
As described above, in the alkaline treatment step, an alkaline solution is applied to the tobacco material, or residual tobacco material. A suitable alkaline solution may be selected, for example, depending on the desired pH of the tobacco material. Preferably, the alkaline solution is an aqueous solution of an alkali 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.
Preferably, the water content of the alkalised tobacco material, prior to the heating step, is between about 10 percent by weight and about 20 percent by weight, more preferably between about 12 percent and about 20 percent by weight, more preferably between about 12 percent and about 18 percent by weight. By providing an alkalised tobacco material having a water content within this preferred range, the extraction of volatile compounds during the subsequent heating step has been found to be optimised. Preferably, the desired water content of the alkalised tobacco material is provided by the water within the alkaline solution so that the application of water and alkaline can be carried out in a single step. In this case, the concentration of the alkaline solution can be adjusted to provide the desired amount of water to alkalised tobacco material. Alternatively, additional water may be added to the alkalised tobacco material, separately to the alkaline solution.
In methods according to the second aspect of the present invention, in which the alkaline treatment is carried out on the residual tobacco material from the first heating step, the residual tobacco material will typically have a low water content following the heating of the tobacco material during the first heating step. In such methods, it will be particularly important to restore the water content of the residual tobacco material to a level of between 10 percent and 20 percent by weight prior to the second heating step. As described above, this remoistening of the residual tobacco material is preferably achieved through the inclusion of a sufficient amount of water in the alkaline solution applied to the residual tobacco material.
As defined above, in the method of the present invention, the tobacco material is heated under specific heating conditions to release the volatile tobacco components, which are collected and formed into a liquid tobacco extract. In embodiments according to the first aspect of the invention in which the tobacco material is subjected to the alkaline treatment prior to the heating step, the alkalised tobacco material will be heated as described below.
During the heating step, the tobacco material is heated to an extraction temperature of between about 100 degrees Celsius and about 160 degrees Celsius. It has been found that below this range, insufficient levels of nicotine and certain flavour compounds are released from the tobacco material such that the resultant 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, 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 between about 110 degrees Celsius and 150 degrees Celsius, or between about 120 degrees Celsius and about 140 degrees Celsius, or between about 125 degrees Celsius and about 135 degrees Celsius, or about 130 degrees Celsius. An extraction temperature of around 130 degrees Celsius has been found to provide a particularly optimised ratio of desirable to undesirable compounds in the liquid tobacco extract.
The tobacco material is heated at the extraction temperature 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 sufficiently long that the desired tobacco flavour compounds can be extracted efficiently to provide a liquid tobacco extract that can produce an aerosol having the desired flavour characteristics. The inclusion of the alkaline treatment step enables the heating step to be carried out relatively quickly, with a potentially shorter heating duration than is typically required in prior art extraction processes.
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 tobacco material may be heated for between about 30 minutes and about 180 minutes, or between about 30 minutes and about 120 minutes, or between about 40 minutes and about 180 minutes, or between about 40 minutes and about 120 minutes, or between about minutes and about 180 minutes, or between about 50 minutes and about 120 minutes, or between about 60 minutes and about 180 minutes, or between about 60 minutes and about 120 minutes
The heating time indicated above corresponds to the duration of time over which the tobacco material is heated at the extraction temperature and does not include the time taken to increase the temperature of the tobacco material up to the extraction temperature.
In methods according to the first aspect of the present invention in which the tobacco material is subjected to the alkaline treatment step prior to the first heating step, the amount of nicotine extracted from the alkalised tobacco material during the heating step preferably corresponds to at least about 10 grams per kg of dry tobacco material, more preferably at least about 12 grams per kg of dry tobacco material. As demonstrated in the example below, this extraction yield of nicotine is significantly higher than is possible using an equivalent extraction method but without the alkaline treatment step prior to heating.
Methods according to the second aspect of the present invention in which the residual tobacco material is subjected to an alkaline treatment step include a second heating step to remove further volatile compounds, in particular nicotine, from the residual tobacco material.
In such methods, during the first heating step, the tobacco material is heated to an extraction temperature of between about 100 degrees Celsius and about 160 degrees Celsius. Preferably, the extraction temperature of the first extraction step 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 of the first extraction step 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 of the first extraction step may be between about 110 degrees Celsius and 150 degrees Celsius, or between about 120 degrees Celsius and about 140 degrees Celsius, or between about 125 degrees Celsius and about 135 degrees Celsius, or about 130 degrees Celsius. An extraction temperature of around 130 degrees Celsius has been found to provide a particularly optimised ratio of desirable to undesirable compounds in the liquid tobacco extract.
During the first heating step, the tobacco material is heated at the extraction temperature for at least about 90 minutes, more preferably for at least about 120 minutes. 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. For example, the tobacco material may be heated for between about 90 minutes and about 270 minutes, or between about 90 minutes and about 180 minutes, or between about 120 minutes and about 270 minutes, or between about 120 minutes and about 180 minutes.
In the second heating step, the alkalised tobacco material is heated to an extraction temperature of between about 100 degrees and about 160 degrees. The temperature of the second heating step may be the same as the temperature selected for the first heating step, or it may be different.
Preferably, the extraction temperature for the second heating step 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 for the second heating step 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 for the second heating step may be between about 110 degrees Celsius and 150 degrees Celsius, or between about 120 degrees Celsius and about 140 degrees Celsius, or between about 125 degrees Celsius and about 135 degrees Celsius, or about 130 degrees Celsius.
In such methods comprising a second heating step, the alkalised tobacco material is preferably heated in the second heating step for at least 15 minutes, more preferably at least 20 minutes, more preferably at least 30 minutes, more preferably at least 40 minutes. The second heating step will typically be shorter than the first heating step. Preferably, during the second heating step, the alkalised tobacco material is heated for no more than about 120 minutes, more preferably no more than about 90 minutes. For example, the alkalised tobacco material may be heated for between about 15 minutes and about 120 minutes, or between about 15 minutes and about 90 minutes, or between about 20 minutes and about 120 minutes, or between about 20 minutes and about 90 minutes, or between about 30 minutes and about 120 minutes, or between about 30 minutes and about 90 minutes, or between about 40 minutes and about 120 minutes, or between about 40 minutes and about 90 minutes.
Preferably, the extraction temperature and the extraction time for the second heating step are selected in order to maximise the extraction of nicotine from the alkalised tobacco material.
The second heating step may be carried out in the same extraction chamber as the first heating step, or in a second extraction chamber. Where two extraction chambers are used for the separate heating steps, the extraction chambers may optionally be connected in order to achieve a continuous flow of the tobacco material through the extraction apparatus.
In methods according to the second aspect of the present invention in which the alkaline treatment step is carried out on the residual tobacco material after the first heating step, the additional amount of nicotine extracted from the alkalised tobacco material during the second heating step corresponds to at least about 1 gram per kg of dry tobacco material, more preferably at least about 2 grams per kg of dry tobacco material. This nicotine yield is in addition to the nicotine extracted from the tobacco material during the first heating step.
For each of the heating steps, the extraction temperature and the duration of heating may be selected within the ranges defined above depending upon 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 proportion of specific tobacco compounds within the liquid tobacco extract can be adjusted to a certain degree through the selection of the extraction parameters in order to maximise the ratio of desirable to undesirable tobacco compounds within the liquid tobacco extract.
For a specific tobacco compound, the variation in the level of release of the compound with extraction temperature during the extraction process can be readily determined for any given tobacco material. For example, it has been found that the level of nicotine released from a tobacco material will typically increase with increasing extraction temperature. The rate of increase has been found to vary for different tobacco types.
It has also been found that the level of desirable tobacco flavour compounds, such as β-damascenone and β-ionone, released from a 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 flavour compounds is typically within the range of 120 degrees Celsius to 160 degrees Celsius such that the level of desirable flavour compounds can be effectively optimised in the extraction method of the present invention.
Many undesirable tobacco compounds have been found to increase slowly with increasing extraction temperature up to a threshold temperature, beyond which a rapid increase is observed. This applies, for example, to the level of phenolic compounds, TSNAs and certain pyrazines and in the case of Bright tobaccos, to the level of furans and formaldehyde. In many cases, the threshold temperature is within the range of 120 degrees Celsius to 160 degrees Celsius and therefore the level of the 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, in methods according to the second aspect of the invention, the extraction temperature or the extraction time or both the extraction temperature and the extraction time of the heating steps are selected to provide a ratio by weight 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 tobacco flavour. It has been found that the amount of 3-damascenone and β-ionone released from a tobacco material will increase with increasing the extraction temperature up to a certain peak extraction temperature, after which the level will begin to decrease. The peak extraction temperature for such flavour compounds is typically within the range of 120 degrees Celsius to 160 degrees Celsius such that the level of desirable flavour compounds can be effectively tailored and controlled in the extraction method.
Preferably, in methods according to the second aspect of the invention, the extraction temperature or the extraction time or both the extraction temperature and the extraction time of the heating steps are selected to provide a ratio by weight of (furaneol+(2,3-diethyl-5-methylpyrazine)*100)) to (nicotine) of at least about 5×10⁻⁴in the liquid tobacco extract.
It has been found that in methods in accordance with the present invention wherein the extraction temperature is selected to provide ratios within the ranges described above, particularly good sensory profiles may be attained when nicotine compositions prepared from liquid tobacco extracts are heated to generate an aerosol.
Suitable heating methods for carrying out the heating of the tobacco material would be known to the skilled person and include but are not limited to: dry distillation, hydrodistillation, vacuum distillation, flash distillation and thin film hydrodistillation.
The one or more heating steps are preferably carried out in an inert atmosphere. Preferably, a flow of an inert gas, such as nitrogen, is passed through the tobacco material during the heating step. In some cases, a flow of a combination of an inert gas with water or steam may be used. The addition of water or steam to the tobacco during extraction has been found to increase yield of extracted components. However, excess addition of water or steam leads to processing difficulties such as stickiness of the tobacco material.
The volatile tobacco compounds are released into the flow of inert gas during the heating step such that the inert gas (or combination of inert gas with water or steam) acts as a carrier for the volatile components. The inert gas flow rate may be optimised based on the scale and geometry of the extraction chamber. A relatively high flow rate of inert gas may advantageously improve the efficiency of extraction from the tobacco material.
In general, upon heating the tobacco material, any moisture present in the tobacco material is also released with the volatile compounds, in the form of steam.
The flow of inert gas helps convey the steam generated by evaporation of the moisture content of the tobacco material and the volatile compounds—including, in particular, nicotine or flavour-associated compounds or both—out of the extraction equipment.
Further, use of a flow of inert gas, such as nitrogen, under light over-pressure in the extraction equipment has the benefit of preventing the presence of oxygen within the extraction equipment. This is desirable in that it prevents risk of any, even partial, combustion of the tobacco material during the heating step. Uncontrolled combustion of the tobacco material would clearly be undesirable as it would represent a major safety risk within the manufacturing environment. However, the inventors have found that even a limited, partial combustion of the tobacco material may lead to a decrease in the quality of the tobacco extract obtainable by the method, which would be undesirable.
Without wishing to be bound by theory, it is understood that, by preventing combustion of the tobacco material, the formation of any undesirable combustion by-products is also prevented. Further, as conditions that would be conducive to combustion of the tobacco material are prevented, the tobacco material is effectively heated under conditions that mimic, to an extent, conditions under which a tobacco-containing substrate (e.g. homogenised tobacco material) is typically heated in “heat-not-burn” articles. As a result, selective extraction of the flavour-bearing volatile species responsible for the taste consumers associate with heated tobacco is advantageously favoured.
Therefore, by carrying out the heating step in an inert atmosphere, the extraction efficiency, product quality and manufacturing safety are advantageously enhanced.
The heating of the tobacco material in a flow of inert gas has the additional benefit that the inert gas flow containing the volatile compounds may be more easily directed into a container containing an extraction solvent, such as a non-aqueous extraction liquid solvent.
Optionally, the heating step may be carried out under vacuum. This removes any oxygen present within the extraction chamber, which may advantageously prevent reaction of the tobacco material or volatile compounds generated upon heating of the tobacco material with oxygen. The removal of oxygen will also prevent any combustion of the tobacco material, as described above.
Methods according to the present invention may further comprise the 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 thought to be due to the turbulent flow that is set up within the extraction chamber as a result of the evaporation of the atomised water. As a result of the improved heat exchange, the inclusion of the step of spraying water into the extraction chamber during the heating step has been found to provide a further improvement in the nicotine yield, as well as an increase in the yield of certain desirable flavour compounds from the tobacco material.
The spray of atomised water may be generated and dispensed into the extraction chamber using any suitable means.
The flow rate at which the atomised water is sprayed into the extraction chamber may be adjusted, for example, depending upon the flow rate of the tobacco material within the extraction chamber. For example, the average flow rate at which the atomised water is sprayed into the extraction chamber may be between about 3 percent and about 30 percent of the flow rate of the tobacco material.
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.
Methods of atomising water would be known to the skilled person. In some embodiments, the water may be atomised in a flow of compressed inert gas, such as air. In other embodiments, the water may be atomised without a flow of gas, due to the pressure within the spray nozzle.
The liquid tobacco extract may be produced from a tobacco material consisting of a single type of natural tobacco. Alternatively, the tobacco material may comprise a blend of two or more types of natural tobaccos. The ratio of the different tobacco types may be adapted depending on 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 may be increased.
The term “natural tobacco” is used herein with reference to the present invention to describe any part of any plant member of the genus Nicotiana, including, but not limited to, leaves, midribs, stems and stalks. In particular, the natural tobacco may comprise flue-cured tobacco material, Burley tobacco material, Oriental tobacco material, Maryland tobacco material, dark tobacco material, dark-fired tobacco material, Rustica 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 may be whole (for example, whole tobacco leaves), shredded, cut or ground.
Where it is desired to produce a liquid tobacco extract from a combination of two of more different tobacco types, the tobacco types may be heated separately at different extraction temperatures within the defined range of 100 degrees Celsius to 160 degrees Celsius, or a mixture of the tobacco types may be heated together at a single extraction temperature within the range.
The tobacco material may be a solid tobacco material, such as a powder, leaf scraps or shreds, or intact leaf. Alternatively, the tobacco material may be a liquid tobacco material such as a dough, 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, cast tobacco, extruded tobacco or tobacco derived pellets.
Preferably, in the step of preparing the tobacco material, the tobacco is ground or cut in order to reduce the size of tobacco particles within the tobacco material. This may advantageously improve the homogeneity of heating of the tobacco material and the efficiency of the extraction.
The tobacco material may optionally be dried prior to the heating step in order to decrease the water content of the tobacco material. Drying of the tobacco material may be carried out by any suitable chemical or physical drying process. Alternatively, water may be added to the tobacco material prior to the heating step in order to increase the water content of the tobacco material.
In certain embodiments of the present invention, the step of preparing the tobacco material may comprise the step of impregnating the tobacco material with an aerosol former. When this impregnation of the tobacco material is carried out prior to the heating step, it may advantageously increase the amount of certain desirable tobacco compounds that are released from the tobacco material upon heating. For example, impregnation of the tobacco material with glycerin has been found to advantageously increase the amount of nicotine that is extracted from the tobacco material. In another example, impregnation of the tobacco material with a non-aqueous extraction solvent that is also an aerosol former, such as propylene glycol, vegetal glycerin, 1,3-propanediol, triacetin, or mixtures thereof has been found to advantageously increase the amount of flavour compounds that are extracted from the tobacco material.
In some embodiments, the tobacco material consists of natural tobacco that has not been subjected to any pre-treatment steps, for example, to adjust the water content. As such, a water content in the tobacco material may be about 10 to 20 percent by weight (water content typically found in natural tobacco material). In other embodiments, the tobacco material may comprise added water, as described above.
Alternatively or in addition, the tobacco material may comprise one or more additional ingredients, such as for example a non-aqueous solvent. An example of a suitable solvent is propylene glycol.
The tobacco material may thus comprise 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.
The water content in the tobacco starting material may be at least about 3 percent by weight. Preferably, the water content in the tobacco starting material is at least about 5 percent by weight. More preferably, the water content in the tobacco starting material is at least about 5 percent by weight. It will be appreciated that “the water content in the tobacco starting material” may include both water inherently present in the natural tobacco material as well as any added water.
The water content in the tobacco starting material may be less than or equal to about 60 percent by weight. Preferably, the water content in the tobacco starting material is less than or equal to about 20 percent by weight. More preferably, the water content in the tobacco starting material is less than or equal to about 12 percent by weight.
In some embodiments, the water content in the tobacco starting material may be from about 3 percent by weight to about 60 percent by weight, more preferably from about 3 percent by weight to about 20 percent by weight, even more preferably from about 3 percent by weight to about 12 percent by weight. In other embodiments, the water content in the tobacco starting material may be from about 5 percent by weight to about 60 percent by weight, more preferably from about 5 percent by weight to about 20 percent by weight, even more preferably from about 5 percent by weight to about 12 percent by weight. In further embodiments, the water content in the tobacco starting material may be from about 8 percent by weight to about 60 percent by weight, more preferably from about 8 percent by weight to about 20 percent by weight, even more preferably from about 8 percent by weight to about 12 percent by weight.
In some embodiments, 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 digested enzymatically 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.
The tobacco material may optionally be analysed prior to the heating step in order to determine the composition, for example, the content of reducing sugars of alkaloids. This information about the composition may helpfully be used to select an appropriate extraction temperature.
Methods according to the invention may further comprise the step of microwave heating the tobacco material during at least one step of the method. The tobacco material may be microwave heated during a pre-treatment step, prior to the heating step. Alternatively or in addition, the tobacco material may be microwave heated during the main heating step, either instead of conventional heating or in combination with conventional heating.
The inclusion of a microwave heating step in the extraction method of the present invention has been found to provide a further improvement in the extraction yield of nicotine.
During the heating of the tobacco material, the volatile compounds are released in gaseous form from the tobacco material. The volatile compounds are collected using any suitable technique. Where the tobacco material is heated in a flow of an inert gas, as described above, the volatile compounds are collected from the inert gas flow. Different collection methods would be well known to the skilled person.
In certain preferred embodiments, the step of collecting the volatile compounds uses an absorption technique in which the volatile compounds are trapped in a non-aqueous extraction liquid solvent. For example, an inert gas flow containing the volatile compounds may be directed into a container of a non-aqueous extraction liquid solvent. The non-aqueous extraction liquid solvent is preferably an aerosol former such as triacetin, glycerin, 1,3-propanediol, propylene glycol or combinations thereof. The use of an aerosol former as the liquid solvent is potentially beneficial because the aerosol former can be retained as a diluting agent in the final liquid tobacco extract. This means that an additional step of removing the non-aqueous extraction solvent is not necessarily required.
As used herein with reference to the present invention, the term “aerosol former” refers to a compound or mixture of compounds that, in use, facilitates formation of an aerosol, and that preferably is 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 glycerin; 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 retained at a temperature of less than 0 degrees Celsius in order to optimise the transfer of the volatile compounds into the liquid solvent. The non-aqueous extraction solvent is preferably retained at a temperature of no less than −10 degrees Celsius. Temperatures below such value may lead to undesirable freezing phenomena.
In alternative preferred embodiments, the step of collecting the volatile compounds may be carried out using a condensation technique in which the volatile compounds are condensed and the condensate of volatile compounds is collected. Condensation of the volatile compounds may be carried out using any suitable apparatus, for example, in a refrigerated column. Preferably, the condensate obtained is added to a liquid aerosol former, preferably propylene glycol.
The addition of a liquid aerosol former in the collection step, and particularly addition of propylene glycol, may advantageously prevent the condensed volatile compounds from splitting into two phases or forming an emulsion, as some tobacco constituents would tend to do. Without wishing to be bound by theory, the inventors have observed that the solubility of the tobacco constituents in the hydrolate (i.e. the aqueous fraction of the liquid, naturally derived tobacco extract) depends primarily on their polarity, on their concentration and on the pH of the hydrolate, which may vary depending on the tobacco type. As a result, an oily layer tends to form at the surface of the liquid, naturally derived tobacco extract, if the amount of aerosol former is not sufficient. Such oily material can aggregate at different locations on the trapping and desiccation equipment wherein the third and further steps of the method are carried out, respectively. The addition of a liquid aerosol former, such as propylene glycol, helps prevent the formation of such layer and favours homogenisation of the liquid, naturally derived tobacco extract. This, in turn, helps prevent any loss of desirable flavour-associated compounds during the fourth (desiccation) step, during which such compounds may undesirably deposit on the equipment surfaces.
In addition, the liquid aerosol former advantageously helps trap the flavour-associated compounds independent of their polarity and volatility. Further, during any subsequent drying step, the liquid aerosol former helps prevent loss of the most volatile fraction, as well as favour the selective removal of excess water from the liquid, naturally derived tobacco extract to obtain the concentrated tobacco extract.
Use of propylene glycol as the aerosol former for the collection step has the further advantage that, by reducing the water activity of aqueous solutions, propylene glycol exerts an anti-microbial activity. By adjusting the content of propylene glycol in the liquid tobacco extract, it is therefore also possible to ensure that the extract substantially does not undergo any microbial activity.
As a further alternative, the step of collecting the volatile compounds may 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.
In the method of the present invention, the next step is the formation of a liquid tobacco extract from the collected volatile compounds. The nature of this step may depend upon the collection method. The “collected volatile compounds” will typically comprise a solution of the tobacco derived volatile compounds in a liquid solvent or carrier.
Where 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 comprise greater 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 comprise greater than about 30 percent by weight of the non-aqueous extraction solvent based on the weight of the liquid tobacco extract or greater than about 35 percent by weight of non-aqueous extraction solvent based on the weight of the liquid tobacco extract.
The liquid tobacco extract may comprise less than or equal to about 65 percent of non-aqueous extraction solvent based on the weight of the liquid tobacco extract. In some embodiments, the liquid tobacco extract may comprise less than or equal to 60 percent of non-aqueous extraction solvent based on the weight of the liquid tobacco extract or less than or equal to 55 percent of 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 further 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 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, glycerin, propylene glycol, 1,3-propanediol or a mixture thereof.
In preferred embodiments, in the liquid tobacco extract a ratio by weight of (6-ionone+6-damascenone) to (phenol) is at least about 0.25.
In preferred embodiments, in the liquid tobacco extract a ratio by weight of (furaneol+(2,3-diethyl-5-methylpyrazine)*100)) to (nicotine) is at least about 5×10⁻⁴.
Where 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 the volatile compounds in the liquid solvent in order to concentrate the solution. This may be carried out, for example, in order to arrive at a desired concentration of nicotine, or flavour compounds. Drying may be carried out using any suitable means, including but not limited to desiccation, molecular sieves, freeze drying, phase separation, distillation, membrane permeation, controlled crystallisation of water and filtering, reverse hygroscopicity, ultracentrifugation, liquid chromatography, reverse osmosis or chemical drying.
In preferred embodiments, the solution of the volatile compounds in a liquid solvent is concentrated by desiccation.
In other words, the solution of the volatile compounds in a liquid solvent is heated to evaporate at least some of the water and obtain a concentrated tobacco extract. To this purpose, the solution of the volatile compounds in a liquid solvent may be heated to a temperature and for a time such that the water content in the tobacco extract is reduced by at least about 60 percent.
The partially desiccated, concentrated tobacco extract can be considered the primary product of a method in accordance with the present invention. Depleted tobacco material, from which the volatile species and most of the moisture content have been extracted upon heating during the second step, may be considered a by-product of the method. Such depleted tobacco material may typically have a moisture content of about 1 to 5 percent by weight, preferably about 2 to 3 percent by weight.
In an embodiment, the solution of the volatile compounds in a liquid solvent is heated under vacuum, preferably at a temperature of at least about 70 degrees Celsius. In another embodiment, the solution of the volatile compounds in a liquid solvent is heated under a flow of air, preferably under a flow of air having relatively low humidity, at a temperature of at least about degrees Celsius. Thus, a naturally derived, concentrated tobacco extract can be obtained by a method in accordance with the invention. One such naturally derived, concentrated tobacco extract typically contains less than about 20 percent by weight of water.
Alternatively, where the volatile compounds are collected by condensation, the step of forming the liquid tobacco extract may comprise adding the condensate to a liquid solvent, such as an aerosol former.
Optionally, the step of forming the liquid tobacco extract comprises a filtering step.
Optionally, the step of forming the liquid tobacco extract comprises a blending step in which extracts derived from different tobacco materials are combined.
Optionally, the step of forming the liquid tobacco extract comprises 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.
In embodiments according to the second aspect of the present invention in which the alkaline treatment step is carried out on the residual tobacco material from the first heating step, two separate liquid tobacco extracts are produced during the extraction method: a first liquid tobacco extract from the first heating step of the tobacco material and a second liquid tobacco extract from the second heating step of the alkalised tobacco material. Preferably, such methods further comprise the step of combining the first liquid tobacco extract and the second liquid tobacco extract.
In certain embodiments, the nicotine from the second liquid tobacco extract may be isolated and at least a portion of the isolated nicotine may be added to the first liquid tobacco extract. This produces a liquid tobacco extract with an enhanced level of nicotine, without impacting the flavour characteristics of the first liquid tobacco extract.
The present invention further provides a liquid tobacco extract produced by a method according to the invention, as described in detail above. As described above, the method of the present invention advantageously produces a natural liquid tobacco extract that has a highly desirable ratio of desired tobacco compounds, such as nicotine and flavour compounds, to undesirable tobacco compounds.
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.
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 that obtained by a method in accordance with the invention 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. As the released compounds cool they condense to form an aerosol that is inhaled by the consumer.
Upon heating of a nicotine composition comprising the liquid tobacco extract according to the present invention, an aerosol is released containing the volatile compounds that have been collected from the tobacco material during the extraction process. By controlling the composition of the liquid tobacco extract through control of the parameters of the extraction parameter, it is possible to adjust the composition and characteristics of the resultant aerosol produced from the liquid tobacco extract and delivered to the consumer.
The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further nicotine. The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further flavour compounds. The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further furaneol. The nicotine composition may be a liquid tobacco extract resulting from an extraction process in accordance with the present invention, without the addition of further solvent.
Alternatively, the liquid tobacco extract may be subjected to additional processing steps to form the nicotine composition. Even when subjected to such additional steps, the nicotine composition may be formed without the need for addition of further nicotine or flavour compounds.
Preferably, the liquid tobacco extract may be concentrated in a desiccation step as described above to form a concentrated tobacco extract, and the concentrated tobacco extract may be used to form the nicotine composition.
Preferably, the concentrated tobacco extract comprises between 8 percent and 15 percent by weight water based on the weight of the concentrated tobacco extract.
The desiccation step provides a concentrated tobacco extract that may have a non-aqueous extraction solvent content of from about 65 percent to about 95 percent by weight, preferably from about 65 percent to 85 percent by weight, most preferably from about 75 percent to about 85 percent by weight. The non-aqueous extraction solvent is preferably triacetin, glycerin, propylene glycol, 1,3-propanediol or a mixture thereof.
The desiccation step provides 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, additional non-aqueous solvent may be added to the liquid tobacco extract or the concentrated tobacco extract to form the nicotine composition.
The nicotine composition may be a liquid nicotine composition or a gel nicotine composition.
The nicotine composition may comprise at least about 10 percent by weight of a liquid tobacco extract. Preferably, the nicotine composition comprises at least about 20 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises at least about 30 percent by weight of a liquid tobacco extract. In preferred embodiments, the nicotine 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 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 concentrated tobacco extract. The nicotine composition may comprise at least about 10 percent by weight of concentrated tobacco extract, at least about 20 percent by weight of concentrated tobacco extract, at least about 30 percent by weight of concentrated tobacco extract, at least about 40 percent by weight of concentrated tobacco extract, at least about 50 percent by weight of concentrated tobacco extract, preferably at least about 60 percent by weight of concentrated tobacco extract, more preferably at least about 70 percent by weight of concentrated tobacco extract, even more preferably at least about 75 percent by weight of concentrated tobacco extract, and most preferably at least about 80 percent by weight of concentrated tobacco extract.
In some embodiments, the nicotine composition comprises from about 40 percent by weight to about 95 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 percent by weight to about 95 percent by weight of a liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 50 percent by weight to about 95 percent by weight of a liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 percent by weight to about 95 percent by weight of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 percent by weight to about 95 percent by weight of a liquid tobacco extract, even more preferably from about 80 percent by weight to about 95 percent by weight of a liquid tobacco extract.
In some embodiments, the nicotine composition comprises from about 40 percent by weight to about 90 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 percent by weight to about 90 percent by weight of a liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 50 percent by weight to about 90 percent by weight of a liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 percent by weight to about 90 percent by weight of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 percent by weight to about 90 percent by weight of a liquid tobacco extract, even more preferably from about 80 percent by weight to about 90 percent by weight of a liquid tobacco extract.
In some embodiments, the nicotine composition comprises from about 40 percent by weight to about 85 percent by weight of a liquid tobacco extract. More preferably, the nicotine composition comprises from about 40 percent by weight to about 85 percent by weight of a liquid tobacco extract. Even more preferably, the nicotine composition comprises from about 85 percent by weight to about 90 percent by weight of a liquid tobacco extract. Most preferably, the nicotine composition comprises from about 60 percent by weight to about 85 percent by weight of a liquid tobacco extract. In some particularly preferred embodiments, the nicotine composition comprises from about 70 percent by weight to about 85 percent by weight of a liquid tobacco extract, even more preferably from about 80 percent by weight to about 85 percent by weight of a liquid tobacco extract.
The nicotine composition may comprise up to about 100 percent by weight of a liquid tobacco extract. In some embodiments, the nicotine composition may be formed directly from the liquid tobacco extract without the need for addition of additional non-aqueous solvent, flavourants or nicotine. That is to say, the nicotine composition may comprise 100 percent by weight of a liquid tobacco extract. In some embodiments, the liquid tobacco extract is concentrated tobacco extract, such that the nicotine composition may comprise 100 percent by weight of concentrated tobacco extract. In embodiments in which the nicotine composition comprises 100 percent by weight of a liquid tobacco extract or 100 percent by weight of concentrated tobacco extract, additional non-aqueous solvent is not present.
Alternatively, in some embodiments, the nicotine composition comprising liquid tobacco extract may comprise additional non-aqueous solvent. Additional non-aqueous solvent is non-aqueous solvent that has been added after the extraction step. Additional non-aqueous solvent is solvent that is supplemental to the non-aqueous extraction solvent present in the liquid tobacco extract. In embodiments in which the liquid tobacco extract is concentrated tobacco extract, the nicotine composition comprising concentrated tobacco extract may comprise additional non-aqueous solvent.
The additional non-aqueous solvent may be an aerosol former. Preferably, the additional non-aqueous solvent is triacetin, glycerin, propylene glycol, 1,3-propanediol or a mixture thereof.
In embodiments in which the nicotine composition comprises additional non-aqueous solvent, the nicotine composition may comprise 90 percent by weight or less of the additional non-aqueous solvent. Preferably, the nicotine composition comprises 80 percent by weight or less of the additional non-aqueous solvent. More preferably, the nicotine composition comprises 70 percent by weight or less of the additional non-aqueous solvent. In preferred embodiments, the nicotine composition comprises about 60 percent by weight or less of the additional non-aqueous solvent, more preferably about 50 percent by weight or less of the additional non-aqueous solvent, even more preferably about 40 percent by weight or less of the additional non-aqueous solvent. In particularly preferred embodiments, the nicotine 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 composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the nicotine content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the nicotine content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.
Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the nicotine content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.
In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the non-aqueous extraction solvent content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the non-aqueous extraction solvent content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the non-aqueous extraction solvent content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.
In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the water content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the water content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the water content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.
In a nicotine composition prepared by means of a method in accordance with the present invention at least 50 percent by weight based on the total weight of the nicotine composition of the desirable tobacco flavour species content in the nicotine composition may come from the tobacco extract as opposed to being added following extraction. In preferred embodiments, at least 80 percent by weight based on the total weight of the nicotine composition of the desirable tobacco flavour species content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction. Even more preferably, at least 90 percent by weight based on the total weight of the nicotine composition of the desirable tobacco flavour species content in the nicotine composition comes from the tobacco extract as opposed to being added following extraction.
The total content of non-aqueous solvent in the nicotine composition includes the non-aqueous extraction solvent and the additional non-aqueous solvent, if it is present. The nicotine composition may comprise a total content of non-aqueous solvent of from about 10 percent to about 95 percent by weight. The nicotine composition preferably comprises a total content of non-aqueous solvent of from about 50 percent to about 95 percent by weight, for example from about 65 percent to about 95 percent by weight, more preferably from about 70 to about 90 percent by weight, most preferably from about 80 percent to about 90 percent by weight. The non-aqueous solvent is preferably triacetin, glycerine, propylene glycol, 1,3-propanediol or a mixture thereof.
The nicotine composition may comprise a total content of propylene glycol of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of propylene glycol of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about 95 percent by weight, or from about 65 percent to about 95 percent by weight, from about 70 to about 90 percent by weight, or from about 80 percent to about 90 percent by weight.
The nicotine composition may comprise a total content of triacetin of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of triacetin of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about percent by weight, from about 70 to about 90 percent by weight or from about 65 percent to about 95 percent by weight, or from about 80 percent to about 90 percent by weight.
The nicotine composition may comprise a total content of glycerine of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of glycerine of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about percent by weight, or from about 65 percent to about 95 percent by weight, from about 70 to about 90 percent by weight or from about 80 percent to about 90 percent by weight.
The nicotine composition may comprise a total content of 1,3-propanediol of from about 10 percent to about 95 percent by weight. The nicotine composition may comprise a total content of 1,3-propanediol of from about 20 percent to about 95 percent by weight, such as from about 50 percent to about 95 percent by weight, or from about 65 percent to about 95 percent by weight, or from about 80 percent to about 90 percent by weight.
The nicotine composition of the present invention comprises at least 0.2 percent by weight of nicotine. More preferably, the nicotine content in the nicotine composition liquid tobacco extract is at least about 0.4 percent by weight. The nicotine composition may have a nicotine content of about 12 percent by weight or less, for example about 10 percent by weight or less, preferably about 8 percent by weight by weight or less, more preferably about 5 percent by weight or less, preferably about 3.6 percent by weight or less. Most preferably, the nicotine composition comprises between about 0.4 percent by weight and 3.6 percent by weight nicotine, based on the weight of the nicotine composition.
The nicotine composition may comprise between 1 percent and 85 percent by weight of water. The nicotine composition may comprise between 2 percent and 50 percent by weight of water. The nicotine composition may comprise between 3 percent and 30 percent by weight of water. The nicotine composition may comprise between 5 percent and 25 percent by weight of water. The nicotine composition may comprise between 8 percent and 20 percent by weight of water. The nicotine composition preferably comprises between 10 percent and 15 percent by weight water.
In some embodiments, the nicotine composition may comprise one or more water-soluble organic acids. As used herein with reference to the invention, the term “water-soluble organic acid” describes an organic acid having a water solubility at 20° C. of greater than or equal to about 500 mg/ml.
The one or more water-soluble organic acids may advantageously bind nicotine in the liquid tobacco extract through formation of one or nicotine salts. The one or more nicotine salts may advantageously be dissolved and stabilised in the water present in the liquid tobacco extract or in the non-aqueous solvent. This may advantageously reduce nicotine adsorption in the upper airways and enhance pulmonary nicotine delivery and retention as discussed above.
Preferably, the nicotine composition has a water-soluble organic acid content of greater than or equal to about 2 percent by weight. More preferably, the nicotine composition has a water-soluble organic acid content of greater than or equal to about 3 percent by weight.
The water-soluble organic acid may be acetic acid.
Exogenous acetic acid is acetic acid that has been added from a source other than the tobacco plant material, and is not acetic acid that is naturally present in the tobacco plant that has been separated from, removed from or derived from the tobacco plant material using the extraction processing conditions and techniques.
If acetic acid is added to the liquid tobacco extract to form the nicotine composition, then the total content of acetic acid in the nicotine composition, including both exogenous and endogenous acetic acid, is preferably from about 0.01 percent to about 8 percent by weight, for example between about 0.03 percent to about 8 percent by weight, from about 0.3 percent to about 8 percent by weight, from about 2 percent to about 8 percent by weight, or from about 3 percent to about 8 percent by weight. More preferably, the total acetic acid content is from about percent to about 6 percent by weight, for example between about 0.03 percent to about 6 percent by weight, from about 0.3 percent to about 6 percent by weight, from about from about 2 percent to about 6 percent by weight, or from about 3 percent to about 6 percent by weight.
Preferably, the nicotine composition has a water-soluble organic acid content of less than or equal to about 8 percent by weight. More preferably, the nicotine composition has a water-soluble organic acid content of less than or equal to about 6 percent by weight.
Preferably, the nicotine composition has a water-soluble organic acid content of between about 2 percent by weight and about 8 percent by weight. For example, the nicotine composition may have a water-soluble organic acid content of between about 2 percent by weight and about 6 percent by weight.
More preferably, the nicotine composition has a water-soluble organic acid content of between about 3 percent by weight and about 8 percent by weight. For example, the nicotine composition may have a water-soluble organic acid content of between about 3 percent by weight and about 6 percent by weight.
The nicotine composition may comprise one or more non-tobacco-derived flavourants. Suitable non-tobacco-derived flavourants include, but are not limited to, menthol.
Preferably, the nicotine composition has a non-tobacco-derived flavourant content of less than or equal to about 4 percent by weight. More preferably, the nicotine composition has a non-tobacco-derived flavourant content of less than or equal to about 3 percent by weight. For example, the liquid tobacco extract produced by the method of the present invention may be used to make a nicotine composition comprising between 10 and 20 mg of nicotine per millilitre, without the need for addition of nicotine.
A nicotine composition suitable for use in an aerosol-generating system may comprise the liquid tobacco extract produced in a method according to the present invention in combination with water and additional aerosol former. The nicotine composition may comprise, for example, between about 10 percent by weight and about 20 percent by weight of water.
A nicotine composition comprising the liquid tobacco extract according to the present invention may be provided in a cartridge for use in an aerosol-generating system. The cartridge may comprise an atomiser, configured to generate an aerosol from the nicotine composition. The atomiser may be a thermal atomiser, which is configured to heat the nicotine composition to generate an aerosol. The thermal atomiser may comprise, for example, a heater and a liquid transport element configured to transport the nicotine composition to the heater. The liquid transport element may comprise a capillary wick. Alternatively, the atomiser may be a non-thermal atomiser, which is configured to generate an aerosol from the nicotine composition by means other than heating. The non-thermal atomiser may be, for example, an impinging jet atomiser, an ultrasonic atomiser or a vibrating mesh atomiser.
The cartridge containing the nicotine composition formed from the liquid tobacco extract of the present invention may 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 may comprise a battery and control electronics.
An embodiment of the present invention will now be further described, by way of example only.

COMPARATIVE EXAMPLE

In a method according to the first aspect of the present invention, a tobacco material was cut to form tobacco shreds having maximum dimensions of 2.5 millimetres by 2.5 millimetres and the tobacco shreds were loaded into an extraction chamber, without compression. The tobacco material was sprayed with an aqueous solution of potassium carbonate to provide alkalised tobacco material having a pH of 9.5. The alkalised tobacco material was heated within the extraction chamber to a temperature of 140 degrees Celsius for a period of 120 minutes. During heating, a flow of nitrogen was passed through the extraction chamber at a flow rate of about 20 litres per minute. The tobacco flow rate was 30 kg per hour and the extraction chamber was rotated at a speed of 1 rpm in order to circulate the tobacco.
The volatile compounds released from the tobacco material during the heating step were collected by condensation at 0 degrees and added to a liquid solvent of propylene glycol.
The Nicotine Composition 1 shown in the table below is a liquid tobacco extract obtained directly from the extraction process according to the first aspect of the present invention, with the alkaline treatment step carried out prior to heating.
In a second, comparative extraction method, the tobacco material was extracted under the same conditions as described above, except that the alkaline treatment step was omitted. The second extraction method was therefore not according to the present invention. The Nicotine Composition 2 shown in the table below is a liquid tobacco extract obtained directly from this second extraction method.
Each of the nicotine compositions 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:


	Nicotine	Nicotine
	Composition 1	Composition 2

Nicotine extraction yield (g/kg	13.3	1.6
of dry tobacco)
2,3-diethyl-5-methylpyrazine	10.5	1.3
extraction yield (μg/kg of dry
tobacco)
2-ethyl-3,5-dimethylpyrazine	153	12
extraction yield (μg/kg of dry
tobacco)

As clearly shown in the table above, the inclusion of the alkaline treatment step in the method according to the first aspect of the invention provides a significant increase in the nicotine extraction yield compared to the methods in which the alkaline treatment step is omitted. As also shown in the table above, the inclusion of the alkaline treatment step provides a significantly improved extraction yield for certain pyrazine flavour compounds, including 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine.

Claims

1.-14. (canceled)

15. A method of producing a liquid tobacco extract, the method comprising the steps of:

preparing a tobacco material;

applying an alkaline solution to the tobacco material to produce an alkalised tobacco material;

heating the alkalised tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 30 minutes,

wherein the alkalised tobacco material is heated in a flow of inert gas or in a flow of a combination of an inert gas with water or steam, and

wherein a water content of the alkalised tobacco material, prior to the heating step, is between 10 percent by weight and 20 percent by weight;

condensing volatile compounds released from the alkalised tobacco material during the heating step and collecting condensate of the volatile compounds; and

forming a liquid tobacco extract comprising the condensate of the volatile compounds.

16. A method of producing a liquid tobacco extract, the method comprising the steps of:

preparing a tobacco material;

heating the tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius for at least 90 minutes;

collecting volatile compounds released from the tobacco material during the heating step;

forming a first liquid tobacco extract comprising the collected volatile compounds from the tobacco material;

applying an alkaline solution to the residual tobacco material from the heating step to produce an alkalised tobacco material;

heating the alkalised tobacco material at an extraction temperature of between 100 degrees Celsius and 160 degrees Celsius;

collecting volatile compounds released from the alkalised tobacco material during the heating step; and

forming a second liquid tobacco extract comprising the collected volatile compounds from the alkalised tobacco material.

17. The method according to claim 16, further comprising the step of combining the first liquid tobacco extract and the second liquid tobacco extract.

18. The method according to claim 16, further comprising the step of isolating nicotine from the second liquid tobacco extract and combining at least a portion of the isolated nicotine from the second liquid tobacco extract with the first liquid tobacco extract.

19. The method according to claim 16, wherein the tobacco material is heated in a flow of inert gas during at least one of the heating steps.

20. The method according to claim 15, wherein a pH of the alkalised tobacco material is water is at least 8.5.

21. The method according to claim 15, wherein a pH of the alkalised tobacco material is water is at least 9.0.

22. The method according to claim 16, wherein a pH of the alkalised tobacco material is water is at least 8.5.

23. The method according to claim 16, wherein a pH of the alkalised tobacco material is water is at least 9.0.

24. The method according to claim 15,

wherein the alkaline solution is sprayed onto the tobacco material, and

wherein the tobacco material is continuously agitated during the spraying.

25. The method according to claim 16,

wherein the alkaline solution is sprayed onto the tobacco material, and

wherein the tobacco material is continuously agitated during the spraying.

26. The method according to claim 15, wherein the alkaline solution is an aqueous solution of potassium carbonate.

27. The method according to claim 16, wherein the water content of the alkalised tobacco material prior to the heating step is between 10 percent and 20 percent by weight.

28. The method according to claim 15, wherein an amount of nicotine extracted from the alkalised tobacco material corresponds to at least 10 grams per kg of dry tobacco material.

29. The method according to claim 15, wherein the alkalised tobacco material is heated at an extraction temperature of between 135 degrees Celsius and 150 degrees Celsius.

30. The method according to claim 15, further comprising the step of spraying atomised water into an extraction chamber during the heating step.

31. The method according to claim 16, further comprising the step of spraying atomised water into an extraction chamber during the heating steps.

32. The method according to claim 15, further comprising the step of drying or concentrating the collected condensate of the volatile compounds.

33. The method according to claim 16, further comprising the step of drying or concentrating the collected volatile compounds.

34. A liquid tobacco extract produced by the method according to claim 15.