NOVEL AEROSOL-GENERATING SUBSTRATE

Description

[0001] The present invention relates to a novel aerosol-generating substrate comprising dried green tobacco material and to an aerosol-generating article comprising such a substrate. The present invention further relates to methods for producing dried green tobacco material for an aerosol-generating substrate.

[0002] In the production of combustible smoking articles, it is considered essential to use only tobacco material that has been sufficiently cured, since the use of uncured green tobacco leaves has been found to generate undesirable aromas and flavours upon burning of the tobacco leaves during smoking. By curing the tobacco material, through a process of drying and browning, the chemistry of the tobacco can be changed such that the undesirable aromas and flavours are minimised. Various methods of curing are used in the tobacco industry, including but not limited to flue curing, air curing and sun curing.

[0003] Aerosol-generating articles in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than combusted, are known in the art. Typically in such articles, an aerosol is generated by the transfer of heat from a heat source to a physically separate aerosol-generating substrate or material, which may be located in contact with, within, around, or downstream of the heat source. During use of the aerosol-generating article, volatile compounds are released from the substrate by heat transfer from the heat source and are entrained in air drawn through the article. As the released compounds cool, they condense to form an aerosol.

[0004] In the production of tobacco containing aerosol-generating substrates for such heated articles, cured tobacco material is used in order to produce an aerosol that replicates the aromas and flavours of the smoke from a combustible smoking article.

[0005] The tobacco curing process starts with the harvesting of the uncured green tobacco leaves, followed by a 'yellowing' phase lasting on average between 5 and 10 days, and finally a drying phase, or browning phase, which may last for up to 50 days. As the curing progresses, the tobacco leaves change from their initial green colour, first to yellow and finally to brown, as the chlorophyll within the leaves degrades. In each phase, the curing is continued until the desired moisture level in the tobacco leaves is achieved. In the uncured green tobacco leaves, the green colour is a result of a high level of chlorophyll within the leaves. In contrast, after curing, the tobacco leaves are found to contain only a very low level of chlorophyll and are brown in colour.

[0006] The curing processes that are used in the tobacco industry are relatively time consuming and often require the use of significant space and resources. Alternative, faster processes for drying the tobacco material without curing have been attempted. However, the resultant dried tobacco material has not been found to be suitable for use in combustible smoking articles, since the fast drying processes have not removed or sufficiently reduced the constituents producing the undesirable aromas and flavours upon burning of the tobacco.

[0007] US 2018/160723 provides a method for dehydrating green tobacco, snuff or tobacco additives by using light energy, microwave energy, or a combination of both, optionally under vacuum. The document also discloses the possibility to provide an aerosol generating substrate.

[0008] Chandrasinh Chavda Jaysinh: "PHYSIOLOGICAL BASIS OF HETEROSIS IN BIDI TOBACCO (nicotiana tabacum L.)",(1998) provides a scientific basis for selecting high-protein tobacco cultivars for downstream processing. It also supports the technical problem of preserving protein during tobacco dehydration.

[0009] US 2012/006343 discloses strands of homogenized tobacco material that have a mass-to-surface-area ratio of at least 0.09 mg/mm² and contain 12 %-25 % by weight of an aerosol former. The strands possess a density of roughly 1.1-1.5 g/cm³ and may include up to 10 % flavorant.

[0010] WO2016/156598 discloses a method for producing a heat not burn or aerosol generating articles comprising combining cellulose, and tobacco that are mixed with a binder, asparaginase (by dry weight), and optionally an aerosol former.

[0011] CN207355454 discloses a tobacco leaf drying device.

[0012] It would be desirable to provide a novel aerosol-generating substrate for a heated aerosol-generating article that can be produced in a more efficient way but without adversely affecting the sensory properties of the resultant aerosol generated upon heating of the substrate.

[0013] The present disclosure relates to an aerosol-generating substrate for an aerosol-generating article. The aerosol-generating substrate may comprise dried green tobacco material, an aerosol former and a binder.

[0014] The present disclosure also relates to an aerosol-generating article comprising a rod of such an aerosol-generating substrate.

[0015] The present disclosure also relates to the use of dried green tobacco leaves in the production of an aerosol-generating substrate for an aerosol-generating article.

[0016] The present disclosure also relates to a dried green tobacco material having a moisture content of between about 4 percent by weight and about 15 percent by weight and a chlorophyll level of at least 0.5 milligrams per gram.

[0017] According to the present invention there is provided an aerosol-generating substrate for a heated aerosol-generating article, the aerosol-generating substrate comprising dried green tobacco material, an aerosol former and a binder. The aerosol-generating substrate may be in the form of a homogenised tobacco material comprising between 5 percent by weight and 55 percent by weight of aerosol former.

[0018] According to the present invention there is further provided an aerosol-generating article comprising a rod of an aerosol-generating substrate, the aerosol-generating substrate comprising dried green tobacco material, an aerosol former and a binder. The aerosol-generating substrate may be in the form of a homogenised tobacco material comprising between 5 percent by weight and 55 percent by weight of aerosol former.

[0019] According to the present invention there is further provided the use of dried green tobacco material in the production of an aerosol-generating substrate for an aerosol-generating article, the aerosol-generating substrate comprising dried green tobacco material, an aerosol former and a binder.

[0020] According to the present invention there is further provided a dried green tobacco material having a moisture content of between about 4 percent by weight and about 15 percent by weight and a chlorophyll level of at least 0.5 milligrams per gram.

[0021] The present disclosure additionally relates to a method of producing dried green tobacco material for use in an aerosol-generating substrate as defined above. The method may comprise: providing uncured green tobacco leaves; drying the uncured green tobacco leaves until a moisture content of between 4 percent by weight and 15 percent by weight is achieved; and cutting or grinding the uncured green tobacco leaves to produce dried green tobacco material. The temperature, pressure and duration of the drying step may be selected such that the dried green tobacco material retains a chlorophyll level of at least 0.5 milligrams per gram.

[0022] According to the present invention there is provided a method of producing dried green tobacco material for use in an aerosol-generating substrate according to the present invention, as defined above. The method comprises: providing uncured green tobacco leaves; drying the uncured green tobacco leaves until a moisture content of between 4 percent by weight and 15 percent by weight is achieved; and cutting or grinding the uncured green tobacco leaves to produce dried green tobacco material. According to the invention, the temperature, pressure and duration of the drying step are preferably selected such that the dried green tobacco material retains a chlorophyll level of at least 0.5 milligrams per gram. Preferably, the drying step is carried out by heating the uncured green tobacco leaves to a temperature of between 75 degrees Celsius and 120 degrees Celsius for no more than 4 hours.

[0023] According to the present invention there is further provided a dried green tobacco material produced by a method according to the invention, as defined above.

[0024] According to the present invention there is further provided a method for producing homogenised tobacco material for use in an aerosol-generating substrate according to the invention, as defined above. The method comprises the steps of: combining dried green tobacco material, an aerosol former, a binder and water to form a slurry; casting the slurry on a surface to form a sheet of homogenised tobacco material; and drying the sheet of homogenised tobacco material, wherein the sheet of homogenised tobacco material has an aerosol former content of between 5 percent by weight and 55 percent by weight, on a dry weight basis.

[0025] Any references below to the aerosol-generating substrates and aerosol-generating articles of the present invention should be considered to be applicable to all aspects of the invention,

[0026] As used herein, the term "aerosol-generating article" refers to an article for producing an aerosol, wherein the article comprises an aerosol-generating substrate that is suitable and intended to be heated or combusted in order to release volatile compounds that can form an aerosol. A conventional cigarette is lit when a user applies a flame to one end of the cigarette and draws air through the other end. The localised heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite, and the resulting combustion generates an inhalable smoke. By contrast, in "heated aerosol-generating articles", an aerosol is generated by heating an aerosol-generating substrate and not by combusting the aerosol-generating substrate. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separate aerosol-generating substrate.

[0027] Also known are aerosol-generating articles that are adapted to be used in an aerosol-generating system that supplies the aerosol former to the aerosol-generating articles. In such a system, the aerosol-generating substrate in the aerosol-generating articles contain substantially less aerosol former relative to those aerosol-generating substrate which carries and provides substantially all the aerosol former used in forming the aerosol during operation.

[0028] As used herein, the term "aerosol-generating substrate" refers to a substrate capable of producing upon heating volatile compounds, which can form an aerosol. The aerosol generated from aerosol-generating substrates may be visible to the human eye or invisible and may include vapours (for example, fine particles of substances, which are in a gaseous state, that are ordinarily liquid or solid at room temperature) as well as gases and liquid droplets of condensed vapours.

[0029] The aerosol-generating substrate according to the present invention is particularly suitable for use in heated aerosol-generating articles, also known as heat-not-burn articles.

[0030] The aerosol-generating substrate according to the present invention may take any suitable form that is capable of generating an aerosol upon heating. Preferably, the aerosol-generating substrate is in the form of a homogenised tobacco material, such as a cast leaf, tobacco paper or reconstituted tobacco material. Alternatively, the aerosol-generating substrate may be in the form of a loose tobacco material such as a tobacco cut filler.

[0031] As used herein, the term "homogenised tobacco material" encompasses any plant material formed by the agglomeration of particles of tobacco plant. For example, sheets or webs of homogenised tobacco material for the aerosol-generating substrates of the present invention may be formed by agglomerating particles of plant material obtained by pulverising, grinding or comminuting tobacco plant material such as tobacco leaf lamina or tobacco leaf stems. The homogenised tobacco material may be produced by casting, extrusion, paper making processes or other any other suitable processes known in the art.

[0032] The term "dried green tobacco material" is used in the present specification to refer to material formed from tobacco leaves that have dried without being subjected to any curing process. The dried green tobacco material is therefore uncured. Such dried green tobacco material will typically retain its natural, green colour. The dried green tobacco material is formed from uncured green tobacco leaves that are dried as described below, in order to provide a desired moisture content, but without any curing. The dried green tobacco material may be from tobacco lamina, tobacco stems, or a combination thereof. The dried green tobacco material preferably has a moisture content of less than 15 percent by weight.

[0033] The term "uncured green tobacco leaves" is used in the present specification to refer to tobacco leaves that have not been subjected to any curing process after harvesting.

[0034] The present invention therefore provides a novel aerosol-generating substrate which is formed from at least a proportion of dried green tobacco material, which will typically be provided in combination with a proportion of cured tobacco material.

[0035] The inventors have surprisingly found that an aerosol-generating substrate for a heated aerosol-generating article can be formed using at least a proportion of dried green tobacco material in place of cured tobacco material, without adversely impacting the sensory properties of the resultant aerosol. In particular, it has been surprisingly found that when a substrate comprising dried green tobacco material is heated, rather combusted, to form an aerosol, the resultant aerosol does not have the unpleasant aromas or flavours that are generated when green tobacco material is used in a combustible smoking article, as described above.

[0036] The dried green tobacco material can advantageously be produced significantly more quickly and more efficiently than cured tobacco material, since it is possible to use a fast drying process to achieve the desired moisture content rather than a much slower curing process. The dried green tobacco material can also be produced naturally and organically, thereby providing a more sustainable process for generating aerosol-generating substrates.

[0037] Advantageously, the methods of drying uncured green tobacco leaves to produce a dried green tobacco material suitable for use in aerosol-generating substrate of the present invention can be applied to all tobacco types.

[0038] Furthermore, it has been found that the uncured green tobacco leaves can be dried and processed without destemming, which further improves the efficiency of production of the aerosol-generating substrate according to the invention.

[0039] The curing process of tobacco is known to affect the chemical composition of the tobacco and in particular, the levels of certain tobacco constituents which affect the flavour of the resultant aerosol generated from the aerosol-generating substrate and the levels of certain undesirable tobacco constituents. For example, it has been surprisingly found that as a result of the absence of a curing step in the production of dried green tobacco material, significantly reduced levels of asparagine, ammonia, free amino acids and total alkaloids are present than in a cured tobacco. This has an effect on the aerosol produced from an aerosol-generating substrate according to the invention, which will include less undesirable compounds such as acrylamide, hydrogen sulphide (H₂S) and methanethiol (MeSH). The inclusion of the dried green tobacco material in the aerosol-generating substrate therefore enables an improved aerosol to be generated upon heating of the substrate than is generated from a substrate with only cured tobacco and no dried green tobacco material.

[0040] The dried green tobacco material has also been found to have a significantly higher level of sugars than cured tobacco material. The presence of the sugars within the dried green tobacco material can advantageously facilitate the manufacture of the aerosol-generating substrate, for example, where the aerosol-generating substrate is formed using a cast leaf process, as described below. In particular, the relatively high level of sugar within the dried green tobacco material improves the flexibility of a sheet of aerosol-generating substrate formed from the dried green tobacco material.

[0041] As described above, when a tobacco material is not subjected to a curing process, it typically retains its natural, high level of chlorophyll and therefore its green colour. As a direct result of the inclusion of a proportion of dried green tobacco material in the aerosol-generating substrate of the present invention, the level of chlorophyll in the substrate is significantly higher than would be measured in a typical substrate formed from only cured tobacco. A cured tobacco is always brown in colour and has a low, often negligible amount of remaining chlorophyll, due to the degradation of the chlorophyll during curing.

[0042] Preferably, the homogenised tobacco material comprises at least 0.1 milligrams of chlorophyll per gram, on a dry weight basis. The presence of chlorophyll within the substrate at a level that is higher than 0.1 milligrams per gram of homogenised tobacco material, on a dry weight basis, is a clear indicator that dried green tobacco material has been incorporated.

[0043] Preferably, the homogenised tobacco material comprises at least about 0.2 milligrams of chlorophyll per gram, more preferably at least about 0.5 milligrams of chlorophyll per gram, more preferably at least about 1.0 milligrams of chlorophyll per gram, more preferably at least about 1.5 milligrams of chlorophyll per gram, more preferably at least about 2.0 milligrams of chlorophyll per gram, more preferably at least about 2.5 milligrams of chlorophyll per gram , more preferably at least about 3.0 milligrams of chlorophyll per gram, on a dry weight basis.

[0044] The higher the level of dried green tobacco material used in the homogenised tobacco material, the higher the level of chlorophyll that will be present in the aerosol-generating substrate. However, even with a relatively low proportion of dried green tobacco material forming the aerosol-generating substrate, the level of chlorophyll in the substrate will be considerably higher than would be present in a substrate formed from only cured tobacco material and without any dried green tobacco material.

[0045] The maximum level of chlorophyll within the aerosol-generating substrate will depend upon the type and amount of the dried green tobacco material within the aerosol-generating substrate. Typically, the homogenised tobacco material will comprise less than about 10.0 milligrams of chlorophyll per gram, or below about 8.0 milligrams of chlorophyll per gram, on a dry weight basis.

[0046] The dried green tobacco material used in the aerosol-generating substrate according to the invention preferably has a chlorophyll level of at least about 0.5 milligrams of chlorophyll per gram, more preferably at least about 1.0 milligrams of chlorophyll per gram, on a dry weight basis.

[0047] A preferred method for measuring the chlorophyll content of a sample of a homogenised tobacco material containing dried green tobacco material, or a sample of dried green tobacco material, may be found in "Lichtenthaler, HK and AR Wellburn (1983) Determinations of total carotenoids and chlorophylls a and b of leaf extracts in different solvents; Biochemical Society Transactions 11:591-592".

[0048] In this method, an aqueous 80 percent acetone extract is produced from a sample of the homogenised tobacco material and the absorbance of the extract at specific wavelengths is measured using a spectrophotometer. The level of chlorophyll a and chlorophyll b can then be calculated using equations set out below:



wherein A₆₆₃ is the measured absorbance at 663 nm and A₆₄₆ is the measured absorbance at 646 nm. The values of chlorophyll defined above in relation to the homogenised tobacco material of the present invention correspond to the total chlorophyll content, which is the sum of the content of chlorophyll a and chlorophyll b.

[0049] An alternative method for measuring the chlorophyll content of a sample of a homogenised tobacco material containing dried green tobacco material, or a sample of dried green tobacco material, may be found in in "Porra, RJ (2002) The chequered history of the development and use of simultaneous equations for the accurate determination of chlorophylls a and b; Photosynthesis Research 73: 149 - 156", which uses the alternative equations:



wherein A_663.6 is the measured absorbance at 663.6 nm and A_646.6 is the measured absorbance at 646.6 nm.

[0050] All of the other components of the dried green tobacco material that are referred to below may be measured by suitable GC-MS or LC-MS techniques, which would be well known to the skilled person.

[0051] The inclusion of dried green tobacco material in the aerosol-generating substrate of the present invention has been found to advantageously provide a decrease in the level of asparagine in the aerosol-generating substrate compared to an equivalent aerosol-generating substrate formed of cured tobacco material only.

[0052] Preferably, the homogenised tobacco material comprises no more than about 2.5 milligrams of asparagine per gram, more preferably no more than about 2.0 milligrams of asparagine per gram, more preferably no more than about 1.5 milligrams of asparagine per gram, more preferably no more than about 0.75 milligrams of asparagine per gram and most preferably no more than about 0.3 milligrams of asparagine per gram, on a dry weight basis.

[0053] The aerosol-generating substrate according to the invention will typically comprise a lower level of asparagine than an aerosol-generating substrate formed from cured tobacco material alone, since the level of asparagine in the tobacco leaf has been found to increase significantly during the curing process. For example, for certain tobacco types, the level of asparagine in the tobacco leaf has been found to be more than 20 times higher after curing of the tobacco leaf than for the uncured green tobacco leaf.

[0054] Preferably, the dried green tobacco material has not been genetically modified and in particular, it has not been genetically modified to reduce the asparagine content.

[0055] Preferably, the dried green tobacco material is substantially free from added asparaginase. The asparaginase that is present in the dried green tobacco material is therefore only that which is naturally present.

[0056] The level of asparagine in tobacco leaf varies depending upon the tobacco type. In certain preferred embodiments, the aerosol-generating substrate comprises dried green tobacco material which are derived from Burley tobacco. The dried green Burley tobacco material preferably comprise no more than about 0.5 milligrams of asparagine per gram, on a dry weight basis.

[0057] The asparagine content of a homogenised tobacco material can be measured using known spectroscopic techniques. A preferred method for determining asparagine content is described in MP 1471 rev 5 (2011) of Chelab Silliker S.r.l. Merieux Nutrisciences Company. Another suitable method is described in UNI EN ISO 13903:2005. A further suitable method is described in "Evaluation of the Content of Free Amino Acids in Tobacco by a New Liquid Chromatography- Tandem Mass Spectrometry Technique; S. C. Moldoveanu et al" (DOI: 10.1515/cttr-2015-0023).

[0058] The resultant aerosol generated from the aerosol-generating substrate according to the invention therefore advantageously has a significantly lower level of acrylamide, which is generated from the asparagine during heating of the aerosol-generating substrate.

[0059] Preferably, upon heating of the aerosol-generating substrate according to the invention under conditions according to Test Method A, an aerosol is generated comprising no more than about 4 micrograms of acrylamide per gram of substrate, preferably no more than about 3 micrograms of acrylamide per gram of substrate.

[0060] For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried green tobacco material from Burley tobacco, the level of acrylamide in the aerosol generated from the substrate when the substrate is heated according to Test Method A is preferably no more than about 4 micrograms of acrylamide per gram of substrate, preferably no more than about 3 micrograms of acrylamide per gram of substrate.

[0061] For the purposes of the invention, the aerosol-generating substrate is heated according to "Test Method A". In Test Method A, an aerosol-generating article incorporating the aerosol-generating substrate is heated in a Tobacco Heating System 2.2 holder (THS2.2 holder) under the Health Canada machine-smoking regimen. For the purposes of carrying out Test Method A, the aerosol-generating substrate is provided in an aerosol-generating article that is compatible with the THS2.2 holder.

[0062] The Tobacco Heating System 2.2 holder (THS2.2 holder) corresponds to the commercially available IQOS device (Philip Morris Products SA, Switzerland) as described in Smith et al., 2016, Regul. Toxicol. Pharmacol. 81 (S2) S82-S92. Aerosol-generating articles for use in conjunction with the IQOS device are also commercially available.

[0063] The Health Canada smoking regimen is a well-defined and accepted smoking protocol as defined in Health Canada 2000 - Tobacco Products Information Regulations SOR/2000-273, Schedule 2; published by Ministry of Justice Canada. The test method is described in ISO/TR 19478-1:2014. In a Health Canada smoking test, an aerosol is collected from the sample aerosol-generating substrate over 12 puffs with a puff volume of 55 millimetres, puff duration of 2 seconds and puff interval of 30 seconds, with all ventilation blocked if ventilation is present.

[0064] Thus, in the context of the present invention, the expression "upon heating of the aerosol-generating substrate according to Test Method A" means upon heating of the aerosol-generating substrate in a THS2.2 holder under the Health Canada machine-smoking regimen as defined in Health Canada 2000 - Tobacco Products Information Regulations SOR/2000-273, Schedule 2; published by Ministry of Justice Canada, the test method being described in ISO/TR 19478-1:2014.

[0065] For the purposes of analysis, the aerosol generated from the heating of the aerosol-generating substrate is trapped using suitable apparatus, depending upon the method of analysis that is to be used. The aerosol may then be analysed using known spectroscopy techniques, such as liquid chromatography or gas chromatography techniques, that would be known to the skilled person.

[0066] The inclusion of dried green tobacco material in the aerosol-generating substrate of the present invention has further been found to advantageously provide a decrease in the level of ammonia in the aerosol-generating substrate compared to an equivalent aerosol-generating substrate formed of cured tobacco material only.

[0067] Preferably, the homogenised tobacco material comprises no more than about 0.5 milligrams of ammonia per gram, more preferably no more than about 0.2 milligrams of ammonia per gram and most preferably no more than about 0.1 milligrams of ammonia per gram, on a dry weight basis. The aerosol-generating substrate according to the invention will typically comprise a lower level of ammonia than an aerosol-generating substrate formed from cured tobacco material alone, since the level of ammonia in the tobacco leaf has been found to increase significantly during the curing process. For example, for certain tobacco types, the level of ammonia in the tobacco leaf has been found to be more than 20 times higher after curing of the tobacco leaf than for the uncured green tobacco leaf.

[0068] The level of ammonia in a homogenised tobacco material can be measured according to the Coresta Recommended Method No. 79 "Determination of Ammonia in Tobacco and Tobacco Products by Ion Chromatographic Analysis" (March 2018).

[0069] The level of ammonia in tobacco leaf varies depending upon the tobacco type. In certain preferred embodiments, the aerosol-generating substrate comprises dried green tobacco material which is derived from Burley tobacco. The dried green Burley tobacco material preferably comprises no more than about 0.2 milligrams of ammonia per gram, on a dry weight basis.

[0070] The resultant aerosol generated from the aerosol-generating substrate according to the invention therefore advantageously has a significantly lower level of ammonia, which is volatilised from the aerosol-generating substrate during heating.

[0071] Preferably, upon heating of the aerosol-generating substrate according to the invention under conditions according to Test Method A, an aerosol is generated comprising no more than about 40 micrograms of ammonia per gram of substrate, preferably no more than about 30 micrograms of ammonia per gram of substrate.

[0072] For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried green tobacco material from Burley tobacco, the level of ammonia in the aerosol generated from the substrate when the substrate is heated according to Test Method A is preferably no more than about 40 micrograms of acrylamide per gram of substrate, preferably no more than about 30 micrograms of ammonia per gram of substrate.

[0073] The inclusion of dried green tobacco material in the aerosol-generating substrate of the present invention has further been found to advantageously provide a decrease in the level of total free amino acids in the aerosol-generating substrate compared to an equivalent aerosol-generating substrate formed of cured tobacco material only.

[0074] Preferably, the homogenised tobacco material comprises no more than about 12 milligrams of total free amino acids per gram, more preferably no more than about 8 milligrams of total free amino acids per gram and most preferably no more than about 6 milligrams of total free amino acids per gram, on a dry weight basis. The aerosol-generating substrate according to the invention will typically comprise a lower level of total free amino acids than an aerosol-generating substrate formed from cured tobacco material alone, since the level of total free amino acids in the tobacco leaf has been found to increase significantly during the curing process. For example, for certain tobacco types, the level of total free amino acids in the tobacco leaf has been found to be more than 5 times higher after curing of the tobacco leaf than for the uncured green tobacco leaf.

[0075] The level of total free amino acids in tobacco leaf varies depending upon the tobacco type. In certain preferred embodiments, the aerosol-generating substrate comprises dried green tobacco material which are derived from Burley tobacco. The dried green Burley tobacco material preferably comprises no more than about 20 milligrams of total free amino acids per gram, on a dry weight basis.

[0076] The resultant aerosol generated from the aerosol-generating substrate according to the invention therefore advantageously has a significantly lower level of hydrogen sulphide and methanethiol, which are generated from the free amino acids in the aerosol-generating substrate during heating.

[0077] Preferably, upon heating of the aerosol-generating substrate according to the invention under conditions according to Test Method A, an aerosol is generated comprising no more than about 6 micrograms of hydrogen sulphide per gram of substrate, preferably no more than about 5 micrograms of hydrogen sulphide per gram of substrate.

[0078] For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried green tobacco material from Burley tobacco, the level of hydrogen sulphide in the aerosol generated from the substrate when the substrate is heated according to Test Method A is preferably no more than about 6 micrograms of hydrogen sulphide per gram of substrate, preferably no more than about 5 micrograms of hydrogen sulphide per gram of substrate.

[0079] Preferably, upon heating of the aerosol-generating substrate according to the invention under conditions according to Test Method A, an aerosol is generated comprising no more than about 10 micrograms of methanethiol per gram of substrate, preferably no more than about 9 micrograms of methanethiol per gram of substrate.

[0080] For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried green tobacco material from Burley tobacco, the level of methanethiol in the aerosol generated from the substrate when the substrate is heated according to Test Method A is preferably no more than about 10 micrograms of methanethiol per gram of substrate, preferably no more than about 9 micrograms of methanethiol per gram of substrate.

[0081] A reduction in the level of hydrogen sulphide and methanediol in the aerosol generated from aerosol-generating substrate of the present invention is advantageous, since these compounds are known to be responsible for undesirable sulphurous odours during heating.

[0082] The inclusion of dried green tobacco material in the aerosol-generating substrate of the present invention has further been found to advantageously provide a decrease in the level of certain TSNAs (tobacco specific nitrosamines) in the aerosol-generating substrate compared to an equivalent aerosol-generating substrate formed of cured tobacco material only.

[0083] For example, the aerosol-generating substrate according to the invention will typically comprise a lower level of NNN (N-Nitrosonornicotine) than an aerosol-generating substrate formed from cured tobacco material alone, since the level of NNN and other TSNAs in the tobacco leaf has been found to increase significantly during the curing process. For certain tobacco types, the level of NNN in the tobacco leaf has been found to be more than 5 times higher after curing of the tobacco leaf than for the uncured green tobacco leaf.

[0084] The level of NNN in tobacco leaf varies depending upon the tobacco type. In certain preferred embodiments, the aerosol-generating substrate comprises dried green tobacco material which is derived from Burley tobacco. The dried green Burley tobacco material preferably comprise no more than about 500 nanograms of NNN per gram, on a dry weight basis.

[0085] The resultant aerosol generated from the aerosol-generating substrate according to the invention therefore advantageously has a significantly lower level of NNN, which is volatilised from the aerosol-generating substrate during heating.

[0086] The inclusion of dried green tobacco material in the aerosol-generating substrate of the present invention has been found to provide a significant increase in the level of phosphatidylethanolamine (PE) in the aerosol-generating substrate compared to an equivalent aerosol-generating substrate formed of cured tobacco material only. PE is an extra-chloroplastic lipid found in plant membranes. The presence of PE above a certain threshold level is clearly indicative of the inclusion of dried green tobacco material within an aerosol-generating substrate. The level of some of the PE molecular species, including PE 36:6, PE 34:3, PE 36:5 and PE 34:2, has been found to be at least 8 times higher, in some cases at least 10 times higher, in the dried green tobacco material than in cured tobacco material of the same tobacco type.

[0087] The term "PE 36:6" refers to a PE molecular species having 36 carbons in the two acyl chains and 6 double bonds in total. The same terminology applies to the other molecular species listed above.

[0088] Preferably, the aerosol produced from an aerosol-generating substrate according to the present invention during Test Method A further comprises at least about 0.1 micrograms of nicotine per gram of the substrate, more preferably at least about 1 microgram of nicotine per gram of the substrate, more preferably at least about 2 micrograms of nicotine per gram of the substrate. Preferably, the aerosol comprises up to about 10 micrograms of nicotine per gram of the substrate, more preferably up to about 7.5 micrograms of nicotine per gram of the substrate, more preferably up to about 4 micrograms of nicotine per gram of the substrate. For example, the aerosol may comprise between about 0.1 micrograms and about 10 micrograms of nicotine per gram of the substrate, or between about 1 microgram and about 7.5 micrograms of nicotine per gram of the substrate, or between about 2 micrograms and about 4 micrograms of nicotine per gram of the substrate. In some embodiments of the present invention, the aerosol may contain zero micrograms of nicotine.

[0089] Various methods known in the art can be applied to measure the amount of nicotine in the aerosol.

[0090] The aerosol produced from an aerosol-generating substrate according to the invention during Test Method A may further comprise at least about 5 milligrams of aerosol former per gram of aerosol-generating substrate, or at least about 10 milligrams of aerosol per gram of the substrate or at least about 15 milligrams of aerosol former per gram of the substrate. Alternatively or in addition, the aerosol may comprises up to about 30 milligrams of aerosol former per gram of the substrate, or up to about 25 milligrams aerosol former per gram of the substrate, or up to about 20 milligrams aerosol former per gram of the substrate. For example, the aerosol may comprise between about 5 milligrams and about 30 milligrams of aerosol former per gram of the substrate, or between about 10 milligrams and about 25 milligrams of aerosol former per gram of the substrate, or between about 15 milligrams and about 20 milligrams of aerosol former per gram of the substrate. In alternative embodiments, the aerosol may comprise less than 5 milligrams of aerosol former per gram of substrate. This may be appropriate, for example, if an aerosol former is provided separately within the aerosol-generating article or aerosol-generating device.

[0091] Suitable aerosol formers for use in the present invention are set out below.

[0092] Various methods known in the art can be applied to measure the amount of aerosol former in the aerosol.

[0093] Preferably, the homogenised tobacco material of aerosol-generating substrates according to the invention comprises at least about 1 percent by weight of dried green tobacco material, on a dry weight basis. Preferably, the homogenised tobacco material comprises at least about 2 percent by weight of dried green tobacco material, more preferably at least about 4 percent by weight of dried green tobacco material, more preferably at least about 6 percent by weight of dried green tobacco material, more preferably at least about 8 percent by weight of dried green tobacco material, more preferably at least about 10 percent by weight of dried green tobacco material, on a dry weight basis.

[0094] The homogenised tobacco material comprises between 10 percent and 50 percent by weight of dried green tobacco material, on a dry weight basis.

[0095] In certain particularly preferred embodiments of the invention, the homogenised tobacco material comprises between about 10 percent by weight and about 30 percent by weight of dried green tobacco material, on a dry weight basis.

[0096] The homogenized tobacco material comprises cured tobacco material or aerosol generating plant material.

[0097] In a first alternative of the invention, the homogenised tobacco material may comprise dried green tobacco material in combination with cured tobacco material, as described below.

[0098] Alternatively to cured tobacco material, the homogenised tobacco material may comprise aerosol-generating plant material derived from one or more plants including but not limited to cannabis, tea, ginger, eucalyptus, clove, peppermint, star anise, rosemary, chamomile, thyme and dill seed.

[0099] In the following description of the invention, the term "plant material" is used to refer collectively to the aerosol-generating plant material that is used to form the aerosol-generating substrate. The plant material may consist substantially of dried green tobacco material or may be a mixture of dried green tobacco material with cured tobacco material or other aerosol-generating plant material as defined above. Preferably, the plant material is in the form of plant particles which may consist substantially of dried green tobacco particles or may be a mixture of dried green tobacco particles with cured tobacco particles. The term "plant material" does not include any inert plant material incorporated into the aerosol-generating substrate and which does not contribute to the aerosol generated upon heating of the aerosol-generating substrate.

[0100] Preferably, the homogenised tobacco material according to the invention further comprises at least about 1 percent by weight of cured tobacco material. For example, the homogenised tobacco material may comprise at least about 2 percent by weight of cured tobacco material, or at least about 4 percent by weight of cured tobacco material, or at least about 6 percent by weight of cured tobacco material, or at least about 8 percent by weight of cured tobacco material, or at least about 10 percent by weight of cured tobacco material, on a dry weight basis.

[0101] The homogenised tobacco material may comprise up to about 75 percent by weight of cured tobacco material, or up to about 70 percent by weight of cured tobacco material, or at least about 65 percent by weight of cured tobacco material, or at least 60 percent by weight of cured tobacco material, or at least about 55 percent by weight of cured tobacco material, or at least about 50 percent by weight of cured tobacco material, on a dry weight basis.

[0102] The cured tobacco material is preferably in the form of cured tobacco particles.

[0103] The term "cured tobacco material" is used in the present specification to refer to material derived from tobacco plants that has been subjected to a known curing process for at least 5 days. Cured tobacco material, such as cured tobacco leaves, will typically be brown in colour and have a chlorophyll level of no more than 0.25 milligrams per gram, on a dry weight basis.

[0104] The ratio of dried green tobacco material to cured tobacco material in the homogenised tobacco material may be varied depending on the desired content of the dried green tobacco material in the homogenised tobacco material. Preferably, the ratio of dried green tobacco material to cured tobacco material in the homogenised tobacco material is no more than 1 to 1 (1:1). In such embodiments, the weight amount of cured tobacco material in the homogenised tobacco material is equal to or greater than the weight amount of dried green tobacco material in the homogenised tobacco material, on a dry weight basis.

[0105] With reference to the present invention, the term "tobacco material", whether referring to the dried green tobacco material or cured tobacco material, may be material of any plant member of the genus Nicotiana. The term "tobacco particles" encompasses ground or powdered tobacco leaf lamina, ground or powdered tobacco leaf stems, tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco. In a preferred embodiment, the tobacco material is substantially all derived from tobacco leaf lamina. By contrast, isolated nicotine and nicotine salts are compounds derived from tobacco but are not considered tobacco material for purposes of the invention and are not included in the percentage of plant material.

[0106] The tobacco material may be prepared from one or more varieties of tobacco plants. Any type of tobacco may be used in a blend. Examples of tobacco types that may be used for the dried green tobacco material include, but are not limited to, Burley tobacco, Maryland tobacco, Oriental tobacco, Virginia tobacco, and other speciality tobaccos. Examples of tobacco types that may be used for the cured tobacco types include, but are not limited to, sun-cured tobacco, flue-cured tobacco, Burley tobacco, Maryland tobacco, Oriental tobacco, Virginia tobacco, and other speciality tobaccos.

[0107] Burley tobacco plays a significant role in many tobacco blends. Burley tobacco has a distinctive flavour and aroma and also has an ability to absorb large amounts of casing.

[0108] Oriental is a type of tobacco which has small leaves, and high aromatic qualities. However, Oriental tobacco has a milder flavour than, for example, Burley. Generally, therefore, Oriental tobacco is used in relatively small proportions in tobacco blends.

[0109] Flue-curing is a method of curing tobacco, which is particularly used with Virginia tobaccos. During the flue-curing process, heated air is circulated through densely packed tobacco. During a first stage, the tobacco leaves turn yellow and wilt. During a second stage, the laminae of the leaves are completely dried. During a third stage, the leaf stems are completely dried.

[0110] Kasturi, Madura and Jatim are subtypes of sun-cured tobacco that can be used.

[0111] The dried green tobacco material or the cured tobacco material may comprise a blend of different tobacco types.

[0112] The tobacco material may have a nicotine content of at least about 2.5 percent by weight, based on dry weight. More preferably, the tobacco material may have a nicotine content of at least about 3 percent, even more preferably at least about 3.2 percent, even more preferably at least about 3.5 percent, most preferably at least about 4 percent by weight, based on dry weight. The curing process does not appear to affect the nicotine level of tobacco leaf to a significant extent and therefore these values apply to both the dried green tobacco material and the cured tobacco material, where present.

[0113] Nicotine may optionally be incorporated into the aerosol-generating substrate although this would be considered as a non-tobacco material for the purposes of the invention. The nicotine may comprise one or more nicotine salts selected from the list consisting of nicotine lactate, nicotine citrate, nicotine pyruvate, nicotine bitartrate, nicotine benzoate, nicotine pectate, nicotine alginate, and nicotine salicylate. Nicotine may be incorporated in addition to a tobacco with low nicotine content, or nicotine may be incorporated into an aerosol-generating substrate that has a reduced or zero tobacco content.

[0114] Preferably, the homogenised tobacco material comprises at least about 0.1 mg of nicotine per gram of the substrate, on a dry weight basis. More preferably, the homogenised tobacco material comprise at least about 0.5 mg of nicotine per gram of the substrate, more preferably at least about 1 mg of nicotine per gram of the substrate, more preferably at least about 1.5 mg of nicotine per gram of the substrate, more preferably at least about 2 mg of nicotine per gram of the substrate, more preferably at least about 3 mg of nicotine per gram of the substrate, more preferably at least about 4 mg of nicotine per gram of the substrate, more preferably at least about 5 mg of nicotine per gram of the substrate, on a dry weight basis.

[0115] Preferably, the homogenised tobacco material comprises up to about 50 mg of nicotine per gram of the substrate, on a dry weight basis. More preferably, the homogenised tobacco material comprises up to about 45 mg of nicotine per gram of the substrate, more preferably up to about 40 mg of nicotine per gram of the substrate, more preferably up to about 35 mg of nicotine per gram of the substrate, more preferably up to about 30 mg of nicotine per gram of the substrate, more preferably up to about 25 mg of nicotine per gram of the substrate, more preferably up to about 20 mg of nicotine per gram of the substrate, on a dry weight basis.

[0116] For example, the homogenised tobacco material may comprise between about 0.1 mg and about 50 mg of nicotine per gram of the substrate, or between about 0.5 mg and about 45 mg of nicotine per gram of the substrate, or between about 1 mg and about 40 mg of nicotine per gram of the substrate, or between about 2 mg and about 35 mg of nicotine per gram of the substrate, or between about 5 mg and about 30 mg of nicotine per gram of the substrate, or between about 10 mg and about 25 mg of nicotine per gram of the substrate, or between about 15 mg and about 20 mg of nicotine per gram of the substrate, on a dry weight basis. In certain preferred embodiments of the invention, the homogenised tobacco material comprises between about 1 mg and about 20 mg of nicotine per gram of the substrate, on a dry weight basis.

[0117] The defined ranges of nicotine content for the homogenised tobacco material include all forms of nicotine which may be present in the homogenised tobacco material, including nicotine intrinsically present in tobacco material as well as nicotine that has optionally been added separately to the homogenised tobacco material, for example, in the form of a nicotine salt.

[0118] The nicotine content of a homogenised tobacco material can be measured according to the hexane method described in Coresta Recommended Method No. 62 "Determination of Nicotine in Tobacco and Tobacco Products by Gas Chromatographic Analysis" (April 2020).

[0119] The homogenised tobacco material preferably comprises at least about 55 percent by weight of the plant material including dried green tobacco material, as described above, more preferably at least about 60 percent by weight of the plant material and more preferably at least about 65 percent by weight of the plant material, on a dry weight basis. The homogenised tobacco material preferably comprises no more than about 95 percent by weight of the plant material, more preferably no more than about 90 percent by weight of the plant material and more preferably no more than about 85 percent by weight of the plant material, on a dry weight basis. For example, the homogenised tobacco material may comprise between about 55 percent and about 95 percent by weight of the plant material, or between about 60 percent and about 90 percent by weight of the plant material, or between about 65 percent and about 85 percent by weight of the plant material, on a dry weight basis. In one particularly preferred embodiment, the homogenised tobacco material comprises about 75 percent by weight of the plant material, on a dry weight basis.

[0120] In certain preferred embodiments, the total weight amount plant material is no more than about 75 percent by weight on a dry weight basis.

[0121] The plant material is therefore combined with one or more other components to form the homogenised tobacco material.

[0122] As defined above, the homogenised tobacco material further comprises an aerosol former. Upon volatilisation, an aerosol former can convey other vaporised compounds released from the homogenised tobacco material upon heating, such as nicotine and flavourants, in an aerosol. The aerosolisation of a specific compound from an homogenised tobacco material is determined not solely by its boiling point. The quantity of a compound that is aerosolised can be affected by the physical form of the substrate, as well as by the other components that are also present in the substrate. The stability of a compound under the temperature and time frame of aerosolisation will also affect the amount of the compound that is present in an aerosol.

[0123] Suitable aerosol formers for inclusion in the homogenised tobacco material are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, propylene glycol, 1,3-butanediol and glycerol; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The homogenised tobacco material may comprise a single aerosol former, or a combination of two or more aerosol formers.

[0124] If the substrate is intended for use in an aerosol-generating article for an electrically-operated aerosol-generating system having a heating element, the aerosol former is preferably glycerol.

[0125] The amount of aerosol former may be adapted depending on the composition of the homogenised tobacco material, such as the type or amount of the plant material, in order to achieve an aerosol having the desired levels of flavour compounds from the plant material. The amount of aerosol former may also be adapted depending on the way in which it is intended to heat the aerosol-generating substrate during use and in particular, the temperature to which the homogenised tobacco material will be heated during heating of the aerosol-generating article in an associated aerosol-generating device.

[0126] The homogenised tobacco material has an aerosol former content of between 5 percent and 55 percent by weight on a dry weight basis, such as between about 10 percent and about 45 percent by weight on a dry weight basis, or between about 15 percent and about 40 percent by weight on a dry weight basis.

[0127] The aerosol former content may be between about 5 percent and about 30 percent by weight, on a dry weight basis. For example, in homogenised tobacco materials according to certain preferred embodiments of the invention, the aerosol former content is preferably between about 5 percent and about 30 percent by weight, more preferably between about 10 percent and about 25 percent by weight, more preferably between about 15 percent and about 20 percent by weight on a dry weight basis.

[0128] Alternatively, the aerosol former content may be between about 15 percent and about 55 percent by weight, on a dry weight basis. For example, in homogenised tobacco materials according to alternative preferred embodiments of the invention, the aerosol former content is preferably between about 15 percent and about 55 percent by weight, more preferably between about 25 percent and about 50 percent by weight, more preferably between about 35 percent and about 45 percent by weight on a dry weight basis.

[0129] The aerosol former may act as a humectant in the homogenised tobacco material.

[0130] As defined above, the homogenised tobacco material further comprises an exogenous binder to alter the mechanical properties of the plant material, wherein the binder is included in the homogenised tobacco material during manufacturing as described herein. Suitable exogenous binders would be known to the skilled person and include but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders, for example, cellulose ethers such as hydroxypropyl cellulose, carboxymethyl cellulose (CMC), hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodium-alginate, agar and pectins; and combinations thereof. Preferably, the binder comprises guar gum.

[0131] Preferably, the binder is present in an amount of from about 1 percent to about 10 percent by weight, preferably in an amount of from about 2 percent to about 9 percent by weight, more preferably in amount of between about 3 percent by weight and about 8 percent by weight, on a dry weight basis.

[0132] In certain embodiments, the homogenised tobacco material preferably comprises between about 1 percent and about 10 percent by weight of binder, on a dry weight basis, wherein the binder is most preferably guar gum. For example, in aerosol-generating articles according to a first preferred embodiment of the invention, the homogenised tobacco material preferably comprises between about 1 percent and about 10 percent by weight of binder, on a dry weight basis, wherein the binder is most preferably guar gum.

[0133] In certain embodiments, the homogenised tobacco material preferably comprises between about 2 percent and about 10 percent by weight of binder, on a dry weight basis, wherein the binder is most preferably cellulose ether. For example, in the aerosol-generating articles according to a second preferred embodiment, the homogenised tobacco material preferably comprises between about 2 percent and about 10 percent by weight of binder, on a dry weight basis, wherein the binder is preferably cellulose ether. Particularly preferably, the binder is carboxymethyl cellulose (CMC).

[0134] In addition, the homogenised tobacco material of any embodiment may optionally further comprise additional cellulose. For example, the homogenised tobacco material may comprise between about 5 percent by weight and about 50 percent by weight of additional cellulose.

[0135] As used herein, the term "additional cellulose" encompasses any cellulosic material incorporated into the homogenised tobacco material which does not derive from the tobacco material provided in the homogenised tobacco material. The additional cellulose is therefore incorporated in the homogenised tobacco material in addition to the tobacco material, as a separate and distinct source of cellulose to any cellulose intrinsically provided within the tobacco material. The additional cellulose will typically derive from a different plant to the tobacco material. Preferably, the additional cellulose is in the form of an inert cellulosic material, which is sensorially inert and therefore does not substantially impact the organoleptic characteristics of the aerosol generated from the homogenised tobacco material. For example, the additional cellulose is preferably a tasteless and odourless material.

[0136] The additional cellulose may consist of one type of cellulose material, or may be a combination of different types of cellulose material which provide different properties, as described in more detail below.

[0137] The additional cellulose incorporated in the homogenised tobacco material according to the present invention is thought to provide additional structure and reinforcement to bind and support the plant material and aerosol former within the homogenised tobacco material.

[0138] The incorporation of additional cellulose has been found to be particularly beneficial in homogenised tobacco materials in which the binder comprises cellulose ether, as described above. The combination of cellulose ether and additional cellulose material, at certain defined levels and within defined ratios, as set out below, has been advantageously found to provide an homogenised tobacco material having an improved tensile strength and homogeneity.

[0139] Preferably, the ratio of additional cellulose material to cellulose ether in the homogenised tobacco material is at least 2.

[0140] Preferably, the additional cellulose comprises cellulose powder. The term "cellulose powder" is used herein to refer to a refined cellulose material in powder form that has been derived from cellulose fibres. Preferably, the cellulose powder is formed of particles with an average particle size of less than 100 microns. The cellulose powder may be in the form of microcrystalline cellulose. A suitable cellulose powder for use in the present invention is available as Microcrystalline Cellulose Type SK-105 or SK-101, or Cellulose Powder Type M-60 from Gumix International, Inc. of New Jersey.

[0141] Preferably, the amount of cellulose powder corresponds to at least about 5 percent by weight of the homogenised tobacco material, more preferably at least about 6 percent by weight of the homogenised tobacco material, more preferably at least about 7 percent by weight of the homogenised tobacco material and more preferably at least about 8 percent by weight of the homogenised tobacco material, on a dry weight basis.

[0142] The amount of cellulose powder may be adapted above this minimum level depending upon the weight amount of the other components within the homogenised tobacco material and in particular, depending upon the weight amount of the plant material. In certain embodiments, the cellulose powder may replace a proportion of the plant material within the homogenised tobacco material, without a significant impact on the characteristics of the aerosol generated.

[0143] Preferably, the amount of cellulose powder corresponds to no more than about 45 percent by weight of the homogenised tobacco material, more preferably no more than about 40 percent by weight of the homogenised tobacco material, on a dry weight basis.

[0144] In certain embodiments, for example, embodiments having a relatively high level of plant material in the homogenised tobacco material, the amount of cellulose powder may be relatively low. In such embodiments, the amount of cellulose powder may be between about 5 percent by weight and about 15 percent by weight of the homogenised tobacco material, or between about 6 percent by weight and about 12 percent by weight of the homogenised tobacco material, or between about 7 percent by weight and about 11 percent by weight of the homogenised tobacco material, or between about 8 percent by weight and about 10 percent by weight of the homogenised tobacco material, on a dry weight basis.

[0145] In other embodiments, for example, embodiments having a relatively low level of aerosol-generating plant material in the homogenised tobacco material, the amount of cellulose powder may be relatively high. In such embodiments, the amount of cellulose powder may be between about 15 percent by weight and about 45 percent by weight of the homogenised tobacco material, or between about 20 percent by weight and about 40 percent by weight of the homogenised tobacco material, or between about 25 percent by weight and about 35 percent by weight of the homogenised tobacco material, on a dry weight basis.

[0146] Preferably, where the homogenised tobacco material comprises cellulose ether and cellulose powder, the ratio by weight of cellulose powder to cellulose ether in the homogenised tobacco material is at least about 1.5, i.e. the amount of cellulose powder is at least 1.5 times the amount of cellulose ether. More preferably, the ratio by weight of cellulose powder to cellulose ether in the homogenised tobacco material is at least about 1.6, more preferably at least about 1.8.

[0147] Alternatively or in addition to the cellulose powder, the additional cellulose may comprise cellulose fibres. The term "cellulose fibres" is used herein to refer to fibres obtained directly from plant-based materials, wherein each fibre has a length that is significantly greater than its width. The cellulose fibres preferably have a fibre length of at least 400 microns. Suitable cellulose fibres for use in the present invention include, for example, wood pulp fibres. A suitable source of cellulose fibres for use in the present invention is available as ECF Bleached Hardwood Kraft Pulp from Storaenso, Sweden.

[0148] The cellulose fibres may advantageously act as mechanical reinforcement in the homogenised tobacco material forming the aerosol-generating substrate of aerosol-generating articles according to the invention. The cellulose fibres may improve the binding of the plant material in the homogenised tobacco material and provide an improvement in tensile strength, in particular when combined with a cellulose ether binder.

[0149] Preferably, the amount of cellulose fibres corresponds to at least about 3 percent by weight of the homogenised tobacco material, based on dry weight, more preferably at least about 4 percent by weight of the homogenised tobacco material, more preferably at least about 5 percent by weight homogenised tobacco material and more preferably at least about 6 percent by weight homogenised tobacco material, on a dry weight basis.

[0150] Preferably, the amount of cellulose fibres corresponds to no more than about 12 percent by weight of the homogenised tobacco material, more preferably at least about 11 percent by weight of the homogenised tobacco material, more preferably at least about 10 percent by weight of the homogenised tobacco material, more preferably at least about 8 percent by weight of the homogenised tobacco material, on a dry weight basis.

[0151] For example, the homogenised tobacco material may comprise between about 3 percent by weight and about 12 percent by weight of cellulose fibres, or between about 4 percent by weight and about 11 percent by weight of cellulose fibres, or between about 5 percent by weight and about 10 percent by weight of cellulose fibres, or between about 6 percent by weight and about 8 percent by weight of cellulose fibres, on a dry weight basis.

[0152] Preferably, where the homogenised tobacco material comprises cellulose ether and cellulose fibres, the ratio by weight of cellulose fibres to cellulose ether in the homogenised tobacco material is at least about 0.5, i.e. the amount of cellulose powder is at least half the amount of cellulose ether. More preferably, the ratio by weight of cellulose fibres to cellulose ether in the homogenised tobacco material is at least about 0.75, more preferably at least about 1.

[0153] In preferred embodiments, the additional cellulose comprises cellulose powder and cellulose fibres. In such embodiments, the ratio by weight of cellulose powder to cellulose fibres is preferably at least about 1.5, more preferably at least about 1.75, more preferably at least about 2.

[0154] Preferably, the amount of additional cellulose provided in the homogenised tobacco material is adapted such that the total amount of additional cellulose and plant material corresponds to no more than 75 percent by weight of the homogenised tobacco material. Preferably, at least about 25 percent by weight of the homogenised tobacco material is therefore provided by other components, including the cellulose ether and aerosol former.

[0155] In the aerosol-generating articles according to the second preferred embodiment of the present invention, the homogenised tobacco material preferably comprises between about 2 percent and about 10 percent by weight of cellulose ether and between about 5 percent by weight and about 50 percent by weight of additional cellulose, on a dry weight basis. Preferably, the ratio of the additional cellulose to cellulose ether is at least 2.

[0156] In addition to the components described above, the homogenised tobacco material may optionally further comprise one or more lipids to facilitate the diffusivity of volatile components (for example, aerosol formers and nicotine), wherein the lipid is included in the homogenised plant material during manufacturing as described herein. Suitable lipids for inclusion in the homogenised tobacco material include, but are not limited to: medium-chain triglycerides, cocoa butter, palm oil, palm kernel oil, mango oil, shea butter, soybean oil, cottonseed oil, coconut oil, hydrogenated coconut oil, candellila wax, carnauba wax, shellac, sunflower wax, sunflower oil, rice bran, and Revel A; and combinations thereof.

[0157] Alternatively or in addition, the homogenised tobacco material may further comprise a pH modifier.

[0158] Alternatively or in addition, the homogenised tobacco material may further comprise fibres to alter the mechanical properties of the homogenised tobacco material, wherein the fibres are included in the homogenised tobacco material during manufacturing as described herein. Suitable exogenous fibres for inclusion in the homogenised tobacco material are known in the art and include fibres formed from non-tobacco material and non-tobacco material, including but not limited to: cellulose fibres; soft-wood fibres; hard-wood fibres; jute fibres and combinations thereof. Exogenous fibres derived from tobacco and/or tobacco can also be added. Any fibres added to the homogenised tobacco material are not considered to form part of the "plant material" as defined above. Prior to inclusion in the homogenised tobacco material, fibres may be treated by suitable processes known in the art including, but not limited to: mechanical pulping; refining; chemical pulping; bleaching; sulphate pulping; and combinations thereof. A fibre typically has a length greater than its width.

[0159] Suitable fibres typically have lengths of greater than 400 micrometres and less than or equal to 4 mm, preferably within the range of 0.7 mm to 4 mm. Preferably, the fibres are present in an amount of at least about 2 percent by weight, based on the dry weight of the substrate. The amount of fibres in the homogenised tobacco material may depend upon the type of material and in particular, the method that is used to produce the homogenised tobacco material. In some embodiments, the fibres may be present in an amount of between about 2 percent by weight and about 15 percent by weight, most preferably at about 4 percent by weight, based on the dry weight of the substrate. For example, this level of fibres may be present where the homogenised tobacco material is in the form of cast leaf. In other embodiments, the fibres may be present in an amount of at least about 30 percent by weight, or at least about 40 percent by weight. For example, this higher level of fibres is likely to be provided where the homogenised tobacco material is a tobacco paper formed in a papermaking process.

[0160] In preferred embodiments of the invention, the homogenised tobacco material comprises between about 5 percent by weight and about 30 percent by weight of aerosol former and between about 1 percent by weight and about 10 percent by weight of binder, on a dry weight basis. In such embodiments, the homogenised tobacco material preferably further comprises between about 2 percent by weight and about 15 percent by weight of fibres. Particularly preferably, the binder is guar gum.

[0161] The homogenised tobacco material is preferably in the form of a solid or a gel. However, in some embodiments the homogenised tobacco material may be in the form of a solid that is not a gel. Preferably, the homogenised tobacco material is not in the form of a film.

[0162] The homogenised tobacco material can be provided in any suitable form. For example, the homogenised tobacco material may be in the form of one or more sheets. As used herein with reference to the invention, the term "sheet" describes a laminar element having a width and length substantially greater than the thickness thereof.

[0163] Alternatively or in addition, the homogenised tobacco material may be in the form of a plurality of pellets or granules.

[0164] Alternatively or in addition, the homogenised tobacco material may be in a form that can fill a cartridge or a shisha consumable, or that can be used in a shisha device. The invention includes a cartridge or a shisha device that contains an homogenised tobacco material.

[0165] Alternatively or in addition, the homogenised tobacco material may be in the form of a plurality of strands, strips or shreds. As used herein, the term "strand" describes an elongate element of material having a length that is substantially greater than the width and thickness thereof. The term "strand" should be considered to encompass strips, shreds and any other homogenised tobacco material having a similar form. The strands of homogenised tobacco material may be formed from a sheet of homogenised tobacco material, for example by cutting or shredding, or by other methods, for example, by an extrusion method.

[0166] In some embodiments, the strands may be formed in situ within the homogenised tobacco material as a result of the splitting or cracking of a sheet of homogenised tobacco material during formation of the homogenised tobacco material, for example, as a result of crimping. The strands of homogenised tobacco material within the homogenised tobacco material may be separate from each other. Alternatively, each strand of homogenised tobacco material within the homogenised tobacco material may be at least partially connected to an adjacent strand or strands along the length of the strands. For example, adjacent strands may be connected by one or more fibres. This may occur, for example, where the strands have been formed due to the splitting of a sheet of homogenised tobacco material during production of the homogenised tobacco material, as described above.

[0167] Preferably, the homogenised tobacco material is in the form of one or more sheets of homogenised tobacco material. In various embodiments of the invention, the one or more sheets of homogenised tobacco material may be produced by a casting process. In various embodiments of the invention, the one or more sheets of homogenised tobacco material may be produced by a paper-making process. The one or more sheets as described herein may each individually have a thickness of between 100 micrometres and 600 micrometres, preferably between 150 micrometres and 300 micrometres, and most preferably between 200 micrometres and 250 micrometres. Individual thickness refers to the thickness of the individual sheet, whereas combined thickness refers to the total thickness of all sheets that make up the aerosol-generating substrate. For example, if the aerosol-generating substrate is formed from two individual sheets, then the combined thickness is the sum of the thickness of the two individual sheets or the measured thickness of the two sheets where the two sheets are stacked in the aerosol-generating substrate.

[0168] The one or more sheets as described herein may each individually have a grammage of between about 100 g/m² and about 300 g/m², or between about 100 g/m² and about 200 g/m².

[0169] The one or more sheets as described herein may each individually have a density of from about 0.3 g/cm³ to about 1.3 g/cm³, and preferably from about 0.7 g/cm³ to about 1.0 g/cm³.

[0170] In embodiments of the present invention in which the aerosol-generating substrate comprises one or more sheets of homogenised tobacco material, the sheets are preferably in the form of one or more gathered sheets. As used herein, the term "gathered" denotes that the sheet of homogenised tobacco material is convoluted, folded, or otherwise compressed or constricted substantially transversely to the cylindrical axis of a plug or a rod. The step of "gathering" the sheet may be carried out by any suitable means which provides the necessary transverse compression of the sheet.

[0171] As used herein, the term "longitudinal" refers to the direction corresponding to the main longitudinal axis of the aerosol-generating article, which extends between the upstream and downstream ends of the aerosol-generating article. During use, air is drawn through the aerosol-generating article in the longitudinal direction. The term "transverse" refers to the direction that is perpendicular to the longitudinal axis. As used herein, the term "length" refers to the dimension of a component in the longitudinal direction and the term "width" refers to the dimension of a component in the transverse direction. For example, in the case of a plug or rod having a circular cross-section, the maximum width corresponds to the diameter of the circle.

[0172] As used herein, the term "plug" denotes a generally cylindrical element having a substantially polygonal, circular, oval or elliptical cross-section. As used herein, the term "rod" refers to a generally cylindrical element of substantially polygonal cross-section and preferably of circular, oval or elliptical cross-section. A rod may have a length greater than or equal to the length of a plug. Typically, a rod has a length that is greater than the length of a plug. A rod may comprise one or more plugs, preferably aligned longitudinally.

[0173] As used herein, the terms "upstream" and "downstream" describe the relative positions of elements, or portions of elements, of the aerosol-generating article in relation to the direction in which the aerosol is transported through the aerosol-generating article during use. The downstream end of the airflow path is the end at which aerosol is delivered to a user of the article.

[0174] The one or more sheets of homogenised tobacco material may be gathered transversely relative to the longitudinal axis thereof and circumscribed with a wrapper to form a continuous rod or a plug. The continuous rod may be severed into a plurality of discrete rods or plugs. The wrapper may be a paper wrapper or a non-paper wrapper, as described in more detail below. tobacco

[0175] Alternatively, the one or more sheets of homogenised tobacco material may be cut into strands as referred to above. In such embodiments, the aerosol-generating substrate comprises a plurality of strands of the homogenised tobacco material. The strands may be used to form a plug. Typically, the width of such strands is at least about 0.2 mm, or at least about 0.5 mm. Preferably, the width of such strands is no more than about 5 mm, or about 4mm, or about 3 mm, or about 1.5 mm. For example, the width of the strands may be between about 0.25 mm and about 5 mm, or between about 0.25 mm and about 3 mm, or between about 0.5 mm and about 1.5 mm.

[0176] The length of the strands is preferably greater than about 5 mm, for example, between about 5 mm to about 20 mm, or between about 8 mm to about 15 mm, or about 12 mm. Preferably, the strands have substantially the same length as each other. The length of the strands may be determined by the manufacturing process whereby a rod is cut into shorter plugs and the length of the strands corresponds to the length of the plug. The strands may be fragile which may result in breakage especially during transit. In such cases, the length of some of the strands may be less than the length of the plug.

[0177] The plurality of strands preferably extend substantially longitudinally along the length of the aerosol-generating substrate, aligned with the longitudinal axis. Preferably, the plurality of strands are therefore aligned substantially parallel to each other.

[0178] The strands of homogenised tobacco material preferably each have a mass to surface area ratio of at least about 0.02 milligrams per square millimetre, more preferably at least about 0.05 milligrams per square millimetre. Preferably the strands of homogenised tobacco material each have a mass to surface area ratio of no more than about 0.2 milligrams per square millimetre, more preferably no more than about 0.15 milligrams per square millimetre. The mass to surface area ratio is calculated by dividing the mass of the strand of homogenised tobacco material in milligrams by the geometric surface area of the strand of homogenised tobacco material in square millimetres.

[0179] The one or more sheets of homogenised tobacco material may be textured through crimping, embossing, or perforating. The one or more sheets may be textured prior to gathering or prior to being cut into strands. Preferably, the one or more sheets of homogenised tobacco material are crimped prior to gathering, such that the homogenised tobacco material may be in the form of a crimped sheet, more preferably in the form of a gathered crimped sheet. As used herein, the term "crimped sheet" denotes a sheet having a plurality of substantially parallel ridges or corrugations usually aligned with the longitudinal axis of the article.

[0180] In one embodiment, the aerosol-generating substrate may be in the form of a single plug of homogenised tobacco material. In other embodiments, the aerosol-generating substrate may be in the form of two or more plugs of homogenised tobacco material, wherein the plugs of homogenised tobacco material may be formed from the same or a different homogenised tobacco material.

[0181] The aerosol-generating substrates according to the invention may be produced by various methods including paper making, casting, dough reconstitution, extrusion or any other suitable process. Preferably, the aerosol-generating substrate is a homogenised tobacco material.

[0182] Preferably, the homogenised tobacco material is in the form of "cast leaf". The term "cast leaf" is used herein to refer to a sheet product made by a casting process that is based on casting a slurry comprising tobacco particles and a binder (for example, guar gum) onto a supportive surface, such as a belt conveyor, drying the slurry and removing the dried sheet from the supportive surface. An example of the casting or cast leaf process is described in, for example, US-A-5,724,998 for making cast leaf tobacco. In a cast leaf process, particulate plant materials are mixed with a liquid component, typically water, to form a slurry. Other added components in the slurry may include fibres, a binder and an aerosol former. The particulate plant materials may be agglomerated in the presence of the binder. The slurry is cast onto a supportive surface and dried to form a sheet of homogenised tobacco material.

[0183] In certain preferred embodiments, the homogenised tobacco material used in articles according to the present invention is produced by casting. Homogenised tobacco material made by the casting process typically comprise agglomerated particulate plant material.

[0184] In a cast-leaf process, because substantially all the soluble fraction is kept within the plant material, most flavours are advantageously preserved. Additionally, energy-intensive paper-making steps are avoided.

[0185] In one preferred embodiment of the present invention, to form homogenised tobacco material, a mixture comprising particulate plant material, water, a binder, and an aerosol former is formed. A sheet is formed from the mixture, and the sheet is then dried. Preferably the mixture is an aqueous mixture. As used herein, "dry weight" refers to the weight of a particular non-water component relative to the sum of the weights of all non-water components in a mixture, expressed as a percentage. The composition of aqueous mixtures may be referred to by "percentage dry weight." This refers to the weight of the non-water components relative to the weight of the entire aqueous mixture, expressed as a percentage.

[0186] The mixture may be a slurry. As used herein, a "slurry" is a homogenised aqueous mixture with a relatively low dry weight. A slurry as used in the method herein may preferably have a dry weight of between 5 percent and 60 percent.

[0187] Alternatively, the mixture may be a dough. As used herein, a "dough" is an aqueous mixture with a relatively high dry weight. A dough as used in the method herein may preferably have a dry weight of at least 60 percent, more preferably at least 70 percent.

[0188] Slurries comprising greater than 30 percent dry weight and doughs may be preferred in certain embodiments of the present method.

[0189] The step of mixing the particulate plant material, water and other optional components may be carried out by any suitable means. For mixtures of a low viscosity, that is, some slurries, it is preferred that mixing is performed using a high energy mixer or a high shear mixer. Such mixing breaks down and distributes the various phases of the mixture homogeneously. For mixtures of a higher viscosity, that is, some doughs, a kneading process may be used to distribute the various phases of the mixture homogeneously.

[0190] Methods according to the present invention may further comprise the step of vibrating the mixture to distribute the various components. Vibrating the mixture, that is for example vibrating a tank or silo where a homogenised mixture is present, may help the homogenization of the mixture, particularly when the mixture is a mixture of low viscosity, that is, some slurries. Less mixing time may be required to homogenize a mixture to the target value optimal for casting if vibrating is performed as well as mixing.

[0191] If the mixture is a slurry, a web of homogenised tobacco material is preferably formed by a casting process comprising casting the slurry on a supportive surface, such as a belt conveyor. The method for production of a homogenised tobacco material comprises the step of drying said cast web to form a sheet. The cast web may be dried at room temperature or at an ambient temperature of at least about 60 degrees Celsius, more preferably at least about 80 degrees Celsius for a suitable length of time. Preferably, the cast web is dried at an ambient temperature of no more than 200 degrees Celsius, more preferably no more than about 160 degrees Celsius. For example, the cast web may be dried at a temperature of between about 60 degrees Celsius and about 200 degrees Celsius, or between about 80 degrees Celsius and about 160 degrees Celsius. Preferably, the moisture content of the sheet after drying is between about 5 percent and about 15 percent based on the total weight of the sheet. The sheet may then be removed from the supportive surface after drying. The cast sheet has a tensile strength such that it can be mechanically manipulated and wound or unwound from a bobbin without breakage or deformation.

[0192] If the mixture is a dough, the dough may be extruded in the form of a sheet, strands, or strips, prior to the step of drying the extruded mixture. Preferably, the dough may be extruded in the form of a sheet. The extruded mixture may be dried at room temperature or at a temperature of at least about 60 degrees Celsius, more preferably at least about 80 degrees Celsius for a suitable length of time. Preferably, the extruded mixture is dried at an ambient temperature of no more than 200 degrees Celsius, more preferably no more than about 160 degrees Celsius. For example, the extruded mixture may be dried at a temperature of between about 60 degrees Celsius and about 200 degrees Celsius, or between about 80 degrees Celsius and about 160 degrees Celsius. Preferably, the moisture content of the extruded mixture after drying is between about 5 percent and about 15 percent based on the total weight of the sheet. A sheet formed from dough requires less drying time and/or lower drying temperatures as a result of significantly lower water content relative to a web formed from a slurry.

[0193] After the sheet has been dried, the method may optionally comprise a step of coating a nicotine salt, preferably along with an aerosol former, onto the sheet, as described in the disclosure of WO-A-2015/082652.

[0194] After the sheet has been dried, methods according to the invention may optionally comprise a step of cutting the sheet into strands, shreds or strips for the formation of the aerosol-generating substrate as described above. The strands, shreds or strips may be brought together to form a rod of the aerosol-generating substrate using suitable means. In the formed rod of aerosol-generating substrate, the strands, shreds or strips may be substantially aligned, for example, in the longitudinal direction of the rod. Alternatively, the strands, shreds or strips may be randomly oriented in the rod.

[0195] Methods according to the present invention may optionally further comprise a step of winding the sheet onto a bobbin, after the drying step.

[0196] The homogenised tobacco material of the present invention may alternatively be produced by a paper-making method for producing sheets of homogenised plant material in the form of a plant "paper". Plant paper refers to a reconstituted plant sheet formed by a process in which a plant feedstock is extracted with a solvent to produce an extract of soluble plant compounds and an insoluble residue of fibrous plant material, and the extract is recombined with the insoluble residue. The extract may optionally be concentrated or further processed before being recombined with the insoluble residue. The insoluble residue may optionally be refined and combined with additional plant fibres before being recombined with the extract. In the method according to the present invention, the plant feedstock will comprise particles of tobacco, optionally in combination with particles of tobacco.

[0197] In more detail, the method of producing a plant paper comprises a first step of mixing a plant material and water to form a dilute suspension. The dilute suspension comprises mostly separate cellulose fibres. The suspension has a lower viscosity and a higher water content than the slurry produced in the casting process. This first step may involve soaking, optionally in the presence of an alkali, such as sodium hydroxide, and optionally applying heat.

[0198] The method further comprises a second step of separating the suspension into an insoluble portion containing the insoluble residue of fibrous plant material and a liquid or aqueous extract comprising soluble plant compounds. The water remaining in the insoluble residue of fibrous plant material may be drained through a screen, acting as a sieve, such that a web of randomly interwoven fibres may be laid down. Water may be further removed from this web by pressing with rollers, sometimes aided by suction or vacuum.

[0199] After removal of the aqueous portion and water, the insoluble residue is formed into a sheet. Preferably, a generally flat, uniform sheet of plant fibres is formed.

[0200] Preferably, the method further comprises the steps of concentrating the extract of soluble plant compounds that were removed from the sheet and adding the concentrated extract into the sheet of insoluble residue of fibrous plant material to form a sheet of homogenised plant material. Alternatively or in addition, a soluble plant substance or concentrated plant substance from another process can be added to the sheet. The extract or concentrated extract may be from another variety of the same species of plant, or from another species of plant.

[0201] This process, as described in US-A-3,860,012, has been used with tobacco to make reconstituted tobacco products, also known as tobacco paper.

[0202] In certain preferred embodiments, the homogenised tobacco material used in articles according to the present invention is produced by a paper-making process as defined above. In such embodiments, the homogenised tobacco material is in the form of a tobacco paper.

[0203] Homogenised tobacco material produced by such a process is referred to as tobacco paper. Homogenised tobacco material made by the paper-making process is distinguishable by the presence of a plurality of fibres throughout the material, visible by eye or under a light microscope, particularly when the paper is wetted by water. In contrast, homogenised tobacco material made by the casting process comprises less fibres than paper and tends to dissociate into a slurry when it is wetted.

[0204] Other known processes that can be applied to producing homogenised tobacco materials are dough reconstitution processes of the type described in, for example, US-A-3,894,544; and extrusion processes of the type described in, for example, in GB-A-983,928. Typically, the densities of homogenised tobacco materials produced by extrusion processes and dough reconstitution processes are greater than the densities of the homogenised tobacco materials produced by casting processes.

[0205] Preferably, the aerosol-generating substrate of aerosol-generating articles according to the invention comprises at least about 200 mg of homogenised tobacco material, more preferably at least about 220 mg of homogenised tobacco material and more preferably at least about 250 mg of homogenised tobacco material.

[0206] Aerosol-generating articles according to the invention comprise a rod, comprising the homogenised tobacco material in one or more plugs. The rod of aerosol-generating substrate may have a length of from about 5 mm to about 120 mm. For example, the rod may preferably have a length of between about 10 and about 45 mm, more preferably between about 10 mm and 15 mm, most preferably about 12 mm. In alternative embodiments, the rod preferably has a length of between about 30 mm and about 45 mm, or between about 33 mm and about 41 mm. Where the rod is formed of a single plug of homogenised tobacco material, the plug has the same length as the rod.

[0207] The rod of aerosol-generating substrate may have an external diameter of between about 5 mm and about 10 mm, depending on their intended use. For example, in some embodiments, the rod may have an external diameter of between about 5.5 mm and about 8 mm, or between about 6.5 mm and about 8 mm. The "external diameter" of the rod of aerosol-generating substrate corresponds to the diameter of the rod including any wrappers.

[0208] The rod of aerosol-generating substrate of the aerosol-generating articles according to the invention is preferably circumscribed by one or more wrappers along at least a part of its length. The one or more wrappers may include a paper wrapper or a non-paper wrapper, or both. Suitable paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to: cigarette papers; and filter plug wraps. Suitable non-paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to sheets of homogenised tobacco materials.

[0209] In certain embodiments of the invention, the aerosol-generating substrate is circumscribed along at least a part of its length by a thermally conductive sheet material, for example, a metallic foil, such as aluminium foil or a metallised paper. The metallic foil or metallised paper serves the purpose of conducting heat rapidly throughout the aerosol-generating substrate. In addition, the metallic foil or metallised paper may serve to prevent the ignition of the aerosol-generating substrate in the event that the consumer attempts to light it. Furthermore, during use, the metallic foil or metallised paper may prevent odours produced upon heating of the outer wrapper from entering the aerosol generated from the aerosol-generating substrate. For example, this may be a problem for aerosol-generating articles having an aerosol-generating substrate that is heated externally during use in order to generate an aerosol. Alternatively, or in addition, a metallised wrapper may be used to facilitate detection or recognition of the aerosol-generating article when it is inserted into an aerosol-generating device during use. The metallic foil or metallised paper may comprise metal particles, such as iron particles.

[0210] The one or more wrappers circumscribing the aerosol-generating substrate preferably have a total thickness of between about 0.1 mm and about 0.9 mm.

[0211] The internal diameter of the rod of aerosol-generating substrate is preferably between about 3 mm and about 9.5 mm, more preferably between about 4 mm and about 7.5 mm, more preferably between about 5 mm and about 7.5 mm. The "internal diameter" corresponds to the diameter of the rod of aerosol-generating substrate without including the thickness of the wrappers, but measured with the wrappers still in place.

[0212] Aerosol-generating articles according to the invention also include but are not limited to a cartridge or a shisha consumable.

[0213] Aerosol-generating articles according to the invention may optionally comprise at least one hollow tube immediately downstream of the aerosol-generating substrate. One function of the tube is to locate the aerosol-generating substrate towards the distal end of the aerosol-generating article so that it can be contacted with a heating element. The tube acts to prevent the aerosol-generating substrate from being forced along the aerosol-generating article towards other downstream elements when a heating element is inserted into the aerosol-generating substrate. The tube also acts as a spacer element to separate the downstream elements from the aerosol-generating substrate. The tube can be made of any material, such as cellulose acetate, a polymer, cardboard, or paper.

[0214] Aerosol-generating articles according to the invention optionally comprise one or more of a spacer or an aerosol-cooling element downstream of the aerosol-generating substrate and immediately downstream of the hollow tube. In use, an aerosol formed by volatile compounds released from the aerosol-generating substrate passes through and is cooled by the aerosol-cooling element before being inhaled by a user. The lower temperature allows the vapours to condense into an aerosol. The spacer or aerosol-cooling element may be a hollow tube, such as a hollow cellulose acetate tube or a cardboard tube, which can be similar to the one that is immediately downstream of the aerosol-generating substrate. The spacer may be a hollow tube of equal outer diameter but smaller or larger inner diameter than the hollow cellulose acetate tube. In one embodiment, the aerosol-cooling element wrapped in paper comprises one or more longitudinal channels made of any suitable material, such as a metallic foil, a paper laminated with a foil, a polymeric sheet preferably made of a synthetic polymer, and a substantially nonporous paper or cardboard. In some embodiments, the aerosol-cooling element wrapped in paper may comprise one or more sheets made of a material selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), cellulose acetate (CA), paper laminated with a polymeric sheet and aluminium foil. Alternatively, the aerosol-cooling element may be made of woven or non-woven filaments of a material selected from the group consisting of polyethylene (PE), polypropylene (PP), polyvinylchloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), and cellulose acetate (CA). In a preferred embodiment, the aerosol-cooling element is a crimped and gathered sheet of polylactic acid wrapped within a filter paper. In another preferred embodiment, the aerosol-cooling element comprises a longitudinal channel and is made of woven filaments of a synthetic polymer, such as polylactic acid filaments, which are wrapped in paper.

[0215] Aerosol-generating articles according to the invention may further comprise a filter or mouthpiece downstream of the aerosol-generating substrate and the hollow acetate tube, spacer or aerosol-cooling element. The filter may comprise one or more filtration materials for the removal of particulate components, gaseous components, or a combination thereof. Suitable filtration materials are known in the art and include, but are not limited to: fibrous filtration materials such as, for example, cellulose acetate tow and paper; adsorbents such as, for example, activated alumina, zeolites, molecular sieves and silica gel; biodegradable polymers including, for example, polylactic acid (PLA), Mater-Bi^®, hydrophobic viscose fibres, and bioplastics; and combinations thereof. The filter may be located at the downstream end of the aerosol-generating article. The filter may be a cellulose acetate filter plug. The filter is about 7 mm in length in one embodiment, but may have a length of between about 5 mm and about 10 mm.

[0216] Aerosol-generating articles according to the invention may comprise a mouth end cavity at the downstream end of the article. The mouth end cavity may be defined by one or more wrappers extending downstream from the filter or mouthpiece. Alternatively, the mouth end cavity may be defined by a separate tubular element provided at the downstream end of the aerosol-generating article.

[0217] Aerosol-generating articles according to the invention preferably further comprise a ventilation zone provided at a location along the aerosol-generating article. For example, the aerosol-generating article may be provided at a location along a hollow tube provided downstream of the aerosol-generating substrate.

[0218] In preferred embodiments of the invention, the aerosol-generating article comprises the aerosol-generating substrate, at least one hollow tube downstream of the aerosol-generating substrate and a filter downstream of the at least one hollow tube. Optionally, the aerosol-generating article further comprises a mouth end cavity at the downstream end of the filter. Preferably, a ventilation zone is provided at a location along the at least one hollow tube.

[0219] The aerosol-generating articles according to the invention may have a total length of at least about 30 mm, or at least about 40 mm. The total length of the aerosol-generating article may be less than 90 mm, or less than about 80 mm.

[0220] In one embodiment, the aerosol-generating article has a total length of between about 40 mm and about 50 mm, preferably about 45 mm. In another embodiment, the aerosol-generating article has a total length of between about 70 mm and about 90 mm, preferably between about 80 mm and about 85 mm. in another embodiment, the aerosol-generating article has a total length of between about 72 mm and about 76 mm, preferably about 74 mm.

[0221] The aerosol-generating article may have an external diameter of about 5 mm to about 8 mm, preferably between about 6 mm and about 8 mm. In one embodiment, the aerosol-generating article has an external diameter of about 7.3 mm.

[0222] Aerosol-generating articles according to the invention may further comprise one or more aerosol-modifying elements. An aerosol-modifying element may provide an aerosol-modifying agent. As used herein, the term aerosol-modifying agent is used to describe any agent that, in use, modifies one or more features or properties of aerosol passing through the filter. Suitable aerosol-modifying agents include, but are not limited to, agents that, in use, impart a taste or aroma to aerosol passing through the filter or agents that, in use, remove flavours from the aerosol passing through the filter.

[0223] An aerosol-modifying agent may be one or more of moisture or a liquid flavourant. Water or moisture may modify the sensorial experience of the user, for example by moistening the generated aerosol, which may provide a cooling effect on the aerosol and may reduce the perception of harshness experienced by the user. An aerosol-modifying element may be in the form of a flavour-delivery element to deliver one or more liquid flavourants. Alternatively, a liquid flavourant may be added directly to the homogenised plant material, for example, by adding the flavour to the slurry or feedstock during production of the homogenised plant material, or by spraying the liquid flavourant onto the surface of the homogenised plant material.

[0224] The one or more liquid flavourants may comprise any flavour compound or botanical extract suitable for being releasably disposed in liquid form within the flavour-delivery element to enhance the taste of aerosol produced during use of the aerosol-generating article. The flavourants, liquid or solid, can also be disposed directly in the material which forms the filter, such as cellulose acetate tow. Suitable flavours or flavourings include, but are not limited to, menthol, mint, such as peppermint and spearmint, chocolate, liquorice, citrus and other fruit flavours, gamma octalactone, vanillin, ethyl vanillin, breath freshener flavours, spice flavours such as cinnamon, methyl salicylate, linalool, eugenol, bergamot oil, geranium oil, lemon oil, cannabis oil, and tobacco flavour. Other suitable flavours may include flavour compounds selected from the group consisting of an acid, an alcohol, an ester, an aldehyde, a ketone, a pyrazine, combinations or blends thereof and the like.

[0225] An aerosol-modifying agent may be an adsorbent material such as activated carbon, which removes certain constituents of the aerosol passing through the filter and thereby modifies the flavour and aroma of the aerosol.

[0226] The one or more aerosol-modifying elements may be located downstream of the aerosol-generating substrate or within the aerosol-generating substrate. The aerosol-generating substrate may comprise homogenised tobacco material and an aerosol-modifying element. In various embodiments, the aerosol-modifying element may be placed adjacent to the homogenised tobacco material or embedded in the homogenised tobacco material. Typically, aerosol-modifying elements may be located downstream of the aerosol-generating substrate, most typically, within the aerosol-cooling element, within the filter of the aerosol-generating article, such as within a filter plug or within a cavity between filter plugs. The one or more aerosol-modifying elements may be in the form of one or more of a thread, a capsule, a microcapsule, a bead or a polymer matrix material, or a combination thereof.

[0227] If an aerosol-modifying element is in the form of a thread, as described in WO-A-2011/060961, the thread may be formed from paper such as filter plug wrap, and the thread may be loaded with at least one aerosol-modifying agent and located within the body of the filter. Other materials that can be used to form a thread include cellulose acetate and cotton.

[0228] If an aerosol-modifying element is in the form of a capsule, as described in WO-A-2007/010407, WO-A-2013/068100 and WO-A-2014/154887, the capsule may be a breakable capsule located within the filter, the inner core of the capsule containing an aerosol-modifying agent which may be released upon breakage of the outer shell of the capsule when the filter is subjected to external force. The capsule may be located within a filter plug or within a cavity between filter plugs.

[0229] If an aerosol-modifying element is in the form of a polymer matrix material, the polymer matrix material releases the flavourant when the aerosol-generating article is heated, such as when the polymer matrix is heated above the melting point of the polymer matrix material as described in WO-A-2013/034488. Typically, such polymer matrix material may be located within a bead within the aerosol-generating substrate. Alternatively, or in addition, the flavourant may be trapped within the domains of a polymer matrix material and releasable from the polymer matrix material upon compression of the polymer matrix material. Preferably, the flavourant is released upon compression of the polymer matrix material with a force of around 15 Newtons. Such flavour-modifying elements may provide a sustained release of the liquid flavourant over a range of force of at least 5 Newtons, such as between 5N and 20N, as described in WO2013/068304. Typically, such polymer matrix material may be located within a bead within the filter.

[0230] The aerosol-generating article may comprise a combustible heat source and an aerosol-generating substrate downstream of the combustible heat source, the aerosol-generating substrate as described above with respect to the first aspect of the invention.

[0231] For example, substrates as described herein may be used in heated aerosol-generating articles of the type disclosed in WO-A-2009/022232, which comprise a combustible carbon-based heat source, an aerosol-generating substrate downstream of the combustible heat source, and a heat-conducting element around and in contact with a rear portion of the combustible carbon-based heat source and an adjacent front portion of the aerosol-generating substrate. However, it will be appreciated that substrates as described herein may also be used in heated aerosol-generating articles comprising combustible heat sources having other constructions.

[0232] The present invention provides an aerosol-generating system comprising an aerosol-generating device comprising a heating element, and an aerosol-generating article for use with the aerosol-generating device, the aerosol-generating article comprising the aerosol-generating substrate as described above.

[0233] In a preferred embodiment, aerosol-generating substrates as described herein may be used in heated aerosol-generating articles for use in electrically-operated aerosol-generating systems in which the aerosol-generating substrate of the heated aerosol-generating article is heated by an electrical heat source.

[0234] For example, aerosol-generating substrates as described herein may be used in heated aerosol-generating articles of the type disclosed in EP-A-0 822 760.

[0235] The heating element of such aerosol-generating devices may be of any suitable form to conduct heat. The heating of the aerosol-generating substrate may be achieved internally, externally or both. The heating element may preferably be a heater blade or pin adapted to be inserted into the substrate so that the substrate is heated from inside. Alternatively, the heating element may partially or completely surround the substrate and heat the substrate circumferentially from the outside.

[0236] In certain embodiments of the invention, the aerosol-generating system comprises an aerosol-generating article comprising an aerosol-generating substrate as defined above, a source of aerosol former and a means to vaporise the aerosol former, preferably a heating element as described above. The source of aerosol former can be a reservoir, which can be refillable or replaceable, that resides on the aerosol generating device. While the reservoir is physically separate from the aerosol generating article, the vapour that is generated is directed through the aerosol-generating article. The vapour makes contact with the aerosol-generating substrate which releases volatile compounds, such as nicotine and flavourants in the plant material, to form an aerosol. Optionally, to aid volatilization of compounds in the aerosol-generating substrate, the aerosol-generating system may further comprise a heating element to heat the aerosol-generating substrate, preferably in a co-ordinated manner with the aerosol former. However, in certain embodiments, the heating element used to heat the aerosol generating article is separate from the heater that heats the aerosol former.

[0237] As defined above, the present invention further provides a method for the production of dried green tobacco material for use in an aerosol-generating substrate according to the invention, as described in detail below. The method according to the invention includes the following steps: providing uncured green tobacco leaves; drying the uncured green tobacco leaves until a moisture content of between 4 percent by weight and 15 percent by weight is achieved; and cutting or grinding the uncured green tobacco leaves to produce dried green tobacco material. According to the invention, the temperature, pressure and duration of the drying step are selected such that the dried green tobacco material retains a chlorophyll level of at least 0.5 milligrams per gram. This means that the drying step is carried out in such a way that the level of chlorophyll in the tobacco leaves is retained and the leaves remain green in colour. The green tobacco leaves are not subjected to any curing process.

[0238] Preferably, the drying step of the method according to the invention is completed within than 5 days from the harvesting of the uncured green tobacco leaves, more preferably within 4 days from the harvesting, more preferably within 3 days from the harvesting and most preferably within 2 days from the harvesting. This means that the total storage and drying time of the tobacco material does not exceed 5 days, or 4 days, or 3 days or 2 days from the time that the tobacco material is harvested. The dried green tobacco material is therefore produced within a relatively short time after the harvesting of the tobacco, so that any effects on the chemical composition of the tobacco leaves as a result of storage of the tobacco leaves can be minimised.

[0239] The method of the present invention provides a fast and efficient way to process green tobacco leaves into dried green tobacco material that is suitable for use in an aerosol-generating substrate for an aerosol-generating article, as described above. This in turn enables an aerosol-generating substrate to be produced more efficiently, both from a time and cost perspective. The method of the present invention can be applied to all tobacco types. Advantageously, the method of the present invention can be carried out on whole tobacco leaves, without destemming, if desired. Alternatively, the method according to the invention may be carried out with the lamina of the uncured green tobacco leaves. In this case, the leaves would be destemmed prior to the drying step and the stems processed separately. If desired, the stems may be recombined with the tobacco lamina to provide the dried green tobacco material for forming the aerosol-generating substrate.

[0240] The drying of the green tobacco leaves is carried out with specifically selected temperature and pressure conditions so that curing does not occur and the tobacco leaves retain their green colour. As described above, there are several benefits to the use of green tobacco leaves in an aerosol-generating substrate, based on the reduced levels of certain undesirable constituents that are present in green tobacco leaves compared with cured leaves.

[0241] Several different methods are available for rapidly drying the uncured tobacco leaves to reduce the moisture content to between about 4 percent and about 15 percent by weight, more preferably between about 10 percent and about 13 percent by weight, whilst retaining the chlorophyll levels in the leaf as high as possible. Depending upon the method selected, the temperature, pressure and duration are specifically adapted to provide the required outcome.

[0242] In certain embodiments, the drying step is carried out by heating the uncured green tobacco leaves to reduce the moisture content of the leaves as rapidly as possible. Heating of the tobacco leaves may be carried out using any suitable apparatus, such as an oven or dryer, which would be known to the skilled person. Preferably, the heating of the tobacco leaves is carried out in a tray dryer. An example of a suitable apparatus for carrying out the drying step is the tray dryer available from Wolvering Proctor & Schwartz Ltd.

[0243] In a tray dryer, the tobacco leaves are typically hung within the heating chamber, which minimises contact between leaves and maximises the surface area of the leaves that is exposed, in order to facilitate drying. During the drying step, heated air or steam is circulated through the chamber at the desired temperature. The use of a tray dryer for heating the tobacco leaves has been found to advantageously provide an even heating of the leaves, with minimisation of hot spots within the dryer. This optimises the uniformity of the drying of the leaves. The use of a tray dryer has also been found to be most effective for the drying of the midribs of the tobacco leaves, which typically dry more slowly than the lamina portions of the leaves.

[0244] Preferably, in such embodiments, the drying step is carried out at a temperature of less than about 120 degrees Celsius, more preferably at a temperature of less than about 110 degrees Celsius. Preferably, the drying step is carried out at a temperature of at least about 75 degrees Celsius, more preferably at least about 85 degrees Celsius and more preferably at least about 100 degrees Celsius. For example, the drying step may be carried out at a temperature of between about 75 degrees Celsius and about 120 degrees Celsius, or between about 75 degrees and about 110 degrees Celsius. This temperature level is selected in order to provide effective drying whilst retaining a relatively high level of chlorophyll and avoiding damage to the leaves during the heating process.

[0245] In a particularly preferred embodiment, the drying step is carried out at a temperature of between 75 degrees Celsius and 110 degrees Celsius in a tray dryer.

[0246] The duration of the heating step will depend upon the moisture level of the uncured tobacco leaves prior to drying, as well as the specific temperature selected for the heating step and the exact heating conditions. Preferably, the tobacco leaves are heated for no more than 7 hours, preferably no more than 6 hours, preferably no more than 4 hours, more preferably no more than 2 hours and most preferably no more than 1 hour.

[0247] In a particularly preferred example, the uncured tobacco leaves are heated at a temperature of 75 degrees Celsius for no more than 7 hours to achieve the required reduction in moisture content. In an alternative preferred example, the uncured tobacco leaves are heated at a temperature of 110 degrees Celsius for no more than 4 hours to achieve the required reduction in moisture content.

[0248] Preferably, the heating step is carried out under ventilated conditions, with a continuous flow of air or inert gas being passed through the tobacco leaves during heating. This may advantageously decrease the required drying time.

[0249] Preferably, the heating step is carried out without agitation of the tobacco leaves, for example, in a rotary drum. This avoids potential damage to the tobacco leaves during heating.

[0250] The heating step may be carried out on the whole, intact tobacco leaves. Alternatively, the tobacco leaves may be destemmed prior to the heating steps such that the tobacco lamina and the tobacco stems are dried separately from each other.

[0251] In certain embodiments, the heating step comprises heating the whole tobacco leaves, separating the tobacco lamina from the tobacco stems when dry and removing the tobacco lamina from the dryer, then heating the remaining tobacco stems until dry. This enables both the tobacco lamina and mid rib to be effectively dried, without over-drying the lamina.

[0252] In certain embodiments in which the drying step is carried out by heating, the method according to the invention may further comprise a second heating step, which is carried out after the first heating step and at a lower temperature. For example, the method may further comprise a second heating step during which the uncured green tobacco leaves are heated at a temperature of less than about 75 degrees Celsius, or less than about 50 degrees Celsius. The inclusion of a second heating step may be advantageous where the uncured tobacco leaves are kept intact during drying, so that complete drying of the tobacco stem (mid-rib) can be achieved.

[0253] As an alternative to heating, the drying step of the method of the present invention may be carried out by lyophilisation. Lyophilisation, also known as freeze drying, is a dehydration process which involves freezing a product (in this case, the tobacco leaves) and then progressively reducing the pressure and increasing the temperature in order to sublimate the frozen water and thereby remove it from the product.

[0254] Preferably, during drying of the uncured green tobacco leaves by lyophilisation, the tobacco leaves are initially frozen to a temperature of less than minus 60 degrees, more preferably less than minus 75 degrees Celsius. For example, the tobacco leaves may be frozen to a temperature of about minus 80 degrees Celsius. Preferably, the freezing of the tobacco leaves is carried out as soon after the harvesting of the leaves as possible.

[0255] The remaining steps of the lyophilisation process are carried out in a suitable lyophilisation chamber. In a first lyophilisation phase, the uncured tobacco leaves are preferably retained in a frozen state at atmospheric pressure. Preferably, the duration of the first lyophilisation phase is no more than about 60 minutes, more preferably no more than about 30 minutes.

[0256] In a second lyophilisation phase, the vacuum pressure and the temperature within the chamber are progressively adjusted to reach a target pressure (below atmospheric pressure) and a target temperature (below room temperature). The target pressure is preferably approximately 0.1 mBar. The target temperature is preferably approximately 15 degrees Celsius. Preferably, the duration of the second lyophilisation step is between about 24 hours and about 60 hours.

[0257] In a third and final lyophilisation step, the temperature is increased to approximately room temperature (22 degrees Celsius) under a full vacuum. Preferably, the duration of the third lyophilisation step is between about 24 hours and about 60 hours.

[0258] As a further alternative, the drying step of the method of the present invention may be carried out using microwave heating. For example, the uncured green tobacco leaves may be dried in a microwave tunnel dryer. The use of microwave heating to dry the uncured green tobacco leaves advantageously enables the moisture of the leaves to be removed very quickly since the microwaves can make the temperature of the leaf rise rapidly, causing the water molecules within the tobacco to evaporate.

[0259] Preferably, during the drying step, the uncured green tobacco leaves are continuously transferred through one or more microwave units, for example, on a conveyor belt. The power and duration of the microwave heating step can be adapted in order to provide the required moisture level of the tobacco leaves.

[0260] Suitable microwave tunnel dryers are commercially available, for example, from Jinan Himax machinery Co., Ltd.

[0261] After the uncured green tobacco leaves have been dried to the required moisture content of between 4 percent and 15 percent by weight, the dried tobacco leaves are processed in order to form dried green tobacco material of the desired size. The uncured green tobacco leaves are preferably cut or ground using known techniques for producing tobacco particles.

[0262] Specific embodiments will be further described, by way of example only, with reference to the accompanying drawings in which:

Figure 1 illustrates a first embodiment of a substrate of an aerosol-generating article as described herein;

Figure 2 illustrates an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device comprising an electric heating element;

Figure 3 illustrates an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device comprising a combustible heating element;

Figure 4 is a cross sectional view of filter 1050 further comprising an aerosol-modifying element, wherein

Figure 4a illustrates the aerosol-modifying element in the form of a spherical capsule or bead within a filter plug.

Figure 4b illustrates the aerosol-modifying element in the form of a thread within a filter plug.

Figure 4c illustrates the aerosol-modifying element in the form of a spherical capsule within a cavity within the filter; and

Figure 5 is a cross sectional view of a plug of aerosol-generating substrate 1020 further comprising an elongate susceptor element.

[0263] Figure 1 illustrates a heated aerosol-generating article 1000 comprising a substrate as described herein. The article 1000 comprises four elements; the aerosol-generating substrate 1020, a hollow cellulose acetate tube 1030, a spacer element 1040, and a mouthpiece filter 1050. These four elements are arranged sequentially and in coaxial alignment and are assembled by a cigarette paper 1060 to form the aerosol-generating article 1000. The article 1000 has a mouth-end 1012, which a user inserts into his or her mouth during use, and a distal end 1013 located at the opposite end of the article to the mouth end 1012. The embodiment of an aerosol-generating article illustrated in Figure 1 is particularly suitable for use with an electrically-operated aerosol-generating device comprising a heater for heating the aerosol-generating substrate.

[0264] When assembled, the article 1000 is about 45 millimetres in length and has an outer diameter of about 7.2 millimetres and an inner diameter of about 6.9 millimetres.

[0265] The aerosol-generating substrate 1020 comprises a plug formed from a sheet of homogenised tobacco material comprising a blend of dried green tobacco material with cured tobacco particles.

[0266] A number of examples of a suitable homogenised tobacco material for forming the aerosol-generating substrate 1020 are shown in Table 1 below (see Samples A and B). The sheet is gathered, crimped and wrapped in a filter paper (not shown) to form the plug. The sheet includes additives, including glycerol as an aerosol former.

[0267] An aerosol-generating article 1000 as illustrated in Figure 1 is designed to engage with an aerosol-generating device in order to be consumed. Such an aerosol-generating device includes means for heating the aerosol-generating substrate 1020 to a sufficient temperature to form an aerosol. Typically, the aerosol-generating device may comprise a heating element that surrounds the aerosol-generating article 1000 adjacent to the aerosol-generating substrate 1020, or a heating element that is inserted into the aerosol-generating substrate 1020.

[0268] Once engaged with an aerosol-generating device, a user draws on the mouth-end 1012 of the smoking article 1000 and the aerosol-generating substrate 1020 is heated to a temperature of about 375 degrees Celsius. At this temperature, volatile compounds are evolved from the aerosol-generating substrate 1020. These compounds condense to form an aerosol. The aerosol is drawn through the filter 1050 and into the user's mouth.

[0269] Figure 2 illustrates a portion of an electrically-operated aerosol-generating system 2000 that utilises a heating blade 2100 to heat an aerosol-generating substrate 1020 of an aerosol-generating article 1000. The heating blade is mounted within an aerosol article receiving chamber of an electrically-operated aerosol-generating device 2010. The aerosol-generating device defines a plurality of air holes 2050 for allowing air to flow to the aerosol-generating article 1000. Air flow is indicated by arrows on Figure 2. The aerosol-generating device comprises a power supply and electronics, which are not illustrated in Figure 2. The aerosol-generating article 1000 of Figure 2 is as described in relation to Figure 1.

[0270] In an alternative configuration shown in Figure 3, the aerosol-generating system is shown with a combustible heating element. While the article 1000 of Figure 1 is intended to be consumed in conjunction with an aerosol-generating device, the article 1001 of Figure 3 comprises a combustible heat source 1080 that may be ignited and transfer heat to the aerosol-generating substrate 1020 to form an inhalable aerosol. The combustible heat source 80 is a charcoal element that is assembled in proximity to the aerosol-generating substrate at a distal end 13 of the rod 11. Elements that are essentially the same as elements in Figure 1 have been given the same numbering.

[0271] Figure 4 is a cross sectional view of filter 1050 further comprising an aerosol-modifying element. In Figure 4a, the filter 1050 further comprises an aerosol-modifying element in the form of a spherical capsule or bead 605.

[0272] In the embodiment of Figure 4a, the capsule or bead 605 is embedded in the filter segment 601 and is surrounded on all sides by the filter material 603. In this embodiment, the capsule comprises an outer shell and an inner core, and the inner core contains a liquid flavourant. The liquid flavourant is for flavouring aerosol during use of the aerosol-generating article provided with the filter. The capsule 605 releases at least a portion of the liquid flavourant when the filter is subjected to external force, for example by squeezing by a consumer. In the embodiment shown, the capsule is generally spherical, with a substantially continuous outer shell containing the liquid flavourant.

[0273] In the embodiment of Figure 4b, the filter segment 601 comprises a plug of filter material 603 and a central flavour-bearing thread 607 that extends axially through the plug of filter material 603 parallel to the longitudinal axis of the filter 1050. The central flavour-bearing thread 607 is of substantially the same length as the plug of filter material 603, so that the ends of the central flavour-bearing thread 607 are visible at the ends of the filter segment 601. In Figure 4b, filter material 603 is cellulose acetate tow. The central flavour-bearing thread 607 is formed from twisted filter plug wrap and loaded with an aerosol-modifying agent.

[0274] In the embodiment of Figure 4c, the filter segment 601 comprises more than one plug of filter material 603, 603'. Preferably, the plugs of filter material 603, 603' are formed from cellulose acetate, such that they are able to filter the aerosol provided by the aerosol generating article. A wrapper 609 is wrapped around and connects filter plugs 603, 603'. Inside a cavity 611 is a capsule 605 comprising an outer shell and an inner core, and the inner core contains a liquid flavourant. The capsule is otherwise similar to the embodiment of Figure 4a.

[0275] Figure 5 is a cross sectional view of aerosol-generating substrate 1020 further comprising an elongate susceptor strip 705. The aerosol-generating substrate 1020 comprises a plug 703 formed from a sheet of homogenised tobacco material comprising a blend of dried green tobacco material and cured tobacco particles. The elongate susceptor strip 705 is embedded within the plug 703 and extends in a longitudinal direction between the upstream and downstream ends of the plug 703. During use, the elongate susceptor strip 705 heats the homogenised tobacco material by means of induction heating, as described above.

Example

[0276] Different samples of homogenised tobacco material for use in an aerosol-generating substrate according to the invention, as described above with reference to the figures, may be prepared from aqueous slurries having compositions shown in Table 1. Samples A to D comprise dried green tobacco material (either alone or in combination with cured tobacco particles), in accordance with the invention. Sample E comprises only cured tobacco particles and is included for the purposes of comparison only.

[0277] Sample A is formed with a CMC binder in combination with cellulose fibres, in accordance with the second preferred embodiment of the invention. Sample A is prepared from an aqueous slurry containing 72.97 kg of water per 100 kg of slurry, with the remainder accounted for by the components in the relative amounts shown in Table 1.

[0278] Samples B to D are formed with a guar gum binder, in accordance with the first preferred embodiment of the invention. Samples B to D are prepared from an aqueous slurry containing between 78-79kg of water per 100 kg of slurry. Sample B is a comparative example.

[0279] In the table below, % DWB refers to the "dry weight base," in this case, the percent by weight calculated relative to the dry weight of the homogenised plant material. The tobacco particles have been ground to an average particles size of 100 microns by triple impact milling.

[0280] The dried green tobacco material are derived from Burley tobacco leaves and have been fast dried using a heating method according to the present invention, as described above. The cured tobacco particles may be derived from one or more types of cured tobacco, as desired.

[0281] The slurries may be casted using a casting bar (0.6 mm) on a glass plate, dried in an oven at 140 degrees Celsius for 7 minutes, and then dried in a second oven at 120 degrees Celsius for 30 seconds.

Table 1. Dry content of slurries

Sample	Uncured green tobacco (% DWB)	Cured tobacco (% DWB)	Glycerol (% DWB)	Guar Gum (% DWB)	CMC (% DWB)	Cellulose fibres (% DWB)
A	25	50	16.7	0	4.6	3.7
B	75	0	18	3	0	4
C	37.5	37.5	18	3	0	4
D	25	50	18	3	0	4
E	0	75	18	3	0	4

[0282] For each of the samples A to E of homogenised tobacco material, a plug may be produced from a single continuous sheet of the homogenised tobacco material, the sheets each having widths of between 100 mm to 130 mm. The individual sheets preferably have a thickness of about 220 microns and a grammage of about 189 g/m². The cut width of each sheet is about 120 mm. The sheets may be crimped to a height of 165 microns to 170 microns, and rolled into plugs having a length of about 12 mm and diameters of about 7 mm, circumscribed by a paper wrapper. The total weight of each plug is about 250 mg.

[0283] For each of the plugs, an aerosol-generating article having an overall length of about 45 mm may be formed having a structure as shown in Figure 3 comprising, from the downstream end: a mouth end cellulose acetate filter (about 7 mm long), an aerosol spacer comprising a crimped sheet of polylactic acid polymer (about 18 mm long), a hollow acetate tube (about 8 mm long) and the plug of aerosol-generating substrate.

Comparative Example 1 - Burley tobacco

[0284] In order to demonstrate the effect of the curing process on the chemical composition of Burley tobacco, the level of certain tobacco constituents was measured for three samples of Burley tobacco leaf: uncured green Burley tobacco leaf, 5 days air-cured Burley tobacco leaf and fully air-cured (50 days) Burley tobacco leaf. Each sample starts from the same uncured green Burley tobacco leaf and therefore the change in the level of each constituent is assumed to be a direct result of the curing process. The results are shown below in Table 2:

Table 2: Chemical composition of uncured and cured Burley tobacco leaf (dry weight basis)

Tobacco constituent	Amount in uncured green tobacco leaf (per gram)	Amount in 5 days cured tobacco leaf (per gram)	Amount in fully cured tobacco leaf (per gram)
Chlorophyll	1.2 mg	0.2 mg	0.2 mg
Asparagine	0.28 mg	12.5 mg	18.4 mg
Ammonia	0.11 mg	0.26 mg	2.55 mg
Total free amino acids	9.69 mg	56.8 mg	48.2 mg
NNN	259.2 ng	1553.6 ng	2154.2 ng

[0285] As shown by the table, the level of chlorophyll drops significantly to a very low level after only 5 days curing. This demonstrates that the presence of a level of chlorophyll above 0.5 mg/g is a good indicator for uncured green tobacco leaves.

[0286] The levels of asparagine, ammonia, total free amino acids and NNN were found to increase significantly as a result of the curing process so that in each case, the level of the constituent in the cured leaf was several times higher than in the uncured green leaf. As shown below, the reduced levels of these constituents in the uncured green tobacco leaf provided a reduction in the related undesirable constituent in the aerosol generated from a homogenised tobacco material comprising the uncured green tobacco.

[0287] The level of sugar in the Burley tobacco leaves was found to vary from 6.87 percent by weight for the uncured green tobacco leaves to 6.47 percent by weight for the 5 days cured tobacco leaves and 1.7 percent by weight for the fully cured tobacco leaves, measured on a dry weight basis.

[0288] For each of the Burley samples, a homogenised tobacco material was formed using a casting process as described above and having the composition shown below in Table 3:

Table 3: Homogenised tobacco material composition:

Component	% (dry weight basis)
Burley tobacco particles	37.5
Virginia flue-cured tobacco particles	37.5
Glycerol	18
Guar Gum	3
Cellulose fibres	4

[0289] Each of the samples of homogenised tobacco material was gathered to form a rod of aerosol-generating substrate having a weight of 250mg which was then incorporated into an aerosol-generating article as described above in the example. For each of these aerosol-generating articles, a mainstream aerosol was generated and collected in accordance with Test Method A, as described above. For each sample, the aerosol was trapped and analysed.

[0290] As described in detail above, according to Test Method A, the aerosol-generating articles may be tested using the commercially available IQOS^® heat-not-burn device tobacco heating system 2.2 holder (THS2.2 holder) from Philip Morris Products SA. The aerosol-generating articles are heated under a Health Canada machine-smoking regimen over 30 puffs with a puff volume of 55 ml, puff duration of 2 seconds and a puff interval of 30 seconds (as described in ISO/TR 19478-1:2014). The aerosol generated during the smoking test is collected on a Cambridge filter pad and extracted with a liquid solvent.

[0291] Table 4 below shows the levels of certain tobacco-derived aerosol constituents in the aerosols generated from the three samples containing uncured green Burley tobacco particles, 5 days cured Burley tobacco particles and fully cured Burley tobacco particles. The amounts of each aerosol constituent are expressed per article, based on a 250 mg rod of the aerosol-generating substrate:

Table 4: Composition of aerosol - amounts of tobacco-derived aerosol constituents

Aerosol constituent	Uncured green tobacco leaf (per article)	5 days cured tobacco leaf (per article)	Fully cured tobacco leaf (per article)
Acrylamide	0.76 µg	1.79 µg	2.98 µg
Ammonia	6.99 mg	11.15 mg	22.13 mg
Hydrogen sulphide	1.51 µg	1.61 µg	22.60 µg
Methanethiol	26.14 µg	31.06 µg	31.25 µg
Nicotine	1.04 mg	1.02 mg	1.01 mg

[0292] The results shown in Table 4 demonstrate the effect of including a proportion of dried green tobacco material in the homogenised tobacco material forming the aerosol-generating substrate, on the levels of aerosol constituents. Notably, the level of acrylamide in the aerosol generated from the sample with dried green tobacco material included was significantly lower than for the other two samples using only cured tobacco particles. This is thought to be due to the reduced level of asparagine in the uncured tobacco leaf, as described above. The levels of ammonia, hydrogen sulphide and methanethiol in the aerosol generated from the sample with dried green tobacco material included were also significantly lower than for the other two samples using only cured tobacco particles.

[0293] The results demonstrate that advantageously, the curing process does not materially affect the nicotine released from the tobacco material into the aerosol and so the use of dried green tobacco material in place of cured tobacco particles does not impact the nicotine content of the aerosol.

[0294] Overall, the aerosol generated from the sample containing dried green tobacco material therefore showed improved levels of certain undesirable compounds whilst retaining a consistent nicotine delivery.

[0295] Similar reductions in these aerosol constituents would also be expected from other tobacco types, such as Virginia.

Claims

1. An aerosol-generating article (1000) comprising a rod of an aerosol-generating substrate (1020), the aerosol-generating substrate (1020) comprising homogenised tobacco material, the homogenised tobacco material comprising between 10 percent and 50 percent by weight of dried green tobacco material on a dry weight basis, cured tobacco material or aerosol generating plant material, an aerosol former and an exogenous binder, wherein the homogenised tobacco material has an aerosol former content of between 5 percent and 55 percent by weight on a dry weight basis.

2. An aerosol-generating article (1000) according to claim 1, wherein the homogenised tobacco material comprises at least one of:

at least 0.1 milligrams of chlorophyll per gram, on a dry weight basis; and

no more than 2.5 milligrams of asparagine per gram, on a dry weight basis.

3. An aerosol-generating article (1000) according to any preceding claim, wherein the homogenised tobacco material comprises at least 1 percent by weight of cured tobacco material, on a dry weight basis.

4. An aerosol-generating article (1000) according to claim 3, wherein the ratio of dried green tobacco material to cured tobacco material in the homogenised tobacco material is no more than 1:1.

5. An aerosol-generating article (1000) according to any preceding claim, wherein the homogenised tobacco material comprises between 1 percent by weight and 10 percent by weight of the exogenous binder, on a dry weight basis.

6. An aerosol-generating article (1000) according to any preceding claim, wherein the homogenised tobacco material is in the form of cast leaf.

7. An aerosol-generating article (1000) according to any preceding claim, wherein the aerosol generating plant material is derived from one or more plants selected from: cannabis, tea, ginger, eucalyptus, clove, peppermint, star anise, rosemary, chamomile, thyme and dill seed.

8. An aerosol-generating article (1000) according to any preceding claim, wherein the dried green tobacco material has a moisture content of between 10 percent and 13 percent by weight.

9. An aerosol-generating article (1000) according to any preceding claim, wherein the dried green tobacco material is from tobacco lamina, tobacco stems, or a combination of both.

10. An aerosol-generating article (1000) according to any preceding claim, wherein the dried green tobacco material is in the form of dried green tobacco particles.

11. An aerosol-generating article (1000) according to any preceding claim, wherein the homogenised tobacco material further comprises at least 3 percent by weight of cellulose fibres.

12. An aerosol-generating article (1000) according to any preceding claim, wherein the rod of the aerosol-generating substrate (1020) comprises one or more sheets of homogenised tobacco material.

13. An aerosol-generating article (1000) according to claim 12, wherein the one or more sheets of homogenised tobacco material are gathered and crimped.

14. An aerosol-generating system (2000) comprising:

an aerosol-generating device (2010) comprising a heating element (2100); and

an aerosol-generating article (1000) according to any preceding claim.

15. A method of producing a homogenised tobacco material for use in the aerosol-forming substrate of aerosol-generating articles according any of claims 1 to 13, the method comprising the steps of:

combining dried green tobacco material, cured tobacco material or aerosol generating plant material, an aerosol former, an exogenous binder and water to form a slurry;

casting the slurry onto a surface to form a sheet of homogenised tobacco material; and

drying the sheet of homogenised tobacco material, wherein the sheet of homogenised tobacco material has an aerosol former content of between 5 percent by weight and 55 percent by weight, on a dry weight basis, and wherein said homogenised tobacco material comprises between 10 percent and 50 percent by weight of dried green tobacco material on a dry weight basis.

Ansprüche

1. Aerosolerzeugender Artikel (1000), aufweisend einen Stab eines aerosolerzeugenden Substrats (1020), wobei das aerosolerzeugende Substrat (1020) homogenisiertes Tabakmaterial aufweist, wobei das homogenisierte Tabakmaterial zwischen 10 und 50 Gew.-% getrocknetes grünes Tabakmaterial auf Trockengewichtsbasis, curiertes Tabakmaterial oder aerosolerzeugendes Pflanzenmaterial, einen Aerosolbildner und ein exogenes Bindemittel aufweist, wobei das homogenisierte Tabakmaterial einen Aerosolbildnergehalt zwischen 5 und 55 Gew.-% auf Trockengewichtsbasis aufweist.

2. Aerosolerzeugender Artikel (1000) nach Anspruch 1, wobei das homogenisierte Tabakmaterial wenigstens eines aufweist von:

wenigstens 0,1 Milligramm Chlorophyll pro Gramm, auf Trockengewichtsbasis; und

nicht mehr als 2,5 Milligramm Asparagin pro Gramm, auf Trockengewichtsbasis.

3. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das homogenisierte Tabakmaterial wenigstens 1 Gew.-% curiertes Tabakmaterial auf Trockengewichtsbasis aufweist.

4. Aerosolerzeugender Artikel(1000) nach Anspruch 3, wobei das Verhältnis von getrocknetem grünem Tabakmaterial zu curiertem Tabakmaterial in dem homogenisierten Tabakmaterial nicht mehr als 1:1 beträgt.

5. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das homogenisierte Tabakmaterial zwischen 1 Gew.-% und 10 Gew.-% des exogenen Bindemittels auf Trockengewichtsbasis aufweist.

6. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das homogenisierte Tabakmaterial in Form eines Gussblattes vorliegt.

7. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das aerosolerzeugende Pflanzenmaterial von einer oder mehreren Pflanzen abgeleitet ist, ausgewählt aus: Cannabis, Tee, Ingwer, Eukalyptus, Nelke, Pfefferminze, Sternanis, Rosmarin, Kamille, Thymian und Dillsamen.

8. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das getrocknete grüne Tabakmaterial einen Feuchtigkeitsgehalt zwischen 10 und 13 Gew.-% aufweist.

9. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das getrocknete grüne Tabakmaterial aus Tabaklamina, Tabakstielen oder einer Kombination der beiden besteht.

10. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das getrocknete grüne Tabakmaterial in Form von getrockneten grünen Tabakpartikeln vorliegt.

11. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei das homogenisierte Tabakmaterial ferner wenigstens 3 Gew.-% Zellulosefasern aufweist.

12. Aerosolerzeugender Artikel (1000) nach einem beliebigen vorangegangenen Anspruch, wobei der Stab des aerosolerzeugenden Substrats (1020) eine oder mehrere Folienbahnen aus homogenisiertem Tabakmaterial aufweist.

13. Aerosolerzeugender Artikel (1000) nach Anspruch 12, wobei die eine oder die mehreren Folienbahnen aus homogenisiertem Tabakmaterial gesammelt und gekräuselt sind.

14. Aerosolerzeugungssystem (2000), aufweisend:

Eine Aerosolerzeugungsvorrichtung (2010), die ein Heizelement (2100) aufweist; und

einen aerosolerzeugenden Artikel (1000) nach einem beliebigen vorangegangenen Anspruch.

15. Verfahren zum Herstellen eines homogenisierten Tabakmaterials zur Verwendung in dem aerosolerzeugenden Substrat aerosolerzeugender Artikel nach einem der Ansprüche 1 bis 13, das Verfahren umfassend die Schritte:

Kombinieren von getrocknetem grünem Tabakmaterial, curiertem Tabakmaterial oder aerosolerzeugendem Pflanzenmaterial, einem Aerosolbildner, einem exogenen Bindemittel und Wasser, um eine Aufschlämmung zu bilden;

Gießen der Aufschlämmung auf eine Oberfläche, um eine Folienbahn aus homogenisiertem Tabakmaterial zu bilden; und

Trocknen der Folienbahn aus homogenisiertem Tabakmaterial, wobei die Folienbahn aus homogenisiertem Tabakmaterial einen Aerosolbildnergehalt zwischen 5 und 55 Gew.-% auf Trockengewichtsbasis aufweist und wobei das homogenisierte Tabakmaterial zwischen 10 und 50 Gew.-% getrocknetes grünes Tabakmaterial auf Trockengewichtsbasis aufweist.

Revendications

1. Article de génération d'aérosol (1000) comprenant une tige de substrat de génération d'aérosol (1020), le substrat de génération d'aérosol (1020) comprenant une matière de tabac homogénéisé, la matière de tabac homogénéisé comprenant entre 10 pour cent et 50 pour cent en poids de matière de tabac vert dessiqué sur la base du poids à sec, une matière de tabac séché ou une matière végétale de génération d'aérosol, un agent de formation d'aérosol et un liant exogène, dans lequel la matière de tabac homogénéisé a une teneur en agent de formation d'aérosol entre 5 pour cent et 55 pour cent en poids sur la base du poids à sec.

2. Article de génération d'aérosol (1000) selon la revendication 1, dans lequel la matière de tabac homogénéisé comprend au moins l'un parmi :

au moins 0,1 milligramme de chlorophylle par gramme, sur la base du poids à sec ; et

pas plus de 2,5 milligrammes d'asparagine par gramme, sur la base du poids à sec.

3. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac homogénéisé comprend au moins 1 pour cent en poids de matière de tabac séché, sur la base du poids à sec.

4. Article de génération d'aérosol (1000) selon la revendication 3, dans lequel le rapport entre la matière de tabac vert dessiqué et la matière de tabac séché dans la matière de tabac homogénéisé n'est pas supérieur à 1:1.

5. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac homogénéisé comprend entre 1 pour cent en poids et 10 pour cent en poids du liant exogène, sur la base du poids à sec.

6. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac homogénéisé est sous la forme d'une feuille naturelle moulée.

7. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière végétale de génération d'aérosol est dérivée d'une ou plusieurs plantes choisies parmi : cannabis, thé, gingembre, eucalyptus, clou de girofle, menthe poivrée, anis étoilé, romarin, camomille, thym et graines d'aneth.

8. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac vert dessiqué a une teneur en humidité entre 10 pour cent et 13 pour cent en poids.

9. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac vert dessiqué provient de limbe de tabac, tiges de tabac ou d'une combinaison des deux.

10. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac vert dessiqué est sous la forme de particules de tabac vert dessiqué.

11. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la matière de tabac homogénéisé comprend en outre au moins 3 pour cent en poids de fibres de cellulose.

12. Article de génération d'aérosol (1000) selon une quelconque revendication précédente, dans lequel la tige du substrat de génération d'aérosol (1020) comprend une ou plusieurs feuilles de matière de tabac homogénéisé.

13. Article de génération d'aérosol (1000) selon la revendication 12, dans lequel les une ou plusieurs feuilles de matière de tabac homogénéisé sont froncées et crêpées.

14. Système de génération d'aérosol (2000) comprenant :

un dispositif de génération d'aérosol (2010) comprenant un élément de chauffage (2100) ; et

un article de génération d'aérosol (1000) selon une quelconque revendication précédente.

15. Procédé de production d'une matière de tabac homogénéisé pour une utilisation dans le substrat formant aérosol des articles de génération d'aérosol selon l'une quelconque des revendications 1 à 13, le procédé comprenant les étapes suivantes :

combinaison d'une matière de tabac vert dessiqué, d'une matière de tabac séché ou d'une matière végétale de génération d'aérosol, d'un agent de formation d'aérosol, d'un liant exogène et d'eau pour former une suspension épaisse ;

moulage de la suspension épaisse sur une surface pour former une feuille de matière de tabac homogénéisé ; et

dessiccation de la feuille de matière de tabac homogénéisé, dans lequel la feuille de matière de tabac homogénéisé a une teneur en agent de formation d'aérosol entre 5 pour cent en poids et 55 pour cent en poids, sur la base du poids à sec, et dans lequel ladite matière de tabac homogénéisé comprend entre 10 pour cent et 50 pour cent en poids de matière de tabac vert dessiqué sur la base du poids à sec.

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