CN116801737A

CN116801737A - Novel aerosol-generating substrate

Info

Publication number: CN116801737A
Application number: CN202180071690.8A
Authority: CN
Inventors: L·博维特; S·格普费特; A·荷福克; D·朗格莱特
Original assignee: Philip Morris Products SA
Current assignee: Philip Morris Products SA
Priority date: 2020-10-29
Filing date: 2021-10-29
Publication date: 2023-09-22
Also published as: JP2023548453A; US20230397649A1; KR20230095106A; EP4236703A1; MX2023004864A; AU2021372809A1; WO2022090497A1; CA3196772A1; IL302283A

Abstract

An aerosol-generating substrate for an aerosol-generating article, the aerosol-generating substrate comprising a homogenized tobacco material, the homogenized tobacco material comprising dried raw tobacco material, an aerosol-forming agent and a binder. The homogenized tobacco material has an aerosol former content of between 5 wt.% and 55 wt.% on a dry weight basis.

Description

Novel aerosol-generating substrate

The present invention relates to a novel aerosol-generating substrate comprising dried raw tobacco material and an aerosol-generating article comprising such a substrate. The invention also relates to a method for producing a dried raw tobacco material for an aerosol-generating substrate.

In the production of combustible smoking articles, it is believed that the use of only fully cured tobacco material is critical, as the use of uncooked raw tobacco leaves has been found to produce undesirable aromas and flavors when the tobacco leaves are burned during smoking. By curing the tobacco material, the chemical nature of the tobacco can be altered through the drying and browning processes to minimize undesirable aroma and taste. Various curing methods are used in the tobacco industry, including, but not limited to, baking (fluid curing), air curing (air curing), and sun curing (sun curing).

Aerosol-generating articles are known in the art in which an aerosol-generating substrate, such as a tobacco-containing substrate, is heated rather than combusted. Typically in such articles, the aerosol is generated by transferring heat from a heat source to a physically separate aerosol-generating substrate or material that may be positioned 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 become entrained in air drawn through the article. As the released compound cools, the compound condenses to form an aerosol.

In producing a tobacco-containing aerosol-generating substrate for such heated articles, cooked tobacco material is used to produce an aerosol that replicates the aroma and taste of smoke from a combustible smoking article.

The tobacco curing process begins with harvesting raw, uncooked tobacco leaves, followed by a "yellowing" stage lasting on average 5 to 10 days, and finally a drying or browning stage, which can last for up to 50 days. As curing progresses, the tobacco leaves change from their original green color first to yellow and finally to brown as chlorophyll in the leaves degrades. In each stage, curing is continued until the desired moisture level in the tobacco leaves is achieved. In green tobacco leaves which have not been cured, green is a result of high levels of chlorophyll in the leaves. In contrast, after curing, tobacco leaves were found to contain only very low chlorophyll levels and to be brown in color.

The curing process used in the tobacco industry is relatively time consuming and typically requires the use of a significant amount of space and resources. Alternative, faster processes for drying tobacco materials other than curing have been attempted. However, the resulting dried tobacco material has not been found suitable for use in combustible smoking articles because the rapid drying process does not remove or substantially reduce the constituent components that produce undesirable aroma and taste upon burning tobacco.

It is desirable to provide a novel aerosol-generating substrate for a heated aerosol-generating article that can be produced in a more efficient manner without adversely affecting the organoleptic properties of the resulting aerosol generated upon heating the substrate.

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

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

The present disclosure also relates to the use of dried raw tobacco leaves in the production of aerosol-generating substrates for aerosol-generating articles.

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

According to the present invention there is provided an aerosol-generating substrate for a heated aerosol-generating article, the aerosol-generating substrate comprising dried raw tobacco material, an aerosol-former and a binder. The aerosol-generating substrate may be in the form of a homogenized tobacco material comprising between 5% and 55% by weight of aerosol-forming agent.

According to the present invention there is also provided an aerosol-generating article comprising a rod of aerosol-generating substrate comprising dried raw tobacco material, an aerosol-former and a binder. The aerosol-generating substrate may be in the form of a homogenized tobacco material comprising between 5% and 55% by weight of aerosol-forming agent.

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

According to the present invention, there is also provided a dried raw tobacco material having a moisture content of between about 4% and about 15% by weight and a chlorophyll level of at least 0.5 milligrams per gram.

The present disclosure also relates to a method of producing a dried raw tobacco material for use in an aerosol-generating substrate as defined above. The method may include: providing uncooked raw tobacco leaves; drying the uncooked raw tobacco until a moisture content of between 4 wt.% and 15 wt.% is achieved; and cutting or grinding the uncooked raw tobacco leaf to produce dried raw tobacco material. The temperature, pressure and duration of the drying step may be selected such that the dried raw tobacco material retains chlorophyll levels of at least 0.5 milligrams per gram.

According to the present invention there is provided a method of producing a dried raw tobacco material for use in an aerosol-generating substrate according to the present invention as defined above. The method comprises the following steps: providing uncooked raw tobacco leaves; drying the uncooked raw tobacco until a moisture content of between 4 wt.% and 15 wt.% is achieved; and cutting or grinding the uncooked raw tobacco leaf to produce dried raw tobacco material. According to the present invention, the temperature, pressure and duration of the drying step are preferably selected such that the dried raw tobacco material retains chlorophyll levels of at least 0.5 milligrams per gram. Preferably, the drying step is performed by heating the uncooked raw tobacco leaf to a temperature between 75 degrees celsius and 120 degrees celsius for no more than 4 hours.

According to the present invention there is also provided a dried raw tobacco material produced by the method according to the present invention as defined above.

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

Any reference below to an aerosol-generating substrate and an aerosol-generating article of the invention should be considered as applicable to all aspects of the invention.

As used herein, the term "aerosol-generating article" refers to an article for generating 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. When a user applies a flame to one end of the cigarette and draws air through the other end, the conventional cigarette will be lit. The localized heat provided by the flame and the oxygen in the air drawn through the cigarette causes the ends of the cigarette to be lit and the resulting combustion generates inhalable smoke. In contrast, in a "heated aerosol-generating article", the aerosol is generated by heating the aerosol-generating substrate rather than by burning the aerosol-generating substrate. Heated aerosol-generating articles are known to include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by heat transfer from a combustible fuel element or heat source to a physically separate aerosol-generating substrate.

Aerosol-generating articles suitable for use in aerosol-generating systems for supplying an aerosol-forming agent to the aerosol-generating article are also known. In such systems, the aerosol-generating substrate in the aerosol-generating article contains significantly less aerosol-forming agent relative to those that carry and provide substantially all of the aerosol-forming agent used in forming an aerosol during operation.

As used herein, the term "aerosol-generating substrate" refers to a substrate capable of generating volatile compounds upon heating that can form an aerosol. The aerosols generated by the aerosol-generating substrate may be visible or invisible to the human eye and may comprise droplets of vapor (e.g., fine particulate matter in the gaseous state, which is typically a liquid or solid at room temperature) as well as gases and condensed vapors.

The aerosol-generating substrate according to the invention is particularly suitable for use in heated aerosol-generating articles, also referred to as heated non-combustible articles.

The aerosol-generating substrate according to the invention may be in any suitable form capable of generating an aerosol upon heating. Preferably, the aerosol-generating substrate is in the form of a homogenized tobacco material, such as 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 tobacco cut filler.

As used herein, the term "homogenized tobacco material" encompasses any plant material formed by agglomeration of particles of tobacco plants. For example, a sheet or web of homogenized tobacco material for use in the aerosol-generating substrate of the invention may be formed by agglomerating particles of plant material obtained by comminuting, grinding or milling tobacco plant material, such as tobacco lamina or tobacco stems. The homogenized tobacco material may be produced by casting, extrusion, papermaking processes, or any other suitable process known in the art.

The term "dried raw tobacco material" is used in this specification to refer to a material formed from tobacco leaves that have been dried without undergoing any curing process. The dried raw tobacco material is thus uncooked. Such dried raw tobacco material will generally retain its natural green color. The dried raw tobacco material is formed from uncooked raw tobacco leaves that are dried as described below to provide a desired moisture content without any curing. The dried raw tobacco material may be from tobacco lamina, stems, or a combination thereof. The dried raw tobacco material preferably has a moisture content of less than 15% by weight.

In the present specification, the term "uncooked raw tobacco leaf" is used to refer to tobacco leaves that have not undergone any curing process after harvesting.

Accordingly, the present invention provides a novel aerosol-generating substrate formed from at least a proportion of dried raw tobacco material that would normally be provided in combination with a proportion of cooked tobacco material.

The inventors have surprisingly found that at least a proportion of dried raw tobacco material may be used in place of cooked tobacco material to form an aerosol-generating substrate for a heated aerosol-generating article without adversely affecting the organoleptic properties of the resulting aerosol. In particular, it has surprisingly been found that when a substrate comprising dried raw tobacco material is heated rather than combusted to form an aerosol, the resulting aerosol does not have the unpleasant aroma or taste generated when the raw tobacco material is used in a combustible smoking article as described above.

The dried raw tobacco material may advantageously be produced significantly faster and more efficiently than cooked tobacco material, as a rapid drying process may be used to achieve a desired moisture content rather than a much slower cooking process. The dried raw tobacco material may also be produced in a natural manner and in an organic manner, thereby providing a more sustainable process for generating an aerosol-generating substrate.

Advantageously, the method of drying uncooked raw tobacco leaves to produce a dried raw tobacco material suitable for use in the aerosol-generating substrate of the present invention can be applied to all tobacco types.

Furthermore, it has been found that uncooked raw tobacco leaves can be dried and processed without stem removal, which will further increase the production efficiency of the aerosol-generating substrate according to the invention.

The curing process of tobacco is known to affect the chemical composition of tobacco, in particular the levels of certain tobacco constituents and the levels of certain undesirable tobacco constituents that will affect the flavor of the resulting aerosol generated from the aerosol-generating substrate. For example, it has surprisingly been found that there is a significant reduction compared to that in cooked tobacco due to the absence of a cooking step in the production of dried raw tobacco materialAsparagine, ammonia, free amino acids and total alkaloid levels. This has an effect on the aerosols produced by the aerosol-generating substrates according to the invention, which aerosols will contain less undesirable compounds such as acrylamide, hydrogen sulphide (H ₂ S) and methyl mercaptan (MeSH). Thus, the inclusion of dried raw tobacco material in the aerosol-generating substrate enables improved aerosol generation upon heating of the substrate than would be generated from a substrate using only cooked tobacco without dried raw tobacco material.

It has also been found that dried raw tobacco material has a significantly higher sugar level than cooked tobacco material. The presence of sugar within the dried raw tobacco material may advantageously facilitate the manufacture of the aerosol-generating substrate, for example, in cases where the aerosol-generating substrate is formed using a cast-leaf process as described below. In particular, relatively high sugar levels within the dried raw tobacco material will improve the flexibility of the sheet of aerosol-generating substrate formed from the dried raw tobacco material.

As mentioned above, when the tobacco material is not subjected to a curing process, it will generally retain its natural high chlorophyll level and thus retain its green color. As a direct consequence of the inclusion of a proportion of dried raw tobacco material in the aerosol-generating substrate of the present invention, the level of chlorophyll in the substrate will be significantly higher than that measured in a typical substrate formed from cooked tobacco alone. The cured tobacco is always brown and the amount of residual chlorophyll is low, usually negligible, due to the degradation of chlorophyll during curing.

Preferably, the homogenized tobacco material comprises at least 0.1 milligrams of chlorophyll per gram on a dry weight basis. The presence of chlorophyll in the matrix at a level above 0.1 milligrams per gram of homogenized tobacco material on a dry weight basis is a clear indication that dried raw tobacco material has been incorporated.

Preferably, the homogenized 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.

The higher the level of dried raw tobacco material used in homogenizing the tobacco material, the higher the level of chlorophyll that will be present in the aerosol-generating substrate. However, even if the proportion of dried raw tobacco material forming the aerosol-generating substrate is relatively low, the level of chlorophyll in the substrate will be substantially higher than that present in a substrate formed solely from cooked tobacco material without any dried raw tobacco material.

The maximum level of chlorophyll within the aerosol-generating substrate will depend on the type and amount of raw tobacco material being dried within the aerosol-generating substrate. Typically, the homogenized tobacco material will comprise less than about 10.0 milligrams of chlorophyll per gram, or less than about 8.0 milligrams of chlorophyll per gram, on a dry weight basis.

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

A preferred method of measuring chlorophyll content of a sample of homogenized tobacco material containing dried raw tobacco material or a sample of dried raw tobacco material is 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 ".

In this method, an aqueous 80% acetone extract is produced from a sample of homogenized tobacco material and the absorbance of the extract at a specific wavelength is measured using a spectrophotometer. The levels of chlorophyll a and chlorophyll b can then be calculated using the formulas listed below:

chlorophyll a (μg/ml) =12.21 (a ₆₆₃ )-2.81(A ₆₄₆ )

Chlorophyll b (μg/ml) =20.13 (a) ₆₄₆ )–5.03(A ₆₆₃ )

Wherein A is ₆₆₃ Is the absorbance measured at 663nmDegree A ₆₄₆ Is the absorbance measured at 646 nm. The values of chlorophyll defined above in relation to the homogenized tobacco material of the invention correspond to the total chlorophyll content, which is the sum of the contents of chlorophyll a and chlorophyll b.

An alternative method of measuring chlorophyll content of a sample of homogenized tobacco material containing dried raw tobacco material or a sample of dried raw tobacco material is found in "pora, 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", using an alternative formula:

chlorophyll a (μg/ml) =12.25 (a _663.6 )-2.55(A _646.6 )

Chlorophyll b (μg/ml) =20.31 (a) _646.6 )-4.91(A _663.6 )

Wherein A is _663.6 Absorbance at 663.6nm and A _646.6 Is the absorbance measured at 646.6 nm.

All other components of the dried raw tobacco material mentioned below can be measured by suitable GC-MS or LC-MS techniques, which will be well known to the skilled person.

It has been found that the inclusion of dried raw tobacco material in the aerosol-generating substrate of the present invention advantageously provides a reduction in the level of asparagine in the aerosol-generating substrate, as compared to an equivalent aerosol-generating substrate formed solely from cooked tobacco material.

Preferably, the homogenized 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.

An aerosol-generating substrate according to the invention will typically comprise lower levels of asparagine than an aerosol-generating substrate formed from cured tobacco material alone, as it has been found that levels of asparagine in tobacco leaves can increase significantly during curing. For example, for certain tobacco types, it has been found that the level of asparagine in tobacco leaves is more than 20-fold higher after the tobacco leaves are cured than the uncooked tobacco leaves.

Preferably, the dried raw tobacco material has not been genetically modified, in particular, it has not been genetically modified to reduce asparagine content.

Preferably, the dried raw tobacco material is substantially free of added asparaginase. Thus, the asparaginase present in the dried raw tobacco material is only naturally occurring asparaginase.

The level of asparagine in tobacco leaves varies with the type of tobacco. In certain preferred embodiments, the aerosol-generating substrate comprises dried raw tobacco material derived from burley tobacco. The dried raw burley tobacco material preferably comprises no more than about 0.5 milligrams of asparagine per gram on a dry weight basis.

The asparagine content of homogenized tobacco material may be measured using known spectroscopic techniques. A preferred method for determining asparagine content is described in MP 1471rev 5 (2011) of Chelab Silieker S.r.l.Merieux Nutrisciences Company. Another suitable method is described in UNI EN ISO 13903:2005. Another 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. Moldovienu et al "(DOI: 10.1515/ctr-2015-0023).

Thus, the resulting aerosol generated from the aerosol-generating substrate according to the invention advantageously has a significantly lower level of acrylamide, which is generated by asparagine during heating of the aerosol-generating substrate.

Preferably, upon heating an aerosol-generating substrate according to the invention under the conditions according to test method a, the aerosol generated comprises 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.

For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried raw tobacco material from burley tobacco, the level of acrylamide in the aerosol generated from the substrate preferably does not exceed about 4 micrograms of acrylamide per gram of substrate, preferably does not exceed about 3 micrograms of acrylamide per gram of substrate, when the substrate is heated in accordance with test method a.

For the purposes of the present invention, the aerosol-generating substrate is heated according to "test method a". In test method a, an aerosol-generating article incorporating an aerosol-generating substrate was heated in a tobacco heating system 2.2 holder (THS 2.2 holder) under a Health Canada machine smoking regime. For the purpose of performing test method a, an aerosol-generating substrate was provided in an aerosol-generating article compatible with the THS2.2 holder.

The tobacco heating system 2.2 holder (THS 2.2 holder) corresponds to a commercially available IQOS device (Philip Morris Products SA (switzerland)), as described in Smith et al, 2016, regul. Protocol. Pharmacol.81 (S2) S82-S92. Aerosol-generating articles for use in conjunction with IQOS devices are also commercially available.

The Health Canada smoking regime is a well-defined and accepted smoking regime as defined in the Health Canada 2000-Tobacco Products Information Regulations SOR/2000-273, schedule 2 (Health Canada 2000-tobacco product information Act SOR/2000-273, plan 2) published by Ministry of Justice Canada. The test method is described in ISO/TR 19478-1:2014. In the Health Canada smoking test, 12 puffs of aerosol were collected from a sample aerosol-generating substrate, a puff volume of 55 mm, a puff duration of 2 seconds, a puff interval of 30 seconds, and if ventilation was present, all ventilation was blocked.

Thus, in the context of the present invention, the expression "when heating an aerosol-generating substrate according to test method a" means when heating an aerosol-generating substrate in a THS2.2 holder under the Health Canada 2000-tobacco product information provision SOR/2000-273, health Canada machine smoking regime defined in plan 2, published as Ministry of Justice Canada, the test method being described in ISO/TR 19478-1:2014.

For analytical purposes, depending on the analytical method to be used, the aerosol generated from the heated aerosol-generating substrate is captured using a suitable device. The aerosols may then be analyzed using known spectroscopic techniques such as liquid chromatography techniques or gas chromatography techniques known to the skilled artisan.

It has also been found that the inclusion of dried raw tobacco material in the aerosol-generating substrate of the present invention advantageously provides a reduction in ammonia levels in the aerosol-generating substrate, as compared to an equivalent aerosol-generating substrate formed solely from cooked tobacco material.

Preferably, the homogenized 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 ammonia level than an aerosol-generating substrate formed from cured tobacco material alone, as it has been found that the ammonia level in tobacco leaves increases significantly during curing. For example, for certain tobacco types, it has been found that the level of ammonia in tobacco leaves is more than 20 times higher after the tobacco leaves are cured than the uncooked tobacco leaves.

The level of ammonia in the homogenized tobacco material may be measured according to Coresta recommendation No. 79, "Determination of Ammonia in Tobacco and Tobacco Products by Ion Chromatographic Analysis" (month 3 of 2018).

The level of ammonia in tobacco leaves varies with the type of tobacco. In certain preferred embodiments, the aerosol-generating substrate comprises dried raw tobacco material derived from burley tobacco. The dried raw burley tobacco material preferably comprises no more than about 0.2 milligrams of ammonia per gram on a dry weight basis.

Thus, the resulting aerosol generated from the aerosol-generating substrate according to the invention advantageously has a significantly lower ammonia level, ammonia volatilizing from the aerosol-generating substrate during heating.

Preferably, when an aerosol-generating substrate according to the invention is heated under the conditions according to test method a, the aerosol generated comprises 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.

For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried raw tobacco material from burley tobacco, the level of ammonia in the aerosol generated from the substrate preferably does not exceed about 40 micrograms of acrylamide per gram of substrate, preferably does not exceed about 30 micrograms of ammonia per gram of substrate, when the substrate is heated in accordance with test method a.

It has also been found that the inclusion of dried raw tobacco material in the aerosol-generating substrate of the present invention advantageously provides a reduction in the level of total free amino acids in the aerosol-generating substrate, as compared to an equivalent aerosol-generating substrate formed solely from cooked tobacco material.

Preferably, the homogenized tobacco material comprises no more than about 12 milligrams total free amino acid per gram, more preferably no more than about 8 milligrams total free amino acid per gram, and most preferably no more than about 6 milligrams total free amino acid per gram, on a dry weight basis. An aerosol-generating substrate according to the invention will generally comprise a lower total free amino acid level than an aerosol-generating substrate formed from cured tobacco material alone, as it has been found that the total free amino acid level in tobacco leaves increases significantly during curing. For example, for certain tobacco types, it has been found that the level of total free amino acids in tobacco leaves is more than 5 times higher after the tobacco leaves are cured than the uncooked raw tobacco leaves.

The level of total free amino acids in tobacco leaves varies with the type of tobacco. In certain preferred embodiments, the aerosol-generating substrate comprises dried raw tobacco material derived from burley tobacco. The dried raw burley tobacco material preferably comprises no more than about 20 milligrams of total free amino acids per gram on a dry weight basis.

The resulting aerosol generated from the aerosol-generating substrate according to the invention thus advantageously has significantly lower levels of hydrogen sulfide and methyl mercaptan, which are generated from free amino acids in the aerosol-generating substrate during heating.

Preferably, upon heating an aerosol-generating substrate according to the invention under the conditions according to test method a, the aerosol generated comprises no more than about 6 micrograms of hydrogen sulfide per gram of substrate, preferably no more than about 5 micrograms of hydrogen sulfide per gram of substrate.

For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried raw tobacco material from burley tobacco, the level of hydrogen sulfide in the aerosol generated from the substrate when the substrate is heated according to test method a preferably does not exceed about 6 micrograms of hydrogen sulfide per gram of substrate, preferably does not exceed about 5 micrograms of hydrogen sulfide per gram of substrate.

Preferably, when an aerosol-generating substrate according to the invention is heated under the conditions according to test method a, the aerosol generated comprises no more than about 10 micrograms of methyl mercaptan per gram of substrate, preferably no more than about 9 micrograms of methyl mercaptan per gram of substrate.

For preferred embodiments of the invention in which the aerosol-generating substrate comprises dried raw tobacco material from burley tobacco, the level of methyl mercaptan in the aerosol generated from the substrate preferably does not exceed about 10 micrograms of methyl mercaptan per gram of substrate, preferably does not exceed about 9 micrograms of methyl mercaptan per gram of substrate, when the substrate is heated in accordance with test method a.

The reduction of the levels of hydrogen sulfide and methane glycol in the aerosols produced from the aerosol-generating substrates of the invention is advantageous because these compounds are known to cause undesirable sulfur flavors during heating.

It has also been found that the inclusion of dried raw tobacco material in the aerosol-generating substrate of the present invention advantageously provides a reduction in the level of certain TSNAs (tobacco specific nitrosamines) in the aerosol-generating substrate, as compared to an equivalent aerosol-generating substrate formed solely from cooked tobacco material.

For example, aerosol-generating substrates according to the invention will typically comprise lower levels of NNN (N-nitrosonornicotine) than aerosol-generating substrates formed from cured tobacco material alone, as NNN and other TSNA levels in tobacco leaves have been found to increase significantly during curing. For certain tobacco types, it has been found that the level of NNN in tobacco leaves is more than 5 times higher after the tobacco leaves are cured than in raw tobacco leaves that have not been cured.

The level of NNN in tobacco leaves varies with the type of tobacco. In certain preferred embodiments, the aerosol-generating substrate comprises dried raw tobacco material derived from burley tobacco. The dried raw burley tobacco material preferably comprises no more than about 500 nanograms of NNN per gram on a dry weight basis.

Thus, the resulting aerosol generated from the aerosol-generating substrate according to the invention advantageously has a significantly lower level of NNN, which volatilizes from the aerosol-generating substrate during heating.

It has been found that the inclusion of dried raw tobacco material in the aerosol-generating substrate of the present invention provides a significant increase in the level of Phosphatidylethanolamine (PE) in the aerosol-generating substrate, as compared to an equivalent aerosol-generating substrate formed solely from cooked tobacco material. PE is a chloroplast outer lipid found in plant membranes. The presence of PE above a certain threshold level clearly indicates the inclusion of dried raw tobacco material within the aerosol-generating substrate. It has been found that the levels of some PE molecular species, including PE 36:6, PE 34:3, PE 36:5, and PE 34:2, are at least 8-fold, and in some cases at least 10-fold higher in the dried raw tobacco material than in the cured tobacco material of the same tobacco type.

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

Preferably, the aerosol generated from the aerosol-generating substrate according to the invention during test method a further comprises at least about 0.1 micrograms of nicotine per gram of substrate, more preferably at least about 1 microgram of nicotine per gram of substrate, more preferably at least about 2 micrograms of nicotine per gram of substrate. Preferably, the aerosol comprises at most about 10 micrograms of nicotine per gram of substrate, more preferably at most about 7.5 micrograms of nicotine per gram of substrate, more preferably at most about 4 micrograms of nicotine per gram of substrate. For example, the aerosol may comprise about 0.1 micrograms to about 10 micrograms of nicotine per gram of substrate, or about 1 micrograms to about 7.5 micrograms of nicotine per gram of substrate, or about 2 micrograms to about 4 micrograms of nicotine per gram of substrate. In some embodiments of the invention, the aerosol may contain zero micrograms of nicotine.

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

The aerosol generated from the aerosol-generating substrate according to the invention during test method a may further comprise at least about 5 mg of aerosol-former per gram of aerosol-generating substrate, or at least about 10 mg of aerosol per gram of substrate, or at least about 15 mg of aerosol-former per gram of substrate. Alternatively or additionally, the aerosol may comprise up to about 30 milligrams of aerosol former per gram of matrix, or up to about 25 milligrams of aerosol former per gram of matrix, or up to about 20 milligrams of aerosol former per gram of matrix. For example, the aerosol may comprise from about 5 mg to about 30 mg of aerosol former per gram of matrix, or from about 10 mg to about 25 mg of aerosol former per gram of matrix, or from about 15 mg to about 20 mg of aerosol former per gram of matrix. In alternative embodiments, the aerosol may comprise less than 5 milligrams of aerosol former per gram of substrate. This may be suitable, for example, if the aerosol-forming agent is provided separately within the aerosol-generating article or the aerosol-generating device.

Suitable aerosol formers for use in the present invention are described below.

Various methods known in the art may be applied to measure the amount of aerosol former in an aerosol.

Preferably, the homogenized tobacco material of the aerosol-generating substrate according to the invention comprises at least about 1 weight percent dried raw tobacco material, on a dry weight basis. Preferably, the homogenized tobacco material comprises at least about 2 weight percent dried raw tobacco material, more preferably at least about 4 weight percent dried raw tobacco material, more preferably at least about 6 weight percent dried raw tobacco material, more preferably at least about 8 weight percent dried raw tobacco material, more preferably at least about 10 weight percent dried raw tobacco material, on a dry weight basis.

The homogenized tobacco material may comprise up to about 75 percent by weight dry raw tobacco material. Preferably, the homogenized tobacco material comprises at most about 70 weight percent dried raw tobacco material, more preferably at most about 65 weight percent dried raw tobacco material, more preferably at most about 60 weight percent dried raw tobacco material, more preferably at most about 55 weight percent dried raw tobacco material, more preferably at most about 50 weight percent dried raw tobacco material, on a dry weight basis.

For example, the homogenized tobacco material may comprise between about 1 weight percent and about 75 weight percent dried raw tobacco material, or between about 2 weight percent and about 70 weight percent dried raw tobacco material, or between about 4 weight percent and about 65 weight percent dried raw tobacco material, or between about 6 weight percent and about 60 weight percent dried raw tobacco material, or between about 8 weight percent and about 55 weight percent dried raw tobacco material, or between about 10 weight percent and about 50 weight percent dried raw tobacco material, on a dry weight basis.

In certain particularly preferred embodiments of the present invention, the homogenized tobacco material comprises between about 10 percent by weight and about 30 percent by weight dry raw tobacco material on a dry weight basis.

In certain embodiments of the present invention, the aerosol-generating plant material forming the homogenized tobacco material may comprise at least 98 weight percent dried raw tobacco material or at least 95 weight percent dried raw tobacco material or at least 90 weight percent dried raw tobacco material, based on the dry weight of the plant material. Thus, in such embodiments, the aerosol-generating substrate comprises dried raw tobacco material, and is substantially free of cooked tobacco material. For example, the plant material forming the homogenized tobacco material may comprise about 100 percent by weight of dried raw tobacco material.

In alternative embodiments of the invention, the homogenized tobacco material may comprise a combination of dried raw tobacco material and cooked tobacco material, as described below.

Alternatively or in addition to the cooked tobacco material, the homogenized tobacco material may comprise aerosol-generating plant material derived from one or more plants including, but not limited to, tea, ginger, eucalyptus, clove, peppermint, star anise, rosemary, chamomile, thyme and dill seed.

In the following description of the invention, the term "plant material" is used generically to refer to aerosol-generating plant material for forming an aerosol-generating substrate. The plant material may consist essentially of dried raw tobacco material, or may be a mixture of dried raw tobacco material and cooked 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 essentially of dried raw tobacco particles, or may be a mixture of dried raw tobacco particles and cooked tobacco particles. The term "plant material" does not include any inert plant material incorporated into the aerosol-generating substrate that does not contribute to the aerosol generated upon heating of the aerosol-generating substrate.

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

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

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

The term "cured tobacco material" is used in this specification to refer to material derived from tobacco plants that have been subjected to known curing processes for at least 5 days. Cured tobacco materials, such as cured tobacco leaves, will typically be brown in color and have chlorophyll levels of no more than 0.25 milligrams per gram on a dry weight basis.

The ratio of dried raw tobacco material to cooked tobacco material in the homogenized tobacco material may vary depending on the desired content of dried raw tobacco material in the homogenized tobacco material. Preferably, the ratio of dried raw tobacco material to cooked tobacco material in the homogenized tobacco material does not exceed 1 to 1 (1:1). In such embodiments, the amount by weight of cooked tobacco material in the homogenized tobacco material is equal to or greater than the amount by weight of dried raw tobacco material in the homogenized tobacco material on a dry weight basis.

For the purposes of the present invention, the term "tobacco material", whether referring to dried raw tobacco material or cooked tobacco material, may be any material of any plant member of the genus Nicotiana. The term "tobacco particles" includes ground or crushed tobacco lamina, ground or crushed tobacco leaf stem, tobacco dust, tobacco fines and other particulate tobacco by-products formed during the handling, manipulation and transportation of tobacco. In a preferred embodiment, the tobacco material is derived substantially entirely from tobacco leaf lamina. In contrast, the nicotine and nicotine salts that are separated are compounds derived from tobacco, but are not considered tobacco materials for the purposes of the present invention and are not included in the percentage of plant material.

The tobacco material may be prepared from one or more tobacco plants. Any type of tobacco may be used in the blend. Examples of tobacco types that may be used for the dried raw tobacco material include, but are not limited to, burley tobacco, maryland tobacco (Maryland tobacco), oriental tobacco (Oriental tobacco), virginia tobacco (Virginia tobacco), and other specialty tobaccos. Examples of tobacco types that may be used for the cured tobacco type include, but are not limited to, sun-cured tobacco, burley tobacco, maryland tobacco, oriental tobacco, virginia tobacco, and other specialty tobacco.

Burley tobacco plays an important role in many tobacco blends. Burley tobacco has a distinctive flavor and aroma, and also has the ability to absorb large amounts of add-on (stiffening).

Oriental tobacco is a tobacco having lamina and high aromatic quality. However, the flavor of Oriental tobacco is milder than that of burley tobacco, for example. Thus, a relatively small proportion of Oriental tobacco is typically used in tobacco blends.

Flue-cured tobacco is a method of curing tobacco, particularly with virginia tobacco. During the baking process, heated air is circulated through the densely packed tobacco. During the first stage, the tobacco leaves yellow and wilt. During the second stage, the leaves' leaves are completely dried. In the third stage, the peduncles are completely dried.

Kasturi, madura and jamm are all useful subtypes of sun-cured tobacco.

The dried raw tobacco material or the cooked tobacco material may comprise a blend of different tobacco types.

The tobacco material can have a nicotine content of at least about 2.5% by weight on a dry weight basis. More preferably, the tobacco material may have a nicotine content of at least about 3% by weight, even more preferably at least about 3.2% by weight, even more preferably at least about 3.5% by weight, most preferably at least about 4% by weight, on a dry weight basis. The curing process does not appear to affect the nicotine level of the tobacco leaves to a significant extent, so these values apply to both the dried raw tobacco material and the cured tobacco material, if present.

Nicotine may optionally be introduced into the aerosol-generating substrate, but for the purposes of the present invention this will be considered a non-tobacco material. The nicotine may comprise one or more nicotine salts selected from the list of: nicotine lactate, nicotine citrate, nicotine pyruvate, nicotine bitartrate, nicotine benzoate, nicotine pectate, nicotine alginate and nicotine salicylate. In addition to tobacco having a low nicotine content, nicotine may also be introduced, or nicotine may be introduced into an aerosol-generating substrate having a reduced or zero tobacco content.

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

Preferably, the homogenized tobacco material comprises at most about 50mg of nicotine per gram of substrate on a dry weight basis. More preferably, the homogenized tobacco material comprises at most about 45mg of nicotine per gram of substrate, more preferably at most about 40mg of nicotine per gram of substrate, more preferably at most about 35mg of nicotine per gram of substrate, more preferably at most about 30mg of nicotine per gram of substrate, more preferably at most about 25mg of nicotine per gram of substrate, more preferably at most about 20mg of nicotine per gram of substrate on a dry weight basis.

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

The defined range of nicotine content of the homogenized tobacco material includes all forms of nicotine that may be present in the homogenized tobacco material, including nicotine inherently present in the tobacco material and nicotine that has optionally been added separately to the homogenized tobacco material, e.g. in the form of nicotine salts.

The nicotine content of the homogenized tobacco material may be measured according to the hexane method described in Coresta recommendation method No. 62 "Determination of Nicotine in Tobacco and Tobacco Products by Gas Chromatographic Analysis" (month 4 2020).

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

In certain preferred embodiments, the total weight of the plant material is no more than about 75% by weight on a dry weight basis.

Thus, the plant material is combined with one or more other components to form a homogenized tobacco material.

As defined above, the homogenized tobacco material also comprises an aerosol former. Upon volatilization, the aerosol former may deliver other volatilized compounds such as nicotine and flavoring agents in the aerosol that are released from the homogenized tobacco material upon heating. Aerosolization of a particular compound from homogenized tobacco material is not solely determined by its boiling point. The amount of aerosolized compound can be affected by the physical form of the matrix as well as other components that are also present in the matrix. The stability of a compound at the temperature and time range of aerosolization will also affect the amount of compound present in the aerosol.

Suitable aerosol-formers included in homogenized 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 monoacetin, diacetin or triacetin; and aliphatic esters of mono-, di-or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. The homogenized tobacco material may comprise a single aerosol-former, or a combination of two or more aerosol-formers.

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

The amount of aerosol former may be adjusted according to the composition of the homogenized tobacco material, such as the type or amount of plant material, in order to obtain an aerosol having a desired level of flavour compounds from the plant material. The amount of aerosol-forming agent may also be adjusted according to the manner in which the aerosol-generating substrate is intended to be heated during use, in particular the temperature to which the aerosol-generating article will be heated during heating in the relevant aerosol-generating device.

The homogenized tobacco material preferably has an aerosol former content of between about 5 wt.% and about 55 wt.% on a dry weight basis, such as between about 10 wt.% and about 45 wt.% on a dry weight basis, or between about 15 wt.% and about 40 wt.% on a dry weight basis.

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

Alternatively, the aerosol former content may be between about 15 wt% to about 55 wt% on a dry weight basis. For example, in an alternative preferred embodiment homogenized tobacco material in accordance with the invention, the aerosol former content is preferably between about 15 weight percent and about 55 weight percent, more preferably between about 25 weight percent and about 50 weight percent, more preferably between about 35 weight percent and about 45 weight percent, on a dry weight basis.

In other embodiments, the homogenized tobacco material may have an aerosol former content of from about 1 weight percent to about 5 weight percent on a dry weight basis. For example, if the substrate is intended for an aerosol-generating article in which the aerosol-former is held in a reservoir separate from the substrate, the substrate may have an aerosol-former content of greater than 1% and less than about 5%. In such embodiments, the aerosol-forming agent volatilizes upon heating and the flow of aerosol-forming agent contacts the homogenized tobacco material so as to entrain flavor from the homogenized tobacco material in the aerosol.

The aerosol former may act as a humectant in the homogenized tobacco material.

As defined above, the homogenized tobacco material also comprises a binder to alter the mechanical properties of the plant material, wherein said binder is comprised in the homogenized tobacco material during manufacture as described herein. Suitable exogenous binders are known to those skilled in the art and include, but are not limited to: gums such as guar gum, xanthan gum, acacia 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 starch; organic acids such as alginic acid; conjugate base salts of organic acids such as sodium alginate, agar and pectin; and combinations thereof. Preferably, the binder comprises guar gum.

Preferably, the binder is present in an amount of about 1% to about 10% by weight, preferably about 2% to about 9% by weight, more preferably about 3% to about 8% by weight, on a dry weight basis.

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

In certain embodiments, the homogenized tobacco material preferably comprises between about 2 weight percent and about 10 weight percent binder, based on dry weight, wherein the binder is most preferably a cellulose ether. For example, in an aerosol-generating article according to the second preferred embodiment, the homogenized tobacco material preferably comprises between about 2 weight percent and about 10 weight percent of a binder, based on dry weight, wherein the binder is preferably a cellulose ether. Particularly preferably, the binder is carboxymethyl cellulose (CMC).

In addition, the homogenized tobacco material of any of the embodiments may optionally further comprise additional cellulose. For example, the homogenized tobacco material may comprise between about 5 percent and about 50 percent by weight of additional cellulose.

As used herein, the term "additional cellulose" encompasses any cellulosic material incorporated into the homogenized tobacco material that is not derived from tobacco material provided in the homogenized tobacco material. Thus, in addition to the tobacco material, additional cellulose is incorporated into the homogenized tobacco material as a separate and distinct source of cellulose from any cellulose inherently provided within the tobacco material. The additional cellulose is typically derived from a plant different from the tobacco material. Preferably, the further cellulose is in the form of an inert cellulosic material which is perceptually inert and thus does not substantially affect the organoleptic properties of the aerosol generated from the homogenized tobacco material. For example, the additional cellulose is preferably a tasteless and odorless material.

The additional cellulose may be composed of one type of cellulose material, or may be a combination of different types of cellulose materials that provide different properties, as described in more detail below.

The additional cellulose incorporated in the homogenized tobacco material in accordance with the invention is believed to provide additional structure and reinforcement to bind and support the plant material and aerosol-former within the homogenized tobacco material.

The incorporation of additional cellulose has been found to be particularly beneficial in homogenized tobacco materials in which the binder as described above comprises a cellulose ether. It has been advantageously found that combining cellulose ether with additional cellulosic material at certain defined levels and within defined ratios as set forth below provides a homogenized tobacco material having improved tensile strength and homogeneity.

Preferably, the ratio of additional cellulosic material to cellulose ether in the homogenized tobacco material is at least 2.

Preferably, the additional cellulose comprises cellulose powder. The term "cellulose powder" as used herein refers to refined cellulose material in powder form derived from cellulose fibers. Preferably, the cellulose powder is formed from particles having an average particle size of less than 100 microns. The cellulose powder may be in the form of microcrystalline cellulose. Cellulose powders suitable for use in the present invention may be microcrystalline cellulose SK-105 or SK-101 or cellulose powder M-60 type obtained from Gumix International, inc.

Preferably, the amount of cellulose powder corresponds to at least about 5% by weight of the homogenized tobacco material, more preferably at least about 6% by weight of the homogenized tobacco material, more preferably at least about 7% by weight of the homogenized tobacco material, more preferably at least about 8% by weight of the homogenized tobacco material, on a dry weight basis.

The amount of cellulose powder may be adjusted above this minimum level depending on the weight amount of other components in the homogenized tobacco material, in particular depending on the weight amount of plant material. In certain embodiments, the cellulose powder may replace a proportion of the plant material within the homogenized tobacco material without significantly affecting the characteristics of the aerosol produced.

Preferably, the amount of cellulose powder corresponds to no more than about 45% by weight of the homogenized tobacco material on a dry weight basis, more preferably no more than about 40% by weight of the homogenized tobacco material.

In certain embodiments, for example, in embodiments where there is a relatively high level of plant material in the homogenized tobacco material, the amount of cellulose powder may be relatively low. In such embodiments, the amount of cellulose powder may be between about 5% and about 15% by weight of the homogenized tobacco material, or between about 6% and about 12% by weight of the homogenized tobacco material, or between about 7% and about 11% by weight of the homogenized tobacco material, or between about 8% and about 10% by weight of the homogenized tobacco material, on a dry weight basis.

In other embodiments, for example, in embodiments where the homogenized tobacco material has a relatively low level of aerosol-generating plant material, the amount of cellulose powder may be relatively high. In such embodiments, the amount of cellulose powder may be between about 15% to about 45% by weight of the homogenized tobacco material, or between about 20% to about 40% by weight of the homogenized tobacco material, or between about 25% to about 35% by weight of the homogenized tobacco material, on a dry weight basis.

Preferably, where the homogenized tobacco material comprises cellulose ether and cellulose powder, the weight ratio of cellulose powder to cellulose ether in the homogenized 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 weight ratio of cellulose powder to cellulose ether in the homogenized tobacco material is at least about 1.6, more preferably at least about 1.8.

Alternatively or in addition to the cellulose powder, the further cellulose may comprise cellulose fibres. The term "cellulosic fiber" as used herein refers to fibers obtained directly from plant-based materials, wherein each fiber has a length that is substantially greater than its width. The cellulose fibers preferably have a fiber length of at least 400 microns. Cellulosic fibers suitable for use in the present invention include, for example, wood pulp fibers. Suitable sources of cellulose fibers for use in the present invention may be obtained from Storaenso, sweden as ECF bleached hardwood kraft pulp.

Cellulose fibres may advantageously be used as mechanical reinforcement in homogenized tobacco material forming an aerosol-generating substrate of an aerosol-generating article according to the invention. Cellulose fibers can improve the incorporation of plant material in homogenized tobacco material and provide improved tensile strength, particularly when combined with cellulose ether binders.

Preferably, the amount of cellulosic fibers corresponds to at least about 3% by weight of the homogenized tobacco material on a dry weight basis, more preferably at least about 4% by weight of the homogenized tobacco material, more preferably at least about 5% by weight of the homogenized tobacco material, more preferably at least about 6% by weight of the homogenized tobacco material.

Preferably, the amount of cellulosic fibers corresponds to no more than about 12% by weight of the homogenized tobacco material, more preferably at least about 11% by weight of the homogenized tobacco material, more preferably at least about 10% by weight of the homogenized tobacco material, more preferably at least about 8% by weight of the homogenized tobacco material, on a dry weight basis.

For example, the homogenized tobacco material may comprise from about 3 weight percent to about 12 weight percent cellulosic fibers, or from about 4 weight percent to about 11 weight percent cellulosic fibers, or from about 5 weight percent to about 10 weight percent cellulosic fibers, or from about 6 weight percent to about 8 weight percent cellulosic fibers, on a dry weight basis.

Preferably, where the homogenized tobacco material comprises cellulose ether and cellulose fiber, the weight ratio of cellulose fiber to cellulose ether in the homogenized 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 weight ratio of cellulosic fibers to cellulose ether in the homogenized tobacco material is at least about 0.75, more preferably at least about 1.

In a preferred embodiment, the additional cellulose comprises cellulose powder and cellulose fibers. In such embodiments, the weight ratio of cellulose powder to cellulose fiber is preferably at least about 1.5, more preferably at least about 1.75, and more preferably at least about 2.

Preferably, the amount of further cellulose provided in the homogenized tobacco material is adjusted such that the total amount of further cellulose and plant material corresponds to no more than 75 wt-% of the homogenized tobacco material. Thus, preferably, at least about 25% by weight of the homogenized tobacco material is provided by other components, including cellulose ether and aerosol former.

In an aerosol-generating article according to the second preferred embodiment of the invention, the homogenized tobacco material preferably comprises between about 2 weight percent and about 10 weight percent cellulose ether and between about 5 weight percent and about 50 weight percent additional cellulose on a dry weight basis. Preferably, the ratio of additional cellulose to cellulose ether is at least 2.

In addition to the above components, the homogenized tobacco material may optionally further comprise one or more lipids to facilitate diffusion of volatile components (e.g., aerosol former and nicotine), wherein the lipids are included into the homogenized plant material during manufacture as described herein. Suitable lipids for inclusion in the homogenized 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, candelilla wax, carnauba wax, shellac, sunflower wax, sunflower oil, rice bran and level a; and combinations thereof.

Alternatively or additionally, the homogenized tobacco material may also comprise a pH adjuster.

Alternatively or additionally, the homogenized tobacco material may also comprise fibers to alter the mechanical properties of the homogenized tobacco material, wherein the fibers are included into the homogenized tobacco material during manufacture as described herein. Suitable exogenous fibers for inclusion in homogenized tobacco material are known in the art and include fibers formed from non-tobacco material and non-tobacco material, including, but not limited to: cellulose fibers; cork fiber; a hardwood fiber; jute fibers and combinations thereof. Exogenous fibers derived from tobacco and/or tobacco may also be added. Any fibers added to the homogenized tobacco material are not considered to form part of the "plant material" as defined above. Prior to inclusion in the homogenized tobacco material, the fibers may be treated by suitable processes known in the art, including, but not limited to: mechanical pulping; refining; chemical pulping; bleaching; pulping by sulfate; and combinations thereof. The fibers typically have a length that is greater than their width.

Suitable fibers generally have a length greater than 400 microns and less than or equal to 4mm, preferably in the range of 0.7mm to 4 mm. Preferably, the fibers are present in an amount of at least about 2% by weight based on the dry weight of the matrix. The amount of fibers in the homogenized tobacco material may depend on the type of material and in particular the method used to produce the homogenized tobacco material. In some embodiments, the fibers may be present in an amount of about 2 wt% to about 15 wt%, most preferably about 4 wt%, based on the dry weight of the matrix. For example, when the homogenized tobacco material is in the form of cast leaves, such levels of fibers may be present. In other embodiments, the fibers may be present in an amount of at least about 30 wt% or at least about 40 wt%. For example, when the homogenized tobacco material is a tobacco paper formed during the papermaking process, it is likely that such higher levels of fibers will be provided.

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

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

The homogenized tobacco material may be provided in any suitable form. For example, the homogenized tobacco material may be in the form of one or more sheets. As used herein with reference to the present invention, the term "sheet" describes a layered element having a width and length substantially greater than its thickness.

Alternatively or additionally, the homogenized tobacco material may be in the form of a plurality of pellets or granules.

Alternatively or additionally, the homogenized tobacco material may be in a form that is capable of being filled with cartridges or hookah consumables, or may be in a form that is capable of being used in a hookah apparatus. The invention includes a cartridge or hookah apparatus for containing homogenized tobacco material.

Alternatively or additionally, the homogenized tobacco material may be in the form of a plurality of strands, bars or pieces. As used herein, the term "strand" describes an elongated element material having a length substantially greater than its width and thickness. The term "strand" should be considered to include strands, pieces and any other homogenized tobacco material having a similar form. The strand of homogenized tobacco material may be formed from a sheet of homogenized tobacco material, e.g. by cutting or shredding, or by other methods, e.g. by extrusion methods.

In some embodiments, the strand may be formed in situ within the homogenized tobacco material due to splitting or splitting of the sheet of homogenized tobacco material during formation of the homogenized tobacco material, e.g. due to crimping. The strands of homogenized tobacco material within the homogenized tobacco material may be separated from each other. Alternatively, each strand of homogenized tobacco material within homogenized tobacco material may be connected to adjacent one or more strands at least partially along the length of the strand. For example, adjacent strips may be connected by one or more fibers. This may occur, for example, in the case of the formation of strips due to the splitting of sheets of homogenized tobacco material during the production of homogenized tobacco material, as described above.

Preferably, the homogenized tobacco material is in the form of one or more sheets of homogenized tobacco material. In various embodiments of the invention, one or more sheets of homogenized tobacco material may be produced by a casting process. In various embodiments of the invention, one or more sheets of homogenized tobacco material may be produced by a papermaking process. The one or more sheets as described herein may each individually have a thickness of between 100 and 600 microns, preferably between 150 and 300 microns, and most preferably between 200 and 250 microns. The individual thickness refers to the thickness of the individual sheets, while the combined thickness refers to the total thickness of all sheets constituting the aerosol-generating substrate. For example, if the aerosol-generating substrate is formed from two separate sheets, the combined thickness is the sum of the thicknesses of the two separate sheets or the measured thickness of the two sheets in case the two sheets are stacked in the aerosol-generating substrate.

One or more sheets as described herein may each individually have about 100g/m ² To about 300g/m ² Or about 100g/m ² To about 200g/m ² Gram weight per square meter.

One or more sheets as described herein may each independently have about 0.3g/cm ³ To about 1.3g/cm ³ Preferably about 0.7g/cm ³ To about 1.0g/cm ³ Is a density of (3).

In embodiments of the 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 agglomerated sheets. As used herein, the term "gathered" means that a sheet of homogenized tobacco material is rolled, folded or otherwise compressed or contracted substantially transverse to the cylindrical axis of a rod or rod. The step of "gathering" the sheet material may be performed by any suitable means that provides the necessary lateral compression of the sheet material.

As used herein, the term "longitudinal" refers to a direction corresponding to a major longitudinal axis of the aerosol-generating article extending between an upstream end and a downstream end of the aerosol-generating article. During use, air is drawn through the aerosol-generating article in a longitudinal direction. The term "transverse" refers to a direction 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 rod or bar having a circular cross-section, the maximum width corresponds to the diameter of the circle.

As used herein, the term "rod" means a generally cylindrical element having a substantially polygonal, circular, oval or elliptical cross-section. As used herein, the term "strip" refers to a generally cylindrical element having a generally polygonal cross-section and preferably having a circular, oval or elliptical cross-section. The length of the bar may be greater than or equal to the length of the rod. Typically, the length of the bar is greater than the length of the bar. The strip may comprise one or more bars, preferably aligned longitudinally.

As used herein, the terms "upstream" and "downstream" describe the relative positions of an element or portion of an element of an aerosol-generating article with respect to the direction in which an aerosol is transported through the aerosol-generating article during use. The downstream end of the airflow path is the end of the aerosol that is delivered to the user of the article.

One or more sheets of homogenized tobacco material may be gathered transversely with respect to its longitudinal axis and surrounded by a wrapper to form a continuous rod or stick. The continuous strip may be cut into a plurality of discrete strips or bars. The wrapper may be a paper wrapper or a non-paper wrapper, as described in more detail below. Tobacco leaf

Alternatively, one or more sheets of homogenized tobacco material may be cut into strips as described above. In such embodiments, the aerosol-generating substrate comprises a plurality of strands of homogenized tobacco material. The thin strips may be used to form a rod. Typically, such strips have a width of at least about 0.2mm, or at least about 0.5mm. Typically, such strips have a width of no more than about 5mm, or about 4mm, or about 3mm, or about 1.5mm. For example, the width of the strands may be between about 0.25mm to about 5mm, or between about 0.25mm to about 3mm, or between about 0.5mm to about 1.5mm.

The length of the strand is preferably greater than about 5mm, for example between about 5mm and about 20mm, or between about 8mm and about 15mm, or about 12mm. Preferably, the strips have substantially the same length as each other. The length of the thin strip may be determined by the manufacturing process whereby the strip is cut into shorter bars and the length of the thin strip corresponds to the length of the bars. The strands may be fragile, which may lead to breakage, especially during transportation. In this case, some of the strands may be less in length than the rod.

The plurality of strips preferably extend substantially longitudinally along the length of the aerosol-generating substrate in alignment with the longitudinal axis. Preferably, the plurality of strips are thus aligned substantially parallel to each other.

The strands of homogenized tobacco material preferably each have a mass-to-surface area ratio of at least about 0.02 milligrams per square millimeter, more preferably at least about 0.05 milligrams per square millimeter. Preferably, the strands of homogenized tobacco material each have a mass to surface area ratio of no more than about 0.2 milligrams per square millimeter, more preferably no more than about 0.15 milligrams per square millimeter. The mass-to-surface area ratio is calculated by dividing the mass (in milligrams) of the strand of homogenized tobacco material by the geometric surface area (in square millimeters) of the strand of homogenized tobacco material.

One or more sheets of homogenized tobacco material may be textured by crimping, embossing or perforating. One or more sheets may be textured prior to gathering or prior to cutting into thin strips. Preferably, one or more sheets of homogenized tobacco material are crimped prior to aggregation, so that the homogenized tobacco material may be in the form of crimped sheets, more preferably in the form of aggregated crimped sheets. As used herein, the term "crimped sheet" refers to a sheet having a plurality of substantially parallel ridges or corrugations that are generally aligned with the longitudinal axis of the article.

In one embodiment, the aerosol-generating substrate may be in the form of a single rod of homogenized tobacco material. In other embodiments, the aerosol-generating substrate may be in the form of two or more rods of homogenized tobacco material, wherein the rods of homogenized tobacco material may be formed from the same or different homogenized tobacco material.

Aerosol-generating substrates according to the present invention may be produced by a variety of methods including papermaking, casting, mass reconstruction, extrusion or any other suitable process. Preferably, the aerosol-generating substrate is a homogenized tobacco material.

Preferably, the homogenized tobacco material is in the form of "cast leaves". 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 (e.g., guar gum) onto a support surface, such as a belt conveyor, drying the slurry, and removing the dried sheet from the support surface. For the manufacture of cast leaf tobacco, examples of casting or cast leaf processes are described, for example, in U.S. Pat. No. 5,724,998. In the cast leaf process, particulate plant material is mixed with a liquid component (typically water) to form a slurry. Other additional components in the slurry may include fibers, binders, and aerosol formers. The particulate plant material may agglomerate in the presence of a binder. The slurry is cast onto a support surface and dried to form a sheet of homogenized tobacco material.

In certain preferred embodiments, the homogenized tobacco material used in the article according to the invention is produced by casting. Homogenized tobacco material prepared by a casting process typically includes agglomerated particulate plant material.

In the cast leaf process, most of the flavoring agent is advantageously preserved because substantially all of the soluble fraction remains in the plant material. In addition, energy intensive papermaking steps are avoided.

In a preferred embodiment of the invention, to form a homogenized tobacco material, a mixture is formed comprising particulate plant material, water, a binder and an aerosol former. A sheet is formed from the mixture and then dried. Preferably, the mixture is an aqueous mixture. As used herein, "dry weight" refers to the weight of a particular nonaqueous component relative to the sum of the weights of all nonaqueous components in the mixture, expressed as a percentage. The composition of the aqueous mixture may be expressed in terms of "dry weight percent". This means that the non-aqueous component is expressed as a percentage relative to the weight of the entire aqueous mixture.

The mixture may be a slurry. As used herein, a "slurry" is a homogenized aqueous mixture having a relatively low dry weight. The slurry used in this method preferably has a dry weight of 5% to 60%.

Alternatively, the mixture may be a mass. As used herein, a "briquette" is an aqueous mixture having a relatively high dry weight. The agglomerates used in the methods herein preferably have a dry weight of at least 60%, more preferably at least 70%.

In certain embodiments of the method of the present invention, it is preferred to include greater than 30% dry weight of the slurry and agglomerates.

The step of mixing the particulate plant material, water and other optional components may be carried out by any suitable method. For low viscosity mixtures, i.e. some slurries, it is preferred to use a high energy mixer or a high shear mixer for mixing. This mixing breaks down and evenly distributes the phases of the mixture. For higher viscosity mixtures, i.e. some agglomerates, a kneading process can be used to uniformly distribute the various phases of the mixture.

The method according to the invention may further comprise the step of vibrating the mixture to dispense the various components. Vibrating the mixture, i.e. for example vibrating a tank or silo in which the homogenized mixture is present, may assist in the homogenization of the mixture, especially when the mixture is a low viscosity mixture, i.e. some slurries. If vibration and mixing are performed, less mixing time may be required to homogenize the mixture to the target value optimal for casting.

If the mixture is a slurry, the web of homogenized tobacco material is preferably formed by a casting process that includes casting the slurry on a support surface, such as a belt conveyor. A method for producing homogenized tobacco material includes the step of drying the 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 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 dried sheet is between about 5% and about 15% based on the total weight of the sheet. Then, after drying, the sheet may be removed from the support surface. The cast sheet has a tensile strength such that it can be mechanically handled and wound or unwound from a roll without breaking or deforming.

If the mixture is a pellet, the pellet may be extruded in the form of a sheet, strand or bar prior to the step of drying the extruded mixture. Preferably, the mass can be extruded in the form of a sheet. The extrusion 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 extrusion 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 extrusion mixture may be dried at a temperature 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% to about 15% based on the total weight of the sheet. Sheets formed from the agglomerates require less drying time and/or lower drying temperature because of the significantly lower moisture content relative to webs formed from the slurry.

After the sheet has been dried, the method may optionally comprise the step of applying A nicotine salt, preferably together with an aerosol former, to the sheet, as described in WO-A-2015/082652.

After the sheet has been dried, the method according to the invention may optionally comprise the step of cutting the sheet into strips, fragments or sticks for forming an aerosol-generating substrate as described above. The strips, fragments or ribbons may be brought together using suitable means to form a ribbon of aerosol-generating substrate. In the formed strips of aerosol-generating substrate, the thin strips, fragments or strips may for example be substantially aligned in the longitudinal direction of the strips. Alternatively, the thin strips, chips or strips may be randomly oriented in the strip.

The method according to the invention may optionally further comprise the step of winding the sheet onto a reel after the drying step.

The homogenized tobacco material of the invention may alternatively be produced by a papermaking process that produces sheets of homogenized plant material in the form of plant "paper". Plant paper refers to reconstituted plant sheet formed by a process in which plant material is extracted with a solvent to produce an extract of soluble plant compounds and insoluble residues of fibrous plant material and the extract is recombined with the insoluble residues. 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 fibers prior to recombination with the extract. In the method according to the invention, the plant material will comprise tobacco particles, optionally in combination with tobacco particles.

In more detail, the method of producing a plant paper comprises a first step of mixing plant material and water to form a dilute suspension. The dilute suspension mainly comprises individual cellulose fibers. The suspension has a lower viscosity and a higher water content than the slurry produced in the casting process. This first step may comprise soaking, optionally in the presence of a base such as sodium hydroxide, and optionally applying heat.

The method further comprises a second step of separating the suspension into an insoluble fraction comprising insoluble residues of the fibrous plant material and a liquid or aqueous extract comprising soluble plant compounds. The water remaining in the insoluble residues of the fibrous plant material can be drained through the screen acting as a sieve, so that a web of randomly interwoven fibers can be laid down. The water may be further removed from this web by pressing with rollers, sometimes with suction or vacuum assistance.

After removal of the aqueous portion and water, insoluble residues are formed into sheets. Preferably, a substantially flat, uniform sheet of plant fibers is formed.

Preferably, the method further comprises the steps of concentrating the extract of soluble plant compounds removed from the sheet and adding the concentrated extract to the sheet of insoluble residues of fibrous plant material to form a sheet of homogenized plant material. Alternatively or additionally, soluble plant material or concentrated plant material from another method may be added to the sheet. The extract or concentrated extract may be from another variety of the same plant species or from another plant species.

Such se:Sup>A process has been used with tobacco to manufacture reconstituted tobacco products, also known as tobacco paper, as described in US-se:Sup>A-3,860,012.

In certain preferred embodiments, the homogenized tobacco material for use in the article according to the invention is produced by a papermaking process as defined above. In such embodiments, the homogenized tobacco material is in the form of tobacco paper.

The homogenized tobacco material produced by such a process is referred to as tobacco paper. Homogenized tobacco material made by the papermaking process may be distinguished by the presence of a large number of fibers in the overall material that are visible to the naked eye or under an optical microscope, particularly when the paper is wetted with water. In contrast, homogenized tobacco material made by a casting process contains less fibers than paper and tends to dissociate into a slurry when it is wetted.

Other known processes that may be suitable for producing homogenized tobacco material are, for example, the mass reconstruction processes of the type described in US-se:Sup>A-3,894,544; and extrusion processes of the type described in, for example, GB-A-983,928. Generally, the density of the homogenized tobacco material produced by the extrusion process and the mass reconstruction process is greater than the density of the homogenized tobacco material produced by the casting process.

Preferably, the aerosol-generating substrate of the aerosol-generating article according to the invention comprises at least about 200mg of homogenized tobacco material, more preferably at least about 220mg of homogenized tobacco material, more preferably at least about 250mg of homogenized tobacco material.

An aerosol-generating article according to the invention comprises a rod comprising homogenized tobacco material in one or more rods. The strips of aerosol-generating substrate may have a length of from about 5mm to about 120 mm. For example, the strip may preferably have a length of about 10mm to about 45mm, more preferably about 10mm to 15mm, most preferably about 12 mm. In alternative embodiments, the strips preferably have a length of about 30mm to about 45mm, or about 33mm to about 41 mm. When the rod is formed from a single rod of homogenized tobacco material, the rod has the same length as the rod.

The strips of aerosol-generating substrate may have an outer diameter of from about 5mm to about 10mm, depending on their intended use. For example, in some embodiments, the strips may have an outer diameter of about 5.5mm to about 8mm, or about 6.5mm to about 8 mm. The "outer diameter" of the strip of aerosol-generating substrate corresponds to the diameter of the strip including any wrapper.

The strip of aerosol-generating substrate of the aerosol-generating article according to the invention is preferably surrounded along at least a portion of its length by one or more wrappers. The one or more packages may include paper packages or non-paper packages or both. Suitable paper packages for use in certain embodiments of the present invention are known in the art and include, but are not limited to: cigarette paper; and a filter segment wrapper. Suitable non-paper packages for use in certain embodiments of the invention are known in the art and include, but are not limited to, sheets of homogenized tobacco material.

In certain embodiments of the invention, the aerosol-generating substrate is surrounded along at least a portion of its length by a thermally conductive sheet material, for example a metal foil such as aluminium foil or metallised paper. The metal foil or metallized paper is used for the purpose of rapid thermal conduction throughout the aerosol-generating substrate. In addition, metal foil or metallized paper may be used to prevent ignition of the aerosol-generating substrate in the event that a consumer attempts to ignite it. Furthermore, during use, the metal foil or metallized paper may prevent odors generated when the outer package is heated from entering the aerosol generated by the aerosol-generating substrate. For example, this may be a problem for aerosol-generating articles having an aerosol-generating substrate that is heated from the outside during use to generate an aerosol. Alternatively or additionally, the metallized wrapper may be used to facilitate detection or identification of the aerosol-generating article when the aerosol-generating article is inserted into the aerosol-generating device during use. The metal foil or metallized paper may comprise metal particles, such as iron particles.

The one or more packages surrounding the aerosol-generating substrate preferably have a total thickness of about 0.1mm to about 0.9 mm.

The inner diameter of the strips of aerosol-generating substrate is preferably between about 3mm and about 9.5mm, more preferably between about 4mm and about 7.5mm, more preferably between about 5mm and about 7.5 mm. The "inner diameter" corresponds to the diameter of the strip of aerosol-generating substrate, excluding the thickness of the wrapper, but the wrapper is still in place when measured.

Aerosol-generating articles according to the invention also include, but are not limited to, cartridges or hookah consumables.

The aerosol-generating article 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 position the aerosol-generating substrate towards the distal end of the aerosol-generating article such that the aerosol-generating substrate may be in contact with the heating element. The tube is used to prevent the aerosol-generating substrate from being forced along the aerosol-generating article towards other downstream elements when the heating element is inserted into the aerosol-generating substrate. The tube also acts as a spacer element to separate downstream elements from the aerosol-generating substrate. The tube may be made of any material, such as cellulose acetate, polymer, cardboard or paper.

The aerosol-generating article according to the invention optionally comprises 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 from volatile compounds released from the aerosol-generating substrate passes through and is cooled by the aerosol-cooling element and is then inhaled by a user. The lower temperature allows the vapor 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 may be similar to a hollow tube immediately downstream of the aerosol-generating substrate. The spacer may be a hollow tube having an outer diameter equal to the hollow cellulose acetate tube but an inner diameter smaller or larger 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 metal foil, paper laminated with the foil, polymeric sheet preferably made of synthetic polymer, and substantially non-porous paper or paperboard. 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), polyvinyl chloride (PVC), polyethylene terephthalate (PET), polylactic acid (PLA), cellulose Acetate (CA), paper laminated with polymer sheets, and aluminum foil. Alternatively, the aerosol-cooling element may be made from woven or nonwoven filaments of a material selected from the group consisting of Polyethylene (PE), polypropylene (PP), polyvinyl chloride (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 encased within filter paper. In another preferred embodiment, the aerosol-cooling element comprises a longitudinal channel and is made of woven filaments of synthetic polymer, such as polylactic acid filaments, which are wrapped in paper.

The aerosol-generating article according to the invention may further comprise a filter or mouthpiece downstream of the aerosol-generating substrate and the hollow cellulose acetate tube, spacer or aerosol-cooling element. The filter may include one or more filter materials for removing particulate components, gaseous components, or a combination thereof. Suitable filter materials are known in the art and include, but are not limited to: fibrous filter materials such as cellulose acetate tow and paper; adsorbents such as activated alumina, zeolite, molecular sieves, and silica gel; biodegradable polymers including, for example, polylactic acid (PLA),HydrophobicSexual viscose and bioplastic; 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 segment. In one embodiment, the filter is about 7mm in length, but may have a length of between about 5mm and about 10 mm.

The aerosol-generating article according to the invention may comprise an oral 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 arranged at the downstream end of the aerosol-generating article.

The aerosol-generating article according to the invention preferably further comprises a ventilation zone arranged at a position 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.

In a preferred embodiment of the invention, the aerosol-generating article comprises an 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 an oral cavity at the downstream end of the filter. Preferably, the ventilation zone is provided at a location along the at least one hollow tube.

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

In one embodiment, the aerosol-generating article has an overall length of about 40mm to about 50mm, preferably about 45 mm. In another embodiment, the aerosol-generating article has an overall length of from about 70mm to about 90mm, preferably from about 80mm to about 85 mm. In another embodiment, the aerosol-generating article has an overall length of about 72mm to about 76mm, preferably about 74 mm.

The aerosol-generating article may have an outer diameter of from about 5mm to about 8mm, preferably from about 6mm to about 8 mm. In one embodiment, the aerosol-generating article has an outer diameter of about 7.3 mm.

The aerosol-generating article according to the invention may further comprise one or more aerosol-modifying elements. The aerosol-modifying element may provide an aerosol modifier. As used herein, the term aerosol modifier is used to describe any agent that modifies one or more characteristics or properties of an aerosol passing through a filter in use. Suitable aerosol modifiers include, but are not limited to, agents that impart a taste or aroma to the aerosol passing through the filter in use or agents that remove flavor from the aerosol passing through the filter in use.

The aerosol modifier may be one or more of moisture or a liquid flavoring agent. The water or moisture may alter the sensory experience of the user, for example by wetting the generated aerosol, which may provide a cooling effect to the aerosol and may reduce the irritation experienced by the user. The aerosol modifying element may be in the form of a flavour delivery element for delivering one or more liquid flavours. Alternatively, the liquid flavoring may be added directly to the homogenized plant material, for example by adding flavoring to the slurry or feedstock during the production of the homogenized plant material, or by spraying the liquid flavoring onto the surface of the homogenized plant material.

The one or more liquid flavourants may comprise any flavouring compound or plant extract adapted to be releasably disposed in liquid form within the flavour delivery element to enhance the taste of the aerosol generated during use of the aerosol-generating article. Liquid or solid flavoring agents may also be disposed directly in the material forming the filter, such as cellulose acetate tow. Suitable flavors or flavoring agents include, but are not limited to, menthol, peppermint, such as peppermint and spearmint, chocolate, licorice, citrus and other fruit flavors, gamma octalactone, vanillin, ethyl vanillin, breath freshener flavors, spices, such as cinnamon, methyl salicylate, linalool, eugenol, bergamot oil, geranium oil, lemon oil and tobacco flavor. Other suitable flavors may include flavor compounds selected from acids, alcohols, esters, aldehydes, ketones, pyrazines, combinations or blends thereof, and the like.

The aerosol modifier may be an adsorbent material such as activated carbon that removes certain aerosol constituents that pass through the filter and thereby alters the flavor and aroma of the aerosol.

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 homogenized tobacco material and an aerosol-modifying element. In various embodiments, the aerosol-modifying element may be disposed adjacent to or embedded in the homogenized tobacco material. Typically, the aerosol-modifying element may be located downstream of the aerosol-generating substrate, most typically within the aerosol-cooling element, within a filter of the aerosol-generating article, such as within a filter-tip segment or within a cavity between filter-tip segments. The one or more aerosol-modifying elements may be in the form of one or more of a wire, a capsule, a microcapsule, a bead, or a polymer matrix material, or a combination thereof.

If the aerosol-modifying element is in the form of A wire, as described in WO-A-2011/060961, the wire may be formed from paper such as A filter-tip segment wrapper, and the wire may be loaded with at least one aerosol-modifying agent and located within the filter body. Other materials that may be used to form the wire include cellulose acetate and cotton.

If the 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 can be released when the filter is subjected to an external force upon breakage of the capsule shell. The capsules may be located in the filter segments or in cavities between the filter segments.

If the aerosol-modifying element is in the form of A polymer matrix material, the polymer matrix material releases the flavouring when the aerosol-generating article is heated, for example when the polymer matrix is heated beyond the melting point of the polymer matrix material, as described in WO-A-2013/034488. Typically, such polymer matrix materials may be located within beads within an aerosol-generating substrate. Alternatively or additionally, the flavoring agent may be trapped within the domains of the polymer matrix material and may be released from the polymer matrix material upon compression of the polymer matrix material. Preferably, the flavoring agent is released upon compression of the polymer matrix material with a force of about 15 newtons. Such flavor modifying components may provide sustained release of liquid flavoring over a force range of at least 5 newtons, such as between 5N and 20N, as described in WO 2013/068304. Typically, such polymer matrix material may be located within beads within the filter.

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 being as described above with respect to the first aspect of the invention.

For example, the substrate as described herein may be used in A heated aerosol-generating article of the type disclosed in WO-A-2009/022232 comprising A combustible carbon-based heat source, an aerosol-generating substrate downstream of the combustible heat source, and A thermally-conductive element surrounding 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 should be understood that the substrates as described herein may also be used in heated aerosol-generating articles comprising combustible heat sources having other configurations.

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 an aerosol-generating substrate as described above.

In a preferred embodiment, an aerosol-generating substrate as described herein may be used in a heated aerosol-generating article for use in an electrically operated aerosol-generating system, wherein the aerosol-generating substrate of the heated aerosol-generating article is heated by an electrical heat source.

For example, an aerosol-generating substrate as described herein may be used in a heated aerosol-generating article of the type disclosed in EP-a-0 822 760.

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

In certain embodiments of the invention, an aerosol-generating system comprises an aerosol-generating article comprising an aerosol-generating substrate as defined above, an aerosol-former source and means for evaporating the aerosol-former, preferably a heating element as described above. The aerosol-former source may be a refillable or replaceable reservoir located on the aerosol-generating device. When the reservoir is physically separated from the aerosol-generating article, the generated vapor is directed through the aerosol-generating article. The vapor is contacted with an aerosol-generating substrate that releases volatile compounds such as nicotine and flavoring in the plant material to form an aerosol. Optionally, to assist in volatilisation 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 coordinated manner with the aerosol-former. However, in certain embodiments, the heating element for heating the aerosol-generating article is separate from the heater for heating the aerosol-forming agent.

The present invention also provides a method of producing a dried raw tobacco material for use in an aerosol-generating substrate according to the invention, as defined hereinabove, as described in detail hereinbelow. The method according to the invention comprises the following steps: providing uncooked raw tobacco leaves; drying the uncooked raw tobacco until a moisture content of between 4 wt.% and 15 wt.% is achieved; and cutting or grinding the uncooked raw tobacco leaf to produce dried raw tobacco material. According to the invention, the temperature, pressure and duration of the drying step are selected such that the dried raw tobacco material retains chlorophyll levels of at least 0.5 milligrams per gram. This means that the drying step is performed in such a way that the chlorophyll level in the tobacco leaves is preserved and the leaves remain green. The raw tobacco leaves are not subjected to any curing process.

Preferably, the drying step of the method according to the invention is completed within 5 days after harvesting of the uncooked raw tobacco leaves, more preferably within 4 days after harvesting, more preferably within 3 days after harvesting, most preferably within 2 days after 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 the tobacco material is harvested. Thus, the dried raw tobacco material is produced in a relatively short time after harvesting the tobacco, so that any influence on the chemical composition of the tobacco due to storage of the tobacco can be minimized.

The method of the present invention provides a method of rapidly and efficiently processing raw tobacco leaves into a dried raw tobacco material suitable for use in an aerosol-generating substrate for an aerosol-generating article as described above. This in turn enables a more efficient generation of aerosol-generating substrate both from a time and cost perspective. The method of the present invention is applicable to all tobacco types. Advantageously, the method of the invention can be carried out on the whole tobacco leaf without stem removal, if desired. Alternatively, the method according to the invention may be carried out with leaves of green tobacco leaves which have not been cured. In this case, the leaves are stemmed and the stems are separately processed before the drying step. If desired, the stems may be recombined with tobacco lamina to provide a dried raw tobacco material for use in forming an aerosol-generating substrate.

The drying of the raw tobacco leaves is carried out under specifically selected temperature and pressure conditions such that curing does not occur and the tobacco leaves remain green. As described above, the use of raw tobacco in an aerosol-generating substrate has several benefits based on the reduction in levels of certain undesirable constituent components present in the cured She Xiangbi raw tobacco.

There are several different methods that can be used to rapidly dry the uncooked tobacco leaf to reduce the moisture content to between about 4 wt.% and about 15 wt.%, more preferably between about 10 wt.% and about 13 wt.%, while retaining chlorophyll levels in the leaf as high as possible. Depending on the method selected, the temperature, pressure and duration are specifically adjusted to provide the desired result.

In certain embodiments, the drying step is performed by heating the uncooked raw tobacco leaf to reduce the moisture content of the leaf as quickly as possible. Heating of the tobacco leaves may be carried out using any suitable equipment known to the skilled person, such as an oven or a dryer. Preferably, the heating of the tobacco leaves is carried out in a tray dryer. One example of a suitable apparatus for performing the drying step is a tray dryer available from Wolvering Proctor & Schwartz ltd.

In tray dryers, the tobacco leaves are typically suspended within a heated chamber, which minimizes contact between the leaves and maximizes the exposed surface area of the leaves to facilitate drying. During the drying step, heated air or steam is circulated through the chamber at a desired temperature. It has been found that using a tray dryer to heat tobacco leaves advantageously provides uniform heating of the leaves, minimizing hot spots within the dryer. This optimizes the uniformity of drying of the leaves. It has also been found that the use of tray dryers is most effective for drying the midvein of tobacco leaves, which is generally slower than the leaf portion of the leaves.

Preferably, in such embodiments, the drying step is performed 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 performed at a temperature of at least about 75 degrees celsius, more preferably at least about 85 degrees celsius, more preferably at least about 100 degrees celsius. For example, the drying step may be performed at a temperature between about 75 degrees celsius and about 120 degrees celsius, or between about 75 degrees celsius and about 110 degrees celsius. This temperature level is chosen to provide efficient drying while retaining relatively high chlorophyll levels and avoiding damage to the leaves during the heating process.

In a particularly preferred embodiment, the drying step is performed in a tray dryer at a temperature between 75 degrees celsius and 110 degrees celsius.

The duration of the heating step will depend on the moisture level of the uncooked tobacco leaves prior to drying as well as the specific temperature and exact heating conditions selected for the heating step. 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, most preferably no more than 1 hour.

In a particularly preferred example, the uncooked tobacco leaf is heated at a temperature of 75 degrees celsius for no more than 7 hours to achieve the desired reduction in moisture content. In an alternative preferred embodiment, the uncooked tobacco leaf is heated at a temperature of 110 degrees celsius for no more than 4 hours to achieve the desired reduction in moisture content.

Preferably, the heating step is carried out under aeration conditions, wherein air or inert gas is continuously flowed through the tobacco leaves during heating. This may advantageously reduce the drying time required.

Preferably, the heating step is performed without agitating the tobacco leaves, for example in a rotating drum. This will avoid potential damage to the tobacco during heating.

The heating step may be performed on the entire whole tobacco leaf. Alternatively, the tobacco leaves may be de-stemmed prior to the heating step such that the tobacco lamina and stem are dried separately from each other.

In certain embodiments, the heating step includes heating the entire tobacco leaf, separating the tobacco lamina from the tobacco stem and removing the tobacco lamina from the dryer while drying, and then heating the remaining tobacco obstruction until dry. This allows both the tobacco lamina and midrib to be effectively dried without overdrying the lamina.

In certain embodiments wherein the drying step is performed by heating, the method according to the present invention may further comprise a second heating step, which is performed after the first heating step and at a lower temperature. For example, the method may further include a second heating step during which the uncooked raw tobacco leaf is heated at a temperature of less than about 75 degrees celsius or less than about 50 degrees celsius. In case the uncooked tobacco leaves remain intact during drying, it may be advantageous to include a second heating step, so that a complete drying of the tobacco stems (midribs) may be achieved.

As an alternative to heating, the drying step of the method of the invention may be carried out by lyophilization. Lyophilization, also known as freeze-drying, is a dehydration process that involves freezing a product (in this case tobacco leaf) and then gradually reducing the pressure and increasing the temperature to sublimate the frozen water and thereby remove it from the product.

Preferably, during drying of the uncooked raw tobacco leaves by lyophilization, the tobacco leaves are initially frozen to a temperature below-60 degrees celsius, more preferably below-75 degrees celsius. For example, the tobacco leaves may be frozen to a temperature of about-80 degrees celsius. Preferably, the freezing of the tobacco leaves is performed as soon as possible after the harvesting of the leaves.

The remaining steps of the lyophilization process are performed in a suitable lyophilization chamber. In the first lyophilization stage, the uncooked tobacco leaves are preferably maintained in a frozen state at atmospheric pressure. Preferably, the duration of the first lyophilization stage is no more than about 60 minutes, more preferably no more than about 30 minutes.

In the second lyophilization stage, the vacuum pressure and temperature within the chamber are gradually adjusted to reach the target pressure (below atmospheric pressure) and the target temperature (below room temperature). The target pressure is preferably about 0.1mBar. The target temperature is preferably about 15 degrees celsius. Preferably, the duration of the second lyophilization step is between about 24 hours and about 60 hours.

In the third and final lyophilization step, the temperature is raised to about room temperature (22 degrees celsius) under full vacuum. Preferably, the duration of the third lyophilization step is between about 24 hours and about 60 hours.

As yet another alternative, the drying step of the method of the present invention may be performed using microwave heating. For example, uncooked raw tobacco leaves can be dried in a microwave tunnel dryer. The use of microwave heating to dry uncooked raw tobacco leaves advantageously enables very rapid removal of leaf moisture, as microwaves can rapidly raise the temperature of the leaves, causing evaporation of water molecules within the tobacco.

Preferably, during the drying step, the uncooked raw 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 may be adjusted to provide a desired moisture level of the tobacco leaf.

Suitable microwave tunnel dryers are commercially available, for example, from Jinan Himax machinery co.

After the uncooked raw tobacco leaf has been dried to a desired moisture content of between 4 wt.% and 15 wt.%, the dried tobacco leaf is processed to form a dried raw tobacco material of a desired size. The uncooked raw tobacco leaf is preferably cut or ground using known techniques for producing tobacco particles.

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

fig. 1 shows a first embodiment of a matrix of an aerosol-generating article as described herein;

fig. 2 shows an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device comprising an electrical heating element;

fig. 3 shows an aerosol-generating system comprising an aerosol-generating article and an aerosol-generating device comprising a combustible heating element;

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

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

Figure 4b illustrates an aerosol-modifying element in the form of a wire within a filter segment.

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

fig. 5 is a cross-sectional view of a rod of aerosol-generating substrate 1020 further comprising an elongated susceptor element.

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

When assembled, the article 1000 has a length of about 45 millimeters and an outer diameter of about 7.2 millimeters and an inner diameter of about 6.9 millimeters.

Aerosol-generating substrate 1020 comprises a rod formed from a sheet of homogenized tobacco material comprising a blend of dried raw tobacco material and cooked tobacco particles.

A number of examples of suitable homogenized tobacco materials for forming aerosol-generating substrate 1020 are shown in table 1 below (see samples a and B). The sheets are gathered, crimped and wrapped in filter paper (not shown) to form a rod. The sheet contains additives including glycerin as an aerosol former.

The aerosol-generating article 1000 as shown in fig. 1 is designed to be engaged with an aerosol-generating device in order to be consumed. Such an aerosol-generating device comprises means for heating the aerosol-generating substrate 1020 to a sufficient temperature to form an aerosol. In general, the aerosol-generating device may comprise a heating element surrounding the aerosol-generating article 1000 adjacent to the aerosol-generating substrate 1020, or a heating element inserted into the aerosol-generating substrate 1020.

Once engaged with the 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 aerosols. The aerosol is drawn through the filter 1050 and into the user's mouth.

Fig. 2 shows a portion of an electrically operated aerosol-generating system 2000 that utilizes a heating blade 2100 to heat an aerosol-generating substrate 1020 of an aerosol-generating article 1000. The heating blade is mounted within the aerosol-product receiving chamber of the electrically operated aerosol-generating device 2010. The aerosol-generating device defines a plurality of air holes 2050 to allow air to flow to the aerosol-generating article 1000. The air flow is indicated by the arrows on fig. 2. The aerosol-generating device comprises a power supply and electronics, which are not shown in fig. 2. The aerosol-generating article 1000 of fig. 2 is as described with respect to fig. 1.

In an alternative configuration shown in fig. 3, the aerosol-generating system is shown with a combustible heating element. While the article 1000 of fig. 1 is intended to be consumed in conjunction with an aerosol-generating device, the article 1001 of fig. 3 includes a combustible heat source 1080 that can 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 proximate to the aerosol-generating substrate at the distal end 13 of the strip 11. Elements that are substantially identical to elements in fig. 1 are given the same reference numerals.

Fig. 4 is a cross-sectional view of a filter 1050 that also includes an aerosol-modifying element. In fig. 4a, filter 1050 further comprises an aerosol-modifying element in the form of a spherical capsule or bead 605.

In the embodiment of fig. 4a, capsules or beads 605 are embedded in the filter segment 601 and 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 flavoring agent. Liquid flavouring is used to flavour an aerosol during use of an aerosol-generating article provided with a filter. When the filter is subjected to an external force, such as by a consumer, the capsule 605 releases at least a portion of the liquid flavoring. In the embodiment shown, the capsule is generally spherical with a substantially continuous shell containing liquid flavoring.

In the embodiment of fig. 4b, the filter segment 601 comprises a rod of filter material 603 and a central flavor bearing line 607 extending axially through the rod of filter material 603 parallel to the longitudinal axis of the filter 1050. The length of the central flavour carrier line 607 is substantially the same as the length of the filter material rod 603 such that the ends of the central flavour carrier line 607 are visible at the ends of the filter segments 601. In fig. 4b, the filter material 603 is cellulose acetate tow. The central flavour carrier line 607 is formed of a twisted filter segment wrapper and is loaded with aerosol modifiers.

In the embodiment of fig. 4c, the filter segment 601 comprises more than one rod 603, 603' of filter material. Preferably, the filter material rods 603, 603' are formed of cellulose acetate such that they are capable of filtering aerosols provided by the aerosol-generating article. The wrapper 609 wraps around and connects the filter segments 603, 603'. Within the cavity 611 is a capsule 605 comprising an outer shell and an inner core, and the inner core contains a liquid flavoring. The capsule is otherwise similar to the embodiment of fig. 4 a.

Fig. 5 is a cross-sectional view of an aerosol-generating substrate 1020 further comprising an elongated susceptor strip 705. Aerosol-generating substrate 1020 comprises rod 703 formed from a sheet of homogenized tobacco material comprising a blend of dried raw tobacco material and cooked tobacco particles. An elongated susceptor strip 705 is embedded within rod 703 and extends in the longitudinal direction between the upstream and downstream ends of rod 703. During use, the elongate susceptor strip 705 heats the homogenized tobacco material by means of inductive heating as described above.

Examples

As described above with reference to the figures, different samples of homogenized tobacco material for aerosol-generating substrate according to the invention may be prepared from aqueous slurries having the composition shown in table 1. Samples a through D according to the present invention contained dried raw tobacco material (alone or in combination with cooked tobacco particles). Sample E contained only cooked tobacco particles and was included for comparison purposes only.

Sample a was formed with a combination of CMC binder and cellulose fibers according to a second preferred embodiment of the invention. Sample a was prepared from an aqueous slurry containing 72.97kg water per 100kg slurry, the remainder being the relative amounts of the components shown in table 1.

Samples B to D were formed with guar gum binders according to the first preferred embodiment of the invention. Samples B through D were prepared from aqueous slurries containing 78-79kg water per 100kg slurry.

In the following table,% DWB refers to "dry weight basis", in which case the weight percentages are calculated relative to the dry weight of the homogenized plant material. The tobacco particles have been ground to an average particle size of 100 microns by triple impact milling.

The dried raw tobacco material is derived from burley tobacco leaf and has been flash dried using the heating method according to the invention as described above. The cooked tobacco particles can be derived from one or more types of cooked tobacco as desired.

The slurry was cast onto a glass plate using a casting bar (0.6 mm), 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 the slurries

For each of samples a to E of homogenized tobacco material, a rod may be produced from a single continuous sheet of homogenized tobacco material, said sheets each having a width of 100mm to 130 mm. Each sheet preferably has a thickness of about 220 microns and a thickness of about 189g/m ² Gram weight per square meter. The cut width of each sheet was about 120mm. The sheet was crimped to a height of 165 microns to 170 microns and rolled into a rod having a length of about 12mm and a diameter of about 7mm, surrounded by a wrapper. The total weight of each bar was about 250mg.

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

Comparative example 1 burley tobacco

To demonstrate the effect of the curing process on the chemical composition of burley tobacco, three burley tobacco samples were measured: the levels of certain tobacco constituents in the uncooked raw burley tobacco leaves, the burley tobacco leaves dried for 5 days, and the burley tobacco leaves dried sufficiently (50 days). Each sample began with the same uncooked raw burley tobacco leaf and thus the change in the level of each constituent was considered to be a direct result of the curing process. The results are shown in table 2 below:

table 2: chemical composition of unripe and ripe burley tobacco leaves (dry weight basis)

As shown in the table, the chlorophyll level was significantly reduced to very low levels after only 5 days of maturation. This demonstrates that the presence of chlorophyll levels above 0.5mg/g is a good indicator of green tobacco leaves that have not been cured.

It was found that the levels of asparagine, ammonia, total free amino acids and NNN increased significantly as a result of the maturation process, so that in each case the levels of these constituents in the mature leaves were several times higher than in the uncooked leaves. As shown below, the reduced levels of these constituents in the uncooked raw tobacco leaves provide a reduction in the associated undesirable constituents in the aerosol generated from the homogenized tobacco material comprising the uncooked raw tobacco.

The sugar level in burley tobacco was found to vary from 6.87 wt.% of the uncooked raw tobacco to 6.47 wt.% of the 5 day-cured tobacco and 1.7 wt.% of the fully cured tobacco, measured on a dry weight basis.

For each of the burley tobacco samples, a homogenized tobacco material was formed using the casting process described above and having the composition shown in table 3 below:

table 3: homogenized tobacco material composition:

component (A)	(dry weight basis)
		Burley tobacco particles	37.5
Virginia cured tobacco particles	37.5
		Glycerol	18
Guar gum	3
		Cellulose fiber	4

Each sample of homogenized tobacco material was gathered to form a rod of aerosol-generating substrate weighing 250mg, which was then incorporated into an aerosol-generating article as described in the examples above. For each of these aerosol-generating articles, a mainstream aerosol was generated and collected according to test method a described above. For each sample, aerosols were captured and analyzed.

As described in detail above, according to test method a, commercially available can be usedThe heat-not burn device tobacco heating system 2.2 holder (THS 2.2 holder) (from Philip Morris Products SA) was tested for aerosol-generating articles. The aerosol-generating article was heated in accordance with the Health Canada machine smoking protocol for more than 30 puffs, with a puff volume of 55ml, a puff duration of 2 seconds and a puff interval of 30 seconds (as described in ISO/TR 19478-1:2014). Aerosols generated during the smoking test were collected on a Cambridge filter pad and extracted with a liquid solvent.

Table 4 below shows the levels of certain tobacco-derived aerosol constituents in aerosols generated from three samples containing uncooked raw burley tobacco particles, burley tobacco particles cooked for 5 days, and burley tobacco particles fully cooked. Based on 250mg strips of aerosol-generating substrate, express the amount of each aerosol constituent per article:

Table 4: composition of aerosol-amount of tobacco-derived aerosol constituents

The results shown in table 4 demonstrate the effect of including a proportion of dried raw tobacco material in the homogenized tobacco material forming the aerosol-generating substrate on the level of aerosol constituents. Notably, the level of acrylamide in the aerosol generated from the samples comprising dried raw tobacco material was significantly lower than the other two samples using only cooked tobacco particles. This is believed to be due to the reduced level of asparagine in the uncooked tobacco leaf, as described above. The levels of ammonia, hydrogen sulfide and methyl mercaptan in the aerosol generated from the samples comprising dried raw tobacco material were also significantly lower than the other two samples using only cooked tobacco particles.

The results demonstrate that advantageously, the curing process does not substantially affect the nicotine released from the tobacco material into the aerosol, so the use of dried raw tobacco material instead of cured tobacco particles does not affect the nicotine content of the aerosol.

Overall, the aerosols generated from the samples containing dried raw tobacco material thus exhibit improved levels of certain undesirable compounds while maintaining consistent nicotine delivery.

Similar reductions in these aerosol constituents are expected for other tobacco types, such as virginia tobacco.

Claims

1. An aerosol-generating substrate for a heated aerosol-generating article, the aerosol-generating substrate comprising a homogenized tobacco material comprising dried raw tobacco material, an aerosol-former and a binder, wherein the homogenized tobacco material has an aerosol-former content of between 5 and 55 weight percent on a dry weight basis.

2. An aerosol-generating substrate according to claim 1, wherein the homogenized 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 substrate according to claim 1 or 2, wherein the homogenized tobacco material comprises at least 10 wt% of the dried raw tobacco material on a dry weight basis.

4. An aerosol-generating substrate according to any preceding claim, wherein the homogenized tobacco material further comprises at least 1 wt% cooked tobacco material on a dry weight basis.

5. An aerosol-generating substrate according to claim 4, wherein the ratio of dried raw tobacco material to cooked tobacco material in the homogenized tobacco material is no more than 1:1.

6. An aerosol-generating substrate according to any preceding claim, wherein the homogenized tobacco material comprises between 1 and 10 wt% binder on a dry weight basis.

7. An aerosol-generating article according to any preceding claim, wherein the homogenized tobacco material is in the form of cast leaves.

8. An aerosol-generating article comprising a strip of aerosol-generating substrate according to any preceding claim.

9. An aerosol-generating system, the aerosol-generating system comprising:

an aerosol-generating device comprising a heating element; and

an aerosol-generating article according to claim 8.

10. Use of a dried raw tobacco material in forming an aerosol-generating substrate for an aerosol-generating article, the aerosol-generating substrate comprising a homogenized tobacco material comprising dried raw tobacco material, an aerosol-former and a binder, wherein the homogenized tobacco material has an aerosol-former content of between 5 and 55 wt% on a dry weight basis.

11. A method of producing a dried raw tobacco material for use in an aerosol-generating substrate according to any of claims 1 to 7, the method comprising:

Providing uncooked raw tobacco leaves;

drying the uncooked raw tobacco until a moisture content of between 4 wt.% and 15 wt.% is achieved; and

cutting or grinding the uncooked raw tobacco leaves to produce dried raw tobacco material,

wherein the drying step is performed by heating the uncooked raw tobacco leaf at a temperature between 75 degrees celsius and 120 degrees celsius for no more than 7 hours such that the dried raw tobacco material retains a chlorophyll level of at least 0.5 milligrams per gram.

12. The method of claim 11, wherein the uncooked raw tobacco leaf is heated for no more than 4 hours.

13. The method of claim 11 or 12, wherein the drying step is performed in a tray dryer.

14. A method of producing homogenized tobacco material for use in an aerosol-forming substrate according to any of claims 1-7, the method comprising the steps of:

combining the dried raw tobacco material, an aerosol former, a binder, and water to form a slurry;

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

drying the sheet of homogenized tobacco material, wherein the sheet of homogenized tobacco material has an aerosol former content of between 5 weight percent and 55 weight percent on a dry weight basis.