AEROSOL-GENERATING PRODUCT CONTAINING A SUBSTRATE WITH HOMOGENIZED PLANT MATERIAL

Abstract

An aerosol-generating article (1)(2) comprises an aerosol-generating substrate (12)(212), the aerosol-generating substrate (12)(212) including a homogenised plant material, the homogenised plant material comprising: at least 20 percent by weight of non-tobacco plant particles, on a dry weight basis; between 1 percent by weight and 3.5 percent by weight of exogenous nicotine, on a dry weight basis; at least 1 percent by weight of an acidic pH modifier, on a dry weight basis; and at least 10 percent by weight of aerosol former, on a dry weight basis.

Description

[0001] AEROSOL-GENERATING ARTICLE COMPRISING A SUBSTRATE WITH HOMOGENISED PLANT MATERIAL

[0002] The present invention relates to an aerosol-generating article comprising an aerosolgenerating substrate including homogenised plant material comprising non-tobacco plant particles. The present invention further relates to an aerosol-generating system comprising a heating element for heating such aerosol-generating articles and to a method of making an aerosol-generating substrate for such aerosol-generating articles.

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

[0004] Some aerosol-generating articles comprise a flavourant that is delivered to the consumer during use of the article to provide a different sensory experience to the consumer, for example to enhance the flavour of aerosol. A flavourant can be used to deliver a gustatory sensation (taste), an olfactory sensation (smell), or both a gustatory and an olfactory sensation to the user inhaling the aerosol. It is known to provide heated aerosol-generating articles that include flavourants.

[0005] There are difficulties involved in replicating the sensory experience provided by conventional combustible cigarettes with aerosol-generating articles in which the aerosolgenerating substrate is heated rather than combusted. This is partially due to the lower temperatures reached during the heating of such aerosol-generating articles, leading to a different profile of volatile compounds being released. It has also been found to be difficult to generate a sufficient level of aerosol from substrates containing a relatively high level of non-tobacco plant materials. With such materials, it can also be challenging to provide an acceptable balance of flavour and delivery of nicotine or other active compounds from the substrate.

[0006] It would be desirable to provide a novel aerosol-generating substrate for a heated aerosolgenerating article providing an improved flavour delivery to the consumer whilst also optimising nicotine delivery. It would be further desirable to provide a novel sensory experience to the consumer. It would also be desirable to provide such an aerosol-generating substrate that can be readily incorporated into an aerosol-generating article and which can be manufactured using existing high-speed methods and apparatus.

[0007] The present disclosure relates to an aerosol-generating article. The aerosol-generating article may comprise an aerosol-generating substrate. The aerosol-generating substrate may include a homogenised plant material. The homogenised plant material may comprise at least 20 percent by weight of non-tobacco plant particles, on a dry weight basis. The homogenised plant material may further comprise between 1 percent by weight and 3.5 percent by weight of exogenous nicotine, on a dry weight basis. The homogenised plant material may further comprise at least 1 percent by weight of an acidic pH modifier, on a dry weight basis. The homogenised plant material may further comprise at least 10 percent by weight of aerosol former, on a dry weight basis.

[0008] Further, the present disclosure relates to an aerosol-generating system. The aerosolgenerating system may comprise an aerosol-generating article as described above. The aerosolgenerating system may further comprise an electrically operated aerosol-generating device comprising a heater element configured to heat the aerosol-generating substrate of the aerosolgenerating article.

[0009] Further, the present disclosure relates to a method of making an aerosol-generating substrate for use in the aerosol-generating article as described above. The method may comprise the step of forming a slurry comprising non-tobacco plant flavour particles, exogenous nicotine, aerosol former, an acidic pH modifier and water. The amount of acid in the slurry may be adapted such that the pH of the slurry is less than 5.5. The method may further comprise the step of casting the slurry in the form of a sheet. The method may further comprise the step of drying the sheet at between 80 and 160 degrees Celsius.

[0010] According to the present invention there is provided an aerosol-generating article comprising an aerosol-generating substrate, the aerosol-generating substrate including a homogenised plant material, the homogenised plant material comprising: at least 20 percent by weight of non-tobacco plant particles, on a dry weight basis; between 1 percent by weight and 3.5 percent by weight of exogenous nicotine, on a dry weight basis; at least 1 percent by weight of an acidic pH modifier, on a dry weight basis; and at least 10 percent by weight of aerosol former, on a dry weight basis.

[0011] Further, according to the present invention there is provided an aerosol-generating system. The aerosol-generating system comprises an aerosol-generating article according to the invention, as described above, and an electrically operated aerosol-generating device comprising a heater element configured to heat the aerosol-generating substrate of the aerosol-generating article.

[0012] Further, according to the present invention there is provided a method of making an aerosolgenerating substrate for use in the aerosol-generating article according to the invention, as described above, the method comprising the steps of: forming a slurry comprising non-tobacco plant flavour particles, exogenous nicotine, aerosol former, acidic pH modifier and water, wherein the amount of acid in the slurry is adapted such that the pH of the slurry is less than 5.5; casting the slurry in the form of a sheet; and drying the sheet at between 80 and 160 degrees Celsius. The inventors of the present invention have found that through the combination of nontobacco plant particles and exogenous nicotine in the homogenised plant material of the aerosolgenerating substrate, it is advantageously possible to produce an aerosol which provides a novel sensory experience whilst also providing a desirable level of nicotine delivery to the consumer. Advantageously, the aerosol-generating substrate can provide a puff profile of nicotine delivery that is similar to the puff profile provided by a tobacco-based aerosol-generating substrate.

[0013] The inventors have also found that this combination of non-tobacco plant particles with exogenous nicotine enables the aerosol-generating substrates to advantageously be formed with a reduced (or zero) level of tobacco particles, which means that the levels of undesirable tobacco compounds in the aerosol are reduced whilst still maintaining an acceptable delivery of nicotine.

[0014] The inclusion of an acidic pH modifier in the aerosol-generating substrate of aerosolgenerating articles according to the present invention in order to decrease the pH of the aerosolgenerating substrate has been found to advantageously improve the efficiency of nicotine delivery from the aerosol-generating substrate. Some types of non-tobacco plant materials produce a slurry with a relatively high pH level. It has been found that this higher pH can lead to a higher volatility of the exogenous nicotine in the slurry, so that a greater proportion of the nicotine is lost during drying of the cast sheet. The inclusion of an acidic pH modifier can advantageously reduce the pH to a sufficient level that the nicotine losses during production are minimised. In this way, the nicotine can be efficiently retained within the aerosol-generating substrate and delivered to the consumer upon heating.

[0015] Advantageously, aerosol-generating articles according to the present invention may be manufactured with the same external dimensions as known aerosol-generating articles. Therefore, users of aerosol-generating articles according to the invention can use them with existing aerosol-generating devices. A further advantage of aerosol-generating articles according to the invention is that since the dimensions of the articles are substantially unchanged, they can be packaged in existing packaging solutions. Aerosol-generating articles according to the present invention can be manufactured efficiently and at high speed using existing manufacturing techniques and machinery.

[0016] As used herein, the term “aerosol-generating article” refers to an article wherein an aerosolgenerating substrate is heated to produce and deliver an inhalable aerosol to a consumer.

[0017] As used herein, the term “aerosol-generating substrate” refers to a substrate capable of releasing upon heating volatile compounds, which can form an aerosol. A conventional cigarette is lit when a user applies a flame to one end of the cigarette and draws air through the other end. The localised heat provided by the flame and the oxygen in the air drawn through the cigarette causes the end of the cigarette to ignite, and the resulting combustion generates an inhalable smoke. By contrast, in heated aerosol-generating articles, an aerosol is generated by heating an aerosol-generating substrate, such as tobacco. Known heated aerosol-generating articles include, for example, electrically heated aerosol-generating articles and aerosol-generating articles in which an aerosol is generated by the transfer of heat from a combustible fuel element or heat source to a physically separate aerosol-generating substrate.

[0018] As used herein with reference to the invention, the term “homogenised plant material” denotes a material formed by agglomerating particulate plant material.

[0019] As used herein, “aerosol-generating device” refers to a device that interacts with an aerosolgenerating substrate to generate an aerosol. Preferably, the aerosol-generating device is a device that interacts with an aerosol-generating substrate to generate an inhalable aerosol that is directly inhalable into a user’s lungs thorough the user's mouth.

[0020] As used herein, “aerosol-generating system” typically refers to the combination of an aerosol-generating device with an aerosol-generating substrate, preferably where the aerosolgenerating substrate is comprised in an aerosol-generating article. In an aerosol-generating system, the aerosol-generating substrate and the aerosol-generating device cooperate to generate an aerosol.

[0021] As used herein with reference to the present disclosure, the term “aerosol” is used to describe a dispersion of solid particles, or liquid droplets, or a combination of solid particles and liquid droplets, in a gas. The aerosol may be visible or invisible. The aerosol may include vapours of substances that are ordinarily liquid or solid at room temperature as well as solid particles, or liquid droplets, or a combination of solid particles and liquid droplets.

[0022] As used herein, “length” refers to the maximum dimension of a feature in a longitudinal direction of the feature. The term “length” denotes the dimension of a component of the aerosolgenerating system in the longitudinal direction, from the component’s furthest upstream point to the component’s furthest downstream point. For example, it may be used to denote the dimension of aerosol-generating substrate or of any elongate tubular elements in the longitudinal direction.

[0023] As used herein, the term “plug” denotes a generally cylindrical element having a substantially polygonal, circular, oval or elliptical cross-section. As used herein, the term “rod” refers to a generally cylindrical element of substantially polygonal cross-section and preferably of circular, oval or elliptical cross-section. A rod may have a length greater than or equal to the length of a plug. Typically, a rod has a length that is greater than the length of a plug. A rod may comprise one or more plugs, preferably aligned longitudinally.

[0024] As used herein, “upstream” and “downstream” describe the relative positions of elements, or portions of elements, of the aerosol-generating system in relation to the direction in which the aerosol is transported through the aerosol-generating article during use. During use, air is drawn through the aerosol-generating article in the longitudinal direction.

[0025] As used herein, “dry weight” refers to the weight of a particular non-water component relative to the sum of the weights of all non-water components in a mixture, expressed as a percentage. The composition of aqueous mixtures may be referred to by “percentage dry weight.” This refers to the weight of the non-water components relative to the weight of the entire aqueous mixture, expressed as a percentage. As used throughout the present disclosure, the term “hollow tubular element” denotes a generally elongate element defining a lumen or airflow passage along a longitudinal axis thereof.

[0026] As defined above, the aerosol-generating substrate of aerosol-generating articles according to the present invention is formed of a homogenised plant material comprising at least 20 percent by weight of non-tobacco plant particles.

[0027] The homogenised plant material may comprise a single non-tobacco plant material, or a combination of two or more different non-tobacco plant materials. The non-tobacco plant particles may be particles formed from leaves, flower buds, seeds or any other suitable plant material.

[0028] In some preferred embodiments, the non-tobacco plant particles are selected from one or more of: ginger particles, eucalyptus particles, clove particles, star anise particles, chamomile particles, verbena particles, tea particles and combinations thereof.

[0029] In particularly preferred embodiments, the non-tobacco plant particles are selected from one or more of: ginger particles, eucalyptus particles, clove particles, star anise particles, and combinations thereof.

[0030] In particularly preferred embodiments, the non-tobacco plant particles comprise ginger particles.

[0031] As used herein, the term “ginger particles” encompasses particles derived from the dried root of plants of the genus Zingiber, preferably particles derived from Zingiber officinale Rose. (Zingiberaceae).

[0032] As used herein, the term “eucalyptus particles” encompasses particles derived from plants of the genus Eucalyptus, preferably particles derived from one or more of E. globulus, E. radiata, E. citriodora and E. smithii, most preferably particles derived from E. globulus, such as ground or powdered eucalyptus leaf lamina, and ground or powdered eucalyptus leaf stems.

[0033] As used herein, “clove particles” encompasses particles derived from buds and stems of Syzygium aromaticum, a tree in the family Myrtaceae.

[0034] As used herein, the term “star anise particles” encompasses particles derived from the dried fruits of plants of the genus lllicium, preferably particles derived from lllicium verum Hooker fil. (Illiciaceae).

[0035] As used herein, “chamomile particles” encompasses particles derived from the flowers of chamomile. The flowers of German chamomile, Matricaria chamomilla L, are preferably used.

[0036] As used herein, “verbena particles” encompasses particles derived from dried leaves of the plants of the genus Verbena, preferably particles derived from dried leaves of Verbena officinalis. Verbena is also commonly known as vervaine or vervain.

[0037] As used herein, “tea” particles encompasses particles derived from dried leaves of the plants of the species Camellia sinensis.

[0038] The total content of non-tobacco plant particles in the homogenised plant material is at least 20 percent by weight on a dry weight basis. Preferably, the total content of non-tobacco plant particles in the homogenised plant material is at least 25 percent by weight on a dry weight basis. More preferably, the total content of non-tobacco plant particles in the homogenised plant material is at least 30 percent by weight on a dry weight basis. More preferably, the total content of nontobacco plant particles in the homogenised plant material is at least 35 percent by weight on a dry weight basis.

[0039] The total content of non-tobacco plant particles in the homogenised plant material is preferably less than or equal to 75 percent by weight on a dry weight basis. More preferably, the total content of non-tobacco plant particles in the homogenised plant material is less than or equal to 70 percent by weight on a dry weight basis. More preferably, the total content of non-tobacco plant particles in the homogenised plant material is less than or equal to 65 percent by weight on a dry weight basis. More preferably, the total content of non-tobacco plant particles in the homogenised plant material is less than or equal to 65 percent by weight on a dry weight basis.

[0040] For example, the total content of non-tobacco plant particles in the homogenised plant material may be between 20 percent and 75 percent by weight, or between 25 percent and 70 percent by weight, or between 30 percent and 65 percent by weight, or between 35 percent and 60 percent by weight, on a dry weight basis.

[0041] In certain embodiments, for example embodiments in which the homogenised plant material comprises one or more cellulose based strengthening agents, as described below, the total content of non-tobacco plant particles in the homogenised plant material may be less than or equal to 45 percent by weight on a dry weight basis, or less than or equal to 40 percent by weight on a dry weight basis. For example, in such embodiments, the total content of non-tobacco particles in the homogenised plant material may be between 20 percent by weight and 45 percent by weight, or between 25 percent by weight and 45 percent by weight, or between 20 percent by weight and 40 percent by weight, or between 25 percent by weight and 40 percent by weight, on a dry weight basis.

[0042] The inventors have found that providing a homogenised plant material having a content of non-tobacco particles falling within the above ranges can help with the generation of an aerosol with a good balance of flavour to the user. In particular, the aerosol generated from such a rod of aerosol-generating substrate advantageously has good flavour from the non-tobacco particles whilst still providing acceptable delivery of nicotine.

[0043] The particle size of the non-tobacco plant particles may be adapted depending on the desired properties of the homogenised plant material.

[0044] Particle sizes herein are stated as D-values, whereby the D-value refers to the percentage of particles by number with a diameter of less than or equal to the given D-value. For instance, in a D90 particle size distribution, 90 percent of the particles by number are of a diameter less than or equal to the given D90 value, and 10% percent of the particles by number are of a diameter measuring greater than the given D90 value. The particle size distribution may be determined by laser diffraction. For example, the particle size distribution may be determined by laser diffraction using a Malvern Mastersizer 3000 laser diffraction particle size analyser in accordance with the manufacturer’s instructions.

[0045] The non-tobacco plant particles preferably have a D90 value of at least 50 microns, more preferably at least 100 microns, more preferably at least 150 microns, more preferably at least 200 microns.

[0046] Preferably, the non-tobacco plant particles have a D90 values of less than or equal to 325 microns, more preferably less than or equal to 300 microns, more preferably less than or equal to 275 microns, more preferably less than or equal to 250 microns.

[0047] For example, the non-tobacco plant particles may have a D90 values of between 50 microns and 325 microns, or between 100 microns and 300 microns, or between 150 microns and 275 microns, or between 200 microns and 250 microns.

[0048] The diameter of 100 percent of the non-tobacco plant particles may be less than or equal to 400 microns, more preferably less than or equal to 350 microns.

[0049] The particle size range of the non-tobacco plant particles enables these non-tobacco plant particles to be used in existing cast leaf processes, in place of tobacco particles. Without wishing to be bound by theory, the particle size range of the non-tobacco plant particles may in some cases reduce or prevent loss of volatile flavour essential oils from the non-tobacco plant particles, as excessive grinding of the particles may cause volatile flavour essential oils to separate from the particles and to evaporate from the relatively large surface area of the relatively small particles.

[0050] The homogenised plant material may optionally comprise tobacco particles in addition to the non-tobacco plant particles. However, preferably the level of tobacco particles is relatively low. Preferably, the homogenised plant material comprises less than 5 percent by weight of tobacco particles, on a dry weight basis. More preferably, the homogenised plant material comprises less than 2 percent by weight of tobacco particles, on a dry weight basis. More preferably, the homogenised plant material comprises less than 1 percent by weight of tobacco particles, on a dry weight basis.

[0051] In some preferred embodiments of the present invention, the homogenised plant material is substantially free from tobacco, or free from tobacco.

[0052] The homogenised plant material further comprises between 1 percent by weight and 3.5 percent by weight of exogenous nicotine.

[0053] As used herein with reference to the invention, the term “nicotine” is used to describe nicotine, a nicotine base or a nicotine salt. In embodiments in which the homogenised plant material comprises a nicotine base or a nicotine salt, the amounts of nicotine recited herein are the amount of free base nicotine or amount of protonated nicotine, respectively.

[0054] As used herein with reference to the invention, the term “exogenous” refers to nicotine incorporated into the homogenised plant material and which is provided extrinsically from tobacco material. The exogenous nicotine is therefore a separate and distinct source of nicotine to any nicotine provided intrinsically within tobacco particles. The exogenous nicotine is provided at a level such that it will be the main source of nicotine within the homogenised plant material. Where the homogenised plant material is free from tobacco, as described above, the exogenous nicotine will provide the only source of nicotine.

[0055] The exogenous nicotine may be in the form of natural nicotine, or synthetic nicotine, or a combination of natural nicotine and synthetic nicotine.

[0056] The homogenised plant material has a total exogenous nicotine content of at least 1 percent by weight, on a dry weight basis. Preferably, the homogenised plant material has a total exogenous nicotine content of at least 1.25 percent by weight, more preferably at least 1.5 percent by weight, more preferably at least 1.75 percent by weight, more preferably at least 2 percent by weight, on a dry weight basis.

[0057] The homogenised plant material has a total exogenous nicotine content of less than or equal to 3.5 percent by weight, on a dry weight basis. Preferably, the homogenised plant material has a total exogenous nicotine content of less than or equal to 3.25 percent by weight and more preferably, less than or equal to 3 percent by weight, on a dry weight basis.

[0058] For example, the homogenised plant material may have a total exogenous nicotine content of between 1 .25 percent by weight and 3.5 percent by weight, between 1.5 percent by weight and 3.5 percent by weight, between 1.75 percent by weight and 3.5 percent by weight, or between 2 percent by weight and 3.5 percent by weight, on a dry weight basis.

[0059] For example, the homogenised plant material may have a total exogenous nicotine content of between 1 percent by weight and 3.25 percent by weight, between 1.25 percent by weight and 3.25 percent by weight, between 1.5 percent by weight and 3.25 percent by weight, between 1.75 percent by weight and 3.25 percent by weight, or between 2 percent by weight and 3.25 percent by weight, on a dry weight basis.

[0060] For example, the homogenised plant material may have a total exogenous nicotine content of between 1 percent by weight and 3 percent by weight, between 1.25 percent by weight and 3 percent by weight, between 1.5 percent by weight and 3 percent by weight, between 1.75 percent by weight and 3 percent by weight, or between 2 percent by weight and 3 percent by weight, on a dry weight basis.

[0061] As defined above, the homogenised plant material used to form the aerosol-generating substrate of aerosol-generating articles according to the present invention additionally comprises an acidic pH modifier, to optimise the pH of the homogenised plant material and the slurry from which it is produced. As described above, this has been found to advantageously minimise the loss of nicotine during production of the homogenised plant material, so that a greater proportion of the exogenous nicotine can be retained in the homogenised plant material and delivered in the aerosol upon heating.

[0062] Inclusion of the acidic pH modifier in the homogenised plant material decreases the pH of the homogenised plant material by a measurable amount. Preferably, inclusion of the acidic pH modifier decreases the pH of the homogenised plant material by at least 0.5 compared to the pH of a similar homogenised plant material that does not include the acidic pH modifier. The level of pH adjustment required for a homogenised plant material will depend upon the nature of the plant particles that are used, since some plants will produce a slurry with a significantly higher pH than others. For example, it has been found that for some plant particles, such as ginger particles, a greater level of pH adjustment is required than for other plant particles. The type of acidic pH modifier and the amount of acidic pH modifier that is used can be adapted according to the level of pH adjustment that is required.

[0063] Preferably, the acidic pH modifier comprises an acid. More preferably, the acidic pH modifier comprises one or more carboxylic acids. Suitable carboxylic acids for use as the acidic pH modifier include but are not limited to: fumaric acid, maleic acid, malic acid, adipic acid, succinic acid, lactic acid, levulinic acid, acetic acid, benzoic acid, citric acid, fumaric acid, maleic acid, and malic acid.

[0064] In particularly preferred embodiments, the acidic pH modifier comprises at least one of lactic acid and levulinic acid.

[0065] According to the present invention, the homogenised plant material comprises at least 1 percent by weight of the acidic pH modifier, on a dry weight basis. Preferably, the homogenised plant material comprises at least 1.05 percent by weight of the acidic pH modifier, more preferably at least 1.1 percent by weight of the acidic pH modifier, on a dry weight basis.

[0066] Preferably, the homogenised plant material comprises less than or equal to 2 percent by weight of the acidic pH modifier, more preferably less than or equal to 1 .75 percent by weight of the acidic pH modifier, more preferably less than 1.5 percent by weight of the acidic pH modifier, on a dry weight basis.

[0067] For example, the homogenised plant material may comprise between 1 percent by weight and 2 percent by weight of the acidic pH modifier, or between 1.05 percent by weight and 2 percent by weight of the acidic pH modifier, or between 1.1 percent by weight and 2 percent by weight of the acidic pH modifier, on a dry weight basis.

[0068] For example, the homogenised plant material may comprise between 1 percent by weight and 1 .75 percent by weight of the acidic pH modifier, or between 1.05 percent by weight and 1.75 percent by weight of the acidic pH modifier, or between 1.1 percent by weight and 1.75 percent by weight of the acidic pH modifier, on a dry weight basis.

[0069] For example, the homogenised plant material may comprise between 1 percent by weight and 1 .5 percent by weight of the acidic pH modifier, or between 1 .05 percent by weight and 1.5 percent by weight of the acidic pH modifier, or between 1.1 percent by weight and 1.5 percent by weight of the acidic pH modifier, on a dry weight basis.

[0070] In particularly preferred embodiments, the homogenised plant material comprises about 1.1 percent by weight of the acidic pH modifier. Preferably, the homogenised plant material has a pH less than or equal to 6. More preferably, the homogenised plant material has a pH less than or equal to 5.5.

[0071] Preferably, the homogenised plant material has a pH of at least 4. For example, the pH of the homogenised plant material may be between 4 and 6, or between 4 and 5.5.

[0072] The pH of the homogenised plant material is measured by dispersing a 0.5 g sample of the homogenised plant material in 5 grams of water, agitating the dispersion and then measuring the pH of the dispersion using a pH electrode.

[0073] According to the invention, the homogenised plant material comprises at least 10 percent by weight of aerosol former, on a dry weight basis. The homogenised plant material may comprise one or more aerosol formers. Suitable aerosol formers for inclusion in the homogenised plant material are known in the art and include, but are not limited to: polyhydric alcohols, such as triethylene glycol, propylene glycol, 1,3-butanediol and glycerol; esters of polyhydric alcohols, such as glycerol mono-, di- or triacetate; and aliphatic esters of mono-, di- or polycarboxylic acids, such as dimethyl dodecanedioate and dimethyl tetradecanedioate. Preferably, the aerosol former comprises one or more of glycerol and propylene glycol. The aerosol former may consist of glycerol or propylene glycol or of a combination of glycerol and propylene glycol.

[0074] Preferably, the homogenised plant material has an aerosol former content of at least 12 percent by weight on a dry weight basis. More preferably, the homogenised plant material has an aerosol former content of at least 15 percent by weight on a dry weight basis.

[0075] The homogenised plant material preferably has an aerosol former content of less than or equal to 30 percent by weight on a dry weight basis. More preferably, the homogenised plant material has an aerosol former content of less than or equal to 25 percent by weight on a dry weight basis. More preferably, the homogenised plant material has an aerosol former content of less than or equal to 20 percent by weight on a dry weight basis.

[0076] For example, the aerosol former content of the homogenised plant material is preferably between 10 percent and 30 percent by weight, or between 12 percent and 25 percent by weight, or between 15 percent and 20 percent by weight, on a dry weight basis.

[0077] Preferably, the homogenised plant material comprises glycerol as an aerosol former. For example, the homogenised plant material may comprise between 10 percent and 30 percent by weight of glycerol, or between 12 percent and 25 percent by weight of glycerol, or between 15 percent and 20 percent by weight of glycerol, on a dry weight basis.

[0078] The homogenised plant material may further comprise one or more cellulose based strengthening agents. Inclusion of one or more cellulose based strengthening agents in the homogenised plant material may advantageously increase the tensile strength of the homogenised plant material. A homogenised plant material having a higher tensile strength may advantageously be less likely to deteriorate or break during manufacture and storage. Advantageously, the homogenised plant material may comprise one or more cellulose based strengthening agents selected from cellulose fibres, cellulose powder, and microcrystalline cellulose (MCC). The cellulose based strengthening agent is in the form of an inert cellulosic material, which is sensorially neutral. The cellulose based strengthening agent therefore does not substantially impact the organoleptic characteristics of the aerosol generated from the aerosol-generating substrate. For example, the additional cellulose is preferably a substantially tasteless and odourless material.

[0079] The homogenised plant material preferably has a total cellulose based strengthening agent content of at least 10 percent by weight, more preferably at least 15 percent by weight, more preferably at least 20 percent by weight, on a dry weight basis, more preferably at least 25 percent by weight, on a dry weight basis.

[0080] As used herein with reference to the invention, the term “total cellulose based strengthening agent content” is used to describe the combined content of all cellulose based strengthening agents in the homogenised plant material.

[0081] The homogenised plant material preferably has a total cellulose based strengthening agent content of up to 50 percent by weight, up to 45 percent by weight, or up to 40 percent by weight, on a dry weight basis.

[0082] The homogenised plant material may have a total cellulose based strengthening agent content of between 10 percent by weight and 50 percent by weight, between 15 percent by weight and 45 percent by weight, or between 20 percent by weight and 40 percent by weight, or between 25 percent and 40 percent by weight, on a dry weight basis.

[0083] Preferably, the homogenised plant material comprises cellulose fibres. Cellulose fibres may be particularly effective at increasing the tensile strength of the homogenised plant material. Advantageously, the combination of cellulose fibres with the non-tobacco plant particles in the homogenised plant material of the present invention has been found to be particularly effective in providing an optimised tensile strength for the homogenised plant material.

[0084] The homogenised plant material may comprise cellulose fibres having a length of at least 0.5 millimetres, at least 0.6 millimetres, at least 0.7 millimetres, or at least 0.9 millimetres.

[0085] The homogenised plant material may comprise cellulose fibres having a length of less than or equal to 2 millimetres, less than or equal to 1 .8 millimetres, less than or equal to 1.6 millimetres, or less than or equal to 1.4 millimetres.

[0086] The homogenised plant material preferably has a cellulose fibre content of at least 2 percent by weight, more preferably at least 5 percent by weight, more preferably at least 10 percent by weight, on a dry weight basis.

[0087] The homogenised plant material preferably has a cellulose fibre content of less than or equal to 25 percent by weight, less than or equal to 20 percent by weight, or less than or equal to 15 percent by weight, on a dry weight basis. For example, the homogenised plant material may have a cellulose fibre content of between 2 percent by weight and 25 percent by weight, or between 5 percent by weight and 20 percent by weight, or between 10 percent by weight and 15 percent by weight, on a dry weight basis.

[0088] Preferably, the homogenised plant material comprises cellulose powder. Cellulose powder acts as an inert filler and may be useful to optimise the balance of flavour provided by the nontobacco plant material, so that the flavour characteristics of the aerosol generated from the homogenised plant material can be tailored. In particularly preferred embodiments, the homogenised plant material comprises both cellulose powder and cellulose fibres.

[0089] The homogenised plant material preferably has a cellulose powder content of at least 10 percent by weight, more preferably at least 15 percent by weight, more preferably at least 20 percent by weight, more preferably at least 25 percent by weight on a dry weight basis.

[0090] The homogenised plant material preferably has a cellulose powder content of less than or equal to 45 percent by weight, less than or equal to 40 percent by weight, or less than or equal to 35 percent by weight, on a dry weight basis.

[0091] For example, the homogenised plant material may have a cellulose powder content of between 10 percent by weight and 45 percent by weight, or between 15 percent by weight and 40 percent by weight, or between 20 percent by weight and 35 percent by weight, or between 25 percent by weight and 35 percent by weight, on a dry weight basis.

[0092] In alternative embodiments, the homogenised plant material may comprise microcrystalline cellulose (MCC) in addition to or instead of the cellulose powder.

[0093] For example, the homogenised plant material may have an MCC content of between 10 percent by weight and 45 percent by weight, or between 15 percent by weight and 40 percent by weight, or between 20 percent by weight and 35 percent by weight, or between 25 percent by weight and 35 percent by weight, on a dry weight basis.

[0094] Preferably, where cellulose powder or MCC is incorporated into the homogenised plant material, the cellulose powder or MCC has an average particle size of less than or equal to 75 microns, more preferably less than or equal to 60 microns.

[0095] Preferably, the weight ratio of the non-tobacco plant particles to the cellulose based strengthening agent is at least 0.5, more preferably at least 0.6, more preferably at least 0.7. The weight ratio of the non-tobacco plant particles to the cellulose based strengthening agent may be up to 2.5, or up to 2.

[0096] The homogenised plant material may further comprise a cellulose ether. The inclusion of a cellulose ether has been found to provide a particularly desirable level of tensile strength and flexibility, in particular, when used in combination with a cellulose based strengthening agent.

[0097] The homogenised plant material preferably comprises at least 2 percent by weight of cellulose ether, more preferably at least 3 percent by weight of cellulose ether, more preferably at least 4 percent by weight of cellulose ether and more preferably 5 percent by weight of cellulose ether, on a dry weight basis. The homogenised plant material preferably comprises no more than 10 percent by weight of cellulose ether, preferably no more than 9 percent by weight of cellulose ether, more preferably no more than 8 percent by weight of cellulose ether, more preferably no more than 7 percent by weight of cellulose ether, on a dry weight basis.

[0098] For example, the homogenised plant material may comprise between about 2 percent by weight and 10 percent by weight of cellulose ether, or about 3 percent by weight and about 9 percent by weight of cellulose ether, or between about 4 percent by weight and about 8 percent by weight of cellulose ether, or between about 4 percent by weight and about 7 percent by weight of cellulose ether, or about 5 percent by weight of cellulose ether, on a dry weight basis.

[0099] Suitable cellulose ethers for use in the present invention include but are not limited to methyl cellulose, hydroxypropyl methyl cellulose, ethyl cellulose, hydroxyl ethyl cellulose, hydroxyl propyl cellulose, ethyl hydroxyl ethyl cellulose and carboxymethyl cellulose (CMC).

[0100] In particularly preferred embodiments, the cellulose ether is carboxymethyl cellulose. For example, the homogenised plant material may comprise between about 2 percent by weight and 10 percent by weight of carboxymethyl cellulose, or about 3 percent by weight and about 9 percent by weight of carboxymethyl cellulose, or between about 4 percent by weight and about 8 percent by weight of carboxymethyl cellulose, or between about 4 percent by weight and about 7 percent by weight of cellulose ether, or about 5 percent by weight of carboxymethyl cellulose, on a dry weight basis.

[0101] The homogenised plant material may further comprise one or more binders to help agglomerate the non-tobacco plant particles. Suitable binders for inclusion in the homogenised plant material as described herein are known in the art and include, but are not limited to: gums such as, for example, guar gum, xanthan gum, arabic gum and locust bean gum; cellulosic binders such as, for example, hydroxypropyl cellulose, carboxymethyl cellulose, hydroxyethyl cellulose, methyl cellulose and ethyl cellulose; polysaccharides such as, for example, starches, organic acids, such as alginic acid, conjugate base salts of organic acids, such as sodiumalginate, agar and pectins; and combinations thereof. Preferably, the binder comprises guar gum. The binder may be present in an amount of from about 1 percent to about 10 percent by weight, based on the dry weight of the homogenised plant material, preferably in an amount of from about 2 percent to about 5 percent by weight, based on the dry weight of the homogenised plant material.

[0102] The homogenised plant material used in articles and substrates according to the invention may be produced by various processes including paper making, casting, dough reconstitution, extrusion or any other suitable process.

[0103] Some processes such as casting and paper making are more suitable for producing homogenised plant material in sheet form. The term “cast leaf” is used herein to refer to a product made by a casting process that is based on casting a slurry comprising plant particles (for example, the non-tobacco plant particles), aerosol former (for example, glycerol) and any other components of the homogenised plant material onto a supportive surface, such as a belt conveyor, drying the slurry and removing the dried sheet from the supportive surface. An example of the casting or cast leaf process is described in, for example, US-A-5,724,998 for making cast leaf tobacco. In a cast leaf process, particulate plant materials are produced by pulverizing, grinding, or comminuting parts of the plant.

[0104] Preferably, the homogenised plant material used in articles and substrates according to the present invention may be produced by casting, that is to say, it may be in the form of cast leaf.

[0105] In methods according to the present invention, as defined above, the non-tobacco plant particles are mixed with a liquid component, typically water, to form a slurry. Other components in the slurry include exogenous nicotine, an acidic pH modifier, an aerosol former and other optional components as described above. The amount of the acidic pH modifier is adapted in order to provide a desired pH of the slurry. The amount required will depend upon the nature of the non-tobacco plant particles and the resultant pH of the slurry without the acidic pH modifier. Preferably, the amount of the acidic pH modifier is adapted to provide the slurry with a pH of less than 5.5.

[0106] Once the desired pH has been achieved, the slurry is cast in the form of a sheet onto a supportive surface and dried into a sheet of homogenised plant material. Preferably, the drying takes place at between 80 and 160 degrees Celsius. Such methods are used to produce homogenised plant material in the form of cast leaf.

[0107] An alternative paper-making process for producing sheets of homogenised plant material comprises a first step of mixing a plant material and water to form a dilute suspension comprising mostly separate cellulose fibres. This first step may involve soaking and applying heat. The suspension has a lower viscosity and a higher water content than the slurry produced in the casting process. The suspension may then be separated into an insoluble portion containing solid fibrous components and a liquid or aqueous portion comprising soluble plant substances. The water remaining in the insoluble fibrous portion may be drained through a screen, acting as a sieve, such that a web of randomly interwoven fibres may be laid down. Water may be further removed from this web by pressing with rollers, sometimes aided by suction or vacuum. When most of the moisture has been removed, a generally flat, uniform sheet of plant fibres is achieved. The soluble plant substances that were removed from the sheet may be concentrated, and the concentrated plant substances may be added back to the sheet resulting in a sheet of homogenised plant material. This process, as described in US 3,860,012, has been used with tobacco to make reconstituted tobacco products, also known as tobacco paper.

[0108] Other known processes that can be applied to producing homogenised plant materials are dough reconstitution processes of the type described in, for example, US-A-3,894,544; and extrusion processes of the type described in, for example, in GB-A-983,928. Typically, the densities of homogenised plant materials produced by extrusion processes and dough reconstitution processes are greater than the densities of the homogenised plant materials produced by casting processes.

[0109] Preferably, the homogenised plant material is in the form of one or more sheets of homogenised plant material.

[0110] The one or more sheets as described herein may each individually have a thickness of between 100 microns and 600 microns, preferably between 100 microns and 400 microns, preferably between 150 microns and 300 microns, and most preferably between 200 microns and 280 microns. Individual thickness refers to the thickness of the individual sheet, whereas combined thickness refers to the total thickness of all sheets that make up the aerosol-generating substrate. For example, if the aerosol-generating substrate is formed from two individual sheets, then the combined thickness is the sum of the thickness of the two individual sheets or the measured thickness of the two sheets where they are stacked in the aerosol-generating substrate.

[0111] The one or more sheets as described herein may each have an average thickness of between 100 microns and 600 microns, preferably between 100 microns and 400 microns, preferably between 150 microns and 300 microns, and most preferably between 200 microns and 280 microns.

[0112] The one or more sheets as described herein may each individually have a grammage of between about 100 grams per square metre and about 300 grams per square metre.

[0113] The one or more sheets as described herein may each individually have a density of from about 0.3 g / cm3to about 1.3 g / cm3, and preferably from about 0.7 g / cm3to about 1.0 g / cm3.

[0114] The one or more sheets as described herein may each individually have a tensile strength at peak in a cross direction of between 50 N / m and 400 N / m or preferably between 150 N / m and 350 N / m, normalized to a thickness of a single sheet, whereby the thickness of the single sheet ranges from 215 pm to 275 pm. The one or more sheets as described herein may each individually have a tensile strength at peak in a machine direction of between 100 N / m and 800 N / m or preferably between 280 N / m and 620 N / m, normalized to a thickness of a single sheet, whereby the thickness of the single sheet ranges from 215 pm to 275 pm. The machine direction refers to the direction in which the sheet material would be rolled onto or unrolled from a bobbin and fed into a machine, while the cross direction is perpendicular to the machine direction. Such values of tensile strength make sheets and methods described herein particularly suitable for subsequent operations involving mechanical stresses.

[0115] The provision of a sheet having the levels of thickness, grammage and tensile strength as defined above advantageously optimises the machinability of the sheet to form the aerosolgenerating substrate and ensures that damage, such as tearing of the sheet, is avoided during high speed processing of the sheet.

[0116] Preferably the one or more sheets may be in the form of one or more gathered sheets. Preferably the aerosol-generating substrate is in the form of a rod comprising one or more gathered sheets of the homogenised plant material, circumscribed by a wrapper. The sheets of homogenised plant material may preferably be gathered transversely relative to the longitudinal axis thereof and circumscribed with a wrapper to form a continuous rod or a plug. The continuous rod may be severed into a plurality of discrete rods or plugs. The wrapper may be a paper wrapper or a non-paper wrapper. Suitable paper wrappers for use in specific embodiments of the invention are known in the art and include, but are not limited to: cigarette papers; and filter plug wraps.

[0117] The sheets of homogenised plant material may be textured through crimping, embossing, perforating or otherwise texturing prior to gathering or being cut into shreds. Preferably the sheets of homogenised plant material are crimped prior to gathering, such that the homogenised plant material may be in the form of a crimped sheet, more preferably in the form of a gathered crimped sheet. As used herein, the term “crimped sheet” denotes a sheet having a plurality of substantially parallel ridges or corrugations.

[0118] Alternatively, the homogenised plant material may be in the form of a plurality of shreds, strands or strips. The shreds, strands or strips may be used to form a plug. In such embodiments, the aerosol-generating substrate therefore comprises shredded homogenised plant material.

[0119] In some embodiments, the strands may be formed in situ within the aerosol-generating substrate as a result of the splitting or cracking of a sheet of homogenised plant material during formation of the aerosol-generating substrate, for example, as a result of crimping. The strands of homogenised plant material within the aerosol-generating substrate may be separate from each other. Alternatively, each strand of homogenised plant material within the aerosolgenerating substrate may be at least partially connected to an adjacent strand or strands along the length of the strands. For example, adjacent strands may be connected by one or more fibres. This may occur, for example, where the strands have been formed due to the splitting of a sheet of homogenised plant material during production of the aerosol-generating substrate, as described above.

[0120] Typically, the width of such shreds, strands or strips is about 5 millimetres, or about 4 millimetres, orabout 3 millimetres, or about 2 millimetres or less. The length of the shreds, strands or strips may be greater than about 5 millimetres, between about 5 millimetres to about 15 millimetres, about 8 millimetres to about 12 millimetres, or about 12 millimetres.

[0121] The plurality of strands preferably extend substantially longitudinally along the length of the aerosol-generating substrate, aligned with the longitudinal axis. Preferably, the plurality of strands are therefore aligned substantially parallel to each other. This provides a relatively uniform, regular structure which facilitates the insertion of an internal heater element into the aerosolgenerating substrate and optimises the efficiency of heating.

[0122] The aerosol-generating substrate of aerosol-generating articles according to the present invention is formed of the homogenised plant material described above. Preferably, the aerosolgenerating articles of the present invention comprise an aerosol-generating substrate in the form of a rod of homogenised plant material circumscribed by a wrapper. The aerosol-generating substrate may have a density of less than or equal to 1000 milligrams per cubic centimetre. Preferably, the aerosol-generating substrate may have a density of less than or equal to 900 milligrams per cubic centimetre. More preferably, the aerosolgenerating substrate may have a density of less than or equal to 800 milligrams per cubic centimetre.

[0123] Preferably, the aerosol-generating substrate may have an average density of at least 200 milligrams per cubic centimetre. More preferably, the aerosol-generating substrate may have a density of at least 300 milligrams per cubic centimetre. More preferably, the aerosol-generating substrate may have a density of at least 400 milligrams per cubic centimetre. More preferably, the aerosol-generating substrate may have a density of at least 500 milligrams per cubic centimetre.

[0124] For example, the aerosol-generating substrate preferably has a density of between 200 milligrams per cubic centimetre and 1000 milligrams per cubic centimetre, or between 300 milligrams per cubic centimetre and 950 milligrams per cubic centimetre, or between 400 milligrams per cubic centimetre and 900 milligrams per cubic centimetre, or between 500 milligrams per cubic centimetre and 800 milligrams per cubic centimetre, or between 700 milligrams per cubic centimetre and 800 milligrams per cubic centimetre.

[0125] The term “density” as used herein in relation to the aerosol-generating substrate refers to the bulk density of the aerosol-generating substrate. This can be calculated by measuring the total weight of the aerosol-generating substrate and dividing this by the volume of the rod of aerosol-generating substrate (excluding any wrapper).

[0126] In some preferred embodiments, the rod of aerosol-generating substrate comprises at least 250 milligrams of homogenised plant material.

[0127] In some preferred embodiments, the rod of aerosol-forming substrate further comprises a heating element arranged to heat the homogenised plant material. The heating element may be one or more susceptor elements. The aerosol-generating substrate may comprise one or more elongate susceptor elements.

[0128] In some preferred embodiments, the rod of aerosol-generating substrate has a length of less than or equal to 20 millimetres. More preferably, the rod of aerosol-generating substrate has a length of less than or equal to 18 millimetres. More preferably, the rod of aerosol-generating substrate has a length of less than or equal to 15 millimetres. More preferably, the rod of aerosol generating substrate has a length of less than or equal to 14 millimetres. More preferably, the rod of aerosol-generating substrate has a length of less or equal to than 13 millimetres.

[0129] Preferably, the rod of aerosol-generating substrate has a length of at least 6 millimetres. More preferably, the rod of aerosol-generating substrate has a length of at least 10 millimetres.

[0130] For example, the rod of aerosol-generating substrate has a length of between 6 millimetres and 20 millimetres, or between 6 millimetres and 18 millimetres, or between 6 millimetres and 15 millimetres, or between 6 millimetres and 14 millimetres, or between 6 millimetres and 13 millimetres, or between 10 millimetres and 18 millimetres, or between 10 millimetres and 15 millimetres, or between 10 millimetres and 14 millimetres, or between 10 millimetres and 13 millimetres.

[0131] In some preferred embodiments, a ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is less than 0.4. More preferably, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is less than 0.35. More preferably, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is less than 0.3. Preferably, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is at least 0.15. More preferably, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is at least 0.2. More preferably, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is at least 0.25. More preferably, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article is at least 0.3.

[0132] For example, the ratio of the length of the rod of aerosol-generating substrate to the length of the aerosol-generating article may be between 0.15 and 0.4, or between 0.2 and 0.35, or between 0.25 and 0.3, or between 0.3 and 0.4.

[0133] The rod of aerosol-generating substrate preferably has an external diameter that is approximately equal to the external diameter of the aerosol-generating article.

[0134] The “external diameter of the rod of aerosol-generating substrate” may be calculated as the average of a plurality of measurements of the diameter of the rod of aerosol-generating substrate taken at different locations along the length of the rod of aerosol-generating substrate.

[0135] Preferably, the rod of aerosol-generating substrate has an external diameter of at least about 5 millimetres. More preferably, the rod of aerosol-generating substrate has an external diameter of at least about 6 millimetres. Even more preferably, the rod of aerosol-generating substrate has an external diameter of at least about 7 millimetres.

[0136] The rod of aerosol-generating substrate preferably has an external diameter of less than or equal to about 12 millimetres. More preferably, the rod of aerosol-generating substrate has an external diameter of less than or equal to about 10 millimetres. Even more preferably, the rod of aerosol-generating substrate has an external diameter of less than or equal to about 8 millimetres.

[0137] In some embodiments, the rod of aerosol-generating substrate has an external diameter from about 5 millimetres to about 12 millimetres, preferably from about 6 millimetres to about 12 millimetres, more preferably from about 7 millimetres to about 12 millimetres. In other embodiments, the rod of aerosol-generating substrate has an external diameter from about 5 millimetres to about 12 millimetres, preferably from about 6 millimetres to about 10 millimetres, more preferably from about 7 millimetres to about 10 millimetres. In further embodiments, the rod of aerosol-generating substrate has an external diameter from about 5 millimetres to about 8 millimetres, preferably from about 6 millimetres to about 8 millimetres, more preferably from about 7 millimetres to about 8 millimetres.

[0138] In particularly preferred embodiments, the rod of aerosol-generating substrate has an external diameter of less than about 7.5 millimetres. By way of example, the rod of aerosolgenerating substrate may an external diameter of about 7.2 millimetres.

[0139] The aerosol-generating article may have any desired shape. For example, the aerosolgenerating article may be substantially cylindrical.

[0140] The aerosol-generating article may have any desired transverse cross-section. For example, the aerosol-generating article may have a substantially circular, oval or elliptical transverse cross-section.

[0141] The aerosol-generating article may have any desired length. For example, the aerosolgenerating article may have a length of between 30 millimetres and 70 millimetres, between 35 millimetres and 65 millimetres, or between 40 millimetres and 60 millimetres.

[0142] The aerosol-generating article may have any desired width. For example, the aerosolgenerating article may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres.

[0143] The aerosol-generating article may include one or more additional components.

[0144] The one or more other components may include one or more of an upstream element, a support element, an aerosol-cooling element and a mouthpiece element.

[0145] The aerosol-generating article may comprise an upstream element located at the distal end of the aerosol-generating article. The upstream element may be located immediately upstream of the solid aerosol-generating substrate.

[0146] The upstream element may advantageously prevent direct contact with the solid aerosolgenerating substrate. This may advantageously help to prevent displacement or deformation of the susceptor during transport and handling of the aerosol-generating article.

[0147] The upstream element may comprise a plug of porous material. For example, the upstream element may comprise a cellulose acetate plug.

[0148] The upstream element may have any desired shape. For example, the upstream element may be substantially cylindrical.

[0149] The upstream element may have any desired transverse cross-section. For example, the support element may have a substantially circular, oval or elliptical transverse cross-section.

[0150] The upstream element may have any desired length. For example, the upstream element may have a length of between 1 millimetre and 10 millimetres, between 1 millimetre and 8 millimetres, or between 1 millimetre and 6 millimetres. For example, the upstream element may have a length of between 3 millimetres and 10 millimetres, between 3 millimetres and 8 millimetres, or between 3 millimetres and 6 millimetres.

[0151] The upstream element may have any desired width. For example, the upstream element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The upstream element may have a width that is substantially the same as the width of the aerosol-generating article.

[0152] The aerosol-generating article may comprise a support element located between the solid aerosol-generating substrate and the proximal end of the aerosol-generating article.

[0153] The support element may be located immediately downstream of the solid aerosolgenerating substrate.

[0154] The support element may comprise a hollow tubular segment. For example, the support element may comprise a hollow cellulose acetate tube. The hollow tubular segment may define a longitudinal cavity providing an unrestricted flow channel.

[0155] The support element may have any desired shape. For example, the support element may be substantially cylindrical.

[0156] The support element may have any desired transverse cross-section. For example, the support element may have a substantially circular, oval or elliptical transverse cross-section.

[0157] The support element may have any desired length. For example, the support element may have a length of between 5 millimetres and 15 millimetres, between 5 millimetres and 12 millimetres, or between 5 millimetres and 10 millimetres. For example, the support element may have a length of between 7 millimetres and 15 millimetres, between 7 millimetres and 12 millimetres, or between 7 millimetres and 10 millimetres.

[0158] The support element may have any desired width. For example, the support element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The support element may have a width that is substantially the same as the width of the aerosol-generating article.

[0159] The aerosol-generating article may comprise a mouthpiece element located at the proximal end of the aerosol-generating article.

[0160] The mouthpiece element may comprise a plug of porous material. For example, the mouthpiece element may comprise a cellulose acetate plug.

[0161] The mouthpiece element may comprise a mouth end cavity.

[0162] The mouth end cavity may be defined by a hollow tubular element provided at the proximal end of the mouthpiece element.

[0163] The mouth end cavity may be defined by a wrapper.

[0164] The mouthpiece element may have any desired shape. For example, the mouthpiece element may be substantially cylindrical.

[0165] The mouthpiece element may have any desired transverse cross-section. For example, the mouthpiece element may have a substantially circular, oval or elliptical transverse cross-section.

[0166] The mouthpiece may have any desired length. For example, the mouthpiece element may have a length of between 5 millimetres and 20 millimetres, between 5 millimetres and 15 millimetres, or between 5 millimetres and 10 millimetres. For example, the mouthpiece element may have a length of between 6 millimetres and 20 millimetres, between 6 millimetres and 15 millimetres, or between 6 millimetres and 10 millimetres. For example, the mouthpiece element may have a length of between 7 millimetres and 20 millimetres, between 7 millimetres and 15 millimetres, or between 7 millimetres and 10 millimetres.

[0167] The mouthpiece element may have any desired width. For example, the mouthpiece element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The mouthpiece element may have a width that is substantially the same as the width of the aerosol-generating article.

[0168] The aerosol-generating article may comprise an aerosol-cooling element located between the solid aerosol-generating substrate and the proximal end of the aerosol-generating article.

[0169] Where the aerosol-generating article comprises a mouthpiece element, the aerosol-cooling element may be located immediately upstream of the mouthpiece element.

[0170] Where the aerosol-generating article comprises a support element, the aerosol-cooling element may be located immediately downstream of the support element.

[0171] The aerosol-cooling element may comprise a hollow tubular segment. For example, the aerosol-cooling element may comprise a hollow cellulose acetate tube.

[0172] The hollow tubular segment may define a longitudinal cavity providing an unrestricted flow channel.

[0173] The aerosol-cooling element may have any desired shape. For example, the mouthpiece element may be substantially cylindrical.

[0174] The aerosol-cooling element may have any desired transverse cross-section. For example, the aerosol-cooling element may have a substantially circular, oval or elliptical transverse crosssection.

[0175] The aerosol-cooling element may have any desired length. For example, the aerosolcooling element may have a length of between 5 millimetres and 20 millimetres or between 5 millimetres and 15 millimetres. For example, the aerosol-cooling element may have a length of between 6 millimetres and 20 millimetres or between 6 millimetres and 15 millimetres. For example, the aerosol-cooling element may have a length of between 7 millimetres and 20 millimetres or between 7 millimetres and 15 millimetres.

[0176] The aerosol-cooling element may have any desired width. For example, the aerosol-cooling element may have a width of between 5 millimetres and 10 millimetres, between 6 millimetres and 9 millimetres, or between 7 millimetres and 8 millimetres. The aerosol-cooling element may have a width that is substantially the same as the width of the aerosol-generating article.

[0177] The solid aerosol-generating substrate, susceptor and one or more other components of the aerosol-generating article may be assembled within one or more wrappers to form the aerosolgenerating article. For example, the solid aerosol-generating substrate, susceptor and other components of the aerosol-generating article may be assembled within one or more wrappers to form an elongate rod. Suitable wrappers for use in aerosol-generating articles according to the first aspect of the invention are known in the art and include, but are not limited to: cigarette papers; filter plug wraps; tipping papers; metallised papers; metal foils; and metal foil-paper laminates.

[0178] The aerosol-generating article may comprise a ventilation zone located between the solid aerosol-generating substrate and the proximal end of the aerosol-generating article.

[0179] Where the aerosol-generating article comprises an aerosol-cooling element, the ventilation zone may be provided at a location along the aerosol-cooling element.

[0180] The ventilation zone typically comprises a plurality of perforations through the peripheral wall of the hollow tubular element. Preferably, the ventilation zone comprises at least one circumferential row of perforations. In some embodiments, the ventilation zone comprises two circumferential rows of perforations. For example, the perforations may be formed online during manufacturing of the aerosol-generating article. Preferably, each circumferential row of perforations comprises from 8 to 30 perforations.

[0181] An aerosol-generating article of the aerosol-generating systems of the present invention preferably has a ventilation level of at least 25 percent.

[0182] The term “ventilation level” is used throughout the present specification to denote a volume ratio between of the airflow admitted into the aerosol-generating article via the ventilation zone (ventilation airflow) and the sum of the aerosol airflow and the ventilation airflow. The greater the ventilation level, the higher the dilution of the aerosol flow delivered to the consumer. The aerosolgenerating article preferably has a ventilation level of at least 25 percent, more preferably at least 30 percent, even more preferably at least 40 percent, even more preferably at least 50 percent.

[0183] An aerosol-generating article of the present invention preferably has a ventilation level of up to 90 percent. Preferably, an aerosol-generating article in accordance with the present invention has a ventilation level of less than or equal to 80 percent, more preferably less than or equal to 70 percent, even more preferably less than or equal to 60 percent.

[0184] For example, an aerosol-generating article of the present invention preferably has a ventilation level from 25 percent to 90 percent, preferably from 30 percent to 80 percent, more preferably from 40 percent to 70 percent, even more preferably from 50 percent to 60 percent.

[0185] Aerosol-generating articles according to the invention may be assembled using known methods and machinery.

[0186] As mentioned above, aerosol-generating systems according to the invention comprising an aerosol-generating article according to the invention, as described above, and an electrically operated aerosol-generating device comprising a heater element configured to heat the aerosolgenerating substrate of the aerosol-generating article.

[0187] The aerosol-generating device comprises means for heating the aerosol-generating substrate to a temperature sufficient to generate an aerosol from the aerosol-generating substrate. Preferably, the aerosol-generating device comprises a housing defining a cavity configured to receive the aerosol-generating article, and means for heating the aerosol- generating substrate to a temperature sufficient to generate an aerosol from the aerosolgenerating substrate when the aerosol-generating article is received within the cavity.

[0188] The aerosol-generating device may be a handheld aerosol-generating device.

[0189] The aerosol-generating device may be an electrically-operated aerosol-generating device.

[0190] The aerosol-generating device may comprise a power supply and control electronics.

[0191] The aerosol-generating device may comprise a battery and control electronics.

[0192] The aerosol-generating device may be configured to heat the aerosol-generating substrate internally. That is, the aerosol-generating device may be configured to supply heat to the aerosolgenerating substrate from a location internal to the aerosol-generating article.

[0193] For example, in some embodiments the aerosol-generating device comprises a heater element configured to be inserted into the aerosol-generating substrate when the aerosolgenerating article is received within the cavity of the aerosol-generating device.

[0194] In other embodiments, the aerosol-generating article comprises a susceptor element provided at a location within the aerosol-generating substrate, and the aerosol-generating device comprises an inductor coil positioned on or within the housing, a power supply of the aerosolgenerating device being connected to the inductor coil and configured to provide a high frequency oscillating current to the inductor coil.

[0195] The aerosol-generating device may be configured to heat the aerosol-generating substrate externally. That is, the aerosol-generating device may be configured to supply heat to the aerosolgenerating substrate from a location external to the aerosol-generating article. For example, in some embodiments the aerosol-generating device comprises a heater element located about a perimeter of the cavity and configured to heat the aerosol-generating substrate of the aerosolgenerating article from an exterior of the aerosol-generating element of the aerosol-generating article.

[0196] The invention is defined in the claims. However, below there is provided a non-exhaustive list of non-limiting examples. Any one or more of the features of these examples may be combined with any one or more features of another example, embodiment, or aspect described herein.

[0197] EX1. An aerosol-generating article comprising an aerosol-generating substrate, the aerosol-generating substrate including a homogenised plant material, the homogenised plant material comprising: at least 20 percent by weight of non-tobacco plant particles, on a dry weight basis; between 1 percent by weight and 3.5 percent by weight of exogenous nicotine, on a dry weight basis; at least 1 percent by weight of an acidic pH modifier, on a dry weight basis; and at least 10 percent by weight of aerosol former, on a dry weight basis.

[0198] EX2. An aerosol-generating article according to example EX1 , wherein the pH of the homogenised plant material is less than 5.5. EX3. An aerosol-generating article according to example EX1 or EX2, wherein the pH of the homogenised plant material is less than 5.

[0199] EX4. An aerosol-generating article according to any of the preceding examples, wherein the non-tobacco plant particles are selected from: ginger particles, eucalyptus particles, clove particles, star anise particles, chamomile particles, verbena particles, tea particles and combinations thereof.

[0200] EX5. An aerosol-generating substrate according to any of the preceding examples, wherein the non-tobacco plant particles are selected from: ginger particles, eucalyptus particles, clove particles, star anise particles and combinations thereof.

[0201] EX6. An aerosol-generating article according to any of the preceding examples, wherein the non-tobacco plant particles comprise ginger particles.

[0202] EX7. An aerosol-generating article according to any of the preceding examples, wherein the D90 value of the non-tobacco plant particles is at least 200 microns.

[0203] EX8. An aerosol-generating article according to any of the preceding examples, wherein the D90 value of the non-tobacco plant particles is less than 300 microns.

[0204] EX9. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material comprises less than 5 percent by weight of tobacco particles, on a dry weight basis.

[0205] EX10. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material is substantially free from tobacco.

[0206] EX11. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material comprises less than 45 percent by weight of the non-tobacco plant particles, on a dry weight basis.

[0207] EX12. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material comprises at least 2 percent by weight of exogenous nicotine, on a dry weight basis.

[0208] EX13. An aerosol-generating article according to any of the preceding examples, wherein the acidic pH modifier comprises one or more carboxylic acids.

[0209] EX14. An aerosol-generating article according to example EX13, wherein the acidic pH modifier comprises at least one of lactic acid or levulinic acid.

[0210] EX15. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material comprises less than 3 percent by weight of the acidic pH modifier, on a dry weight basis.

[0211] EX16. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material further comprises a cellulose based strengthening agent.

[0212] EX17. An aerosol-generating article according to example EX16, wherein the homogenised plant material comprises at least 10 percent by weight of the cellulose based strengthening agent. EX18. An aerosol-generating article according to example EX16 or EX17, wherein the homogenised plant material comprises at least 25 percent by weight of the cellulose based agent.

[0213] EX19. An aerosol-generating article according to any of examples EX16 to EX18, wherein the weight ratio of the non-tobacco plant particles to the cellulose based agent is at least 0.5.

[0214] EX20. An aerosol-generating article according to example EX20, wherein the homogenised plant material may comprise one or more cellulose based strengthening agents selected from cellulose fibres, cellulose powder, and microcrystalline cellulose (MCC).

[0215] EX21. An aerosol-generating article according to example EX20, wherein the cellulose based strengthening agent comprises cellulose fibres.

[0216] EX22. An aerosol-generating article according to example EX21, wherein the homogenised plant material comprises at least 2 percent by weight of cellulose fibres, on a dry weight basis.

[0217] EX23. An aerosol-generating article according to example EX20, wherein the cellulose based strengthening agent comprises cellulose powder.

[0218] EX24. An aerosol-generating article according to example EX23, wherein the homogenised plant material comprises at least 10 percent by weight of cellulose powder, on a dry weight basis.

[0219] EX25. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material further comprises a cellulose ether.

[0220] EX26. An aerosol-generating article according to example EX25, wherein the homogenised plant material further comprises carboxymethyl cellulose (CMC).

[0221] EX27. An aerosol-generating article according to example EX25 or EX26, wherein the homogenised plant material comprises at least 2 percent by weight of cellulose ether.

[0222] EX28. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material further comprises a binder.

[0223] EX29. An aerosol-generating article according to example EX28, wherein the binder comprises guar gum.

[0224] EX29. An aerosol-generating article according to example EX28 or EX29, wherein the homogenised plant material comprises between 1 percent by weight and 10 percent by weight of binder, on a dry weight basis.

[0225] EX30. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material comprises at least 15 percent by weight of aerosol former.

[0226] EX31. An aerosol-generating article according to any of the preceding examples, wherein the aerosol former comprises glycerol.

[0227] EX32. An aerosol-generating article according to any of the preceding examples, wherein the homogenised plant material is in the form of cast leaf. EX33. An aerosol-generating article according to any of the preceding examples, wherein the aerosol-generating substrate comprises one or more sheets of the homogenised plant material.

[0228] EX34. An aerosol-generating article according to example EX33, wherein the one or more sheets of homogenised plant material are crimped.

[0229] EX35. An aerosol-generating article according to any of the examples EX1 to EX32, wherein the aerosol-generating substrate comprises shredded homogenised plant material.

[0230] EX36. An aerosol-generating article according to any of the preceding examples, comprising a rod of the homogenised plant material circumscribed by a wrapper.

[0231] EX37. An aerosol-generating article according to example EX36, wherein the rod of the homogenised plant material has a length of at least 10 millimetres.

[0232] EX38. An aerosol-generating article according to any of the preceding examples, further comprising a susceptor element within the aerosol-generating substrate.

[0233] EX39. An aerosol-generating article according to any of the preceding examples, wherein the aerosol-generating substrate comprises one or more sheets of the homogenised plant material and wherein each sheet has an average thickness of between 100 microns and 400 microns.

[0234] EX40. An aerosol-generating article according to any of the preceding examples, wherein the aerosol-generating substrate comprises one or more sheets of the homogenised plant material and wherein each sheet has a grammage of between 100 grams per square metre and 300 grams per square metre.

[0235] EX41. An aerosol-generating article according to any of the preceding examples, wherein the aerosol-generating substrate comprises one or more sheets of the homogenised plant material and wherein each sheet has a tensile strength at peak in a cross direction of between 150 N / m and 350 N / m.

[0236] EX42. An aerosol-generating article according to any of the preceding examples, wherein the aerosol-generating substrate comprises one or more sheets of the homogenised plant material and wherein each sheet has a tensile strength at peak in a machine direction of between 100 N / m and 800 N / m.

[0237] EX43. An aerosol-generating article according to any of the preceding examples, further comprising an upstream section provided upstream of the rod of aerosol-generating substrate, the upstream section comprising at least one upstream element.

[0238] EX44. An aerosol-generating article according to example EX43, wherein the upstream element has a length of between 2 millimetres and 8 millimetres.

[0239] EX45. An aerosol-generating article according to any of the preceding examples, further comprising a downstream section provided downstream of the rod of aerosol-generating substrate, the downstream section comprising at least one hollow tubular element abutting a downstream end of the rod of aerosol-generating substrate. EX46. An aerosol-generating article according to example EX45, further comprising a ventilation zone provided at a location along the hollow tubular element of the downstream section.

[0240] EX47. An aerosol-generating article according to example EX 45, wherein the hollow tubular element of the downstream section has a length of between 17 millimetres and 25 millimetres.

[0241] EX48. An aerosol-generating article according to example EX45, wherein the downstream section further comprises a mouthpiece element.

[0242] EX49. An aerosol-generating article according to example EX48, wherein the mouthpiece element comprises at least one mouthpiece filter segment formed of a fibrous filtration material.

[0243] EX50. An aerosol-generating article according to EX48 or EX49, wherein the length of the mouthpiece element is between 3 millimetres and 15 millimetres.

[0244] EX51. An aerosol-generating article according to example EX45, further comprising a paper wrapper circumscribing the rod of aerosol-generating substrate and at least a portion of the hollow tubular element, and wherein the paper wrapper has a thickness of less than or equal to 100 micrometres.

[0245] EX52. An aerosol-generating article according to example EX51 , wherein the paper wrapper has a thickness of less than or equal to 50 micrometres.

[0246] EX53. An aerosol-generating article according to example EX51 or EX52, wherein the paper wrapper has a grammage of less than or equal to 50 grams per square metre.

[0247] EX54. A rod for use as an aerosol-generating substrate in an aerosol-generating article, the rod comprising one or more sheets of a homogenised plant material, the homogenised plant material comprising: at least 20 percent by weight non-tobacco plant particles, on a dry weight basis; between 1 percent by weight and 3.5 percent by weight exogenous nicotine, on a dry weight basis; at least 1 percent by weight acid, on a dry weight basis; and at least 10 percent by weight of aerosol former, on a dry weight basis.

[0248] EX55. An aerosol-generating system comprising an aerosol-generating article according to any of the examples EX1 to EX53 and an electrically operated aerosol-generating device comprising a heater element configured to heat the aerosol-generating substrate of the aerosolgenerating article.

[0249] EX56. A method of making an aerosol-generating substrate for use in the aerosolgenerating article according to any of the examples EX1 to EX53, the method comprising the steps of: forming a slurry comprising non-tobacco plant particles, exogenous nicotine, aerosol former, acidic pH modifier and water, wherein the amount of acidic pH modifier in the slurry is adapted such that the pH of the slurry is less than 5.5; casting the slurry in the form of a sheet; and drying the sheet at between 80 and 160 degrees Celsius.

[0250] Examples will now be further described with reference to the drawings of the accompanying Figures in which:

[0251] Figure 1 is a schematic cross-sectional view of an embodiment of an aerosol generating article according to a first embodiment of the invention; and

[0252] Figure 2 is a schematic cross-sectional view of an embodiment of an aerosol-generating article according to a second embodiment of the invention.

[0253] The aerosol-generating article 1 shown in Figure 1 comprises a rod of aerosol-generating substrate 12, a downstream section 14 located downstream of the rod of aerosol-generating substrate 12 and an upstream section 16 located upstream of the rod of aerosol-generating substrate 12. As shown in Figure 1, the aerosol-generating article 1 has an upstream end 48 and a downstream end 20. The aerosol-generating article 1 may have an overall length of 45 millimetres and an external diameter of 7.2 millimetres.

[0254] The aerosol-generating article 1 further comprises an elongate susceptor element 44 within the rod 12 of aerosol-generating substrate. In more detail, the susceptor element 44 is arranged substantially longitudinally within the aerosol-generating substrate, such as to be approximately parallel to the longitudinal direction of the rod 12. As shown in the drawing of Figure 1 , the susceptor element 44 is positioned in a radially central position within the rod and extends effectively along the longitudinal axis of the rod 12.

[0255] The susceptor element 44 extends all the way from an upstream end to a downstream end of the rod 12. In effect, the susceptor element 44 has substantially the same length as the rod 12 of aerosol-generating substrate.

[0256] In the embodiment of Figure 1, the susceptor element 44 is provided in the form of a strip and has a length of about 12 millimetres, a thickness of about 60 micrometres, and a width of about 4 millimetres.

[0257] The upstream section 16 comprises an upstream element 46 located immediately upstream of the rod 12 of aerosol-generating substrate, the upstream element 46 being in longitudinal alignment with the rod 12. In the embodiment of Figure 1, the downstream end of the upstream element 46 abuts the upstream end of the rod 12 of aerosol-generating substrate. This advantageously prevents the susceptor element 44 from being dislodged. Further, this ensures that the consumer cannot accidentally contact the heated susceptor element 44 after use.

[0258] The upstream element 46 is in the form of a cylindrical plug of cellulose acetate circumscribed by a stiff wrapper. The upstream element 46 may have a length of 5 millimetres and an external diameter of 6.9 millimetres.

[0259] The downstream section 14 of the aerosol-generating article 1 comprises a support element 22 located immediately downstream of the rod of aerosol-generating substrate 12, an aerosolcooling element 24 located immediately downstream of the support element 22, and a mouthpiece element 42 located immediately downstream of the aerosol-cooling element 24. The support element 22 and the aerosol-cooling element 24 together define an intermediate hollow section 50 of the aerosol-generating article 1.

[0260] The support element 22 comprises a first hollow tubular element 26. The first hollow tubular element 26 is in the form of a hollow cylindrical tube made of cellulose acetate. The first hollow tubular element 26 defines an internal cavity 28 that extends from an upstream end 30 of the first hollow tubular element to a downstream end 32 of the first hollow tubular element 20. The first hollow tubular element 26 may have a length of 8 millimetres and an external diameter of 6.9 millimetres. The first hollow tubular element 26 may have an internal diameter of 3.25 millimetres.

[0261] The aerosol-cooling element 24 comprises a second hollow tubular element 34. The second hollow tubular element 34 is in the form of a hollow cylindrical tube made of cellulose acetate. The second hollow tubular element 34 defines an internal cavity 36 that extends from an upstream end 38 of the second hollow tubular element to a downstream end 40 of the second hollow tubular element 34. The second hollow tubular element 34 may have a length of 8 millimetres and an external diameter of 6.9 millimetres. The second hollow tubular element 34 may have an internal diameter of 5 millimetres.

[0262] As shown by the dashed vertical line in Figure 1 , the aerosol-generating article 1 comprises a ventilation zone 60 provided at a location along the second hollow tubular element 34. The ventilation zone may be provided 2 millimetres from the upstream end of the second hollow tubular element 34. A ventilation level of the aerosol-generating article 1 may be 35 percent.

[0263] The mouthpiece element 42 is in the form of a cylindrical plug of low-density cellulose acetate. The mouthpiece element 42 may have a length of 12 millimetres and an external diameter of 6.9 millimetres.

[0264] The rod of aerosol-generating substrate 12 may have a length of 12 millimetres and an external diameter of 6.9 millimetres.

[0265] The rod of aerosol-generating substrate 12 comprises a gathered sheet of homogenised plant material comprising ginger particles. Suitable compositions are shown below in Table 1.

[0266] The homogenised plant material is produced by forming a slurry of the ginger particles, nicotine, glycerol and cellulose fibres in water. The pH of the slurry prior to the addition of the acidic pH modifier is approximately 7.7. After the addition of the acidic pH modifier, the pH of the slurry reduces to approximately 5.6. The slurry is cast onto a supportive surface to form a sheet and the sheet is dried. The pH of the dried sheet is also approximately 5.6.

[0267] In use, a user draws on the mouthpiece element 42 of the aerosol-generating article 1. When a user draws on the mouthpiece 42, air is drawn into the aerosol-generating article 1 through the upstream end 48. The drawn air passes through the upstream element 46 to the rod of aerosol-generating substrate 12. Heating of the rod of aerosol-generating substrate releases volatile and semi-volatile compounds, which form an aerosol that is entrained in the drawn air as it flows through the rod of aerosol-generating substrate 12. The drawn air and entrained aerosol pass through the intermediate hollow section 50 of the aerosol-generating article 1 , where they cool and condense. The cooled aerosol then passes through the mouthpiece element 42 of the aerosol-generating article 1 and into the mouth of the user. Table 1

[0268] The aerosol-generating article 2 shown in Figure 2 comprises a rod of aerosol-generating substrate 212, a downstream section 214 located downstream of the rod of aerosol-generating substrate 212 and an upstream section 216 located upstream of the rod of aerosol-generating substrate 212. As shown in Figure 2, the aerosol-generating article 2 has an upstream end 248 and a downstream end 220. The aerosol-generating article 2 may have an overall length of 45 millimetres and an external diameter of 7.2 millimetres.

[0269] The upstream section 216 of the aerosol-generating article 2 comprises an upstream element 346 located immediately upstream of the rod of aerosol-generating substrate 212.

[0270] The upstream element 246 is in the form of a cylindrical plug of cellulose acetate circumscribed by a stiff wrapper. The upstream element 246 may have a length of 5 millimetres, an external diameter of 7.2 millimetres and an internal diameter of 5.1 millimetres. The downstream section 214 of the aerosol-generating article 2 comprises an aerosolcooling element 224 located immediately downstream of the rod of aerosol-generating substrate 212, and a mouthpiece element 42 located immediately downstream of the aerosol-cooling element 224. The aerosol-cooling element 224 defines an intermediate hollow section 250 of the aerosol-generating article 2.

[0271] The aerosol-cooling element 224 comprises a hollow tubular element 234. The hollow tubular element 234 is in the form of a hollow cylindrical tube made of cellulose acetate. The hollow tubular element 234 defines an internal cavity 236 that extends from an upstream end 238 of the hollow tubular element to a downstream end 240 of the hollow tubular element 234. The hollow tubular element 234 may have a length of 21 millimetres and an external diameter of 7.2 millimetres. The hollow tubular element 234 may have an internal diameter of 3.25 millimetres.

[0272] The mouthpiece element 242 is in the form of a cylindrical plug of low-density cellulose acetate. The mouthpiece element 242 may have a length of 7 millimetres and an external diameter of 7.2 millimetres.

[0273] The rod of aerosol-generating substrate 212 may have a length of 12 millimetres and an external diameter of 7.2 millimetres.

[0274] The rod of aerosol-generating substrate 212 comprises a shredded homogenised plant material. Suitable compositions for the homogenised plant material are shown below in Table 2.

[0275] The homogenised plant material is produced by forming a slurry of the clove particles, nicotine, glycerol and cellulose fibres in water. The pH of the slurry prior to the addition of the acidic pH modifier is approximately 4.8. After the addition of the acidic pH modifier, the pH of the slurry reduces to approximately 4.1. The slurry is cast onto a supportive surface to form a sheet and the sheet is dried, then shredded. The pH of the dried sheet is also approximately 4.1.

[0276] In use, a user draws on the mouthpiece element 242 of the aerosol-generating article 2. When a user draws on the mouthpiece 242, air is drawn into the aerosol-generating article 2 through the upstream end 248. The drawn air passes to the rod of aerosol-generating substrate 212. Heating of the rod of aerosol-generating substrate releases volatile and semi-volatile compounds, which form an aerosol that is entrained in the drawn air as it flows through the rod of aerosol-generating substrate 212. The drawn air and entrained aerosol pass through the intermediate hollow section 250 of the aerosol-generating article 2, where they cool and condense. The cooled aerosol then passes through the mouthpiece element 242 of the aerosolgenerating article 2 and into the mouth of the user.

[0277] As shown by the dashed vertical line in Figure 2, the aerosol-generating article 2 comprises a ventilation zone 260 provided at a location along the second hollow tubular element 234. A ventilation level of the aerosol-generating article 1 may be 35 percent.

[0278] Table 2

[0279] Comparative Examples The technical effect provided by the inclusion of an acidic pH modifier in the homogenised plant material used in the articles according to the present invention is demonstrated by the following comparative examples. In each example, an aerosol-generating article according to the invention as defined above comprising a homogenised plant material was heated as described below and the nicotine delivery in the resulting aerosol was measured. The same test was carried out with an article including a homogenised plant material having a similar composition but without the inclusion of an acidic pH modifier.

[0280] For the purposes of the comparative examples, an aerosol-generating article incorporating the aerosol-generating substrate is heated with a flat heating profile at 270 degrees Celsius in a Tobacco Heating System 2.2 holder (THS2.2 holder) under the Health Canada machine-smoking regimen. The Tobacco Heating System 2.2 holder (THS2.2 holder) corresponds to the commercially available IQOS device (Philip Morris Products SA, Switzerland).

[0281] The Health Canada smoking regimen is a well-defined and accepted smoking protocol as defined in Health Canada 2000 - Tobacco Products Information Regulations SCR / 2000-273, Schedule 2; published by Ministry of Justice Canada. The test method is described in ISO / TR 19478-1 :2014. In a Health Canada smoking test, an aerosol is collected from the sample aerosolgenerating substrate over 12 puffs with a puff volume of 55 millimetres, puff duration of 2 seconds and puff interval of 30 seconds, with all ventilation blocked if ventilation is present.

[0282] Comparative Example 1 - homogenised plant materials with ginger particles

[0283] The following homogenised plant materials were produced and incorporated into an aerosol-generating article as described above in relation to Figure 1 . Samples A and B are according to the present invention whilst Samples X1 and Y1 each provide a comparative composition, which does not include an acidic pH modifier.

[0284] The homogenised plant materials had the following pH values:

[0285] The inclusion of the acidic pH modifier was therefore found to significantly decrease the pH of the sample by more than 2.

[0286] The following levels of nicotine were measured in the aerosols generated from Samples A, B, X1 and Y1 :

[0287] The table above shows the actual delivery of nicotine in the aerosol, in mg per article, as well as the transfer rate of nicotine, which corresponds to the percentage of nicotine present in the substrate that is transferred into the aerosol.

[0288] As demonstrated by these results, the inclusion of lactic acid in the ginger containing Samples A and B to reduce the pH values of the homogenised plant material resulted in a very significant improvement in the transfer rate of nicotine from the homogenised plant material into the aerosol compared to the comparative samples X1 and Y1 , which have a similar composition to Samples A and B, respectively, but without the lactic acid. The inclusion of the lactic acid therefore improves the efficiency of release of nicotine from the substrate compared to a similar substrate which does not incorporate an acidic pH modifier. This effect was found to be particularly pronounced for homogenised plant materials including ginger as the non-tobacco plant material. For Sample A, there was an increase in the transfer rate of nicotine of over 60 percent compared to the nicotine transfer rate for Sample X1. For Sample B, there was an increase in the transfer rate of nicotine of over 75 percent compared to the nicotine transfer rate for Sample Y1.

[0289] Comparative Example 2 - homogenised plant materials with clove particles

[0290] The following homogenised plant materials were produced and incorporated into an aerosol-generating article as described above in relation to Figure 1. Samples D and E are according to the present invention whilst Samples X2 and Y2 each provides a comparative composition, which does not include an acidic pH modifier.

[0291]

[0292] The homogenised plant materials had the following pH values:

[0293] The inclusion of the acidic pH modifier was therefore found to decrease the pH of the sample by pH 0.7.

[0294] The following levels of nicotine were measured in the aerosols generated from Samples D, E, X2 and Y2: The table above shows the actual delivery of nicotine in the aerosol, in mg per article, as well as the transfer rate of nicotine, which corresponds to the percentage of nicotine present in the substrate that is transferred into the aerosol. As demonstrated by these results, the inclusion of lactic acid in the clove containing Samples D and E to reduce the pH values of the homogenised plant material resulted in a significant improvement in the transfer rate of nicotine from the homogenised plant material into the aerosol compared to the comparative samples X2 and Y2, which have a similar composition to Samples D and E, respectively, but without the lactic acid. The inclusion of the lactic acid therefore improves the efficiency of release of nicotine from the substrate compared to a similar substrate which does not incorporate an acidic pH modifier. For Sample D, there was an increase in the transfer rate of nicotine of over 25 percent compared to the nicotine transfer rate for Sample X2. For Sample E, there was an increase in the transfer rate of nicotine of over 5 percent compared to the nicotine transfer rate for Sample Y2.

[0295] Comparative Example 3 - homogenised plant materials with star anise particles

[0296] The following homogenised plant materials were produced and incorporated into an aerosol-generating article as described above in relation to Figure 1. Sample G is according to the present invention whilst Sample Y3 provides a comparative composition, which does not include an acidic pH modifier.

[0297] The homogenised plant materials had the following pH values: The inclusion of the acidic pH modifier was therefore found to significantly decrease the pH of the sample by more than 2.

[0298] The following levels of nicotine were measured in the aerosols generated from Samples G and Y3:

[0299] The table above shows the actual delivery of nicotine in the aerosol, in mg per article, as well as the transfer rate of nicotine, which corresponds to the percentage of nicotine present in the substrate that is transferred into the aerosol.

[0300] As demonstrated by these results, the inclusion of lactic acid in the star anise containing Sample G to reduce the pH value of the homogenised plant material resulted in a very significant improvement in the transfer rate of nicotine from the homogenised plant material into the aerosol compared to the comparative samples Y3, which has a similar composition to Sample G, but without the lactic acid. The inclusion of the lactic acid therefore improves the efficiency of release of nicotine from the substrate compared to a similar substrate which does not incorporate an acidic pH modifier. For Sample G, there was an increase in the transfer rate of nicotine of 10 percent compared to the nicotine transfer rate for Sample Y3.

[0301] The specific embodiments and examples described above illustrate, but do not limit, the invention. It is to be understood that other embodiments of the invention may be made and the specific embodiments and examples described herein are not exhaustive.

[0302] For the purpose of the present description and of the appended claims, except where otherwise indicated, all numbers expressing amounts, quantities, percentages, and so forth, are to be understood as being modified in all instances by the term "about". In this context, therefore, a number A is understood as A ± 10% of A. Within this context, a number A may be considered to include numerical values that are within general standard error for the measurement of the property that the number A modifies. The number A, in some instances as used in the appended claims, may deviate by the percentages enumerated above provided that the amount by which A deviates does not materially affect the basic and novel characteristic(s) of the claimed invention. Also, all ranges include the maximum and minimum points disclosed and include any intermediate ranges therein, which may or may not be specifically enumerated herein.

Claims

1. An aerosol-generating article comprising an aerosol-generating substrate comprising homogenized plant material containing: at least 20 percent by weight of non-tobacco vegetable matter on a dry weight basis; from 1 percent by weight to 3.5 percent by weight exogenous nicotine on a dry weight basis; at least 1 percent by weight of an acidic pH modifier on a dry weight basis; and at least 10 percent by weight of the aerosol forming agent on a dry weight basis.

2. An aerosol generating article according to claim 1, characterized in that the pH of the homogenized plant material is less than 5.

5.

3. An aerosol generating article according to claim 1 or 2, characterized in that the non-tobacco plant particles are selected from ginger particles, eucalyptus particles, clove particles, star anise particles, chamomile particles, verbena particles, tea particles, and combinations thereof.

4. An aerosol-generating article as defined in any preceding paragraph, in which the tobacco particles have a D90 value of less than 300 microns.

5. An aerosol-generating article according to any of the preceding claims, characterized in that the homogenized plant material additionally contains less than 5 percent by weight of tobacco particles on a dry weight basis.

6. An aerosol-generating article according to any of the preceding claims, characterized in that the homogenized plant material is substantially free of tobacco.

7. An aerosol generating article according to any one of the preceding claims, characterized in that the acidic pH modifier comprises one or more carboxylic acids.

8. An aerosol generating article according to claim 7, wherein the acidic pH modifier comprises at least one of lactic acid or levulinic acid.

9. An aerosol generating article according to any of the preceding claims, characterized in that the homogenized plant material also contains a cellulose-based reinforcing agent.

10. An aerosol-generating substrate according to claim 9, characterized in that the cellulose-based reinforcing agent contains cellulose fibers.

11. An aerosol generating article according to any of the preceding claims, wherein the homogenized plant material is present in the form of a molded sheet.

12. An aerosol-generating article according to any of the preceding claims, further comprising a susceptor element within the aerosol-generating substrate.

13. A rod for use as an aerosol generating substrate in an aerosol generating article comprising one or more sheets of homogenized plant material containing: at least 20 percent by weight of non-tobacco vegetable matter on a dry weight basis; from 1 percent by weight to 3.5 percent by weight exogenous nicotine on a dry weight basis; at least 1 percent by weight of an acidic pH modifier on a dry weight basis; and at least 10 percent by weight of the aerosol forming agent on a dry weight basis.

14. An aerosol generating system comprising an aerosol generating article according to any one of claims 1-12 and an electrically controlled aerosol generating device comprising a heating element configured to heat an aerosol generating substrate of the aerosol generating article.

15. A method for producing an aerosol-forming substrate for use in an aerosol-generating article according to any one of paragraphs 1-12, comprising the steps of: forming a suspension containing non-tobacco plant particles, exogenous nicotine, an aerosol forming agent, an acidic pH modifier and water, wherein the amount of the acidic pH modifier in the suspension is selected such that the pH of the suspension is less than 5.5; castings of the suspension in sheet form; and drying the leaf at a temperature of 80 to 160 degrees Celsius.