WO2018141461A1

WO2018141461A1 - Method for the production of homogenized tobacco material

Info

Publication number: WO2018141461A1
Application number: PCT/EP2017/083941
Authority: WO
Inventors: Corinne Deforel; Marine JARRIAULT; Johannes Petrus Maria Pijnenburg
Original assignee: Philip Morris Products S.A.
Priority date: 2017-01-31
Filing date: 2017-12-20
Publication date: 2018-08-09

Abstract

The present invention relates to a method of preparation of a slurry for the production of a homogenized tobacco material, the method comprising: • providing a tobacco powder blend; • providing a binder (4) and an aerosol-former (3); • forming (100) a cellulose pulp (6) from cellulose fibers (2) and water (1); • combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form (103) a slurry; and • cooling (104) the slurry to a temperature below about 10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes.

Description

METHOD FOR THE PRODUCTION OF HOMOGENIZED TOBACCO MATERIAL

This invention relates to a process for producing homogenized tobacco material. In particular, the invention relates to a process for producing homogenized tobacco material for use in an aerosol-generating article such as, for example, a cigarette or a "heat-not-burn" type tobacco containing product.

Today, in the manufacture of tobacco products, besides tobacco leaves, also homogenized tobacco material is used. This homogenized tobacco material is typically manufactured from parts of the tobacco plant that are less suited for the production of cut filler, like, for example, tobacco stems or tobacco dust. Typically, tobacco dust is created as a side product during the handling of the tobacco leaves during manufacture.

The most commonly used forms of homogenized tobacco material is reconstituted tobacco sheet and cast leaf. The process to form homogenized tobacco material sheets commonly comprises a step in which tobacco dust and a binder are mixed to form a slurry. The slurry is then used to create a tobacco web, for example by casting a viscous slurry onto a moving metal belt to produce so called cast leaf. Alternatively, a slurry with low viscosity and high water content can be used to create reconstituted tobacco in a process that resembles paper-making. Once prepared, homogenized tobacco webs may be cut in a similar fashion as whole leaf tobacco to produce tobacco cut filler suitable for cigarettes and other smoking articles. The function of the homogenized tobacco for use in conventional cigarettes is substantially limited to physical properties of tobacco, such as filling power, resistance to draw, tobacco rod firmness and burn characteristics. This homogenized tobacco is typically not designed to have taste impact. A process for making such homogenized tobacco is for example disclosed in European Patent EP 0565360.

In a "heat-not-burn" aerosol-generating article, an aerosol-forming substrate is heated to a relatively low temperature, in order to form an aerosol but prevent combustion of the tobacco material. Further, the tobacco present in the homogenized tobacco material is typically the only tobacco, or includes the majority of the tobacco, present in the homogenized tobacco material of such a "heat-not burn" aerosol-generating article. This means that the aerosol composition that is generated by such a "heat-not burn" aerosol-generating article is substantially only based on the homogenized tobacco material. Therefore it is important to have good control over the composition of the homogenized tobacco material, for the control for example, of the taste of the aerosol. The use of tobacco dust or leftovers from other tobacco productions for the production of homogenized tobacco material for aerosol-generating article is therefore less suitable because the exact composition of the tobacco dust is not known. The slurry used to create a tobacco web, for example by casting a viscous slurry onto a moving metal belt to produce a so called cast leaf, can be stored from the time it is made up to the time it is cast. This storage may for example allow the transportation of the slurry to the moving metal belt, the preservation of the slurry for the subsequent casting or can be performed for any other reason. In any case, the slurry always rests for a period of time, even when the slurry is immediately cast after it is made up, since a certain time is anyhow required for both positioning the slurry onto the moving metal belt and casting the same. However, the presence of a binder inside the slurry may change the characteristics of the slurry itself during this waiting or storage time. Due to the fact that some time has elapsed from the slurry preparation to the slurry casting, during this time interval one or more of the characteristics of the slurry may not remain constant, and consequently a sub-optimal slurry is present at casting.

There is therefore a need for a new method of preparing a homogenized tobacco material for the use in a heated aerosol-generating article of the "heat-not-burn" type that provides for a slurry which is adapted to be stored and least for a given amount of time, and it is still adapted to be cast in a tobacco web within the required quality specifications.

According to a first aspect, the invention relates to a method for the production of a homogenized tobacco material, the method comprising: providing a tobacco powder blend, providing a binder and an aerosol-former, forming a cellulose pulp from cellulose fibers and water, combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form a slurry. According to the invention, the slurry is cooled to a temperature below about 10 degrees Celsius and the slurry is kept at a temperature below about 10 degrees Celsius for a time period longer than or equal to 60 minutes.

Homogenized tobacco materials are formed by mixing several ingredients with water to obtain a slurry and then, for example by casting the slurry, by creating a continuous web of homogenized material on a support. It is desired that the resulting web of homogenized tobacco material has a good homogeneity even after a storing period.

An important parameter of the slurry is its viscosity, in particular at the time of casting or otherwise forming the continuous web of tobacco. Viscosity influences the tensile strength of the homogenized tobacco web and its uniformity. The density of the slurry, in particular before a step of casting the slurry to form a homogenized tobacco web, is important for determining the end quality of the web itself. A proper slurry density and homogeneity minimizes the number of defects and maximizes tensile strength of the web.

The slurry comprises a number of components to produce the homogenized tobacco web. These components influence the homogenized tobacco material properties. A first ingredient is a tobacco powder blend, which preferably contains the majority of the tobacco present in the slurry. The tobacco powder blend is the source of the majority of tobacco in the homogenized tobacco material and thus gives the flavor to the aerosol. A cellulose pulp containing cellulose fibers is added in order to increase the tensile strength of the tobacco material web, acting as a strengthening agent. A binder and an aerosol-former are added as well, in order to enhance the tensile properties of the homogenized sheet and promote the formation of aerosol.

However, when the slurry is stored for even a limited amount of time the binder may start to degrade and the viscosity of the slurry may decrease. The subsequent casting of the slurry may create defects in the cast layer, such as random variation in the thickness of the cast layer, because the viscosity of the slurry is not any more within the optimal range, due to the binder's degradation. Particularly, the degradation of the binder and the decrease in viscosity of the slurry become significant and can jeopardize the casting of the slurry when the storage period is significant, as for example equal or longer than 60 minutes. After this significant period of storage, the viscosity of the slurry rapidly decreases and can fall down even to a half of the original viscosity of the slurry.

According to the invention, the slurry is cooled to a temperature below about 10 degrees Celsius and the temperature of the slurry is kept below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes. Preferably, the cooling takes place before the casting and after the slurry preparation, that is, after all ingredients making up the slurry have been introduced and mixed. Cooling the slurry to a temperature below about 10 degrees Celsius and keeping the slurry to a temperature below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes may prevent or delay the binder's degradation so that the viscosity of the slurry does not significantly decrease or anyhow may not substantially change.

The term "significant" or "significantly" referred to the decrease of the viscosity of the slurry is used throughout the specification to encompass a decrease in slurry viscosity of more than about 25 percent.

The term "homogenized tobacco material" is used throughout the specification to encompass any tobacco material formed by the agglomeration of particles of tobacco material. Sheets or webs of homogenized tobacco are formed in the present invention by agglomerating particulate tobacco obtained by grinding or otherwise powdering of one or both of tobacco leaf lamina and tobacco leaf stems. In addition, homogenized tobacco material may comprise a minor quantity of one or more of tobacco dust, tobacco fines, and other particulate tobacco by-products formed during the treating, handling and shipping of tobacco.

In the present invention, the slurry is formed by tobacco lamina and stem of different tobacco types, which are properly blended. With the term "tobacco type" one of the different varieties of tobacco is meant. With respect to the present invention, these different tobacco types are distinguished in three main groups of bright tobacco, dark tobacco and aromatic tobacco. The distinction between these three groups is based on the curing process the tobacco undergoes before it is further processed in a tobacco product.

Bright tobaccos are tobaccos with a generally large, light coloured leaves. Throughout the specification, the term "bright tobacco" is used for tobaccos that have been flue cured. Examples for bright tobaccos are Chinese Flue-Cured, Flue-Cured Brazil, US Flue-Cured such as Virginia tobacco, Indian Flue-Cured, Flue-Cured from Tanzania or other African Flue Cured. Bright tobacco is characterized by a high sugar to nitrogen ratio. From a sensorial perspective, bright tobacco is a tobacco type which, after curing, is associated with a spicy and lively sensation. According to the invention, bright tobaccos are tobaccos with a content of reducing sugars of between about 2.5 percent and about 20 percent of dry weight base of the leaf and a total ammonia content of less than about 0.12 percent of dry weight base of the leaf. Reducing sugars comprise for example glucose or fructose. Total ammonia comprises for example ammonia and ammonia salts.

Dark tobaccos are tobaccos with a generally large, dark coloured leaves. Throughout the specification, the term "dark tobacco" is used for tobaccos that have been air cured. Additionally, dark tobaccos may be fermented. Tobaccos that are used mainly for chewing, snuff, cigar, and pipe blends are also included in this category. From a sensorial perspective, dark tobacco is a tobacco type which, after curing, is associated with a smoky, dark cigar type sensation. Dark tobacco is characterized by a low sugar to nitrogen ratio. Examples for dark tobacco are Burley Malawi or other African Burley, Dark Cured Brazil Galpao, Sun Cured or Air Cured Indonesian Kasturi. According to the invention, dark tobaccos are tobaccos with a content of reducing sugars of less than about 5 percent of dry weight base of the leaf and a total ammonia content of up to about 0.5 percent of dry weight base of the leaf.

Aromatic tobaccos are tobaccos that often have small, light coloured leaves. Throughout the specification, the term "aromatic tobacco" is used for other tobaccos that have a high aromatic content, for example a high content of essential oils. From a sensorial perspective, aromatic tobacco is a tobacco type which, after curing, is associated with spicy and aromatic sensation. Example for aromatic tobaccos are Greek Oriental, Oriental Turkey, semi-oriental tobacco but also Fire Cured, US Burley, such as Perique, Rustica, US Burley or Meriland.

Additionally, a blend may comprise so called filler tobaccos. Filler tobacco is not a specific tobacco type, but it includes tobacco types which are mostly used to complement the other tobacco types used in the blend and do not bring a specific characteristic aroma direction to the final product. Examples for filler tobaccos are stems, midrib or stalks of other tobacco types. A specific example may be flue cured stems of Flue Cured Brazil lower stalk.

Within each type of tobaccos, the tobacco leaves are further graded for example with respect to origin, position in the plant, colour, surface texture, size and shape. These and other characteristics of the tobacco leaves are used to form a tobacco blend. A blend of tobacco is a mixture of tobaccos belonging to the same or different types such that the tobacco blend has an agglomerated specific characteristic. This characteristic can be for example a unique taste or a specific aerosol chemical composition, when heated or burnt. A blend comprises specific tobacco types and grades in a given proportion one with respect to the other.

According to the invention, different grades within the same tobacco type may be cross- blended to reduce the variability of each blend component. According to the invention, the different tobacco grades are selected in order to realize a desired blend having specific predetermined characteristics. For example, the blend may have a target value of the reducing sugars, total ammonia and total alkaloids per dry weight base of the homogenized tobacco material. Total alkaloids are for example nicotine and the minor alkaloids including nornicotine, anatabine, anabasine and myosmine.

The various tobacco types are in generally available in lamina and stems. In order to produce a slurry for a homogenized tobacco material, the selected tobacco types have to be ground in order to achieve a proper tobacco size, for example a tobacco size which is suitable for forming a slurry.

A cellulose pulp includes water and cellulose fibres. Tobacco itself includes naturally cellulose fibres. The cellulose fibres of the pulp are added to the slurry in addition to those cellulose fibres contained in the tobacco blend and are called in the following "added" cellulose fibres. Cellulose fibres for including in a slurry for homogenized tobacco material are known in the art and include, but are not limited to: soft-wood fibres, hard wood fibres, jute fibres, flax fibres, tobacco fibres and combination thereof. In addition to pulping, the added cellulose fibres might be subjected to suitable processes such as refining, mechanical pulping, chemical pulping, bleaching, sulphate pulping and combination thereof. Fibres particles may include tobacco stem materials, stalks or other tobacco plant material. Preferably, cellulose-based fibres such as wood fibres comprise a low lignin content. Fibres particles may be selected based on the desire to produce a sufficient tensile strength. Alternatively fibres, such as vegetable fibres, may be used either with the above fibres or in the alternative, including hemp and bamboo.

The addition of a binder, such as any of the gums or pectins described herein, facilitates that the tobacco powder remains substantially dispersed throughout the homogenized tobacco web. For a descriptive review of gums, see Gums And Stabilizers For The Food Industry, IRL Press (G.O. Phillip et al. eds. 1988); Whistler, Industrial Gums: Polysaccharides And Their Derivatives, Academic Press (2d ed. 1973); and Lawrence, Natural Gums For Edible Purposes, Noyes Data Corp. (1976).

Although any binder may be employed, preferred binders are guar gums, such as hydroxyethyl guar and hydroxypropyl guar; natural pectins, such as fruit, citrus or tobacco pectins; locust bean gums, such as hydroxyethyl and hydroxypropyl locust bean gum; alginate; starches, such as modified or derivitized starches; celluloses, such as methyl, ethyl, ethylhydroxymethyl and carboxymethyl cellulose; tamarind gum; dextran; pullalon; konjac flour; xanthan gum and the like. The particularly preferred binder for use in the present invention is guar.

The slurry also comprises an aerosol former. Aerosol formers may include Glycerin, Triethyl citrate, Propylene carbonate, Ethyl laurate, Triacetin, meso-Erythritol, a Diacetin mixture, a Diethyl suberate, and Propylene Glycol. Functionally, the aerosol former provides mechanism that allows it to volatilize and convey nicotine and/or flavouring in an aerosol when heated above the specific volatilization temperature of the aerosol former. The aerosol former may also have humectant type properties that help maintain a desirable level of moisture in an aerosol forming substrate when the substrate is composed of a tobacco-based product including tobacco particle.

Preferably, the slurry contain an amount of asparaginase lower than or equal to about 0.001 percent per weight on dry weight basis of the slurry. More preferably, the slurry does not contain asparaginase. Thus, preferably, in the slurry there is preferably either a low level of asparaginase (lower than about 0.001 percent in dry weight basis) or absence of asparaginase.

Slurry for the production homogenized tobacco material may comprise other ingredients or additives in addition to the above mentioned list. For example, the slurry may include, but not limited to, tobacco fibers, plasticizers, flavourants, fillers, aqueous and nonaqueous solvents, and combinations thereof. Further, in order to reach a certain viscosity and moisture optimal for casting the web of homogenized tobacco material, water may be added to the slurry. The slurry is mixed in order to render it as homogeneous as possible.

The slurry is formed combining all the above mentioned elements together: preferably a suspension of binder in aerosol-former is made, which is then added to the pulp, and the tobacco powder blend. In the slurry formation, the binder enters in contact with water due to the fact that pulp contains water. When in contact with water, an aging process starts, where some gel may form and the viscosity of the slurry changes continuously. When the slurry is formed, the aging process of the binder continues and the viscosity of the slurry starts to decrease. As an example, the viscosity of the slurry can decrease up to 50 percent of the initial viscosity of the slurry in about 240 minutes.

According to the invention, cooling the slurry already formed to a temperature below about 10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes may prevent the aging process of the binder to continue significantly, in this way the cooling may prevent the viscosity of the slurry to drop down to values unsuitable for obtaining a web of homogenized tobacco material having proper homogeneity. The binder in the slurry takes more time to degrade when the slurry is cooled at the above indicated temperature than when the slurry is maintained at room temperature. Therefore, there is more time for properly storing the slurry before its casting without negatively affecting the quality and the properties of the resulting homogenized tobacco material.

Preferably, the already formed slurry is cooled to a temperature comprised between the freezing temperature of the slurry and 10 degrees Celsius. More preferably, the already formed slurry is cooled to a temperature comprised between about 10 degrees Celsius and about 2 degrees Celsius, more preferably between about 10 degrees Celsius and about 3 degrees Celsius, even more preferably between about 10 degrees Celsius and about 5 degree Celsius, even more preferably between about 10 degrees Celsius and about 9 degree Celsius or between about 9 degrees Celsius and about 7 degree Celsius.

Preferably, the temperature of the slurry during the cooling and keeping phase may remain always constant, that is, the temperature of the slurry may remain substantially always the same. Alternatively, the temperature of the slurry might fluctuate or vary during the cooling and keeping steps, although it remains always below 10 degrees Celsius. For example the temperature of the slurry may remain at the same

for the whole time period, or it may fluctuate within the time period. Further, within the at least 60 minutes time interval, the temperature of the slurry may be constant for some time sub-intervals and may vary in other time sub-intervals. Any suitable device apt to decrease the temperature, such as a refrigerating machine acting on a container or a vessel containing the slurry or such as water jacket wall surrounding the vessel containing the slurry, can perform the cooling of the slurry. Preferably, the temperature of the slurry is monitored during the entire period the slurry is kept at the preferred temperature. Preferably, the temperature of the slurry is monitored with appropriate sensors. Preferably, the sensor signals are used with a feedback loop for online signal processing and control to maintain the temperature of the slurry within the preferred range.

Further, the temperature of the slurry below about 10 degrees Celsius is kept for at least about 60 minutes. Preferably, the temperature of the slurry is kept lower than about 10 degrees Celsius for a time period comprised between about 60 minutes and about 2400 minutes. More preferably, the temperature of the slurry is kept lower than about 10 degrees Celsius for a time period comprised between about 60 minutes and about 2100 minutes. Even more preferably, the temperature of the slurry is kept lower than about 10 degrees Celsius for a time period comprised between about 200 minutes and about 2000 minutes.

Thanks to the slurry cooling to a temperature below about 10 degrees Celsius, it is possible to increase from about 4 hours to about 36 hours the storage time of slurry between the last process step of slurry preparation and the first step of cast leaf processing. In this way, manufacturability and flexibility in process management to adequately process slurry within specifications may be strongly improved. Further, process capability towards a stable manufacturing process and a more consistent product may be enhanced as well.

Preferably, the method of the invention further comprises the step of storing the slurry while cooling.

Storing the slurry while cooling can allow, for example, to rest the slurry before casting the same without any degradation of the binder and thus without a significant decrease of the viscosity of the slurry. In this way, the preparation of the slurry may take place in given premises, while the casting may take place in a different production site, without affecting the quality of the cast leaf.

Preferably, the method of the invention further comprises the step of storing the slurry while keeping the slurry at a temperature below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes.

Therefore, the step of storing the slurry can be performed while cooling the slurry at a temperature below about 10 degrees Celsius or while keeping the slurry at a temperature below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes or during both. Preferably, the method of the invention further comprises the step of transporting the slurry while cooling.

The transportation of the slurry while cooling can allow, for example, transferring the slurry in an area of the production plant, different from the area wherein the slurry is manufactured, for a subsequent storing or for casting the slurry while preventing the viscosity of the slurry to significantly decrease. Therefore, the transportation phase can be relatively long, because cooling the slurry while transporting may avoid the side effects of the binder's degradation.

Preferably, the method of the invention further comprises the step of transporting the slurry while keeping the slurry at a temperature below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes.

Therefore, the step of transporting the slurry can be performed while cooling the slurry at a temperature below about 10 degrees Celsius or while keeping the slurry at a temperature below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes or during both.

Preferably, the step of providing a binder and an aerosol former includes: suspending a binder in an aerosol-former to form a suspension; and the step of combining the binder, the aerosol- former, the cellulose pulp and the tobacco powder blend to form a slurry comprises combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form a slurry.

The formation of a suspension of the binder in the aerosol former may further reduce the "aging" of the binder and its consequent degradation when it comes into contact with water. The molecules of aerosol-former encircle the binder so that the contact of the binder with water is delayed.

Preferably, the step of cooling the slurry already formed to a temperature below about

10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius is performed for a time period shorter than about 2400 minutes.

It has been found that the cooling of the slurry prevents variations, in particular drops, in the slurry viscosity up to a period of 36 hours. Within this time period, if cooling takes place, the formation of a homogenized tobacco web without defects is possible also after storing the slurry for a day.

Preferably, in the method of the invention, the binder is guar. More preferably, the guar is guar gums. Preferably, the step of combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry comprises: combining the binder, the aerosol- former, the cellulose pulp and the tobacco powder blend in such a proportion that the cellulose fibers is in an amount comprised between about 1 percent and about 4 percent in dry weight basis of the slurry.

The pulp is formed by adding together the cellulose fibres and water. The water is preferably added in two separate steps. Firstly the pulp is produced mixing together the cellulose fibres and a first amount of water. This concentrated pulp is then preferably stored and diluted when it is to be added to the other ingredients forming the slurry. In this way the amount of water to be introduced in the slurry can be easily controlled. Preferably, the cellulose fibers are in an amount comprised between about 2 percent and about 3 percent in dry weight basis of the slurry.

Preferably, combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry comprises: combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend in such a proportion that the binder is in an amount comprised between about 1 percent and about 4 percent in dry weight basis of the slurry.

In slurry for the preparation of homogenized tobacco material according to the prior art, the amount of binder added to it generally exceeds 5 percent in dry weight basis of the total amount of slurry. In the present method of the invention, only between about 1 percent and about 4 percent of binder in dry weight basis of the slurry is preferably added to the slurry, reducing the total costs of the realization of the slurry, being the binder generally relatively expensive. Preferably, the binder is in an amount comprised between about 2 percent and about 3 percent in dry weight basis of the slurry.

Advantageously, said step of combining the binder, the aerosol-former, said cellulose pulp and said tobacco powder blend to form said slurry comprises: combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend in such a proportion that the aerosol-former is in an amount comprised between about 5 percent and about 30 percent in dry weight basis of the slurry.

The slurry of the invention contains a relatively large amount of aerosol -former, when compared to the slurry for the production of homogenized tobacco material according to the prior art. The relatively high amount of aerosol-former is preferably used to make a suspension with the binder so that substantially all binder is surrounded by aerosol-former molecules, in order to keep the binder away from water as much as possible when combined in the slurry. In a preferred embodiment, the method of the invention further comprises: combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form said slurry in a tank; and cooling said tank in order to keep a temperature of said slurry below about 10 degrees Celsius.

The cooling of the tank where the slurry is formed for keeping the slurry at a temperature below about 10 degrees Celsius can allow avoiding the immediate transfer of the slurry in a dedicated storage container for starting the cooling step, in order to prevent the viscosity to change. The storage of the slurry is therefore simplified.

Preferably, the cooling of the tank is made for keeping the slurry at a temperature below about 10 degrees Celsius for a time period equal or longer than 60 minutes.

The tank where the slurry is formed preferably comprises a mantel, which is cooled in order to keep the slurry at a temperature below about 10 degrees Celsius. The portions of slurry within the tank in contact with the mantel decrease their temperature by heat exchange.

Alternatively or in addition, the dedicated storage container where the slurry can be transferred for its storage or for its transportation is cooled in order to keep the slurry at a temperature below about 10 degrees Celsius.

Preferably, the cooling of the dedicated storage container is made for keeping the slurry at a temperature below about 10 degrees Celsius for a time period equal or longer than 60 minutes.

Preferably, the method of the invention further comprises: combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry in a tank; and mixing the slurry.

Due to the mixing in the slurry formation tank, the temperature becomes uniform as the portions of slurry in contact to the cooled mantel of the tank are moved towards the interior of the tank, where the temperature is higher. Mixing therefore allows a temperature homogenization of the slurry. Moreover, mixing allows homogeneously combining all ingredients of the slurry and creating a uniform mixture of all of them. This also means that the slurry present in the tank reaches the same viscosity.

More preferably, the slurry mixing is performed in a tank defining a central region and an outer mantel, the mixing being performed by means of a spiral mixer adapted to remove slurry from the outer mantel and to direct it towards the central region or to remove slurry from the central region and direct it towards the outer mantel, so as to uniformly mix the slurry. The slurry should be as homogeneous as possible so that also its viscosity is as uniform as possible and close to a target value. In order to obtain a uniform viscosity, the entire amount of slurry is preferably mixed. Accordingly, non-moving portions of slurry are minimized. Otherwise, these non-moving portions of slurry may attach to the side walls of the tank. For this purpose, the mixer is designed in such a way that the slurry is continuously moved from the external walls or mantel towards the center of the mixer or vice-versa. In this way, all the bulk of slurry continuously moves and there are no portions of slurry mixed more (or less) than others. This may greatly improve the homogeneity of the viscosity of the slurry and with that the physical properties of the cast tobacco web, including the machinability of the cast tobacco web.

Preferably, the method of the invention further comprises one or more of the following steps: monitoring a viscosity of the slurry; monitoring a temperature of the slurry.

The formation of the slurry is a delicate process which determines the quality of the end product. Several parameters may be controlled to minimize the risk of a rejection of the homogenized tobacco sheet obtained with the slurry prepared according to the invention. For example, due to defects or a low tensile strength out of specification material could be formed. In particular, these process parameters are among other parameters, the temperature and the viscosity of the slurry. It is known that the viscosity is indeed a function of (among others) the temperature. Therefore, preferably, at least one of the viscosity and the temperature of the slurry is monitored with appropriate sensors. Preferably, the sensor signals are used with a feedback loop for online signal processing and control to maintain the parameters within a set of predetermined ranges.

Preferably, the method of the invention further comprises: casting the slurry so as to form a continuous homogenized tobacco web; and cooling the slurry during casting.

A web of homogenized tobacco material is preferably formed by a casting process of the type generally comprising casting a slurry prepared including the blend of tobacco powder above described on a support surface. Preferably, the cast sheet is then dried to form a sheet of homogenized tobacco material and it is then removed from the support surface.

Preferably, said step of casting the slurry so as to form a continuous homogenized tobacco web is performed by casting the slurry onto a movable support to form a continuous web of homogenized tobacco material. The casting may take place by means of a casting blade. A transporting support moves along a longitudinal or transport direction in order to remove the slurry from the cast apparatus. The support may include for example a stainless steel movable belt. The cast apparatus is preferably so designed and construed to form a cast web of slurry which has a substantially uniform thickness onto the movable support.

Preferably, during the casting process, namely up to the formation of a cast web onto the movable support, the slurry is cooled, so that the viscosity of the slurry does not drop down during the casting process. However, in the casting box, it is possible that the temperature of the slurry rises above 10 degrees Celsius, due to the friction the slurry experiences therein.

An important parameter of the slurry is its viscosity, in particular at the time of casting or otherwise forming the continuous web of tobacco. Viscosity influences the tensile strength of the homogenized tobacco web and its uniformity. The density of the slurry, in particular before and during a step of casting the slurry to form a homogenized tobacco web, is important for determining the end quality of the web itself. A proper slurry density and homogeneity minimizes the number of defects and maximizes tensile strength of the web. Therefore, the cooling of the slurry may prevent the viscosity of the slurry to significantly decrease during the casting process so allowing to minimize the number of defects in the homogenized tobacco web.

Preferably, the method of production of homogenized tobacco material includes a step of slurry formation including: combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder and mixing the same. Preferably, the formation and mixing of the slurry is performed at room temperature.

It has been observed that to obtain a slurry with a good tensile strength and relatively few defects, the temperature of the slurry, which in turn is connected to the viscosity of the slurry, is a relevant parameter. Due to the fact that the slurry needs to be constantly mixed to render it homogeneous and uniform, the friction caused by the mixer may increase the temperature of the slurry. It is preferred to keep the temperature under control within a suitable range between about 10 degrees Celsius and about 40 degrees Celsius, preferably between about 15 degrees Celsius and about 25 degrees Celsius. Preferably, in order to keep the slurry temperature within this range, the slurry tank is cooled. The tank preferably comprises a mantel which is cooled.

Preferably, the step of cooling the slurry to a temperature below about 10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes is performed after the above described step of forming and mixing the slurry. Preferably, the slurry is cast to form a homogenized tobacco sheet. Preferably, the temperature of the slurry below about 10 degrees Celsius is kept till the slurry reaches the casting step. More preferably, the temperature of the slurry below about 10 degrees Celsius is kept till the slurry reaches a casting box.

Preferably, after casting, the homogenized tobacco sheet is dried. Preferably, the drying is performed at a temperature above room temperature. Preferably, the drying is performed at a temperature above about 30 degrees Celsius. Preferably, the drying is performed at a temperature above about 40 degrees Celsius. Preferably, the drying is performed at a temperature above about 50 degrees Celsius. Preferably, the drying is performed at a temperature up to about 60 degrees Celsius. Preferably, the drying is performed at a temperature above about 70 degrees Celsius. Preferably, the drying is performed at a temperature above about 80 degrees Celsius.

Preferably, the temperature difference between the temperature at which the slurry is cooled for a time period longer than or equal to about 60 minutes and the temperature at which the slurry is formed and mixed is at least of about 1 degree Celsius. Preferably, the temperature difference is at least of about 2 degrees Celsius. Preferably, the temperature difference is at least of about 5 degrees Celsius. Preferably, the temperature difference is at least of about 10 degrees Celsius.

Preferably, the temperature difference between the temperature at which the slurry is cooled for a time period longer than or equal to about 60 minutes and the temperature at which the homogenized tobacco sheet is dried is at least of about 20 degrees Celsius. Preferably, the temperature difference is at least of about 30 degrees Celsius. Preferably, the temperature difference is at least of about 40 degrees Celsius. Preferably, the temperature difference is at least of about 50 degrees Celsius. Preferably, the temperature difference is at least of about 60 degrees Celsius. Preferably, the temperature difference is at least of about 70 degrees Celsius.

Preferably, the moisture of the cast tobacco material web at casting is between about 60 percent and about 80 percent in weight of the total weight of the cast tobacco web. Preferably, the method for production of a homogenized tobacco material comprises the step of drying said cast sheet, winding said cast sheet, wherein the moisture of said cast sheet at winding is between about 7 percent and about 15 percent of the total weight of the tobacco material web. Preferably, the moisture of said homogenized tobacco web at winding is between about 8 percent and about 12 percent of the total weight of the homogenized tobacco web.

In an embodiment, the step of forming a pulp with cellulose fibers and water comprises: reducing the fiber length of the cellulose fibers by means of grinding in order to obtain an mean fiber length of said cellulose fibers comprised between about 0.2 millimeters and about 4 millimeters.

According to the invention, cellulose fibres are introduced in the slurry, in addition to the cellulose fibres which are naturally present in the tobacco. The introduction of cellulose fibres to the fibres present in the tobacco in the slurry increases the tensile strength of the tobacco material web, acting as a strengthening agent. Therefore, adding cellulose fibres may increase the resilience of the homogenized tobacco material web. This supports a smooth manufacturing process and subsequent handling of the homogenized tobacco material during the manufacture of aerosol generating articles. In turn, this can lead to an increase in production efficiency, cost efficiency, reproducibility and production speed of the manufacture of the aerosol- generating articles and other smoking articles.

One relevant factor in the added cellulose fibres is the cellulose fibre length. Where the cellulose fibres are too short, the fibres would not contribute efficiently to the tensile strength of the resulting homogenized tobacco material. Where the cellulose fibres are too long, the cellulose fibres would impact the homogeneity in the slurry and in turn may create inhomogeneties and other defects in the homogenized tobacco material, in particular for thin homogenized tobacco material, for example with a homogenized tobacco material with a thickness of several hundreds of micrometres. According to the invention, the size of added cellulose fibres in a slurry comprising tobacco powder having a mean size between about 0.03 millimetres and about 0.12 millimetres and a quantity of binder between about 1 percent and about 3 percent in dry weight of the slurry, is advantageously between about 0.2 millimetres and about 4 millimetres, preferably between about 1 millimetres and about 3 millimetres. Further, according to the invention, the amount of the added cellulose fibres is comprised between about 1 percent and about 3 percent in dry weight of the total weight of the slurry. These values of the ingredients of the slurry have shown to improved tensile strength while maintaining a high level of homogeneity of the homogenized tobacco material compared to homogenized tobacco material that only relies on binder to address tensile strength of the homogeneous tobacco web. At the same time, added cellulose fibres having a mean length of between about 0.2 millimetres and about 4 millimetres do not significantly inhibit the release of substances from the fine ground tobacco powder when the homogenized tobacco material is used as an aerosol generating substrate of an aerosol generating article. In the present specification, the fibre "size" means the fibre length, that is, the fibre length is the dominant dimension of the fibre. Thus, mean fibre size has the meaning of mean fibre size length. The mean fiber length is the mean fiber length per a given number of fibers, excluding fibers having a length below about 200 microns or above about 10.000 microns and excluding fibres having a width below about 5 microns or above about 75 microns. According to the invention, a relatively fast and reliable manufacturing process of homogenized tobacco web can be obtained, as well as a substrate for a highly reproducible aerosol.

Preferably, the step of mixing binder and aerosol-former to form a suspension comprises:

adding a first amount of binder to a first amount of aerosol-former;

mixing the first amount of binder and the first amount of aerosol-former; and adding a second amount of aerosol-former.

Binders are commonly relatively sticky substances that are prone to leave residues on the pipes on or supports in which are transported. The presence of a first pre-mixing step according to the method of the invention, in which binder and aerosol-former form a suspension, implies that a relatively large amount of binder is flowing in a process line to combine with the aerosol-former. The process line may thus often require cleaning, which causes an interruption of the production process of the homogenized tobacco material. The cleaning causes waste, requires time and reduced productivity. In order to minimize the cleaning intervention, some aerosol-former is used to "flush" the process line after the binder has been already transported. This way, advantageously, the process line may be efficiently cleaned during the production by removing fresh binder residues. Thus the step of adding a second amount of aerosol-former may comprise the step of flushing a process line with said second amount of aerosol-former so as to clean the process line.

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

Figure 1 is a flow diagram of an embodiment of the method of preparation of a slurry for the production of a homogenized tobacco material;

- Figure 2 is a schematic view of an apparatus for the production of a suspension of binder in aerosol-former;

Figure 3 is a schematic view of an apparatus for the production of cellulose pulp; Figure 4 is a schematic view of an apparatus for the preparation of slurry; and

Figure 5 is a schematic view of an apparatus for casting and drying a homogenized tobacco sheet.

With reference to figure 1 , a method to realize a slurry for the production of a homogenized tobacco material according to the invention is schematically depicted.

The method of realize the slurry includes a step of preparing a cellulose pulp 100. The pulp preparation step 100 preferably comprises mixing water 1 and cellulose fibers 2 in a concentrated form, optionally storing the pulp so obtained and then diluting the pulp before forming the slurry. The cellulose fibers, for example in boards or bags, are loaded in a pulper and then liquefied with water. The resulting water - cellulose solution may be stored at different densities, however preferably the pulp which is the result of the step 100 is "concentrate". Preferably, "concentrate" means that between about 3 and about 5 percent of cellulose fibers are included in the water/cellulose pulp. Preferred cellulose fibers are soft wood fibers. Preferably, the total amount of cellulose fibers in the slurry in dry weight, in addition to the cellulose fibres present in the tobacco blend added to the slurry, is between about 1 percent and about 4 percent, preferably, between about 2 percent and about 3 percent in dry weight of the homogenized tobacco material.

Preferably, the step of mixing of water and cellulose fibers lasts between about 20 and about 60 minutes, advantageously at a temperature comprised between about 15 degrees Celsius and about 40 degrees Celsius.

The storage time, if storage of the pulp is performed, may preferably vary between about 0.1 and about 7 days.

Advantageously, water dilution takes place after the step of storing of the concentrated pulp. Water is added to the concentrated pulp in such an amount that the cellulose fibers are less than about 1 percent of the total weight of the pulp. For example, a dilution of a factor comprised between about 3 and about 20 can take place. Further, an additional step of mixing may take place, which comprises mixing the concentrated pulp and the added water. The additional mixing step preferably lasts between about 120 minutes and about 180 minutes at a temperature between about 15 degrees Celsius and about 40 degrees Celsius, more preferably, at a temperature of between about 18 degrees Celsius and about 25 degrees Celsius.

An apparatus 200 to perform the method step 100 of the pulp formation is depicted in figure 2. Figure 2 schematically depicts a cellulose fibre feeding and preparation line 200 comprising a feeding system 201 , preferably adapted to handle cellulose fibres 2 in bulk form, such as board/sheets or fluffed fibers, and a pulper 202. The feeding system 201 is adapted to direct the cellulose fibres to the pulper 202, which is in turn adapted to disperse the received fibres uniformly.

The pulper 202 includes a temperature control unit 201 a so that the temperature in the pulper is kept within a given temperature interval, and a rotational speed control unit 201 b, so that the speed of an impeller (not shown) present in the pulper 202 is controlled and kept preferably comprised between about 5 rpm and about 35 rpm. The cellulose fibre feeding and preparation line 200 further comprises a water line 204 adapted to introduce water in the pulper 202. A flow rate controller 205 to control the flow rate of water introduced in pulper 202 is preferably added in the water line 204.

The cellulose fibre feeding and preparation line 200 may also further comprise a fibre refiner system 203 to treat and fibrillate fibres, so that long fibres and nested fibres are removed, and a uniform fibre distribution is obtained.

Downstream the fibre refiner system 203, the cellulose fibre feeding and preparation line 200 may comprise a cellulose buffer tank 207 connected to the fibre refiner system 203 to store the high consistency fibre solution coming out of the system 203.

At the end of cellulose fibre feeding and preparation line 200, a cellulose dilution tank

208 in which pulp is diluted is preferably present and connected to cellulose buffer tank 207. The cellulose dilution tank 208 is adapted to batch out cellulose fibres of right consistency for subsequent slurry mixing. Water for dilution is introduced in tank 208 via a second water line 210.

Referring back to figure 1 , the method to realize the slurry according to the invention also includes a step of suspension preparation 101. The suspension preparation step 101 preferably comprises mixing an aerosol-former 3 and a binder 4 in order to form a suspension. Preferably, the aerosol - former 3 comprises glycerol and the binder 4 comprises guar, more preferably the binder 4 comprises gums guar. The suspension step 101 of binder in aerosol- former includes the steps of loading the aerosol-former and the binder in a container and mixing the two. Preferably, the resulting suspension is then stored before being introduced in the slurry. Preferably, the glycerol is added to the guar in two steps, a first amount of glycerol is mixed with guar and a second amount of glycerol is then injected in the transport pipes, so that glycerol is used to clean the processing line, avoiding hard-to-clean points within the line.

A slurry preparation line 300 adapted to perform the suspension step 101 of binder in aerosol-former of the invention is depicted in figure 3.

The slurry preparation line 300 includes an aerosol-former, such as glycerol, bulk tank 301 and a pipe transfer system 302 having a mass flow control system 303 adapted to transfer the aerosol-former 3 from the tank 301 and to control its flow rate. Further, the slurry preparation line 300 comprises a binder handling station 304 and a pneumatic transport and dosing system 305 to transport and weight the binder 4 received at the station 304.

Aerosol-former and binder from tank 301 and handling station 304 are transported to a mixing tank, or more than a mixing tank, 306, part of the slurry preparation line 300, designed to mix binder and aerosol-former uniformly. All tanks and transfer pipes for cellulose fiber, guar and glycerol are preferably designed to be as optimally short as possible to reduce transfer time, minimize waste, avoid cross contamination and facilitate ease of cleaning. Further, preferably, the transfer pipes for cellulose fiber, guar and glycerol are as straight as possible, to allow a swift and uninterrupted flow. In particular for the suspension of binder in the aerosol-former, turns in the transfer pipe could otherwise result in areas of low flow rate or even standstill, which in turn can be areas where gelling can occur and with that potentially blockages within the transfer pipes. As mentioned before, those blockages can lead to the need for cleaning and standstill of the entire manufacturing process.

Further, the method of the invention includes a step of a tobacco powder blend formation 102. Tobacco has been blended and grinded in a blending and grinding line, not depicted in the drawing, in order to obtain a tobacco powder blend preferably to a mean size between about 0.03 millimetres and about 0.12 millimetres.

The method to form a slurry according to the invention further comprises a step of slurry formation 103, where the suspension 5 of the binder in the aerosol-former obtained in step 101 , the pulp 6 obtained in step 100 and a tobacco powder 7 obtained in step 102 are combined together.

Preferably, the step of slurry formation 103 comprises first a step of introduction in a tank of the suspension of binder in aerosol-former 5 and of the cellulose pulp 6. Afterwards, the tobacco powder 7 is introduced as well. Preferably, the suspension 5, the pulp 6 and the tobacco powder 7 are suitably dosed in order to control the amount of each of them introduced in the tank. The slurry is prepared according to specific proportion among its ingredients. Preferably also water 8 is added.

Preferably, the step of slurry formation 103 further comprises a mixing step, where all the slurry ingredients are mixed together for a fixed amount of time. In a further step of the method according to the invention, the slurry is then transferred to a following cooling step 104, casting step 105 and drying step 106.

An apparatus 400 for the slurry formation adapted to realize step 103 of the method of the invention is schematically depicted in figure 4. Apparatus 400 includes a mixing tank 401 where cellulose pulp 6 and suspension 5 of binder in aerosol-former are introduced. Further, tobacco powder 7 from the blending and grinding line is fine-ground and dosed into the mixing tank 401 in specified quantity to prepare the slurry.

For example, the tobacco powder 7 may be contained in a tobacco fine powder buffer storage silo to ensure continuous upstream powder operation and meeting demand of slurry mixing process. Tobacco powder is transferred to the mixing tank 401 preferably by means of a pneumatic transfer system (not shown).

The apparatus 400 further comprises preferably a powder dosing system (also not shown) to dose required amount of the slurry's ingredients. For example, the tobacco powder may be weighed by a scale (not shown) or weighing belt (not shown) for precise dosing. The mixing tank 401 is specially designed to mix the dry and liquid ingredients to form a homogenous slurry.

The slurry mixing tank comprises a cooler 403, such as water jacket wall to allow water cooling on the external walls of the mixing tank 401. Alternatively, the cooler 403 can be a refrigeration machine acting on the external walls of the mixing tank 401. The slurry mixing tank 401 is equipped with one or more temperature sensors 404. The temperature sensors 404 may comprise temperature probes acting in the slurry for sensing the actual temperature of the slurry. The temperature probes act on different portions of the slurry for ensuring a distributed measurement of the temperatures within the slurry. The temperature probes are electrically connected to a control unit 405 that compares the detected temperature with a threshold temperature value. The control unit 405 is further electrically connected to the cooler 403 for increasing its cooling power in case the detected temperature is below the threshold temperature value and for decreasing its cooling power in case the detected temperature is above the threshold temperature value.

The slurry mixing tank 401 is further equipped with one or more sensors such as level sensors and sampling port for control and monitoring purpose. Mixing tank 401 has an impeller 402 adapted to ensure uniform mixing of the slurry, in particular adapted to transfer slurry form the external walls of the tank to the internal part of the tank or vice-versa. The speed of the impeller can be preferably controlled by means of a dedicated controlling unit that can be embedded in the control unit 405 above cited. Mixing tank 401 also includes a water line for the introduction of water 8 at a controlled flow rate.

Preferably, the mixing tank 401 is also used for transfer to provide continuous slurry supply to a slurry casting station or for transporting the slurry in a remote position from the mixing slurry or for storing the slurry before the casting operation.

Alternatively, a second tank (not shown) is provided for continuous slurry supply to a slurry casting station or for transporting the slurry in a remote position from the mixing slurry or for storing the slurry before the casting operation. The second tank too comprises a cooler, such as water jacket wall to allow water cooling on the external walls of the second tank. Alternatively, the cooler can be a refrigeration machine acting on the external walls of the second tank. The second tank is equipped with one or more temperature sensors. The temperature sensors may comprise temperature probes acting in the slurry for sensing the actual temperature of the slurry. The temperature probes act on different portions of the slurry for ensuring a distributed measurement of the temperatures within the slurry. The temperature probes are electrically connected to a control unit that compares the detected temperature with a threshold temperature value. The control unit is further electrically connected to the cooler for increasing its cooling power in case the detected temperature is below the threshold temperature value and for decreasing its cooling power in case the detected temperature is above the threshold temperature value.

The method of the invention to produce a homogenized tobacco web includes a cooling step 104 in which the slurry prepared in step 103 is cooled to a temperature below about 10 degrees Celsius. The cooling step 104 includes keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes. Preferably, the cooling step 104 is performed for a time period shorter than about 2400 minutes. That is, the slurry is kept to a temperature below about 10 degrees Celsius for less than 2400 minutes. The cooling step 104 starts immediately after the slurry is formed. Preferably, the cooling step 104 starts by cooling the mixing tank 401 as above described in order to keep the temperature of the slurry below about 10 degrees Celsius. In case a second tank is involved for storing or for transporting the slurry, the cooling step 104 continues by cooling the second tank as above described in order to keep the temperature of the slurry below about 10 degrees Celsius.

Preferably, in the cooling step 104 the temperature of the slurry is not kept below the freezing temperature of the slurry. Preferably, in the cooling step 104 the temperature of the slurry is kept between 8 degrees Celsius and 9 degrees Celsius.

The method of the invention to produce a homogenized tobacco web includes further the casting step 105 in which the slurry prepared in step 103 and cooled in step 104 is cast in a continuous tobacco web onto a support. The casting step 105 includes casting, preferably by means of a casting blade, the slurry onto a support, such as a steel conveyor. During the casting step 105, before casting the slurry onto a support, the temperature of the slurry is kept below about 10 degrees Celsius.

Further, in order to obtain a final homogenized tobacco web for the use in an aerosol- formed article, the method of the invention includes a drying step 106 in which the cast web of homogenized tobacco material is preferably dried. The drying step 106 includes drying the cast web, by means of steam and heated air. Preferably, the drying with steam is performed on the side of the cast web in contact with the support, while the drying with heated air is performed on the free side of the cast web.

An apparatus for performing the step of casting 105 and drying 106 is schematically depicted in figure 5. The casting and drying apparatus 500 includes a slurry transfer system 501 , such as a pump, preferably having a flow control, and a casting box 502 to which the slurry is transferred by the pump. Preferably, casting box 502 is equipped with level control 503 and a casting blade 504 for the casting of the slurry into a continuous web of homogenized tobacco material. Casting box 502 may also comprise a density control device 505 to control the density of the cast web. Casting box 502 further comprises a cooler 506, such as water jacket wall to allow water cooling on the external walls of the casting box 502. Alternatively, the cooler 506 can be a refrigeration machine acting on the external walls of the casting box 502. The casting box 502 is equipped with one or more temperature sensors 507. The temperature sensors 507 may comprise temperature probes acting in the slurry for sensing the actual temperature of the slurry. The temperature probes act on different portions of the slurry for ensuring a distributed measurement of the temperatures within the slurry. The temperature probes are electrically connected to a control unit 508 that compares the detected temperature with a threshold temperature value. The control unit 508 is further electrically connected to the cooler 506 for increasing its cooling power in case the detected temperature is below the threshold temperature value and for decreasing its cooling power in case the detected temperature is above the threshold temperature value.

A support, such as a stainless steel belt conveyor 509, receives the slurry cast by the casting blade 504.

Casting and drying apparatus 500 also includes a drying station 510 to dry the cast web of slurry. Drying station 510 comprises a steam heating 51 1 and top air drying 512.

Preferably, at the end of the casting step 105 and of the drying step 106, the homogenized tobacco web is removed from the support 509. Doctoring of the cast web after the drying station 508 at the right moisture content is preferably performed.

Preferably, the cast tobacco web is transported through a secondary drying process to remove further moisture content of the web to reach target moisture.

Claims

1. Method of production of a homogenized tobacco material, said method comprising: providing a tobacco powder blend;

providing a binder and an aerosol-former;

forming a cellulose pulp from cellulose fibers and water;

combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form a slurry; and

cooling the slurry to a temperature below about 10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes.

2. Method according to claim 1 , further comprising:

storing the slurry while cooling.

3. Method according to claim 1 or 2, further comprising:

transporting the slurry while cooling.

4. Method according to any of the preceding claims, wherein the step of providing a binder and an aerosol former includes:

suspending a binder in an aerosol-former to form a suspension; and

wherein combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form a slurry comprises:

combining the suspension of binder in aerosol-former, the cellulose pulp and the tobacco powder blend to form a slurry.

5. Method according to any of the preceding claims, wherein cooling the slurry is performed for a time period shorter than about 2400 minutes.

6. Method according to any of the preceding claims, wherein combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry comprises:

combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend in such a proportion that the cellulose fibers is in an amount comprised between about 1 percent and about 4 percent in dry weight basis of the slurry.

7. Method according to any of the preceding claims, wherein combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry comprises:

combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend in such a proportion that the binder is in an amount comprised between about 1 percent and about 4 percent in dry weight basis of the slurry.

8. Method according to any of the preceding claims, wherein after the step of cooling the slurry to a temperature below about 10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes, it comprises

casting the slurry so as to form a continuous homogenized tobacco web.

9. Method according to any of the preceding claims, wherein after the step of cooling the slurry to a temperature below about 10 degrees Celsius and keeping a temperature of the slurry below about 10 degrees Celsius for a time period longer than or equal to about 60 minutes, it comprises:

casting the slurry so as to form a continuous homogenized tobacco web; and keeping the slurry at a temperature below 10 degrees Celsius also during casting.

10. Method according to any of the preceding claims wherein the binder comprises guar.

1 1 . Method according to claim 10, wherein the guar comprised in the binder is guar gums.

12. Method according to any of the preceding claims, further comprising:

combining the binder, the aerosol-former, the cellulose pulp and the tobacco powder blend to form the slurry in a tank; and

cooling the tank in order to keep a temperature of the slurry below about 10 degrees Celsius.

13. Method according to any of the preceding claims, further comprising:

mixing the slurry.