Method for treating tobacco material and treated tobacco material

Abstract

To provide a method for treating tobacco and a treated tobacco by fermentation.SOLUTION: The invention relates to a method for treating tobacco material, the method comprising: fermenting the tobacco material to obtain treated tobacco material, including: incubating the tobacco material under anaerobic conditions; applying a pressure to the tobacco material comprised between 1000 kilograms per square meter and 4000 kilograms per square meter; keeping the moisture content of the tobacco material comprised between 25 weight percent and 40 weight percent of the total weight of the tobacco material; wherein the fermenting lasts at least one month.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for treating tobacco by fermentation and to the treated tobacco, particularly where the fermentation is anaerobic fermentation. [Background technology]

[0002] Various processing methods and additives have been proposed in the art to alter the overall characteristics or properties of tobacco materials utilized in tobacco products. For example, tobacco materials have been treated with additives. In addition, the processing conditions used during the processing of these tobacco materials have been controlled to alter the chemical or sensory properties of tobacco products produced from such tobacco materials, and to alter the chemical or sensory properties of mainstream smoke or aerosols generated by smoking articles incorporating such tobacco materials.

[0003] Processing tobacco materials to enhance or add flavor and aroma at later stages in tobacco processing often involves adding one or more additive(s) to the tobacco, which can require additional processing steps and equipment, which can be expensive and time-consuming. Furthermore, the addition of additives to tobacco may be viewed unfavorably by some consumers.

[0004] Thus, there is a need to modify the organoleptic properties of tobacco materials in a process that does not involve adding external flavorings to the tobacco itself. Further, there is a need for tobacco materials that exhibit these different organoleptic materials without the need for complex processing. Summary of the Invention

[0005] According to one aspect, the present invention relates to a method for treating tobacco material, the method comprising fermenting the tobacco material. The fermentation step preferably comprises incubating the tobacco material under anaerobic conditions. The fermentation step preferably comprises applying a pressure of 1000 kilograms per square meter to 4000 kilograms per square meter to the tobacco material. The fermentation step preferably comprises maintaining a moisture content of the tobacco material at an amount of 25 weight percent to 40 weight percent of the total weight of the tobacco material. The fermentation step preferably lasts for at least one month.

[0006] According to the method of the present invention, tobacco fermentation occurs under the claimed conditions. Due to fermentation, the specific compounds present in the tobacco material may change, as may the organoleptic properties of the tobacco material. Furthermore, tobacco material fermented by the method of the present invention may exhibit lower levels of asparagine.

[0007] It is known that tobacco material can be fermented. Tobacco plants can host microorganisms, which in turn can include bacteria, molds, and actinomycetes. Studies have shown that bacteria make up the majority of the microorganisms present in tobacco, while molds and actinomycetes are in the minority. Little or no yeast can be detected. Fermented tobacco can be fermented by a variety of suitable techniques known in the art, e.g. http: / / www.scirp.org / journal / jbmTobacco fermentation can be made by techniques such as those described in "Research Progress in Tobacco Fermentation" by Yang Yang et al. (Journal of Biosciences and Medicines 2018, 6, 105-114), available at: http: / / www.yangyang.com / , or U.S. Patent No. 5,372,149, or U.S. Patent No. 4,528,993, and elsewhere. Generally, tobacco fermentation involves adjusting the moisture content of dried, aged tobacco to a moisture content of about 20 percent to about 60 percent, and layering the moistened tobacco for fermentation. Fermentation can be terminated, for example, by drying or cold storage. As noted above, tobacco fermentation does not require the addition of microorganisms, as microorganisms are generally naturally present in tobacco plants.

[0008] In the present invention, fermentation is carried out under anaerobic conditions, unlike those known in the art.

[0009] Anaerobic fermentation is defined as the conversion of complex organic compounds into smaller molecules in the absence of oxygen. This term can also be defined as conditions in which oxygen is unavailable for redox reactions, both as a result of chemical equilibrium and biochemical activity. Instead, other oxidized compounds may be present that can be used by microorganisms for specific types of energy metabolism.

[0010] Anaerobic conditions may coexist with aerobic conditions, and oxygen in gaseous form may be unavailable to microorganisms in the microenvironment (e.g., aggregates of debris suspended in water) while simultaneously being present in the macroenvironment (water).

[0011] In anaerobic tobacco fermentation, without being bound by theory, the main energy extraction pathway may come from glycolysis, and some amino acids are also used as carbon / nitrogen sources. Preferred nitrogen compounds typically include glutamine, alanine, serine, threonine, aspartic acid, asparagine, urea, and arginine.

[0012] The anaerobic conditions are preferably achieved by placing the tobacco material in a container and closing the container. The anaerobic conditions are preferably achieved by placing the tobacco material in a container, removing air from the container, and closing the container in an airtight manner.

[0013] More preferably, pressure is applied to remove air from the tobacco material, the applied pressure "pushing" the air out of the tobacco material, such that after the container is closed, no oxygen, or only a minimal amount, is present in the container.

[0014] Placing the tobacco material in a container and then closing the container after the air has been removed from the sealed container allows anaerobic conditions to be reached quickly. This method of achieving anaerobic conditions is preferred because it is cost-effective and easy to implement.

[0015] Alternatively, the tobacco material is placed in a container and the air is removed and replaced with water.

[0016] The container in which the tobacco material is placed is, for example, a barrel, which is preferably made of wood, concrete, metal, or a combination of any of these three materials.

[0017] The anaerobic conditions are maintained for the desired fermentation period.

[0018] To achieve the desired fermentation according to the present invention, the tobacco material preferably has a moisture content of 25 to 40 weight percent (weight percent) of the total weight of the tobacco material. More preferably, the tobacco material has a moisture content of 25 to 35 weight percent (weight percent) of the total weight of the tobacco material. More preferably, the tobacco material has a moisture content of 28 to 32 weight percent (weight percent) of the total weight of the tobacco material. More preferably, the tobacco material has a moisture content of 30 weight percent (weight percent) of the total weight of the tobacco material. To achieve this moisture content, the tobacco material is preferably moistened with water. Water is added to the tobacco material. The tobacco material is preferably moistened before being introduced into a container where anaerobic conditions are established and maintained.

[0019] Furthermore, this moisture content is maintained throughout the fermentation process. Therefore, it is preferred that the moisture content of the tobacco material be monitored during fermentation. For example, if the tobacco material is introduced into a container in which fermentation occurs, the container may be opened and the moisture content of the tobacco material may be measured as the container is opened. It is preferred that the container be opened at regular intervals to perform measurements of the tobacco moisture.

[0020] The moisture may be measured by a moisture sensor located inside the container. In this way, the moisture may be measured even when the tobacco material is in the sealed container.

[0021] The moisture content of the tobacco material is preferably measured at a constant rate.

[0022] During fermentation, the tobacco material is subjected to pressure. The pressure exerted on the tobacco material is 1000 kilograms per square meter (kg / m 2 ) ~ 4000 kilograms / square meter (kg / m 2 ) is preferably composed of.

[0023] The pressure applied to the tobacco material is maintained within the above range during fermentation.

[0024] Pressure may be applied to the tobacco material by any means. Pressure may be applied by pumping an inert gas into the container. Pressure may also be applied by placing a weight on the tobacco material so that a desired pressure range is applied to the tobacco material. For example, a container may be filled with moist tobacco material, and a weight may be placed in contact with the tobacco material as a "lid" for the container until water seeps out of the container.

[0025] The tobacco material is inserted into the container, and the weight is preferably positioned on or above the tobacco material to exert the desired pressure. The container is then closed, preferably leaving the weight inside the container so that the weight can continue to exert pressure on the tobacco material.

[0026] Hereinafter, the term "fermentation conditions" refers to all three of these conditions: anaerobic conditions, a moisture content of the tobacco material comprising 25 weight percent to 40 weight percent of the total weight of the tobacco material, and an applied pressure of 1000 kilograms per square meter to 4000 kilograms per square meter. Thus, stating that a tobacco material is subject to fermentation conditions means that the tobacco material is subjected to anaerobic conditions, a moisture content of the tobacco material comprising 25 weight percent to 40 weight percent of the total weight of the tobacco material, and an applied pressure of 1000 kilograms per square meter to 4000 kilograms per square meter.

[0027] The tobacco material is subjected to the above-described fermentation conditions for at least one month. Preferably, the tobacco material is subjected to the fermentation conditions for at least two months. Preferably, the tobacco material is subjected to the fermentation conditions for at least six months. Preferably, the tobacco material is subjected to the fermentation conditions for at least 12 months. Preferably, the tobacco material is subjected to the fermentation conditions for at least 24 months. Preferably, the tobacco material is subjected to the fermentation conditions for less than 36 months.

[0028] The application of the fermentation conditions may continue for the entire claimed time (e.g., more than 1 month, or more than 2 months, or more than 6 months, or more than 12 months, or more than 24 months). Alternatively, the fermentation conditions may be applied for multiple time intervals to form a series of time intervals. The time intervals are separated from one another by "interruptions." For example, one or more interruptions may occur during one or more of the following: the presence of anaerobic conditions; a moisture content of 25 weight percent to 40 weight percent of the total weight of the tobacco material; and the application of a pressure of 1,000 kilograms per square meter to 4,000 kilograms per square meter. The interruptions may occur to examine the tobacco material. For example, the moisture content of the tobacco material may be measured during the interruptions. The interruptions may occur to rotate or mix the tobacco material so that a uniformly processed tobacco material can be obtained.

[0029] The interruption may last up to 6 hours.

[0030] Therefore, the total period during which the tobacco is subjected to the fermentation conditions described above is calculated by adding the durations of all time intervals during which the fermentation conditions are actually applied. Alternatively, the total period can be calculated starting from the moment the fermentation conditions are first applied and ending when the fermentation conditions are last applied, with any subsequent periods of interruption "removed."

[0031] For example, given a selected fermentation time T (where "fermentation time" refers to the total period of time that the tobacco material is subjected to fermentation conditions), the following are possible:

[0032] The fermentation conditions are applied continuously for a total period equal to T.

[0033] Fermentation conditions are N fermentation time intervals t1, t2, ..., t N applied over t1+t2+...+t N = T. Fermentation time interval t j and the subsequent time interval t j+1 The time gap between is the interruption.

[0034] This total period T is at least 1 month, or at least 2 months, or at least 6 months, or at least 12 months, or at least 24 months).

[0035] Preferably, there is a break between two consecutive time intervals during which the fermentation conditions are applied, the break lasting no more than 6 hours.

[0036] Fermentation conditions are applied to the tobacco material for at least one month to ensure the desired chemical modification of the tobacco material. For example, fermentation conditions may be applied until a desired amount of one or more chemicals is reached in the tobacco material. For example, chemicals contained in the tobacco material may be decreased or increased by the fermentation conditions. Thus, the fermentation conditions are stopped when the desired amount of chemicals is reached. For example, fermentation conditions may be applied until a desired color of the tobacco material is achieved.

[0037] Anaerobic fermentation occurs when tobacco raw materials are subjected to fermentation conditions.

[0038] The temperature of the tobacco material during fermentation (while fermentation conditions are applied) may remain within the range of 25°C to 35°C, more preferably 27°C to 31°C. The temperature of the tobacco material is substantially maintained within this range throughout the entire fermentation (while fermentation conditions are applied). The temperature is maintained by the fermentation itself, and there is no need to provide or subtract heat to the tobacco material. This temperature of the tobacco material during fermentation is obtained when the ambient temperature around the tobacco material is preferably comprised between 15°C and 25°C.

[0039] The amounts of reducing sugars and free amino acids present in tobacco materials during fermentation under fermentation conditions are monitored. The most abundant naturally occurring sugars in tobacco leaves are glucose, fructose, and sucrose. Differences in sugar content can exist between tobacco types. For example, Virginia is characterized by a high sugar content (generally in the range of 8% to 30%), while Burley is characterized by a low sugar content (generally in the range of 1% to 2%). However, regardless of the tobacco type used in the tobacco material, a decrease in the content of reducing sugars during fermentation under the fermentation conditions of the present invention was found.

[0040] Varying the amount of reducing sugars can change the organoleptic properties of the tobacco material and the smoke or aerosol produced with the tobacco material.

[0041] Furthermore, tobacco materials contain multiple levels of amino acids. Amino acids can substantially contribute to the levels of specific components in the smoke or aerosol produced by final products containing fermented tobacco material, as well as to the sensory characteristics of the smoke or aerosol. Different types of tobacco can contain different amounts of amino acids. Furthermore, there can be (mainly quantitative) differences in amino acid composition between tobacco leaves, tips, or petioles. Also, the location of tobacco growth can alter the ratio of levels of different amino acids, although a fairly similar composition of the same tobacco amino acids is generally maintained. Regardless of the tobacco type and origin, it has been observed that the asparagine content in tobacco materials decreases during fermentation under the fermentation conditions of the present invention.

[0042] This suggests that the fermenting bacteria in the fermentation of the present invention produce specific asparaginase(s) to assimilate C and N from the amino acid resource.

[0043] Asparagine can be thermally converted to acrylamide, which is considered a potentially harmful substance. Achieving a reduction in the asparagine content in tobacco materials would be desirable, as this would coincide with a reduction in acrylamide formation.

[0044] The above-described changes in the amount of asparagine and the amount of reducing sugars in the tobacco material can be observed one month after the fermentation conditions are applied to the tobacco material, and the fermentation conditions are applied to the tobacco material and continue to be applied for at least one month.

[0045] In the method of the present invention, anaerobic fermentation of tobacco material occurs when the tobacco material is subjected to fermentation conditions. This anaerobic fermentation alters the amount of reducing sugars and asparagine in the tobacco material. Therefore, reduction of certain potentially harmful substances can be achieved through a natural process such as fermentation and without the addition of additives or external microorganisms to the tobacco material. These substances may include acrylamide. Fermentation may also change the organoleptic properties of the tobacco material. These changes in organoleptic properties occur because reducing sugars are converted to pyruvate and pyruvic acid, which are precursors of many other flavor compounds. This means that there may be significant changes in the organoleptic properties of the tobacco material after fermentation in accordance with the present invention. The taste properties of the tobacco material may change compared to the taste properties of the same tobacco material subjected to conventional drying and without the application of fermentation under fermentation conditions in accordance with the present invention.

[0046] As used herein, the term "alter" or "altered" is used in the context of flavor or organoleptic characteristics and means that there is a modification, which may include an improvement, from one overall taste or sensory characteristic to another as identified by a skilled smoker.

[0047] Preferably, the method includes drying the tobacco material to obtain a dried tobacco material having a moisture content of 1 weight percent to 15 weight percent of the total weight of the tobacco material. The drying step is preferably carried out after fermentation under fermenting conditions has concluded. After a total fermentation period T has elapsed, the treated tobacco material is preferably removed from its container and the pressure applied to the tobacco is preferably reduced. The treated tobacco material is then dried to a moisture content of 1 weight percent to 15 weight percent of the total weight of the tobacco material, more preferably 5 weight percent to 10 weight percent. Drying is carried out so that the treated tobacco material can be easily processed in subsequent steps.

[0048] Preferably, the method includes a step of drying the tobacco material before fermentation. The tobacco material processed by the method of the present invention may include cured tobacco. As used herein, the term "cured tobacco" refers to cured tobacco. The drying of the tobacco is preferably achieved by standard procedures and may depend on the type of tobacco contained in the tobacco material. The tobacco material may include different types of tobacco and tobacco that has undergone different curing. Different types of tobacco may be blended and then processed by the present invention.

[0049] Alternatively, or additionally, the tobacco material treated by the method of the present invention may include re-graded tobacco, raw leaf blended tobacco, conditioned tobacco, stemmed or de-stemmed tobacco (or not in the case of whole leaf), flue-cured tobacco, or packer tobacco.

[0050] Preferably, the method includes maintaining the temperature of the tobacco material at a temperature comprised between 25°C and 35°C. The temperature of the tobacco material is maintained between 25°C and 35°C while the tobacco material is subjected to fermentation conditions. The temperature of the tobacco material is automatically maintained within this range by the fermentation process. No additional equipment is required to cool or heat the tobacco material.

[0051] Preferably, the method includes a step of rotating the tobacco material. Rotating the tobacco material may provide improved homogenization. Rotating the tobacco material may mean turning the tobacco material upside down. Rotating the tobacco material may mean turning the tobacco material upside down. The interruption of the fermentation conditions caused by the rotation may also be used to measure certain parameters of the tobacco material, such as the moisture content. During the rotation of the tobacco material, the fermentation conditions may no longer be applied. Not all, or only some, of the three fermentation conditions may be applied during the rotation. The fermentation process is therefore "interrupted." After the rotation, the fermentation conditions are preferably applied again to the tobacco material.

[0052] Preferably, the method includes securing the tobacco material within a moisture-retaining material. This step of securing the tobacco material preferably occurs before the tobacco material is subjected to fermentation conditions. The moisture-retaining material desirably resists degradation during the tobacco treatment process (fermentation). The moisture-retaining material may comprise a flexible material. This flexible material may be wrapped around the tobacco material. Preferably, the moisture-retaining material comprises a plastic material. Alternatively, or additionally, the moisture-retaining material may comprise a rigid material. The container into which the tobacco material is introduced may function as the moisture-retaining material. In this case, the material of the container may comprise, for example, metal, wood, plastic, or concrete.

[0053] Preferably, the method includes wetting the tobacco material in water prior to fermentation to achieve a moisture content of the tobacco material of 25 to 40 weight percent of the total weight of the tobacco material. After drying, the moisture content of the tobacco material is generally low. Therefore, it is preferred that water be added to the tobacco material to achieve a moisture level of 25 to 35 weight percent. More preferably, water is also added during the fermentation process to maintain the moisture content of the tobacco material at 25 to 40 weight percent of the total weight of the tobacco material for at least one month, more preferably at least two months, preferably at least six months, preferably at least 12 months, and preferably at least 24 months.

[0054] In another aspect, the present invention relates to a tobacco material treated by the method of the previous aspect, wherein the treated tobacco material contains an amount of asparagine that is at least 50 percent, more preferably 60 percent, and even more preferably 80 percent lower than the amount of asparagine contained in the same tobacco material before treatment according to the previous aspect. At the end of fermentation, the amount of asparagine is preferably at least 50 percent, more preferably 60 percent, and even more preferably 80 percent lower than the amount of asparagine contained in the same tobacco material before treatment. Tobacco treated by the method of the present invention may have a changed chemical composition relative to untreated tobacco. In this context, "treated tobacco material" refers to a tobacco material that has undergone the described treatment in a previous process, i.e., that has been subjected to fermentation conditions for at least one month. In this context, "untreated tobacco material" refers to a tobacco material that has not undergone the described treatment in a previous process, i.e., that has not been subjected to fermentation conditions. Untreated tobacco material is, for example, tobacco material that has been inserted into a container before the treatment of the present invention begins. The treated tobacco material is compared to the same tobacco material that has not undergone the treatment according to the present invention (untreated tobacco material). The decrease in asparagine can be associated with an increase in aspartic acid, suggesting that fermenting bacteria produce specific asparaginase(s) to assimilate C and N from amino acid resources. This reaction can produce ammonia.

[0055] The treated tobacco material preferably contains at least 50 percent, more preferably 60 percent, and even more preferably 80 percent less glutamine than the amount of glutamine contained in the same tobacco material before treatment by the method of the previous embodiment. At the end of fermentation, the amount of glutamine is preferably at least 50 percent, more preferably 60 percent, and even more preferably 80 percent less glutamine than the amount of glutamine contained in the same tobacco material before treatment. Tobacco materials treated by the method of the present invention may change their chemical composition relative to untreated tobacco materials. Treated tobacco materials are compared with the same tobacco material not subjected to treatment by the present invention. A decrease in glutamine may be associated with an increase in glutamic acid. This suggests that fermentation bacteria produce specific glutaminase(s) to assimilate carbon and nitrogen from amino acid sources. This reaction may produce ammonia.

[0056] The treated tobacco material preferably contains a total reducing sugar content that is at least 50 percent, more preferably 60 percent, and even more preferably 85 percent lower than the total reducing sugar content of the same tobacco material prior to treatment by the method of the previous embodiment. At the end of fermentation, the total reducing sugar content is preferably at least 50 percent, more preferably 60 percent, and even more preferably 85 percent lower than the total reducing sugar content of the same tobacco material prior to treatment. Reducing sugars are the sum of glucose, fructose, sucrose, and maltose. Most of the reducing sugars in the treated tobacco material can be converted. Reducing sugar sources, such as glucose and fructose, present in the starting tobacco material can be used as an energy source by anaerobic bacteria. In the absence of oxygen, the glycolytic pathway converts glucose (or fructose) to pyruvate. Changes in the levels of these compounds can contribute to the desirable taste and aroma of the treated tobacco material.

[0057] The treated tobacco material is preferably at least 100 times more acidic than the untreated tobacco material. The pH of the treated tobacco material and the pH of the untreated tobacco material may differ by at least 2 pH units. The pH may remain substantially unchanged for the different tobacco materials.

[0058] The processed tobacco preferably contains lactic acid. Lactic acid is known to be a relevant catabolic product in anaerobic fermentation. Lactic acid may have a "smoothing effect" on the harshness of nicotine. Lactic acid may be responsible for the decrease in pH of the processed tobacco material.

[0059] According to another aspect, the present invention relates to a tobacco material comprising less than 3 percent total reducing sugars on a total dry weight basis. More preferably, the tobacco material comprises less than 2 percent total reducing sugars on a total dry weight basis. Even more preferably, the tobacco material comprises less than 1 percent total reducing sugars on a total dry weight basis. Preferably, the tobacco material comprises less than 300 milligrams / kilogram of asparagine on a total dry weight basis. The tobacco material is a fermented tobacco material. Preferably, the tobacco material is a tobacco material that has been processed by the method of the present invention.

[0060] The advantages of the tobacco material of the present invention have already been outlined with reference to the previous embodiment and will not be repeated here.

[0061] Fermentation is obtained without the addition of microorganisms other than those already contained in the tobacco material prior to fermentation.

[0062] Preferably, the tobacco material contains less than 70 milligrams per kilogram of glutamine on a total dry weight basis.

[0063] Preferably, the tobacco material comprises greater than 10,000 milligrams / kilogram of total free amino acids on a total dry weight basis.

[0064] Preferably, the tobacco material comprises hand-stripped leaves from which the veins have been removed.

[0065] The tobacco material is preferably dried, preferably before fermentation.

[0066] Preferably, the tobacco material comprises Kasturi tobacco.

[0067] According to a different aspect, the present invention relates to an aerosol-generating article comprising tobacco material according to the previous aspect.

[0068] The term "tobacco material" refers to any part of the tobacco plant or a mixture of different plants, including, but not limited to, tobacco waste, unprocessed tobacco waste, tobacco stems, tobacco dust produced during tobacco processing, tobacco prime lamina shreds, and combinations thereof. Tobacco material can be in the form of processed tobacco parts or fragments, cured and aged tobacco in essentially natural lamina or stem form, tobacco extract, or a mixture of the above, such as a mixture of extracted tobacco pulp combined with granulated cured and aged natural tobacco lamina. Tobacco material can be in solid, liquid, semi-solid, or the like. The term "tobacco material" preferably includes any part and any associated by-products, such as the leaves or stems of any member of the Nicotiana genus. Tobacco material for use in the present invention is preferably derived from the species Nicotiana tabacum. Any type, style, or variety of tobacco can be processed. Examples of tobacco that can be used include, but are not limited to, Virginia, Burley, Orient tobacco, and any blends of these types. Preferably, the tobacco material comprises Kasturi tobacco. The tobacco material to be treated may comprise or consist of tobacco after curing.

[0069] As used herein, the term "cured tobacco" refers to tobacco that has been cured but has not undergone any further processing to alter the taste or aroma of the tobacco material. The cured tobacco may be blended with other styles, varieties, or types of tobacco. Alternatively, or additionally, the processed tobacco material may include or consist of re-graded tobacco, raw leaf blended tobacco, conditioned tobacco, stemmed or destemmed tobacco (or not in the case of whole leaf), cured tobacco, or packed tobacco.

[0070] The tobacco material preferably comprises laminar tobacco material. The tobacco may comprise between about 70% and 100% laminar material.

[0071] When the tobacco material comprises lamina tobacco material, the lamina may be in the form of whole leaves. In some embodiments, the tobacco material comprises cured whole leaf tobacco. In some embodiments, the tobacco material substantially comprises cured whole leaf tobacco. In some embodiments, the tobacco material consists essentially of cured whole leaf tobacco.

[0072] In some embodiments, the tobacco material comprises stem tobacco material. The tobacco may comprise up to 30 percent stem material.

[0073] The process of "curing" green tobacco depends on the type of tobacco harvested. For example, Virginia flue (bright) tobacco is typically flue-cured, while burley and certain dark strains are usually air-cured. Flue-curing of tobacco typically occurs over a period of 5-7 days, compared to air-curing, which occurs over a period of 1-2 months. A number of major chemical and biochemical changes begin during the curing process and continue throughout the early stages of leaf drying. The transformation of tobacco from yellow to brown generally results in the formation and significant accumulation of nitrosamines and an increase in microbial content.

[0074] Different types of curing are used for different types of tobacco.

[0075] Virginia tobacco is typically "air-cured." Tobacco leaves are hung in drying barns, where heated air is blown on to dry the leaves. As the leaves lose moisture, they develop their unique aroma, texture, and color. Farmers must carefully navigate this process, which can take up to a week, during which the temperature of the heated air must be constantly monitored and gradually increased. Too much or too little heat at any stage of the process can have a negative impact on the quality of the tobacco.

[0076] Burley and Orient tobacco are dried in different ways. Burley is "air-dried" in barns where heat and humidity come from natural ventilation. The drying process can take up to two months. Orient tobacco is "sun-dried" by hanging the leaves outside in the sun for around two weeks.

[0077] In this text, the verbs "comprise" and "include" are synonymous and both indicate a non-exhaustive list of features. The verb "consist" indicates an exhaustive list.

[0078] The present invention is defined in the claims. However, the following provides 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 any other example, embodiment, or aspect described herein.

[0079] [Example 1] 1. A method for processing tobacco material, the method comprising: fermenting a tobacco material to obtain a treated tobacco material, which Incubating the tobacco material under anaerobic conditions; ■ Applying a pressure of 1000 kilograms per square meter to 4000 kilograms per square meter to the tobacco material; Maintaining the moisture content of the tobacco material at an amount comprised between 25 weight percent and 40 weight percent of the total weight of the tobacco material, A method that allows fermentation to continue for at least one month.

[0080] [Example 2] The method of Example 1, comprising: A method comprising the step of drying a tobacco material to obtain a dried tobacco material having a moisture content of 5 weight percent to 10 weight percent of the total weight of the tobacco material.

[0081] [Example 3] The method according to Example 1 or Example 2, A method comprising the step of drying the tobacco material before fermentation. [Example 4]

[0082] The method according to one or more of Examples 1 to 3, wherein the fermentation lasts for less than 3 years.

[0083] [Example 5] The method according to one or more of Examples 1 to 4, A method comprising the step of rotating a tobacco material.

[0084] [Example 6] The method according to one or more of Examples 1 to 5, a method comprising adding water to the tobacco material to maintain the moisture content of the tobacco material in an amount comprised between 25 weight percent and 40 weight percent of the total weight of the tobacco material.

[0085] [Example 7] 7. The method of one or more of Examples 1 to 6, comprising maintaining the temperature of the tobacco material at a temperature comprised between 25°C and 35°C.

[0086] [Example 8] The method according to one or more of Examples 1 to 7, A method comprising securing tobacco material within a moisture-retaining material.

[0087] [Example 9] The method according to one or more of Examples 1 to 8, a method comprising wetting the tobacco material in water prior to fermentation so as to achieve a moisture content of the tobacco material of between 25 weight percent and 40 weight percent of the total weight of the tobacco material.

[0088] [Example 10] The method of one or more of Examples 1-9, wherein the amount of asparagine in the treated tobacco material is at least 50 percent lower than the amount of asparagine contained in the same tobacco material before treatment according to Examples 1-9.

[0089] [Example 11] The method of one or more of Examples 1-10, wherein the amount of asparagine in the treated tobacco material is at least 50 percent lower than the amount of asparagine contained in the same tobacco material before treatment according to Examples 1-10.

[0090] [Example 12] The method of one or more of Examples 1-11, wherein the amount of reducing sugars in the treated tobacco material is at least 50 percent lower than the amount of reducing sugars contained in the same tobacco material before treatment according to Examples 1-11.

[0091] [Example 13] A tobacco material processed according to any one of Examples 1 to 12, wherein the processed tobacco material contains an amount of asparagine that is at least 80 percent lower than the amount of asparagine contained in the same tobacco material before processing according to Examples 1 to 12. Example 14: A processed tobacco material according to Example 13, wherein the processed tobacco material contains an amount of glutamine that is at least 80 percent lower than the amount of glutamine contained in the same tobacco material before processing according to Examples 1 to 12.

[0092] [Example 15] A treated tobacco material as described in Example 13 or Example 14, wherein the treated tobacco material contains an amount of total reducing sugars that is at least 85 percent lower than the amount of total reducing sugars contained in the same tobacco material before treatment according to Examples 1 to 12.

[0093] [Example 16] 16. The treated tobacco material of any of Examples 13-15, wherein the treated tobacco material is at least 100 times more acidic than the same tobacco material before treatment according to Examples 1-12.

[0094] [Example 17] A tobacco material comprising: less than 3 percent total reducing sugars on a total dry weight basis; Tobacco materials containing less than 300 milligrams per kilogram of asparagine on a total dry weight basis.

[0095] [Example 18] 18. The tobacco material of Example 17, o Tobacco material containing less than 1 percent total reducing sugars on a total dry weight basis.

[0096] [Example 19] The tobacco material according to Example 17 or Example 18, Tobacco material containing less than 70 milligrams per kilogram of glutamine on a total dry weight basis.

[0097] [Example 20] 19. The tobacco material of one or more of Examples 17-19, wherein the fermented tobacco material is: - Tobacco material containing more than 10,000 milligrams / kilogram of total free amino acids on a total dry weight basis.

[0098] [Example 21] The tobacco of any one of Examples 17 to 20, comprising lactic acid.

[0099] [Example 22] 22. The tobacco material of one or more of Examples 17-21, wherein the tobacco material comprises hand-stripped leaves from which the veins have been removed.

[0100] [Example 23] 23. The tobacco material of one or more of Examples 17-22, wherein the tobacco material is dried.

[0101] [Example 24] 25. The tobacco material of one or more of Examples 17-24, comprising lactic acid.

[0102] [Example 25] An aerosol-generating article comprising the tobacco material described in any one of Examples 17 to 24.

[0103] The embodiments will now be further described with reference to the following figures: [Brief explanation of the drawings]

[0104] [Figure 1] FIG. 1 is a histogram showing the amount of lactic acid in the tobacco material of Example 1 measured before (0T) and after 6 months (3T) of fermentation according to the present invention. [Figure 2] FIG. 2 is a histogram showing the amount of lactic acid in the tobacco material of Example 2 measured before (0T) and after 6 months (3T) of fermentation according to the present invention. [Figure 3] FIG. 3 is a histogram showing the amount of total alkaloid (TA) levels (percent of total dry weight basis DW) in the tobacco material of Example 1 measured before (0T) and during fermentation according to the present invention, respectively. [Figure 4] FIG. 4 is a histogram showing the amount of total alkaloid (TA) levels (percent of total dry weight basis DW) in the tobacco material of Example 2 measured before (0T) and during fermentation according to the present invention. [Figure 5] FIG. 5 is a histogram showing the amount of glutamine and glutamic acid in the tobacco material of Example 1 (on a total dry weight basis, DW) measured before (0T) and during fermentation according to the present invention, respectively. [Figure 6] FIG. 6 is a histogram showing the amount of glutamine and glutamic acid in the tobacco material of Example 2 (on a total dry weight basis, DW) measured before (0T) and during fermentation according to the present invention, respectively. [Figure 7] FIG. 7 is a histogram showing the amounts of asparagine and aspartic acid in the tobacco material of Example 1 (on a total dry weight basis, DW) measured before (0T) and during fermentation, respectively, according to the present invention. [Figure 8] FIG. 8 is a histogram showing the amounts of asparagine and aspartic acid in the tobacco material of Example 2 (on a total dry weight basis, DW) measured before (0T) and during fermentation, respectively, according to the present invention. [Figure 9] FIG. 9 is a histogram showing the amount of total alkaloids in the tobacco material of Example 3 (on a total dry weight basis, DW) measured before (VG-BF), during, and after fermentation (VG-AF) according to the present invention. [Figure 10] FIG. 10 is a histogram showing the amount of reducing sugars in the tobacco material of Example 3 (on a total dry weight basis, DW) measured before (VG-BF), during, and after fermentation (VG-AF) according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0105] First and second tobacco materials were prepared that were the same tobacco type but underwent different processing before fermentation. The tobacco source was Kasturi tobacco.

[0106] [Example 1] Dark tobacco leaf material was thoroughly sun-dried for approximately 10 days. The sun-dried leaves were stripped to retain only the lamina (hand-stripped leaves). This tobacco material is called "HS."

[0107] The tobacco material was conditioned to obtain a moisture content of approximately 30 percent. This conditioned, but not yet fermented, sample of tobacco material is referred to as 0T ("starting material").

[0108] The conditioned tobacco material is then introduced into three barrels, each barrel containing approximately 100 kilograms of tobacco material. Prior to introduction, the tobacco material is wrapped in the resulting moisture-retaining material.

[0109] Pressure is applied to each barrel, ranging from 1000 kilograms per square meter to 4000 kilograms per square meter.

[0110] After 1 month (sample designated 1T), 2.5 months (sample designated 2T), 6 months (sample designated 3T), and 8.5 months (sample designated 4T), the barrels were opened and at least three samples were taken from each barrel before turning the tobacco and before readjusting the moisture content to approximately 30 percent ± 5 percent.

[0111] During the anaerobic fermentation process, the temperature inside the barrel did not increase significantly (it remained within the range of 27-31°C). Fermentation was stopped after 8.5 months.

[0112] [Example 2] Dark tobacco material was allowed to yellow for two days and then rapidly shredded with a cut filler. This tobacco material contained both lamina and veins. The shredded leaves, containing both lamina and midrib, were sun-dried for two days. This tobacco material sample is hereinafter designated "CC."

[0113] The tobacco material was conditioned to obtain a moisture content of approximately 30 percent. This conditioned, but not yet fermented, sample of tobacco material is referred to as 0T ("starting material").

[0114] The conditioned tobacco material is then introduced into three barrels, each containing approximately 100 kg of tobacco material. Prior to introduction, the tobacco material is wrapped in the resulting moisture-retaining material.

[0115] Pressure is applied to each barrel, ranging from 1000 kilograms per square meter to 4000 kilograms per square meter.

[0116] After 1 month (sample designated 1T), 2.5 months (sample designated 2T), 6 months (sample designated 3T), and 8.5 months (sample designated 4T), the barrels were opened and at least three samples were taken from each barrel before turning the tobacco and before readjusting the moisture content to approximately 30 percent ± 5 percent.

[0117] During the anaerobic fermentation process, the temperature inside the barrel did not increase significantly (it remained within the range of 27-31°C). Fermentation was stopped after 8.5 months.

[0118] [Visual observation] The initial tobacco material had already changed after 2.5 months of fermentation (sample 2T), with both HS and CC leaves darker in color and the tobacco aroma developing a nice caramelized buttery and fermented complex character. The dark color was more pronounced in the fermented HS leaves compared to the CC leaves at the end of the process (8.5 months, sample 4T), likely due to the presence of the midvein in the CC leaves.

[0119] [Chemical analysis] In the following, when values ​​relating to a sample are mentioned, the given value represents the average of several values ​​obtained for each sample of the same type.

[0120] After 2.5 months of fermentation conditions (as found for sample 2T), the pH of the tobacco material samples (both CC and HS) became acidic, reaching 3.2. This reflects the process of anaerobic fermentation accompanied by sugar decomposition, which usually produces organic acids such as (acetic and / or) lactic acid. The starting pH of tobacco material is generally comprised between pH 5 and pH 6.

[0121] Figures 1 and 2 show the presence of lactic acid in tobacco materials. As shown by the figures (Figure 1 represents the lactic acid content of HS leaves, and Figure 2 represents the lactic acid content of CC leaves), before fermentation, all samples are free of lactic acid (three samples 0T per tobacco material (CC or HS) are shown). After fermentation (in this case, after six months, three samples for the tobacco material, referred to as 3T, are shown for both tobacco materials (CC or HS)), all samples (both CC and HS leaves) show the presence of lactic acid, albeit in variable amounts.

[0122] Alkaloids were not degraded or degraded only slightly during fermentation. Total alkaloid (TA) content as a percentage of total dry weight (denoted as %DW in the figures) is shown in Figure 3 (HS leaves) and Figure 4 (CC leaves). Total alkaloid content remained fairly stable during fermentation. After 8.5 months (4T), only 4% degraded in HS leaves and 9% degraded in CC leaves. While statistically relevant, these small variations may result from sampling alone. Some limited alkaloid hydrolase activity may not be excluded. Total alkaloids were analyzed in samples collected at the beginning (0T, n = 6 samples analyzed), 1 month (1T, n = 9), 2.5 months (2T, n = 9), 6 months (3T, n = 9), and 8.5 months (4T, n = 12) during the heavy fermentation process. T-tests (test statistics) were performed for comparison with the control unfermented cured tobacco (0T). The results are shown in Figures 3 and 4, which show p-values ​​as follows: *, p < 0.05; **, p<0.01 and ***, p<0.001.

[0123] HS leaf sample 4T and CC leaf sample 3T have p-values ​​<0.01, while CC leaf samples 1T and 4T have p-values ​​<0.001, indicating a statistically significant difference between the fermented and non-fermented tobacco materials.

[0124] Nitrate content was unaffected by the heavy fermentation process. However, some effects were observed on tobacco-specific nitrosamines (TSNAs): NNN (N'-nitrosonornicotine), NNK (nicotine-derived nitrosamine ketone), and NAT (N'-nitrosoanatabine). After 8.5 months of fermentation, no changes were measured for NNK and NAT. However, increases in NNN were observed in both HS (a three-fold increase) and CC (a five- to six-fold increase). Nornicotine, the precursor of NNN before nitration, did not increase correspondingly. Therefore, NAT and NNK may be partially degraded by bacteria during fermentation, but NNN may not be partially degraded. This is because NNK and NAT initially increased twofold by 2.5 months of fermentation and then declined to their initial values ​​in unfermented tobacco. This observation may imply that nitration of alkaloids occurs during heavy fermentation.

[0125] The evolution of sugars and free amino acids during heavy fermentation according to the present invention has been analyzed. The values ​​of measurements performed on tobacco material samples are collected in Table 1. Table 1 shows the evolution of sugars and amino acids during the heavy fermentation process, from an untreated tobacco material sample (Sample 0T) to 8.5 months into the fermentation process (Sample 4T) under fermentation conditions in barrels containing either hand-stripped (HS) or shredded (CC) leaves, as in Examples 1 and 2. All values ​​in the table are on a total dry weight basis. Units of reducing sugars are percent of the total dry weight basis, while free amino acids are in milligrams per kilogram of total dried tobacco material. A decrease in reducing sugars occurred after 2.5 months (2T, see Table 1), in sync with color change and slurry acidification. Glucose and fructose are two tobacco leaf substrates that can be metabolized by anaerobic bacteria in the fermentation barrel. Conversely, most amino acids increased during the process. Both asparagine and glutamine significantly decreased. Overall, these observations may indicate that the main fermentation activity occurred between months 1 and 3. Proline was not degraded under anaerobic fermentation (see Table 1). Ornithine increased significantly (>100-fold) during fermentation in both HS and CC, and citrulline (data obtained from metabolomic analysis between 0T and 3T) increased 16-fold in HS and 2-fold in CC. This may indicate that (plant-derived) lactic acid bacteria are active in tobacco fermentation barrels, since these bacteria have been described to produce ornithine and citrulline at high levels (Rakhimuzzaman et al., Biol Pharm Bull. 2019;42(9):1581-1589).

[0126] [Table 1]

[0127] Figures 5-8 show the amounts of glutamine and asparagine in tobacco materials. As shown by Figures 5-8 and based on the data presented in Table 1, the deamination of glutamine and asparagine that occurs during the anaerobic fermentation process of both HS and CC leaves can be correlated with the simultaneous increase in glutamate and aspartate, respectively. This suggests that the fermentation bacteria produce specific glutaminases and asparaginases to assimilate C and N from amino acid sources. Both reactions produce ammonia, which increased two-fold during the anaerobic fermentation process of both HS and CC leaves. Figures 5 and 6 show the levels of glutamine (white histograms) and glutamate (black histograms) in HS and CC leaves, respectively. It is clear from the figures that glutamine decreases and glutamate increases during fermentation. Figures 7 and 8 show the levels of asparagine (striped histograms) and aspartic acid (black histograms) in HS and CC leaves, respectively. It is clear from the figures that asparagine decreases and aspartic acid increases during fermentation.

[0128] A metabolomic study was conducted to identify marker molecules or pathways associated with the anaerobic tobacco leaf fermentation process. Sugar sources, such as glucose and fructose, present in both HS and CC leaf starting materials (controls) can be used as energy sources by anaerobic bacteria (see Table 1). In the absence of oxygen, the glycolytic pathway converts glucose (or fructose) to pyruvate, producing two ATPs and two NADH+H+. Other organic and abundant carbon compounds that can be rapidly utilized by anaerobic bacteria are citrate and malate (Bintsis, T, 2018, AIMS Microbiology, 4(4): 665-684), both of which are the most abundant organic acids in plants. Similar to reducing sugars, citrate and malate are also metabolized during tobacco heavy fermentation. Chemical analysis of the samples showed that over 60% of the glucose, fructose, citrate, and malate present in the starting tobacco material (Sample 0T) and hand-stripped and shredded leaves were catabolized after six months of heavy fermentation (Sample 3T). Another observation that can be linked to the consumption of these organic molecules is the increase in pyruvate (13-14-fold) in both HS and CC fermented tobacco materials. Pyruvate is a substrate for several reactions that can occur under anaerobic conditions: (1) the production of D-lactate, primarily to regenerate NAD+ for glycolytic reactions; and (2) the production of acetate, diacetyl, and 2,3-butanediol, which may contribute to the delivery of aromatic compounds and flavor in heavy fermented tobacco. Pyruvate can lead to the generation of aromatic compounds such as 2,3-butanediol or lactic acid as a product of lactic acid bacteria.

[0129] Two other pathways emerged from metabolomic analysis of heavily fermented tobacco: (1) tryptophan degradation and (2) chlorogenic acid catabolism.

[0130] Regarding tryptophan degradation, a pathway was described by Ummadi and Weimer (2001, J. Dairy Sci. 84:1773-1782) for cheese bacteria and adapted accordingly. In this case, more than 78% of the tryptophan present in the starting tobacco material (sample 0T) was catabolized after 6 months of fermentation (sample 3T) in both HS and CC leaves. The pathway showed that the product resulting from these catabolic reactions was primarily indole-3-lactic acid, as indicated by a 14-fold and 28-fold increase in HS and CC leaves, respectively. Other compounds belonging to this pathway did not show such an increase. No specific aromatic properties were reported for this compound.

[0131] Chlorogenic acid (CGA), an important biologically active dietary polyphenol, is produced by certain plant species, such as tobacco, and is a major component of coffee. In heavily fermented tobacco leaves, CGA is completely degraded after the anaerobic fermentation process. Meanwhile, the products resulting from CGA catabolism, namely, quinoic acid and caffeic acid, increased after 6 months of fermentation in both HS and CC leaves. This is likely due to bacterial cinnamoyl esterase activity, as documented by Guglielmetti et al. (2008, Applied and Environmental Microbiology, 74, 4: 1284-1288). Therefore, a portion of the quinoic acid and caffeic acid pools likely result from the hydrolysis of CGA, neither of which has been reported to have flavor properties.

[0132] The elevated presence of pyruvic acid, indole-3-lactic acid, and the absence of chlorogenic acid in heavily fermented tobacco compared to cured tobacco may make them useful as chemical markers.

[0133] For purposes of this specification and the appended claims, unless otherwise indicated, all numbers expressing amounts, quantities, percentages, and the like should be understood in all instances to be modified by the term "about." Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therebetween, which may or may not be specifically recited herein. Accordingly, in this context, the number A is understood as A ± 10 percent. Within this context, the number A may be considered to include a numerical value that is within the common standard error for measurement of the property represented by the number A. In some cases, as used in the appended claims, the number A may deviate by the percentages recited above, provided that the amount by which A deviates does not materially affect the basic and novel property(ies) of the claimed invention. Also, all ranges include the disclosed maximum and minimum points, and include any intermediate ranges therebetween, which may or may not be specifically recited herein.

[0134] A third tobacco material was prepared that was a different tobacco type than those in Examples 1 and 2. The tobacco material was Virginia tobacco.

[0135] [Example 3] The tobacco leaf material was thoroughly sun-dried for approximately 10 days. The sun-dried leaves were treated as a standard for Virginia tobacco.

[0136] The tobacco material was conditioned to obtain a moisture content of approximately 30 percent. This conditioned, but not yet fermented, sample of tobacco material is called BF (Before Fermentation Starting Material).

[0137] The conditioned tobacco material is then introduced into two barrels, each containing approximately 100 kilograms of tobacco material. Prior to introduction, the tobacco material is wrapped in the resulting moisture-retaining material.

[0138] Pressure is applied to each barrel, ranging from 1000 kilograms per square meter to 4000 kilograms per square meter.

[0139] The barrels were opened after 1 month (sample designated 1T), 2 months (sample designated 2T), 3 months (sample designated 3T), 4 months (sample designated 4T), 5 months (sample designated 5T), 6 months (sample designated 6T), 7 months (sample designated 7T), and 8 months (sample designated AF, post-fermentation).

[0140] During each month, the tobacco material in the two barrels was rotated at least six times.

[0141] Samples were taken before fermentation (VG-BF: starting material, six replicates), during the fermentation process (every month from VG-T1 to VG-T7, three replicates per barrel), and after fermentation (VG-AF: post-fermentation, six replicates).

[0142] During sampling, the tobacco material was rotated and the moisture content of the tobacco material was readjusted to approximately 30 percent ± 5 percent.

[0143] During the heavy fermentation process under fully anaerobic conditions, no significant temperature changes were observed during the fermentation process, which varied linearly from 30°C at the beginning of fermentation (VG-T1) to 26°C at the end of fermentation (VG-AF). The temperature was measured inside the barrel using a captor.

[0144] The pH of the tobacco material did not change significantly during the fermentation process (T1-AF) and remained at 5.1 ± 0.3. Fermentation was stopped after eight months.

[0145] [Visual observation] As seen in the case of Kasturi tobacco material, the color of the tobacco material at the end of the fermentation process (VG-AF) was significantly darker compared to the starting material (VG-BF). However, after 4 months of anaerobic fermentation (VG-T4), the Virginia tobacco material did not show the same darkness as the same amount of Kasturi tobacco after fermentation. This suggests that 4 months may not be sufficient to obtain complete fermentation of the Virginia tobacco material.

[0146] [Chemical analysis] In the following, when values ​​relating to a sample are mentioned, the given value represents the average of several values ​​obtained for each sample of the same type.

[0147] The behavior of lactic acid in tobacco materials over time is very similar to that depicted in Figures 1 and 2. Qualitatively, before fermentation, lactic acid is absent in all samples. After fermentation, variable amounts of lactic acid are present.

[0148] Figure 9 shows the evolution of total alkaloids (TA) during the fermentation process. These data confirm that alkaloids, especially nicotine (not shown), are not affected by anaerobic fermentation. The bacteria did not consume the major alkaloids as fermentation substrates.

[0149] On the other hand, reducing sugars were used as substrates by the fermentation bacteria, as depicted in Figure 10 and previously observed in Examples 1 and 2. Thus, approximately 60% of the reducing sugars (RS) were oxidized during the 8-month fermentation, changing from 18.3 percent (VG-BF) to 7.4 percent (VG-AF) dry weight (DW). A longer fermentation period may have led to a higher RS ​​degradation rate.

[0150] The means (n=6) and SDs are presented in Figures 9 and 10, as well as paired t-tests performed between BF and AF.

[0151] Further chemical analysis showed that the starting material (VG-BF) had an asparagine content of 262 micrograms per gram (ug / g) on ​​a dry weight basis. The same tobacco material after fermentation (8 months, VG-AF) had an asparagine content of 19 micrograms per gram (ug / g) on ​​a dry weight basis.

[0152] The starting material (VG-BF) had a glutamine content of 185 micrograms per gram (ug / g) on ​​a dry weight basis. The same tobacco material after fermentation (8 months, VG-AF) had a glutamine content of 12 micrograms per gram (ug / g) on ​​a dry weight basis.

Claims

1. 1. A method for processing tobacco material, said method comprising: fermenting said tobacco material to obtain a treated tobacco material, which (iii) incubating the tobacco material under anaerobic conditions; (iii) applying a pressure of 1,000 kilograms per square meter to 4,000 kilograms per square meter to the tobacco material; (iii) maintaining the moisture content of the tobacco material at an amount comprised between 25 weight percent and 40 weight percent of the total weight of the tobacco material; A method wherein said fermentation lasts for at least one month.

2. 10. The method of claim 1, a step of drying the tobacco material to obtain a dried tobacco material having a moisture content comprised between 5 percent and 10 percent of the total weight of the tobacco material.

3. 3. The method of claim 1 or claim 2, a method comprising the step of drying said tobacco material before fermentation.

4. 4. The method according to one or more of claims 1 to 3, comprising maintaining the temperature of the tobacco material at a temperature comprised between 25°C and 35°C.

5. 5. The method according to one or more of claims 1 to 4, a method comprising the step of rotating the tobacco material.

6. 6. The method according to one or more of claims 1 to 5, a method comprising securing said tobacco material within a moisture-retaining material.

7. 7. The method according to one or more of claims 1 to 6, a method comprising wetting the tobacco material in water prior to fermentation to achieve a moisture content of the tobacco material comprising 25 weight percent to 40 weight percent of the total weight of the tobacco material.

8. 8. The method of claim 1, wherein the amount of asparagine in the treated tobacco material is at least 50 percent lower than the amount of asparagine contained in the same tobacco material before treatment.

9. 9. The method of claim 1, wherein the amount of asparagine in the treated tobacco material is at least 50 percent lower than the amount of asparagine contained in the same tobacco material before treatment.

10. 10. The method according to one or more of claims 1 to 9, wherein the amount of reducing sugars in the treated tobacco material is at least 50 percent lower than the amount of reducing sugars contained in the same tobacco material before treatment.

11. A tobacco material comprising: less than 3 percent total reducing sugars on a total dry weight basis; - Tobacco material containing less than 300 milligrams / kilogram of asparagine on a total dry weight basis.

12. 12. The tobacco material according to claim 11, Tobacco material containing less than 70 milligrams / kilogram of glutamine on a total dry weight basis.

13. 13. The tobacco material according to claim 11 or claim 12, A tobacco material containing more than 10,000 milligrams / kilogram of total free amino acids on a total dry weight basis.

14. The tobacco material according to one or more of claims 11 to 13, wherein the tobacco material is dried.

15. An aerosol-generating article comprising a tobacco material according to one or more of claims 11 to 14.

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