EP3643184A1

EP3643184A1 - Method for producing tobacco flavor liquid, and tobacco flavor liquid

Info

Publication number: EP3643184A1
Application number: EP17920081.1A
Authority: EP
Inventors: Akane OGINO; Kenji Ito
Original assignee: Japan Tobacco Inc
Current assignee: Japan Tobacco Inc
Priority date: 2017-08-02
Filing date: 2017-08-02
Publication date: 2020-04-29
Also published as: WO2019026201A1; EP3643184A4

Abstract

A method of producing a tobacco flavor solution, comprising: a first heating step of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80 to 240°C; and a second heating step of heating the mixture at a temperature of 25 to 60°C after the first heating step.

Description

FIELD

The present invention relates to a method of producing a tobacco flavor solution, and a tobacco flavor solution produced by the method.

BACKGROUND OF THE INVENTION

It has been reported that a tobacco extract solution is prepared by extracting smoking flavor components from tobacco material such as leaf tobacco, and this is used as raw material for a flavor source of a tobacco product by applying it to cut tobacco or cigarette paper or by incorporating it into raw material slurry of reconstituted tobacco ( WO2007/052159 ). Alternatively, a tobacco extract solution is used as raw material for a tobacco flavor source to be contained in a liquid container of a non-heating type flavor inhaler, or as raw material for a tobacco flavor source to be added to a liquid aerosol source of a heating type flavor inhaler (Jpn. Pat. Appln. KOKAI Publication No. 2013-13394 ).
For example, it has been reported that a tobacco extract solution is prepared by extracting smoking flavor components such as vanillin, syringaldehyde, and pyrazine from tobacco stalks or tobacco roots, and used as raw material for a flavor source of a tobacco product ( WO2012/103435 ).
It is desirable that a tobacco extract solution exhibit storage stability for the duration of storage of a tobacco product so that it can provide an excellent smoking flavor to a user when used as raw material for the flavor source of a tobacco product.

SUMMARY

TECHNICAL PROBLEM

The present inventors conducted a study in which tobacco material is heated in an alkali aqueous solution to increase an amount of pyrazine derivatives contained in a tobacco extract solution, thereby increasing smoking flavor components of a tobacco extract. When the present inventors heated the tobacco material in the alkali aqueous solution, the amount of pyrazine derivatives contained in the tobacco extract solution increased, but after that, when they exposed the tobacco extract solution to a heat drying step in a conventional manner, the pyrazine derivatives disappeared (see Example 3 in Table 2 below). Therefore, the present inventors heated the tobacco material in the alkali aqueous solution and used the obtained tobacco extract solution as raw material for the flavor source of the tobacco product without exposing it to heat drying. Then, they faced the problem in which the smoking flavor changed after storage of the tobacco product (see Sample 2-2 in Table 3 below).
Thus, an object of the present invention is to provide a tobacco flavor solution that contains a large amount of pyrazine derivatives as smoking flavor components while containing only a small amount of unstable components that cause a change in smoking flavor during a storage period.

SOLUTION TO PROBLEM

The present inventors considered that the above-noted change in smoking flavor results from the fact that cyclotene, maltol and vanillin, which are flavor components contained in the tobacco extract solution, are unstable under alkaline conditions. The present inventors found that when tobacco material is heated in an alkali aqueous solution to increase an amount of pyrazine derivatives contained in a tobacco extract solution followed by heating again at a relatively low temperature, it is possible to significantly reduce the content of cyclotene, maltol and vanillin with little decrease in the increased content of pyrazine derivatives. The present inventors confirmed that a tobacco extract solution produced based on such knowledge does not cause a significant change in smoking flavor after storage for a certain period of time, leading to the completion of the present invention.
Specifically, according to one aspect of the present invention, there is provided a method of producing a tobacco flavor solution, comprising:

a first heating step of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80 to 240°C; and
a second heating step of heating the mixture at a temperature of 25 to 60°C after the first heating step.

According to another aspect of the present invention, there is provided a tobacco flavor solution obtainable by the above-mentioned method, the tobacco flavor solution comprising:

pyrazine derivatives such that a total content of pyrazine derivatives contained in the tobacco flavor solution is 0.4 mg or more per 1 g of the tobacco material; and
cyclotene, maltol and vanillin such that a total content of cyclotene, maltol and vanillin contained in the tobacco flavor solution is 0.05 mg or less per 1 g of the tobacco material.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide a tobacco flavor solution containing a large amount of pyrazine derivatives as smoking flavor components and containing only a small amount of unstable components that cause a change in smoking flavor during a storage period.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing a preferred embodiment of a method of the present invention;
FIG. 2 is a graph showing a relationship between number of days of a second heating step and a total content of pyrazine derivatives; and
FIG. 3 is a graph showing a relationship between number of days of a second heating step and a total content of cyclotene, maltol and vanillin.

DETAILED DESCRIPTION

Hereinafter, the present invention will be described, but the following description is for the purpose of detailed explanation of the present invention, and is not intended to limit the present invention.

<1. Method of Producing Tobacco Flavor Solution>

According to an embodiment, a method of producing a tobacco flavor solution includes:

According to a preferred embodiment, a method of producing a tobacco flavor solution includes:

a first heating step of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80 to 240°C;
a step of separating a liquid part from the mixture after the first heating step to obtain a tobacco extract solution; and
a second heating step of heating the separated tobacco extract solution at a temperature of 25 to 60°C.

A preferred embodiment is shown in FIG. 1.
In the first heating step, when the mixture containing the tobacco material and the alkali aqueous solution is heated, a mixture containing a tobacco extract solution and a tobacco residue is obtained, and pyrazine derivatives are extracted in the tobacco extract solution. During the first heating step, the pH of the mixture decreases.
In the second heating step, when the mixture containing the tobacco extract solution and the tobacco residue, or the separated tobacco extract solution, is heated, a mixture containing a tobacco flavor solution and a tobacco residue is obtained, and the total content of pyrazine derivatives in the tobacco flavor solution decreases very little as compared to that in the tobacco extract solution, whereas the total content of cyclotene, maltol and vanillin in the tobacco flavor solution significantly decreases as compared to that in the tobacco extract solution.
In this manner, it is possible to obtain a tobacco flavor solution containing a large amount of pyrazine derivatives as smoking flavor components and containing only a small amount of unstable components that cause a change in smoking flavor during a storage period.
In the present specification, a liquid obtained after the first heating step will be referred to as "a tobacco extract solution", while a liquid obtained after the second heating step will be referred to as "a tobacco flavor solution".
Hereinafter, a description will be given of the "first heating step", "separation step", and "second heating step" in this order.

[First Heating Step]

As tobacco material used in the method according to the present invention, cut tobacco which is ready to be incorporated into a tobacco product such as a smoking article or a flavor inhaler can be used. The "cut tobacco which is ready to be incorporated into a tobacco product" refers to cut tobacco which is ready to be incorporated into a tobacco product through various processes including a drying process of harvested tobacco leaves in a farm house, thereafter an aging process for one to several years in a leaf processing plant, and thereafter blending and cutting processes in a manufacturing plant.
As the cut tobacco, cut tobacco derived from any tobacco variety can be used. For example, cut tobacco derived from flue-cured tobacco, Burley tobacco, Oriental tobacco or the like can be used. As the cut tobacco, cut tobacco derived from a single variety may be used, or a mixture of cut tobacco derived from different varieties may be used.
The cut tobacco can include cut pieces of stemmed leaves, midribs, and reconstituted tobacco made from these raw materials (i.e., a tobacco material obtained by processing leaf scraps, cut tobacco scraps, midrib scraps, and fine powder generated in the plant processes into a reusable shape). The cut tobacco is preferably cut leaf tobacco.
In the first heating step, a mixture containing the tobacco material and the alkali aqueous solution and having a pH of 11 to 13 is heated at a temperature of 80 to 240°C. The pH of the mixture can be determined by measuring a pH of the liquid part of the mixture containing the tobacco material and the alkali aqueous solution.
The mixture preferably has a pH of 11.5 to 12.5. For the alkali aqueous solution, for example, a 0.1 to 0.5 mol/L potassium hydroxide aqueous solution, or a 0.1 to 0.5 mol/L sodium hydroxide aqueous solution can be used.
A ratio between the mass (g) of the tobacco material and the volume (mL) of the alkali aqueous solution is preferably 1:5 to 1:20, more preferably 1:7 to 1:15.
The first heating step can be performed at 80 to 240°C, preferably 120 to 200°C. The first heating step can be performed for, for example, 1 hour or more and less than 10 hours.
The first heating step preferably consists of:

heating step A of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80°C or higher and lower than 160°C, until the pH of the mixture becomes 10 or lower; and
heating step B of heating the mixture at a temperature of 160°C or higher and 240°C or lower for at least 30 minutes after the heating step A.

By performing the first heating step in two stages of the heating steps A and B, it is possible to efficiently synthesize pyrazine derivatives.
Preferably, the heating step A can be performed at a temperature of 120 to 150°C, and the heating step B can be performed at a temperature of 160 to 200°C.
For example, the heating step A can be performed for 30 minutes to 2 hours, and the heating step B can be performed for 30 minutes to 2 hours.
The first heating step can be performed generally for less than 10 hours, preferably 1 hour or more and less than 10 hours, more preferably 1 to 4 hours. That is, the total time of the heating steps A and B is generally less than 10 hours, preferably 1 hour or more and less than 10 hours, more preferably 1 to 4 hours. If the first heating step is performed for 10 hours or more, most substrates of the pyrazine derivatives (sugar, amino acid, protein, etc.) are used up, and the amount of pyrazine derivatives is less likely to increase, but rather the increased amount of pyrazine derivatives may decrease by heating.
During the heating step A, the pH decreases. The heating step A is performed until the pH of the mixture is 10 or less, preferably 8 to 10. The present inventors have experimentally demonstrated that the drop in pH occurring during the heating step A stops when the pH of the mixture drops to 10 or less. Such a stop state is considered to occur because most substrates of the pyrazine derivatives have been used up. Therefore, it is preferable that the heating step A be performed until the pH of the mixture becomes 10 or less, that is, until most of the substrates of the pyrazine derivatives are used up. Thereafter, by performing the heating step B by raising a reaction temperature, the synthesis reaction of pyrazine derivatives can be promoted.
The first heating step is desirably performed in a sealed container. When the first heating step is performed in a sealed container, the liquid amount of the mixture can be maintained after the heating step.
After the first heating step, a mixture containing the tobacco extract solution and the tobacco residue is obtained, and the content of pyrazine derivatives in the tobacco extract solution increases. In this specification, "pyrazine derivative" refers to aromatic alkylpyrazine in which at least one of four hydrogen atoms of pyrazine is substituted with an ethyl group or a methyl group, specific examples of which include 2-methylpyrazine, 2,5-dimethylpyrazine, 2,6-dimethylpyrazine, 2-ethylpyrazine, 2,3-dimethylpyrazine, 2-ethyl-5-methylpyrazine, 2-ethyl-6-methylpyrazine, 2,3,5-trimethylpyrazine, tetramethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, and 2-ethyl-3,5-dimethylpyrazine. Pyrazine derivatives are components that contribute to tobacco smoking flavor (specifically, fragrant smoking flavor).
After the first heating step, the mixture may be cooled to room temperature and then subjected to subsequent steps.

[Separation Step]

After the first heating step, a liquid part is separated from the mixture containing the tobacco extract solution and the tobacco residue to obtain a tobacco extract solution. This separation step is preferably performed, but may not be performed.
If the separation step is performed, the tobacco extract solution is subjected to the second heating step, and if not, the mixture containing the tobacco extract solution and the tobacco residue is subjected to the second heating step.

[Second Heating Step]

In the second heating step, the mixture containing the tobacco extract solution and the tobacco residue, or the separated tobacco extract solution, is heated at a temperature of 25 to 60°C. If the second heating step is performed at a temperature lower than 25°C, it is difficult to sufficiently reduce unstable components that cause a change in smoking flavor during a storage period. Further, if the second heating step is performed at a temperature exceeding 60°C, the amount of pyrazine derivatives increased by the first heating step is likely to decrease.
The second heating step can be performed preferably at a temperature of 30 to 50°C.
The second heating step can be performed for preferably 24 hours or longer, more preferably 24 to 720 hours, and still more preferably 24 to 72 hours.
The second heating step is desirably performed in a sealed container. When the second heating step is performed in a sealed container, the liquid amount of the mixture can be maintained after the heating step.
After the second heating step, the total content of cyclotene, maltol and vanillin in the tobacco extract solution can be significantly reduced with little decrease in the total content of pyrazine derivatives in the tobacco extract solution.
In this manner, it is possible to obtain a tobacco flavor solution preferably containing:

pyrazine derivatives such that the total content of pyrazine derivatives contained in the ultimately produced tobacco flavor solution is 0.4 mg or more per 1 g of the tobacco material as a starting material; and
cyclotene, maltol and vanillin such that the total content of cyclotene, maltol and vanillin contained in the ultimately produced tobacco flavor solution is 0.05 mg or less per 1 g of the tobacco material as a starting material.

It is possible to obtain a tobacco flavor solution more preferably containing:

pyrazine derivatives such that the total content of pyrazine derivatives contained in the ultimately produced tobacco flavor solution is 0.4 to 4 mg per 1 g of the tobacco material as a starting material; and
cyclotene, maltol and vanillin such that the total content of cyclotene, maltol and vanillin contained in the ultimately produced tobacco flavor solution is 0.05 mg or less per 1 g of the tobacco material as a starting material, or no cyclotene, maltol or vanillin.

Thus, the tobacco flavor solution obtained by the method of the present invention contains a large amount of pyrazine derivatives and only a small amount or none of cyclotene, maltol and vanillin. Therefore, such a tobacco flavor solution, when used as raw material for a flavor source of a tobacco product, can give a user a rich smoking flavor by virtue of containing a large amount of pyrazine derivatives, and can prevent cyclotene, maltol and vanillin from changing during storage of the tobacco product to cause a change in smoking flavor by virtue of containing a small amount or none of cyclotene, maltol and vanillin.

<2. Tobacco Product>

As shown in the examples described later, the increased amount of pyrazine derivatives did not decrease when the tobacco extract solution obtained in the first heating step was exposed to the heating step at 40°C, whereas the increased amount of pyrazine derivatives decreased when the tobacco extract solution was exposed to the heat drying step at 80°C (see Example 1 in Table 1, and Example 3 in Table 2 below). Therefore, there is a need to use the tobacco flavor solution produced according to the method of the present invention in a tobacco product as raw material for a flavor source of the tobacco product (e.g., flavor inhaler) without being exposed to high temperatures that cause reduction of pyrazine derivatives. Conventionally, when incorporated into a tobacco product such as smokeless tobacco (snus) or cigarettes, a tobacco flavor solution is put back into a tobacco residue, and this is exposed to a heat drying step at, for example, 80 to 120°C, and then incorporated into a tobacco product; however, in the present invention, the tobacco flavor solution should not be exposed to such a heat drying step.
Specifically, it is preferable that the tobacco extract solution prepared to contain a large amount of pyrazine derivatives after the first heating step not be placed under a temperature condition exceeding 60°C until it turns into a tobacco flavor solution through the second heating step and is used in a tobacco product as raw material for a flavor source of the tobacco product and used by a user. More specifically, it is preferable that the tobacco extract solution prepared to contain a large amount of pyrazine derivatives after the first heating step be placed under a temperature condition of 60°C or less, specifically -30°C to +60°C until it turns into a tobacco flavor solution through the second heating step and is used in a tobacco product as raw material for a flavor source of the tobacco product and used by a user.
If the tobacco extract solution is not placed under a temperature condition exceeding 60°C until it turns into a tobacco flavor solution through the second heating step and is used in a tobacco product as raw material for a flavor source of the tobacco product and used by the user, the tobacco flavor solution can stably contain pyrazine derivatives without reducing them even after storage, and thus a tobacco product containing such a tobacco flavor solution as raw material for a flavor source can provide a user with an excellent smoking flavor when used.
While it is preferable that the tobacco extract solution and the tobacco flavor solution not be placed under temperature conditions exceeding 60°C, the tobacco flavor solution produced may be neutralized before being applied to the tobacco product.
The tobacco flavor solution produced according to the method of the present invention can be used as raw material for producing a flavor source applied to, for example, a non-heating type flavor inhaler, or a heating type flavor inhaler.
A "non-heating type flavor inhaler" refers to an inhaler which allows a user to savor a flavor of a tobacco flavor source (e.g., cut tobacco or tobacco flavor solution) through inhalation without heating the tobacco flavor source. Examples of the non-heating type flavor inhaler include: a flavor inhaler which comprises an inhalation holder and a tobacco flavor source filled in an air flow path of the inhalation holder (see, for example, WO2010/095659 ).
A "heating type flavor inhaler" refers to an inhaler which heats a tobacco flavor source without burning it and allows a user to savor a flavor of the heated tobacco flavor source through inhalation. Examples of the heating type flavor inhaler include: a carbonaceous heat source type inhalation article that heats a tobacco flavor source with combustion heat of a carbon heat source (see, for example, WO2006/073065 ); an electrical heating type inhalation article provided with an inhaler and a heating device for electrically heating the inhaler (see, for example, WO2010/110226 ); and a liquid atomization type inhalation article that atomizes, by heating, a liquid aerosol source containing a tobacco flavor source (see, for example, WO2015/046385 ).
The tobacco flavor solution produced according to the method of the present invention may be used in the "non-heating type flavor inhaler" as raw material for producing a liquid flavor source incorporated alone in a liquid container, or as raw material for producing a flavor source put in a pod by mixing with other material. Alternatively, the tobacco flavor solution produced according to the method of the present invention may be used in the "heating type flavor inhaler" as raw material for producing a liquid flavor source incorporated alone in a liquid container, as raw material for producing a flavor source put in a pod by mixing with other material, or as raw material for producing a flavor source used by mixing with an aerosol source liquid (e.g., glycerin).

<3. Preferred Embodiments>

The preferred embodiments of the present invention are summarized below.
As described above, a method of producing a tobacco flavor solution according to an embodiment, comprises:

As described above, a method of producing a tobacco flavor solution according to a preferred embodiment, comprises:

According to a more preferred embodiment, in any one of the above-described embodiments, the first heating step consists of:

heating step A of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80°C or higher and lower than 160°C until the pH of the mixture becomes 10 or lower; and
heating step B of heating the mixture at a temperature of 160°C or higher and 240°C or lower for at least 30 minutes after the heating step A.

According to a more preferred embodiment, in any one of the above-described embodiments, the heating step A is performed at a temperature of 120 to 150°C.
According to a more preferred embodiment, in any one of the above-described embodiments, the heating step B is performed at a temperature of 160 to 200°C.
According to a more preferred embodiment, in any one of the above-described embodiments, the heating step A is performed for 30 minutes to 2 hours.
According to a more preferred embodiment, in any one of the above-described embodiments, the heating step B is performed for 30 minutes to 2 hours.
According to a more preferred embodiment, in any one of the above-described embodiments, the first heating step is performed for less than 10 hours.
According to a more preferred embodiment, in any one of the above-described embodiments, the first heating step is performed for 1 hour or more and less than 10 hours, preferably 1 to 4 hours.
According to a more preferred embodiment, in any one of the above-described embodiments, the tobacco material is cut tobacco, preferably cut leaf tobacco.
According to a more preferred embodiment, in any one of the above-described embodiments, the mixture has a pH of 11.5 to 12.5.
According to a more preferred embodiment, in any one of the above-described embodiments, the alkali aqueous solution is a 0.1 to 0.5 mol/L potassium hydroxide aqueous solution, or a 0.1 to 0.5 mol/L sodium hydroxide aqueous solution.
According to a more preferred embodiment, in any one of the above-described embodiments, a ratio between mass (g) of the tobacco material and volume (mL) of the alkali aqueous solution is 1:5 to 1:20, preferably 1:7 to 1:15.
According to a more preferred embodiment, in any one of the above-described embodiments, the heating step A is performed until the pH of the mixture becomes 8 to 10.
According to a more preferred embodiment, in any one of the above-described embodiments, the first heating step is performed in a sealed container.
According to a more preferred embodiment, in any one of the above-described embodiments, the second heating step is performed for 24 hours or more.
According to a more preferred embodiment, in any one of the above-described embodiments, the second heating step is performed for 24 to 720 hours, preferably 24 to 72 hours.
According to a more preferred embodiment, in any one of the above-described embodiments, the second heating step is performed at a temperature of 30 to 50°C.
According to a more preferred embodiment, in any one of the above-described embodiments, the second heating step is performed in a sealed container.
According to a more preferred embodiment, in any one of the above-described embodiments, the tobacco extract solution obtained after the first heating step is not placed under a temperature condition exceeding 60°C until it turns into a tobacco flavor solution through the second heating step and is used in a tobacco product as raw material for a flavor source of the tobacco product and used by a user.
According to a more preferred embodiment, in any one of the above-described embodiments, the tobacco extract solution obtained after the first heating step is placed under a temperature condition of -30°C to +60°C until it turns into a tobacco flavor solution through the second heating step and is used in a tobacco product as raw material for a flavor source of the tobacco product and used by a user.
A tobacco flavor solution according to a preferred embodiment is obtainable by the method according to any one of the above-described embodiments, the tobacco flavor solution comprising:

A tobacco flavor solution according to a more preferred embodiment is obtainable by the method according to any one of the above-described embodiments, the tobacco flavor solution comprising:

pyrazine derivatives such that a total content of pyrazine derivatives contained in the tobacco flavor solution is 0.4 to 4 mg per 1 g of the tobacco material; and
cyclotene, maltol and vanillin such that a total content of cyclotene, maltol and vanillin contained in the tobacco flavor solution is 0.05 mg or less per 1 g of the tobacco material, or no cyclotene, maltol or vanillin.

Examples

1. Production of Tobacco Flavor Solution

For tobacco material, cut leaf tobacco (a mixture of American Burley leaves and domestic flue-cured leaves (9:1 mass ratio)) was used.
The tobacco material was heated by sequentially performing heating step A and heating step B (first heating step) as follows.
Heating step A: In a stainless steel pressure tight container, 10 mL of a 0.25 mol/L potassium hydroxide aqueous solution (pH 12) was added to 1 g of the tobacco material to obtain a mixture. The pH of the mixture immediately after the addition of potassium hydroxide was 12. The resulting mixture was heated at 120°C for 1 hour using a jacket heater. That is, the resulting mixture was heated at 120°C until the pH was 10 or less.
Heating step B: After the heating step A, the mixture was heated at 180°C for 1 hour.
The heating steps A and B were performed in a sealed container (capacity: 100 mL) in order to maintain the liquid amount of the mixture.
After the heating step B, the residue was removed from the mixture by suction filtration to obtain a tobacco extract solution.
The tobacco extract solution was placed in a glass bottle with a lid, and heated at 40°C in a thermostatic bath (second heating step). The second heating step was performed for 1 day, 3 days, 7 days, 14 days, or 28 days. The second heating step was also performed in a sealed container (capacity: 10 mL) in order to maintain the liquid amount of the tobacco extract solution. In this manner, a tobacco flavor solution was obtained.

The tobacco flavor solution was obtained in the same manner as in Example 1, except that the second heating step was performed by placing the tobacco extract solution in a glass bottle with a lid and heating it at 80°C in a thermostatic bath, and that the second heating step was performed for 1 day, 3 days, or 7 days.

The tobacco flavor solution was obtained in the same manner as in Example 1, except that the second heating step was performed by filtering the tobacco extract solution with a filter paper and then heat-drying it at 80°C for 1 hour in a thermostatic bath. In Example 3, the heat drying was performed in an open container, not in a glass bottle with a lid (i.e., a sealed container), and therefore, the liquid amount of the tobacco flavor solution obtained in Example 3 was smaller than that of the tobacco extract solution.

2. Evaluation of Content of Flavor Components

At the start of the second heating step (Day 0), the content of the flavor components in the tobacco extract solution was measured.
In Example 1, the content of the flavor components in the tobacco flavor solution was measured 1 day, 3 days, 7 days, 14 days, and 28 days after the start of the second heating step. In Example 2, the content of the flavor components in the tobacco flavor solution was measured 1 day, 3 days, and 7 days after the start of the second heating step. In Example 3, the content of the flavor components in the tobacco flavor solution was measured after the heat drying at 80°C for 1 hour.
The measurement was performed in the following manner.
50 µL of the internal standard (4-bromophenethyl alcohol) and 80 mL of water were added to 1.0 mL of the tobacco flavor solution to prepare a measurement solution. The measurement solution was adjusted to have pH 2 or 9 using hydrochloric acid or a sodium hydroxide aqueous solution. Thereafter, each of the pH 2 measurement solution and the pH 9 measurement solution was applied to an Oasis HLB cartridge manufactured by WATERS. Subsequently, the cartridge was washed with 20 mL of water, and the supported substances were eluted with diethyl ether. The supernatant of the eluate was subjected to GC/MS analysis. As the column, DB-FFAP manufactured by Agilent was used, and the oven was heated to 60 to 240°C. MS detection was performed in the SIM mode.

The results of Example 1 are shown in Table 1 and FIGS. 2 and 3, and the results of Examples 2 and 3 are shown in Table 2.

[Table 1]

	Example 1
Time of second heating step	0 Days	1 Day	3 Days	7 Days	14 Days	28 Days
2-Methylpyrazine	0.099	0.096	0.096	0.096	0.095	0.087
2,5-Dimethylpyrazine	0.081	0.077	0.079	0.078	0.077	0.070
2,6-Dimethylpyrazine	0.084	0.079	0.081	0.081	0.080	0.074
2-Ethylpyrazine	0.013	0.012	0.012	0.012	0.012	0.010
2,3-Dimethylpyrazine	0.016	0.018	0.018	0.018	0.015	0.016
2-Ethyl-5-methylpyrazine	0.036	0.035	0.034	0.034	0.033	0.030
2-Ethyl-6-methylpyrazine	0.010	0.010	0.010	0.009	0.009	0.008
2,3,5-Trimethylpyrazine	0.085	0.084	0.083	0.081	0.081	0.076
Tetramethylpyrazine	0.017	0.017	0.017	0.016	0.016	0.015
2-Ethyl-3,6-dimethylpyrazine	0.010	0.010	0.009	0.009	0.009	0.008
2-Ethyl-3,5-dimethylpyrazine	0.012	0.012	0.011	0.011	0.011	0.011
Total of pyrazine derivatives	0.462	0.449	0.449	0.444	0.441	0.405
Cyclotene	0.211	0.005	0.001	0.001	0.001	0.001
Maltol	0.020	0.016	0.012	0.009	0.007	0.006
Vanillin	0.032	0.028	0.021	0.012	0.006	0.002
Total of cyclotene, maltol and vanillin	0.263	0.049	0.034	0.022	0.014	0.009

[Table 2]

	Example 2				Example 3
Time of second heating step	0 Days	1 Day	3 Days	7 Days	0 Hours	1 Hour
2-Methylpyrazine	0.099	0.088	0.076	0.053	0.099	0.000
2,5-Dimethylpyrazine	0.081	0.069	0.051	0.029	0.081	0.000
2,6-Dimethylpyrazine	0.084	0.073	0.057	0.036	0.084	0.000
2-Ethylpyrazine	0.013	0.009	0.006	0.002	0.013	0.000
2,3-Dimethylpyrazine	0.016	0.017	0.013	0.009	0.016	0.000
2-Ethyl-5-methylpyrazine	0.036	0.025	0.014	0.004	0.036	0.000
2-Ethyl-6-methylpyrazine	0.010	0.006	0.002	0.000	0.010	0.000
2,3,5-Trimethylpyrazine	0.085	0.070	0.051	0.030	0.085	0.000
Tetramethylpyrazine	0.017	0.011	0.005	0.000	0.017	0.000
2-Ethyl-3,6-dimethylpyrazine	0.010	0.005	0.002	0.000	0.010	0.000
2-Ethyl-3,5-dimethylpyrazine	0.012	0.009	0.006	0.003	0.012	0.000
Total of pyrazine derivatives	0.462	0.384	0.282	0.165	0.462	0.000
Cyclotene	0.211	0.003	0.002	0.001	0.211	0.043
Maltol	0.020	0.006	0.005	0.005	0.020	0.017
Vanillin	0.032	0.003	0.001	0.000	0.032	0.048
Total of cyclotene, maltol and vanillin	0.263	0.011	0.007	0.007	0.263	0.108

In Tables 1 and 2 and FIGS. 2 and 3, the content of the flavor component is represented as a content (mg) per 1 g of the tobacco material.
In Example 1, after 28 days from the start of the second heating step (heating at 40°C), the total content of pyrazine derivatives in the tobacco flavor solution maintained approximately 88% by mass of the initial content with little decrease, whereas the total content of cyclotene, maltol and vanillin in the tobacco flavor solution decreased to approximately 3% by mass of the initial content (see Table 1 and FIGS. 2 and 3).
In Example 2, after 7 days from the start of the second heating step (heating at 80°C), the total content of pyrazine derivatives in the tobacco flavor solution decreased to approximately 36% by mass of the initial content, and the total content of cyclotene, maltol and vanillin in the tobacco flavor solution decreased to approximately 3% by mass of the initial content (see Table 2).
In Example 3, when the tobacco extract solution was heat-dried at 80°C for 1 hour, the pyrazine derivatives in the tobacco flavor solution disappeared, and the total content of cyclotene, maltol and vanillin in the tobacco flavor solution decreased to approximately 41% by mass of the initial content (see Table 2).
When the tobacco extract solution was allowed to stand at room temperature (approximately 22°C) for 28 days without being exposed to the second heating step, the total content of pyrazine derivatives could be maintained, but the total content of cyclotene, maltol and vanillin could not be reduced sufficiently.
These results show that when the tobacco material is heated in the alkali aqueous solution to increase the amount of pyrazine derivatives contained in the tobacco extract solution followed by heating again at a relatively low temperature according to the method of the present invention, it is possible to significantly reduce the content of cyclotene, maltol and vanillin with little decrease in the increased content of pyrazine derivatives.

3. Sensory Evaluation

According to the method described in Example 1, the first heating step was performed and then the second heating step was performed at 40°C for 3 days to produce a tobacco flavor solution. Immediately after production, 2 mL of the tobacco flavor solution was placed in a glass bottle with a lid (capacity: 10 mL) to prepare Sample 1-1 for sensory evaluation. Sample 1-1 was stored at room temperature (22°C) for 24 hours, and this was designated as Sample 1-2 for sensory evaluation.
According to the method described in Example 1, the first heating step was performed to produce a tobacco extract solution. Immediately after production, 2 mL of the tobacco extract solution was placed in a glass bottle with a lid (capacity: 10 mL) to prepare Sample 2-1 for sensory evaluation. Sample 2-1 was stored at room temperature (22°C) for 24 hours, and this was designated as Sample 2-2 for sensory evaluation.
According to the method described in Example 3, the first heating step was performed to obtain a tobacco extract solution, and then the tobacco extract solution (2 mL) was filtered with a filter paper followed by heat drying at 80°C for 1 hour, thereby producing a tobacco flavor solution. Immediately after production, a tobacco flavor solution (i.e., a tobacco flavor solution obtained from 2 mL of the tobacco extract solution) was placed in a glass bottle with a lid (capacity: 10 mL) to prepare Sample 3-1 for sensory evaluation.
Immediately after preparation of the samples, sensory evaluation was conducted by five professional panelists. The panelists evaluated each sample by removing the lid of the glass bottle and sniffing the flavor.
For Samples 1-1, 2-1 and 3-1, the panelists conducted evaluation by commenting on the flavor characteristics. For Sample 1-2, it was evaluated whether there was a change in flavor as compared to Sample 1-1. Similarly, for Sample 2-2, it was evaluated whether there was a change in flavor as compared to Sample 2-1.

The results of sensory evaluation are shown in Table 3.

[Table 3]

Sample		Sensory evaluation
Tobacco flavor solution produced in Example 1	Sample 1-1 (before storage)	Fruity
		Western liquor-like
		Nutty
	Sample 1-2 (after storage)	No change in flavor as compared to Sample 1-1
Tobacco extract solution produced in Example 1	Sample 2-1 (before storage)	Fruity but lack of complexity
Tobacco extract solution produced in Example 1	Sample 2-2 (after storage)	Reduction in fruitiness as compared to Sample 2-1
Tobacco flavor solution produced in Example 3	Sample 3-1 (before storage)	Light flavor

The tobacco flavor solution of Sample 1-1 had an excellent flavor. When Sample 1-2 was prepared by storing Sample 1-1, Sample 1-2 maintained the excellent flavor of Sample 1-1.
On the other hand, the tobacco flavor solution of Sample 2-1 had a fruity flavor but lacked a flavor complexity as compared to Sample 1-1. When Sample 2-2 was prepared by storing Sample 2-1, Sample 2-2 had a reduced fruity flavor and did not maintain the flavor of Sample 2-1.
The tobacco flavor solution of Sample 3-1 had a light flavor.
These results show that when the tobacco material is heated in the alkali aqueous solution followed by heating again at a relatively low temperature according to the method of the present invention, it is possible to obtain a tobacco flavor solution with an excellent flavor even after storage.
In addition, the results of the above-mentioned "Evaluation of Content of Flavor Components" and "Sensory Evaluation" show the following. According to the method of the present invention, it is possible to provide a tobacco flavor solution containing a large amount of pyrazine derivatives as smoking flavor components and containing only a small amount of cyclotene, maltol and vanillin (i.e., unstable components causing a change in smoking flavor during the storage period). When such a tobacco flavor solution is used as raw material for a flavor source of a tobacco product, it is possible to provide a rich smoking flavor by virtue of containing a large amount of pyrazine derivatives, and to prevent cyclotene, maltol and vanillin from changing during storage of the tobacco product to cause a change in smoking flavor by virtue of containing only a small amount of cyclotene, maltol and vanillin.

Claims

A method of producing a tobacco flavor solution, comprising:
a first heating step of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80 to 240°C; and

a second heating step of heating the mixture at a temperature of 25 to 60°C after the first heating step.
The method according to claim 1,
wherein the first heating step consists of:
heating step A of heating a mixture containing a tobacco material and an alkali aqueous solution and having a pH of 11 to 13, at a temperature of 80°C or higher and lower than 160°C until the pH of the mixture becomes 10 or lower; and

heating step B of heating the mixture at a temperature of 160°C or higher and 240°C or lower for at least 30 minutes after the heating step A.
The method according to claim 2, wherein the heating step A is performed at a temperature of 120 to 150°C, and the heating step B is performed at a temperature of 160 to 200°C.
The method according to claim 2 or 3, wherein the heating step A is performed for 30 minutes to 2 hours, and the heating step B is performed for 30 minutes to 2 hours.
The method according to any one of claims 1 to 3, wherein the first heating step is performed for less than 10 hours.
The method according to any one of claims 1 to 3 and 5, wherein the first heating step is performed for 1 hour or more and less than 10 hours.
The method according to any one of claims 1 to 6, wherein the second heating step is performed for 24 hours or more.
The method according to any one of claims 1 to 7, wherein the second heating step is performed for 24 to 720 hours.
The method according to any one of claims 1 to 8, further comprising separating a liquid part from the mixture to obtain a tobacco extract solution after the first heating step,
wherein the second heating step is a step of heating the separated tobacco extract solution at a temperature of 25 to 60°C.
The method according to any one of claims 1 to 9, wherein the second heating step is performed at a temperature of 30 to 50°C.
A tobacco flavor solution obtainable by the method according to any one of claims 1 to 10, the tobacco flavor solution comprising:
pyrazine derivatives such that a total content of pyrazine derivatives contained in the tobacco flavor solution is 0.4 mg or more per 1 g of the tobacco material; and

cyclotene, maltol and vanillin such that a total content of cyclotene, maltol and vanillin contained in the tobacco flavor solution is 0.05 mg or less per 1 g of the tobacco material.