Method for preparing fresh tobacco leaves and prepared tobacco leaves

Abstract

The invention relates to a method for preparing fresh tobacco leaves and prepared tobacco leaves. The method comprises the following steps: withering fresh tobacco leaves to obtain first tobacco leaves; the moisture content of the first tobacco leaves is 53 wt%-57 wt%; the first tobacco leaves are subjected to water insulation steaming treatment through water vapor, and second tobacco leaves are obtained; and the second tobacco leaves are sequentially fermented and dried. In the preparation method of the fresh tobacco leaves, the withering treatment, the steaming treatment, the fermentation treatment and the drying treatment are sequentially performed, and the moisture content of the withered tobacco leaves is controlled, so that the tobacco leaves with relatively high content of aroma-like substances and relatively low content of macromolecular substances such as starch, protein and plastid pigment in the tobacco leaves can be obtained; the tobacco leaf also has the characteristic note of honey sweet fragrance.

Description

Technical Field

[0001] The invention relates to the technical field of tobacco processing, in particular to a method for curing fresh tobacco leaves and the cured tobacco leaves. Background Art

[0002] The main method of curing fresh tobacco leaves is intensive baking, which essentially means that the tobacco leaves turn yellow, fragrant and dry by controlling the temperature and humidity of the equipment. Tobacco leaf curing is an optimized combination and integration of multiple related technologies. It requires accurate judgment of the maturity of tobacco leaves and timely harvesting, and then judging their baking characteristics and baking parameters according to the quality of fresh leaves. Among them, timely harvesting of tobacco leaves at maturity is the basis of curing tobacco leaves and the key to highlighting the quality of tobacco leaves formed in the field through the baking process.

[0003] According to the preparation method, there are four basic types of tobacco: sun-dried tobacco, air-dried tobacco, smoked tobacco, and flue-cured tobacco. It is a process of dehydrating and drying tobacco leaves and causing physical and chemical changes through different means. In the traditional flue-cured tobacco preparation technology, the three-stage baking process is mainly used. A detailed discussion has been carried out on tobacco leaf baking equipment, the formation mechanism of tobacco leaf baking quality, and the standard technology of tobacco leaf baking. An intensive baking process for improving quality and aroma has been established with "low temperature and medium humidity to slowly turn yellow, medium humidity to fix color and slow heating, variable speed ventilation to slowly remove moisture, stable time at key stages, and light breeze to dry the tendons to preserve aroma" as the core. The maturity of tobacco leaves harvested and the flue-cured tobacco preparation process determine the shortcomings of flue-cured tobacco, which has a relatively fixed style and a relatively single aroma, and the process improvements for flue-cured tobacco cannot change the essence of the aroma and fragrance of tobacco leaves. Summary of the invention

[0004] Based on this, it is necessary to provide a method for curing fresh tobacco leaves, wherein the cured tobacco leaves obtained by the curing method have a high content of polyphenol aroma substances and a good aroma. Furthermore, a cured tobacco leaf is provided.

[0005] In a first aspect of the present application, a method for preparing fresh tobacco leaves is provided, comprising the following steps:

[0006] The fresh tobacco leaves are withered to obtain first tobacco leaves; the moisture content of the first tobacco leaves is 53wt% to 57wt%;

[0007] steaming the first tobacco leaves to obtain second tobacco leaves;

[0008] The second tobacco leaves are subjected to fermentation treatment and drying treatment in sequence.

[0009] In the above-mentioned method for preparing fresh tobacco leaves, withering treatment, steaming treatment, fermentation treatment and drying treatment are carried out in sequence, and the moisture content of the tobacco leaves after withering treatment is controlled to obtain tobacco leaves with a high content of aroma substances and a low content of macromolecular substances such as starch, protein, plastid pigments in the tobacco leaves; the tobacco leaves also have a characteristic aroma of sweet honey. Among them, by controlling the moisture content in the tobacco leaves after withering treatment, the content of macromolecular substances such as starch, protein, plastid pigments in the tobacco leaves can be reduced, and the quality of the tobacco leaves can be improved; further, by steaming the tobacco leaves after withering, the damage to the leaf cells can be reduced and the content of polyphenol aroma substances can be increased; and then the fermentation treatment and drying treatment steps are coordinated to improve the smoking quality of the tobacco leaves, and the tobacco leaves have a characteristic aroma of sweet honey.

[0010] In some embodiments, the steaming time is 8 min to 12 min.

[0011] In some embodiments, the withering treatment is carried out in a withering machine, and during the withering treatment, the dry bulb temperature of the withering machine is set to 38°C~39°C, and the wet bulb temperature is set to 35°C~36°C.

[0012] In some embodiments, the fermentation temperature is 40°C to 45°C.

[0013] In some embodiments, the relative humidity of the fermentation process is 80% to 85%.

[0014] In some embodiments, the fermentation treatment time is 10h~15h.

[0015] In some embodiments, during the fermentation process, the second tobacco leaves are stacked together, and the stacking thickness of the second tobacco leaves is 4.5 cm to 5.5 cm.

[0016] In some embodiments, the drying step comprises:

[0017] The drying equipment is preheated first, and after the temperature in the drying equipment reaches a first set temperature, the tobacco leaves to be dried are placed in the drying equipment for a first drying treatment; the first set temperature is 80°C to 90°C; and the time for the first drying treatment is 10min to 20min.

[0018] In some embodiments, after the first drying process, the drying process comprises:

[0019] The aroma machine is preheated first, and after the temperature of the aroma machine reaches a second set temperature, the tobacco leaves after the first drying treatment are placed in the aroma machine for a second drying treatment; the second set temperature is 100°C~110°C.

[0020] A second aspect of the present application provides a cured tobacco leaf, which is prepared according to the curing method described in the first aspect. DETAILED DESCRIPTION

[0021] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0023] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0024] In one embodiment of the present application, a method for preparing fresh tobacco leaves is provided, comprising the following steps S10 to S40:

[0025] S10, withering the fresh tobacco leaves to obtain first tobacco leaves; the moisture content of the first tobacco leaves is 53wt%-57wt%.

[0026] S20, steaming the first tobacco leaves with water vapor to obtain second tobacco leaves.

[0027] S30, fermenting the second tobacco leaf.

[0028] S40, drying the fermented tobacco leaves.

[0029] Herein, moisture content refers to the mass content of water.

[0030] In the above-mentioned method for preparing fresh tobacco leaves, withering treatment, steaming treatment, fermentation treatment and drying treatment are carried out in sequence, and the moisture content of the tobacco leaves after withering treatment is controlled to obtain a tobacco leaf with a high content of aroma substances and a low content of macromolecular substances such as starch, protein, plastid pigments in the tobacco leaves; the tobacco leaves also have a characteristic aroma of sweet honey. Among them, by controlling the moisture content in the tobacco leaves after withering treatment, the content of macromolecular substances such as starch, protein, plastid pigments in the tobacco leaves can be reduced, and the quality of the tobacco leaves can be improved; further, by steaming the tobacco leaves after withering, the damage to the leaf cells can be reduced and the content of polyphenol aroma substances can be increased; and then the fermentation treatment and drying treatment steps are coordinated to improve the smoking quality of the tobacco leaves, and the tobacco leaves have a characteristic aroma of sweet honey.

[0031] As an example, the moisture content in the first tobacco leaf can be 53wt%, 54wt%, 54.5wt%, 55wt%, 55.5wt%, 56wt%, 56.5wt% or 57wt%. Furthermore, the moisture content in the first tobacco leaf can be a range value consisting of any two of the above point values ​​as end values. By controlling the moisture content in the first tobacco leaf, macromolecular substances such as starch, protein, plastid pigments in the tobacco leaf can be fully degraded. Too low moisture content in tobacco leaves will lead to a significant reduction in the content of polyphenols such as chlorogenic acid and rutin; too high moisture content in tobacco leaves will lead to insufficient degradation of starch and plastid pigments.

[0032] Furthermore, the moisture content in the first tobacco leaf is 54.5wt%~55.5wt%.

[0033] More preferably, the moisture content in the first tobacco leaf is 55wt%.

[0034] In some embodiments, the withering treatment time is 8 hours to 12 hours. It can be understood that the moisture content of the first tobacco leaf after withering can be controlled by controlling the withering treatment time. The longer the withering treatment time, the lower the moisture content of the first tobacco leaf obtained.

[0035] In some embodiments, the withering process is carried out in a withering machine.

[0036] In some embodiments, during the withering process, the dry bulb temperature in the withering machine is set to 38°C~39°C; the wet bulb temperature is set to 35°C~36°C.

[0037] In some embodiments, when withering, the fresh tobacco leaves need to be braided into rods and then evenly hung in a withering machine for withering. During the process, the state of the tobacco leaves and the withering condition need to be frequently observed. If uneven withering occurs, the position of the tobacco leaf hanging rod needs to be adjusted in time.

[0038] In some embodiments, the steaming time is 8 min to 12 min. As an example, the steaming time can be 8 min, 8.5 min, 9 min, 9.5 min, 10 min, 10.5 min, 11 min, 11.5 min or 12 min. Further, the steaming time can be a range value consisting of any two of the above point values ​​as end values.

[0039] Furthermore, the time of the steaming process is 9 minutes to 11 minutes.

[0040] In some embodiments, the steaming process can be performed in a steamer.

[0041] In some embodiments, the step of steaming in a steamer comprises:

[0042] Place the first tobacco leaf on the steaming bamboo strips of the steamer;

[0043] Water is added to the steamer, and then heated. After the steam is generated in the steamer, the steaming bamboo strips carrying the first tobacco leaves are placed in the steam to steam the first tobacco leaves. After the steaming is completed, the tobacco leaves are taken out to obtain second tobacco leaves.

[0044] In some embodiments, the fermentation process is performed when the temperature of the second tobacco leaves is lowered to room temperature.

[0045] In some embodiments, the temperature of the fermentation treatment is 40°C to 45°C. As an example, the temperature of the fermentation treatment can be 40°C, 41°C, 42°C, 43°C, 44°C or 45°C. Furthermore, the temperature of the fermentation treatment can be a range value consisting of any two of the above point values ​​as end values. Preferably, the temperature of the fermentation treatment is 40°C to 42°C. By controlling the fermentation temperature, the content of sugar substances such as total sugar, reducing sugar, starch, etc. in the tobacco leaves can be regulated. The fermentation temperature affects the microbial activity of the tobacco leaf fermentation process. The microorganisms are highly active within the above range and consume more sugar substances. Therefore, the starch content in the tobacco leaves is lower, which also leads to the degradation of some macromolecular substances and the increase of the aroma substance content, thereby improving the smoking quality.

[0046] In some embodiments, the relative humidity of the fermentation process is 80% to 85%. As an example, the relative humidity of the fermentation process can be 80%, 81%, 82%, 83%, 84% or 85%. Further, the relative humidity of the fermentation process can be a range value consisting of any two of the above point values ​​as end values. Preferably, the relative humidity of the fermentation process is 80% to 82%.

[0047] In some embodiments, the fermentation process is carried out in a fermentation box, and the relative humidity control of the fermentation process can be achieved by automatic humidification of the fermentation box. During the automatic humidification process, fresh air is automatically added every 10 minutes.

[0048] In some embodiments, the fermentation time is 10 hours to 15 hours. As an example, the fermentation time can be 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours. Further, the fermentation time can be a range value consisting of any two of the above point values ​​as end values. Preferably, the fermentation time is 12 hours to 14 hours.

[0049] In some embodiments, during the fermentation process, the second tobacco leaves are stacked together, and the stacking thickness of the second tobacco leaves is 4.5 cm to 5.5 cm.

[0050] In some embodiments, the fermentation process is performed in a fermentation frame.

[0051] In some embodiments, during the fermentation process, 1 to 2 air holes with a diameter of 10 cm to 15 cm are left in the stacked layer formed by the second smoke. The air holes penetrate the upper end and the bottom end of the stacked layer. The air holes are provided to facilitate heat dissipation and ventilation to ensure sufficient reaction during the fermentation process.

[0052] In some embodiments, the drying process includes step S41.

[0053] S41, preheating the drying equipment first, and after the temperature in the drying equipment reaches a first set temperature, placing the tobacco leaves to be dried in the drying equipment for a first drying treatment.

[0054] In some embodiments, the first set temperature is 80°C to 90°C. It is understood that the first set temperature is also the temperature of the first drying. As an example, the first set temperature can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C or 90°C. Further, the first set temperature can be a range value consisting of any two of the above point values ​​as end values. Preferably, the first set temperature can be 84°C to 86°C. More preferably, the first set temperature is 85°C.

[0055] In some embodiments, the first drying process lasts for 10 to 20 minutes. Further, the first drying process lasts for 14 to 16 minutes.

[0056] In some embodiments, the above drying process, after the first drying process, further includes step S42.

[0057] S42, preheating the aroma machine first, and after the temperature of the aroma machine reaches a second set temperature, placing the tobacco leaves after the first drying treatment in the aroma machine for a second drying treatment.

[0058] In some embodiments, the second set temperature is 100°C to 110°C. It can be understood that the second set temperature is also the temperature of the second drying. As an example, the second set temperature can be 100°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C or 110°C. Further, the second set temperature can be a range value consisting of any two of the above point values ​​as end values. Preferably, the second set temperature can be 104°C to 106°C. More preferably, the second set temperature is 105°C. Controlling the temperature of the aroma machine can make the polyphenol aroma substances in the tobacco leaves emit better, enhance the aroma intensity and aroma quality of the tobacco, and make the tobacco products have a more mellow and full aroma.

[0059] In some embodiments, the second drying process lasts for 10 min to 15 min.

[0060] In some embodiments, the moisture content of the cured tobacco leaves obtained after the second drying treatment is less than 5wt%.

[0061] In another embodiment of the present application, a cured tobacco leaf prepared according to the above-mentioned curing method is provided.

[0062] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention, which can be used to describe the present invention and cannot be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0063] In order to better illustrate the present invention, the present invention is further described below in conjunction with the embodiments. The following are specific embodiments.

[0064] The tobacco leaf samples used in this embodiment and comparative example are as follows:

[0065] Test materials

[0066] Variety: Yunyan 87; Part: middle leaves (determined by the number of leaves left in the field); Maturity: moderately mature; Location: Yong'an Town, Liuyang City

[0067] Sampling requirements: The tobacco leaves should be in good condition, with uniform maturity at harvest, from the same plot, with uniform growth, consistent fertilization plan, the same field management measures, away from roads, without cover, and free of disease.

[0068] Sampling method: After removing the bottom leaves, select 2 continuous plots of about 3 mu (one of which is used as a backup to avoid diseases and other factors that affect the quality of tobacco leaves), mark the tobacco leaves in the field that meet the sampling standards, and when the tobacco leaves are ripe, sample 220 kg of tobacco leaves at one time for backup.

[0069] Note: Contact the local tobacco station technicians in advance, select tobacco farmers with good planting and flue-curing techniques, determine the farmers and plots for sampling, and collect field management information.

[0070] Example 1

[0071] Withering: Weave the fresh tobacco leaves into poles, hang them evenly in the withering machine, and set the temperature for withering. During this period, the tobacco leaf status and withering situation should be frequently observed. If the withering is uneven, the position of the tobacco leaf hanging pole should be adjusted in time. The dry bulb temperature for withering is set at 38℃ and the wet bulb temperature at 36℃. When the moisture content reaches 55%, take out the tobacco leaves.

[0072] Steaming: Weigh 1000g of tobacco leaves for steaming, spread them thinly on the steaming bamboo strips of a clean steamer. Clean the steamer in advance and add distilled water to preheat it. After the steamer is steaming, steam the tobacco leaves in the steam for 8 to 10 minutes. After steaming, take out the tobacco leaves, spread them evenly on a drying tray, use cold air to dry the surface moisture, and wait for the tobacco leaves to cool to room temperature before proceeding to the next fermentation process.

[0073] Fermentation: Prepare the fermentation frame, spread a layer of moistened gauze at the bottom of the fermentation frame, put the steamed tobacco leaves into the fermentation frame, and evenly stack them. The thickness of the pile is about 5cm, and two air holes are left for heat dissipation and ventilation to ensure sufficient reaction during the fermentation process. After the tobacco leaves are laid, cover them with a layer of moistened gauze to ensure sufficient moisture. Put the fermentation frame into the fermentation box, set the constant temperature of 41℃ for fermentation, the relative humidity in the box is 80%, automatic humidification, automatic ventilation time of 10 minutes, and fermentation time of 13h. During this period, the state of the tobacco leaves in the fermentation frame needs to be regularly observed.

[0074] Drying: Take out the tobacco leaves in the fermentation frame and place them evenly on the drying tray. Be careful to unfold the rolled tobacco leaves, otherwise some of the tobacco leaves will be difficult to dry. After placing them, turn on the dryer for preheating. After reaching the set temperature, put the drying tray into the dryer and dry it at 85℃ for about 15 minutes. After the tobacco leaves are basically dry, take them out and place them for about 30 minutes. Set the temperature of the aroma machine to 105℃. After reaching the set temperature, put the drying tray into the aroma machine for drying. When the moisture content of the tobacco leaves is less than 5%, the tobacco leaves are completely dry; take them out.

[0075] Comparative Example 1

[0076] The preparation method of this embodiment is basically the same as that of Example 1, and the only difference is that the moisture content of the tobacco leaves obtained after withering is different. In this embodiment, the moisture content of the tobacco leaves obtained after withering is 60%.

[0077] Comparative Example 2

[0078] The preparation method of this embodiment is basically the same as that of Example 1, and the only difference is that the moisture content of the tobacco leaves obtained after withering is different. In this embodiment, the moisture content of the tobacco leaves obtained after withering is 50%.

[0079] Comparative Example 3

[0080] The preparation method of this comparative example 1 is basically the same as that of Example 1, except that this comparative example does not steam the tobacco leaves after withering, but uses rolling to replace the steaming step. Specifically, the rolling steps in this comparative example are as follows:

[0081] Rolling: Remove the main veins of withered tobacco leaves along both sides of the main veins with a knife and cut them into small pieces of 10 cm square. Put the cut tobacco leaves into the rolling machine. The amount of tobacco leaves put into the container should be 75% to 85% (i.e. the rolling amount is 2.0 kg). The rolling and pressing should follow the principle of "light-heavy-light". During the rolling process, the tobacco leaves that are rolled into a ball are dispersed to ensure full rolling and uniform and full crushing of the leaf pulp cells. The rolling time is about 20 minutes.

[0082] The fermentation and drying steps of this comparative example are consistent with those of Example 1.

[0083] Comparative Example 4

[0084] The preparation method of this comparative example 2 is basically the same as that of Example 1, except that this comparative example does not steam the tobacco leaves after withering, but replaces the steaming step with a greening method. Specifically, the greening steps in this comparative example are as follows:

[0085] Making green tea: It mainly includes two steps of shaking and drying green tea. Making green tea will be carried out in the green tea making room, which is equipped with air conditioning and air humidifier to ensure the temperature and humidity conditions of the green tea making environment. The number of times of making green tea is 4 times, one shaking and one drying, the shaking time is 4min, 4min, 8min, 4min respectively; the drying time is 1h, 2h, 2h, 3h respectively, a total of 8h. The temperature of the green tea making room is controlled at 26℃, and the relative humidity of the environment is above 60%. Fermentation is carried out after the green tea making is completed.

[0086] The fermentation and drying steps of this comparative example are consistent with those of Example 1.

[0087] Testing items and methods

[0088] (1) Conventional chemical indicators

[0089] Test items: total sugar, total nitrogen, total alkali, reducing sugar, chlorine, potassium, starch, protein, and plastid pigment.

[0090] Detection method: Determine the total sugar and reducing sugar content according to YC / T 159-2002; determine the total alkali content according to YC / T 468-2013; determine the chloride ion content according to YC / T 162-2002; determine the potassium ion content according to YC / T 217-2007; determine the total nitrogen content according to YC / T 161-2002; determine the starch content according to YC / T 216-2007; determine the protein content according to YC / T 166-2003; determine the plastid pigment content according to YC / T 382-2010.

[0091] (2) Evaluation

[0092] Organized and implemented by Hunan China Tobacco Technology Center.

[0093] The smoking evaluation indicators include three categories: aroma characteristics (total score is 36), smoke characteristics (total score is 18) and taste characteristics (total score is 54).

[0094] Aroma characteristics: aroma quality (total score is 9), aroma quantity (total score is 9), permeability (total score is 9), and miscellaneous aroma (total score is 9).

[0095] Smoke characteristics: concentration (total score: 9), softness and fineness (total score: 9).

[0096] Taste characteristics: strength (total score 9), pungency (total score 9), aftertaste (total score 9), sweetness (total score 9), dryness (total score 9), cleanliness (total score 9).

[0097] (3) Detection of polyphenol aroma substances

[0098] Testing items: polyphenol aroma substances.

[0099] Detection method: Determine the contents of chlorogenic acid, rutin, scopoletin and kaempferol according to YC / T202-2006 method and calculate the total amount. The result is the average of 3 repeated measurements.

[0100] Data processing and analysis

[0101] Excel was used to preliminarily process and tabulate the experimental data, and the DPS data processing system was used for variance analysis.

[0102] Results and analysis:

[0103] The aroma characteristics and smoke characteristics scores of the tobacco leaves after modulation in each embodiment and comparative example are shown in Table 1 below.

[0104] Table 1

[0105]

[0106] Note: a, b, and c in the table represent the significance of differences between different groups, respectively; the same letters indicate no significant difference between the corresponding groups; different letters indicate significant difference between the corresponding groups, i.e., P < 0.05.

[0107] In conjunction with Table 1, by comparing Example 1 with Comparative Examples 1 to 2, it can be seen that the moisture content of tobacco leaves after withering treatment has a significant effect on the aroma characteristics and smoke characteristics scores of tobacco leaves. In terms of the total aroma score, the score of the tobacco leaves prepared in Example 1 is 5.57% higher than that of the tobacco leaves prepared in Comparative Example 1, and 5.61% higher than that of the tobacco leaves prepared in Comparative Example 2. In terms of smoke scores, the score of the tobacco leaves prepared in Example 1 is 3.62% higher than that of the tobacco leaves prepared in Comparative Example 1, and 1.15% higher than that of the tobacco leaves prepared in Comparative Example 3. The tobacco leaves prepared in Example 1 are significantly higher than those in Comparative Examples 1 and 2 in terms of aroma quality, aroma quantity, permeability, impurities, concentration, softness and delicacy.

[0108] By comparing Example 1 with Comparative Examples 3-4, it can be found that Example 1 uses tobacco leaves prepared by withering, steaming, fermentation and drying steps in sequence, and the scores in aroma characteristics and smoke characteristics are the highest; Comparative Example 4 uses tobacco leaves prepared by withering, making green, fermentation and drying steps, and the scores in Comparative Example 3 using withering, rolling, fermentation and drying steps are the lowest. The tobacco leaves prepared in Example 1 are significantly higher in aroma quality, aroma volume, permeability and impurity scores than the tobacco leaves prepared in Comparative Example 3; the aroma quality, permeability and impurity scores of the tobacco leaves prepared in Example 1 are significantly higher than those of the tobacco leaves prepared in Comparative Example 4. In terms of smoke concentration, there is no significant difference between the tobacco leaves prepared in Example 1 and the tobacco leaves prepared in Comparative Example 4, but both are significantly higher than the tobacco leaves prepared in Comparative Example 3. As can be seen from the above, the tobacco leaves prepared by steaming, withering, fermentation and drying steps have better aroma characteristics and smoke characteristics.

[0109] The taste characteristics and evaluation scores of the tobacco leaves prepared in each embodiment and comparative example are shown in Table 2 below.

[0110] Table 2

[0111]

[0112] Combined with the data in Table 2, by comparing Example 1 with Comparative Examples 1~2, it can be found that the tobacco leaves prepared in Example 1 are significantly higher than those in Comparative Examples 1 and 2 in terms of taste characteristics and total scores of smoking evaluation. Specifically, in terms of taste characteristics, Example 1 is 1.64% higher than Comparative Example 1 and 0.76% higher than Comparative Example 2. In terms of total scores of smoking evaluation, Example 1 is 3.01% higher than Comparative Example 1 and 2.23% higher than Comparative Example 2. There is no significant difference in sweetness and cleanliness between Example 1 and Comparative Examples 1~2; however, there are significant differences in strength, aftertaste, and dryness; in general, the tobacco leaves prepared in Example 1 have higher smoking scores in most indicators than Comparative Examples 1 and 2, and the improvement effect in aroma characteristics is significant.

[0113] Comparing Comparative Example 1 with Comparative Examples 3 and 4, it can be seen that the tobacco leaves prepared in Example 1 have higher taste scores and total scores, as well as higher total scores for smoking evaluation than those of Comparative Examples 3 and 4. It can be seen that the use of the steaming treatment method can further improve the taste performance and smoking performance of tobacco leaves.

[0114] The textual description of the smoking evaluation of the tobacco leaves after being prepared in each embodiment and comparative example is shown in Table 3.

[0115] Table 3

[0116]

[0117] Combined with Table 3, by comparing Example 1 and Comparative Examples 1-2, it can be found that the description of honey sweet aroma appears in all three groups of examples, indicating that the steamed green tobacco leaves enhance the expression of honey sweet aroma. Continuing to compare the three groups of examples, among them, in Comparative Example 1, the green miscellaneous smell is heavier, and there is residue on the tongue surface; the aftertaste of Comparative Example 2 is slightly astringent, and the residue and irritation are increased; while Example 1 has only a slight green miscellaneous smell, and the aroma concentration and aroma amount are increased, and the roasted aroma, honey sweet aroma, and hay aroma are clearly expressed. In summary, honey sweet aroma is the characteristic aroma of steamed green tobacco leaves, and the tobacco leaves prepared in Example 1 have a better effect in terms of smoking evaluation; it also shows that when the moisture content of the tobacco leaves after withering treatment is controlled to 55%, the tobacco leaves have the best smoking evaluation effect.

[0118] By comparing Example 1 with Comparative Examples 3 and 4, it can be found that the tobacco leaves prepared in Example 1 have characteristic aromas of baking aroma and honey sweet aroma, the tobacco leaves prepared in Comparative Example 4 have characteristic aromas of burnt aroma and nut aroma, and the tobacco leaves prepared in Comparative Example 3 have more prominent baking aroma and hay aroma. At the same time, it also shows that the tobacco leaves treated by steaming have better characteristic aromas of baking aroma and honey sweet aroma.

[0119] The chemical compositions of the tobacco leaves obtained after the preparation of each embodiment and comparative example are shown in Table 4.

[0120] Table 4

[0121]

[0122] In conjunction with Table 4, by comparing the examples and comparative examples 1 to 2, it can be found that there are significant differences in the total sugar, reducing sugar, total alkali, and starch contents of the tobacco leaves prepared in the three groups of examples, and there are no significant differences in the total nitrogen, chloride ion, and potassium ion contents. Among them, the total sugar content in the tobacco leaves prepared in Example 1 is significantly higher than that in Comparative Examples 1 and 2. As the moisture content of the tobacco leaves after withering decreases, the total sugar content tends to increase and then decrease; specifically, the total sugar content of Example 1 is 12.80% higher than that of Comparative Example 1 and 2.78% higher than that of Comparative Example 2. The reducing sugar and total sugar have the same changing trend, wherein the reducing sugar content of Example 1 is 17.64% higher than that of Comparative Example 1 and 13.50% higher than that of Comparative Example 2. The starch content shows a trend of first decreasing and then increasing as the moisture content of the tobacco leaves after withering treatment decreases. Specifically, the starch content in the tobacco leaves prepared in Example 1 is significantly lower than that in the tobacco leaves prepared in Comparative Examples 1 and 2. Compared with the starch content in the tobacco leaves prepared in Comparative Example 1, Example 1 is reduced by 29.45%; compared with Comparative Example 2, the starch content in the tobacco leaves prepared in Example 1 is reduced by 20.65%. As the withering progresses, the decrease in starch content is a normal physiological change in tobacco leaves, but the starch content increases abnormally when the moisture content of the tobacco leaves is withered to 50%, which may be due to the differences in the substances contained in tobacco leaves with different withering degrees, and more starch is decomposed in Example 1 during the fermentation stage. Therefore, judging fermentation is also an important step in the entire preparation process.

[0123] Comparing Example 1 with Comparative Examples 3-4, it can be seen that the total sugar content in the tobacco leaves prepared in Example 1 and Comparative Example 3 is significantly higher than that in Comparative Example 4. The reducing sugar content in the tobacco leaves prepared in Comparative Example 3 is significantly higher than that in Example 1 and Comparative Example 4. The total alkali content in the tobacco leaves prepared in Example 1 is significantly higher than that in Comparative Example 3 and Comparative Example 4. There is no significant difference in chloride ion content. The potassium ion content in the tobacco leaves prepared in Comparative Example 4 is lower than that in Comparative Example 3 and Example 1, and the total nitrogen content is Example 1>Comparative Example 4>Comparative Example 3. The starch content prepared in Example 1 is significantly lower than that in the other two treatments.

[0124] The plastid pigment content of the tobacco leaves obtained after modulation in each embodiment and comparative example is shown in Table 5.

[0125] Table 5

[0126]

[0127] Combined with Table 5, Example 1 is compared with Comparative Example 1 and Comparative Example 2; it can be found that the chlorophyll and carotenoid contents in the tobacco leaves prepared in Comparative Example 1 are significantly higher than those in Example 1 and Comparative Example 2; among them, the chlorophyll a content in the tobacco leaves prepared in Example 1 and Comparative Example 2 is 0.03 mg / g lower than that in Comparative Example 1, the chlorophyll b content is 0.03 mg / g lower than that in Comparative Example 1, the carotenoid content is 0.04 mg / g and 0.05 mg / g lower than that in Comparative Example 1, respectively, the total chlorophyll content is 0.08 mg / g lower than that in Comparative Example 1, and the total amount of plastid pigment is more than 0.10 mg / g lower than that in Comparative Example 1. The above results show that when the tobacco leaves are withered to a moisture content of about 55%, the internal plastid pigment reaches the minimum value, and as the moisture content further decreases, the degradation rate of the plastid pigment is lower.

[0128] By comparing Example 1 with Comparative Examples 3 and 4, it can be found that the chlorophyll a and chlorophyll b contents in the tobacco leaves prepared in Example 1 and Comparative Example 4 are significantly lower than those in Comparative Example 3, the carotenoid content in the tobacco leaves prepared in Example 1 is the lowest, and the carotenoid content in the tobacco leaves prepared in Comparative Example 4 is the highest. Moreover, the total amount of plastid pigments in the tobacco leaves prepared in the three groups of examples is significantly different, wherein the total amount of plastid pigments in the tobacco leaves prepared in Example 1 is reduced by 0.10 mg / g compared with Comparative Example 3, and by 0.03 mg / g compared with Comparative Example 4. This indicates that the steaming treatment is beneficial to the degradation of macromolecular substances in tobacco leaves.

[0129] The polyphenol content of the tobacco leaves obtained after modulation in each embodiment and comparative example is shown in Table 6.

[0130] Table 6

[0131]

[0132] Combined with Table 6, Example 1 is compared with Comparative Example 1 and Comparative Example 2: the content of polyphenols in the tobacco leaves prepared by Example 1 is the highest, followed by Comparative Example 1, and the lowest is Comparative Example 2. Specifically, the total amount of polyphenols in the tobacco leaves prepared by Example 1 is 14.93% and 28.61% higher than that of Comparative Example 1 and Comparative Example 2, respectively. There is no significant difference in the content of chlorogenic acid and scopoletin between Comparative Example 1 and Example 1, but both are significantly higher than Comparative Example 2. The contents of rutin and kaempferol in the tobacco leaves prepared by Example 1 are significantly higher than those in Comparative Example 1 and Comparative Example 2. It is explained that when the tobacco leaves are withered to a moisture content of 55%, the accumulation of polyphenols reaches its peak, and continued withering may cause water imbalance in the tobacco leaves and damage to some membrane structures, resulting in contact between polyphenols and oxygen, and then leading to oxidative loss of chlorogenic acid and rutin content and an increase in scopoletin content.

[0133] By comparing Example 1 with Comparative Examples 3 and 4, it can be found that, in the tobacco leaves prepared in Example 1, except for the content of scopoletin, the contents of chlorogenic acid, rutin, and kaempferol are significantly higher than those in Comparative Examples 3 and 4, and the total amount of polyphenol aroma substances in the tobacco leaves prepared in Example 1 is 2.36 times that of Comparative Example 4 and 4.25 times that of Comparative Example 3. This shows that the steaming treatment is more conducive to the retention of polyphenol aroma substances in tobacco leaves.

[0134] Based on the performance data in Tables 1 to 6, the following conclusions can be drawn by comparing Example 1 with Comparative Examples 1 to 2:

[0135] 1. The tobacco leaves treated with steaming all have a sweet and fragrant aroma, among which Example 1 has the highest smoking score and the most prominent sweet and fragrant aroma.

[0136] 2. The contents of total sugar, reducing sugar and total alkali in the tobacco leaves prepared in Example 1 are significantly higher than those in Comparative Example 1 and Comparative Example 2, and the starch content is significantly lower than those in Comparative Example 1 and Comparative Example 2.

[0137] 3. The content of plastid pigment in the tobacco leaves prepared in Example 1 and Comparative Example 2 was significantly lower than that in Comparative Example 1, indicating that the plastid pigment degraded slowly after the moisture content of the tobacco leaves was lower than 55%.

[0138] 4. The content of polyphenol aroma components in the tobacco leaves prepared in Example 1 is the highest, while that in Comparative Example 2 is the lowest, indicating that a moisture content of 55% in the leaves is conducive to the formation and retention of polyphenol aroma components.

[0139] In summary, it can be concluded that withering tobacco leaves to a moisture content of 55% is beneficial to the degradation of starch and plastid pigments and the conversion and retention of sugars and polyphenols, and is more suitable for the steaming process.

[0140] Furthermore, in the present application, the withered tobacco leaves are inactivated by high-temperature steam to inactivate their biological enzyme activity, which plays a role in preserving the key aroma substances in the tobacco leaves and fixing the color of the tobacco leaves. The degradation rate of the plastid pigments in the tobacco leaves after steaming is relatively high, the total sugar and reducing sugar contents are higher than those of the withered tobacco leaves, and the total alkali content can be reduced; the polyphenol content of the steamed tobacco leaves is far higher than that of the rolled tobacco leaves, and the color and morphology of the tobacco leaves are similar to flue-cured tobacco. From the results of the smoking test, the steamed tobacco leaves scored higher, and their styles were burnt sweet and honey sweet, and their quality and availability were relatively high.

[0141] Steaming can increase the content of total sugar and reducing sugar in tobacco leaves. This may be caused by the violent movement of polysaccharide molecules caused by temperature. When the temperature rises to a certain level, the polysaccharide chains break and decompose, so the content of reducing sugar increases. The content of total alkali decreases significantly after steaming, which may also be due to the breakage of nitrogen-containing functional groups caused by intense high temperature. Based on the comprehensive conventional chemical indicators, it can be concluded that the tobacco leaves after steaming are of high-quality level, and their nitrogen-alkali ratio is greater than 1, which may lead to high irritation. After fermentation is completed, the content of total sugar, reducing sugar and total alkali is higher than that before fermentation, while potassium ions are lost. This may be because after the tobacco leaves are damaged, the air oxidation and microbial action cause the degradation of polysaccharides in the tobacco leaves, increasing the content of total sugar and reducing sugar. Because its cells are damaged, potassium ions in the tobacco leaves may be continuously lost as the fermentation proceeds.

[0142] From the degradation of macromolecular substances, the steaming treatment has a significant effect on the degradation of plastid pigments in tobacco leaves, among which chlorophyll has the best degradation effect. This may be due to the high temperature of the permeability, which causes the chlorophyll to undergo a de-magnesium reaction. However, due to the high moisture environment, it is not easy for the tobacco leaves to further generate charred de-magnesium chlorophyll and turn the tobacco leaves brown. The degradation efficiency of plastid pigments decreases during the fermentation process. This may be because the steaming treatment has cleaved most of the plastid pigments. After the fermentation is completed, the color of the tobacco leaves remains. This may be because the water vapor generated during the steaming process enters the tobacco leaves as the cells are broken, thereby reducing the area of ​​contact between the tobacco leaves and the air, thereby reducing the discoloration of the tobacco leaves caused by oxidation.

[0143] Steaming is an effective way to preserve polyphenols in tobacco leaves. This process can effectively preserve chlorogenic acid, rutin and kaempferol in tobacco leaves. After fermentation, the content of kaempferol and rutin is further increased. Unlike rolling, the steaming process does not cause or promote the conversion of aroma substances, but preserves them as much as possible. Traditional baking technology believes that hot air will accelerate the volatilization of phenolic substances, but high-temperature steaming can effectively preserve them, which may be because the medium that transmits temperature has become water vapor at this time.

[0144] Judging from the results of the smoking evaluation, the aroma of steamed green tobacco leaves is described as burnt sweet, honey sweet, and hay-scented but slightly raw; the steamed green tobacco leaves are superior to the rolled tobacco leaves in terms of aroma quality, aroma volume, sweetness, aftertaste, and softness and delicacy, but the higher irritation in the taste characteristics lowers the overall score of the steamed green tobacco leaves.

[0145] From the perspective of modulation, steamed tobacco leaves are essentially different from traditional flue-cured tobacco and imitation black tea modulation techniques. The core is to change the heat transfer medium to preserve the various aroma substances in the tobacco leaves. In terms of conventional chemical composition, total sugar, reducing sugar and total alkali of steamed tobacco leaves are affected by high temperature, and the steaming process can significantly cleave the plastid pigments with heat-unstable characteristics. The effect of fermentation on tobacco leaves is reflected in total sugar, reducing sugar and potassium ions; fermentation has little effect on total polyphenols in tobacco leaves, and slightly improves rutin and kaempferol. The tobacco leaves after steaming are of high-quality level, with distinct style characteristics and significant effect of steaming.

[0146] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0147] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A method for preparing fresh tobacco leaves, characterized in that: The steps include: The fresh tobacco leaves are withered to obtain first tobacco leaves; the moisture content of the first tobacco leaves is 53wt% to 57wt%; steaming the first tobacco leaves to obtain second tobacco leaves; The second tobacco leaves are subjected to fermentation treatment and drying treatment in sequence.

2. The modulation method according to claim 1, characterized in that: The steaming time is 8 to 12 minutes.

3. The modulation method according to claim 1 or 2, characterized in that: The withering treatment is carried out in a withering machine, and during the withering treatment, the dry bulb temperature of the withering machine is set to 38°C~39°C, and the wet bulb temperature is set to 35°C~36°C.

4. The modulation method according to claim 1 or 2, characterized in that: The temperature of the fermentation treatment is 40°C to 45°C.

5. The modulation method according to claim 1 or 2, characterized in that: The relative humidity of the fermentation treatment is 80% to 85%.

6. The modulation method according to claim 1 or 2, characterized in that: The fermentation time is 10h~15h.

7. The modulation method according to claim 1 or 2, characterized in that: During the fermentation process, the second tobacco leaves are stacked together, and the stacking thickness of the second tobacco leaves is 4.5 cm to 5.5 cm.

8. The modulation method according to claim 1 or 2, characterized in that: The drying process comprises: The drying equipment is preheated first, and after the temperature in the drying equipment reaches a first set temperature, the tobacco leaves to be dried are placed in the drying equipment for a first drying treatment; the first set temperature is 80°C to 90°C; and the time for the first drying treatment is 10min to 20min.

9. The modulation method according to claim 8, characterized in that: After the first drying process, the drying process comprises: The aroma machine is preheated first, and after the temperature of the aroma machine reaches a second set temperature, the tobacco leaves after the first drying treatment are placed in the aroma machine for a second drying treatment; the second set temperature is 100°C~110°C.

10. A cured tobacco leaf, characterized in that: The cured tobacco leaves are prepared according to the curing method according to any one of claims 1 to 9.

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