Method for curing tobacco leaf and cured tobacco leaf

Abstract

The application relates to a tobacco leaf curing method and cured tobacco leaf. The method comprises the following steps: subjecting fresh tobacco leaf to wilting treatment to obtain first tobacco leaf; the moisture content of the first tobacco leaf is 53wt%-57wt%; subjecting the first tobacco leaf to water-steam curing treatment to obtain second tobacco leaf; and sequentially subjecting the second tobacco leaf to fermentation treatment and drying treatment. In the above tobacco leaf curing method, the wilting treatment, the steam curing treatment, the fermentation treatment and the drying treatment are sequentially performed, and the moisture content of the tobacco leaf after the wilting treatment is controlled, so that the tobacco leaf with high content of similar aroma substances and low content of macromolecular substances such as starch, protein and plastid pigment in the tobacco leaf can be obtained; and the tobacco leaf also has a characteristic honey sweet aroma.

Description

Technical Field

[0001] This invention relates to the field of tobacco processing technology, and in particular to a method for processing fresh tobacco leaves and processed tobacco leaves. Background Technology

[0002] The main method of tobacco leaf curing is intensive curing, which essentially involves using equipment to control temperature and humidity to turn the tobacco leaves yellow, develop aroma, and dry them. Tobacco leaf curing is an optimized combination and integration of multiple related technologies. It requires accurate judgment of the maturity of the tobacco leaves and timely harvesting, and then determining the curing characteristics and parameters based on the quality of the fresh leaves. Among these, timely harvesting at the appropriate maturity is the foundation of curing tobacco leaves and the key to highlighting the quality of the tobacco leaves formed in the field during the curing process.

[0003] Based on preparation methods, tobacco can be categorized into four basic types: sun-dried, air-dried, smoked, and flue-cured. These processes involve dehydrating and drying tobacco leaves through various means, resulting in physical and chemical changes. Traditional flue-cured tobacco processing techniques primarily employ a three-stage curing process. This involves detailed discussions of tobacco curing equipment, the mechanism of tobacco curing quality formation, and standard curing techniques. A core principle for improving quality and aroma has been established: "low temperature, medium humidity, slow yellowing; medium humidity, color setting, slow temperature increase; variable-speed ventilation, slow moisture removal; stable time at key stages; and gentle air drying to preserve aroma." However, the maturity of the harvested tobacco leaves and the curing process result in a relatively fixed style and a somewhat singular aroma in flue-cured tobacco. Furthermore, improvements to the flue-cured tobacco processing techniques cannot fundamentally alter the aroma and flavor of the tobacco leaves. Summary of the Invention

[0004] Therefore, it is necessary to provide a method for processing fresh tobacco leaves, which produces processed tobacco leaves with a high content of polyphenolic aroma substances and a good aroma. Furthermore, a processed tobacco leaf is provided.

[0005] In a first aspect, this application provides a method for processing fresh tobacco leaves, comprising the following steps:

[0006] Fresh tobacco leaves are withered to obtain the first tobacco leaf; the moisture content of the first tobacco leaf is 53wt%~57wt%.

[0007] The first tobacco leaf is steamed in a water-water steaming process to obtain the second tobacco leaf;

[0008] The second tobacco leaf is then subjected to fermentation and drying processes in sequence.

[0009] In the tobacco leaf conditioning method, the wilting treatment, the steaming treatment, the fermentation treatment and the drying treatment are sequentially performed, and the moisture content of the tobacco leaf after the wilting treatment is controlled to obtain the tobacco leaf with high content of aroma substances and low content of macromolecular substances such as starch, protein and plastid pigment in the tobacco leaf; the tobacco leaf also has a characteristic aroma of honey sweet. By controlling the moisture content of the tobacco leaf after the wilting treatment, the content of macromolecular substances such as starch, protein and plastid pigment in the tobacco leaf is reduced, and the quality of the tobacco leaf is improved; further, by performing the steaming treatment on the tobacco leaf after the wilting, the damage to the leaf cells is reduced, and the content of polyphenolic aroma substances is increased; then, the fermentation treatment and the drying treatment are performed in cooperation to improve the smoking quality of the tobacco leaf, and the tobacco leaf has a characteristic aroma of honey sweet.

[0010] In some embodiments, the steaming treatment is performed for 8 min to 12 min.

[0011] In some embodiments, the wilting treatment is performed in a wilting machine, and in the wilting treatment, the dry bulb temperature of the wilting machine is set to 38℃ to 39℃, and the wet bulb temperature is set to 35℃ to 36℃.

[0012] In some embodiments, the fermentation treatment is performed at a temperature of 40℃ to 45℃.

[0013] In some embodiments, the fermentation treatment is performed at a relative humidity of 80% to 85%.

[0014] In some embodiments, the fermentation treatment is performed for 10 h to 15 h.

[0015] In some embodiments, during the fermentation treatment, 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 treatment comprises the following steps:

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

[0018] In some embodiments, after the first drying treatment, the drying treatment comprises the following steps:

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

[0020] The second aspect of the present application provides a cured tobacco leaf prepared according to the curing method of the first aspect. DETAILED DESCRIPTION

[0021] For the purpose of promoting the understanding of the present application, the present application will be more fully described by referring to the preferred embodiments thereof. This present application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the application to those skilled in the art.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0023] In addition, the terms "first", "second", etc. are used herein only to describe different instances, and cannot be construed as indicating or implying relative importance or an indicated number of technical features. Thus, the features defined with "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0024] In an embodiment of the present application, a curing method of tobacco fresh leaves is provided, comprising the following steps S10-S40:

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

[0026] S20, subjecting the first tobacco leaves to water-steam curing treatment to obtain second tobacco leaves.

[0027] S30, subjecting the second tobacco leaves to fermentation treatment.

[0028] S40, subjecting the tobacco leaves after fermentation treatment to drying treatment.

[0029] In this application, the moisture content refers to the mass content of water.

[0030] In the tobacco leaf conditioning method, the wilting treatment, the steaming treatment, the fermentation treatment and the drying treatment are sequentially performed, and the moisture content of the tobacco leaf after the wilting treatment is controlled, so that a tobacco leaf with high content of aroma-like substances and low content of macromolecular substances such as starch, protein and plastid pigment in the tobacco leaf is obtained; the tobacco leaf also has a characteristic aroma of honey sweet. By controlling the moisture content of the tobacco leaf after the wilting treatment, the content of macromolecular substances such as starch, protein and plastid pigment in the tobacco leaf is reduced, and the quality of the tobacco leaf is improved; further, by performing the steaming treatment on the tobacco leaf after the wilting, the damage to the leaf cells is reduced, and the content of polyphenolic aroma substances is increased; then, the fermentation treatment and the drying treatment are performed in cooperation, the smoking quality of the tobacco leaf is improved, and the tobacco leaf has a characteristic aroma of honey sweet.

[0031] For example, the moisture content of the first tobacco leaf can be 53wt%, 54wt%, 54.5wt%, 55wt%, 55.5wt%, 56wt%, 56.5wt% or 57wt%. Further, the moisture content of the first tobacco leaf can be a range value formed by taking any two of the above point values as end values. By controlling the moisture content of the first tobacco leaf, the macromolecular substances such as starch, protein and plastid pigment in the tobacco leaf can be sufficiently degraded. If the moisture content of the tobacco leaf is too low, the content of polyphenolic substances such as chlorogenic acid and rutin will be greatly reduced; if the moisture content of the tobacco leaf is too high, the degradation of starch and plastid pigment will not be sufficient.

[0032] Further, the moisture content of the first tobacco leaf is 54.5wt% to 55.5wt%.

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

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

[0035] In some embodiments, the wilting treatment is performed in a wilting machine.

[0036] In some embodiments, in the wilting treatment, the dry bulb temperature in the wilting machine is set to 38°C to 39°C, and the wet bulb temperature is set to 35°C to 36°C.

[0037] In some embodiments, when the wilting treatment is performed, the tobacco leaves need to be bundled and hung uniformly in the wilting machine for wilting treatment. During the wilting treatment, the state of the tobacco leaves and the wilting condition need to be observed frequently, and if the wilting is uneven, the position of the tobacco leaf bundle needs to be adjusted in time.

[0038] In some embodiments, the steaming time is 8 min to 12 min. For 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 formed by any two point values described above as end values.

[0039] Further, the steaming time is 9 min to 11 min.

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

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

[0042] Placing the first tobacco leaves on the steaming rack of the steamer;

[0043] Adding water to the steamer and then heating, and placing the steaming rack carrying the first tobacco leaves in the steam after the steamer is steamed, steaming the first tobacco leaves, and taking out the tobacco leaves after the steaming is completed to obtain the second tobacco leaves.

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

[0045] In some embodiments, the fermentation temperature is 40℃ to 45℃. For example, the fermentation temperature can be 40℃, 41℃, 42℃, 43℃, 44℃ or 45℃. Further, the fermentation temperature can be a range value formed by any two point values described above as end values. Preferably, the fermentation temperature is 40℃ to 42℃, by controlling the fermentation temperature, the content of sugar substances such as total sugar, reducing sugar, starch and the like in the tobacco leaves can be regulated, the fermentation temperature affects the microbial activity in the tobacco fermentation process, the microorganisms have high activity in the above range, and consume more sugar substances, so that the starch content in the tobacco leaves is lower, which also leads to the degradation of part of the macromolecular substances and the increase of the aroma substance content, and the smoking quality is improved.

[0046] In some embodiments, the relative humidity of the fermentation process is 80% to 85%. For 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 formed by any two point values described above 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. In the automatic humidification process, fresh air is automatically introduced every 10 min.

[0048] In some embodiments, the fermentation treatment is performed for 10-15 hours. For example, the fermentation treatment can be performed for 10 hours, 11 hours, 12 hours, 13 hours, 14 hours or 15 hours. Further, the fermentation treatment can be performed for a range defined by any two of the above-mentioned values as the end values. Preferably, the fermentation treatment is performed for 12-14 hours.

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

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

[0051] In some embodiments, during the fermentation treatment, 1-2 air holes with a diameter of 10-15 cm are left in the stack of the second tobacco leaves. The air holes pass through the upper end and the bottom end of the stack. The air holes are provided to facilitate heat dissipation and air permeation, so as to ensure that the reaction is sufficient during the fermentation.

[0052] In some embodiments, the drying treatment comprises step S41.

[0053] S41, the drying equipment is preheated first, and then the tobacco leaves to be dried are placed in the drying equipment for first drying treatment after the temperature in the drying equipment reaches a first set temperature.

[0054] In some embodiments, the first set temperature is 80-90°C. It can be understood that the first set temperature is the temperature of the first drying. For 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 defined by any two of the above-mentioned values as the end values. Preferably, the first set temperature can be 84-86°C. More preferably, the first set temperature is 85°C.

[0055] In some embodiments, the first drying treatment is performed for 10-20 minutes. Further, the first drying treatment is performed for 14-16 minutes.

[0056] In some embodiments, the above-mentioned drying treatment further comprises step S42 after the first drying treatment.

[0057] S42, the flavoring machine is preheated first, and then the tobacco leaves after the first drying treatment are placed in the flavoring machine for second drying treatment after the temperature of the flavoring machine reaches a second set temperature.

[0058] In some embodiments, the second set temperature is 100-110°C. It can be understood that the second set temperature is also the temperature of the second drying. For 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 formed by any two of the above-mentioned values as end values. Preferably, the second set temperature can be 104-106°C. More preferably, the second set temperature is 105°C. Controlling the temperature of the curing machine can make the polyphenolic aroma substances in the tobacco leaves better spread out, enhance the aroma intensity and aroma quality of the tobacco, and make the tobacco product have a more mellow and full aroma.

[0059] In some embodiments, the second drying treatment is performed for 10-15 minutes.

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

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

[0062] In order to make the purpose, technical solutions and advantages of the present application more concise and clear, the present application is described by the following specific examples, but the present application is not limited to these examples. The examples described below are only better embodiments of the present application, which can be used to describe the present application, and cannot be understood as limiting the scope of the present application. It should be noted that any modification, equivalent replacement and improvement made within the spirit and principles of the present application shall be included in the protection scope of the present application.

[0063] In order to better illustrate the present application, the content of the present application is further described below in combination with examples. The following are specific examples.

[0064] The tobacco leaf samples used in the present examples and comparative examples are as follows:

[0065] Test materials

[0066] Variety: Yunyan 87; Position: middle leaves (determined according to the number of leaves left in the field); Maturity: suitable; Location: Yongan Town, Liuyang City

[0067] Sampling requirements: the tobacco leaves have a good growth potential, the harvesting maturity is consistent, the same plot, the growth potential is uniform, the fertilization scheme is consistent, the field management measures are the same, far away from the road, no shelter, no disease.

[0068] Sampling method: after the foot leaves are removed, select two continuous plots of about 3 mu (one of which is a backup to avoid diseases and other factors affecting the quality of tobacco leaves), mark the tobacco leaves that meet the sampling standards in the field, and sample 220 kg of tobacco leaves at one time after the tobacco leaves are mature.

[0069] Notes: Contact the local tobacco station technician in advance, choose tobacco farmers with good planting and flue-cured tobacco technology, and determine the sampling farmers and plots after the sampling farmers and plots are determined.

[0070] Example 1

[0071] Wilt: The tobacco fresh leaves are bundled and hung evenly in the wilt machine, and the temperature is set for wilting. During this period, the state of the tobacco leaves and the wilting condition need to be observed frequently, and if uneven wilting occurs, the position of the tobacco leaf bundle needs to be adjusted in time. The dry ball temperature is set to 38℃, the wet ball temperature is set to 36℃, and the tobacco leaves are taken out when the moisture content reaches 55%.

[0072] Steaming: 1000g of tobacco leaves are weighed and steamed. The leaves are spread on the steaming net in a clean steaming pot, the steaming pot is cleaned in advance and distilled water is added for preheating. After the steaming pot is steamed, the tobacco leaves are placed in the steam for 8-10 minutes. After steaming, the tobacco leaves are taken out and evenly spread on a drying tray. The surface moisture is blown dry with cold air. After the tobacco leaves are cooled to room temperature, the next step of fermentation is carried out.

[0073] Fermentation: Prepare the fermentation frame, lay a layer of moistened gauze at the bottom of the fermentation frame, and place the steamed tobacco leaves in the fermentation frame. The leaves are evenly stacked to a thickness of about 5cm, with two air holes to ensure sufficient reaction during fermentation and adequate ventilation. After the leaves are laid, cover them with another layer of moistened gauze to ensure adequate moisture. Place the fermentation frame in the fermentation box and set the temperature to 41℃ for constant temperature fermentation. The relative humidity in the box is 80%, with automatic humidification and automatic ventilation every 10 minutes. The fermentation time is 13 hours, and the state of the tobacco leaves in the fermentation frame needs to be observed regularly during this period.

[0074] Drying: Take out the tobacco leaves from the fermentation frame and place them evenly on a drying tray. Make sure to unroll the rolled tobacco leaves, as otherwise some leaves may not dry properly. After the drying machine is preheated, place the drying tray inside. Set the temperature to 85℃ and dry for about 15 minutes. Once the tobacco leaves are dry, take them out and let them sit for about 30 minutes. Set the temperature of the flavor enhancer to 105℃. Once the temperature is reached, place the drying tray inside the flavor enhancer. When the moisture content of the tobacco leaves is less than 5%, the tobacco leaves are completely dry.

[0075] Comparative Example 1

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

[0077] Comparative Example 2

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

[0079] Comparative Example 3

[0080] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that this comparative example does not perform steaming treatment on the withered tobacco leaves, but instead uses rolling to replace the steaming treatment step. Specifically, the rolling step in this comparative example is as follows:

[0081] Rolling: After the tobacco leaves have been withered, remove the main vein along both sides with a knife and cut them into 10cm square pieces. Put the cut tobacco leaves into the rolling machine, with the amount of tobacco leaves in the container ideally between 75% and 85% (i.e., a rolling weight of 2.0kg). The rolling pressure should follow the principle of "light-heavy-light," and any clumps of tobacco leaves should be manually dispersed during the rolling process to ensure thorough rolling and even and complete breaking down of the leaf mesophyll cells. The rolling time is approximately 20 minutes.

[0082] The fermentation and drying steps in this comparative example are the same as those in Example 1.

[0083] Comparative Example 4

[0084] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that this comparative example does not perform steaming treatment on the withered tobacco leaves, but instead uses a withering process to replace the steaming step. Specifically, the withering step in this comparative example is as follows:

[0085] Making the green leaves mainly includes two steps: shaking and drying. The green leaves will be made in a room equipped with air conditioning and a humidifier to ensure the temperature and humidity conditions of the environment. The green leaves will be made four times, with one shaking followed by one drying. The shaking time is 4 minutes, 4 minutes, 8 minutes, and 4 minutes respectively; the drying time is 1 hour, 2 hours, 2 hours, and 3 hours respectively, for a total of 8 hours. The temperature in the green leaves room is controlled at 26℃, and the relative humidity is above 60%. After the green leaves are made, fermentation will begin.

[0086] The fermentation and drying steps in this comparative example are the same as those in 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 pigments.

[0090] Test methods: Total sugar and reducing sugar content are determined according to YC / T 159—2002; total alkali content is determined according to YC / T 468—2013; chloride ion content is determined according to YC / T 162—2002; potassium ion content is determined according to YC / T 217—2007; total nitrogen content is determined according to YC / T 161—2002; starch content is determined according to YC / T 216—2007; protein content is determined according to YC / T 166—2003; plastid pigment content is determined according to YC / T 382—2010.

[0091] (2) Evaluation of absorption

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

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

[0094] Aroma characteristics: Aroma quality (total score 9), Aroma quantity (total score 9), Penetration (total score 9), Off-flavors (total score 9).

[0095] Smoke characteristics: Concentration (out of 9), smoothness and fineness (out of 9).

[0096] Taste characteristics: strength (out of 9), irritation (out of 9), aftertaste (out of 9), sweetness (out of 9), dryness (out of 9), cleanliness (out of 9).

[0097] (3) Detection of polyphenolic aroma substances

[0098] Test item: Polyphenolic aroma substances.

[0099] Detection method: The contents of chlorogenic acid, rutin, hyoscyamine and kaempferol were determined according to YC / T202—2006 and the total amount was calculated. The result is the average of three repeated determinations.

[0100] Data processing and analysis

[0101] The experimental data were initially processed and tabulated using Excel, and then analyzed for variance using the DPS data processing system.

[0102] Results and Analysis:

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

[0104] Table 1

[0105]

[0106] Note: a, b, c in the table represent the significance of difference between different groups; among them, the same letter means no significant difference between the corresponding groups; different letters mean significant difference between the corresponding groups, i.e. P<0.05.

[0107] In combination with Table 1, comparing Example 1 and Comparative Examples 1-2, it can be seen that the water content of the wilted tobacco leaves has a significant effect on the scores of the aroma characteristics and smoke characteristics of the tobacco leaves. In terms of the total aroma score, the score of the tobacco leaves modulated in Example 1 is 5.57% higher than that of the tobacco leaves modulated in Comparative Example 1 and 5.61% higher than that of the tobacco leaves modulated in Comparative Example 2. In terms of the smoke score, the score of the tobacco leaves modulated in Example 1 is 3.62% higher than that of the tobacco leaves modulated in Comparative Example 1 and 1.15% higher than that of the tobacco leaves modulated in Comparative Example 3. The tobacco leaves modulated in Example 1 are significantly higher than those modulated in Comparative Examples 1 and 2 in terms of aroma quality, aroma amount, permeability, foreign odor, concentration, and softness.

[0108] Comparing Example 1 with Comparative Examples 3-4, it can be found that the tobacco leaves modulated in Example 1 using the steps of wilting, steaming, fermentation, and drying in sequence have the highest scores in aroma characteristics and smoke characteristics; the tobacco leaves modulated in Comparative Example 4 using the steps of wilting, curing, fermentation, and drying have the second highest scores; and the tobacco leaves modulated in Comparative Example 3 using the steps of wilting, rolling, fermentation, and drying have the lowest scores. The tobacco leaves modulated in Example 1 are significantly higher than those modulated in Comparative Example 3 in terms of aroma quality, aroma amount, permeability, and foreign odor; and the tobacco leaves modulated in Example 1 are significantly higher than those modulated in Comparative Example 4 in terms of aroma quality, permeability, and foreign odor. In terms of smoke concentration, the tobacco leaves modulated in Example 1 and Comparative Example 4 are not significantly different, but both are significantly higher than those modulated in Comparative Example 3. The above shows that the tobacco leaves modulated by the step of steaming in combination with the steps of wilting, fermentation, and drying have better aroma characteristics and smoke characteristics.

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

[0110] Table 2

[0111]

[0112] In combination with the data in Table 2, comparing Example 1 and Comparative Examples 1-2, it can be found that the tobacco leaves modulated by Example 1 are significantly higher than Comparative Examples 1 and 2 in terms of taste characteristics and total score. 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 score, Example 1 is 3.01% higher than Comparative Example 1 and 2.23% higher than Comparative Example 2. There is no significant difference between Example 1 and Comparative Examples 1-2 in sweetness and cleanliness, but there is a significant difference in strength, aftertaste and dryness. Overall, the tobacco leaves modulated by Example 1 have higher scores in most indicators and have a significant improvement in aroma characteristics.

[0113] Comparing Comparative Example 1 and Comparative Examples 3-4, it can be seen that the tobacco leaves modulated by Example 1 are higher than Comparative Examples 3 and 4 in terms of taste score and total score, and total score. It can be seen that the use of steaming treatment can further improve the taste performance and smoking performance of the tobacco leaves.

[0114] The smoking text description of the tobacco leaves modulated by each example and comparative example is shown in Table 3.

[0115] Table 3

[0116]

[0117] In combination with Table 3, comparing Example 1 and Comparative Examples 1-2, it can be found that honey sweet aroma is described in all 3 groups of examples, indicating that the steaming treated tobacco leaves enhance the expression of honey sweet aroma. Continue to compare the 3 groups of examples, among which, the green and miscellaneous gas in Comparative Example 1 is heavy, and the tongue surface has residues; the aftertaste of Comparative Example 2 is slightly astringent, and the residues and irritability increase; while Example 1 only has a little green and miscellaneous gas, and the aroma concentration and aroma amount increase, the baking aroma, honey sweet aroma and dry grass aroma are clearly expressed. In summary, honey sweet aroma is the characteristic aroma of steaming tobacco leaves, and the tobacco leaves modulated by Example 1 have better smoking effect; also indicates that when the moisture content of the tobacco leaves after wilting treatment is controlled to 55%, the tobacco leaves have the best smoking effect.

[0118] Comparing Example 1 and Comparative Examples 3-4, it can be found that the tobacco leaves modulated by Example 1 have baking aroma and honey sweet aroma characteristic aroma, the tobacco leaves modulated by Comparative Example 4 have characteristic aroma of burnt aroma and nut aroma, and the tobacco leaves modulated by Comparative Example 3 have baking aroma and dry grass aroma. At the same time, it also shows that the tobacco leaves treated by steaming have better baking aroma and honey sweet aroma characteristic aroma.

[0119] The chemical composition of the tobacco leaves obtained after modulation of each example and comparative example is shown in Table 4.

[0120] Table 4

[0121]

[0122] In combination with Table 4, comparing the examples and Comparative Examples 1-2, it can be found that the total sugar, reducing sugar, total alkali, and starch content of the tobacco leaves modulated in the three groups of examples are significantly different, and the total nitrogen, chloride ion, and potassium ion content are not significantly different. Among them, the total sugar content of the tobacco leaves modulated in Example 1 is significantly higher than that of Comparative Example 1 and Comparative Example 2. With the decrease of the water content of the tobacco leaves after the wilting treatment, the total sugar content shows a rising and then falling trend; 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 has the same change trend as the total sugar, and 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 downward and then upward trend with the decrease of the water content of the tobacco leaves after the wilting treatment, and specifically, the starch content of the tobacco leaves modulated in Example 1 is significantly lower than that of Comparative Example 1 and Comparative Example 2. Compared with the starch content of the tobacco leaves modulated in Comparative Example 1, the starch content of Example 1 is reduced by 29.45%; compared with Comparative Example 2, the starch content of the tobacco leaves modulated in Example 1 is reduced by 20.65%. With the deepening of wilting, the decrease of starch content is a normal physiological change of tobacco leaves, but the abnormal increase of starch content when the tobacco leaves are wilted to a water content of 50% may be due to the difference in the content of different wilted tobacco leaves, which further decomposes more starch in the fermentation stage of Example 1, so it is judged that fermentation is also an important process in the whole modulation process.

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

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

[0125] Table 5

[0126]

[0127] In combination with Table 5, comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be found that the chlorophyll and carotenoid contents in the cured tobacco leaves of Comparative Example 1 are significantly higher than those of Example 1 and Comparative Example 2. Specifically, the chlorophyll a content in the cured tobacco leaves of Example 1 and Comparative Example 2 is 0.03 mg / g lower than that of Comparative Example 1, the chlorophyll b content is 0.03 mg / g lower than that of Comparative Example 1, the carotenoid content is 0.04 mg / g and 0.05 mg / g lower than that of Comparative Example 1 respectively, the total chlorophyll content is 0.08 mg / g lower than that of Comparative Example 1, and the total amount of plastid pigments is more than 0.10 mg / g lower than that of Comparative Example 1. The above results show that the internal plastid pigments of the tobacco leaves reach the minimum value when the tobacco leaves are wilted to a moisture content of about 55%, and the degradation rate of the plastid pigments is low as the moisture content further decreases.

[0128] Comparing Example 1 with Comparative Example 3-4, it can be found that the chlorophyll a and chlorophyll b contents in the cured tobacco leaves of Example 1 and Comparative Example 4 are significantly lower than those of Comparative Example 3, the carotenoid content in the cured tobacco leaves of Example 1 is the lowest, and the carotenoid content in the cured tobacco leaves of Comparative Example 4 is the highest. The total amount of plastid pigments in the cured tobacco leaves of the three examples is significantly different, wherein the total amount of plastid pigments in the cured tobacco leaves of Example 1 is 0.10 mg / g lower than that of Comparative Example 3 and 0.03 mg / g lower than that of Comparative Example 4. This shows that the use of steaming treatment is beneficial to the degradation of macromolecular substances in the tobacco leaves.

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

[0130] Table 6

[0131]

[0132] In combination with Table 6, comparing Example 1 with Comparative Example 1 and Comparative Example 2, it can be found that the polyphenol content in the cured tobacco leaves of Example 1 is the highest, that in Comparative Example 1 is the second, and that in Comparative Example 2 is the lowest. Specifically, the total amount of polyphenols in the cured tobacco leaves of Example 1 is 14.93% and 28.61% higher than those of Comparative Example 1 and Comparative Example 2 respectively. The difference in the contents of chlorogenic acid and anortine between Comparative Example 1 and Example 1 is not significant, but both are significantly higher than those of Comparative Example 2. The contents of rutin and kaempferol in the cured tobacco leaves of Example 1 are significantly higher than those of Comparative Example 1 and Comparative Example 2. This shows that the accumulation of polyphenols reaches the peak when the tobacco leaves are wilted to a moisture content of about 55%, and the further wilting may cause the imbalance of water in the tobacco leaves and the damage of part of the membrane structure, leading to the contact between polyphenols and oxygen, and thus the oxidation loss of chlorogenic acid and rutin and the increase of the content of anortine.

[0133] Comparing Example 1 with Comparative Examples 3-4, it can be found that, in the tobacco leaves modulated by Example 1, the contents of chlorogenic acid, rutin and kaempferol are all significantly higher than those in Comparative Example 3 and Comparative Example 4, and the total amount of polyphenol aroma substances in the tobacco leaves modulated by Example 1 is 2.36 times that in Comparative Example 4 and 4.25 times that in Comparative Example 3. It is shown that the steam treatment is more conducive to the preservation of polyphenol aroma substances in tobacco leaves.

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

[0135] 1. The tobacco leaves treated by steam all have honey sweet aroma, and the honey sweet aroma in Example 1 is the most outstanding with the highest evaluation score.

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

[0137] 3. The contents of plastid pigments in the tobacco leaves modulated by Example 1 and Comparative Example 2 are both significantly lower than that in Comparative Example 1, which shows that the degradation of plastid pigments is slow when the moisture content of tobacco leaves is lower than 55%.

[0138] 4. The content of polyphenol aroma components in the tobacco leaves modulated by Example 1 is the highest, and that in Comparative Example 2 is the lowest, which shows that the moisture content of 55% is conducive to the formation and preservation of polyphenol aroma components.

[0139] In summary, it can be concluded that the wilting of tobacco leaves to a moisture content of 55% is conducive to the degradation of starch and plastid pigments and the transformation and preservation of sugar and polyphenol substances, and the steam treatment is more suitable.

[0140] Further, in the present application, the high-temperature steam inactivation of wilted tobacco leaves makes the biological enzyme activity lost, which plays a role in preserving key aroma substances and fixing the color of tobacco leaves. The degradation rate of plastid pigments in the tobacco leaves treated by steam is higher, the contents of total sugar and reducing sugar are higher than those in wilted tobacco leaves, and the total alkali content can be reduced. The content of polyphenol substances in the tobacco leaves treated by steam is much higher than that in rolled tobacco, and the color and shape of the tobacco leaves are similar to those of flue-cured tobacco. From the evaluation results, the score of the tobacco leaves treated by steam is higher, the style is caramel sweet and honey sweet, and the quality and usability are higher.

[0141] The steaming process can increase the content of total sugar and reducing sugar in tobacco leaves, which may be caused by the intense movement of polysaccharide molecules at high temperature, resulting in the breakage and decomposition of polysaccharide chains at a certain temperature, thus increasing the content of reducing sugar. The content of total alkali significantly decreases after the steaming process, which may also be caused by the breakage of nitrogen-containing functional groups due to high temperature. Based on the conventional chemical indicators, the tobacco leaves after steaming belong to high-quality tobacco leaves, and the nitrogen-alkali ratio > 1 may cause a high level of irritation. After fermentation, the contents of total sugar, reducing sugar and total alkali increase compared with those before fermentation, while potassium ions are lost, which may be caused by the degradation of polysaccharides in tobacco leaves under the action of air oxidation and microorganisms after the destruction of tobacco leaves,

[0142] From the degradation of macromolecular substances, the steaming process has a significant effect on the degradation of plastid pigments in tobacco leaves, and the degradation effect of chlorophyll is the best, which may be caused by the demetallization of chlorophyll due to high transmittance and high temperature. However, the high-moisture environment makes it difficult for tobacco leaves to further generate pyro-metallization and turn brown. The degradation efficiency of plastid pigments decreases during fermentation, which may be because most of the plastid pigments are cleaved by the steaming process. After fermentation, the color of tobacco leaves remains, which may be because the water vapor generated during the steaming process enters the interior of the tobacco leaves with cell destruction, thereby reducing the contact area between the substances in the tobacco leaves and the air and reducing the discoloration of the tobacco leaves caused by oxidation.

[0143] The steaming process is an effective method for preserving polyphenolic substances in tobacco leaves, which can effectively preserve chlorogenic acid, rutin and kaempferol in tobacco leaves, and the contents of kaempferol and rutin further increase after fermentation. Unlike the kneading process, the steaming process does not cause and promote the conversion of aroma substances, but preserves them as much as possible. Traditional baking technology believes that hot air can accelerate the volatilization of phenolic substances, but high-temperature steaming can effectively preserve them, which may be because the medium of conduction temperature has changed to water vapor.

[0144] From the smoking results, the aroma of steamed tobacco leaves is described as caramel, honey, hay but slightly green; the steamed tobacco leaves are better than the kneaded tobacco leaves in terms of aroma quality, aroma amount, sweetness, aftertaste and softness, but the irritation is higher in eating taste characteristics, which reduces the overall score of steamed tobacco leaves.

[0145] From the perspective of modulation, steaming of green tobacco leaves is essentially different from traditional flue-cured tobacco and black tea-like processing technology, and the core is to change the heat transfer medium to preserve various aroma components in tobacco leaves. In terms of conventional chemical components, total sugar, reducing sugar and total alkaloids are affected by high temperature, and steaming treatment can greatly crack plastid pigments with thermal instability. 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 steamed green tobacco leaves belong to high-quality tobacco leaves, with distinct style characteristics, and the effect of steaming is significant.

[0146] The technical features of the above-described embodiments can be combined arbitrarily, and to make the description concise, all possible combinations of the technical features in the above-described embodiments are not described, however, as long as the combinations of the technical features do not exist contradictory, they should be considered as the scope of the present disclosure.

[0147] The above-described embodiments only express several implementation manners of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that for ordinary skilled in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are all within the protection scope of the present application. Therefore, the protection scope of the present application patent should be subject to the appended claims, and the description can be used to explain the content of the claims.

Claims

1. A method of curing tobacco leaf, characterised in that, The method comprises the following steps: subjecting fresh tobacco leaves to wilting treatment to obtain first tobacco leaves; the moisture content of the first tobacco leaves is 53wt%-57wt%; subjecting the first tobacco leaves to water-steam curing treatment to obtain second tobacco leaves; the curing treatment time is 8min-12min; subjecting the second tobacco leaves to fermentation treatment and drying treatment in sequence; during the fermentation treatment, the second tobacco leaves are stacked together, and the stacking thickness of the second tobacco leaves is 4.5cm-5.5cm.

2. The modulation method of claim 1, wherein, The wilting treatment is performed in a wilting machine, and during the wilting treatment, the dry bulb temperature of the wilting machine is set to 38℃-39℃, and the wet bulb temperature is set to 35℃-36℃.

3. The modulation method of claim 1 or 2, wherein The fermentation treatment temperature is 40℃-45℃.

4. The modulation method of claim 1 or 2, wherein The fermentation treatment relative humidity is 80%-85%.

5. The modulation method of claim 1 or 2, wherein The fermentation treatment time is 10h-15h.

6. The modulation method of claim 1 or 2, wherein The drying treatment steps comprise: first, preheat a drying device, and after the temperature in the drying device reaches a first set temperature, place the tobacco leaves to be dried in the drying device for first drying treatment; the first set temperature is 80℃-90℃; the first drying treatment time is 10min-20min.

7. The modulation method of claim 6, wherein, After the first drying treatment, the drying treatment steps comprise: first, preheat a flavoring machine, and after the temperature of the flavoring machine reaches a second set temperature, place the first drying treatment tobacco leaves in the flavoring machine for second drying treatment; the second set temperature is 100℃-110℃.

8. A cured tobacco leaf, characterized by, The cured tobacco leaves are prepared according to the curing method of any one of claims 1-7.

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