Method for swelling tobacco stems, reconstituted tobacco leaves, preparation method and application thereof, and tobacco products

Abstract

The present invention belongs to the field of papermaking reconstituted tobacco leaves, and specifically relates to a method for swelling tobacco stems, comprising: washing raw tobacco stems, conveying the washed tobacco stems through a screw conveyor, and the temperature in the screw conveyor is 60°C to 80°C and the relative humidity is 65% to 90%; steaming the obtained tobacco stems through a spiral stem steamer, the temperature of the steamed stems is 70°C to 120°C, and the time is 5-30 seconds; steaming the obtained tobacco stems through a tunnel-type stem steamer, the temperature of the steamed stems is 90°C to 120°C, and the time is 5-30 seconds; soaking the obtained tobacco stems in water at 60°C to 70°C, and separating the tobacco stems. The present invention also relates to a method for preparing reconstituted tobacco leaves, reconstituted tobacco leaves and applications, and tobacco products. The method of the present invention improves the swelling effect of tobacco stems, reduces the content of hot water solubles in substrates, and improves the tobacco stem extraction rate, substrate absorbency, product yield and sensory quality.

Description

Technical Field

[0001] The invention belongs to the field of papermaking reconstituted tobacco, and specifically relates to a method for swelling tobacco stems, and also relates to a method for preparing reconstituted tobacco, the prepared reconstituted tobacco and its application, and tobacco products. Background Art

[0002] Tobacco stems are one of the main raw materials for papermaking reconstituted tobacco leaf technology. They can be used to extract tobacco extracts and provide fiber materials for making substrates. Tobacco stems have a low cellulose content, short fibers, and more miscellaneous cells. When domestic companies use papermaking to reconstitute tobacco leaves, they mostly extract and pulp the tobacco stems. The extraction and pulping effects of tobacco stems are important factors affecting production efficiency and product quality, and tobacco stem swelling is a key factor affecting the extraction and pulping effects.

[0003] Tobacco stem swelling refers to the process in which water gradually penetrates from the surface of the tobacco stem into the internal structure. The swelling method in the existing papermaking process for reconstituted tobacco is usually to soak the tobacco stems in water for a long time and store the stems for a long time. However, the tobacco stem swelling effect of this method is not ideal, which often leads to low tobacco stem extraction rate, high hot water soluble content in the produced substrate, uneven physical properties of fibers in the substrate, insufficient fiber separation, poor substrate permeability and other problems, affecting product quality and product yield; moreover, this swelling method has a long cycle, which can easily lead to production interruptions and reduce production efficiency. After soaking and storing the stems for a long time, the tobacco stems are loosened, which can easily lead to problems such as too short tobacco stem fibers, reduced fiber yield, and poor pulping effect.

[0004] Therefore, there is an urgent need for a method for swelling tobacco stems in a papermaking process for reconstituted tobacco to improve the swelling effect, thereby improving the production efficiency, product quality and product yield of the reconstituted tobacco. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for swelling tobacco stems, and the swollen tobacco stems are used in a papermaking process for reconstituted tobacco leaves. The method for swelling tobacco stems of the present invention improves the swelling effect of tobacco stems, improves the tobacco stem extraction rate and product yield in a papermaking process for reconstituted tobacco leaves, improves the absorbency of the prepared substrate, reduces the hot water soluble content in the substrate, and improves the sensory quality of the reconstituted tobacco leaves. Another purpose of the present invention is to provide a method for preparing reconstituted tobacco leaves, the prepared reconstituted tobacco leaves and their applications, and tobacco products.

[0006] A first aspect of the present invention provides a method for swelling tobacco stems, comprising the following steps:

[0007] (1) washing raw tobacco stems, conveying the washed tobacco stems through a screw conveyor to reduce moisture, and maintaining the temperature in the screw conveyor at 60° C. to 80° C. (e.g., 65° C., 70° C., 75° C.) and the relative humidity at 65% to 90% (e.g., 70%, 75%, 80%, 85%) to obtain tobacco stems;

[0008] (2) steaming the tobacco stems obtained in step (1) in a spiral stem steamer at a temperature of 70° C. to 120° C. (e.g., 80° C., 90° C., 100° C., 110° C.) for 5 to 30 seconds (e.g., 10 seconds, 15 seconds, 20 seconds, 25 seconds) to obtain tobacco stems;

[0009] (3) steaming the tobacco stems obtained in step (2) in a tunnel-type stem steamer at a temperature of 90° C. to 120° C. (e.g., 90° C., 100° C., 110° C.) for 5 to 30 seconds (e.g., 10 seconds, 15 seconds, 20 seconds, 25 seconds) to obtain tobacco stems;

[0010] (4) Soaking the tobacco stems obtained in step (3) in water at 60° C. to 70° C. (e.g., 65° C.) to separate the tobacco stems.

[0011] In any embodiment of the first aspect of the present invention, in step (2), the tobacco stems are piled in a spiral stem steamer for steaming, and the thickness of the pile is 1.5-5 cm, for example, 2 cm, 2.5 cm, 3 cm, 3.5 cm, 4 cm, 4.5 cm.

[0012] In any embodiment of the first aspect of the present invention, in step (3), the feed flow rate of the tunnel-type stem steaming machine is 900-1400 kg / h, for example, 1000 kg / h, 1100 kg / h, 1200 kg / h, 1250 kg / h, 1300 kg / h, 1350 kg / h.

[0013] In any embodiment of the first aspect of the present invention, the method comprises one or more of the following:

[0014] A. In step (1), the washing temperature is 60°C to 85°C, for example, 65°C, 70°C, 75°C, 80°C;

[0015] B. In step (1), the washing time is 1 to 30 seconds, for example, 4 seconds, 5 seconds, 10 seconds, 15 seconds, 20 seconds, 25 seconds, or 28 seconds;

[0016] C. In step (1), washing is performed using a water tank type tobacco stem rehumidification machine;

[0017] D. In step (1), the delivery time is 1-40 seconds, for example, 5, 10, 15, 20, 25, 30 seconds;

[0018] E. In step (1), the temperature and humidity in the screw conveyor are maintained by introducing water vapor;

[0019] F. In step (2), the discharge temperature of the spiral stem steamer is 70°C to 90°C, for example, 75°C, 80°C, or 85°C;

[0020] G. In step (3), the discharge temperature of the tunnel-type stem steaming machine is 75°C to 100°C, for example, 80°C, 85°C, 90°C, or 95°C;

[0021] H. In step (4), the soaking time is 5 to 60 minutes, for example, 8 minutes, 10 minutes, 15 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, or 55 minutes;

[0022] I. In step (4), stirring is performed while soaking;

[0023] J. In step (4), separation is performed by filtration;

[0024] K. In step (1), the moisture content of the raw tobacco stems is 4% W / W to 16% W / W, for example 8% W / W, 10% W / W, 12% W / W, 15% W / W;

[0025] L. The moisture content of the tobacco stems obtained in step (1) is 22% W / W to 33% W / W, for example, 25% W / W, 27% W / W, 30% W / W, 31% W / W;

[0026] M. The moisture content of the tobacco stems obtained in step (2) is 27% W / W to 37% W / W, for example 28% W / W, 30% W / W, 34% W / W, 36% W / W;

[0027] N. the moisture content of the tobacco stems obtained in step (3) is 30% W / W to 45% W / W, for example 31% W / W, 33% W / W, 34% W / W, 36% W / W, 38% W / W, 40% W / W, 42% W / W, 44% W / W;

[0028] O. The moisture content of the tobacco stems obtained in step (4) is 60% W / W to 90% W / W, for example 65% W / W, 70% W / W, 75% W / W, 80% W / W, 85% W / W, 88% W / W.

[0029] In any embodiment of the first aspect of the present invention, the moisture content of the tobacco stems obtained in step (2) is higher than the moisture content of the tobacco stems obtained in step (1), preferably 1% W / W-6% W / W higher, for example 2% W / W, 3% W / W, 4% W / W, 5% W / W.

[0030] In any embodiment of the first aspect of the present invention, the moisture content of the tobacco stems obtained in step (3) is higher than the moisture content of the tobacco stems obtained in step (2), preferably 2% W / W-8% W / W higher, for example 3% W / W, 4% W / W, 5% W / W, 6% W / W, 7% W / W.

[0031] A second aspect of the present invention provides a method for preparing reconstituted tobacco, comprising the following steps:

[0032] 1) swelling tobacco stems according to the steps of the method of the first aspect of the present invention;

[0033] 2) extracting the tobacco stems obtained in step 1) with water, separating the solid from the liquid, and obtaining a liquid phase and a solid phase;

[0034] 3) preparing the liquid phase into a coating liquid;

[0035] 4) making the solid phase into a substrate;

[0036] 5) Applying the coating liquid on the surface of the substrate and drying it to obtain reconstituted tobacco leaves.

[0037] In any embodiment of the second aspect of the present invention, the method comprises one or more of the following:

[0038] a. In step 2), the extraction temperature is 55°C-80°C, for example 60°C, 65°C, 70°C, 75°C;

[0039] b. In step 2), the extraction time is 5-30 minutes, for example 8, 10, 13, 15, 18, 20, 23, 25, 28 minutes;

[0040] c. Step 2), solid-liquid separation by centrifugation;

[0041] d. Step 3), the liquid phase is concentrated to obtain a coating solution;

[0042] e. In step 4), the solid phase is sequentially subjected to coarse fiber disintegration, high-concentration pulping, low-concentration pulping, refined pulping and papermaking to obtain a substrate;

[0043] f. In step 5), the reconstituted tobacco leaves are cut.

[0044] In any embodiment of the second aspect of the present invention, the absorbency of the substrate is 15 to 25 mm / min, for example 16 mm / min, 17 mm / min, 18 mm / min, 19 mm / min, 20 mm / min, 21 mm / min, 22 mm / min, 23 mm / min; and / or,

[0045] The hot water soluble matter content in the substrate is 7% W / W to 9.5% W / W, for example 7.5% W / W, 8% W / W, 8.5% W / W, 9% W / W, 9.4% W / W; and / or,

[0046] The extraction rate of tobacco stems is 44% W / W to 55% W / W, such as 45% W / W, 46% W / W, 47% W / W, 48% W / W, 50% W / W, 52% W / W, 54% W / W; and / or,

[0047] The product yield is 84% ​​to 98%, for example 85%, 87%, 89%, 90%, 93%, 95%, 97%.

[0048] In the present invention, the absorbency of the substrate refers to the water absorption of the substrate, which can be measured by conventional methods. For example, the following method can be used: 1) adjust the scale of the water absorption rate measuring instrument to the lowest position, inject distilled water into the water tank of the water absorption rate measuring instrument, and adjust the instrument so that the water surface and the zero point of all scales are on the same horizontal line; 2) raise the scale to a higher position, hang the substrate vertically on one side of the scale, and the bottom of the substrate is 10mm lower than the zero point of the scale; lower the scale and the sample together until the zero point of the scale just touches the water surface and the substrate extends 10mm into the water, then stop lowering, and start timing at this time; after the 10-minute timing is over, immediately raise the scale and the substrate together, and read the reading on the scale corresponding to the wetting line on the substrate (accurate to 1mm).

[0049] In the present invention, the hot water soluble matter content in the substrate can be determined by conventional methods. For example, it can be measured by the following method: dry the substrate until the weight no longer changes, weigh the absolute dry weight of the substrate; put the dried substrate into a previously dried crucible, add water to the crucible, heat to boiling and keep boiling for 60 minutes, collect the filter residue into the crucible after suction filtration, wash the filter residue with water, and rinse the wall-hanging filter residue back into the crucible with water, collect the filter residue into the crucible after suction filtration, place it in a blast drying oven at 120±2℃ and dry it to constant weight, cool it to room temperature in a dryer, and weigh it; calculate the hot water soluble matter content in the substrate according to the following formula;

[0050]

[0051] in,

[0052] C represents the hot water soluble content in the substrate (% W / W);

[0053] N represents the absolute dry weight of the substrate (g);

[0054] m1 represents the absolute dry weight of the crucible (g);

[0055] m2 represents the total weight of the substrate and crucible after drying (g).

[0056] In the present invention, the extraction rate of tobacco stems can be measured by conventional methods. For example, it can be measured by the following method: the tobacco stems and the precipitate remaining after extraction are dried separately until the weight no longer changes, the absolute dry weight of the tobacco stems and the absolute dry weight of the precipitate are weighed, and the tobacco stem extraction rate is calculated according to the following formula;

[0057]

[0058] in,

[0059] T represents the tobacco stem extraction rate (% W / W);

[0060] M represents the dry weight of tobacco stems (g);

[0061] m represents the absolute dry weight of the precipitate (g).

[0062] In the present invention, the product yield can be measured by conventional methods. For example, it can be measured by the following method: the product yield is calculated according to the following formula;

[0063]

[0064] in,

[0065] X represents the product yield (%);

[0066] W represents the total weight of reconstituted tobacco produced (g);

[0067] Y represents the total weight (g) of raw tobacco stems consumed in production.

[0068] The third aspect of the present invention provides a reconstituted tobacco leaf, which is produced by the method of the second aspect of the present invention.

[0069] The fourth aspect of the present invention provides a tobacco product, comprising the reconstituted tobacco leaf of the third aspect of the present invention;

[0070] Preferably, the tobacco product is a cigarette.

[0071] The fifth aspect of the present invention provides the use of the reconstituted tobacco leaf of the third aspect of the present invention in the preparation of tobacco products;

[0072] Preferably, the tobacco product is a cigarette.

[0073] In the present invention, the screw conveyor is a conventional device in the art.

[0074] In the present invention, the spiral stem steaming machine is a conventional device in the art.

[0075] In the present invention, the tunnel-type stem steaming machine is also a conventional device in the art.

[0076] Beneficial effects achieved by the present invention:

[0077] 1. The method for swelling tobacco stems of the present invention improves the swelling effect of tobacco stems, improves the tobacco stem extraction rate and product yield in the papermaking process of reconstituted tobacco leaves, improves the absorbency of the prepared substrate, and reduces the hot water soluble content in the substrate.

[0078] 2. The method for swelling tobacco stems of the present invention improves the aroma and aftertaste of cigarettes made from reconstituted tobacco leaves when smoked, reduces the foreign smell and irritation when smoked, and significantly improves the overall sensory quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein

[0080] Figure 1 The present invention is a flow chart of the papermaking method for reconstructing tobacco leaves. DETAILED DESCRIPTION

[0081] Example 1

[0082] The papermaking process for reconstructing tobacco leaves of the present invention is as follows Figure 1 As shown, it includes:

[0083] (1) placing tobacco stem raw materials with a water content of 12% W / W into a water trough type tobacco stem rehumidification machine for washing, wherein the water temperature for washing the stems is 70° C. and the washing time is 4 seconds; taking out the washed tobacco stems, placing them into a screw conveyor for conveying for 30 seconds while introducing water vapor, maintaining the temperature in the screw conveyor at 65° C. and the relative humidity at 70%, so that the inside of the tobacco stems swells in a high temperature and high humidity environment, and at the same time, filtering out excess water on the surface of the tobacco stems through the screw conveyor, thereby obtaining tobacco stems with a water content of 27% W / W;

[0084] (2) piling the tobacco stems obtained in step (1) in a spiral stem steamer for steaming, wherein the thickness of the material stacking is 3 cm, the temperature of the steaming is 100° C., the time of the steaming is 10 seconds, and the discharge temperature is 80° C., to obtain tobacco stems with a moisture content of 30% w / w;

[0085] (3) feeding the tobacco stems obtained in step (2) into a tunnel-type stem steamer for further steaming, with a feed rate of 1250 kg / h, a steaming temperature of 100° C., a steaming time of 10 seconds, and a discharge temperature of 85° C. to obtain tobacco stems with a moisture content of 34% W / W;

[0086] (4) immersing the tobacco stems obtained in step (3) in 65° C. water for 10 minutes while stirring to allow the tobacco stems to swell fully, and filtering to obtain tobacco stems having a water content of 80% w / w;

[0087] (5) The tobacco stems obtained in step (4) are extracted with water at 65° C. for 10 minutes, and centrifuged to obtain a liquid and a precipitate respectively; the precipitate is subjected to coarse fiberizing, high-concentration pulping, low-concentration pulping, refined pulping, and papermaking in sequence to obtain a substrate; the liquid is concentrated to obtain a coating liquid; the coating liquid is applied to the substrate, and the substrate is dried and cut to obtain a reconstituted tobacco leaf product 1.

[0088] Example 2

[0089] The papermaking process for reconstructing tobacco leaves of the present invention is as follows Figure 1 As shown, it includes:

[0090] (1) placing tobacco stem raw materials with a water content of 12% W / W into a water trough type tobacco stem rehumidification machine for washing, wherein the water temperature for washing the stems is 75° C. and the washing time is 5 seconds; taking out the washed tobacco stems, placing them into a screw conveyor for conveying for 30 seconds while introducing water vapor, maintaining the temperature in the screw conveyor at 70° C. and the relative humidity at 75%, so that the inside of the tobacco stems swells in a high temperature and high humidity environment, and at the same time, filtering out excess water on the surface of the tobacco stems through the screw conveyor, thereby obtaining tobacco stems with a water content of 30% W / W;

[0091] (2) piling the tobacco stems obtained in step (1) in a spiral stem steamer for steaming, wherein the thickness of the material stacking is 2.5 cm, the temperature of the steaming is 100° C., the time of the steaming is 15 seconds, and the discharge temperature is 80° C., to obtain tobacco stems with a moisture content of 34% w / w;

[0092] (3) feeding the tobacco stems obtained in step (2) into a tunnel-type stem steamer for further steaming, with a feed rate of 1000 kg / h, a stem steaming temperature of 100° C., a stem steaming time of 15 seconds, and a discharge temperature of 90° C. to obtain tobacco stems with a moisture content of 38% W / W;

[0093] (4) immersing the tobacco stems obtained in step (3) in 65° C. water for 8 minutes while stirring to allow the tobacco stems to swell fully, and filtering to obtain tobacco stems having a water content of 85% w / w;

[0094] (5) The tobacco stems obtained in step (4) are extracted with water at 65° C. for 10 minutes, and centrifuged to obtain a liquid and a precipitate respectively; the precipitate is subjected to coarse fiberizing, high-concentration pulping, low-concentration pulping, refined pulping, and papermaking in sequence to obtain a substrate; the liquid is concentrated to obtain a coating liquid; the coating liquid is applied to the substrate, and the substrate is dried and cut to obtain a reconstituted tobacco leaf product 2.

[0095] Comparative Example

[0096] The tobacco stem raw material is directly extracted with 65°C water for 30 minutes and then centrifuged to obtain a liquid and a precipitate respectively; the precipitate is subjected to coarse fiberizing, high-concentration pulping, low-concentration pulping, refined pulping and papermaking in sequence to obtain a substrate; the liquid is concentrated to obtain a coating liquid; the coating liquid is applied to the substrate, and after drying and cutting, a reconstituted tobacco leaf product M is obtained.

[0097] Experimental Example 1

[0098] The tobacco stem extraction rate, substrate absorbency, hot water soluble matter content in the substrate and product yield of Examples 1-2 and the comparative example were measured.

[0099] (1) Determination of tobacco stem extraction rate

[0100] The washed tobacco stems and the precipitate are dried separately until the weight no longer changes, the absolute dry weight of the washed tobacco stems and the absolute dry weight of the precipitate are weighed, and the tobacco stem extraction rate is calculated according to the following formula;

[0101]

[0102] in,

[0103] T represents the tobacco stem extraction rate (% W / W);

[0104] M represents the absolute dry weight of washed tobacco stems (g);

[0105] m represents the absolute dry weight of the precipitate (g).

[0106] (2) Determination of substrate absorbency

[0107] (2.1) Instrument and sample preparation:

[0108] Water absorption tester, scale graduation value 1mm;

[0109] The substrate was made into samples with a size of 250 × 15 mm;

[0110] (2.2) Determination method:

[0111] 1) Adjust the scale of the water absorption meter to the lowest position, inject distilled water into the water tank of the water absorption meter, and adjust the support feet of the instrument so that the water surface and the zero point of all scales are on the same horizontal line;

[0112] 2) Turn the handle of the water absorption meter to raise the ruler to a higher position, and hang the sample vertically on one side of the ruler, with the bottom of the sample 10mm lower than the zero point of the ruler; turn the handle to lower the ruler and the sample together until the zero point of the ruler just touches the water surface and the sample is inserted into the water for 10mm and then stops descending. Start timing at this time; after the 10-minute timing is over, immediately raise the ruler and the sample together, and read the reading on the ruler corresponding to the wetting line on the sample (accurate to 1mm); if the wetting line is inclined or curved, read the reading according to the average height.

[0113] (3) Determination of hot water soluble content in substrate

[0114] Dry the substrate until the weight no longer changes, and weigh the absolute dry weight of the substrate. Place the dried substrate in a previously dried crucible, add 100±5mL of deionized water to the crucible, heat to boiling and keep boiling for 60min, collect the filter residue in the crucible after suction filtration, wash the filter residue twice with 100±10mL of deionized water, and then rinse the wall-hanging filter residue back into the crucible twice with no more than 20mL of deionized water, collect the filter residue in the crucible after suction filtration, place in a 120±2℃ forced air drying oven to dry to constant weight, place in a desiccator to cool to room temperature, and weigh. Calculate the hot water soluble content in the substrate according to the following formula.

[0115]

[0116] in,

[0117] C represents the hot water soluble content in the substrate (% W / W);

[0118] N represents the absolute dry weight of the substrate (g);

[0119] m1 represents the absolute dry weight of the crucible (g);

[0120] m2 represents the total weight of the substrate and crucible after drying (g).

[0121] (4) Calculation of product yield

[0122] The product yield is calculated according to the following formula;

[0123]

[0124] in,

[0125] X represents the product yield (%);

[0126] W represents the total weight of reconstituted tobacco produced (g);

[0127] Y represents the total weight (g) of tobacco stem raw material consumed in production.

[0128] The above results are shown in Table 1.

[0129] Table 1

[0130]

[0131] It can be seen from Table 1 that, compared with the process of the comparative example, the tobacco stem extraction rate of the process of Example 1 of the present invention is increased by 7.1%, the absorbency of the prepared substrate is increased by 12.1%, the hot water soluble content in the substrate is decreased by 8%, and the product yield is increased by 7.5%; compared with the process of the comparative example, the tobacco stem extraction rate of the process of Example 2 of the present invention is increased by 12%, the absorbency of the prepared substrate is increased by 15%, the hot water soluble content in the substrate is decreased by 15%, and the product yield is increased by 13.8%; this shows that the tobacco stem extraction rate of the process of the present invention is significantly improved, the absorbency of the prepared substrate is significantly increased, the hot water soluble content in the substrate is significantly decreased, and the product yield is significantly improved, and the process of Example 2 of the present invention further improves the tobacco stem extraction rate and the absorbency of the substrate, further reduces the hot water soluble content in the substrate, and at the same time further improves the product yield.

[0132] Experimental Example 2

[0133] The reconstituted tobacco product 1-2 and the reconstituted tobacco product M are cut into shreds and made into cigarettes 1-2 and M according to the same conventional method, wherein the content of reconstituted tobacco in the cigarettes is the same, and the cigarettes do not contain other shredded tobacco except the reconstituted tobacco.

[0134] According to the national standard GB5606.6-2005 "Cigarettes", the sensory quality of cigarettes 1-2 and M was evaluated. A difference of 0.5 points can be considered as a difference of one grade. The results are shown in Table 2.

[0135] Table 2

[0136]

[0137]

[0138] It can be seen from Table 2 that, compared with the process of the comparative example, the aroma of the cigarettes produced by the process of the present invention is significantly improved, the impurities and irritation are significantly reduced, the aftertaste is significantly improved, and the overall sensory quality is significantly improved.

[0139] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for swelling tobacco stems, comprising the following steps: (1) Washing the raw tobacco stems, conveying the washed tobacco stems through a screw conveyor, and maintaining the temperature and humidity in the screw conveyor by introducing water vapor, wherein the temperature in the screw conveyor is maintained at 60°C to 80°C, and the relative humidity is maintained at 65% to 90%, and the conveying time is 1 to 40 seconds, thereby obtaining tobacco stems; (2) piling the tobacco stems obtained in step (1) in a spiral stem steamer to steam the stems to a thickness of 1.5-5 cm at a temperature of 70° C. to 120° C. for 5-30 seconds to obtain tobacco stems; (3) steaming the tobacco stems obtained in step (2) in a tunnel-type stem steamer at a temperature of 90°C to 120°C for 5 to 30 seconds and a feed flow rate of 900 to 1400 kg / h to obtain tobacco stems; (4) Soaking the tobacco stems obtained in step (3) in water at 60°C to 70°C to separate the tobacco stems.

2. The method according to claim 1, characterized in that One or more of the following: A. In step (1), the washing temperature is 60°C to 85°C; B. In step (1), the washing time is 1 to 30 seconds; C. In step (1), washing the tobacco stems in a water tank type tobacco stem rehumidification machine; D. In step (2), the discharge temperature of the spiral steamer is 70°C to 90°C; E. In step (3), the discharge temperature of the tunnel-type stem steaming machine is 75°C to 100°C; F. In step (4), the soaking time is 5 to 60 minutes; G. In step (4), stirring is performed while soaking; H. In step (4), separation is performed by filtration; I. In step (1), the moisture content of the raw tobacco stems is 4% W / W to 16% W / W; J. The moisture content of the tobacco stems obtained in step (1) is 22% W / W to 33% W / W; K. The moisture content of the tobacco stems obtained in step (2) is 27% W / W to 37% W / W; L. The moisture content of the tobacco stems obtained in step (3) is 30% W / W to 45% W / W; M. The moisture content of the tobacco stems obtained in step (4) is 60% W / W to 90% W / W.

3. A method for preparing reconstituted tobacco, comprising the following steps: 1) swelling tobacco stems according to the steps of the method of claim 1 or 2; 2) extracting the tobacco stems obtained in step 1) with water, separating the solid from the liquid, and obtaining a liquid phase and a solid phase; 3) preparing the liquid phase into a coating liquid; 4) Making the solid phase into a substrate; 5) Applying the coating liquid on the surface of the substrate and drying it to obtain reconstituted tobacco leaves.

4. The method according to claim 3, characterized in that One or more of the following: a. In step 2), the extraction temperature is 55°C-80°C; b. In step 2), the extraction time is 5-30 minutes; c. In step 2), solid-liquid separation is performed by centrifugation; d. In step 3), the liquid phase is concentrated to obtain a coating solution; e. In step 4), the solid phase is subjected to coarse fiber disintegration, high-concentration pulping, low-concentration pulping, refined pulping and papermaking in sequence to obtain a substrate; f. In step 5), the reconstituted tobacco leaves are cut.

5. The method according to claim 3 or 4, wherein: The substrate has an absorbency of 15 to 25 mm / min; and / or, The hot water soluble matter content in the substrate is 7% W / W to 9.5% W / W; and / or, The extraction rate of tobacco stems is 44% W / W to 55% W / W; and / or, The product yield is 84%~98%.

6. A reconstituted tobacco leaf, produced by the method according to any one of claims 3 to 5.

7. A tobacco product comprising the reconstituted tobacco leaf according to claim 6.

8. The tobacco product according to claim 7, which is a cigarette.

9. Use of the reconstituted tobacco leaf according to claim 6 in the preparation of tobacco products.

10. The use according to claim 9, wherein: The tobacco product is a cigarette.

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