A curing process for one-time harvesting of 4-6 upper leaves of flue-cured tobacco

Abstract

The application discloses a kind of baking process of flue-cured tobacco upper leaf 4-6 pieces one-time collection, comprising the following steps: 1) when upper leaf collection maturity requirement reaches maturity, one-time collection flue-cured tobacco upper leaf 4-6 pieces leaf;2) weaving pole baking;3) using the baking process of flue-cured tobacco upper leaf 4-6 pieces one-time collection;The application is one-time collection to flue-cured tobacco upper leaf 4-6 pieces, improves the quality and availability of upper leaf, and the average price of upper leaf baking is 0.83 yuan more than conventional, excellent tobacco is 10.39 percentage points more, orange yellow tobacco is 1.61 percentage points more, and colorless and colorless tobacco is reduced by 2.43 percentage points, single leaf weight is 0.19g, and the comprehensive benefit of one-time collection per kilogram of dry tobacco is 31.71 yuan, 1.2 yuan higher than conventional, tobacco chemical composition is coordinated, and the industrial availability of flue-cured tobacco upper leaf is improved.

Description

Technical Field

[0001] This invention relates to a curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation, belonging to the field of tobacco curing technology. Background Technology

[0002] Fresh tobacco leaves harvested from the field are placed in specific processing equipment (usually called a curing barn) in a certain way to artificially create suitable temperature and humidity conditions, so that the color of the tobacco leaves changes from green to yellow and they are continuously dehydrated and dried, realizing the whole process of curing the tobacco leaves to yellow, dry and fragrant.

[0003] Tobacco leaf harvesting must be carried out in stages, with each harvest requiring the same variety, the same part of the plant, and the same degree of maturity. This facilitates curing, ensuring a consistent rate of decomposition and transformation of the tobacco's internal substances, as well as a uniform yellowing and drying speed, thus guaranteeing the quality of the cured tobacco. Currently, cigarette manufacturers have a large amount of unsuitable tobacco leaves in their inventory, with 60% originating from the upper leaves. The upper 4-6 leaves of flue-cured tobacco, due to their relatively thicker thickness, lower moisture content, and slower maturity, are prone to being under-ripened or over-ripened when harvested using conventional methods (low-temperature slow-curing three-stage curing process). This can lead to issues such as ash residue, green veins, discoloration, and excessively dark coloring after curing. Summary of the Invention

[0004] Based on the above, the present invention provides a curing process for harvesting 4-6 upper leaves of flue-cured tobacco in one go. By harvesting 4-6 upper leaves without stems in one go, the harvesting and curing steps are reduced and the harvesting and curing cycle is shortened. At the same time, a medium-moisture curing process is adopted, thereby improving the quality and industrial usability of the upper tobacco leaves.

[0005] The technical solution of this invention is: a curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation, comprising:

[0006] S1. Tobacco Leaf Harvesting

[0007] When the maturity of the upper leaves meets the requirements of the processing technology, harvest 4-6 upper leaves at once.

[0008] S2, woven pipe tobacco

[0009] Tie the poles according to the same variety and the same part of the plant. The same leaves should be on the same pole when they are ripe and of the same length. Do not tie poles to severely diseased or damaged leaves.

[0010] S3, Baking and Seasoning

[0011] Baking and preparation are carried out according to the following steps:

[0012] S31. Maintain a steady low flame, simultaneously raising the dry bulb temperature to 32±1℃, then raising it to 36℃ at a rate of 1℃ / h, with a dry-wet difference of 1-2℃. Run the fan at 720r / min until the blade tips begin to turn yellow and soften, and the blades become warm to the touch.

[0013] S32. Raise the dry bulb temperature to 38℃ at a rate of 1℃ / h, with a dry-wet difference of 2℃, and run the fan at 720r / min until the leaves in the high-temperature layer are 70-80% yellow, soften, and begin to wilt; raise the temperature to 40℃ at a rate of 1℃ / 2h, with a wet bulb temperature of 36℃, and run the fan at 1440r / min until the leaves in the high-temperature layer are 80-90% yellow, soften, and collapse, with a water loss of 20%;

[0014] S33. Raise the dry bulb temperature to 42℃ at 1℃ / 2h, the wet bulb temperature to 36℃, and run the fan at 1440r / min. Stabilize the temperature until the veins of the tobacco leaves in the high-temperature layer turn white, the tobacco leaves fully collapse and the main ribs soften, and the tobacco leaves in the low-temperature layer turn 80-90% yellow and the leaves soften.

[0015] S34. Heat the fire to a high temperature, raising the dry bulb temperature to 44℃ at a rate of 1℃ / 2-3h, with the wet bulb temperature at 37℃. Run the fan at 1440r / min and stabilize the temperature until the small veins of the tobacco leaves in the mid-temperature layer turn completely white and the tips curl. Extend the temperature stabilization for 10 hours, raising the temperature to 48℃ at a rate of 1℃ / 2-3h, with the wet bulb temperature at 37-38℃. Stabilize the temperature and remove moisture until the main veins of the tobacco leaves turn white and the leaves lose 50% of their water content.

[0016] S35. Increase the dry bulb temperature to 54℃ in 1℃ / 2-3h, and the wet bulb temperature to 38-39℃. During the temperature stabilization stage, adjust the fan to 720r / min. Stabilize the temperature and remove moisture until the whole dry sheet roll is dry. Stabilize the temperature for 8 hours to promote softening and aroma, and reduce the color difference between the front and back of the leaf.

[0017] S36. Increase the temperature to 60℃ at a rate of 1℃ / h, maintain the wet-bulb temperature at 39-40℃, and keep the temperature stable for 10 hours until the main stem of the tobacco leaf is half dry. Then increase the temperature to 65-68℃ at a rate of 1℃ / h, with a maximum of 70℃. Use a fan at 720r / min and control the wet-bulb temperature at 41℃ and keep it stable. Maintain stable temperature and humidity until all the tobacco leaves are dry.

[0018] Optionally, the standard for the upper leaves to reach maturity is a curing process in which 4-6 upper leaves of flue-cured tobacco are harvested at once. The standard for the upper leaves to reach maturity is that the main vein of the upper tobacco leaf turns white and shiny, the yellow veins on the leaf surface are bright white, the basic color is greenish-yellow, mainly yellow, the leaf surface is fully yellowed, wrinkled, with obvious maturity spots, with withered tips and scorched edges, the leaf auricles turn yellow, the leaf surface hairs fall off and become shiny, the main vein is completely white, more than 2 / 3 of the branch veins turn white and shiny, the stem-leaf angle is significantly increased, the leaf tip droops, the leaf edge is curved and wrinkled, the sound is crisp when harvested, the cross-section is neat, without stem bark, and the leaf age is 70 to 90 days.

[0019] Optionally, 20-25 days after topping, the main vein of the tobacco leaves turns white and shiny, and the leaf surface turns yellowish-green. 4-6 leaves are harvested at once.

[0020] Optionally, when weaving the pipes, each pipe has 60 loops, with 2-3 pieces per loop. After weaving the standard pipes, only 5-8cm of length remains at both ends of the pipe.

[0021] The beneficial effects of this invention are:

[0022] 1. This invention changes the traditional low-temperature slow-curing process and adopts a medium-temperature, medium-humidity curing process to cure the top 4-6 tobacco leaves in the same batch. It improves the curing process for color fixing and reduces the harm to tobacco quality caused by browning during curing. Because the top 4-6 tobacco leaves are relatively thick, have low moisture content, and mature slowly, conventional harvesting and curing methods can easily lead to some tobacco leaves being harvested under-ripe or over-ripe. After curing, the tobacco leaves are prone to phenomena such as ash, green veins, discoloration, and excessively dark color. When the temperature exceeds 45℃, the relative humidity in the curing barn is above 60%, and the water loss of the tobacco leaves is less than 50%, due to enzyme activity and material transformation, the color of the tobacco leaves gradually changes from yellow to darker, eventually turning brown or tan. The tobacco leaves are prone to browning, which is harmful to the quality of the tobacco leaves. This invention controls the temperature and humidity in the curing barn during the color-fixing period of tobacco curing, adjusts the temperature stabilization time, reduces the harm of enzymatic browning reaction to tobacco leaves, controls the curing barn temperature at 44℃ and humidity at 37℃, and operates the fan at 1440r / min. After the tobacco leaves turn yellow, they lose water and reach the point of tip curling. Extending the temperature stabilization time by 10 hours promotes the reaction of sugars and amino acids to form aroma substances, deepens the color of tobacco leaves, makes the tobacco leaves less prone to browning, and improves the quality of tobacco curing.

[0023] 2. This invention involves harvesting 4-6 upper leaves without stems in a single operation, reducing the number of harvesting and curing steps and shortening the harvesting and curing cycle. Furthermore, the use of a medium-moisture curing process improves the quality and industrial usability of the upper leaves. Specifically, after adopting this invention, the average price of harvested and cured upper leaves is 0.83 yuan higher than conventional methods, with a 10.39 percentage point increase for high-grade tobacco, a 1.61 percentage point increase for orange-yellow tobacco, and a 2.43 percentage point decrease for mixed-color tobacco. The average weight of a single leaf is 0.19g, and the overall benefit of a single harvest and curing operation per kilogram of dry tobacco is 31.71 yuan, 1.2 yuan higher than conventional methods. The chemical composition of the tobacco leaves is also more balanced, improving the industrial usability of the upper leaves of flue-cured tobacco. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Example 1

[0026] A curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation includes:

[0027] S1. Tobacco Leaf Harvesting

[0028] When the upper leaves reach maturity, harvest 4-6 leaves at once. The standard for mature upper leaves is that the basic color of the tobacco leaf is yellow, the leaf surface is fully yellowed, wrinkled, with obvious maturity spots, withered tips and scorched edges, the leaf auricles are yellowed, the leaf surface hairs have fallen off and it is shiny, the main vein is completely white, more than 2 / 3 of the branch veins are white and shiny, the stem-leaf angle is significantly increased, the leaf tip is drooping, the leaf edge is curved and wrinkled, the sound is crisp when harvesting, the cross-section is neat, the stem bark is not included, and the leaf age is 70-90 days. The key points of the technique for harvesting 4-6 upper leaves of flue-cured tobacco at once: 20-25 days after topping, the tobacco leaf shows that the main vein has turned white and shiny, and the leaf surface is yellowish-green. Harvest 4-6 leaves at once.

[0029] S2, woven pipe tobacco

[0030] The tobacco poles should be tied according to the same variety and part of the plant, and the same ripe leaves and leaves should be tied to the same pole. Severely diseased or damaged leaves should not be tied to the pole. Each pole should have about 60 knots, with 2-3 leaves per knot. After the standard poles are tied, only 5-8cm of length should be left at both ends of the pole.

[0031] S3, Baking and Seasoning

[0032] Baking and preparation are carried out according to the following steps:

[0033] S31. Maintain a steady low flame, simultaneously raising the dry bulb temperature to 32±1℃, then raising it to 36℃ at a rate of 1℃ / h, with a dry-wet difference of 1-2℃. Run the fan at 720r / min until the blade tips begin to turn yellow and soften, and the blades become warm to the touch.

[0034] S32. Raise the dry bulb temperature to 38℃ at a rate of 1℃ / h, with a dry-wet difference of 2℃, and run the fan at 720r / min until the leaves in the high-temperature layer are 70-80% yellow, soften, and begin to wilt; raise the temperature to 40℃ at a rate of 1℃ / 2h, with a wet bulb temperature of 36℃, and run the fan at 1440r / min until the leaves in the high-temperature layer are 80-90% yellow, soften, and collapse, with a water loss of 20%;

[0035] S33. Raise the dry bulb temperature to 42℃ at 1℃ / 2h, the wet bulb temperature to 36℃, and run the fan at 1440r / min. Stabilize the temperature until the veins of the tobacco leaves in the high-temperature layer turn white, the tobacco leaves fully collapse and the main ribs soften, and the tobacco leaves in the low-temperature layer turn 80-90% yellow and the leaves soften.

[0036] S34. Heat the fire to a high temperature, raising the dry bulb temperature to 44℃ at a rate of 1℃ / 2-3h, with the wet bulb temperature at 37℃. Run the fan at 1440r / min and stabilize the temperature until the small veins of the tobacco leaves in the mid-temperature layer turn completely white and the tips curl. Extend the temperature stabilization for 10 hours, raising the temperature to 48℃ at a rate of 1℃ / 2-3h, with the wet bulb temperature at 37-38℃. Stabilize the temperature and remove moisture until the main veins of the tobacco leaves turn white and the leaves lose 50% of their water content.

[0037] S35. Increase the dry bulb temperature to 54℃ in 1℃ / 2-3h, and the wet bulb temperature to 38-39℃. During the temperature stabilization stage, adjust the fan to 720r / min. Stabilize the temperature and remove moisture until the whole dry sheet roll is dry. Stabilize the temperature for 8 hours to promote softening and aroma, and reduce the color difference between the front and back of the leaf.

[0038] S36. Increase the temperature to 60℃ at a rate of 1℃ / h, maintain the wet-bulb temperature at 39-40℃, and keep the temperature stable for 10 hours until the main stem of the tobacco leaf is half dry. Then increase the temperature to 65-68℃ at a rate of 1℃ / h, with a maximum of 70℃. Use a fan at 720r / min and control the wet-bulb temperature at 41℃ and keep it stable. Maintain stable temperature and humidity until all the tobacco leaves are dry.

[0039] Compare with Example 1

[0040] S1. Tobacco Leaf Harvesting

[0041] Harvest one leaf at a time when the upper 4-6 leaves are mature, in 2-3 harvests. The upper leaves are considered mature when the basic color of the tobacco leaf is yellow, the leaf surface is fully yellowed, wrinkled, with obvious maturity spots, withered tips and scorched edges, the leaf auricles are yellowed, the leaf surface hairs have fallen off and it is glossy, the main vein is completely white, more than 2 / 3 of the branch veins are white and shiny, the angle between the stem and leaf is significantly increased, the leaf tip is drooping, the leaf edge is curved and wrinkled, the sound is crisp when harvested, the cross-section is neat, the stem bark is not included, and the leaf age is 70-90 days.

[0042] S2, woven pipe tobacco

[0043] The tobacco poles should be tied according to the same variety and part of the plant, and the same ripe leaves and leaves should be tied to the same pole. Severely diseased or damaged leaves should not be tied to the pole. Each pole should have about 60 knots, with 2-3 leaves per knot. After the standard poles are tied, only 5-8cm of length should be left at both ends of the pole.

[0044] S3, Baking and Seasoning

[0045] Baking is performed using a low-temperature, slow-bake, three-stage baking process, the specific process of which is as follows:

[0046] After ignition, maintain a steady low flame, increasing the temperature at a rate of 1℃ / h to 34.0℃~35.0℃, controlling the humidity at 33.0℃~35.0℃, and hold this temperature for 20~25 hours, until the tobacco leaves in the observation layer turn 40%~60% yellow; then, increase the temperature at a rate of 1℃ / 2h to 38.0℃, maintaining the humidity at 34.0℃~36.0℃, and hold this temperature for 15~20 hours, until the tobacco leaves in the observation layer turn 70%~80% yellow; then, increase the temperature at a rate of 1℃ / 2h to 38.0℃, controlling the humidity at 34.0℃~36.0℃, and hold this temperature for 15~20 hours, until the tobacco leaves in the observation layer turn 70%~80% yellow; finally, increase the temperature at a rate of 1℃ / 2h... The temperature is increased to 40℃ at a rate of 2 hours, with a humidity of 32.0℃~34.0℃, and then maintained at a stable temperature for 10~15 hours until the tobacco leaves in the observation layer turn yellow with green veins. Then, the temperature is increased to 42.0℃ at a rate of 1℃ / 2h~3h, with a humidity of 33.0℃, and maintained at a stable temperature for 10~20 hours until the tobacco leaves in the observation layer turn completely yellow and collapse, and 1 / 4 to 1 / 3 of the main veins of the tobacco leaves turn white and shiny. After this, the color-fixing period begins. Color-fixing period: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] The temperature starts at 42.0℃ and increases by 3℃ each time, with a heating rate of 1℃ / 2h to 3h, and a stabilization period of 6h. Specifically, when the temperature is between 45.0℃ and 47.0℃, the tobacco leaves are baked at a stable temperature until the main veins turn white and shiny, and the leaf tips are dry; when the temperature is between 53.0℃ and 55.0℃, the leaves are baked at a stable temperature until they are dry; during the color-fixing period, the temperature is between 42.1℃ and 48.0℃, and the humidity is between 32.0℃ and 34.0℃; during the color-fixing period, the temperature is between 48.1℃ and 55.0℃, and the humidity is 35℃; during the dry-bulb stage: after the tobacco leaves have reached the color-fixing stage requirements, the dry-bulb temperature starts at 55.0℃ and increases to 68℃, with a heating rate of 1℃ to 2℃ / h, and is baked at a stable temperature of 60.0℃ for 8h, and then at 68℃ until the main veins of all the tobacco leaves in the kiln are completely dry; the humidity during the dry-bulb stage is between 38.0℃ and 40.0℃.

[0047] Both Example 1 and Control Example 1 involved harvesting tobacco leaves from the same plot of land. The tobacco variety was Yunyan 87. Example 1 used three curing barns, numbered Treatment 1, 2, and 3. The Control Example used one curing barn, numbered Treatment 4. Both barns were large-scale, intensive curing barns. Energy consumption, labor costs, quality of medium-grade tobacco, output value, yield, tobacco appearance quality evaluation, and tobacco chemical composition evaluation were recorded.

[0048] 1. Comparison of fresh tobacco leaf weight, dry tobacco weight, fresh-to-dry ratio, number of harvestable leaves, and curing area.

[0049] Table 1 Comparison of tobacco loading and dry weight under different harvesting and curing methods

[0050]

[0051]

[0052] As shown in Table 1, under the same tobacco loading capacity, the average yield of the curing barn using the one-time harvesting and curing method is 459.77 kg of dry tobacco, with an average fresh-to-dry ratio of 8.7 and a curing area of ​​1.07 hectares. The average yield of the conventional harvesting and curing method is 454.55 kg of dry tobacco, with a fresh-to-dry ratio of 8.8 and a curing area of ​​1.07 hectares. The fresh-to-dry ratio of the one-time harvesting and curing method is 0.1 higher than that of the conventional method, and the average yield of dry tobacco per barn is 5.22 kg more. The curing area is the same for both harvesting and curing methods.

[0053] 2. Comparison of labor required from harvesting to removal from the kiln

[0054] As shown in Table 2, in terms of labor costs, each batch of single-harvest tobacco requires 1.5 fewer workers for harvesting and 1 fewer worker for transportation compared to conventional harvesting. The harvesting process alone requires 2.5 fewer workers, equivalent to 150 yuan less, while other labor costs remain the same. Table 2 below shows that the labor cost for conventional harvesting to produce 1 kg of dried tobacco is 0.36 yuan more than that for single-harvest tobacco.

[0055] Table 2 Comparison of Labor Costs from Harvesting to Removal from Harvest (Units: kg, pieces, yuan)

[0056]

[0057] 3. Cost of curing tobacco leaves

[0058] As shown in Table 3, the electricity consumption for each kang (heated brick bed) using the conventional roasting method is 0.3 kWh more, and the coal consumption is 0.3 kg more, while the roasting time is the same. Table 3 also shows that roasting 1 kg of dry tobacco using the conventional method consumes 0.01 yuan less energy than the conventional method.

[0059] Table 3. Costs of roasting and baking under different treatments

[0060]

[0061]

[0062] Note: Electricity costs 0.46 yuan per kilowatt-hour, and coal costs 0.6 yuan per kilogram.

[0063] 4. Comparison of upper- and middle-grade tobacco products, output value, and production volume.

[0064] As shown in Tables 4 and 5, the average price of tobacco leaves harvested and cured in the upper part of the leaf was 0.83 yuan higher than that of conventionally harvested tobacco, 10.39 percentage points higher for high-grade tobacco, 1.61 percentage points higher for orange-yellow tobacco, and 2.43 percentage points lower for mixed-color tobacco. The weight of a single leaf was 0.19g. This indicates that harvesting and curing the upper leaves in one go can increase the average price of tobacco leaves, the proportion of high-grade and medium-grade tobacco, and the proportion of orange-yellow tobacco, and can effectively control the proportion of mixed-color tobacco.

[0065] Table 4. Comparison of average prices of upper tobacco leaves, upper-middle grade tobacco, orange-yellow tobacco, and mixed-color tobacco under different harvesting methods.

[0066]

[0067] Table 5 Comparison of Single Leaf Weight of Tobacco Leaves After Curing with Different Harvesting and Curing Methods

[0068] deal with Total weight (g) Number of leaves (blades) Average single leaf weight (g) Process 1 1106.2 100 11.06 Process 2 1096.7 100 10.97 Process 3 1103.5 100 11.04 Process 4 1083.4 100 10.83

[0069] 5. Comparison of economic benefits

[0070] As shown in Table 6, the comprehensive benefit of one-time harvesting and curing of each kilogram of dry tobacco is 31.71 yuan, which is 1.20 yuan higher than the conventional method.

[0071] Table 6 Comparison of Labor, Energy Consumption, and Economic Benefits in Each Stage

[0072]

[0073]

[0074] 6. Comparison of chemical composition

[0075] Table 7 Comparison of Chemical Composition of Tobacco Leaves from Different Harvesting and Curing Methods

[0076]

[0077] As shown in Table 7, the chemical composition of flue-cured tobacco leaves harvested in one go (4-6 leaves) is more coordinated than that of conventionally harvested tobacco leaves. The nicotine content is 3.53%, which is 0.26 percentage points lower than that of conventionally harvested tobacco leaves, effectively improving the industrial usability of the upper tobacco leaves.

[0078] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation, characterized in that, include: S1. Tobacco Leaf Harvesting When the maturity of the upper leaves meets the requirements of the processing technology, 4-6 upper leaves should be harvested at once. S2, woven pipe tobacco Tie the poles according to the same variety and the same part of the plant. The same leaves should be on the same pole when they are ripe and of the same length. Do not tie poles to severely diseased or damaged leaves. S3, Baking and Seasoning Baking and preparation are carried out according to the following steps: S31. Maintain a steady low flame, simultaneously raising the dry bulb temperature to 32±1℃, then raising it to 36℃ at a rate of 1℃ / h, with a dry-wet difference of 1-2℃. Run the fan at 720r / min until the blade tips begin to turn yellow and soften, and the blades become warm to the touch. S32. Raise the dry bulb temperature to 38℃ at a rate of 1℃ / h, with a dry-wet difference of 2℃, and run the fan at 720r / min until the leaves in the high-temperature layer are 70-80% yellow, soften, and begin to wilt; raise the temperature to 40℃ at a rate of 1℃ / 2h, with a wet bulb temperature of 36℃, and run the fan at 1440r / min until the leaves in the high-temperature layer are 80-90% yellow, soften, and collapse, with a water loss of 20%; S33. Raise the dry bulb temperature to 42℃ at 1℃ / 2h, the wet bulb temperature to 36℃, and run the fan at 1440r / min. Stabilize the temperature until the veins of the tobacco leaves in the high-temperature layer turn white, the tobacco leaves fully collapse and the main ribs soften, and the tobacco leaves in the low-temperature layer turn 80-90% yellow and the leaves soften. S34. Start with a high flame, raising the dry bulb temperature to 44℃ at a rate of 1℃ / 2-3h, with a wet bulb temperature of 37℃, and run at 1440r / min. Stabilize the temperature until the small veins of the tobacco leaves in the mid-temperature layer turn completely white and the tips curl. Extend the stabilization period for 10 hours, raising the temperature to 48℃ at a rate of 1℃ / 2-3h, with a wet bulb temperature of 37-38℃. Stabilize the temperature and remove moisture until the main veins of the tobacco leaves turn white and the leaves lose 50% of their water content. S35. Increase the dry bulb temperature to 54℃ in 1℃ / 2-3h, and the wet bulb temperature to 38-39℃. During the temperature stabilization stage, adjust the fan to 720r / min. Stabilize the temperature and remove moisture until the whole dry sheet roll is dry. Stabilize the temperature for 8 hours to promote softening and aroma, and reduce the color difference between the front and back of the leaf. S36. Increase the temperature to 60℃ at a rate of 1℃ / h, maintain the wet-bulb temperature at 39-40℃, and keep the temperature stable for 10 hours until the main stem of the tobacco leaf is half dry. Then increase the temperature to 65-68℃ at a rate of 1℃ / h, with a maximum of 70℃. Use a fan at 720r / min and control the wet-bulb temperature at 41℃ and keep it stable. Maintain stable temperature and humidity until all the tobacco leaves are dry.

2. The curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation according to claim 1, characterized in that, The criteria for the upper leaves to reach maturity are as follows: the main vein of the upper tobacco leaf turns white and shiny, the yellow veins on the leaf surface are bright white, the basic color is greenish-yellow, mainly yellow, the leaf surface is fully yellowed, wrinkled, with obvious maturity spots, with withered tips and scorched edges, the leaf auricles turn yellow, the leaf surface hairs fall off and become shiny, the main vein is completely white, more than 2 / 3 of the branch veins turn white and shiny, the stem-leaf angle increases significantly, the leaf tip droops, the leaf edge is curved and wrinkled, the sound is crisp when harvested, the cross-section is neat, without stem bark, and the leaf age is 70 to 90 days.

3. The curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation according to claim 1, characterized in that, 20-25 days after topping, the main vein of the tobacco leaves turns white and shiny, and the leaf surface turns yellowish-green. 4-6 leaves are harvested at a time.

4. The curing process for harvesting 4-6 upper leaves of flue-cured tobacco in a single operation according to claim 1, characterized in that, When weaving the tobacco poles, each pole has 60 loops, with 2-3 pieces per loop. After weaving the standard tobacco poles, only 5-8cm of length remains at both ends of the pole.

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