A method for moisture stepwise reduction treatment in the curing and withering period of flue-cured tobacco

Abstract

The application discloses a kind of tobacco baking withering period moisture stepwise dehumidification processing method, comprising: S1, determines the moisture treatment dry ball temperature control point in tobacco baking withering period in tobacco barn;S2, initial wet ball temperature corresponding to moisture treatment dry ball temperature control point is divided according to stepwise dehumidification, initial wet ball temperature is 38~40 DEG C, which is 0.3~1 DEG C gradually reduced every 1.5h~3h, finally reduced to 35~36 DEG C;S3, according to S1 and S2 dry ball temperature and wet ball temperature setting "stepwise dehumidification curve" on baking control instrument;S4, run "stepwise dehumidification curve", tobacco is baked to full hearth tobacco soft, two layer tobacco hook tip to curl edge target state;S5, exit "stepwise dehumidification curve", and tobacco withering period moisture treatment ends.The present application is processed by interpolation "stepwise dehumidification curve" after tobacco baking withering period tobacco moisture, and the effect is better, and effectual control is baked black tobacco leaf production that tobacco moisture treatment is more in place.

Description

Technical Field

[0001] This invention relates to a method for stepwise dehumidification of moisture during the curing and withering period of flue-cured tobacco, belonging to the field of tobacco curing technology. Background Technology

[0002] Tobacco curing is essentially a process and result of drying tobacco leaves in a curing barn, removing moisture, and undergoing changes in the chemical composition of the leaves. A key challenge is ensuring that the changes during the drying process meet the required quality standards, namely, a yellow to orange-red appearance and harmonious internal chemical composition. Moisture control is crucial during the curing process.

[0003] Current curing theories and practices indicate that temperature and humidity within the curing barn directly and decisively influence the rate and direction of biochemical reactions within the leaf tissue cells during tobacco curing, making it one of the most important influencing factors in the curing environment. Within a temperature range of 45–46℃, when relative humidity exceeds 60%, if the moisture loss of tobacco leaves is less than 50%, browning will occur. However, even with fresh tobacco leaves with high moisture content, within the aforementioned temperature range, if the relative humidity is below 60%, and the moisture loss at the end of the yellowing stage exceeds 50%, browning is less likely to occur. Practice has shown that after tobacco leaves enter the color-fixing stage, when the dry-bulb temperature rises to 45℃, if the relative humidity within the curing barn exceeds 80%–100%, browning is easily induced in a very short time (half an hour), leading to blackening or even rottenness. Therefore, effectively managing the moisture content of tobacco leaves within the curing barn before the color-fixing stage is a crucial foundation for successful color fixing.

[0004] In existing curing processes, such as the three-stage curing process and others, the moisture treatment in the curing barn during the withering period is handled using a "cliff-jump" method (i.e., the wet-bulb temperature drops sharply from the initial setting of 38°C to 36°C in a very short time) or a natural treatment method (i.e., the wet-bulb temperature and dry-bulb temperature in the curing barn rise or fall simultaneously). The applicant has found in actual curing that the existing methods of moisture treatment during the withering period have the following problems: the tobacco leaves are difficult to color-fix, leading to blackening and rot; the appearance defects of the cured tobacco leaves are manifested as stiff leaves and ash residue, resulting in high losses in the quantity of cured tobacco leaves and poor curing quality.

[0005] Through observation and comparative research using curing experiments, the applicant discovered that when curing operators employ either a "cliff-like" or natural method to remove moisture from tobacco leaves during the withering period, it is difficult to achieve the expected 50% moisture loss. This leads to difficulties in color setting during the color-fixing period, resulting in poor tobacco curing quality (blackening, rottenness, stiffness, browning, etc.). The "cliff-like" method, by rapidly removing moisture from tobacco leaves in a short time, causes the leaves to harden and form stiff leaves after curing, failing to meet the cigarette industry's requirement for soft leaves. Furthermore, the bound water in the leaves is difficult to evaporate due to closed stomata, resulting in a moisture loss below the 50% target. This water is then released in large quantities after 45°C during the color-fixing period, leading to excessive relative humidity (above 60%) in the curing barn. This easily causes a browning reaction in the tobacco leaves, resulting in blackening or browning. In the natural dehumidification method, the wet-bulb temperature increases as the dry-bulb temperature rises. In the late yellowing stage and early color-fixing stage, the water loss of tobacco leaves is far below the target value of 50%, and the tobacco leaves are in a state of water-filled expansion. As the dry-bulb temperature rises, even when the water loss of tobacco leaves is less than 50% during the color-fixing stage, a large amount of water is discharged from the tobacco leaves, causing the relative humidity in the curing barn to be too high (greater than 70%). This easily leads to the browning reaction of tobacco leaves, resulting in the tobacco leaves being blackened and rotten. Summary of the Invention

[0006] Based on the above, the present invention provides a method for step-by-step dehumidification of tobacco during the curing and withering period, in order to overcome the shortcomings of the prior art.

[0007] The technical solution of this invention is: a method for stepwise dehumidification of tobacco moisture during the curing and withering period, comprising:

[0008] S1. Determine the dry ball temperature control point for moisture treatment in the curing barn during the tobacco curing and withering period, wherein the dry ball temperature control point is 38℃~40℃.

[0009] S2. The initial wet-bulb temperature corresponding to the dry-bulb temperature control point of the moisture treatment is divided according to the step-by-step dehumidification. The initial wet-bulb temperature is 38℃~40℃, which is gradually reduced by 0.3℃~1℃ every 1.5h~3h of operation, and finally reduced to 35℃~36℃.

[0010] S3. Set the "step dehumidification curve" on the baking controller according to S1 and S2 for dry bulb temperature and wet bulb temperature;

[0011] S4. Run the "step-by-step dehumidification curve" until the tobacco leaves are fully softened and the tips of the second layer of tobacco leaves are hooked and curled. If the tobacco leaves do not reach the target state, repeat the "step-by-step dehumidification curve" until the tobacco leaves reach the target state.

[0012] S5. Exit the "step-by-step dehumidification curve" and the water treatment during the tobacco wilting period ends.

[0013] As a further improvement of the present invention, when the initial wet-bulb temperature is 38°C, the dehumidification rate is 0.5°C / h, divided into stages of 38°C, 37.5°C, 37°C, 36.5°C, 36°C, and 35.5°C, with each stage running for 2 hours.

[0014] As a further improvement of the present invention, when the initial wet-bulb temperature is 39°C, the dehumidification rate is 0.5°C / h, divided into stages of 39°C, 38.5°C, 38°C, 37.5°C, 37°C, 36.5°C, 36°C, and 35.5°C, with each stage running for 2 hours.

[0015] As a further improvement of the present invention, when the initial wet-bulb temperature is 40°C, the temperature is divided into four stages: 40°C, 39.5°C, 39°C, 38.5°C, 38°C, 37.5°C, 37°C, 36.5°C, 36°C, and 35.5°C. The dehumidification rate is 0.5°C / h, and each stage runs for 2 hours.

[0016] As a further improvement of the present invention, in rainy weather and when the relative humidity in the curing barn is higher than 94%, the running time of each wet bulb temperature segment is adjusted to 3 hours, and the target state of the tobacco leaves is adjusted to soften the tobacco leaves throughout the curing process and form small rolled leaves.

[0017] The beneficial effects of this invention are as follows: This invention treats the moisture content of tobacco leaves during the withering period of flue-cured tobacco by interpolating a "step dehumidification curve" before curing, resulting in more effective and thorough moisture treatment of the tobacco leaves; it lays a good foundation for good moisture content during the color-fixing period of tobacco leaves, effectively controls the production of rotten and blackened tobacco leaves (weight of non-graded tobacco leaves in Tables 1-3); and significantly improves the quality of tobacco leaves after curing. Detailed Implementation

[0018] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, a detailed description is provided below in conjunction with specific embodiments of the present invention. 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.

[0019] The experiment was conducted from 2016 to 2023 in Longli County, Huishui County, Pingtang County, Luodian County, Changshun County, Guiding County, and Fuquan City of Qiannan Buyi and Miao Autonomous Prefecture, Guizhou Province. The tested flue-cured tobacco varieties were Yunyan 87, Yunyan 85, and K326. Middle and upper leaves were used as experimental materials. The tested tobacco leaves were cultivated and managed according to local high-quality tobacco production standards, and harvested at maturity according to the standards. The tested curing barns were conventional airflow rising or falling dense curing barns. A comparative experiment was conducted using the local conventional three-stage curing process as a control, and interpolating the proposed step-down dehumidification treatment of this invention into the conventional three-stage curing process or the medium-temperature, moisturizing, yellowing dense curing process for middle and upper leaves as a comparative treatment. Except for the process conditions, all other factors, such as curing barn structure, tobacco variety, quantity, and packing density, were the same.

[0020] Example 1 (Interpolation of "stepped dehumidification curve" for conventional three-stage baking process)

[0021] Tested variety: Yunyan 87, upper leaves, 2018, Pingyan, Luodian County

[0022] Curing process: The curing process follows the conventional three-stage curing process for flue-cured tobacco varieties (GB / T 23219—2008). Moisture treatment is carried out according to the "step-down dehumidification curve," and the curing operation is conducted locally. The specific process is as follows:

[0023] Yellowing stage: After loading the tobacco, raise the temperature of the curing barn to 35℃ with a low fire, and maintain the wet bulb temperature at 34℃. After the leaf tips turn yellow, raise the dry bulb temperature to 38℃ at a rate of 1℃ every 2 hours, and extend the temperature stabilization time, controlling the wet bulb temperature at 36℃. This will ensure that about 80% of the tobacco leaves in the curing barn, measured by the thermometer, reach 70% to 80% yellow. After raising the wet bulb temperature to 38℃, switch to a medium fire and maintain the dry bulb temperature at 38℃. Set the curing temperature according to the "step dehumidification curve" (divided into wet bulb temperatures of 38℃, 37.5℃, 37℃, 36.5℃, 36℃, and 35.5℃, with a dehumidification rate of 0.5℃ / h, and each stage running for 2 hours) until the tobacco leaves are in the following state: the entire layer of tobacco leaves softens, and the tips of the second layer of tobacco leaves curl. Afterwards, the baking control device was reset, starting with a dry bulb temperature of 38℃ and a wet bulb temperature of 35.5℃, then the temperature was increased to 42℃, while maintaining a wet bulb temperature of 37℃ for an extended period of time, so that the tobacco leaves could achieve full-curling and edge-rolling of the leaves.

[0024] Color fixation period: The dry-bulb temperature is first increased at an average rate of 1°C every 3 hours to 46°C and then kept stable for an extended period, causing the tobacco leaves to turn yellow and lose moisture to reach the small rolling stage. Then, the temperature is increased at a rate of 1°C every 2 hours to 54°C and kept stable for 10 hours to achieve leaf dryness. As the dry-bulb temperature rises, the wet-bulb temperature gradually rises and stabilizes at 39°C.

[0025] Drying stage: Increase the temperature from 54℃ to 68℃ at a rate of 1℃ per hour and maintain it until the tobacco leaves are completely dry. Maintain a wet-bulb temperature of 40℃ until the dry-bulb temperature reaches 60℃; after reaching 60℃, gradually close the inlet and outlet vents, reduce ventilation, and maintain a wet-bulb temperature of 40℃.

[0026] Compare with Example 1 (conventional three-stage baking process)

[0027] Tested variety: Yunyan 87, upper leaves, 2018, Pingyan, Luodian County

[0028] Curing process: The curing operation will be carried out locally according to the conventional three-stage curing process for flue-cured tobacco varieties (GB / T 23219—2008). The specific process is as follows:

[0029] Yellowing stage: After loading the tobacco, raise the temperature of the curing barn to 35℃ with a low flame, maintaining a wet-bulb temperature of 34℃. Once the leaf tips turn yellow, increase the dry-bulb temperature to 38℃ at a rate of 1℃ every 2 hours, and maintain this temperature for an extended period, controlling the wet-bulb temperature at 36℃. This will ensure that about 80% of the tobacco leaves in the curing barn, measured by the thermometer, reach 70% to 80% yellowing, while simultaneously softening the leaves (with a water loss of about 30%). Then, raise the temperature to 42℃, maintaining a wet-bulb temperature of 37℃ for an extended period, until the tobacco leaves are yellow with slightly green veins, wilting and collapsing, and the midrib softens.

[0030] Color fixation period: The dry-bulb temperature is first increased at an average rate of 1°C every 3 hours to 46°C and then kept stable for an extended period, causing the tobacco leaves to turn yellow and lose moisture to reach the small rolling stage. Then, the temperature is increased at a rate of 1°C every 2 hours to 54°C and kept stable for 10 hours to achieve leaf dryness. As the dry-bulb temperature rises, the wet-bulb temperature gradually rises and stabilizes at 39°C.

[0031] Drying stage: Increase the temperature from 54℃ to 68℃ at a rate of 1℃ per hour and maintain it until the tobacco leaves are completely dry. Maintain a wet-bulb temperature of 40℃ until the dry-bulb temperature reaches 60℃; after reaching 60℃, gradually close the inlet and outlet vents, reduce ventilation, and maintain a wet-bulb temperature of 40℃.

[0032] For the tobacco leaves after curing in Example 1 and Control Example 1, 30 tobacco stalks were taken from the same location in the curing barn, and the dry weight of the tobacco leaves was measured. The weight of the yellow tobacco was sorted out, and the sales amount, average price of the sample tobacco, and average price of the yellow tobacco were calculated. The results are shown in Table 1.

[0033]

[0034] As shown in Table 1, by interpolating the "stepped dehumidification curve" in the conventional baking process, every 30 tobacco sticks can effectively reduce the weight of non-grade tobacco leaves (i.e., black tobacco, rotten tobacco, tung bark tobacco, mixed color tobacco, gray tobacco, green tobacco, etc.) by about 15 kg, increase the weight of yellow tobacco by about 21 kg, significantly increase the proportion of high-grade yellow tobacco by 214.8%, and increase the sales amount of tobacco by about 710 yuan.

[0035] Example 2 (Interpolation of "stepped dehumidification curve" for the intensive curing process of medium-temperature moisturizing and yellowing of tobacco leaves in the upper and middle parts)

[0036] Tested variety: Yunyan 87, middle leaf, 2019, Pingyan, Luodian County.

[0037] Curing process: The process follows the conventional medium-temperature, moisturizing, intensive curing process for the upper and middle parts of the tobacco leaves, with moisture treatment using a "stepped dehumidification curve." The specific process is as follows:

[0038] Yellowing stage:

[0039] Ignition and preheating point: After ignition, raise the dry bulb temperature to 33℃ in 2-3 hours, with temperature and humidity synchronized, and maintain a stable temperature for 8 hours to preheat all tobacco leaves in the kiln. Observe the glass of the observation window for fogging and the tips of the leaves for yellowing.

[0040] Optimal yellowing point: Raise the dry and wet bulb temperature in the curing room to 38℃ (middle leaves) at 1℃ / 2h, run the curing controller, start and stop the circulating fan on a timer (start and run for 10 minutes every hour), maintain the temperature for 36h, and cure the tobacco leaves until the leaves turn yellow with green veins (80% yellow).

[0041] Yellowing and softening transition point: Raise the dry-bulb temperature in the curing barn to 40℃ at a rate of 1℃ / 2h. Set the wet-bulb temperatures as a "stepped dehumidification curve" at 40℃, 39.5℃, 39℃, 38.5℃, 38℃, 37.5℃, 37℃, 36.5℃, 36℃, and 35.5℃, with a dehumidification rate of 0.5℃ / h, and run each stage for 2 hours. Run the "stepped dehumidification curve" until all the tobacco leaves in the curing barn soften and the tips of the second layer of tobacco leaves curl.

[0042] Yellowing and softening of veins: Raise the dry bulb temperature to 42℃ at 1℃ / 2h, the wet bulb temperature to 36.5℃, maintain the temperature for 20h, and bake until the tobacco leaves are 90% yellow, the main veins soften, the leaves collapse, and the high-temperature layer forms small curls.

[0043] Color fixation period:

[0044] Half-dried point: Raise the dry bulb temperature to 45℃ at 1℃ / 2h, keep the wet bulb temperature at 37℃ for 24h, and bake until the leaves turn yellow with white veins and break the green, and the leaves in the middle temperature layer curl up and become half-dried.

[0045] Dry bulb blending point: Raise the dry bulb temperature to 52℃ at 1℃ / 2h, maintain the wet bulb temperature at 38℃ for 20h. The leaves turn yellow with yellow veins, and the leaves are rolled into large rolls and dried in a fully kiln-dried state to promote the synthesis of aroma substances.

[0046] Drying stage:

[0047] Vein contraction and color adjustment point: Raise the dry bulb temperature to 58℃ at a rate of 1℃ / h, keep the wet bulb temperature at 39℃ and maintain the temperature for 10 hours to promote the contraction of the main vein and adjust the color difference between the front and back of the tobacco leaf.

[0048] Purple Pure Fragrance Point: The dry bulb temperature is raised to 62℃ at a rate of 1℃ / h, and the wet bulb temperature is kept constant at 40℃ for 12 hours to promote the semi-drying of the main vein and the beginning of its purple coloration, thus purifying the aroma substances.

[0049] Dry-bulb preservation point: Raise the dry-bulb temperature to 68℃ and the wet-bulb temperature to 40℃ at a rate of 1℃ / h, and maintain this temperature for 12 hours. Then, lower the dry-bulb temperature to 65℃ and the wet-bulb temperature to 40℃, and maintain this temperature for 12 hours until the main veins of the tobacco leaves are completely dry and the entire batch has purple veins, thus preserving the aroma to the maximum extent. The dry-bulb temperature should not exceed 68℃ and the wet-bulb temperature should not exceed 41℃ to prevent the leaves from turning red.

[0050] Compare with Example 2 (medium-temperature moisturizing and intensive baking process for middle and upper tobacco leaves to turn yellow).

[0051] Tested variety: Yunyan 87, middle leaf, 2019, Pingyan, Luodian County.

[0052] Curing process: The curing operation is carried out locally using the conventional medium-temperature, moisturizing, and intensive curing process for the upper and middle parts of tobacco leaves, which causes them to turn yellow. The specific process is as follows:

[0053] Yellowing stage:

[0054] Ignition and preheating point: After ignition, raise the dry bulb temperature to 33℃ in 2-3 hours, with temperature and humidity synchronized, and maintain a stable temperature for 8 hours to preheat all tobacco leaves in the kiln. Observe the glass of the observation window for fogging and the tips of the leaves for yellowing.

[0055] Optimal yellowing point: Raise the dry and wet bulb temperature in the curing room to 38℃ (middle leaves) at 1℃ / 2h, run the curing controller, start and stop the circulating fan on a timer (start and run for 10 minutes every hour), maintain the temperature for 36h, and cure the tobacco leaves until the leaves turn yellow with green veins (80% yellow).

[0056] Yellowing and softening transition point: Raise the dry bulb temperature in the curing barn to 40℃ at a rate of 1℃ / 2h, then lower the wet bulb temperature to 36℃ at a rate of 1℃ / 2h, stabilize the temperature for 8h, and cure until the tobacco leaves are 90% yellow, soft, and have yellow leaves with green veins.

[0057] Yellowing and softening of veins: Raise the dry bulb temperature to 42℃ at 1℃ / 2h and the wet bulb temperature to 36.5℃, maintain the temperature for 20h, and bake until the tobacco leaves are 90% yellow, the main veins soften, the leaves collapse, and the tips and edges curl in the high-temperature layer.

[0058] Color fixation period:

[0059] Half-dried point: Raise the dry bulb temperature to 45℃ at 1℃ / 2h, keep the wet bulb temperature at 37℃ for 24h, and bake until the leaves turn yellow with white veins and break the green, and the leaves in the middle temperature layer curl up and become half-dried.

[0060] Dry bulb blending point: Raise the dry bulb temperature to 52℃ at 1℃ / 2h, maintain the wet bulb temperature at 38℃ for 20h. The leaves turn yellow with yellow veins, and the leaves are rolled into large rolls and dried in a fully kiln-dried state to promote the synthesis of aroma substances.

[0061] Drying stage:

[0062] Vein contraction and color adjustment point: Raise the dry bulb temperature to 58℃ at a rate of 1℃ / h, keep the wet bulb temperature at 39℃ and maintain the temperature for 10 hours to promote the contraction of the main vein and adjust the color difference between the front and back of the tobacco leaf.

[0063] Purple Pure Fragrance Point: The dry bulb temperature is raised to 62℃ at a rate of 1℃ / h, and the wet bulb temperature is kept constant at 40℃ for 12 hours to promote the semi-drying of the main vein and the beginning of its purple coloration, thus purifying the aroma substances.

[0064] Dry-bulb preservation point: Raise the dry-bulb temperature to 68℃ and the wet-bulb temperature to 40℃ at a rate of 1℃ / h, and maintain this temperature for 12 hours. Then, lower the dry-bulb temperature to 65℃ and the wet-bulb temperature to 40℃, and maintain this temperature for 12 hours until the main veins of the tobacco leaves are completely dry and the entire batch has purple veins, thus preserving the aroma to the maximum extent. The dry-bulb temperature should not exceed 68℃ and the wet-bulb temperature should not exceed 41℃ to prevent the leaves from turning red.

[0065] For the tobacco leaves after curing in Example 2 and Control Example 2, 30 tobacco stalks were taken from the same location in the curing barn, and the dry weight of the tobacco leaves was measured. The weight of the yellow tobacco was sorted out, and the sales amount, average price of the sample tobacco, and average price of the yellow tobacco were calculated. The results are shown in Table 2.

[0066]

[0067] As shown in Table 2, by interpolating the "stepped dehumidification curve" in the intensive yellowing and curing process of the middle and upper tobacco leaves at medium temperature and humidity, every 30 tobacco sticks can effectively reduce the weight of non-graded tobacco leaves (i.e., blackened, rotten, tung bark, mixed color, gray leaf tobacco, green tobacco, etc.) by about 2 kg, increase the weight of yellow tobacco by about 5 kg, improve the grade of yellow tobacco, and increase the sales amount of tobacco by about 192 yuan.

[0068] Example 3 (Interpolation of "stepped dehumidification curve" for the intensive curing process of medium-temperature moisturizing and yellowing of tobacco leaves in the upper and middle parts)

[0069] Tested variety: K326, upper leaves, 2020, Longlibai Province.

[0070] Curing process: The process follows the conventional medium-temperature, moisturizing, intensive curing process for the upper and middle parts of the tobacco leaves, with moisture treatment using a "stepped dehumidification curve." The specific process is as follows:

[0071] Yellowing stage:

[0072] Ignition and preheating point: After ignition, raise the dry bulb temperature to 33℃ in 2-3 hours, with temperature and humidity synchronized, and maintain a stable temperature for 8 hours to preheat all tobacco leaves in the kiln. Observe the glass of the observation window for fogging and the tips of the leaves for yellowing.

[0073] Optimal yellowing point: Raise the dry and wet bulb temperature in the curing room to 39℃ (upper leaves) at 1℃ / 2h, run the curing controller, start and stop the circulating fan on a timer (start and run for 10 minutes every hour), maintain the temperature for 48h, and cure the tobacco leaves until they turn yellow with green veins (90% yellow).

[0074] Yellowing and softening transition point: Raise the dry bulb temperature in the curing barn to 40℃ at a rate of 1℃ / 2h. Set the wet bulb temperatures as a "stepped dehumidification curve" at 40℃, 39.5℃, 39℃, 38.5℃, 38℃, 37.5℃, 37℃, 36.5℃, 36℃, and 35.5℃, with a dehumidification rate of 0.5℃ / h, and run each stage for 3 hours. Run the "stepped dehumidification curve" until all the tobacco leaves in the curing barn soften and the tips of the second layer of tobacco leaves curl.

[0075] Yellowing and softening of veins: Raise the dry bulb temperature to 42℃ at 1℃ / 3h, the wet bulb temperature to 36.5℃, maintain the temperature for 24h, and bake until the tobacco leaves are 90% yellow, the main veins soften, the leaves collapse, and the high-temperature layer forms small curls.

[0076] Color fixation period:

[0077] Half-dried point: Raise the dry bulb temperature to 46℃ at 1℃ / 3h, keep the wet bulb temperature at 37℃ for 26h, and bake until the leaves turn yellow with white veins and break the green, and the leaves in the middle temperature layer curl up and become half-dried.

[0078] Dry bulb blending point: Raise the dry bulb temperature to 52℃ at 1℃ / 3h, maintain the wet bulb temperature at 38℃ for 24h. The leaves turn yellow with yellow veins, and the leaves are rolled into large rolls and dried in a fully kiln-dried state to promote the synthesis of aroma substances.

[0079] Drying stage:

[0080] Vein contraction and color adjustment point: Raise the dry bulb temperature to 58℃ at a rate of 1℃ / h, keep the wet bulb temperature at 39℃ and maintain the temperature for 10 hours to promote the contraction of the main vein and adjust the color difference between the front and back of the tobacco leaf.

[0081] Purple Pure Fragrance Point: The dry bulb temperature is raised to 62℃ at a rate of 1℃ / h, and the wet bulb temperature is kept constant at 40℃ for 12 hours to promote the semi-drying of the main vein and the beginning of its purple coloration, thus purifying the aroma substances.

[0082] Dry-bulb preservation point: Raise the dry-bulb temperature to 68℃ and the wet-bulb temperature to 40℃ at a rate of 1℃ / h, and maintain this temperature for 12 hours. Then, lower the dry-bulb temperature to 65℃ and the wet-bulb temperature to 40℃, and maintain this temperature for 12 hours until the main veins of the tobacco leaves are completely dry and the entire batch has purple veins, thus preserving the aroma to the maximum extent. The dry-bulb temperature should not exceed 68℃ and the wet-bulb temperature should not exceed 41℃ to prevent the leaves from turning red.

[0083] Compare with Example 3 (medium-temperature moisturizing and intensive baking process for middle and upper tobacco leaves to turn yellow).

[0084] Tested variety: K326, upper leaves, 2020, Longlibai Province.

[0085] Curing process: The curing operation is carried out locally using the conventional medium-temperature, moisturizing, and intensive curing process for the upper and middle parts of tobacco leaves, which causes them to turn yellow. Specific processes are as follows:

[0086] Yellowing stage:

[0087] Ignition and preheating point: After ignition, raise the dry bulb temperature to 33℃ in 2-3 hours, with temperature and humidity synchronized, and maintain a stable temperature for 8 hours to preheat all tobacco leaves in the kiln. Observe the glass of the observation window for fogging and the tips of the leaves for yellowing.

[0088] Optimal yellowing point: Raise the dry and wet bulb temperature in the curing room to 39℃ (upper leaves) at 1℃ / 2h, run the curing controller, start and stop the circulating fan on a timer (start and run for 10 minutes every hour), maintain the temperature for 48h, and cure the tobacco leaves until they turn yellow with green veins (90% yellow).

[0089] Yellowing and softening transition point: Raise the dry bulb temperature in the curing barn to 40℃ at a rate of 1℃ / 2h, and then lower the wet bulb temperature to 36℃ at a rate of 1℃ / 2h. Maintain the temperature for 10h and cure until the tobacco leaves are 90% yellow, soft, and have yellow leaves with green veins.

[0090] Yellowing and softening of veins: Raise the dry bulb temperature to 42℃ at 1℃ / 3h and the wet bulb temperature to 36.5℃, maintain the temperature for 24h, and bake until the tobacco leaves are 100% yellow, the main veins soften, the leaves collapse, and the tips and edges curl in the high-temperature layer.

[0091] Color fixation period:

[0092] Half-dried point: Raise the dry bulb temperature to 46℃ at 1℃ / 3h, keep the wet bulb temperature at 37℃ for 26h, and bake until the leaves turn yellow with white veins and break the green, and the leaves in the middle temperature layer curl up and become half-dried.

[0093] Dry bulb blending point: Raise the dry bulb temperature to 52℃ at 1℃ / 3h, maintain the wet bulb temperature at 38℃ for 24h. The leaves turn yellow with yellow veins, and the leaves are rolled into large rolls and dried in a fully kiln-dried state to promote the synthesis of aroma substances.

[0094] Drying stage:

[0095] Vein contraction and color adjustment point: Raise the dry bulb temperature to 58℃ at a rate of 1℃ / h, keep the wet bulb temperature at 39℃ and maintain the temperature for 10 hours to promote the contraction of the main vein and adjust the color difference between the front and back of the tobacco leaf.

[0096] Purple Pure Fragrance Point: The dry bulb temperature is raised to 62℃ at a rate of 1℃ / h, and the wet bulb temperature is kept constant at 40℃ for 12 hours to promote the semi-drying of the main vein and the beginning of its purple coloration, thus purifying the aroma substances.

[0097] Dry-bulb preservation point: Raise the dry-bulb temperature to 68℃ and the wet-bulb temperature to 40℃ at a rate of 1℃ / h, and maintain this temperature for 12 hours. Then, lower the dry-bulb temperature to 65℃ and the wet-bulb temperature to 40℃, and maintain this temperature for 12 hours until the main veins of the tobacco leaves are completely dry and the entire batch has purple veins, thus preserving the aroma to the maximum extent. The dry-bulb temperature should not exceed 68℃ and the wet-bulb temperature should not exceed 41℃ to prevent the leaves from turning red.

[0098] For the tobacco leaves after curing in Example 3 and Control Example 3, 30 tobacco stalks were taken from the same location in the curing barn, and the dry weight of the tobacco leaves was measured. The weight of the yellow tobacco was sorted out, and the sales amount, average price of the sample tobacco, and average price of the yellow tobacco were calculated. The results are shown in Table 3.

[0099]

[0100] As shown in Table 3, by interpolating the "stepped dehumidification curve" in the intensive curing process of medium-temperature moisturizing and yellowing of tobacco leaves in the middle and upper parts, the weight of non-graded tobacco leaves (i.e., blackened, rotten, tung bark, mixed color, gray leaf tobacco, green tobacco, etc.) can be effectively reduced by about 8.5 kg per 30 tobacco sticks, while the weight of yellow tobacco increases by about 14.5 kg. The proportion of high-grade yellow tobacco increases significantly by 54.9%, and the sales amount increases by about 407 yuan.

[0101] 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 method for stepwise moisture reduction treatment during the curing and withering period of flue-cured tobacco, characterized in that, include: S1. Determine the dry ball temperature control point for moisture treatment in the curing barn during the tobacco curing and withering period, wherein the dry ball temperature control point is 38℃~40℃. S2. The initial wet-bulb temperature corresponding to the dry-bulb temperature control point of the moisture treatment is divided according to the stepped dehumidification method. When the initial wet-bulb temperature is 38℃, it is divided into stages of 38℃, 37.5℃, 37℃, 36.5℃, 36℃, and 35.5℃, with a dehumidification rate of 0.5℃ / h and each stage running for 2 hours. When the initial wet-bulb temperature is 39℃, it is divided into stages of 39℃, 38.5℃, 38℃, 37.5℃, 37℃, 36.5℃, 36℃, and 35.5℃, with a dehumidification rate of 0.5℃ / h and each stage running for 2 hours. When the initial wet-bulb temperature is 40℃, it is divided into stages of 40℃, 39.5℃, 39℃, 38.5℃, 38℃, 37.5℃, 37℃, 36.5℃, 36℃, and 35.5℃, with a dehumidification rate of 0.5℃ / h and each stage running for 2 hours. S3. Set the "stepped dehumidification curve" on the baking controller according to S1 and S2 for dry bulb temperature and wet bulb temperature; S4. Run the "step-by-step dehumidification curve" until the tobacco leaves are fully softened and the tips of the second layer of tobacco leaves are hooked and curled. If the tobacco leaves do not reach the target state, repeat the "step-by-step dehumidification curve" until the tobacco leaves reach the target state. S5. Exit the "step-by-step dehumidification curve". The water treatment during the tobacco wilting period is over.

2. The method for stepwise moisture reduction during the curing and withering period of flue-cured tobacco according to claim 1, characterized in that, In rainy weather and when the relative humidity in the curing barn is higher than 94%, the running time of each wet bulb temperature stage is adjusted to 3 hours, and the target state of the tobacco leaves is adjusted to soften the tobacco leaves throughout the curing process and form small rolled leaves.

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