Method for reducing hunger ash hanging of lower tobacco leaves

Abstract

The invention discloses a method for reducing hunger ash hanging of lower tobacco leaves, which comprises the following steps of: secondarily cleaning bottom leaves, cleaning 1-2 pieces of tobacco leaves in a second shed, squaring and topping, harvesting in physiological maturity, weaving rods in a classified manner, loading the tobacco leaves into a kang in a layered and reduced manner and the like, and baking by adopting a six-stage baking process. The method comprises a low-temperature preheating yellowing stage, an initial yellowing stage, a main yellowing and withering stage, a yellowing and drying coordination stage, a low-temperature medium-high-humidity color fixing stage and a rapid stem drying stage. The method can effectively improve the appearance quality of the lower flue-cured tobacco leaves, improve the grade structure and sensory quality of the lower flue-cured tobacco leaves, increase the weight of single leaves and remarkably reduce the proportion of ash-coated tobacco leaves.

Description

Technical Field

[0001] This invention relates to a method for reducing the starvation and ash accumulation of lower tobacco leaves, belonging to the field of tobacco cultivation and curing technology. Background Technology

[0002] Flue-cured tobacco is an important economic crop in my country, and the quality of its leaves directly affects the quality of the cigarette industry. Lower tobacco leaves typically refer to the first to eighth leaves from the bottom, mainly including the three bottom leaves and the fourth to fifth leaves from the second shed. Due to poor lighting conditions and intense nutrient competition, lower tobacco leaves generally suffer from thinner leaves and poor development. The quality of the three bottom leaves and the first to second leaves from the second shed (from bottom to top) is particularly low, resulting in lower curing value and usability. In actual production, the harvest maturity of lower tobacco leaves is often too high, with a large proportion being overripe. During curing, these leaves turn yellow quickly and to a high degree, easily leading to "starvation" due to excessive nutrient consumption, which in turn induces ash formation and enzymatic browning, severely restricting the usability and economic value of lower tobacco leaves.

[0003] Existing technologies mainly improve tobacco quality and grade structure by optimizing agronomic measures. Patent document (authorization announcement number CN104429446B) discloses a method for adjusting the grade structure of flue-cured tobacco. This involves removing 6-8 unsuitable fresh tobacco leaves from the bottom and lower parts of the plant when 50% of the first central flower has opened. Then, at the end of the harvest of the middle leaves, a second topping is performed, removing the top 3-4 leaves with distinct upper characteristics from each plant. After the second topping, the total number of effective leaves per plant reaches 14-17, achieving 100% upper-medium grade and 70% upper grade tobacco. Ouyang Lei (2013) found that removing 2 bottom leaves 7 days after topping resulted in the most balanced chemical composition. Li Dong et al. (2018) found that removing 4 bottom leaves at once during topping, leaving 18 leaves, yielded the best results, optimizing the grade structure and output value of Yuyan No. 6 tobacco. Li Chengjun et al. (2021) further confirmed that the treatment combinations of topping at 80% central flower opening + removing 4 bottom leaves one week before topping and topping at 80% central flower opening + removing 4 bottom leaves on the day of topping had a higher overall evaluation. Ma Yuan (2020) believed that the best leaf removal mode for the new flue-cured tobacco line CF8704 was to remove the bottom leaves during inter-cultivation and hilling, and then remove the bottom 2 leaves during topping. Liu Li and Ye Weimin (2016) pointed out that removing 2 bottom leaves during topping can increase the weight of a single leaf and has a good effect on improving the quality of tobacco leaves. Li Jun et al. (2014) believed that removing 2 bottom leaves during topping is the optimal treatment, with the highest proportion of high-grade tobacco, average price, yield, and output value. Zhang Liming et al. (2014) believed that removing bottom leaves during topping can better optimize the structure of tobacco leaves and achieve the goal of improving quality, stabilizing yield, and increasing value. Guo Fangjun et al. (2017) pointed out that topping when 30% to 50% of the central flowers are open and removing 4 bottom leaves on the same day is beneficial to improving the yield and quality of tobacco leaves. Patent document (publication number CN116548268A) discloses a method for preventing ash buildup on upper tobacco leaves and for harvesting and curing in high-altitude tobacco-growing areas. This method involves selecting low-temperature resistant flue-cured tobacco varieties suitable for the local ecological and climatic conditions, appropriately advancing the field transplanting time, removing bottom leaves and lower leaves with no curing value, determining the appropriate topping height, number of leaves and branches to be retained, appropriately advancing the harvest time, determining the appropriate harvest maturity, and the number and frequency of harvesting leaves. It also involves controlling the rate of temperature increase, slow curing at low temperatures, gradually increasing the temperature for preheating and initiating the yellowing of the tobacco leaves, and maintaining stable curing temperatures at six key dry-bulb temperatures: 38℃, 40℃, 42℃, 44℃, 48℃, and 53℃. At 38℃, a repeated steaming and dehumidification method is used to induce sweating, water loss, and yellowing of the tobacco leaves, effectively reducing ash buildup in the field and after curing, and improving the quality of the upper tobacco leaves after curing.

[0004] However, existing research has largely focused on optimizing the overall grade structure of lower tobacco leaves or addressing problems with upper leaves, failing to propose systematic solutions to the "starvation and ash-covering" phenomenon unique to lower leaves due to inherent deficiencies such as insufficient sunlight, thin leaves, and susceptibility to over-ripening. Particularly in the curing process, current technologies have failed to precisely control the curing process based on the lower leaves' poor curing resistance and tendency to excessive yellowing, which has become a major bottleneck in improving the quality of lower tobacco leaves. Summary of the Invention

[0005] Based on the above, the present invention provides a method for reducing the ash-laden residue on lower tobacco leaves. By integrating innovative agronomic operations and supporting curing processes, the method systematically solves the problem of ash-laden residue on lower tobacco leaves caused by poor field environment, easy over-ripening, yellowing during curing and uneven water loss, thereby improving the quality of lower tobacco leaves after curing.

[0006] The technical solution of this invention is: a method for reducing the starvation and ash accumulation of lower tobacco leaves, comprising: S1 Secondary Removal of Bottom Leaves: Remove 1-2 bottom leaves for the first time 35 days after transplanting in the field; remove 1-2 bottom leaves for the second time 45 days after transplanting; S2 Cleaning of the second-lowest tobacco leaves: 55 days after transplanting in the field, clean 1-2 leaves from the bottom second-lowest tobacco leaves; S3 Budding and Topping: Adopts the budding and topping method; S4 Physiological Maturity Harvesting: When more than 80% of the tobacco leaves in the lower two sheds of the tobacco field have reached physiological maturity, the lower tobacco leaves are harvested. S5 Classification and Bagging: According to the maturity characteristics of tobacco leaves, fresh tobacco leaves are divided into four categories: immature, physiologically mature, technologically mature, and over-mature. Tobacco leaves with no curing value are removed, and the leaves are classified and bundled into bamboo poles, with 100-120 leaves per pole. S6 Layered Loading: Following the principle of "same layer, same quality," fresh tobacco leaves with lower maturity are loaded into the low-temperature layer of the intensive curing barn, while those with higher maturity are loaded into the high-temperature layer. The loading amount is 270-300 sticks, a reduction of 9.09%-25.00% compared to the conventional loading amount of 330-360 sticks. S7 Baking: Baking is carried out according to a six-stage baking process, which includes low-temperature preheating and yellowing stage, initial yellowing stage, main yellowing and wilting stage, yellowing and drying coordination stage, low-temperature and medium-high humidity color fixing stage, and rapid drying stage.

[0007] The aforementioned method for reducing the starvation and ash accumulation of lower tobacco leaves is as follows: In step S3, the specific operation of budding and topping is as follows: On a sunny morning, when the flower bud extends beyond the top leaf, reaches a length of 3-5 cm, is still green, is clearly distinguishable from the young top leaf, and the petals wrapped by the calyx are visible, remove the flower bud, flower stalk, and 2-3 underdeveloped small leaves below it.

[0008] The aforementioned method for reducing the starvation and ash accumulation of lower tobacco leaves is as follows: In step S4, the criteria for determining physiologically mature tobacco leaves are: the basic color of the tobacco leaf surface is green and glossy, the leaf tip and base are light yellow, more than 1 / 2 of the main veins are faded to white, the pubescence is lost, the leaf surface is slightly wrinkled, the leaf tip and leaf edge droop slightly, the picking sound is crisp, the cross-section is neat, and there is no stem bark.

[0009] The aforementioned method for reducing the starvation and ash buildup in the lower tobacco leaves includes the following six-stage curing process: Phase 1: Low-temperature preheating and yellowing stage After ignition, the dry bulb temperature is raised to 30-33℃ and the wet bulb temperature is raised to 30-33℃ at a rate of 1℃ / h, and then the temperature is maintained for 3-4 hours. After that, the dry bulb temperature is raised to 35-36℃ and the wet bulb temperature is raised to 34.5-35.5℃ at a rate of 1℃ / h, and then the temperature is maintained for 4-6 hours to preheat the tobacco leaves and make them turn yellow by 10-20%. Phase Two: Initial Yellowing Stage Raise the dry bulb temperature to 37-38℃ and the wet bulb temperature to 36-37℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 15-20 hours until the tobacco leaves turn 30-40% yellow and 1 / 3 of the leaves soften. Third stage: Main yellowing and withering stage Increase the dry-bulb temperature to 39-41℃ and the wet-bulb temperature to 35℃ at a rate of 1℃ / 4h, and bake at a stable temperature for 6-10h until the tobacco leaves turn 40-50% yellow and the leaves soften. Then, keep the dry-bulb temperature constant and increase the wet-bulb temperature to 36-37℃ at a rate of 1℃ / 3h, and bake at a stable temperature until the tobacco leaves turn 70-80% yellow and the midrib softens. Phase Four: Coordination Phase The dry bulb temperature was raised to 42-43℃ and the wet bulb temperature to 35.5-36.5℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they turned completely yellow, the tips curled, the lateral veins were almost completely white, and more than 1 / 10 of the main vein turned white. Fifth stage: Low temperature and high humidity color fixing stage The dry-bulb temperature was increased to 44-46℃ and the wet-bulb temperature to 37-38℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they were semi-dry, rolled into small rolls, and the main veins were nearly completely yellow and more than 1 / 4 dry. After that, the dry-bulb temperature was increased to 48-50℃ and the wet-bulb temperature to 38-39℃ at a rate of 1℃ / 3h. The tobacco leaves were then baked at a stable temperature until they were completely dry, rolled into large rolls, and the main veins were more than 1 / 3 dry. Phase 6: Rapid Drying Stage Increase the dry bulb temperature to 59-60℃ and the wet bulb temperature to 40-41℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 6-10 hours; then increase the dry bulb temperature to 66-67℃ and the wet bulb temperature to 40.5-41.5℃ at a heating rate of 1℃ / h, and bake at a stable temperature until the entire batch of tobacco leaves is dry.

[0010] The aforementioned method to reduce the starvation and ash accumulation of lower tobacco leaves is to control the wet-bulb heating rate in the third stage, when the tobacco leaves are 70-80% yellow, so that the degree of water loss of the tobacco leaves is higher than the degree of yellowing, and to ensure that the main vein of the tobacco leaves is fully softened.

[0011] The beneficial effects of this invention are: By cleaning the bottom leaves twice and removing 1-2 leaves from the lower two sheds, the field ventilation and light conditions for the remaining lower leaves can be improved in advance, optimizing their growth microenvironment. This effectively avoids premature aging and over-ripening of tobacco leaves due to nutrient competition, preventing the formation of "starved tobacco leaves," thereby promoting the full development of the remaining leaves and increasing leaf thickness, thus improving the quality of the cured tobacco leaves. Using the budding and topping method aims to inhibit the excessive consumption of assimilated products by the plant's reproductive growth, concentrating nutrients to the leaves, promoting dry matter accumulation, and further increasing leaf thickness. By harvesting fresh tobacco leaves at over 80% physiological maturity in the field, the ineffective consumption of nutrients by the lower leaves in the field can be minimized, preventing over-ripening. By classifying and bundling the tobacco leaves into different tiers and reducing the amount of tobacco loaded by 9.09%~25.00%, the total moisture load in the curing barn can be significantly reduced, increasing the gaps between tobacco leaves and optimizing airflow circulation, thereby promoting timely moisture removal and color stability during the curing process.

[0012] In terms of the curing process, a low-temperature preheating process of 30-36℃ for yellowing and a primary yellowing treatment of 37-38℃ are adopted. This avoids the drawbacks of the traditional process of slow yellowing at low temperatures for a long time, and reduces excessive consumption of nutrients due to respiration during this stage. In the main yellowing and wilting stage, the tobacco leaves are first cured at a stable temperature of 39-41℃ for dry bulbs and 35℃ for wet bulbs, which promotes yellowing of 40-50% and softens the leaves. Then, while maintaining the dry bulb temperature, the wet bulb temperature is raised to 36-37℃ at a rate of 1℃ / 3h and stabilized until the tobacco leaves are 70-80% yellow and the midribs are softened. This strategy follows the principle of "removing water first, then coloring," ensuring that the tobacco leaves first lose water and wilt appropriately before fully yellowing, effectively preventing "hard yellowing" and ash formation, and laying the foundation for subsequent yellowing and drying coordination. At the same time, the primary yellowing at a dry bulb temperature of 39-41℃ accelerates the yellowing process, further reducing the respiration consumption of the lower leaves and preventing excessive yellowing of the tobacco leaves. During the yellowing-drying coordination stage, the yellowing and moisture loss of tobacco leaves are further increased at a dry-bulb temperature of 42-43℃, with target values ​​higher than conventional curing. This effectively inhibits the activity of enzymatic browning reactions in tobacco leaves, reduces the risk of enzymatic browning, prevents browning and ash formation, and achieves simultaneous coordination of yellowing and drying. In the low-temperature, high-humidity color-fixing stage, the tobacco leaves are dried at a higher standard than conventional processes within a dry-bulb temperature range of 44-50℃. This continuously inhibits the activity of enzymes involved in the browning reaction, ensuring safe color fixation. Simultaneously, the high-humidity color-fixing helps increase the proportion of orange-yellow tobacco leaves and deepen their orange hue. In the rapid drying stage, the temperature is rapidly increased within a dry-bulb temperature range of 51-67℃ to promote rapid drying of the midrib. This operation shortens the duration of high temperatures, reduces the loss of aroma compounds through volatilization, and thus improves the sensory quality of the cured tobacco leaves. During the drying stage at dry-bulb temperatures of 37-50℃, reducing the heating rate to within 1℃ / 3-4h coordinates the activity of enzymes involved in the yellowing, dehydration, and browning processes of tobacco leaves. This promotes coordinated yellowing and drying, effectively reducing the risk of browning and ash formation, and further decreasing the proportion of ash-covered tobacco after drying. In other words, the "six-stage drying process" precisely controls the yellowing and dehydration process, systematically preventing starvation and ash formation from the source to the entire process.

[0013] In summary, this invention integrates agronomical measures such as secondary cleaning of bottom leaves, cleaning 1-2 leaves from the lower second shed, budding and topping, harvesting at physiological maturity, sorting and weaving, and layering for drying, along with the aforementioned six-stage drying process. This improves the field environment, optimizes ventilation and light penetration for the lower leaves, promotes nutrient accumulation, reduces unnecessary nutrient loss in the field and during the early stages of drying, avoids over-ripening and excessive yellowing, promotes efficient and timely moisture loss and color stability of tobacco leaves, significantly reduces the incidence of browning and starvation, and systematically overcomes the shortcomings of existing conventional production and three-stage drying methods.

[0014] Meanwhile, the cured tobacco leaves have the following advantages: 1. It helps improve the appearance quality of the lower tobacco leaves; 2. It helps improve the grade structure of lower tobacco leaves and the weight of individual leaves; 3. It helps to significantly reduce the proportion of ash and soot on the lower tobacco leaves; 4. It helps improve the sensory quality of the lower flue-cured tobacco leaves. Detailed Implementation

[0015] 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.

[0016] Example 1: The method for reducing the starvation and ash accumulation of lower tobacco leaves is achieved through the following steps: S1 Secondary Removal of Bottom Leaves: Remove 1-2 bottom leaves for the first time 35 days after transplanting in the field; remove 1-2 bottom leaves for the second time 45 days after transplanting; S2 Cleaning of the second-lowest tobacco leaves: 55 days after transplanting in the field, clean 1-2 leaves from the bottom second-lowest tobacco leaves; S3 Budding and Topping: The budding and topping method is adopted; the specific operation of budding and topping is as follows: on a sunny morning, when the flower bud extends out of the top leaf, reaches a length of 3-5cm, is still green, is clearly distinguishable from the top young leaf, and the petals wrapped by the calyx are visible, remove the flower bud, flower stalk and 2-3 underdeveloped small leaves below it. S4 Physiological Maturity Harvesting: When more than 80% of the tobacco leaves in the lower two sheds of the tobacco field reach physiological maturity, the lower tobacco leaves are harvested; the criteria for judging physiologically mature tobacco leaves are: the basic color of the tobacco leaf surface is green and glossy, the leaf tip and base are light yellow, more than 1 / 2 of the main veins turn white, the pubescence is lost, the leaf surface is slightly wrinkled, the leaf tip and leaf edge droop slightly, the picking sound is crisp, the cross-section is neat, and there is no stem bark; S5 Classification and Bagging: According to the maturity characteristics of tobacco leaves, fresh tobacco leaves are divided into four categories: immature, physiologically mature, technologically mature, and over-mature. Tobacco leaves with no curing value are removed, and the leaves are classified and bundled into bamboo poles, with 100-120 leaves per pole. S6 Layered Loading: Following the principle of "same layer, same quality," fresh tobacco leaves with lower maturity are loaded into the low-temperature layer of the intensive curing barn, while those with higher maturity are loaded into the high-temperature layer. The loading amount is 270-300 sticks, a reduction of 9.09%-25.00% compared to the conventional loading amount of 330-360 sticks. S7 Baking: Baking is carried out according to a six-stage baking process, which includes low-temperature preheating and yellowing stage, initial yellowing stage, main yellowing and wilting stage, yellowing and drying coordination stage, low-temperature and medium-high humidity color fixing stage, and rapid drying stage.

[0017] The six-stage baking process includes: Phase 1: Low-temperature preheating and yellowing stage After ignition, the dry bulb temperature is raised to 30℃ and the wet bulb temperature is 30℃ at a heating rate of 1℃ / h, and then the temperature is maintained for 4 hours. After that, the dry bulb temperature is raised to 35℃ and the wet bulb temperature is 34.5℃ at a heating rate of 1℃ / h, and the temperature is maintained for 6 hours to preheat the tobacco leaves and make them turn yellow by 10-20%. Phase Two: Initial Yellowing Stage The dry bulb temperature was raised to 37°C and the wet bulb temperature to 36°C at a heating rate of 1°C / h. The temperature was kept stable for 20 hours until the tobacco leaves turned 30-40% yellow and 1 / 3 of the leaves softened. Third stage: Main yellowing and withering stage The dry bulb temperature was increased to 39℃ and the wet bulb temperature to 35℃ at a rate of 1℃ / 4h. The temperature was then maintained for 10h until the tobacco leaves turned 40-50% yellow and softened. After that, the dry bulb temperature was kept constant, and the wet bulb temperature was increased to 36℃ at a rate of 1℃ / 3h. The temperature was then maintained for 10h until the tobacco leaves turned 70-80% yellow and the midrib softened. When the tobacco leaves turn 70-80% yellow, the wet-bulb heating rate needs to be controlled to ensure that the degree of water loss from the tobacco leaves is greater than the degree of yellowing, thus ensuring that the main veins of the tobacco leaves soften sufficiently. Phase Four: Coordination Phase The dry bulb temperature was raised to 42℃ and the wet bulb temperature to 35.5℃ at a heating rate of 1℃ / 4h. The temperature was kept stable until the tobacco leaves turned completely yellow, the tips curled and the edges rolled up, the lateral veins were almost completely white, and more than 1 / 10 of the main vein turned white. Fifth stage: Low temperature and high humidity color fixing stage The dry-bulb temperature was increased to 44℃ and the wet-bulb temperature to 37℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they were semi-dry, rolled into small rolls, and the main veins were nearly completely yellow and more than 1 / 4 dry. After that, the dry-bulb temperature was increased to 48℃ and the wet-bulb temperature to 38℃ at a rate of 1℃ / 3h. The tobacco leaves were then baked at a stable temperature until they were completely dry, rolled into large rolls, and the main veins were more than 1 / 3 dry. Phase 6: Rapid Drying Stage The dry bulb temperature was increased to 59℃ and the wet bulb temperature to 40℃ at a heating rate of 1℃ / h, and then the temperature was maintained for 10 hours. After that, the dry bulb temperature was increased to 66℃ and the wet bulb temperature to 40.5℃ at a heating rate of 1℃ / h, and the temperature was maintained for 1 hour until the entire batch of tobacco leaves was dry.

[0018] Example 2: This is an adjustment to the six-stage baking process based on Example 1, specifically as follows: Phase 1: Low-temperature preheating and yellowing stage After ignition, the dry bulb temperature is raised to 33°C and the wet bulb temperature is 33°C at a heating rate of 1°C / h, and then the temperature is maintained for 3 hours. After that, the dry bulb temperature is raised to 36°C and the wet bulb temperature is 35.5°C at a heating rate of 1°C / h, and the temperature is maintained for 4 hours to preheat the tobacco leaves and make them turn yellow by 10-20%. Phase Two: Initial Yellowing Stage The dry bulb temperature was raised to 38℃ and the wet bulb temperature to 37℃ at a heating rate of 1℃ / h. The temperature was kept stable for 15 hours until the tobacco leaves turned 30-40% yellow and 1 / 3 of the leaves softened. Third stage: Main yellowing and withering stage The dry bulb temperature was increased to 41℃ and the wet bulb temperature to 35℃ at a rate of 1℃ / 4h. The temperature was then maintained for 6h until the tobacco leaves turned 40-50% yellow and the leaves softened. After that, the dry bulb temperature was kept constant, and the wet bulb temperature was increased to 37℃ at a rate of 1℃ / 3h. The temperature was then maintained for 6h until the tobacco leaves turned 70-80% yellow and the midrib softened. When the tobacco leaves turn 70-80% yellow, the wet-bulb heating rate needs to be controlled to ensure that the degree of water loss from the tobacco leaves is greater than the degree of yellowing, thus ensuring that the main veins of the tobacco leaves soften sufficiently. Phase Four: Coordination Phase The dry bulb temperature was raised to 43℃ and the wet bulb temperature to 36.5℃ at a heating rate of 1℃ / 4h. The temperature was kept stable until the tobacco leaves turned completely yellow, the tips curled and the edges rolled up, the lateral veins were almost completely white, and more than 1 / 10 of the main vein turned white. Fifth stage: Low temperature and high humidity color fixing stage The dry-bulb temperature was increased to 46℃ and the wet-bulb temperature to 38℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they were semi-dry, rolled into small rolls, and the main veins were nearly completely yellow and more than 1 / 4 dry. After that, the dry-bulb temperature was increased to 50℃ and the wet-bulb temperature to 39℃ at a rate of 1℃ / 3h. The tobacco leaves were then baked at a stable temperature until they were completely dry, rolled into large rolls, and the main veins were more than 1 / 3 dry. Phase 6: Rapid Drying Stage The dry bulb temperature was increased to 60℃ and the wet bulb temperature to 41℃ at a heating rate of 1℃ / h, and then the temperature was maintained for 6 hours. After that, the dry bulb temperature was increased to 67℃ and the wet bulb temperature to 41.5℃ at a heating rate of 1℃ / h, and the temperature was maintained for 6 hours until the entire batch of tobacco leaves was dry.

[0019] Example 3: This is an adjustment to the six-stage baking process based on Example 1, specifically as follows: Phase 1: Low-temperature preheating and yellowing stage After ignition, the dry bulb temperature is raised to 32°C and the wet bulb temperature to 31°C at a heating rate of 1°C / h, and then the temperature is maintained for 3 hours. After that, the dry bulb temperature is raised to 36°C and the wet bulb temperature to 35°C at a heating rate of 1°C / h, and the temperature is maintained for 5 hours to preheat the tobacco leaves and make them turn yellow by 10-20%. Phase Two: Initial Yellowing Stage The dry bulb temperature was raised to 38℃ and the wet bulb temperature to 37℃ at a heating rate of 1℃ / h. The temperature was kept stable for 18 hours until the tobacco leaves turned 30-40% yellow and 1 / 3 of the leaves softened. Third stage: Main yellowing and withering stage The dry bulb temperature was increased to 40℃ and the wet bulb temperature to 35℃ at a rate of 1℃ / 4h. The temperature was then maintained for 8h until the tobacco leaves turned 40-50% yellow and the leaves softened. After that, the dry bulb temperature was kept constant, and the wet bulb temperature was increased to 37℃ at a rate of 1℃ / 3h. The temperature was then maintained for 80-70% yellow and the midrib softened. When the tobacco leaves turn 70-80% yellow, the wet-bulb heating rate needs to be controlled to ensure that the degree of water loss from the tobacco leaves is greater than the degree of yellowing, thus ensuring that the main veins of the tobacco leaves soften sufficiently. Phase Four: Coordination Phase The dry bulb temperature was raised to 43℃ and the wet bulb temperature to 36℃ at a heating rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they turned completely yellow, the tips curled, the lateral veins were almost completely white, and more than 1 / 10 of the main vein turned white. Fifth stage: Low temperature and high humidity color fixing stage The dry bulb temperature was increased to 45℃ and the wet bulb temperature to 38℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they were semi-dry, rolled into small rolls, and the main veins were nearly completely yellow and more than 1 / 4 dry. After that, the dry bulb temperature was increased to 49℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 3h. The tobacco leaves were then baked at a stable temperature until they were completely dry, rolled into large rolls, and the main veins were more than 1 / 3 dry. Phase 6: Rapid Drying Stage The dry bulb temperature was increased to 60℃ and the wet bulb temperature to 41℃ at a heating rate of 1℃ / h, and then the temperature was maintained for 8 hours. After that, the dry bulb temperature was increased to 67℃ and the wet bulb temperature to 41℃ at a heating rate of 1℃ / h, and the temperature was maintained for 8 hours until the entire batch of tobacco leaves was dry.

[0020] Effect comparison test The experiment was conducted in the tobacco-growing area of ​​the Tobacco Science and Technology Park in Heishi Town, Weining County, Bijie City, Guizhou Province, from 2024 to 2025. The tested flue-cured tobacco variety was Yunyan 87, and the third leaf (from bottom to top) in the second greenhouse was used as the research object. The tested curing barn was a standard dense curing barn with descending airflow. A comparative experiment was conducted using the local conventional planting management and harvesting and curing methods as a control and the method of this invention as a comparative treatment.

[0021] (a) Control (CK): Conventional planting method and harvesting and drying S1 Clean the bottom leaves: Clean 2-3 bottom leaves when topping; S2 Initial Flowering and Topping: When the inflorescence at the top of the tobacco plant has fully extended beyond the top leaf and the first central flower on the main inflorescence has just opened, remove the entire inflorescence along with the 2-3 small leaves below it. S3 mature harvesting: When the tobacco leaves in the second greenhouse reach the mature stage of the process, they are harvested. The criteria for judging this are: the basic color of the tobacco leaf surface is green with a small amount of light yellow, it is glossy, the leaf tip and base are yellow, more than 2 / 3 of the main veins are fading and turning white, the pubescence is lost, the leaf surface is slightly wrinkled, the leaf tip and leaf edge droop slightly, the picking sound is crisp, the cross-section is neat, and there is no stem bark. S4 Classification and Bagging: According to the maturity characteristics of tobacco leaves, fresh tobacco leaves are divided into four categories: immature, physiologically mature, technologically mature, and over-mature. Tobacco leaves with no curing value are removed, and the leaves are classified and bundled into bamboo poles, with 130 to 150 leaves per pole. S5 Layered Loading: Tobacco is loaded according to the principle of "same layer, same quality". Fresh tobacco leaves with low maturity are loaded in the low-temperature layer of the intensive curing room, while fresh tobacco leaves with high maturity are loaded in the high-temperature layer of the intensive curing room. The amount of tobacco loaded is 330~360 sticks. S6 Curing: Carry out the curing process according to the conventional three-stage curing process for flue-cured tobacco (GB / T 23219—2008).

[0022] S6-1 Yellowing Stage: After loading the tobacco, raise the temperature of the curing barn to 30℃ with a low fire, maintaining a wet-bulb temperature of 30℃, and cure at a stable temperature until the leaf tips turn yellow. Then, increase the dry-bulb temperature to 36℃ at a rate of 1℃ / h, maintaining a wet-bulb temperature of 35℃, until the tobacco leaves are 20-30% yellow. Next, increase the dry-bulb temperature to 38℃ at a rate of 1℃ / h, maintaining this temperature for an extended period, controlling the wet-bulb temperature at 36-37℃, so that about 80% of the tobacco leaves in the thermometer-hanging section of the curing barn reach 70-80% yellow, while simultaneously softening the leaves (with approximately 30% water loss). Then, increase the dry-bulb temperature to 40℃ at a rate of 1℃ / 2-3h, maintaining a wet-bulb temperature of 36℃, and cure at a stable temperature for 10 hours. Finally, increase the temperature to 42℃, maintaining a wet-bulb temperature of 37℃, extending the curing time until the tobacco leaves are yellow with slightly green veins, wilting and collapsing, and the midrib softens.

[0023] S6-2 Color Fixing Period: The dry-bulb temperature is increased to 45℃ at a rate of 1℃ / 3h, while the wet-bulb temperature is maintained at 37℃. The leaves are then baked at this stable temperature until the tips and edges curl. Next, the dry-bulb temperature is increased to 48℃ at the same rate and maintained, while the wet-bulb temperature is maintained at 38℃. This process is prolonged until the leaf veins turn yellow and the leaves lose moisture to the point of forming small rolls. Then, the dry-bulb temperature is increased to 54℃ at a rate of 1℃ / 2h and maintained for 12h to achieve complete leaf drying. As the dry-bulb temperature rises, the wet-bulb temperature gradually increases and stabilizes at 39℃.

[0024] S6-3 Drying Stage: Increase the dry-bulb temperature from 54℃ to 65℃ at a rate of 1℃ / h and maintain it until the tobacco leaves are completely dry. Before the dry-bulb temperature reaches 60℃, maintain the wet-bulb temperature at 40℃; after reaching 60℃, gradually close the inlet and outlet vents, reduce the ventilation volume, and maintain the wet-bulb temperature at 41℃.

[0025] (ii) Processing (T): The method of the present invention, Examples 1-3 are all acceptable. Using conventional planting management, harvesting, and curing as the control (CK), and the method of this invention as the comparative treatment (T), fresh tobacco leaf samples were placed in the middle layer of two standard dense curing barns, at a distance of 6 tobacco poles from the entrance of the loading chamber. The effects of different treatments on the appearance quality, grade structure, single leaf weight, proportion of ash-covered tobacco leaves, and sensory quality of the lower tobacco leaves after curing are described below: 1. Tobacco leaf appearance quality Table 1. Effects of different treatments on the appearance quality of cured tobacco leaves

[0026] Note: "+" indicates that it is better than the control.

[0027] As shown in Table 1, compared with the control (CK), the X2F tobacco leaves cured by the method of the present invention show significant improvements in identity, oil content, and color, while the differences in color, maturity, and leaf structure are not significant. This indicates that the method of the present invention is beneficial to improving the appearance quality of the lower tobacco leaves.

[0028] 2. Tobacco leaf grade structure, single leaf weight, and proportion of ash-covered tobacco. Table 2. Effects of different treatments on grade structure, single leaf weight, and proportion of ash-covered tobacco leaves after curing.

[0029] Note: Different lowercase letters in the same column indicate that different treatments are significantly different at the 0.05 level.

[0030] As shown in Table 2, compared with the control (CK), the method of this invention significantly improves the proportion of orange-yellow tobacco, the proportion of high-grade tobacco, the average price, and the weight per leaf after curing, while significantly reducing the proportion of ash-covered tobacco. In summary, the method of this invention helps to improve the grade structure and weight per leaf of cured tobacco, and reduces the proportion of ash-covered tobacco.

[0031] 3. Sensory quality of tobacco leaves Table 3 Effects of different treatments on the sensory quality of cured tobacco leaves

[0032] Note: Sensory quality evaluation is the sum of six items: aroma quality, aroma quantity, taste, off-flavors, irritation, and strength, with each item worth 9 points.

[0033] As shown in Table 3, compared with CK, the X2F tobacco leaves cured by the method of the present invention show significant improvements in aroma quality, aroma quantity, taste, and irritation, while the differences in off-flavors and strength are not significant, resulting in a total score increase of 1.5 points. This indicates that the method of the present invention is beneficial for improving the sensory quality of cured tobacco leaves.

[0034] 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 reducing the starvation and ash accumulation of lower tobacco leaves, characterized in that, include: S1 Secondary Removal of Bottom Leaves: Remove 1-2 bottom leaves for the first time 35 days after transplanting in the field; remove 1-2 bottom leaves for the second time 45 days after transplanting; S2 Cleaning of the second-lowest tobacco leaves: 55 days after transplanting in the field, clean 1-2 leaves from the bottom second-lowest tobacco leaves; S3 Budding and Topping: Adopts the budding and topping method; S4 Physiological Maturity Harvesting: When more than 80% of the tobacco leaves in the lower two sheds of the tobacco field have reached physiological maturity, the lower tobacco leaves are harvested. S5 Classification and Bagging: According to the maturity characteristics of tobacco leaves, fresh tobacco leaves are divided into four categories: immature, physiologically mature, technologically mature, and over-mature. Tobacco leaves with no curing value are removed, and the leaves are classified and bundled into bamboo poles, with 100-120 leaves per pole. S6 Layered Loading: Following the principle of "same layer, same quality," fresh tobacco leaves with lower maturity are loaded into the low-temperature layer of the intensive curing barn, while those with higher maturity are loaded into the high-temperature layer. The loading amount is 270-300 sticks, a reduction of 9.09%-25.00% compared to the conventional loading amount of 330-360 sticks. S7 Baking: Baking is carried out according to a six-stage baking process, which includes low-temperature preheating and yellowing stage, initial yellowing stage, main yellowing and wilting stage, yellowing and drying coordination stage, low-temperature and medium-high humidity color fixing stage, and rapid drying stage.

2. The method for reducing the starvation and ash accumulation of lower tobacco leaves according to claim 1, characterized in that, In step S3, the specific operation of bud removal is as follows: on a sunny morning, when the flower bud extends beyond the top leaf, reaches a length of 3-5 cm, is still green, is clearly distinguishable from the young top leaf, and the petals wrapped by the calyx are visible, remove the flower bud, flower stalk, and 2-3 underdeveloped small leaves below it.

3. The method for reducing the starvation and ash accumulation of lower tobacco leaves according to claim 2, characterized in that, In step S4, the criteria for determining physiologically mature tobacco leaves are as follows: the basic color of the tobacco leaf surface is green and glossy, the leaf tip and base are light yellow, more than 1 / 2 of the main veins turn white, the pubescence is lost, the leaf surface is slightly wrinkled, the leaf tip and leaf edge droop slightly, the picking sound is crisp, the cross-section is neat, and there is no stem bark.

4. The method for reducing the starvation and ash accumulation of lower tobacco leaves according to any one of claims 1-3, characterized in that, The six-stage baking process includes: Phase 1: Low-temperature preheating and yellowing stage After ignition, the dry bulb temperature is raised to 30-33℃ and the wet bulb temperature is raised to 30-33℃ at a rate of 1℃ / h, and then the temperature is maintained for 3-4 hours. After that, the dry bulb temperature is raised to 35-36℃ and the wet bulb temperature is raised to 34.5-35.5℃ at a rate of 1℃ / h, and then the temperature is maintained for 4-6 hours to preheat the tobacco leaves and make them turn yellow by 10-20%. Phase Two: Initial Yellowing Stage Raise the dry bulb temperature to 37-38℃ and the wet bulb temperature to 36-37℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 15-20 hours until the tobacco leaves turn 30-40% yellow and 1 / 3 of the leaves soften. Third stage: Main yellowing and withering stage Increase the dry-bulb temperature to 39-41℃ and the wet-bulb temperature to 35℃ at a rate of 1℃ / 4h, and bake at a stable temperature for 6-10h until the tobacco leaves turn 40-50% yellow and the leaves soften. Then, keep the dry-bulb temperature constant and increase the wet-bulb temperature to 36-37℃ at a rate of 1℃ / 3h, and bake at a stable temperature until the tobacco leaves turn 70-80% yellow and the midrib softens. Phase Four: Coordination Phase The dry bulb temperature was raised to 42-43℃ and the wet bulb temperature to 35.5-36.5℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they turned completely yellow, the tips curled, the lateral veins were almost completely white, and more than 1 / 10 of the main vein turned white. Fifth stage: Low temperature and high humidity color fixing stage The dry-bulb temperature was increased to 44-46℃ and the wet-bulb temperature to 37-38℃ at a rate of 1℃ / 4h. The tobacco leaves were then baked at a stable temperature until they were semi-dry, rolled into small rolls, and the main veins were nearly completely yellow and more than 1 / 4 dry. After that, the dry-bulb temperature was increased to 48-50℃ and the wet-bulb temperature to 38-39℃ at a rate of 1℃ / 3h. The tobacco leaves were then baked at a stable temperature until they were completely dry, rolled into large rolls, and the main veins were more than 1 / 3 dry. Phase 6: Rapid Drying Stage Increase the dry bulb temperature to 59-60℃ and the wet bulb temperature to 40-41℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 6-10 hours; then increase the dry bulb temperature to 66-67℃ and the wet bulb temperature to 40.5-41.5℃ at a heating rate of 1℃ / h, and bake at a stable temperature until the entire batch of tobacco leaves is dry.

5. The method for reducing the starvation and ash accumulation of lower tobacco leaves according to claim 4, characterized in that, In the third stage, when the tobacco leaves turn 70-80% yellow, the wet-bulb heating rate needs to be controlled to ensure that the degree of water loss from the tobacco leaves is higher than the degree of yellowing, thus ensuring that the main veins of the tobacco leaves soften sufficiently.

Images