Structure optimization and baking process for flue-cured tobacco variety Guiyan 20 tobacco leaves

Abstract

The invention discloses a flue-cured tobacco variety Guiyan 20 tobacco leaf structure optimization and flue-curing process. The flue-cured tobacco variety Guiyan 20 tobacco leaf structure optimization and flue-curing process comprises the following steps of tobacco plant structure optimization, tobacco branch stem reservation, fresh tobacco harvesting, classified tobacco weaving, reasonable kang loading and differentiated flue-curing. The lower leaves adopt a high-temperature quick baking process of'high-temperature yellowing + medium-high humidity color fixing + high-temperature stem drying ', the middle leaves adopt a medium-temperature slow baking process of'slow heating + stable wet bulb temperature main yellowing + medium-high humidity color fixing', and the upper leaves adopt a high-temperature slow baking process of'slow heating + high-temperature high-humidity sweating yellowing + high drying degree and medium-high humidity color fixing '; the appearance quality and the economic benefit of the baked tobacco leaves are obviously improved.

Description

Technical Field

[0001] This invention relates to the structural optimization and curing process of the leaves of the flue-cured tobacco variety Guiyan 20, belonging to the field of flue-cured tobacco cultivation and curing technology. Background Technology

[0002] As an important economic crop, the curing process of flue-cured tobacco directly determines the quality and value of the final tobacco leaves. The curing process is a complex physical and biochemical process, its core lying in controlling the curing environment (such as temperature and humidity) to induce a series of beneficial material transformations and morphological changes within the tobacco leaves, ultimately yielding tobacco products with excellent appearance and internal quality, including superior color, aroma, and texture. Therefore, developing curing processes tailored to the physiological and curing characteristics of specific flue-cured tobacco varieties is crucial for improving tobacco leaf quality.

[0003] Traditional tobacco curing processes typically follow a three-stage curing principle, dividing the curing process into three stages: yellowing, color setting, and core drying. During the yellowing stage, suitable temperature and humidity conditions promote the degradation of large molecules like starch in the tobacco leaves into smaller sugar molecules, while chlorophyll decomposes, causing the leaves to turn from green to yellow. During the color setting stage, temperature is gradually increased and humidity decreased to fix the formed yellow color and promote the formation of aroma compounds, while preventing enzymatic browning that leads to browning and ash formation. In the core drying stage, temperature is further increased to thoroughly remove moisture from the midrib, completing the drying process. Existing technologies have disclosed numerous curing processes for specific flue-cured tobacco varieties. These processes are usually based on the general three-stage curing principle, with optimized adjustments to temperature and humidity parameters, heating rates, and temperature stabilization times at each stage according to the curing characteristics of the target variety.

[0004] For example, patent document (authorization announcement number: CN115777977B) discloses a method for constructing a matching curing process based on the evaluation of the curing characteristics of flue-cured tobacco varieties or lines. Through dark-box experiments, in-curing experiments, post-curing experiments, and evaluation of curing characteristics, a matching curing process suitable for the tested flue-cured tobacco varieties (lines) is optimized. Patent document (publication number: CN104997151A) discloses a curing process for the flue-cured tobacco variety Yunyan 99. Based on the characteristics and quality of Yunyan 99 tobacco leaves, a five-step, three-stage curing method is adopted, which can effectively maintain the stability of the tobacco leaf color, improve leaf wrinkling, and significantly increase oil content and aroma. Patent document (authorization announcement number: CN107028214B) discloses a flue-cured tobacco curing process suitable for Yunyan 116 tobacco leaves. By setting steps such as the yellowing period, wilting period, pre-coloring period, post-coloring period, and drying period, the quality of the cured tobacco leaves is effectively improved. Patent document (authorization announcement number: CN116869207B) discloses a curing method suitable for the upper leaves of flue-cured tobacco variety K326. By controlling the wet-bulb temperature in a "V"-shaped change pattern during the mid-yellowing to late-color-fixing stage, and exhibiting double "39℃-40℃" and "41℃-42℃" dry-bulb temperatures during the mid-yellowing and late-yellowing stages respectively, and reducing the wet-bulb temperature by 0.5℃~1℃ in the later stages of each stage, the degree and proportion of ash on the upper leaves after curing are significantly reduced. Patent document (publication number: CN106539117A) discloses a harvesting and curing method to reduce ash and discoloration on the upper leaves of the Honghua Dajinyuan variety. This method involves continuous irrigation of the tobacco field during the upper leaf maturity period, harvesting six upper leaves at once after they reach the first leaf maturity level, and then curing them normally until yellowing. The method involves a steady increase in temperature and slow dehumidification to promote full wilting and gradual color fixation and drying, effectively reducing the proportion of ash and discolored tobacco. Patent document (authorization announcement number: CN108065447B) discloses a method for curing the green tobacco leaves of the Honghua Dajinyuan flue-cured tobacco variety. By fully softening the leaves at dry-bulb temperatures of 40℃~42℃ / 37℃~38℃, turning the leaves yellow to 80-90% at dry-bulb temperatures of 37℃~38℃ / 35℃~36℃, and causing the leaves to turn yellow with green veins and collapse at dry-bulb temperatures of 42℃ / 35℃~36℃, and yellow with yellow veins and hooked tips and curled edges at dry-bulb temperatures of 45℃ / 36℃~37℃, the method can effectively increase the proportion of high-grade tobacco leaves after curing and significantly reduce the proportion of green tobacco, mixed-color tobacco, and rotten tobacco. Patent document (authorization announcement number: CN101991180B) discloses a tobacco curing process that can improve the curing quality of flue-cured tobacco variety KRK26. Through low temperature humidity adjustment for yellowing, stable temperature and humidity dehumidification for wilting, ventilation and dehydration for drying leaves, and temperature and humidity control for drying the core, KRK26 tobacco leaves can be smoothly yellowed, timely colored, and dried in a timely manner during the curing process.Patent document (publication number: CN111035039A) discloses a curing process for the KRK26 flue-cured tobacco variety. By employing a "slow-to-steady-to-fast seven-step low-temperature, low-humidity curing process," it resolves three key relationships: yellowing and wilting of tobacco leaves, color fixation and aroma, and dryness and color. Patent document (publication number: CN104621704A) discloses a curing process and corresponding operational techniques for the KRK26 flue-cured tobacco variety, establishing a series of technologies for mature tobacco harvesting and curing centered on a "low-temperature, medium-humidity, seven-step" curing process. Patent documents (publication numbers: CN110122913A and CN107736642A) disclose curing processes for the Yuyan No. 6 and Yuyan No. 11 flue-cured tobacco varieties, respectively. By implementing steps such as pre-curing preparation, yellowing, color fixation, and dryness, they significantly improve the quality of cured tobacco leaves and the proportion of high-grade tobacco. Patent document (authorization announcement number: CN108065447B) discloses a special baking method for removing greenness, preventing blackening, and maintaining yellowness in Yuyan No. 9 tobacco. By coordinating the yellowing stage, the dehumidification and color-fixing stage, and the medium-moisture drying stage, it effectively solves problems such as unsuitable yellowing, asynchronous yellowing and dehydration, and difficulty in color fixing. Patent document (publication number: CN119867347A) discloses a baking process for a new flue-cured tobacco variety, Zhongchuan 208. By adopting different temperature and humidity combinations and carrying out staged baking during the sweating period, yellowing period, gluten formation period, color fixing period, and gluten drying period, it greatly improves the quality of the cured tobacco leaves and the coordination of the chemical composition of the tobacco leaves. Patent document (authorization announcement number: CN115836741B) discloses a baking method and application for improving the baking quality of the Y2001 flue-cured tobacco variety. By implementing baking processes such as "high-humidity rapid yellowing, 40℃ micro-dehumidification, and increased dehumidification in the early stage of color fixing," it achieves simultaneous improvement in the yield, aroma quality, and economic benefits of the cured tobacco leaves. Patent document (authorization announcement number: CN106954879B) discloses a method for slow-temperature roasting of Xiangyan No. 5 tobacco leaves. By implementing a slow-temperature roasting process and coordinating the control of key parameters such as tobacco weaving, the roasting quality and economic benefits of the tobacco leaves are significantly improved. Patent document (authorization announcement number: CN104146333B) discloses a roasting method for the American-imported flue-cured tobacco variety NC297. By setting differentiated roasting parameters for different parts of the tobacco leaves, the proportion of ash-covered, green-cured, and discolored tobacco leaves is effectively reduced. Patent document (authorization announcement number: CN106387977B) discloses a roasting method for the flue-cured tobacco variety H892. By adopting a zoned roasting strategy and using a variable frequency fan to precisely control the circulating wind speed during the yellowing, color-fixing, and drying stages, the quality of the roasted tobacco leaves is significantly improved. Patent document (authorization announcement number: CN109892683B) discloses a curing process suitable for flue-cured tobacco leaves of the NC-YATAS6 variety. By harvesting at maturity and performing curing operations during the yellowing period, withering period, pre-coloring period, post-coloring period and dry rib period, the color saturation of the cured tobacco leaves can be effectively improved and the smoking quality can be improved.Patent document (authorization announcement number: CN116326802B) discloses a method for curing the upper leaves of GZ36 flue-cured tobacco. This method involves judging the curing characteristics of the upper leaves of GZ36, harvesting at maturity, classifying and binding the tobacco, and loading it into curing kilns. The method utilizes a dry-bulb temperature cycling method during the yellowing stage, which effectively improves the intrinsic quality of the upper leaves after curing. Patent document (publication number: CN119234650A) discloses a cultivation and curing process for the flue-cured tobacco variety GZ37. Through field cultivation and the adoption of a "medium-temperature, medium-humidity" curing process, the method improves the coordination of chemical components in the cured tobacco leaves and effectively reduces the proportion of green and mixed tobacco.

[0005] However, existing cultivation and curing techniques are mostly concentrated on mainstream varieties such as the Yunyan series, K326, and Honghua Dajinyuan. There is often a lack of targeted research on newly cultivated flue-cured tobacco varieties with unique agronomic traits. "Guiyan 20" is a flue-cured tobacco variety bred by the Guizhou Provincial Tobacco Science Research Institute and the Zunyi Branch of the Guizhou Provincial Tobacco Company through systematic selection from a naturally mutated single plant with a large number of leaves in Yunyan 87. This variety has a relatively large number of leaves (26-29). In field cultivation, the lower leaves suffer from insufficient light due to canopy shading, resulting in insufficient dry matter accumulation and thinner leaves with lower oil content after curing. Meanwhile, the upper leaves are prone to insufficient leaf opening and a dense tissue structure, leading to poor moisture drainage during curing and making them highly susceptible to enzymatic browning and ash formation. Furthermore, compared to the control variety Yunyan 87, the color of the cured leaves from different parts is relatively lighter. The currently used "three-stage curing" or special processes for other flue-cured tobacco varieties are difficult to effectively coordinate the balance between yellowing and dehydration, safe color fixation and appearance quality of "Guiyan 20" tobacco leaves during curing. They cannot simultaneously solve multiple quality defects such as thin lower leaves, easy ash accumulation on upper leaves, and pale overall color. Summary of the Invention

[0006] Based on the above, this invention provides a structural optimization and curing process for the Guiyan 20 flue-cured tobacco leaf, in order to solve the problem that the existing technology lacks systematic and differentiated optimization from field agronomic measures to curing process to address the characteristics of the Guiyan 20 variety, such as "many leaves, thin lower leaves, upper leaves not opening and easy to be covered with ash, and pale color of the tobacco leaves after curing". This addresses the contradiction between "yellowing and water loss" and "safe color fixation and appearance quality" of the tobacco leaves, thereby improving the appearance quality and economic benefits of the cured tobacco leaves.

[0007] The technical solution of this invention is: a structural optimization and curing process for the leaves of the Guiyan 20 flue-cured tobacco variety, comprising the following steps:

[0008] S1. Optimization of tobacco plant structure: Remove 2-3 bottom leaves 15-20 days before topping, remove 2-3 lower leaves 5-10 days before topping, and remove 1-2 lower leaves with no potential curing value when topping;

[0009] S2. Retain the stem of the tobacco branch: After topping, select 1-2 tobacco branches at the first or second leaf position from the top. When they grow to 5-10cm, remove all the leaves and the growing point at the top of the tobacco branch, leaving only the stem part.

[0010] S3. Fresh tobacco harvesting: Harvesting is carried out according to the maturity characteristics of different parts of the tobacco leaves: lower leaves are harvested when physiologically mature, middle leaves are harvested when technologically mature, and upper leaves are harvested when fully mature to high maturity.

[0011] S4. Classification and arranging of tobacco: Fresh tobacco leaves from different parts are classified into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature, and tobacco leaves without curing value are removed; tobacco leaves are then arranged into stalks of the same type and quality, with 130-160 leaves per stalk for lower leaves, 150-180 leaves per stalk for middle leaves, and 170-200 leaves per stalk for upper leaves.

[0012] S5. Reasonable loading of tobacco leaves: tobacco leaves of the same quality are loaded in the same layer. The tobacco leaves with low maturity are loaded in the low temperature layer and the tobacco leaves with high maturity are loaded in the high temperature layer. The lower leaves are loaded with 280-320 sticks of tobacco per kiln, the middle leaves are loaded with 300-340 sticks of tobacco per kiln, and the upper leaves are loaded with 320-360 sticks of tobacco per kiln.

[0013] S6. Differentiated curing methods are adopted according to the part of the tobacco leaf: The lower tobacco leaves adopt a high-temperature fast curing process, with a dry-bulb temperature higher than that of conventional curing during the yellowing period, a wet-bulb temperature higher than that of conventional curing during the color-fixing period, and a dry-bulb temperature higher than that of conventional curing during the rib-drying period; The middle tobacco leaves adopt a medium-temperature slow curing process, with a lower starting dry-bulb temperature than that of conventional curing during the yellowing period, a reduced heating rate, and a stable wet-bulb temperature, and a wet-bulb temperature higher than that of conventional curing during the color-fixing period; The upper tobacco leaves adopt a high-temperature slow curing process, with a slow heating and increased wet-bulb temperature during the yellowing period, and a wet-bulb temperature higher than that of conventional curing during the color-fixing period, while also increasing the degree of dryness of the tobacco leaves.

[0014] Preferably, the physiological maturity harvesting standard for the lower leaves is that the basic color of the leaf surface is green, the leaf tip and edge are obviously fading green, the overall yellowing degree of the tobacco leaf is 30-40%, more than 1 / 3 of the main veins are fading green and turning white, the leaf tip is drooping, and the pubescence is slightly lost.

[0015] Preferably, the mature harvesting standard for the middle leaves is that the basic color of the leaf surface is yellowish-green, the leaf tip and edge turn yellow, the overall yellowing degree of the tobacco leaf is 60-70%, more than 2 / 3 of the main veins turn white, the leaf tip droops obviously, most of the hairs fall off, and light yellow mature spots appear.

[0016] Preferably, the harvesting standard for the upper leaves to be fully mature to high maturity is that the basic color of the leaf surface is yellow, the leaf tip and leaf edge are obviously white, the overall yellowing degree of the tobacco leaf is more than 80%, the main veins are almost completely white, the leaf tip is obviously drooping, the hairs have almost all fallen off, and obvious yellowish-white maturity spots appear.

[0017] Preferably, the upper leaves are harvested when they are fully mature and at a high degree of maturity, and 1-2 top leaves that have no baking value are discarded.

[0018] Preferably, the specific operation of the high-temperature rapid baking process is as follows:

[0019] S1 下 Yellowing stage: After ignition, raise the dry bulb temperature to 37℃ and the wet bulb temperature to 36.5℃ at a rate of 1℃ / h, and bake at a stable temperature for 6~10h until the tobacco leaves turn 30-40% yellow; then, raise the dry bulb temperature to 39℃ and the wet bulb temperature to 36℃~37℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 15~20h until the tobacco leaves turn 70-80% yellow and the leaves soften; then, raise the dry bulb temperature to 42℃ and the wet bulb temperature to 36℃~37℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 10~15h until the tobacco leaves are yellow with green veins, the main veins soften, and the leaf tips and edges curl slightly.

[0020] S2 下 Color fixing period: Increase the dry bulb temperature to 44℃~45℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 3h, and bake at a stable temperature for 6~10h until the tip of the tobacco leaf is more than 3cm dry; then, increase the dry bulb temperature to 48℃~50℃ and the wet bulb temperature to 37.5℃~38.5℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 10~15h until more than 1 / 2 of the tobacco leaf is dry and the main vein is completely white; then, increase the dry bulb temperature to 54℃~55℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 2h, and bake at a stable temperature until all the tobacco leaves in the chamber are completely dry.

[0021] S3 下 Drying stage: Increase the dry bulb temperature to 65℃~67℃ and the wet bulb temperature to 40℃~41℃ at a heating rate of 1℃ / h, and bake at a stable temperature until all tobacco leaves in the room are completely dry.

[0022] Preferably, the specific operation of the medium-temperature slow baking process is as follows:

[0023] S1 中Yellowing stage: After ignition, raise the dry-bulb temperature to 32℃~33℃ at a rate of 1℃ / h, and the wet-bulb temperature to 32℃~33℃, maintaining a stable temperature for 2~3 hours to initiate the yellowing process of the tobacco leaves; then, raise the dry-bulb temperature to 35℃~36℃ at a rate of 1℃ / h, and the wet-bulb temperature to 34.5℃~35.5℃, maintaining a stable temperature for 3~5 hours, until the tobacco leaves have turned 10-20% yellow; then, raise the dry-bulb temperature to 38℃ at a rate of 1℃ / 2 hours, and the wet-bulb temperature to 3... Baking at a stable temperature of 6℃~37℃ for 20~30 hours until the tobacco leaves turn 60~70% yellow; then, increasing the dry-bulb temperature to 40℃ at a rate of 1℃ / 3 hours, stabilizing the wet-bulb temperature at 36℃~37℃, and baking at a stable temperature for 6~10 hours until the tobacco leaves turn more than 80% yellow; then, increasing the dry-bulb temperature to 42℃ at a rate of 1℃ / 4 hours, stabilizing the wet-bulb temperature at 36℃~37℃, and baking at a stable temperature for 6~10 hours until the tobacco leaves are yellow with green veins, slightly green at the base, and the main veins are fully softened;

[0024] S2 中 Color fixation period: Increase the dry bulb temperature to 44℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 4h, and bake at a stable temperature for 8~12h until the tobacco leaf tips are more than 6cm dry; then, increase the dry bulb temperature to 48℃ and the wet bulb temperature to 37.5℃~38.5℃ at a rate of 1℃ / 4h, and bake at a stable temperature until the tobacco leaves are more than 1 / 2 dry and the main veins are completely white; then, increase the dry bulb temperature to 53℃~54℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 2~3h, and bake at a stable temperature until all the tobacco leaves in the chamber are completely dry.

[0025] S3 中 Drying stage: Increase the dry bulb temperature to 60℃ and the wet bulb temperature to 40℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 4~6 hours; then, increase the dry bulb temperature to 66℃~67℃ and the wet bulb temperature to 40℃~42℃ at a heating rate of 1℃ / h, and bake at a stable temperature until all the tobacco leaves in the room are completely dry.

[0026] Preferably, the specific operation of the high-temperature slow baking process is as follows:

[0027] S1 上 Yellowing stage: After ignition, raise the dry bulb temperature to 38℃ at a rate of 1℃ / 2h, and the wet bulb temperature to 37.5℃. Maintain this temperature for 6-10h until the tobacco leaves turn 20-30% yellow. Then, raise the dry bulb temperature to 40℃ at a rate of 1℃ / 3h, and the wet bulb temperature to 39℃-40℃. Maintain this temperature for 6-10h until the tobacco leaves turn 40-50% yellow. Then, slowly lower the wet bulb temperature to 35.5℃-36.5℃ and maintain this temperature until the tobacco leaves turn 70-80% yellow and the leaves soften. Finally, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 3-4h, and maintain the wet bulb temperature at 36℃-37℃. Maintain this temperature until the tobacco leaves turn yellow with green veins and fully collapse.

[0028] S2 上Color fixation period: Increase the dry bulb temperature to 44℃ at a rate of 1℃ / 4~5h, and the wet bulb temperature to 37℃~37.5℃. Maintain this temperature for 10~15h until the tobacco leaf tips are dry to more than 10cm and some main veins turn from green to white. Then, increase the dry bulb temperature to 49℃ at a rate of 1℃ / 3~4h, and the wet bulb temperature to 38℃~39℃. Maintain this temperature for 1h until more than 2 / 3 of the tobacco leaves are dry and the main veins are completely white, shrunken, and more than 1 / 5 dry. Then, increase the dry bulb temperature to 54℃~55℃ at a rate of 1℃ / 2~3h, and the wet bulb temperature to 39℃. Maintain this temperature for 1h until all the tobacco leaves in the entire chamber are dry and more than 2 / 5 of the main veins are dry.

[0029] S3 上 Drying stage: Increase the dry bulb temperature to 60℃ and the wet bulb temperature to 40℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 3~5h; then increase the dry bulb temperature to 67℃ and the wet bulb temperature to 41℃~42℃ at a rate of 1℃ / h, and bake at a stable temperature until all the tobacco leaves in the room are completely dry.

[0030] The beneficial effects of this invention: This invention provides a systematic structural optimization and curing process specifically for the new flue-cured tobacco variety "Guiyan 20". Compared with the commonly used "three-stage curing" or dedicated curing processes for other varieties in the prior art, the improvements and beneficial effects of this invention are mainly reflected in:

[0031] 1. This invention establishes a complete technical system from the field to the curing barn through optimized tobacco plant structure, preservation of tobacco branches and stems, differentiated harvesting at appropriate maturity, classified tobacco weaving, rational loading into the curing barn, and segmented curing steps. This technical system improves the quality of tobacco leaves from the source and, through precise control of differentiated curing process parameters during the curing process, systematically and synergistically solves the interconnected quality defects of "Guiyan 20" tobacco, such as thin lower leaves, easy ash accumulation on upper leaves, and pale color of cured tobacco leaves caused by the large number of leaves.

[0032] 2. In this invention, steps S1 and S2 optimize the photosynthetic capacity of the lower leaves and the degree of leaf opening of the upper leaves by cleaning up ineffective leaves in batches and retaining the tobacco stems, respectively, laying the material foundation for curing high-quality tobacco leaves. Steps S3 to S5 ensure uniform quality of tobacco leaves in the same curing batch through refined harvesting, sorting, and curing management, which is conducive to the synchronous coordination of yellowing and dehydration of tobacco leaves during the curing process. Step S6 designs differentiated "three-stage curing" process parameters for the lower, middle, and upper tobacco leaves. These parameters are specifically optimized for the physiological and curing characteristics of different parts of "Guiyan 20" tobacco leaves (lower leaves have less dry matter and need to be cured quickly to preserve their quality, while upper leaves are prone to browning and need to be cured slowly to prevent ash buildup). These improvements promote the transformation and retention of substances inside the tobacco leaves, inhibit undesirable biochemical reactions (such as enzymatic browning), and ultimately significantly increase the proportion of orange-yellow tobacco and upper-middle-grade tobacco leaves after curing, while significantly reducing the proportion of green mixed tobacco and ash-covered tobacco, thereby effectively improving the average price of tobacco leaves and overall economic benefits.

[0033] 3. For the lower tobacco leaves, harvest them at physiological maturity; classify the fresh tobacco leaves of different parts into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature, and remove tobacco leaves that have no curing value; categorize and bundle the tobacco leaves into different poles, ensuring that the same leaves are of the same quality and that the bundles are sparse, with 130-160 leaves per pole; load the tobacco leaves into the same layer and of the same quality, placing the less mature leaves in the low-temperature layer and the more mature leaves in the high-temperature layer, with 280-320 poles loaded per curing barn. This helps reduce the respiration loss of the lower tobacco leaves in the field and during curing, promotes smooth ventilation and dehumidification in the curing barn, and ensures coordinated yellowing and drying of the lower tobacco leaves, thereby increasing the oil content of the lower tobacco leaves after curing and increasing the thickness of the tobacco leaves. To address the relatively insufficient dry matter accumulation and thin texture of the lower leaves of Guiyan 20 tobacco, a high-temperature rapid baking process is adopted, which involves "high-temperature yellowing (yellowing at dry-bulb temperatures of 37℃, 39℃, and 42℃) + medium-high humidity color fixing (wet-bulb temperature 0-0.5℃ higher than conventional baking during the color fixing period) + high-temperature drying (stable drying at dry-bulb temperatures of 65℃-67℃)". This process further reduces the consumption of respiration substrates in the field and during the baking process, promotes timely color fixing of tobacco leaves during baking, and increases the thickness and color depth of the tobacco leaves after baking, thereby improving the problem of its light color.

[0034] 4. For the middle-section tobacco leaves, harvesting is carried out at a mature stage. Fresh tobacco leaves from different parts are classified into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature. Leaves without curing value are removed. The leaves are then bundled into different sections, ensuring uniform quality within each section, with a moderate number of leaves per section (150-180 leaves). The leaves are then packed into layers of uniform quality, with lower-maturity leaves placed in the lower-temperature layer and higher-maturity leaves in the higher-temperature layer, with 300-340 sections packed per batch. Considering the relatively balanced and good quality of the middle-section leaves in Guiyan 20, a "slow heating" method is adopted (lowering the initial stable temperature for drying the dry balls to...). The medium-temperature slow-curing process, characterized by "heating rate of 1℃ / 3~4h at 32℃~33℃ and dry-bulb temperature of 38℃~48℃ + stable wet-bulb temperature for primary yellowing (dry-bulb temperature of 38℃~42℃ and stable wet-bulb temperature of 36℃~37℃) + medium-high humidity for color fixing (wet-bulb temperature during color fixing period is 0~0.5℃ higher than conventional curing)," promotes smooth ventilation and dehumidification in the curing room and ensures coordinated yellowing and drying of tobacco leaves in the same layer. It avoids problems such as excessively rapid heating or large fluctuations in temperature and humidity, leading to greening, ash accumulation, or uneven curing and light curing, thereby improving the appearance quality of the cured tobacco leaves.

[0035] 5. For the upper tobacco leaves, harvest them at full maturity to high maturity; classify the fresh tobacco leaves of different parts into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature, and remove tobacco leaves that have no curing value; categorize and bundle the tobacco leaves into different piles, ensuring that the same quality leaves are bundled densely, with 170-200 leaves per pile; load the tobacco leaves in the same layer, placing the less mature leaves in the low-temperature layer and the more mature leaves in the high-temperature layer, with 320-360 piles per batch; addressing the characteristics of insufficient leaf opening, easy ash accumulation, and pale color in the upper leaves of Guiyan 20, adopt a "slow heating (dry bulb temperature 38℃~49℃, heating rate 1℃ / 3~4h) + high temperature and high humidity sweating and yellowing (dry bulb temperature 38℃~40℃, wet bulb temperature 37.5℃~40℃) + high degree of dryness (dry bulb... The high-temperature slow-curing process involves drying the tobacco leaf tips to over 10cm at 44℃; drying more than 2 / 3 of the leaves at 49℃, with the main veins completely white and shrunken, and more than 1 / 5 dry; and drying the entire tobacco leaf chamber at 54℃~55℃, with more than 2 / 5 of the main veins dry. This process, along with medium-high humidity color fixing (the wet-bulb temperature during the color fixing period is 0~1℃ higher than conventional curing), utilizes a high-temperature, high-humidity process in the early stages to open the tobacco leaf stomata for moisture removal and promote yellowing and aging, thus increasing the looseness of the tobacco leaf structure after curing. The later stages involve a slow increase in temperature and control of a relatively high wet-bulb temperature, ensuring sufficient yellowing and dehydration while effectively inhibiting enzymatic browning, reducing the risk of ash buildup, and increasing the color and depth of the leaves, thereby improving the appearance quality of the cured tobacco. Detailed Implementation

[0036] 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.

[0037] Example 1: Experiment on the effects of tobacco plant structure optimization and maturity on the appearance quality of cured tobacco leaves

[0038] The experiment used the multi-leaf flue-cured tobacco variety Guiyan 20 as material, selecting fresh tobacco leaves from the 8th to 9th leaf position (from bottom to top, including the bottom leaves) to represent the lower tobacco leaf samples. The conventional structure-optimized production method was used as the control (CK), and the tobacco plant structure optimization method of this invention was used as the treatment (T).

[0039] Conventional structural optimization production method:

[0040] When topping, remove 2-3 bottom leaves and 4-5 lower leaves that have no potential baking value.

[0041] The method for optimizing tobacco plant structure in this invention is as follows:

[0042] Remove 2-3 bottom leaves 15-20 days before topping, remove 2-3 lower leaves 5-10 days before topping, and remove 1-2 lower leaves that have no potential baking value when topping.

[0043] Fresh tobacco leaf samples of different physiological and technological maturity were bundled into poles and placed in the middle layer of the same standard intensive curing barn. All samples were placed 10-11 poles away from the tobacco loading gate. The curing operation was carried out according to the three-stage curing process (GB / T 23219—2008), and the specific operation is as follows:

[0044] Yellowing stage: After ignition, slowly raise the temperature of the curing barn to 33℃, maintaining a wet-bulb temperature of 32℃. Once the leaf tips turn yellow, increase the dry-bulb temperature to 38℃ at a rate of 1℃ every 2 hours, extending the stable temperature curing time and controlling the wet-bulb temperature at 36℃. This ensures that about 80% of the tobacco leaves in the high-temperature layer of the curing barn 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 36℃, and extend the stable temperature curing time until the tobacco leaves reach a state of yellow leaves with slightly green veins (approximately 90% yellow), wilting and collapsing, with the main veins softening.

[0045] Color-fixing period: The dry-bulb temperature is first increased at an average rate of 1°C every 3 hours to 45°C and then maintained at a stable temperature for baking until the tips curl. Then, the temperature is increased at a rate of 1°C every 2 hours to 48°C, extending the baking time to allow the tobacco leaves to turn yellow and lose moisture to reach the small rolling stage. Finally, the temperature is increased at a rate of 1°C every 2 hours to 55°C and baked at a stable temperature until the leaves are dry. As the dry-bulb temperature rises, the wet-bulb temperature gradually increases and stabilizes at 39°C.

[0046] Drying period: Increase the temperature from 55℃ to 66℃ at a rate of 1℃ per hour 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℃, maintain the wet bulb temperature at 42℃.

[0047] After the curing process, the appearance quality of the tobacco leaf samples after curing under different treatments was measured, and the results are shown in Table 1.

[0048]

[0049] Note: "+" indicates that it is better than the control; the more "+" signs, the better the quality.

[0050] Table 1 shows that different tobacco plant structure optimizations and maturity treatments significantly affect the appearance quality of the lower tobacco leaves after curing. In terms of maturity, physiologically mature lower tobacco leaves exhibit better color, identity, oil content, and chroma than technologically matured leaves. There are no significant differences in maturity and leaf structure indices among different maturity treatments. Regarding tobacco plant structure optimization, the color, identity, oil content, and chroma of physiologically and technologically matured tobacco leaves obtained using the method of this invention are superior to the control. This indicates that the method of this invention is beneficial for improving the appearance quality of the lower tobacco leaves after curing, including identity, oil content, and color.

[0051] Example 2: Experiment on the effect of retaining tobacco fork stems on the length, width, and grade structure of cured tobacco leaves

[0052] The experiment used the multi-leaf flue-cured tobacco variety Guiyan 20 as material. The tobacco plant structure optimization was carried out according to the tobacco plant structure optimization method of the present invention in Example 1. Fresh tobacco leaves from the third leaf position from the top (from top to bottom) were selected to represent the upper tobacco leaf samples. The conventional topping method was used as the control (CK), and the method of retaining tobacco branches and stems of the present invention was used as the treatment (T).

[0053] Conventional topping method:

[0054] Remove tobacco branches and buds from the tobacco plant when it first flowers and after that.

[0055] The method of this invention preserves the tobacco fork stem:

[0056] After topping, select 1-2 tobacco branches at the first or second leaf position from the top. When they grow to 5-10cm, remove all leaves and the top growing point from the tobacco branches, leaving only the stem.

[0057] Samples of fully mature to highly mature upper tobacco leaves, treated with different methods, were bundled into poles and placed in the middle layer of different standard intensive curing barns, 5-6 poles away from the entrance of the loading chamber. The curing process was carried out according to the three-stage curing process of Example 1 (GB / T 23219—2008). After curing, the appearance quality of the cured tobacco leaf samples with different treatments was measured.

[0058]

[0059] Table 2 shows that retaining the tobacco fork stalk (T) treatment is beneficial for the opening of the upper leaves. After curing, the length and width of the upper leaves are significantly greater than those of the control (CK). Furthermore, the proportion of orange-yellow tobacco and high-grade tobacco after curing is significantly higher than that of CK, while the proportion of ash-covered tobacco is significantly lower than that of CK. This indicates that the method of the present invention, which retains the tobacco fork stalk (T) treatment, is beneficial for the opening of the upper leaves, reduces ash-covered upper leaves, and improves the quality of the cured tobacco leaves.

[0060] Example 3: Comparison Experiment of the Effects of the Baking Process of the Present Invention and the Conventional Baking Process

[0061] The experiment used the multi-leaf flue-cured tobacco variety Guiyan 20 as material. The tobacco plant structure optimization was implemented according to the conventional structure optimization production method in Example 1, and the topping method was implemented according to the conventional topping method in Example 2. The middle and lower leaves were harvested when they were technologically mature, and the upper leaves were harvested when fully mature. Fresh tobacco leaves from different parts were classified into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature, and leaves without curing value were removed. The leaves were bundled into different piles, with the same quality on each pile, and a moderate number of leaves from different parts bundled per pile (150-180 leaves per pile). The leaves were packed in the same layer with the same quality, with less mature leaves packed in the low-temperature layer and more mature leaves packed in the high-temperature layer. Each batch of tobacco leaves from different parts was packed into 330 piles. Using the three-stage curing process (GB / T 23219—2008) as the control (CK) and the curing process of this invention as the treatment (T), fresh tobacco leaves from the 8th, 16th, and 23rd leaf positions (from bottom to top) were selected to represent the lower, middle, and upper tobacco leaf samples. The tobacco leaf samples were placed in the middle layer of two standard dense curing barns, at a distance of 8 tobacco poles from the entrance of the loading chamber. After curing, the appearance quality and grade structure of the cured tobacco leaves were statistically analyzed.

[0062] The baking process of this invention:

[0063] The baking process for the lower leaves is as follows:

[0064] S1 下Yellowing stage: After ignition, raise the dry bulb temperature to 37℃ at a rate of 1℃ / h, and the wet bulb temperature to 36.5℃. Maintain this temperature for 8 hours until the tobacco leaves turn 30-40% yellow. Then, raise the dry bulb temperature to 39℃ at a rate of 1℃ / 2h, and the wet bulb temperature to 36℃-37℃. Maintain this temperature for 20 hours until the tobacco leaves turn 70-80% yellow and the leaves become soft. After that, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 2h, and the wet bulb temperature to 36℃-37℃. Maintain this temperature for 10 hours until the tobacco leaves turn yellow with green veins, the main veins soften, and the leaf tips and edges curl slightly.

[0065] S2 下 Color fixing period: Increase the dry bulb temperature to 44℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 3h, and bake at a stable temperature for 10h until the tip of the tobacco leaf is more than 3cm dry; then, increase the dry bulb temperature to 50℃ and the wet bulb temperature to 37.5℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 15h until more than 1 / 2 of the tobacco leaf is dry and the main vein is completely white; then, increase the dry bulb temperature to 54℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 2h, and bake at a stable temperature until all the tobacco leaves in the chamber are completely dry.

[0066] S3 下 Drying stage: Increase the dry bulb temperature to 67℃ and the wet bulb temperature to 40℃ at a heating rate of 1℃ / h, and bake at a stable temperature until all tobacco leaves in the room are completely dry.

[0067] The baking process for the middle leaves is as follows:

[0068] S1 中 Yellowing stage: After ignition, raise the dry bulb temperature to 32℃ at a rate of 1℃ / h, and the wet bulb temperature to 32℃, and maintain the temperature for 3 hours to initiate the yellowing process of the tobacco leaves; then, raise the dry bulb temperature to 35℃ at a rate of 1℃ / h, and the wet bulb temperature to 34.5℃, and maintain the temperature for 5 hours to achieve 10-20% yellowing of the tobacco leaves; then, raise the dry bulb temperature to 38℃ at a rate of 1℃ / 2h, and the wet bulb temperature to 36℃, and maintain the temperature for 25 hours to achieve 60-70% yellowing of the tobacco leaves; then, raise the dry bulb temperature to 40℃ at a rate of 1℃ / 3h, and maintain the wet bulb temperature to 36℃-37℃, and maintain the temperature for 10 hours to achieve over 80% yellowing of the tobacco leaves; finally, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 4h, and the wet bulb temperature to 36℃-37℃, and maintain the temperature for 8 hours to achieve yellow leaves with green veins, a slightly greenish base, and fully softened main veins;

[0069] S2 中Color fixation period: Increase the dry bulb temperature to 44℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 4h, and bake at a stable temperature for 12h until the tobacco leaf tips are more than 6cm dry; then, increase the dry bulb temperature to 48℃ and the wet bulb temperature to 37.5℃ at a rate of 1℃ / 4h, and bake at a stable temperature until the tobacco leaves are more than 1 / 2 dry and the main veins are completely white; then, increase the dry bulb temperature to 53℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 2h, and bake at a stable temperature until all the tobacco leaves in the chamber are completely dry.

[0070] S3 中 Drying stage: Increase the dry bulb temperature to 60℃ and the wet bulb temperature to 40℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 4 hours; then increase the dry bulb temperature to 66℃ and the wet bulb temperature to 41℃ at a heating rate of 1℃ / h, and bake at a stable temperature until all the tobacco leaves in the room are completely dry.

[0071] The baking process for the upper leaves is as follows:

[0072] S1 上 Yellowing stage: After ignition, raise the dry bulb temperature to 38℃ and the wet bulb temperature to 37.5℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 10h until the tobacco leaves turn 20-30% yellow; then, raise the dry bulb temperature to 40℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 3h, and bake at a stable temperature for 6h until the tobacco leaves turn 40-50% yellow; then, slowly lower the wet bulb temperature to 36.5℃ and bake at a stable temperature until the tobacco leaves turn 70-80% yellow and the leaves soften; then, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 3-4h, stabilize the wet bulb temperature at 36℃, and bake at a stable temperature until the tobacco leaves turn yellow with green veins and fully collapse.

[0073] S2 上 Color fixation period: Increase the dry bulb temperature to 44℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 4h, and bake at a stable temperature for 12h until the tobacco leaf tips are dry to more than 10cm and some main veins turn from green to white; then, increase the dry bulb temperature to 49℃ and the wet bulb temperature to 38℃ at a rate of 1℃ / 3h, and bake at a stable temperature until more than 2 / 3 of the tobacco leaves are dry, and the main veins are completely white, shrunken, and more than 1 / 5 dry; then, increase the dry bulb temperature to 54℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 3h, and bake at a stable temperature until all the tobacco leaves in the entire chamber are completely dry and more than 2 / 5 of the main veins are dry.

[0074] S3 上 Drying stage: Increase the dry bulb temperature to 60℃ and the wet bulb temperature to 40℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 5h; then increase the dry bulb temperature to 67℃ and the wet bulb temperature to 41℃ at a rate of 1℃ / h, and bake at a stable temperature until all the tobacco leaves in the room are completely dry.

[0075]

[0076] As shown in Table 3, compared with the control (CK), the color, oil content, and chroma of the tobacco leaves treated with method T of the present invention were all improved in different parts after curing; the differences in maturity and identity indicators were not significant, and the leaf structure of the upper leaves treated with method T was better. This indicates that the curing process of the present invention is generally beneficial to improving the appearance quality of the cured tobacco leaves.

[0077]

[0078] As shown in Table 4, compared with the control (CK), the proportion of orange-yellow tobacco and the proportion of upper- and middle-grade tobacco in different parts of the flue-cured tobacco leaves treated by the method of the present invention significantly increased, while the proportion of green and mixed tobacco and the proportion of ash-covered tobacco significantly decreased, and the average price significantly increased. This indicates that the curing process of the method of the present invention is beneficial to improving the grade structure of the flue-cured tobacco leaves.

[0079] Example 4:

[0080] The experiment used the multi-leaf flue-cured tobacco variety Guiyan 20 as the material, with conventional production methods as the control (CK) and the method of this invention as the treatment (T). Fresh tobacco leaves from the 8th, 16th, and 23rd leaf positions (from bottom to top) were selected to represent the lower, middle, and upper tobacco leaf samples. The tobacco leaf samples were placed in the middle layer of two standard dense curing barns, 8-10 tobacco poles away from the door of the loading chamber. After curing, the appearance quality and grade structure of the cured tobacco leaves were statistically analyzed.

[0081] Conventional production method:

[0082] 1. Tobacco plant structure optimization: The production method is the same as the conventional structure optimization method in Example 1;

[0083] 2. Ceiling method: Same as the conventional ceiling method in Example 2;

[0084] 3. Fresh tobacco harvesting: Harvesting is carried out according to the maturity characteristics of different parts of the tobacco leaves. The middle and lower leaves are harvested when they are technologically mature, and the upper leaves are harvested when they are fully mature.

[0085] 4. Sorting and arranging tobacco: Fresh tobacco leaves from different parts are classified into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature, and tobacco leaves with no curing value are removed; tobacco leaves are then sorted and arranged into sticks, with the same quality on the same stick, and the number of tobacco leaves from different parts arranged into sticks is moderate, with 150 to 180 pieces per stick.

[0086] 5. Reasonable loading of tobacco leaves: Load tobacco leaves of the same quality in the same layer, and load tobacco leaves with low maturity in the low temperature layer and tobacco leaves with high maturity in the high temperature layer; load 300-340 tobacco leaves from different parts of the tobacco per kiln.

[0087] 6. Baking: A three-stage baking process (GB / T 23219—2008) is adopted. For specific operation, please refer to Example 1.

[0088] Production method of this invention:

[0089] 1. Optimization of tobacco plant structure: The optimization method of tobacco plant structure of the present invention is the same as that in Example 1;

[0090] 2. Topping method: Same as the topping method of the present invention in Example 2;

[0091] 3. Fresh tobacco harvesting: Harvesting is carried out according to the maturity characteristics of different parts of the tobacco leaves: the lower leaves are harvested when they are physiologically mature, the middle leaves are harvested when they are technologically mature, and the upper leaves are harvested when they are fully mature to a high degree of maturity.

[0092] 4. Sorting and arranging tobacco: Fresh tobacco leaves from different parts are classified into four categories based on maturity: immature, physiologically mature, technologically mature, and overripe, and tobacco leaves without curing value are removed; tobacco leaves are then arranged into stalks according to their maturity, with the same quality on the same stalk, and the number of tobacco leaves from different parts arranged into stalks is moderate, with 130-160 leaves per stalk for lower leaves, 150-180 leaves per stalk for middle leaves, and 170-200 leaves per stalk for upper leaves;

[0093] 5. Reasonable loading of tobacco leaves: Load tobacco leaves of the same quality in the same layer, and load tobacco leaves with low maturity in the low temperature layer and tobacco leaves with high maturity in the high temperature layer; load 280-320 tobacco sticks per kiln for the lower leaves, 300-340 tobacco sticks per kiln for the middle leaves, and 320-360 tobacco sticks per kiln for the upper leaves.

[0094] 6. Baking: The baking method of the present invention is the same as that in Example 3.

[0095]

[0096] As shown in Table 5, compared with the control (CK), the color, oil content, and chroma of the flue-cured tobacco leaves treated with method T of the present invention were all improved in different parts; the differences in maturity and leaf structure indicators were not significant, but the upper leaves treated with T showed better maturity and leaf structure after curing; the identity indicators of the lower and upper leaves were better with treatment T. This indicates that the method of the present invention is generally beneficial to improving the appearance quality of the flue-cured tobacco leaves.

[0097]

[0098] As shown in Table 6, compared with the control (CK), the proportion of orange-yellow tobacco and the proportion of upper- and middle-grade tobacco in different parts of the flue-cured tobacco treated by the method of the present invention significantly increased, while the proportion of green and mixed tobacco and the proportion of ash-covered tobacco significantly decreased, and the average price significantly increased. This indicates that the method of the present invention is beneficial to improving the grade structure of flue-cured tobacco leaves.

[0099] 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 structural optimization and curing process for the leaves of the flue-cured tobacco variety Guiyan 20, characterized in that, Includes the following steps: S1. Optimization of tobacco plant structure: Remove 2-3 bottom leaves 15-20 days before topping, remove 2-3 lower leaves 5-10 days before topping, and remove 1-2 lower leaves with no potential curing value when topping; S2. Retain the stem of the tobacco branch: After topping, select 1-2 tobacco branches at the first or second leaf position from the top. When they grow to 5-10cm, remove all the leaves and the growing point at the top of the tobacco branch, leaving only the stem part. S3. Fresh tobacco harvesting: Harvesting is carried out according to the maturity characteristics of tobacco leaves in different parts: lower leaves are harvested when physiologically mature, middle leaves are harvested when technologically mature, and upper leaves are harvested when fully mature to high maturity. S4. Classification and arranging of tobacco: Fresh tobacco leaves from different parts are classified into four categories based on maturity: immature, physiologically mature, technologically mature, and over-mature, and tobacco leaves without curing value are removed; tobacco leaves are then arranged into stalks of the same type and quality, with 130-160 leaves per stalk for lower leaves, 150-180 leaves per stalk for middle leaves, and 170-200 leaves per stalk for upper leaves. S5. Reasonable loading of tobacco leaves: tobacco leaves of the same quality are loaded in the same layer. The tobacco leaves with low maturity are loaded in the low temperature layer and the tobacco leaves with high maturity are loaded in the high temperature layer. The lower leaves are loaded with 280-320 sticks of tobacco per kiln, the middle leaves are loaded with 300-340 sticks of tobacco per kiln, and the upper leaves are loaded with 320-360 sticks of tobacco per kiln. S6. Differentiated curing methods are adopted according to the part of the tobacco leaf: The lower tobacco leaves adopt a high-temperature fast curing process, with a dry-bulb temperature higher than that of conventional curing during the yellowing period, a wet-bulb temperature higher than that of conventional curing during the color-fixing period, and a dry-bulb temperature higher than that of conventional curing during the rib-drying period; The middle tobacco leaves adopt a medium-temperature slow curing process, with a lower starting dry-bulb temperature than that of conventional curing during the yellowing period, a reduced heating rate, and a stable wet-bulb temperature, and a wet-bulb temperature higher than that of conventional curing during the color-fixing period; The upper tobacco leaves adopt a high-temperature slow curing process, with a slow heating and increased wet-bulb temperature during the yellowing period, and a wet-bulb temperature higher than that of conventional curing during the color-fixing period, while also increasing the degree of dryness of the tobacco leaves.

2. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 1, characterized in that, The physiological maturity harvesting standard for the lower leaves is that the basic color of the leaf surface is green, the leaf tip and edge are obviously fading green, the overall yellowing degree of the tobacco leaf is 30-40%, more than 1 / 3 of the main veins are fading green and turning white, the leaf tip is drooping, and the pubescence is slightly lost.

3. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 1, characterized in that, The mature harvesting standard for the middle leaves is that the basic color of the leaf surface is yellowish-green, the leaf tip and edge turn yellow, the overall yellowing degree of the tobacco leaf is 60-70%, more than 2 / 3 of the main veins turn white, the leaf tip droops obviously, most of the hairs fall off, and light yellow mature spots appear.

4. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 1, characterized in that, The standard for harvesting the upper leaves to full maturity or high maturity is that the basic color of the leaf surface is yellow, the leaf tip and edge are obviously white, the overall yellowing degree of the tobacco leaf is more than 80%, the main veins are almost completely white, the leaf tip is obviously drooping, the hairs have almost all fallen off, and obvious yellowish-white maturity spots appear.

5. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 4, characterized in that, The upper leaves are harvested when they are fully mature and at a high degree of maturity. One or two top leaves that have no baking value are discarded.

6. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 1, characterized in that, The specific operation of the high-temperature rapid baking process is as follows: S1 下 Yellowing stage: After ignition, raise the dry bulb temperature to 37℃ and the wet bulb temperature to 36.5℃ at a rate of 1℃ / h, and bake at a stable temperature for 6~10h until the tobacco leaves turn 30-40% yellow; then, raise the dry bulb temperature to 39℃ and the wet bulb temperature to 36℃~37℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 15~20h until the tobacco leaves turn 70-80% yellow and the leaves soften; then, raise the dry bulb temperature to 42℃ and the wet bulb temperature to 36℃~37℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 10~15h until the tobacco leaves are yellow with green veins, the main veins soften, and the leaf tips and edges curl slightly. S2 下 Color fixing period: Increase the dry bulb temperature to 44℃~45℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 3h, and bake at a stable temperature for 6~10h until the tip of the tobacco leaf is more than 3cm dry; then, increase the dry bulb temperature to 48℃~50℃ and the wet bulb temperature to 37.5℃~38.5℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 10~15h until more than 1 / 2 of the tobacco leaf is dry and the main vein is completely white; then, increase the dry bulb temperature to 54℃~55℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 2h, and bake at a stable temperature until all the tobacco leaves in the chamber are completely dry. S3 下 Drying stage: Increase the dry bulb temperature to 65℃~67℃ and the wet bulb temperature to 40℃~41℃ at a heating rate of 1℃ / h, and bake at a stable temperature until all tobacco leaves in the room are completely dry.

7. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 1, characterized in that, The specific operation of the medium-temperature slow baking process is as follows: S1 中 Yellowing stage: After ignition, raise the dry-bulb temperature to 32℃~33℃ at a rate of 1℃ / h, and the wet-bulb temperature to 32℃~33℃, maintaining a stable temperature for 2~3 hours to initiate the yellowing process of the tobacco leaves; then, raise the dry-bulb temperature to 35℃~36℃ at a rate of 1℃ / h, and the wet-bulb temperature to 34.5℃~35.5℃, maintaining a stable temperature for 3~5 hours, until the tobacco leaves have turned 10-20% yellow; then, raise the dry-bulb temperature to 38℃ at a rate of 1℃ / 2 hours, and the wet-bulb temperature to 3... Baking at a stable temperature of 6℃~37℃ for 20~30 hours until the tobacco leaves turn 60~70% yellow; then, increasing the dry-bulb temperature to 40℃ at a rate of 1℃ / 3 hours, stabilizing the wet-bulb temperature at 36℃~37℃, and baking at a stable temperature for 6~10 hours until the tobacco leaves turn more than 80% yellow; then, increasing the dry-bulb temperature to 42℃ at a rate of 1℃ / 4 hours, stabilizing the wet-bulb temperature at 36℃~37℃, and baking at a stable temperature for 6~10 hours until the tobacco leaves are yellow with green veins, slightly green at the base, and the main veins are fully softened; S2 中 Color fixation period: Increase the dry bulb temperature to 44℃ and the wet bulb temperature to 37℃ at a rate of 1℃ / 4h, and bake at a stable temperature for 8~12h until the tobacco leaf tips are more than 6cm dry; then, increase the dry bulb temperature to 48℃ and the wet bulb temperature to 37.5℃~38.5℃ at a rate of 1℃ / 4h, and bake at a stable temperature until the tobacco leaves are more than 1 / 2 dry and the main veins are completely white; then, increase the dry bulb temperature to 53℃~54℃ and the wet bulb temperature to 39℃ at a rate of 1℃ / 2~3h, and bake at a stable temperature until all the tobacco leaves in the chamber are completely dry. S3 中 Drying stage: Increase the dry bulb temperature to 60℃ and the wet bulb temperature to 40℃ at a heating rate of 1℃ / h, and bake at a stable temperature for 4~6 hours; then increase the dry bulb temperature to 66℃~67℃ and the wet bulb temperature to 40℃~42℃ at a heating rate of 1℃ / h, and bake at a stable temperature until all the tobacco leaves in the room are completely dry.

8. The structural optimization and curing process of the Guiyan 20 flue-cured tobacco leaf according to claim 1, characterized in that, The specific operation of the high-temperature slow baking process is as follows: S1 上 Yellowing stage: After ignition, raise the dry bulb temperature to 38℃ at a rate of 1℃ / 2h, and the wet bulb temperature to 37.5℃. Maintain this temperature for 6-10h until the tobacco leaves turn 20-30% yellow. Then, raise the dry bulb temperature to 40℃ at a rate of 1℃ / 3h, and the wet bulb temperature to 39℃-40℃. Maintain this temperature for 6-10h until the tobacco leaves turn 40-50% yellow. Then, slowly lower the wet bulb temperature to 35.5℃-36.5℃ and maintain this temperature until the tobacco leaves turn 70-80% yellow and the leaves soften. Finally, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 3-4h, and maintain the wet bulb temperature at 36℃-37℃. Maintain this temperature until the tobacco leaves turn yellow with green veins and fully collapse. S2 上 Color fixation period: Increase the dry bulb temperature to 44℃ at a rate of 1℃ / 4~5h, and the wet bulb temperature to 37℃~37.5℃. Maintain this temperature for 10~15h until the tobacco leaf tips are dry to more than 10cm and some main veins turn from green to white. Then, increase the dry bulb temperature to 49℃ at a rate of 1℃ / 3~4h, and the wet bulb temperature to 38℃~39℃. Maintain this temperature for 1h until more than 2 / 3 of the tobacco leaves are dry and the main veins are completely white, shrunken, and more than 1 / 5 dry. Then, increase the dry bulb temperature to 54℃~55℃ at a rate of 1℃ / 2~3h, and the wet bulb temperature to 39℃. Maintain this temperature for 1h until all the tobacco leaves in the entire chamber are dry and more than 2 / 5 of the main veins are dry. S3 上 Drying stage: Increase the dry bulb temperature to 60℃ and the wet bulb temperature to 40℃ at a rate of 1℃ / 2h, and bake at a stable temperature for 3~5h; then increase the dry bulb temperature to 67℃ and the wet bulb temperature to 41℃~42℃ at a rate of 1℃ / h, and bake at a stable temperature until all the tobacco leaves in the room are completely dry.

Images