Method for cutting and baking upper tobacco leaves with stems

Abstract

The invention discloses a method for cutting and baking upper tobacco leaves with stems. The method comprises the steps of segmented stem cutting and harvesting, segmented stem splitting, reasonable rod binding, layered kang loading and precise baking. Accurate temperature control and humidity control curing processes of'one low, one slow, one long and one high ', 'one low, one slow, one equal, one long and one minute' and'one slow 'are adopted in the three key stages of the yellowing middle and later stage, the color fixing stage and the stem drying stage respectively, and layered color fixing is conducted on the tobacco leaves in the high-temperature layer, the middle-temperature layer and the low-temperature layer in the color fixing stage. According to the method, the problem that the ash hanging ratio and the stiffness ratio of the upper tobacco leaves are high is effectively solved, and the appearance quality, the grade structure, the sensory quality and the industrial usability of the baked upper tobacco leaves are remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for upper tobacco leaf stalk cutting and curing, belonging to the technical field of tobacco leaf curing. BACKGROUND

[0002] In recent years, with the adjustment of tobacco leaf procurement structure, the proportion of upper leaves in raw materials has exceeded 45%, becoming an important component of tobacco raw materials. However, the upper tobacco leaves generally have problems such as thick leaves, tight tissue structure, high dry matter accumulation, low water content, slow maturation and yellowing, etc., which lead to high proportion of gray and rigid tobacco leaves after curing, dark color, low proportion of superior tobacco, and uncoordinated chemical composition, etc., seriously affecting the quality and industrial usability.

[0003] The curing method is an important technical means to improve the curing quality of upper leaves. There are many methods for curing upper leaves in the prior art. For example, patent document (publication number: CN117643387A) discloses a curing method for upper tobacco leaves, which is to pack the tobacco leaves with stems into a kiln, then sequentially stabilize at 38-40℃ until 7-8% yellow, stabilize at 42℃ until 9-10% yellow, then fix color at 45-54℃ for 60-72h until dry piece wet stem, and finally dry stem at 60-68℃ for 40-48h until dry stem, so as to improve the appearance quality, sensory quality and chemical composition coordination of the cured tobacco leaves. Patent document (publication number: CN118436108A) discloses a one-time cutting and curing method and device for upper tobacco leaves, which is to hang by hooks, bind with twine, and place in layers according to leaf quality, combined with time-controlled fan and temperature and humidity, to realize staged curing and achieve the effect of labor saving and quality improvement. Patent document (publication number: CN118512024A) discloses a 4-6 piece one-time stalk cutting curing process for upper tobacco leaves, which adopts a "high-temperature fast exhaust method" to effectively improve the curing quality of upper tobacco leaves and increase the income of tobacco farmers. Patent document (publication number: CN103637392B) discloses a cutting and binding curing method and curing structure for upper tobacco leaves, which is to directly stack the bound 4-6 tobacco plants vertically on the curing house air distribution plate for curing, eliminating the need for hanging rods, improving the loading capacity and reducing costs. Patent document (publication number: CN110037328A) discloses a cutting and binding curing method and curing structure for upper tobacco leaves, which is to directly stack the cut and bound tobacco leaves in an inclined manner on the air distribution plate in a downflow type curing house for curing, which can improve the curing quality of upper tobacco leaves. Patent document (publication number: CN120436358A) discloses a one-time stalk curing method for upper tobacco leaves, which adjusts the temperature rising rate and stabilization time, relative humidity in the 5 stages of aroma brewing, aroma production, aroma enhancement, aroma increase and aroma fixation, to promote full yellowing and aroma formation of the tobacco leaves, and improve the overall quality of the upper tobacco leaves.

[0004] However, the prior art is mostly focused on the improvement of the one-time stalk cutting and tobacco loading method of the upper 4-6 leaves and the overall curing process, and still has the following shortcomings: the upper 4-6 leaves cut with stalks in one time are dried slowly in the curing process, the curing period is long, the curing cost is high, and the color fixing is difficult; most importantly, there is still a lack of a systematic solution integrating the segmented stalk cutting, segmented stalk splitting, reasonable pole binding, layered loading and supporting curing process. Therefore, it is of urgent significance to develop an upper tobacco stalk cutting method integrating the segmented stalk cutting, segmented stalk splitting, reasonable pole binding, layered loading and supporting curing process to solve the current production problems of the upper tobacco. SUMMARY

[0005] Based on the above, the present application provides an upper tobacco stalk cutting method, which can significantly improve the appearance quality of cured tobacco, increase the proportion of orange tobacco and high-grade tobacco, reduce the proportion of ash hanging tobacco and rigid tobacco, and improve the average price of tobacco, sensory quality and industrial usability, and can overcome the shortcomings of the prior art.

[0006] The upper tobacco stalk cutting method comprises the following steps: S1. Segmented stalk cutting: after the top 1-3 leaves in the upper tobacco enter the physiological maturity period and the remaining lower leaves enter the process maturity period, the upper tobacco is divided into two segments with the top physiological maturity period and the lower process maturity period as the dividing line and is cut; S2. Segmented stalk splitting: the stalks of the top physiological maturity period tobacco and the lower process maturity period tobacco are respectively split along the longitudinal direction, and the split stalks are retained on the longitudinal split stalks; S3. Reasonable pole binding: the split stalk tobacco of the physiological maturity period and the process maturity period is bound and loaded into the kiln, and 40-80 split stalk tobaccos are bound per pole; S4. Layered loading: the split stalk tobacco of the process maturity period is loaded in the high-temperature layer, and the split stalk tobacco of the physiological maturity period is loaded in the low-temperature layer, and the same layer and the same quality are required, and 280-320 poles are loaded per kiln, and the loading is required to be uniform and full, and the tobacco poles are closely arranged to ensure that there is no gap; S5. Precise curing: compared with the three-stage curing process "GB / T 23219-2008 Tobacco Curing Technical Regulations", the present application adopts "one low, one slow, one long, one high", "one low, one slow, one fixed, one long, one division" and "one slow" precise temperature and humidity control curing process in the three key stages of the yellowing middle and late period, the color fixing period and the dry stem period; The middle and late stage of the yellowing period is between 38-42℃ of dry ball temperature, and has "one low, one slow, one long, and one high": "one low" refers to reducing the wet ball temperature by 0.5-1.5℃ during this period; "one slow" refers to slowing down the temperature rising speed to 1℃ / 3-4.5h during this period; "one long" refers to extending the stable temperature baking time from 10-15h to 15-25h at 42℃ of dry ball temperature; and "one high" refers to increasing the drying degree of the tobacco leaves to 5-10cm of dried leaf tip at 42℃ of dry ball temperature; The color fixing period has "one low, one slow, one fixed, one long, and one divided": "one low" refers to reducing the wet ball temperature by 1-2℃ during the color fixing period; "one slow" refers to slowing down the temperature rising speed to 1℃ / 2-4.5h during the color fixing period; "one fixed" refers to increasing the dry ball temperature by 4℃ as a fixed temperature difference, and baking at three stable temperature points of 46℃, 50℃, and 54℃ in stages; "one long" refers to extending the stable temperature baking time by 6-10h at 46℃, 50℃, and 54℃ of dry ball temperature, respectively; and "one divided" refers to dividing the tobacco leaves in the color fixing period into high-temperature layer, medium-temperature layer, and low-temperature layer for color fixing. The dry muscle period has "one slow": refers to reducing the temperature rising speed from 1℃ / h to 1℃ / 2h during the dry muscle period.

[0007] The aforementioned tobacco leaf band stem cutting method is, the physiological maturity period of the tobacco leaf is characterized in that 70%-80% of the leaf surface is yellow, the main veins are basically white and bright, most of the branch veins are white and bright, the villi are basically shed, the leaf surface is obviously shriveled, the leaf tip and leaf edge are obviously yellow and white, and the leaf surface has mature patches and gloss.

[0008] The aforementioned tobacco leaf band stem cutting method is, the process maturity period of the tobacco leaf is characterized in that more than 85% of the leaf surface is yellow, the main veins are white and bright, most of the branch veins are white and bright, the villi are shed, the leaf surface is shriveled, the leaf tip and leaf edge are white and rolled down, and the leaf surface has obvious mature patches and strong gloss.

[0009] The aforementioned tobacco leaf band stem cutting method is, in the step S2 of segmenting the stem, the direction of the segmented stem is required to be controlled, and the segmented stem longitudinal line is required to avoid the position of the leaf blade to prevent the fresh tobacco leaf from being broken; and 1-3 pieces of tobacco leaves are reserved on the segmented stem of the segmented stem tobacco leaf.

[0010] The upper tobacco stalk cutting and curing method is characterized in that the yellowing period curing operation steps are as follows: after ignition, the dry ball temperature is raised to 32-36 DEG C at a temperature raising speed of 1 DEG C / h, the dry ball temperature difference is controlled to 0-1 DEG C, and the temperature is kept stable for 3-5 h until the tobacco leaves are 2 / 3-3 / 3 yellow; then the dry ball temperature is raised to 38 DEG C at a temperature raising speed of 1 DEG C / 2 h, the wet ball temperature is controlled to 35-36 DEG C, and the temperature is kept stable for 15-20 h until the tobacco leaves are 6 / 7-7 / 7 yellow, and more than 4 / 5 of the leaves are soft; then the dry ball temperature is raised to 40 DEG C at a temperature raising speed of 1 DEG C / 3-4 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 6-10 h until the tobacco leaves are 8 / 9-9 / 9 yellow, and the leaves are fully soft; then the dry ball temperature is raised to 42 DEG C at a temperature raising speed of 1 DEG C / 3.5-4.5 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 15-25 h until the tobacco leaves are dried by 5-10 cm at the leaf tip.

[0011] The upper tobacco stalk cutting and curing method is characterized in that the yellowing period curing operation steps are as follows: after ignition, the dry ball temperature is raised to 32-36 DEG C at a temperature raising speed of 1 DEG C / h, the dry ball temperature difference is controlled to 0-1 DEG C, and the temperature is kept stable for 3-5 h until the tobacco leaves are 2 / 3-3 / 3 yellow; then the dry ball temperature is raised to 38 DEG C at a temperature raising speed of 1 DEG C / 2 h, the wet ball temperature is controlled to 35-36 DEG C, and the temperature is kept stable for 15-20 h until the tobacco leaves are 6 / 7-7 / 7 yellow, and more than 4 / 5 of the leaves are soft; then the dry ball temperature is raised to 40 DEG C at a temperature raising speed of 1 DEG C / 3-4 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 6-10 h until the tobacco leaves are 8 / 9-9 / 9 yellow, and the leaves are fully soft; then the dry ball temperature is raised to 42 DEG C at a temperature raising speed of 1 DEG C / 3.5-4.5 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 15-25 h until the tobacco leaves are dried by 5-10 cm at the leaf tip.

[0012] The upper tobacco stalk cutting and curing method is characterized in that the yellowing period curing operation steps are as follows: after ignition, the dry ball temperature is raised to 32-36 DEG C at a temperature raising speed of 1 DEG C / h, the dry ball temperature difference is controlled to 0-1 DEG C, and the temperature is kept stable for 3-5 h until the tobacco leaves are 2 / 3-3 / 3 yellow; then the dry ball temperature is raised to 38 DEG C at a temperature raising speed of 1 DEG C / 2 h, the wet ball temperature is controlled to 35-36 DEG C, and the temperature is kept stable for 15-20 h until the tobacco leaves are 6 / 7-7 / 7 yellow, and more than 4 / 5 of the leaves are soft; then the dry ball temperature is raised to 40 DEG C at a temperature raising speed of 1 DEG C / 3-4 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 6-10 h until the tobacco leaves are 8 / 9-9 / 9 yellow, and the leaves are fully soft; then the dry ball temperature is raised to 42 DEG C at a temperature raising speed of 1 DEG C / 3.5-4.5 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 15-25 h until the tobacco leaves are dried by 5-10 cm at the leaf tip.

[0013] The upper tobacco stalk cutting and curing method is characterized in that the yellowing period curing operation steps are as follows: after ignition, the dry ball temperature is raised to 32-36 DEG C at a temperature raising speed of 1 DEG C / h, the dry ball temperature difference is controlled to 0-1 DEG C, and the temperature is kept stable for 3-5 h until the tobacco leaves are 2 / 3-3 / 3 yellow; then the dry ball temperature is raised to 38 DEG C at a temperature raising speed of 1 DEG C / 2 h, the wet ball temperature is controlled to 35-36 DEG C, and the temperature is kept stable for 15-20 h until the tobacco leaves are 6 / 7-7 / 7 yellow, and more than 4 / 5 of the leaves are soft; then the dry ball temperature is raised to 40 DEG C at a temperature raising speed of 1 DEG C / 3-4 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 6-10 h until the tobacco leaves are 8 / 9-9 / 9 yellow, and the leaves are fully soft; then the dry ball temperature is raised to 42 DEG C at a temperature raising speed of 1 DEG C / 3.5-4.5 h, the wet ball temperature is kept unchanged, and the temperature is kept stable for 15-25 h until the tobacco leaves are dried by 5-10 cm at the leaf tip.

[0014] Compared with the prior art, the upper tobacco stalk cutting and curing method has the advantages of: This invention utilizes segmented harvesting with stems and segmented stem splitting techniques to ensure that the split tobacco stems continuously provide the moisture needed for the tobacco leaves to turn yellow, while also ensuring timely dehydration and drying during the color-fixing period. This process guarantees a smooth transition between the yellowing and color-fixing stages, effectively reducing the proportion of ash-covered and stiff tobacco leaves, while significantly improving the appearance, grade structure, sensory quality, and industrial usability of the cured tobacco leaves. In contrast, harvesting and curing only the top 4-6 leaves at once, due to the lack of stem moisture supply, easily leads to premature termination of metabolism during the curing process, resulting in ash-covered and stiff tobacco leaves, thus reducing the grade and quality of the tobacco leaves. While harvesting and curing only the top 4-6 leaves with stems at once provides more moisture, it prolongs the curing time, increases curing energy consumption and costs, and also increases the difficulty of color fixing and the risks of curing operations.

[0015] By properly binding poles and layering the tobacco leaves, this invention ensures smooth ventilation and dehumidification in dense curing barns, effectively preventing excessive greening or yellowing of tobacco leaves, promoting coordinated and synchronous yellowing and dehydration processes, further reducing the proportion of ash and stiffness on the upper tobacco leaves, thereby improving the overall quality of the cured tobacco leaves.

[0016] During the mid-to-late yellowing stage, this invention employs a precise temperature and humidity control baking process of "low, slow, long, and high." Specifically, within the dry-bulb temperature range of 38-42℃, the wet-bulb temperature is reduced by 0.5-1.5℃, the heating rate is slowed to 1℃ / 3-4.5h, the stable temperature time at 42℃ is extended by 10-15h, and the degree of tobacco leaf drying is increased to 5-10cm at the leaf tip. This helps to coordinate the yellowing and water loss of the tobacco leaves, avoids the occurrence of leaf roasting and steaming, reduces the proportion of ash and stiffness in the upper leaves, and thus comprehensively improves the quality of the tobacco leaves.

[0017] During the color-fixing period, a precise temperature and humidity control process of "low temperature, slow temperature, fixed temperature, long temperature, and partial temperature control" is adopted. Specifically, this includes: lowering the wet-bulb temperature by 1-2℃, slowing the heating rate by 1℃ / 2-4.5h, and using a fixed temperature difference of 4℃ to raise the temperature in stages to three stable temperature points of 46℃, 50℃, and 54℃ for stable temperature baking, and extending the stable temperature baking time at each of these three temperature points by 6-10h. At the same time, layered color fixing is implemented for tobacco leaves in the high, medium, and low temperature layers to effectively avoid problems such as green veins, ash residue, stiffness, and uneven quality of tobacco leaves in different layers, ensuring that the yellowing and water loss of tobacco leaves are coordinated and timely color fixing is achieved, thereby improving the overall baking quality.

[0018] During the drying stage, a "slow" curing process is adopted, with the heating rate controlled at 1℃ / 2h. The slow heating allows the moisture inside the tobacco stems and stalks to be discharged gradually, avoiding excessive humidity in the curing barn due to rapid heating, which can cause the tobacco leaves to steam and turn red, thereby improving the appearance quality of the tobacco leaves.

[0019] Compared with existing curing technologies, the curing scheme provided by this invention significantly improves the appearance quality of the cured tobacco leaves. Specifically, the proportion of orange-yellow tobacco and high-grade tobacco is significantly increased, while the proportion of ash-covered tobacco and stiff tobacco is significantly reduced, thereby effectively improving the average price, sensory quality, and industrial usability of the tobacco leaves. Attached Figure Description

[0020] Figure 1 These are photos of tobacco leaves after the segmented splitting process of this invention; Figure 2 These are photos of tobacco leaves after curing using this invention; Figure 3 These are photos of tobacco leaves after a single harvest, with the top 4-6 leaves remaining. Figure 4 These are photos of tobacco leaves after a single harvest with 4-6 upper leaves; Figure 5 It is a photo of the upper 4-6 leaves being cut off and harvested along with the stem, and then hung on a pole; Figure 6 This is a photo of tobacco leaves after they have been harvested and cured, with the upper 4-6 leaves cut off along with the stem. Detailed Implementation

[0021] 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.

[0022] The experiment was conducted in Fuquan City and Bijie City, Guizhou Province, from 2024 to 2025. The tested flue-cured tobacco variety was Yunyan 87. The top 4-6 leaves were used as the research object, and the 16th leaf (from bottom to top) was selected as the analysis sample. The tested tobacco leaves were cultivated and managed according to the local standardized production standards for high-quality tobacco leaves. The tested curing barn was a standard dense curing barn with descending airflow. In this experiment, the top 4-6 leaves were harvested and cured at once as control 1, and the top 4-6 leaves were cut and cured with the stem intact at once as control 2. The method of cutting and curing the top tobacco leaves with the stem intact as described in this invention was used as the comparative treatment to carry out the comparative experiment.

[0023] (a) Control 1: Harvest and roast the upper 4-6 leaves at once. Mature harvesting: When the second leaf from the top down is physiologically mature, it is harvested and cured in one go. The fresh tobacco leaves are like... Figure 3 As shown; Fresh tobacco classification: tobacco leaves are classified into immature, physiologically mature, technologically mature, and over-mature categories, and tobacco leaves that have no curing value are removed; Reasonable tobacco peg weaving: Weaving pegs according to maturity, with each peg containing 160 tobacco leaves; Categorized loading: High-maturity tobacco leaves are loaded into the high-temperature layer, and low-maturity tobacco leaves are loaded into the low-temperature layer. Each load consists of 300 tobacco sticks. The loading should be uniform and full, with the tobacco sticks arranged closely together to ensure that there are no gaps. Baking: The operation shall be carried out in accordance with the three-stage baking process of "GB / T 23219—2008 Technical Specification for Tobacco Baking", and the specific operation is as follows: Yellowing stage: After loading the tobacco, slowly raise the temperature of the curing barn to 35℃, maintaining a wet-bulb temperature of 34℃, until the leaf tips turn yellow. Then, raise the dry-bulb temperature to 38℃ at a rate of 1℃ / 2 hours, controlling the wet-bulb temperature at 36.5℃, and maintain a stable temperature for curing until about 80% of the tobacco leaves in the high-temperature layer reach 70% to 80% yellowing, while the leaves soften (with a water loss of about 30%). Then, raise the temperature to 42℃, maintaining a wet-bulb temperature of 36.5℃, and maintain a stable temperature for curing until the tobacco leaves are yellow with slightly green veins, wilting and collapsing, and the midrib softens.

[0024] Color fixation period: Increase the dry bulb temperature to 45℃ at a rate of 1℃ / 2h, and bake at a stable temperature until the tips curl; then increase the temperature to 48℃ at a rate of 1℃ / 2h, and bake at a stable temperature until the tobacco veins turn yellow and the leaves curl into small tubes; then increase the temperature to 54℃ at a rate of 1℃ / 2h, and maintain the temperature for 10h until the leaves are dry. During this stage, the wet bulb temperature gradually increases and stabilizes at 39℃.

[0025] Drying stage: Increase the temperature from 54℃ to 67℃ at a rate of 1℃ / h, and maintain the temperature 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 41℃.

[0026] (ii) Control 2: Cut and roast the upper 4-6 leaves along with the stem in one go. Harvesting at maturity: Harvest the top 4-6 tobacco leaves with the stem attached in one go when they are fully mature; Properly tied poles: Tie 35 tobacco plants to each pole, such as... Figure 5 As shown; Properly load the tobacco into the kang (heated brick bed): Each kang should be loaded with 300 tobacco sticks, ensuring that the tobacco is evenly and fully loaded, and that the tobacco sticks are closely arranged to ensure that there are no gaps. S4. Baking: Baking is carried out using the single-bake process with 4-6 upper leaves and stems. The specific steps are as follows: Yellowing stage: After ignition, raise the dry bulb temperature to 35℃ at a rate of 1℃ / h, control the wet bulb temperature at 34℃, and bake at a stable temperature for 8 hours until the tobacco leaves sweat, soften, and the tips and edges of the leaves turn yellow; then, raise the dry bulb temperature to 38℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 37℃, and bake at a stable temperature for 18 hours until the tobacco leaves are 60-70% yellow and the leaves are soft; then, raise the dry bulb temperature to 40℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 36℃, and bake at a stable temperature for 10 hours until the tobacco leaves are 80% yellow and the leaves are soft; then, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 37℃, and bake at a stable temperature for 12 hours until the tobacco leaves are yellow with green veins. Color fixing period: Increase the dry bulb temperature to 45℃ at a rate of 1℃ / 3h, control the wet bulb temperature at 37℃, and bake at a stable temperature for 10h until the tips and edges of the tobacco leaves in the high-temperature layer curl; then, increase the dry bulb temperature to 48℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 38℃, and bake at a stable temperature for 15h until the tobacco leaves in the high-temperature layer are semi-dry, small curled, and the main veins turn white; then, increase the dry bulb temperature to 53℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 39℃, and bake at a stable temperature for 14h until the tobacco leaves in the low-temperature layer are completely dry. Drying stage: Raise the dry bulb temperature to 60℃ at a rate of 1℃ / h, maintain the wet bulb temperature at 40℃, and bake at a stable temperature for 5 hours; then, raise the dry bulb temperature to 67℃, maintain the wet bulb temperature at 41℃, and bake at a stable temperature until the tobacco leaves, stems and stalks are completely dry.

[0027] (III) Processing: The method of the present invention The method for cutting and curing the upper tobacco leaves with stems involves the following steps: S1. Segmented Harvesting with Stems: After the top 1-3 leaves of the upper tobacco leaf reach physiological maturity and the remaining lower leaves reach processing maturity, the upper tobacco leaf is divided into two segments and harvested, using the physiological maturity of the top segment and the processing maturity of the lower segment as the dividing line. The physiological maturity stage is characterized by 70%-80% yellowing of the leaf surface, the main vein turning mostly white and shiny, most of the secondary veins turning white and shiny, the pubescence largely falling off, the leaf surface noticeably wrinkled, and the leaf tips and edges clearly yellowing and whitening, with mature patches and a glossy appearance. The processing maturity stage is characterized by over 85% yellowing of the leaf surface, the main vein turning white and shiny, the secondary veins mostly turning white and shiny, the pubescence falling off, the leaf surface wrinkled, the leaf tips and edges whitening and curling downwards, and the leaf surface having obvious mature patches and a strong glossy appearance.

[0028] S2. Segmented stem splitting: The stems of the top physiologically mature tobacco leaves and the lower technologically mature tobacco leaves are split longitudinally, and tobacco leaves are retained on the longitudinally split stems to form split stem tobacco leaves; S3. Properly binding the poles: Bind the split tobacco leaves at the physiological maturity stage and the technological maturity stage separately to the drying pit, with 40 to 80 split tobacco leaves bound to each pole; S4. Layered loading: The tobacco leaves of the mature stage of the process are loaded into the high temperature layer, and the tobacco leaves of the physiological maturity stage are loaded into the low temperature layer. The same layer and the same quality are used. Each load contains 280 to 320 tobacco sticks. The loading should be uniform and full, and the tobacco sticks should be closely arranged to ensure that there are no gaps. S5. Precision baking: Compared with the three-stage baking process "GB / T 23219—2008 Technical Specification for Curing Tobacco", this invention adopts a precise temperature and humidity control baking process of "one low, one slow, one long, one high", "one low, one slow, one long, one segment", and "one slow" in the three key stages of yellowing, color fixing, and drying. The middle and late stages of the yellowing period are characterized by a dry-bulb temperature between 38 and 42°C, and are characterized by "one low, one slow, one long, and one high": "one low" refers to reducing the wet-bulb temperature by 0.5 to 1.5°C during this period; "one slow" refers to slowing down the heating rate by 1°C / 3 to 4.5 hours during this period; "one long" refers to extending the stable temperature baking time from 10 to 15 hours to 15 to 25 hours at a dry-bulb temperature of 42°C; and "one high" refers to increasing the degree of tobacco leaf drying at a dry-bulb temperature of 42°C until the leaf tip is 5 to 10 cm dry. The color-fixing period is defined as "one low, one slow, one fixed, one long, and one segment": "One low" refers to lowering the wet-bulb temperature by 1-2℃ during the color-fixing period; "one slow" refers to slowing down the heating rate during the color-fixing period by 1℃ / 2-4.5h; "one fixed" refers to raising the dry-bulb temperature at a fixed 4℃ difference, and then gradually increasing it to three stable temperature points of 46℃, 50℃, and 54℃ for stable baking; "one long" refers to extending the stable baking time at 46℃, 50℃, and 54℃ by 6-10h respectively; and "one segment" refers to stratifying the tobacco leaves in the high-temperature, medium-temperature, and low-temperature layers of the tobacco loading chamber during the color-fixing period. The "slow" drying period refers to reducing the heating rate during the drying period from 1℃ / h to 1℃ / 2h.

[0029] The specific steps are as follows: Because the maturity of tobacco leaves at different leaf positions cannot be completely uniform, the leaves are harvested with the stem attached when the second to last leaf of more than 90% of the tobacco plants in the field is close to physiological maturity. That is, the second to last leaf from the top is 70% to 80% yellow, the main vein is basically white and shiny, most of the branch veins are white and shiny, the pubescence has basically fallen off, the leaf surface is obviously wrinkled, the leaf tip and edge are obviously yellow and white, and the leaf surface has mature patches and a glossy appearance.

[0030] Use a machete or sickle to cut the stem with 4-6 upper tobacco leaves in two stages: the top section with 1-3 leaves (physiological maturity) and the bottom section with 2-3 leaves (processing maturity). Alternatively, cut the stem with 4-6 upper tobacco leaves as a whole, transport it back to the curing barn, and then cut it at the boundary between the top and bottom sections to separate them. Then, use a machete to split the stem of the top physiologically mature tobacco leaves and the bottom process-mature tobacco leaves longitudinally. When splitting longitudinally, control the direction of the split, and avoid the leaf attachment point to prevent breakage of the fresh tobacco leaves. Leave 1-3 tobacco leaves on the split stem. Figure 1 As shown.

[0031] Separately tie the physiologically mature and technologically mature tobacco leaves to poles for loading into the kiln, with 60 tobacco leaves tied to each pole. The technologically mature tobacco leaves are loaded into the high-temperature layer, while the physiologically mature tobacco leaves are loaded into the low-temperature layer. The leaves are of the same quality in the same layer. Each kiln is loaded with 300 poles. The loading should be uniform and full, with the tobacco poles arranged closely together to ensure that there are no gaps.

[0032] After loading the tobacco, set the baking parameters as follows: Yellowing stage: After ignition, raise the dry bulb temperature to 35℃ at a rate of 1℃ / h, control the dry bulb-wet bulb temperature difference at 34℃, and bake at a stable temperature for 5 hours until the tobacco leaves turn 20-30% yellow; then, raise the dry bulb temperature to 38℃ at a rate of 1℃ / 2h, control the wet bulb temperature at 36℃, and bake at a stable temperature for 20 hours until the tobacco leaves turn 60-70% yellow and more than 4 / 5 of the leaves soften; then, raise the dry bulb temperature to 40℃ at a rate of 1℃ / 3h, control the wet bulb temperature, and bake at a stable temperature for 10 hours until the tobacco leaves turn 80-90% yellow and the leaves are fully softened; then, raise the dry bulb temperature to 42℃ at a rate of 1℃ / 4h, control the wet bulb temperature, and bake at a stable temperature for 20 hours until the tobacco leaf tips are 5-10cm dry. Color-fixing period: The dry-bulb temperature is increased to 46℃ at a rate of 1℃ / 4.5h, while the wet-bulb temperature is controlled at 36℃. The leaves are then baked at a stable temperature for 20h until more than 2 / 3 of the high-temperature layer tobacco leaves are dry and some main veins have turned from green to white. After that, the dry-bulb temperature is increased to 50℃ at a rate of 1℃ / 3.5h, while the wet-bulb temperature is controlled at 37.5℃. The leaves are then baked at a stable temperature for 20h until more than 2 / 3 of the medium-temperature layer tobacco leaves are dry and the main veins are completely white. After that, the dry-bulb temperature is increased to 54℃ at a rate of 1℃ / 2.5h, while the wet-bulb temperature is controlled at 38℃. The leaves are then baked at a stable temperature for 18h until the low-temperature layer tobacco leaves are completely dry. During the color-fixing period, the high, medium, and low-temperature layer tobacco leaves are color-fixed in layers to reduce the proportion of ash and stiffness in the upper tobacco leaves, thereby improving the quality and usability of the tobacco leaves.

[0033] Drying stage: Raise the dry bulb temperature to 60℃ at a rate of 1℃ / 2h, maintain the wet bulb temperature at 40℃, and bake at a stable temperature for 8h; then, raise the dry bulb temperature to 67℃ at the same rate, maintain the wet bulb temperature at 41℃, and bake at a stable temperature until the entire tobacco leaf, tobacco stem and stalk are completely dry.

[0034] Using controls 1 and 2 as controls, and the method of this invention as the treatment, tobacco leaves at the 16th leaf position were selected as samples. Fresh tobacco leaf samples from controls 1, 2, and the treatment group were placed in the middle layer of three standard intensive curing barns, at a distance of 5 tobacco poles from the entrance of the loading chamber. The curing time and cost for each treatment were statistically analyzed. After curing, the appearance quality and grade structure of the cured tobacco leaves (proportion of orange-yellow tobacco, proportion of high-grade tobacco, proportion of ash-covered tobacco, proportion of stiff tobacco leaves, and average price) were evaluated. Sensory quality evaluation was conducted on B2F grade samples, and the comparison results are as follows: Table 1. Effects of different treatments on the appearance quality after baking As shown in Table 1, compared with Control 1, the upper tobacco leaves roasted using the method of the present invention have a deeper orange-yellow and lemon-yellow color, better maturity, looser texture, medium to slightly thicker body, increased oil content, and enhanced color. Compared with Control 2, the upper tobacco leaves treated by the method of the present invention show a slight increase in oil content and color, while other indicators are not significantly different. Overall, the tobacco leaves roasted using the method of the present invention have a superior appearance quality.

[0035] Table 2. Effects of different treatments on the grade structure of cured tobacco leaves Table 2 shows that, compared with Control 1, the upper tobacco leaves produced using the method of this invention and Control 2 showed significantly improved proportions of orange-yellow tobacco, high-grade tobacco, and average price, while significantly reduced proportions of ash-covered and stiff tobacco leaves. Compared with Control 2, the method of this invention did not show significant differences in the proportions of orange-yellow tobacco, stiff tobacco leaves, and average price, but the proportion of high-grade tobacco was higher, and the proportion of ash-covered tobacco was significantly reduced. In summary, the method of this invention helps to improve the grade structure of cured tobacco leaves.

[0036] Table 3. Effects of different treatments on baking time and baking cost Note: Baking time refers to the total time from ignition to the end of baking; the price of biomass pellet fuel is 1.00 yuan / kg, the price of electricity is 0.46 yuan / kWh, and the labor cost is 100 yuan / labor; the baking cost is the sum of the biomass fuel, electricity, and labor costs consumed by a single baking room.

[0037] As shown in Table 3, compared with Control 1, the baking time of the method of the present invention and Control 2 are both extended, and the baking cost increases accordingly; however, compared with Control 2, the baking time of the method of the present invention is significantly shortened, and the baking cost is also significantly reduced.

[0038] Table 4. Effects of different treatments on the sensory quality and industrial usability of flue-cured tobacco leaves. Note: The evaluation was conducted by 7 experts according to the Sensory Evaluation Method for Tobacco and Tobacco Products (YC / T 138-1998). The evaluation covered aspects such as aroma quality, aroma intensity, off-flavors, irritation, aftertaste, combustibility, smoke smoothness, taste, and ash content. The maximum score for aroma quality and off-flavor intensity was 18 points; for aroma intensity and irritation, it was 12 points; for aftertaste and taste, it was 10 points; for smoke smoothness and combustibility, it was 8 points each; and for ash content, it was 4 points. The total score was 100 points. A higher score indicates better tobacco curing quality. Industrial usability evaluation was divided into five levels: A (Good), B (Good), C (Average), and D (Poor). Formula compatibility evaluation was divided into five levels: Category I, Category II, Category III, Category IV, and Category V.

[0039] As shown in Table 4, compared with Control 1, both the method of the present invention and Control 2 significantly improved the sensory evaluation quality, industrial usability and formulation suitability of the upper tobacco leaves; the method of the present invention and Control 2 did not differ significantly in the above indicators, but the method of the present invention was slightly better than Control 2 in terms of industrial usability.

[0040] The embodiments described above are merely illustrative of implementation methods 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 cutting and roasting upper tobacco leaves with stems, characterized in that, Includes the following steps: S1. Segmented harvesting with stems: After the top 1-3 leaves of the upper tobacco leaves have entered the physiological maturity stage and the remaining lower tobacco leaves have entered the process maturity stage, the upper tobacco leaves are divided into two segments and harvested, with the physiological maturity stage of the top segment and the process maturity stage of the lower segment as the dividing line. S2. Segmented stem splitting: The stems of the top physiologically mature tobacco leaves and the lower technologically mature tobacco leaves are split longitudinally, and tobacco leaves are retained on the longitudinally split stems to form split stem tobacco leaves; S3. Properly binding the poles: Bind the split tobacco leaves at the physiological maturity stage and the technological maturity stage separately to the drying pit, with 40 to 80 split tobacco leaves bound to each pole; S4. Layered loading: The tobacco leaves of the mature stage of the process are loaded into the high temperature layer, and the tobacco leaves of the physiological maturity stage are loaded into the low temperature layer. The same layer and the same quality are used. Each load contains 280 to 320 tobacco sticks. The loading should be uniform and full, and the tobacco sticks should be closely arranged to ensure that there are no gaps. S5. Precision baking: Compared with the three-stage baking process "GB / T 23219—2008 Technical Specification for Curing Tobacco", the precise temperature and humidity control baking process is adopted in the three key stages of yellowing, color fixing and drying, respectively: "one low, one slow, one long and one high", "one low, one slow, one fixed, one long and one segmented" and "one slow". The middle and late stages of the yellowing period are characterized by a dry-bulb temperature between 38 and 42°C, and are characterized by "one low, one slow, one long, and one high": "one low" refers to reducing the wet-bulb temperature by 0.5 to 1.5°C during this period; "one slow" refers to slowing down the heating rate by 1°C / 3 to 4.5 hours during this period; "one long" refers to extending the stable temperature baking time from 10 to 15 hours to 15 to 25 hours at a dry-bulb temperature of 42°C; and "one high" refers to increasing the degree of tobacco leaf drying at a dry-bulb temperature of 42°C until the leaf tip is 5 to 10 cm dry. The color-fixing period is described as "one low, one slow, one fixed, one long, one segment": "One low" refers to lowering the wet-bulb temperature by 1-2℃ during the color-fixing period; "one slow" refers to slowing down the heating rate during the color-fixing period by 1℃ / 2-4.5h; "one fixed" refers to raising the dry-bulb temperature at a fixed 4℃ difference, in stages to three stable temperature points of 46℃, 50℃, and 54℃ for baking; "one long" refers to extending the stable baking time at dry-bulb temperatures of 46℃, 50℃, and 54℃ by 6-10h respectively; and "one segment" refers to color-fixing the tobacco leaves in layers of the high-temperature, medium-temperature, and low-temperature layers in the tobacco loading chamber during the color-fixing period. The "slow" drying period refers to reducing the heating rate during the drying period from 1℃ / h to 1℃ / 2h.

2. The method for cutting and roasting upper tobacco leaves with stems according to claim 1, characterized in that: The physiological maturity stage of tobacco leaves is characterized by 70% to 80% yellowing of the leaf surface, the main vein turning white and shiny, most of the branch veins turning white and shiny, the pubescence basically falling off, the leaf surface becoming noticeably wrinkled, the leaf tip and edge turning noticeably yellow and white, and the leaf surface having mature patches and a glossy appearance.

3. The method for cutting and roasting upper tobacco leaves with stems according to claim 2, characterized in that: The mature stage of the tobacco leaves is characterized by more than 85% yellowing of the leaf surface, the main vein turning white and shiny, the lateral veins basically turning white and shiny, the pubescence falling off, the leaf surface wrinkling, the leaf tip and edge turning white and curling downwards, and the leaf surface having obvious mature patches and strong luster.

4. The method for cutting and roasting upper tobacco leaves with stems according to claim 3, characterized in that, In step S2, when splitting the stems, it is necessary to control the direction of the splitting. The longitudinal line of the splitting should avoid the position where the leaves grow to prevent the fresh tobacco leaves from breaking.

5. The method for cutting and roasting upper tobacco leaves with stems according to claim 4, characterized in that, The yellowing stage baking operation steps are as follows: After ignition, raise the dry bulb temperature to 32~36℃ at a heating rate of 1℃ / h, control the dry bulb-wet bulb temperature difference to 0~1℃, and bake at a stable temperature for 3~5 hours until the tobacco leaves turn 2~30% yellow; then, raise the dry bulb temperature to 38℃ at a heating rate of 1℃ / 2h, control the wet bulb temperature to 35~36℃, and bake at a stable temperature for 15~20 hours until the tobacco leaves turn 6~70% yellow and more than 4 / 5 of the leaves soften; then, raise the dry bulb temperature to 40℃ at a heating rate of 1℃ / 3~4h, control the wet bulb temperature to remain constant, and bake at a stable temperature for 6~10 hours until the tobacco leaves turn 8~90% yellow and the leaves are fully softened; then, raise the dry bulb temperature to 42℃ at a heating rate of 1℃ / 3.5~4.5h, control the wet bulb temperature to remain constant, and bake at a stable temperature for 15~25 hours until the tobacco leaf tips are 5~10cm dry.

6. The method for cutting and roasting upper tobacco leaves with stems according to claim 5, characterized in that, The color-fixing baking operation steps are as follows: Raise the dry-bulb temperature to 46℃ at a rate of 1℃ / 3.5~4.5h, control the wet-bulb temperature at 35~36℃, and bake at a stable temperature for 15~20h until more than 2 / 3 of the tobacco leaves in the high-temperature layer are dry and some main veins turn from green to white; then, raise the dry-bulb temperature to 50℃ at a rate of 1℃ / 3~4h, control the wet-bulb temperature at 37~38℃, and bake at a stable temperature for 18~25h until more than 2 / 3 of the tobacco leaves in the medium-temperature layer are dry and the main veins are completely white; then, raise the dry-bulb temperature to 54℃ at a rate of 1℃ / 2~3h, control the wet-bulb temperature at 38℃, and bake at a stable temperature for 16~20h until the tobacco leaves in the low-temperature layer are completely dry.

7. The method for cutting and roasting upper tobacco leaves with stems according to claim 6, characterized in that, The drying and baking process is as follows: the dry bulb temperature is raised to 60°C at a rate of 1°C / 2h, the wet bulb temperature is maintained at 40~41°C, and the temperature is kept stable for 6~8h; then, the dry bulb temperature is raised to 66~67°C at the same rate, the wet bulb temperature is maintained at 41~42°C, and the temperature is kept stable until the tobacco leaves, stems and stalks are completely dry.

8. The method for cutting and roasting upper tobacco leaves with stems according to claim 7, characterized in that: During the color-fixing period, the tobacco leaves in the high, medium and low temperature layers are color-fixed in layers to reduce the proportion of ash and stiffness in the upper tobacco leaves, thereby improving the quality and usability of the tobacco leaves.

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