Method for baking upper tobacco leaves with stems in segmented mode

Abstract

The invention discloses a method for baking upper tobacco leaves with stems in a segmented mode, and belongs to the technical field of tobacco leaf baking. The method for baking the upper tobacco leaves with the stems in the segmented mode comprises the following steps that firstly, mature upper tobacco leaves are selected and then obliquely cut, and the tobacco leaves with the stems are obtained; 2, the obtained tobacco leaves with stems are classified, woven into rods and loaded, and tobacco leaves to be treated are obtained; 3, the tobacco leaves to be treated are baked, after baking is finished, fire stopping, cooling, natural moisture regaining and tobacco unloading are conducted, and baked tobacco leaves are obtained. According to the flue-cured tobacco prepared by the method, the appearance quality, the internal chemical components, the physical characteristics and the process stability are comprehensively improved.

Description

Technical Field

[0001] This invention belongs to the field of tobacco curing technology, specifically relating to a curing method for segmented tobacco leaves with stems. Background Technology

[0002] The traditional "harvest one leaf at a time" method of harvesting and curing has significant limitations when processing upper tobacco leaves. Due to their long growth cycle and the influence of ample sunlight and good ventilation, upper tobacco leaves have dense tissues, a thick waxy layer, and a high accumulation of dry matter. When harvesting and curing single leaves, uneven moisture loss often leads to difficulties in yellowing and color fixation, resulting in a higher proportion of green-veined, gray-colored, and mixed-color tobacco, severely impacting the industrial usability and economic value of the tobacco. To overcome this bottleneck, a segmented curing method with stems for upper tobacco leaves has emerged. This method involves harvesting fully mature upper tobacco leaves with stems, utilizing the vascular tissue of the stems to maintain the moisture balance of the leaves and promote the transformation of internal substances. During curing, the leaves yellow more evenly and color fixation is more thorough, significantly reducing the proportion of mixed-color tobacco. Simultaneously, it enhances the oil content and aroma of the leaves, improving both their appearance and internal quality, providing an effective technical path to improve the curing efficiency and industrial usability of upper tobacco leaves.

[0003] Patent CN117281280A discloses a simplified method for harvesting and curing single tobacco leaves with stems from the upper part of the flue-cured tobacco plant, including the following steps: S1, Harvesting: When the upper tobacco leaves reach maturity, cut the tobacco leaves and stems one by one from the tobacco plant, keeping each tobacco leaf with 1-2cm of the lower stem at the bottom; S2, Tying / Hanging: Tie / hang the tobacco leaves with short stems on both sides of the woven tobacco poles using a figure-eight wrapping method with rope, and place the tied / hanged tobacco leaves in a cool place; S3, Loading: Transfer all the tied / hanged woven tobacco poles to the curing barn and arrange them in an orderly manner according to a certain arrangement; S4, Curing: Curing is carried out using a high-humidity yellowing and medium-humidity withering and color fixing curing process. This application employs a single-leaf harvesting and curing method with 1-2cm stems. Compared to traditional techniques, this significantly reduces the harvesting, handling, and drying of stems, thereby lowering labor intensity, shortening curing time, and minimizing the loss of aroma compounds due to prolonged drying periods and high temperatures, thus improving curing quality. While the aforementioned patent's simplified single-leaf harvesting and curing method with stems for upper flue-cured tobacco leaves is highly effective in reducing labor intensity, shortening curing time, and minimizing aroma compound loss, it still has certain shortcomings in practical application. The main problem is that retaining only 1-2cm short stems makes the leaves prone to falling off during binding / hanging and handling, resulting in losses. Furthermore, the short stems have limited capacity to regulate the transport of moisture and nutrients, leading to uneven moisture loss during curing and potential yellowing or inconsistent color fixation in some areas, affecting the overall curing quality. These shortcomings limit the further optimization and promotion of this method. Summary of the Invention

[0004] The object of the present invention is to provide a baking method for upper tobacco leaves with stems in segments, so as to solve the technical problem of poor tobacco leaf baking quality in the prior art.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a baking method for upper tobacco leaves with stems in segments, including the following steps: Step 1: Select mature upper tobacco leaves, and then perform oblique cutting to obtain tobacco leaves with stems; Step 2: Classify the obtained tobacco leaves with stems, thread them onto poles, and load the poles into the tobacco barn to obtain tobacco leaves to be processed; Step 3: Bake the tobacco leaves to be processed (using a natural gas tobacco barn), after the baking is completed, stop firing, reduce the temperature, naturally rehumidify, and unload the tobacco leaves to obtain baked tobacco leaves.

[0006] Preferably, in Step 1, 4-6 upper tobacco leaves are selected, the oblique cutting distance from the lowest leaf position is 2-4 cm, and the angle between the knife and the stem is 30-45°.

[0007] Preferably, in Step 2, the tobacco leaves with stems are classified according to the leaf size, thickness and maturity, 30-35 tobacco plants are threaded onto each pole with a length of 1.4-1.5 m, the leaves evenly span the pole, and are arranged in a "pin" shape in a staggered manner, ensuring uniformity between the upper and lower layers and consistency within the same layer.

[0008] Preferably, in Step 3, during the baking process, it is divided into three stages. The first stage is the yellowing stage, the second stage is the color-fixing stage, and the third stage is the stem-drying stage.

[0009] Preferably, the treatment process in the yellowing stage is as follows: close the fan and all ventilation openings, ignite, increase the dry-bulb temperature to 36-38°C at a heating rate of 1°C / h, keep the wet-bulb temperature at 35-37°C, and maintain for 24-36 h until 80% of the leaves turn yellow, the tobacco leaves become soft and collapse, and the connection between the tobacco stem and the leaves begins to turn yellow and become soft.

[0010] Preferably, the treatment process in the color-fixing stage is as follows: increase the dry-bulb temperature from 38°C to 42-43°C at a temperature rate of 2-3°C / h, keep the wet-bulb temperature at 36-37°C, and maintain the temperature for 10-15 h until the tobacco leaves and stems turn completely yellow, the tips of the leaves are hooked and the edges are curled. When the tobacco leaves turn completely yellow, increase the dry-bulb temperature from 43°C to 48°C at a heating rate of 1-2°C / h, reduce the wet-bulb temperature to 37-38°C, and maintain the temperature at 46-48°C for more than 12 h until the tobacco leaves are in small rolls. Then continue to increase the dry-bulb temperature to 54-55°C, keep the wet-bulb temperature stable at 38-39°C, and maintain the temperature until the pressed slices are completely dry.

[0011] Preferably, the drying process is as follows: the dry bulb temperature is increased to 68°C at a rate of 1°C / h, not exceeding 70°C, the wet bulb temperature is 40-42°C, and the temperature is stabilized at 68°C until all main veins and tobacco stems are completely dry.

[0012] Preferably, in step three, when the dry bulb temperature drops to a level not much different from the ambient temperature, the tobacco loading door and air inlet are opened in the early morning or evening when the air humidity is high, allowing the tobacco leaves to naturally rehydrate until the tobacco leaves and tobacco fibers absorb water and become soft. When the tobacco leaves are resilient and not easily broken when picked up, the tobacco can be unloaded.

[0013] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are: The method of this invention for curing tobacco leaves achieves a comprehensive improvement in appearance quality, internal chemical composition, physical properties, and process stability. In terms of appearance, the tobacco leaves are bright orange-yellow with a uniform color and low breakage rate. Internally, the chemical composition is well-balanced, with a harmonious sugar-to-alkali ratio, resulting in the abundant generation of aroma-enhancing substances and a significant reduction in grassy odors and irritation. Regarding physical properties, it ensures the tobacco leaves are resistant to storage and mold, and their resilience is enhanced after rehydration, resulting in low industrial processing losses. The process stability is outstanding, especially addressing the problem of thick upper leaves and uneven ripening. By harvesting with stems to increase moisture buffering and implementing precise three-stage temperature and humidity control, the rate of damage during curing is significantly reduced. Simultaneously, the use of a natural gas curing barn ensures stable heat source, standardized operation, energy efficiency, and controllability, resulting in strong applicability and improved tobacco quality. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] This invention investigated different methods of curing tobacco leaves with stems, setting up several different curing treatments: "traditional six-and-a-half-leaf stem-cutting curing," "curing with stems on the top three and bottom three leaves," and "curing with small stems on single leaves." Through economic curing characteristics, enzyme activity detection during curing, chemical composition analysis of samples obtained during curing, chemical composition of the cured tobacco, sensory evaluation of the cured tobacco, observation of cell ultrastructure, analysis of neutral aroma substances, and detection of amino acid content and metabolomics in the cured tobacco, it was concluded that, based on current research and the performance of each treatment, the single-leaf treatment with small stems generally performs better in all aspects, with more balanced chemical composition, stronger enzyme activity, lower power consumption, and higher quality cured leaves, better meeting the requirements of high-quality tobacco leaves.

[0016] Example 1: This example discloses a method for curing segmented tobacco leaves with stems, including the following steps: Step 1: Select mature upper tobacco leaves, and then perform diagonal cutting to obtain tobacco leaves with stems. Among them, 4-6 upper tobacco leaves are selected, the diagonal cutting distance is 2-4 cm from the lowest leaf position, and the angle between the knife and the stem is 30-45°; Step 2: Classify, string onto poles, and load the obtained tobacco leaves with stems to obtain the tobacco leaves to be processed. Among them, the tobacco leaves with stems are classified according to leaf size, thickness and maturity. For every 1.4-1.5 m tobacco pole, 30-35 tobacco plants are strung onto each pole. The leaves evenly span the tobacco pole and are arranged in a staggered "pin" shape to ensure uniformity between the upper and lower layers and consistency within the same layer; Step 3: Bake the tobacco leaves to be processed (using a natural gas baking house). During the baking process, it is divided into three stages. The first stage is the yellowing stage. The processing process of this stage is as follows: Turn off the fan and all ventilation openings, ignite, and raise the dry bulb temperature to 36-38°C at a heating rate of 1°C / h, keep the wet bulb temperature at 35-37°C, and maintain for 24-36 h until 80% of the leaves turn yellow, the tobacco leaves become soft and collapse, and the connection between the tobacco stem and the leaves begins to turn yellow and become soft; The second stage is the color-fixing stage. The processing process of this stage is as follows: Raise the dry bulb temperature from 38°C to 42-43°C at a temperature rate of 2-3°C / h, keep the wet bulb temperature at 36-37°C, and stabilize the temperature for 10-15 h until the tobacco leaves and stems turn completely yellow, with the tips hooked and the edges curled. When the tobacco leaves turn completely yellow, raise the dry bulb temperature from 43°C to 48°C at a heating rate of 1-2°C / h, lower the wet bulb temperature to 37-38°C, and maintain the temperature at 46-48°C for more than 12 h until the tobacco leaves form small rolls. Then continue to raise the dry bulb temperature to 54-55°C, and stabilize the wet bulb temperature to 38-39°C, and stabilize the temperature until the pressed sheets are completely dry; The third stage is the dry rib stage. The processing process of this stage is as follows: Raise the dry bulb temperature to 68°C at a heating rate of 1°C / h, not exceeding 70°C at the highest, keep the wet bulb temperature at 40-42°C, and stabilize the temperature at 68°C until all the main veins and stems are completely dry. After the baking is completed, stop the fire and cool down. When the dry bulb temperature drops to be not much different from the ambient temperature, open the loading door and the air inlet in the early morning or evening when the air humidity is relatively high, and let the tobacco leaves naturally regain moisture until the tobacco leaves and ribs absorb water and become soft, and the tobacco leaves are tough and not easy to break when lifted by hand, then the tobacco can be unloaded to obtain the baked tobacco.

[0017] Performance test: I. Research on segmented stem-retaining, harvesting timing and methods of upper leaves The experiment was conducted at the Dazhai Tobacco Station in Gulin County, Luzhou, at an altitude of 1023-1180m. The climate is mild, with abundant rainfall and sunshine, making it an ideal ecological environment. The soil at the experimental site is lateritic red soil, and the previous crop was corn. The soil fertility is uniform and of medium to high level. A slope of approximately 20° was selected for planting Zhongchuan 208 tobacco. Tobacco leaves were harvested between 8:00 AM and 11:30 AM. Different treatment groups were established for harvesting: T1 group: harvested 5 days earlier with 4 leaves left; T2 group: harvested 5 days earlier with 5 leaves left; T3 group: harvested 5 days earlier with 6 leaves left; T4 group: harvested at maturity with 4 leaves left; T5 group: harvested with 5 leaves left... T6 group: Leave 6 leaves, harvest at maturity; T7 group: Leave 4 leaves, harvest 5 days later; T8 group: Leave 5 leaves, harvest 5 days later; T9 group: Leave 6 leaves, harvest 5 days later; Each treatment group has 3 rows and 2 protection rows, for a total of 29 rows, with a row spacing of 1.2m × 0.5m. Transplanting is concentrated from April 23 to April 25, and harvesting ends at the end of August 9. All agricultural operations are consistent, and the requirements for the control of major pests and diseases in the field are consistent with local technical requirements. The same management measures are completed within 1 day. Other management is carried out in accordance with local production standardization requirements, and testing is conducted. 1. Determination of field agronomic traits: Field agronomic traits were measured 10 days after the middle leaves of the tobacco were harvested and before harvesting 5 days earlier. The effects of the number of leaves retained on the field growth period of flue-cured tobacco were then observed. The results are shown in Table 1.

[0018] As shown in Table 1, with the increase of the number of leaves retained, the various agronomic indicators also increase accordingly. This may be because the more leaves retained, the more nutrients the plant absorbs from the air, which leads to an increase in plant height, stem circumference, maximum leaf length, and maximum leaf width. With the extension of the harvest time, the indicators also increase.

[0019] 2. Determination of economic traits of flue-cured tobacco leaves: After baking, the yield was recorded by grading. Grading was performed stepwise according to GB / T 2635-92, and the tobacco was weighed. The proportion of superior tobacco in each treatment group was also calculated. The results are shown in Table 2.

[0020] As shown in Table 2, the overall tobacco yield increases with the increase in the number of leaves retained. The average price is highest when harvesting is delayed by five days with four leaves retained, and lowest when harvesting is done five days earlier. Although the yield and value of tobacco increase with the extension of the harvesting time, the proportion of high-grade tobacco decreases compared to normally harvested tobacco. This may be because some leaves become overripe when harvested five days later, leading to a lower proportion of high-grade tobacco, but the top leaves reach full maturity, thus increasing the value. Analyzing the number of leaves retained, it can be seen that retaining six leaves is better than retaining four leaves, and also better than retaining five leaves for the proportion of high-grade tobacco. Analyzing the harvesting time, it can be seen that the proportion of high-grade tobacco is highest with normal harvesting, followed by harvesting five days later, and lowest with harvesting five days earlier.

[0021] 3. Determination of chemical composition of flue-cured tobacco: Two kg of flue-cured tobacco was selected, blanched at 105℃ for 30 min, then dried at 65℃, ground into powder, and stored. The contents of nicotine, total sugar, reducing sugar, starch, total nitrogen, potassium ions, chloride ions, polyphenols, and organic acids were measured. The results are shown in Table 3.

[0022] As shown in Table 3, different treatments can significantly improve the chemical composition content of tobacco leaves, and there are significant differences in chemical composition among the treatment groups.

[0023] II. Research on the Impact of Natural Gas Curing Equipment on Tobacco Leaf Quality Tobacco leaves of the same variety from the same plot of land were placed in the middle of a sealed curing barn. The curing process used biomass fuel-fired barns as group CK and natural gas fuel-fired barns as group A1. The intensive curing process was carried out according to the curing process in Example 1. 1. Appearance quality and economic characteristics of flue-cured tobacco leaves: After curing, 2 kg of tobacco leaf samples were taken for economic trait evaluation (according to the national standard for Grade 42 flue-cured tobacco) and appearance quality assessment. The results of each treatment were evaluated and are shown in Table 4.

[0024] As shown in Table 4, compared with biomass curing barns, the tobacco cured in natural gas curing barns is superior in terms of maturity, leaf structure, quality, and oil content. However, it is inferior in terms of color. Overall, the appearance quality of tobacco cured in natural gas curing barns is better than that of tobacco cured in biomass curing barns.

[0025] 2. Economic characteristics of flue-cured tobacco: After baking, the yield was recorded by grading. Each piece was graded according to GB / T 2635-92, weighed, and the proportion of superior tobacco in each treatment was calculated. The results are shown in Table 5.

[0026] As shown in Table 5, the tobacco produced by natural gas curing barns is superior to that produced by biomass curing barns in terms of both yield and value per mu. This indicates that using natural gas curing barns can increase the yield and value per mu of tobacco. However, the proportion of high-grade tobacco produced by biomass curing barns is higher than that produced by natural gas curing barns. This may be because natural gas curing barns use mixed varieties when filling the pits, and the different curing characteristics of each variety lead to a decrease in the proportion of high-grade tobacco after curing.

[0027] 3. Sensory quality test: Blind tastings were conducted on cigarettes made from various processed tobacco leaves by experts from Henan China Tobacco Industry Co., Ltd. The results are shown in Table 6:

[0028] As shown in Table 6, the middle leaves treated in the natural gas curing barn exhibit a pronounced mature aroma, good sweetness, and a good overall fragrance quality. The aroma intensity is moderate, the concentration is relatively strong, and there is a certain supporting structure. The aftertaste is also relatively clean, resulting in higher sensory quality compared to those treated in the biomass curing barn. The upper leaves treated in the biomass curing barn have a poorer aroma quality, slightly less aroma intensity, moderate concentration, and some off-flavors, resulting in poor sensory quality. Meanwhile, the upper leaves cured in the natural gas curing barn have a slightly sweet taste, moderate aroma quality, moderate aroma intensity, and a more harmonious overall aroma, resulting in higher sensory quality.

[0029] 4. Basic chemical component content test: Two kg of flue-cured tobacco was selected, blanched at 105℃ for 30 min, then dried at 65℃, ground into powder, and stored. The contents of nicotine, total sugar, reducing sugar, starch, total nitrogen, potassium ions, chloride ions, polyphenols, and organic acids were measured. The measurement results are shown in Table 7.

[0030] Table 7 shows that different treatments significantly altered the chemical composition of tobacco leaves, with significant differences among treatments. In the middle leaves, compared to the control group (CK), the A1 group had higher levels of total sugar, reducing sugar, nicotine, starch, sugar-nitrogen ratio, and sugar-nitrogen ratio; and lower levels of total nitrogen, potassium ions, and chloride ions. Significant differences were observed in reducing sugar, potassium ions, sugar-nitrogen ratio, and potassium-chloride ratio. In the upper leaves, compared to the control group (CK), the A1 group had higher levels of total sugar, reducing sugar, nicotine, chloride ions, and sugar-nitrogen ratio; and lower levels of total nitrogen, potassium ions, starch, sugar-nitrogen ratio, and potassium-chloride ratio. Significant differences were observed in nicotine, potassium ions, sugar-nitrogen ratio, and potassium-chloride ratio.

[0031] 5. Determination of neutral aroma compounds: Qualitative and quantitative analyses were performed using an HP5890-5972 gas chromatography-mass spectrometry (GC-MS) system, and the results are shown in Table 8.

[0032]

[0033]

[0034] As shown in Table 8, in the content of neutral aroma compounds in the middle leaves, the A1 treatment had a significantly higher total aroma content than the CK treatment. Furthermore, the A1 treatment outperformed the CK treatment in all aspects, including browning reaction products, carotenoid degradation products, phenylalanine degradation products, cephalosporin-like degradation products, and chlorophyll degradation products, with significant differences among the treatments. In the content of neutral aroma compounds in the upper leaves, the A1 treatment had a higher total aroma content than the CK treatment. The A1 treatment also outperformed the CK treatment in all aspects, including browning reaction products, carotenoid degradation products, cephalosporin-like degradation products, and chlorophyll degradation products, but its phenylalanine degradation product content was lower than that of the CK treatment. The aroma content among the treatments showed significant differences.

[0035] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

[0036] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for curing tobacco leaves in sections with stems, characterized in that, It includes the following steps: Step 1: Select mature upper tobacco leaves, and then perform diagonal cutting to obtain tobacco leaves with stems. Among them, 4-6 upper tobacco leaves are selected, the diagonal cutting distance is 2-4 cm from the lowest leaf position, and the angle between the knife and the stem is 30-45°; Step 2: Classify the obtained tobacco leaves with stems, string them on poles, and use a "pin" - shaped staggered hanging method during the loading process to ensure uniformity between the upper and lower layers and consistency within the same layer, obtaining the tobacco leaves to be processed; Step 3: Bake the tobacco leaves to be processed. After the baking is completed, stop the fire, reduce the temperature, naturally moisten, and unload the tobacco leaves to obtain the baked tobacco. Among them, a natural gas baking room is used for baking. During the baking process, it is divided into three stages. The first stage is the yellowing stage, the second stage is the color - fixing stage, and the third stage is the stem - drying stage.

2. The method for drying segmented tobacco leaves with stems according to claim 1, characterized in that, In the above - mentioned Step 2, the tobacco leaves with stems are classified according to leaf size, thickness, and maturity. For each 1.4 - 1.5 m tobacco pole, 30 - 35 tobacco plants are strung on each pole, and the leaves evenly span the tobacco pole.

3. The method for drying segmented tobacco leaves with stems according to claim 1, characterized in that, The processing process of the yellowing stage is as follows: Close the fan and all ventilation openings, ignite, and increase the dry - bulb temperature to 36 - 38 °C at a heating rate of 1 °C / h, keep the wet - bulb temperature at 35 - 37 °C, and maintain for 24 - 36 h until 80% of the leaves turn yellow, the tobacco leaves become soft and collapse, and the connection between the tobacco stem and the tobacco leaf begins to turn yellow and become soft.

4. The method for drying segmented tobacco leaves with stems according to claim 1, characterized in that, The processing process of the color - fixing stage is as follows: Increase the dry - bulb temperature from 38 °C to 42 - 43 °C at a temperature rate of 2 - 3 °C / h, keep the wet - bulb temperature at 36 - 37 °C, and maintain the temperature for 10 - 15 h until the tobacco leaves and stems turn completely yellow and the tips are hooked and the edges are curled. When the tobacco leaves turn completely yellow, increase the dry - bulb temperature from 43 °C to 48 °C at a heating rate of 1 - 2 °C / h, reduce the wet - bulb temperature to 37 - 38 °C, and maintain the temperature for more than 12 h when the dry - bulb temperature is 46 - 48 °C until the tobacco leaves form small rolls. Then continue to increase the dry - bulb temperature to 54 - 55 °C, stabilize the wet - bulb temperature to 38 - 39 °C, and maintain the temperature until the pressed pieces are completely dry.

5. The method for drying segmented tobacco leaves with stems according to claim 1, characterized in that, The processing process of the stem - drying stage is as follows: Increase the dry - bulb temperature to 68 °C at a heating rate of 1 °C / h, with a maximum not exceeding 70 °C, and the wet - bulb temperature is 40 - 42 °C. Stabilize the temperature at 68 °C until all the main veins and stems are completely dry.

6. The method for curing segmented tobacco leaves with stems according to claim 1, characterized in that, In the above - mentioned Step 3, when the dry - bulb temperature drops to the same as the ambient temperature, open the loading door and the air inlet in the early morning or evening when the air humidity is relatively high, and let the tobacco leaves naturally moisten until the tobacco leaves and stems absorb water and become soft, and when the tobacco leaves can be lifted with toughness and are not easily broken, the tobacco leaves can be unloaded.

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