Pu'er mountain tobacco leaf curing process and application thereof

Abstract

The invention provides a Pu'er mountain tobacco leaf curing process and application thereof.The Pu'er mountain tobacco leaf curing process comprises the tobacco loading stage, the yellowing stage, the color fixing stage and the stem drying stage and specifically comprises the following steps that tobacco loading is conducted, specifically, tobacco leaves are hung in a curing barn, and it is guaranteed that airflow is smooth; in a yellowing stage, baking by stages, including an early yellowing stage, a middle yellowing stage and a later yellowing stage; color fixing stage: performing stage-by-stage baking including an early color fixing stage and a later color fixing stage; and a stem drying stage: baking by stages, including an early stem drying stage and a later stem drying stage. According to the process provided by the invention, a clear stage target and a corresponding key temperature control node are set, and a dehydration drying process of the tobacco leaves and a conversion process of color and aroma substances are strictly matched, so that the'fresh, sweet and high-aroma 'quality of a final product is remarkably improved and stabilized while the baking efficiency is ensured.

Description

Technical Field

[0001] This invention belongs to the field of tobacco curing technology, specifically relating to a curing process for Pu'er mountain tobacco leaves and its application. Background Technology

[0002] A dense curing barn is a specialized curing equipment with high tobacco density, forced ventilation and hot air circulation, and an automatic temperature and humidity control system. However, current general curing processes often use relatively fixed temperature and humidity curves, failing to fully consider the characteristics of raw materials from different producing areas and varieties of tobacco, as well as their specific physiological and biochemical changes during the curing process. For tobacco leaves grown under the specific mountainous ecological conditions of Pu'er, their internal material composition and moisture state are unique. If conventional processes are used, the temperature and humidity control is not synchronized with the actual changes in the tobacco leaves, leading to an imbalance in dehydration and material transformation. Specifically, this manifests as insufficient or excessive water loss during the yellowing stage of the tobacco leaves, and a lack of coordination between pigment degradation and aroma formation during the color-fixing stage. Ultimately, this results in the aroma of the cured tobacco leaves being lost, insufficient sweetness, and the appearance of base off-flavors, as well as poor color and uniformity, making it difficult to consistently reflect the inherent potential of the "sweet and fragrant" tobacco leaves of this region.

[0003] CN110638081A discloses a highly efficient curing method for improving the quality of K326 tobacco leaves. The method uses biomass fuel for curing, harvesting appropriately mature K326 tobacco leaves; the leaves are bundled into poles and loaded into the curing barn for curing; the yellowing period is controlled, including control during the early, middle, and late stages of yellowing; the color-fixing period is controlled, including control during the early and late stages of color-fixing, with the initial color-fixing control involving a temperature increase of 1℃ / 1~2h after the yellowing period control; the drying period control involves raising the dry bulb temperature to 66~67℃ and adjusting the wet bulb temperature to 40~42℃. This invention solves problems in the traditional K326 tobacco curing process by slowly increasing the temperature in the early stage of color-fixing, combined with higher temperatures and lower humidity during the drying period. These problems include easy yellowing and difficult color fixing, stiff leaves after curing, insufficient aroma, slow temperature rise, unstable temperature leading to ash residue, inaccurate process execution, long curing time, low combustion efficiency, significant pollution, and frequent feeding. This significantly improves the proportion of medium and high-grade tobacco and the overall quality of the cured leaves. However, the tobacco leaves used in this method are different from those in this application, and their roasting tolerance differs, making this method unsuitable for roasting tobacco leaves grown in the Pu'er mountains.

[0004] Therefore, developing a refined roasting process that is highly compatible with the characteristics of Pu'er mountain tobacco leaves has become the key to improving the processing quality of this unique and high-quality raw material. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a curing process for Pu'er mountain tobacco leaves and its application. The process provided by this invention sets clear stage targets and corresponding key temperature control nodes, strictly matching the dehydration and drying process of the tobacco leaves with the transformation process of color and aroma substances. This significantly improves and stabilizes the "sweet and fragrant" quality of the final product while ensuring curing efficiency.

[0006] To achieve this objective, the present invention adopts the following technical solution: On one hand, the present invention provides a curing process for Pu'er mountain tobacco leaves, which includes loading, yellowing period, color fixing period and drying period, and the specific steps are as follows: Loading tobacco: Hang the tobacco leaves in the curing barn, ensuring good airflow; Yellowing stage: baking in stages, including early yellowing, middle yellowing and late yellowing; the dry bulb temperature in the early yellowing stage is 34-35℃ and the wet bulb temperature is 32-33℃; the dry bulb temperature in the middle yellowing stage is 37.5-38.5℃ and the wet bulb temperature is 34-36℃; the dry bulb temperature in the late yellowing stage is 41.5-42.5℃ and the wet bulb temperature is 35-36.5℃. Color setting period: staged baking, including pre-color setting and post-color setting; the dry bulb temperature in the pre-color setting period is 44-45℃ and the wet bulb temperature is 35.5-36.5℃; the dry bulb temperature in the post-color setting period is 47.5-48.5℃ and the wet bulb temperature is 36.5-37.5℃. Drying stage: staged baking, including early drying stage and late drying stage; the dry bulb temperature of the early drying stage is 53.4-54.5℃ and the wet bulb temperature is 37.5-38.5℃; the dry bulb temperature of the late drying stage is 65-68℃ and the wet bulb temperature is 39-40℃.

[0007] Because the tobacco varieties grown in the Pu'er region are not resistant to baking, the baking process must be slower and more gradual. Furthermore, the high moisture content of Pu'er mountain tobacco results in a slow heating rate, requiring early and gradual dehumidification. This slow dehumidification process, compared to the rapid baking strategy of conventional, baking-resistant varieties, leads to a unique approach combining "low-temperature slow baking" and "step-by-step gradual dehumidification." By setting key stable temperature points, the degradation and transformation of macromolecules such as starch and protein are facilitated without excessive stress on the tobacco leaves, accumulating sufficient precursors for the formation of sweet and aromatic compounds. Addressing the generally high moisture content of Pu'er mountain tobacco leaves during harvest, this invention initiates and advances the dehumidification process from the yellowing stage to the early color-fixing stage, while controlling the dehumidification rate slowly. This "early and gradual dehumidification" strategy ensures coordinated yellowing and water loss, avoiding the risks of later blackening and steaming due to high moisture content and untimely dehumidification, thus forming the basis for effective browning control. Compared to the baking processes of other varieties, this invention offers the following superior effects: 1. Overcoming the problem of varieties not being resistant to roasting: Through a customized slow roasting and gradual color change process, the problem of roasting green and blackening that easily occurs in Pu'er mountain tobacco leaves under conventional fast roasting has been successfully solved, enabling this variety to achieve full yellowing and perfect color fixation.

[0008] 2. Significantly improves the applicability of mountain tobacco: The process parameters are designed directly for the growth and development of tobacco leaves in high-altitude mountain tobacco fields and the characteristics of harvest moisture. In particular, the "early drainage and slow moisture" humidity control mode effectively addresses the challenges of high moisture content and difficult dehydration in mountain tobacco, greatly improving the adaptability and success rate of curing.

[0009] 3. Targeted shaping of quality and style: The slow roasting process allows time for the full transformation and accumulation of aroma substances. Combined with precise moisture control, the produced tobacco leaves not only have a uniform and bright appearance, but also exhibit a significant "sweet and fragrant" style. The quality consistency is superior to tobacco leaves from the same region that are roasted using general processes.

[0010] 4. Strong process specificity: This invention is not a simple adjustment to the existing process, but a special roasting system established based on the interaction between a specific variety and a specific ecology (Puer Mountain area). Its technical parameters have clear specificity and cannot be directly applied to other varieties or production areas.

[0011] Preferably, the drying room is a dense drying room; Preferably, the density of the suspension is 60-70 kg per cubic meter.

[0012] Preferably, the yellowing stage involves baking until the tips of the tobacco leaves in the high-temperature zone turn yellow by more than 2 inches, the leaves feel warm to the touch, and the fan maintains a speed of 900-1000 r / min. The goal of this stage is to gently initiate the enzymatic reaction, begin chlorophyll degradation, and prevent the formation of green tips in the high-temperature zone.

[0013] Preferably, during the mid-yellowing stage of baking, at least 90% of the tobacco leaves in the high-temperature layer have a yellow leaf area of ​​at least 90% (almost entirely yellow), with the leaves wilting and collapsing. At the low-temperature layer, at least 90% of the tobacco leaves have a yellow leaf area of ​​at least 60% (significantly yellowed), and the fan is maintained at 900-1000 r / min. At this point, the tobacco leaves need to lose 20%-30% of their moisture to ensure that yellowing and moisture loss are coordinated. The wet-bulb temperature is adjusted according to the tobacco leaves' tolerance to baking (35-36℃ for tolerant tobacco, 34-35℃ for non-tolerant tobacco). The baking process should not be changed until the yellowing target is achieved.

[0014] Preferably, the heating rate during the early to middle stages of yellowing is 0.4-0.6℃ / h.

[0015] Preferably, during the later stages of yellowing, the tobacco leaves are baked until at least 90% of the leaves in the entire kiln have a yellow leaf area of ​​at least 90%, and in the low-temperature layer, at least 90% of the tobacco leaves have a yellow leaf area of ​​at least 90% before collapsing, while the leaves in the high-temperature layer have curled tips and edges. This stage is crucial for preventing later browning and coordinating the transformation of substances.

[0016] Preferably, during the heating process from the middle to the later stages of yellowing, the fan is maintained at 900-1000 r / min, and after the heating is completed, the fan speed is switched to 1400-1500 r / min. This stage is critical; the temperature must be stabilized and the wet-bulb temperature must be finely adjusted to ensure that the low-temperature layer yellows sufficiently.

[0017] Preferably, the color-fixing process involves baking the tobacco leaves in the low-temperature layer until the veins are completely yellow, the tips are hooked and the edges are curled, and the fan maintains a speed of 1400-1500 r / min with a dry-wet difference of 8-9℃.

[0018] Preferably, the color-fixing process involves baking the tobacco leaves until the midrib turns white and the leaf tissue and lateral veins turn completely yellow. In the low-temperature layer, the midrib turns white and the leaf tissue turns completely yellow (white veins, yellow flesh), forming small cylindrical shapes, with the fan maintained at 1400-1500 r / min. After reaching 45℃, the fire needs to be intensified to prevent a drop in temperature. This signifies the complete completion of the yellowing process.

[0019] Preferably, the tobacco leaves are baked in the early stage until the leaf tissue in the low-temperature layer is completely dry, forming a large cylindrical shape, and the grayish-white color on the back of the leaf disappears, while the fan is maintained at 1400-1500 r / min. At this time, the color and aroma substances of the leaves are basically fixed.

[0020] Preferably, the heating rate from the later stage of color fixation to the early stage of drying is 0.4-0.6℃ / h.

[0021] Preferably, the drying process involves baking the tobacco leaves in the later stages until the main veins of the entire batch are completely dry; Preferably, the heating rate from the early to the late stages of the drying process is 0.8-1.2℃ / h, and the fan speed is reduced to 900-1000 r / min after the temperature reaches 54℃. The dry bulb temperature must be strictly controlled to not exceed 70℃ and the wet bulb temperature to not exceed 43℃ to prevent overheating.

[0022] The technical principle of this invention is based on the active regulation of the physiological and biochemical changes during the tobacco curing process. Through a carefully designed temperature and humidity program, it precisely coordinates the two key processes of moisture migration and material transformation, thereby shaping and stabilizing the "sweet and fragrant" style.

[0023] The principle of synergistic regulation of moisture and substance transformation: The process extends the yellowing period through "low-temperature slow baking," providing sufficient time for the full degradation and transformation of macromolecules such as starch and protein into small-molecule sugars and amino acids. At the same time, the "step-by-step dehumidification" strategy ensures that the dehydration rate is strictly synchronized with the yellowing and wilting process of the leaves (e.g., the water loss rate reaches 50-60% at the critical point of 48℃), creating an internal environment conducive to the formation of aroma precursors and unfavorable to the accumulation of harmful substances.

[0024] The principle of aroma-directed formation and browning control: During the mid-to-late yellowing stage to the early color-fixing stage (approximately 42-54℃), by precisely controlling the degree of dehydration, the cell water content of the tobacco leaves is reduced to below the critical point that inactivates relevant oxidases before entering the sensitive temperature zone of enzymatic browning reaction. This fundamentally inhibits the biochemical pathways that lead to browning and aroma deterioration. At the same time, the relatively mild heating rate and suitable humidity environment maximize the preservation of volatile aroma substances and promote the enzymatic release of glycosides and Maillard reactions, resulting in the formation of sweet and highly aromatic substances.

[0025] On the other hand, the present invention also provides the application of the Pu'er mountain tobacco curing process described above in the preparation of sweet and fragrant tobacco leaves.

[0026] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a process for curing tobacco leaves grown in the Pu'er Mountains. Applying this process yields the following significant benefits: Significantly improved quality and style: The color of the flue-cured tobacco leaves is uniform, with a high proportion of orange and golden yellow, and the phenomenon of roasting black or red is basically eliminated; the internal chemical composition is coordinated, the sugar-alkali ratio is appropriate, the aroma is abundant and pure, the sweet aroma is obvious, the high aroma is prominent, and the overall sensory quality and the rate of high-grade tobacco are greatly improved.

[0027] Enhanced process reliability and stability: By using intuitive changes in tobacco leaf morphology (such as "collapsed frame" and "small roll") as key operational nodes, clear and observable process standards have been established, reducing reliance on the personal experience of operators, making the curing process more standardized, and resulting in strong repeatability.

[0028] Improved economic efficiency: The optimized curve reduces ineffective heating and excessive dehumidification, resulting in a significant reduction in energy consumption. Simultaneously, the increased proportion of high-quality smoke directly enhances economic benefits, making the overall input-output ratio superior to traditional processes.

[0029] Strong regional adaptability: The process parameters are derived from targeted research on the characteristics of tobacco leaves in the Pu'er mountainous area and the wet-bulb adjustment strategy for tobacco leaves with different moisture contents (such as dry-day tobacco and rain-day tobacco). Therefore, it exhibits excellent universality and stability under the complex and variable production conditions in the Pu'er tobacco region, which is conducive to large-scale promotion and application. Detailed Implementation

[0030] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.

[0031] Example 1 This embodiment provides a curing process for Pu'er mountain tobacco leaves (Yunyan 85), the specific process of which is as follows: Comparative Example 1 This comparative example provides a curing process for Pu'er mountain tobacco leaves (Yunyan 85), the specific process of which is as follows: This comparative example adjusts the key stable temperature point and dehumidification process of the present invention, adopting a "high-temperature rapid baking" strategy. In the early stage of yellowing, the temperature is directly raised to 37°C for stabilization, with a wet-bulb temperature of 33°C; in the middle stage of yellowing, the temperature is rapidly raised to 40°C, with a wet-bulb temperature of 35°C; during the color-fixing period, the temperature rises at a faster rate of 1.5°C / hour, and in the later stage of drying, the temperature reaches a maximum of 68°C for stabilization.

[0032] Specifically as follows: Comparative Example 2 This comparative example provides a curing process for Pu'er mountain tobacco leaves (Yunyan 85), the specific process of which is as follows: This comparative example uses a conventional three-stage baking process. Yellowing stage: dry bulb temperature 36-38℃, wet bulb temperature 35-36℃, time approximately 48 hours; Color setting stage: dry bulb temperature increases to 54-55℃ at a rate of 1℃ every 2 hours, and wet bulb temperature gradually increases to 38-39℃; Rib drying stage: dry bulb temperature increases to 68℃, and wet bulb temperature increases to 41-42℃, until the midrib is completely dry.

[0033] Specifically as follows: Comparative Example 3 This comparative example provides a curing process for Pu'er mountain tobacco leaves (Yunyan 85), the specific process of which is as follows: The core of this comparative example is "low-temperature slow yellowing". During the yellowing period, the dry bulb temperature is kept stable at 34-36℃ for a long time, and the wet bulb temperature is 33-34℃, with the yellowing time lasting more than 60 hours. During the color-fixing period, the temperature rises very slowly and remains stable in the range of 45-48℃ for more than 30 hours. During the drying period, the highest temperature is controlled at 62℃.

[0034] Specifically as follows: Effect Comparison The process methods provided in Example 1 and Comparative Examples 1-3 were tested for effectiveness. The test items and methods are as follows: 1. Reflection of the light aroma style (sensory quality): The tobacco leaves after drying are smoked individually, and the typicality, purity and pleasantness of the light aroma style are evaluated. The maximum score is 100 points.

[0035] 2. Color fixation effect: 100 pieces of dried tobacco leaves were randomly selected, and the color of the tobacco leaves (proportion of lemon yellow and orange yellow and brightness of gloss) was evaluated according to national standards. The proportion of tobacco leaves with excellent color (orange yellow and bright color) was counted.

[0036] 3. Proportion of superior tobacco: All dried tobacco leaves in each batch are graded according to the national flue-cured tobacco grading standard (GB 2635), and the percentage of superior tobacco weight in the total weight is calculated.

[0037] The results are as follows: The roasting process provided in Example 1 of this invention is significantly superior to Comparative Examples 1-3 in highlighting the fragrant style of Pu'er mountain tobacco, ensuring the quality of tobacco color fixing, and improving economic benefits (proportion of high-grade tobacco). Specifically, Comparative Example 1, due to excessively rapid heating and high temperatures, resulted in excessive volatilization of aroma substances, a slightly stronger grassy and impure smell, and some tobacco leaves showing signs of reddening; Comparative Example 2, while using a conventional process, was relatively stable, but failed to accurately match the characteristics of mountain tobacco, resulting in an insufficiently prominent fragrant style; Comparative Example 3, with its low-temperature slow roasting process, led to a dull color and an increased proportion of ash-covered tobacco, severely affecting the appearance quality and the proportion of high-grade tobacco. The process of this invention, by precisely controlling the temperature and humidity curves and duration at each stage, achieves the optimal balance between the quality and yield of Pu'er mountain tobacco.

[0038] As can be seen from the above, the process provided by the present invention can effectively roast Pu'er mountain tobacco leaves, significantly improving the "sweet and fragrant" quality of the product. Comparing Example 1 and Comparative Examples 1-3, it can be found that the present invention, by adopting specific processes and setting key stable temperature points, can effectively promote the degradation and transformation of macromolecular substances, improve the sweet and fragrant quality, and control the dehumidification process to ensure that the yellowing and water loss of tobacco leaves are coordinated. Compared with the prior art, it can more effectively achieve intensive roasting of Pu'er mountain tobacco leaves.

[0039] The applicant declares that this invention illustrates the Pu'er mountain tobacco curing process and its application through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials of this invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

[0040] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0041] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A process for curing Pu'er mountain tobacco leaves, characterized in that, The Pu'er mountain tobacco curing process includes loading, yellowing period, color fixing period, and drying period, with the specific steps as follows: Loading tobacco: Hang the tobacco leaves in the curing barn, ensuring good airflow; Yellowing stage: baking in stages, including early yellowing, middle yellowing and late yellowing; the dry bulb temperature in the early yellowing stage is 34-35℃ and the wet bulb temperature is 32-33℃; the dry bulb temperature in the middle yellowing stage is 37.5-38.5℃ and the wet bulb temperature is 34-36℃; the dry bulb temperature in the late yellowing stage is 41.5-42.5℃ and the wet bulb temperature is 35-36.5℃. Color setting period: staged baking, including pre-color setting and post-color setting; the dry bulb temperature in the pre-color setting period is 44-45℃ and the wet bulb temperature is 35.5-36.5℃; the dry bulb temperature in the post-color setting period is 47.5-48.5℃ and the wet bulb temperature is 36.5-37.5℃. Drying stage: staged baking, including early drying stage and late drying stage; the dry bulb temperature of the early drying stage is 53.4-54.5℃ and the wet bulb temperature is 37.5-38.5℃; the dry bulb temperature of the late drying stage is 65-68℃ and the wet bulb temperature is 39-40℃.

2. The Pu'er mountain tobacco curing process according to claim 1, characterized in that, The drying room is a dense drying room; Preferably, the density of the suspension is 60-70 kg per cubic meter.

3. The Pu'er mountain tobacco curing process according to claim 1 or 2, characterized in that, During the initial yellowing stage, the tobacco leaves are baked until the tips turn yellow by more than 2 inches at high temperature, and the leaves feel warm to the touch, while the fan maintains a speed of 900-1000 r / min.

4. The Pu'er mountain tobacco curing process according to any one of claims 1-3, characterized in that, During the mid-yellowing stage, when the tobacco leaves in the high-temperature layer reach a yellow area of ​​no less than 90%, the leaves wither and collapse. In the low-temperature layer, when the tobacco leaves in the high-temperature layer reach a yellow area of ​​no less than 60%, the fan maintains a speed of 900-1000 r / min. Preferably, the heating rate during the early to middle stages of yellowing is 0.4-0.6℃ / h.

5. The Pu'er mountain tobacco curing process according to any one of claims 1-4, characterized in that, The yellowing process involves baking the tobacco leaves until at least 90% of the leaves in the entire oven have a yellow leaf area of ​​at least 90%, and in the low-temperature layer, at least 90% of the tobacco leaves have a yellow leaf area of ​​at least 90%, and the leaves collapse on the racks. In the high-temperature layer, the tobacco leaves have hooked tips and curled edges. Preferably, the fan is maintained at 900-1000 r / min during the heating process from the middle to the late stage of yellowing, and the fan is switched to 1400-1500 r / min after the heating is completed.

6. The Pu'er mountain tobacco curing process according to any one of claims 1-5, characterized in that, During the initial color-fixing process, the tobacco leaves in the low-temperature layer are baked until the veins are completely yellow, the tips are hooked and the edges are curled, and the fan is maintained at 1400-1500 r / min.

7. The Pu'er mountain tobacco curing process according to any one of claims 1-6, characterized in that, During the color-fixing stage, the tobacco leaves are baked until the main vein turns white and the leaf tissue and lateral veins turn completely yellow. In the low-temperature layer, the main vein turns white and the leaf tissue turns completely yellow, forming small tubes. The fan is maintained at 1400-1500 r / min.

8. The Pu'er mountain tobacco curing process according to any one of claims 1-7, characterized in that, The dry bar is baked until the tobacco leaf tissue in the low-temperature layer is completely dry, forming a large cylindrical shape, and the grayish-white color on the back of the leaf disappears. The fan is maintained at 1400-1500 r / min. Preferably, the heating rate from the later stage of color fixation to the early stage of drying is 0.4-0.6℃ / h.

9. The Pu'er mountain tobacco curing process according to any one of claims 1-8, characterized in that, The dry ribs are baked until the main veins of all the tobacco leaves in the oven are completely dry; Preferably, the heating rate from the early stage to the late stage of the drying process is 0.8-1.2℃ / h, and the fan speed is reduced to 900-1000 r / min after the temperature reaches 54℃.

10. The application of the Pu'er mountain tobacco curing process according to any one of claims 1-9 in the preparation of sweet and fragrant high-quality tobacco leaves.

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