A precise curing method for improving sensory evaluation quality of tobacco leaves and increasing high-grade tobacco rate

Abstract

The present application relates to the tobacco leaf baking processing technical field, specifically to a kind of precision baking method for improving sensory evaluation smoking quality of tobacco leaf and improving high-grade tobacco rate, the method is implemented in airflow two-way circulation curing barn, and includes the following steps: S1, state identification index system and stage target value are established, classification is carried out to tobacco leaf to be baked, and state identification index system is established;The system contains appearance maturity index A, moisture migration index W, component coordination index C;At the same time, the above-mentioned index (A / W / C) target value of each baking stage is set, and the supporting reference baking parameter;Method realizes the precision synchronization of baking process and the actual quality formation state of tobacco leaf, can reduce appearance defects such as green tendon, hanging ash, color, browning and baking red, reduce green mixed gas, reduce aroma loss, improve sensory evaluation smoking quality of tobacco leaf, improve high-grade tobacco proportion and average price, suitable for precision baking of tobacco leaf of different varieties, leaf position, maturity and moisture state.

Description

Technical Field

[0001] This invention relates to the field of tobacco curing and processing technology, specifically to a precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the yield of high-grade tobacco. Background Technology

[0002] Tobacco curing is a crucial step in flue-cured tobacco production, transforming fresh leaves into marketable tobacco. During curing, fresh tobacco leaves undergo a series of processes, including yellowing, dehydration, color fixing, drying into smaller leaves, and drying the inner core. The coordination between these stages directly determines the color, maturity, oil content, structure, and quality of the cured tobacco leaves. It also further influences sensory evaluation qualities such as aroma, aroma intensity, irritation, aftertaste, off-flavors, and combustibility. For tobacco leaf grading, appearance grade and internal quality jointly determine the percentage of high-grade tobacco and the average economic price. Therefore, curing is not simply a dehydration and drying process, but rather a process that involves the combined formation of the tobacco leaves' appearance quality, internal composition transformation, and sensory qualities.

[0003] Current tobacco curing methods mostly rely on preset temperature and humidity curves for control, supplemented by manual judgment. In practice, curing personnel typically determine whether to increase temperature, reduce humidity, or proceed to the next stage based on the color of the tobacco leaves observed through the observation window, the degree of leaf softening, the condition of the rolled leaves, and the dryness of the midrib. While this method is simple to operate, in actual production, the variety, leaf position, maturity, thickness, and moisture content of tobacco leaves within the same curing barn often vary. Different tobacco leaves are not entirely consistent in their yellowing rate, water loss rate, color stability, and internal component transformation rate. If curing is still carried out according to fixed times and fixed temperature and humidity points, it is easy to encounter problems where the process progress is not synchronized with the actual changes in the tobacco leaves. For example, if tobacco leaves lose moisture too quickly before fully turning yellow, they are prone to developing green veins, green flakes, and a greenish odor; if the leaves have mostly turned yellow but have not lost enough moisture, they are prone to dull yellowing, ash buildup, and discoloration; if the temperature is raised too quickly or the moisture is removed too rapidly during the color-fixing stage, browning, reddening, and dull color are likely to occur; if the temperature is too high or the moisture is removed too frequently during the drying stage (drying flakes and drying veins), aroma loss, increased irritation, and a worse aftertaste are likely to occur. All of these problems will reduce the sensory quality of tobacco leaves and lead to a decrease in the proportion of high-grade tobacco and the average economic price.

[0004] In recent years, bidirectional airflow circulating curing barns have improved the distribution of hot and humid air inside the tobacco loading chamber by using forward and reverse rotation of the circulating fans, which can reduce the differences in heating, humidification, and water loss between the upper and lower layers of tobacco leaves to a certain extent. However, in current applications, the circulating fans mostly operate at fixed forward and reverse rotation times, and temperature, humidity, and dehumidification control still mainly rely on preset curves or manual experience for adjustment. When tobacco leaves show insufficient yellowing, delayed water loss, increased risk of color fixing, or insufficient internal component coordination, the existing methods are difficult to identify and control in a timely manner, and problems such as uneven quality of tobacco leaves in the same furnace, a high proportion of low-grade tobacco, and large fluctuations in sensory quality may still occur.

[0005] Therefore, it is necessary to propose a precise curing method with the formation of tobacco leaf quality as the control target. During the curing process, the appearance maturity status, moisture migration status, and component coordination status related to sensory evaluation of tobacco leaves should be acquired in real time. Based on the actual state of the tobacco leaves, the dry bulb temperature, wet bulb temperature, heating rate, dehumidification method, temperature stabilization time, and bidirectional airflow forward and reverse operation parameters should be dynamically adjusted to ensure that the processes of yellowing, water loss, color fixation, drying of leaves, and drying of stems of tobacco leaves are carried out in a coordinated manner, thereby improving the sensory evaluation quality of tobacco leaves and increasing the rate of high-grade tobacco and the average economic price. Summary of the Invention

[0006] The purpose of this invention is to provide a precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the yield of high-grade tobacco, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The present invention aims to solve the technical problems existing in the prior art or related technologies.

[0008] Therefore, this invention provides a precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the percentage of high-grade tobacco. The method includes the following steps: S1: Establishing a state identification index system and stage target values.

[0009] First, the tobacco leaves to be cured are classified, and a state identification index system is established. This system includes the appearance maturity index A, the moisture migration index W, and the component coordination index C. At the same time, target values ​​for the above indicators (A / W / C) are set for each curing stage, including yellowing, color fixing, and dry ribs, as well as the corresponding benchmark curing parameters, including: dry bulb temperature, dehumidification method and dehumidification intensity, temperature stabilization time, and the benchmark parameters for forward and reverse rotation of the fan.

[0010] S2: Collect tobacco leaf curing status information

[0011] Monitoring points are set up on each floor of the drying room to collect multi-dimensional data in real time. The collected data includes: image data, weight data, near-infrared spectral data, dry and wet bulb temperatures, and fan operation data. After being measured and recorded at a unified time, the data is synchronously transmitted to the computing unit.

[0012] S3: Multi-information fusion recognition and judgment

[0013] The collected multi-source data is preprocessed and analyzed to quantify the current baking status:

[0014] Image processing and A-value calculation: background removal, white balance correction, and color segmentation are performed on the image, and the appearance maturity index A is calculated;

[0015] Weight data analysis and W value calculation: Smooth the weight data, calculate the water loss rate and water loss speed, and determine the water migration index W;

[0016] Spectral data analysis and C-value calculation: The spectral data is preprocessed and input into the calibration model to predict total sugar, reducing sugar, nicotine, total nitrogen and moisture, and then the component coordination index C is calculated;

[0017] S4: State determination and dynamic feedback (loop control)

[0018] The calculated current state indicators (A, W, C) are compared with the current stage switching conditions set in S1 to determine the appropriate outcome.

[0019] If the condition is "yes": If A, W, and C meet the switching conditions for the current stage, then proceed to step S4-2.

[0020] S4-2 Enter the next baking stage: Switch to the next baking stage and execute the dry bulb temperature, wet bulb temperature, dehumidification method and dehumidification intensity, temperature rise and stabilization time, and circulating fan forward and reverse rotation reference values ​​set for this stage; then continue to step S2 for real-time monitoring;

[0021] If the condition is "No": If the switching condition is not met, proceed to step S4-1;

[0022] S4-1 Dynamic Feedback Control: Based on the deviations of A, W, C from the stage target values, identify the current abnormal state. Abnormal states include insufficient yellowing, excessively fast or slow water loss, increased defect color, and deviation of component coordination. Accordingly, adjust the heating rate, wet-bulb temperature, dehumidification method and intensity, temperature stabilization time, and forward and reverse rotation time of the circulating fan, and feed the adjusted parameters back to step S2 for continued monitoring and judgment, forming a closed-loop control.

[0023] Further, step S1 includes: establishing an appearance maturity index A, a moisture migration index W, and a component coordination index C for real-time determination during the baking process, and simultaneously setting the target state of appearance maturity index A, the target state of moisture migration index W, the target state of component coordination index C, the dry bulb temperature, the wet bulb temperature, the dehumidification method, the temperature stability requirements, and the reference running time for forward and reverse rotation of the circulating fan for each baking stage.

[0024] The appearance maturity index A is calculated based on the areas of yellow, green, dark, and brown regions in the tobacco leaf image. Background removal, white balance correction, and color segmentation are performed on the tobacco leaf image to obtain the areas of yellow (Sy), green (Sg), dark (Sd), and brown (Sb), and the effective leaf area S is then calculated.

[0025] S = Sy + Sg + Sd + Sb;

[0026] The yellowing ratio H is calculated using the following formula:

[0027]

[0028] The defect color ratio D is calculated according to the following formula:

[0029] .

[0030] The appearance maturity index A is divided into levels A0 to A5. It should be noted that A0 represents the risk-priority judgment state when the proportion of defective colors exceeds the threshold, and is not the lowest level of yellowing maturity of tobacco leaves. A1 to A5 are used to characterize the degree of yellowing maturity under the condition that D ≤ 5%. When D > 5%, regardless of the level of yellowing proportion H, it is preferentially judged as A0. When A is A0, regardless of the level of yellowing proportion H, it does not directly enter the next heating stage, but should take measures such as pausing heating, reducing wet-bulb temperature, or increasing intermittent dehumidification.

[0031] The moisture migration index W is determined by both the water loss rate M and the water loss velocity Vm. The water loss rate M is calculated using the following formula:

[0032]

[0033] In the formula, W0 is the initial net weight of a representative tobacco leaf at the start of curing, and Wt is the current net weight of a representative tobacco leaf during the curing process. The water loss rate Vm is calculated according to the following formula:

[0034]

[0035] In the formula, Mt is the water loss rate at the current monitoring time, Mt-1 is the water loss rate at the previous monitoring time, and Δt is the interval between two adjacent weighing monitoring.

[0036] The component coordination index C is calculated from the predicted values ​​of total sugar (TS), reducing sugar (RS), nicotine (NIC), total nitrogen (TN), and moisture (WN) obtained by near-infrared spectroscopy. The calculation formula is as follows:

[0037] .

[0038] Wherein, Gt is the target sugar-alkali ratio for the current baking stage; Rt is the target proportion of reducing sugar to total sugar for the current baking stage; Nt is the target nitrogen-alkali ratio for the current baking stage; and Wc is the target moisture content for the current baking stage.

[0039] The component coordination index C is divided into levels C1 to C3.

[0040] Further, step S2 includes: setting monitoring points in the tobacco loading chamber of the bidirectional airflow circulating curing barn, with the monitoring points arranged on each layer of the curing barn; and setting an image acquisition device, a weighing device, a near-infrared spectroscopy acquisition device, and a temperature and humidity sensor at the monitoring points. The image acquisition device is used to acquire representative tobacco leaf surface images; the weighing device is used to obtain representative tobacco leaf weight changes; the near-infrared spectroscopy acquisition device is used to acquire representative tobacco leaf spectral data; and the temperature and humidity sensor is used to acquire the dry-bulb temperature and wet-bulb temperature of the curing barn; the leaf surface images, weight change data, and near-infrared spectral data are acquired periodically at preset time intervals.

[0041] Further, step S3 includes: the calculation unit receiving the tobacco leaf surface image, weight change data, near-infrared spectral data, and curing barn temperature and humidity data collected in step S2; performing color segmentation on the tobacco leaf surface image and calculating the appearance maturity index A; performing moving average processing on the weight change data and calculating the water loss rate M and water loss velocity Vm to determine the moisture migration index W; preprocessing the near-infrared spectral data and inputting it into the near-infrared correction model to obtain the predicted values ​​TS (total sugar), RS (reducing sugar), NIC (nicotine), TN (total nitrogen), and WN (moisture), and calculating the component coordination index C. The current tobacco curing status is identified based on the calculation results.

[0042] Further, step S4 includes: matching the target state values ​​of appearance maturity index A, moisture migration index W, and component coordination index C set for each baking stage according to the identification result of step S3; switching to the next baking stage when the appearance maturity index A, moisture migration index W, and component coordination index C reach the current stage transition conditions; and adjusting the dry bulb temperature, wet bulb temperature, heating rate, dehumidification method and intensity, temperature stabilization time, and forward and reverse rotation operation time of the circulating fan in real time when the appearance maturity index A, moisture migration index W, or component coordination index C deviates from the target state of the current stage. The dehumidification method and intensity include at least one of continuous dehumidification, intermittent dehumidification, dehumidification duration, and shutdown duration.

[0043] Specifically, step S4 includes the following phased control process:

[0044] a. Preheating equilibrium period

[0045] During the preheating and equalization period, the dry bulb temperature is controlled to rise from room temperature to 35°C, and the wet bulb temperature is controlled to rise from room temperature to 34°C. The circulating fan operates based on 60 minutes of forward rotation and 60 minutes of reverse rotation.

[0046] When the appearance maturity index A reaches A1 to A2, the moisture migration index W reaches W1 to S1, and the component coordination index C is C1 or C2, it enters the low temperature and high humidity yellowing period.

[0047] When the appearance maturity index A differs by more than one level between different layers, the one-way running time of the fan should be shortened by 10 to 20 minutes; when the moisture migration index W is W1-S2, the heating rate should be reduced and the dehumidification should be decreased.

[0048] b. Yellowing period due to low temperature and high humidity

[0049] During the low temperature and high humidity yellowing period, the dry bulb temperature is controlled to rise from 35℃ to 38℃, and the wet bulb temperature is controlled to rise from 34℃ to 35℃. The circulating fan is operated with a standard of 60 minutes of forward rotation and 60 minutes of reverse rotation.

[0050] When the appearance maturity index A reaches A3, the moisture migration index W reaches W2-S1, and the component coordination index C is C1 or C2, the yellowing and water loss coordination period begins.

[0051] When the appearance maturity index A is lower than A2 and the moisture migration index W is in the S2 state, reduce the heating rate, reduce dehumidification, or prolong the stable temperature under the current temperature and humidity conditions; when the appearance maturity index A reaches A3 but the moisture migration index W is in the S0 state, increase intermittent dehumidification; when the composition coordination index C is C3, maintain the current dry bulb temperature and wet bulb temperature, reduce continuous dehumidification, and prolong the stable temperature.

[0052] c. Yellowing and water loss adjustment period

[0053] During the yellowing and water loss coordination period, the dry bulb temperature was controlled to rise from 38℃ to 42℃, and the wet bulb temperature was controlled to rise from 35℃ to 35.5℃. The circulating fan was operated with a standard of 50 minutes of forward rotation and 50 minutes of reverse rotation.

[0054] When the appearance maturity index A reaches A4, the moisture migration index W reaches W3-S1, and the component coordination index C is C1 or C2, the color stabilization and color fixing phase begins.

[0055] When the appearance maturity index A reaches A4 but the moisture migration index W is W3-S0, lower the wet-bulb temperature, increase intermittent dehumidification, and shorten the unidirectional operation time of the fan by 10-20 minutes; when the moisture migration index W reaches W3-S1 or W3-S2 but the appearance maturity index A does not reach A4, reduce dehumidification and prolong the stable temperature period; when the composition coordination index C is C3, maintain the current dry-bulb temperature, reduce the dehumidification intensity, and prolong the stable temperature period.

[0056] d. Preliminary stage of color stabilization and fixing

[0057] In the early stage of color stabilization and fixing, the dry bulb temperature is controlled to rise from 42℃ to 45℃, the wet bulb temperature is kept at 35.5℃, and the circulating fan is operated based on 80 minutes of forward rotation and 80 minutes of reverse rotation.

[0058] When the appearance maturity index A reaches A4 to A5 and is not A0, the moisture migration index W transitions from W3-S1 to W4-S1, and the component coordination index C is C1 or C2, the color stabilization and color fixing stage begins.

[0059] When the appearance maturity index A is A0, stop heating, lower the wet-bulb temperature and increase intermittent dehumidification; when the moisture migration index W remains at W3-S0, increase intermittent dehumidification; when the moisture migration index W changes to W4-S2, reduce dehumidification and lower the heating rate; when the composition coordination index C changes to C3, stop heating and extend the stable temperature period.

[0060] e. Color stabilization and fixing post-processing

[0061] In the later stage of color stabilization and fixing, the dry bulb temperature is controlled to rise from 45℃ to 48℃, the wet bulb temperature is kept at 35.5℃, and the circulating fan is operated based on 80 minutes of forward rotation and 80 minutes of reverse rotation.

[0062] When the appearance maturity index A reaches A5 and is not A0, the moisture migration index W reaches W4-S1, and the component coordination index C is C1 or C2, it enters the early stage of stabilizing aroma and drying.

[0063] When the appearance maturity index A is A0, stop heating, lower the wet bulb temperature and increase intermittent dehumidification; when the defect color ratio D is higher than 5%, shorten the one-way running time of the fan by 10-30 minutes; when the moisture migration index W is W4-S2, reduce the continuous dehumidification time; when the moisture migration index W is W4-S0, increase intermittent dehumidification.

[0064] f. Sterilization of dried gluten in the early stage

[0065] In the early stage of stabilizing the aroma and drying the gluten, the dry bulb temperature is controlled to rise from 48℃ to 54℃, and the wet bulb temperature is controlled to rise from 35.5℃ to 36℃. The circulating fan is operated with a standard of 100 minutes of forward rotation and 100 minutes of reverse rotation.

[0066] When the conditions for stabilizing the aroma and drying the gluten meet the following criteria in the early stage: A remains A5 and is not A0, W remains W4-S1, and C is C1 or C2, and the temperature is stabilized at 54℃ for a preset time or the near-infrared predicted moisture value WN reaches the target moisture range for this stage, the process enters the middle stage of stabilizing the aroma and drying the gluten.

[0067] When the component coordination index C changes from C1 or C2 to C3, reduce the heating rate, reduce continuous dehumidification, or extend the stable temperature period; when the near-infrared predicted moisture value WN decreases at a rate exceeding the target range for this stage, reduce the duration of the dehumidification period and extend the shutdown time.

[0068] g. Sterilized Fragrant Dry Tendon Mid-term

[0069] During the middle stage of stabilizing the drying process, the dry bulb temperature was controlled to rise from 54℃ to 62℃, and the wet bulb temperature was controlled to rise from 36℃ to 37.5℃. The circulating fan was operated with a standard of 120 minutes of forward rotation and 120 minutes of reverse rotation.

[0070] When the appearance maturity index A remains at A5 and is not A0, the moisture migration index W enters W5, and the composition coordination index C is C1 or C2, it enters the late stage of temperature-limited drying.

[0071] When the moisture migration index W is still at W4-S0 or W4-S1, maintain the current temperature and humidity conditions and increase intermittent dehumidification; when the composition coordination index C turns to C3, reduce continuous dehumidification and control the temperature rise; when the moisture migration index W between different layers differs by more than one level, shorten the unidirectional operation time of the fan by 10-30 minutes.

[0072] h. Temperature-limited dry gluten later stage

[0073] In the later stage of temperature-controlled dry tumble drying, the dry bulb temperature is controlled to rise from 62℃ to 66℃, and the wet bulb temperature is controlled to rise from 37.5℃ to 39℃. The circulating fan is operated based on 120 minutes of forward rotation and 120 minutes of reverse rotation.

[0074] When the moisture migration index W reaches W5-S0 and remains so for more than 1 hour, the near-infrared predicted moisture value WN reaches the endpoint moisture threshold, or manual sampling shows that the main vein is completely dry, and the component coordination index C does not change to C3, heating is stopped and the product is removed from the oven for rehydration.

[0075] When the moisture migration index W is W5-S1, maintain the dry bulb temperature at 66℃ and continue to keep the temperature stable; when the lower layer of tobacco leaves or the main vein of slightly moist tobacco leaves has not yet reached W5-S0, shorten the one-way running time of the fan by 10-30 minutes; when the composition coordination index C turns to C3, stop increasing the dry bulb temperature, reduce continuous dehumidification and extend the shutdown time.

[0076] Compared with the prior art, the present invention has at least the following beneficial effects:

[0077] (1) This invention establishes a precise tobacco leaf roasting status identification system consisting of appearance maturity index A, moisture migration index W and component coordination index C. It incorporates tobacco leaf color changes, water loss process and quality-related component changes into the roasting control basis, avoiding the subjectivity and lag caused by traditional roasting methods that rely solely on manual observation of color, roll and main vein dryness.

[0078] (2) This invention uses the achievement of stage target states in A, W, and C as the basis for stage transition, and performs corresponding temperature and humidity, dehumidification, temperature stabilization, and bidirectional airflow regulation measures when the target state is not achieved. Compared with fixed-time curve baking, this invention can determine whether to raise the temperature, dehumidify, extend the temperature stabilization period, and adjust the airflow direction according to the actual state of the tobacco leaves, so that the baking process is synchronized with the actual quality formation process of the tobacco leaves.

[0079] (3) The present invention sets different target states and trigger control measures at different baking stages, which can reduce the proportion of low-grade defects in the tobacco leaves after baking, increase the proportion of high-grade tobacco, enhance the coordination of the internal chemical components of the tobacco leaves, and ultimately help to increase the average economic price of tobacco leaves and baking revenue.

[0080] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above and other objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0081] Figure 1 This is a flowchart illustrating a precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the yield of high-grade tobacco, as described in this application.

[0082] Figure 2 This is a curing process curve diagram of a precision curing method for improving the sensory evaluation quality of tobacco leaves and increasing the yield of high-grade tobacco, as described in this application. Detailed Implementation

[0083] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0084] Please see Figures 1-2 This invention provides a technical solution: a precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the yield of high-grade tobacco, the overall process of which is as follows: Figure 1 As shown, its baking process curve is as follows: Figure 2As shown. The core of this method lies in the fact that it does not use a fixed baking time as the sole basis for stage transition. Instead, it collects real-time images of tobacco leaf surfaces, weight changes, and near-infrared spectral data in a bidirectional airflow circulating curing barn to calculate the appearance maturity index A, moisture migration index W, and component coordination index C, respectively. The transition is based on A, W, and C reaching the target state of the corresponding stage. The control system matches the target state values ​​of the appearance maturity index A, moisture migration index W, and component coordination index C for each baking stage according to the real-time changes of A, W, and C. When the appearance maturity index A, moisture migration index W, and component coordination index C reach the current stage transition conditions, it switches to the next baking stage. When the appearance maturity index A, moisture migration index W, or component coordination index C deviates from the target state of the current stage, it adjusts the dry-bulb temperature, wet-bulb temperature, heating rate, dehumidification intensity, temperature stabilization time, and the forward and reverse rotation time of the circulating fan in real time.

[0085] Example

[0086] Depend on Figure 1 , Figure 2 As shown, this embodiment provides a precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the yield of high-grade tobacco, specifically including the following steps:

[0087] This embodiment uses the mature fresh tobacco leaves of the main tobacco variety Honghua Dajinyuan in the Dali tobacco-growing area of ​​Yunnan Province as the object. The method of the present invention is implemented in a dense curing barn with bidirectional airflow circulation (the tobacco loading chamber is 8m×2.7m×4.2m with four layers of tobacco hanging racks). At the same time, a three-stage curing process is set up as a control.

[0088] Fresh tobacco leaves of the Honghua Dajinyuan variety, characterized by uniform growth and maturity, were selected from the field. After harvesting, the leaves were sorted according to size, maturity, thickness, and moisture content, removing diseased, overripe, veiny, and mechanically damaged leaves. The sorted leaves were then evenly bundled into poles or clamps and packed into a densely ventilated curing barn, adhering to the principle of relatively concentrated packing at the same maturity level, leaf position, and moisture content. During packing, the leaves were kept evenly arranged with consistent density within the same layer to avoid localized overcrowding that could cause airflow short-circuiting or moisture retention.

[0089] After the tobacco is loaded, close the curing chamber door, start the circulating fan, heating system, temperature and humidity control system, image acquisition device, weighing device and near-infrared spectral acquisition device, and start curing after confirming that all devices are operating normally.

[0090] Step S1: Establish a precise tobacco curing status identification index system and phased target values.

[0091] In this embodiment, a precise tobacco curing status identification index system is first established. The index system includes the appearance maturity index A, the moisture migration index W, and the component coordination index C.

[0092] The appearance maturity index A is used to characterize changes in leaf color and defect colors. Before curing, sample tobacco leaves with the same variety, leaf position, and maturity as the tobacco leaves to be cured are selected, and leaf images are acquired to establish color segmentation thresholds. The image segmentation regions include yellow, green, gray, and brown areas.

[0093] Furthermore, the appearance maturity index A is calculated based on the areas of yellow, green, dark, and brown regions in the tobacco leaf image. Background removal, white balance correction, and color segmentation are performed on the tobacco leaf image to obtain the areas of yellow (Sy), green (Sg), dark (Sd), and brown (Sb), and the effective leaf area S is calculated.

[0094]

[0095] The yellowing ratio H is calculated using the following formula:

[0096]

[0097] The defect color ratio D is calculated according to the following formula:

[0098]

[0099] The appearance maturity index A is divided into levels A0 to A5, as shown in Table 1:

[0100] Table 1. Classification of Appearance Maturity Index A Level

[0101] A0 D＞5% A1 D≤5%, H<25% A2 D≤5%, 25%≤H<50% A3 D≤5%, 50%≤H<80% A4 D≤5%, 80%≤H<95% A5 D≤5%, H≥95%

[0102] It should be noted that A0 is the priority judgment state for defect color risk, not the lowest level of yellowing maturity of tobacco leaves; A1 to A5 are used to characterize the yellowing maturity under the condition of D≤5%.

[0103] The moisture migration index W is determined by the water loss rate M and the water loss speed Vm. Before curing begins, the initial net weight W0 of a representative tobacco leaf is recorded; during curing, the weighing device records the current net weight Wt of the representative tobacco leaf in real time. The water loss rate M is calculated according to the following formula:

[0104]

[0105] In the formula, W0 is the initial net weight of a representative tobacco leaf at the start of curing, and Wt is the current net weight of a representative tobacco leaf during the curing process. The water loss rate Vm is calculated according to the following formula:

[0106]

[0107] In the formula, Mt is the water loss rate at the current monitoring time, Mt-1 is the water loss rate at the previous monitoring time, and Δt is the interval between two adjacent weighing monitoring.

[0108] The water migration index W includes the cumulative water loss stages W1 to W5 and the water loss rate states S0 to S2, as shown in Table 2. S0 indicates slow water loss, S1 indicates appropriate water loss, and S2 indicates fast water loss.

[0109] Table 2 Classification of Moisture Migration Index (W)

[0110] Cumulative water loss stage M range S0: Water loss is slow S1: Suitable for water loss S2: Water loss is too rapid W1 M＜10% Vm < 0.1% / h 0.1% / h ≤ Vm ≤ 0.5% / h Vm>0.5% / h W2 10%≤M＜20% Vm < 0.3% / h 0.3% / h≤Vm≤0.8% / h Vm>0.8% / h W3 20%≤M＜40% Vm < 0.5% / h 0.5% / h ≤ Vm ≤ 1.2% / h Vm>1.2% / h W4 40%≤M＜70% Vm < 0.4% / h 0.4% / h ≤ Vm ≤ 1.5% / h Vm > 1.5% / h W5 M≥70% Vm < 0.3% / h 0.3% / h≤Vm≤0.8% / h Vm>0.8% / h

[0111] The component coordination index C was calculated from near-infrared spectroscopy prediction results. Before curing, a near-infrared calibration model was established using samples of the same variety, leaf position, and maturity of tobacco leaves to be cured. The calibration model was used to predict total sugar (TS), reducing sugar (RS), nicotine (NIC), total nitrogen (TN), and moisture (WN).

[0112] The component coordination index C is calculated according to the following formula:

[0113] .

[0114] Wherein, Gt is the target sugar-alkali ratio for the current baking stage; Rt is the target proportion of reducing sugar to total sugar for the current baking stage; Nt is the target nitrogen-alkali ratio for the current baking stage; and Wc is the target moisture content for the current baking stage.

[0115] The component coordination index C is divided into levels C1 to C3 as shown in Table 3:

[0116] Table 3. Classification of Ingredient Harmony Index C Grade:

[0117] C1 C≤0.20 C2 0.20＜C≤0.35 C3 C＞0.35

[0118] Step S2: Collect tobacco leaf curing status information in real time or at preset time intervals.

[0119] Monitoring points were set up in the tobacco loading chamber of the bidirectional airflow curing barn. The monitoring points were distributed in each layer, and representative tobacco leaves with maturity, leaf thickness and moisture content were selected as monitoring objects in each layer.

[0120] The image acquisition device is positioned at an observation window or on the side wall of the tobacco loading chamber, capable of stably capturing images of representative tobacco leaf surfaces, with the acquisition direction facing the representative tobacco leaf surface. The image acquisition device acquires an image of the tobacco leaf surface every 20 minutes and sends the image data to the computing unit.

[0121] A weighing device is installed at a representative tobacco stem or clip to acquire data on changes in tobacco weight. The weighing device collects weight data every 20 minutes and sends the data to the computing unit.

[0122] The near-infrared spectroscopy acquisition device was positioned near a representative tobacco leaf, with the acquisition window avoiding tobacco clips, tobacco stems, and areas of significant shadow. The device acquired spectral data from the tobacco leaf every 20 minutes and transmitted the data to the computing unit.

[0123] Temperature and humidity sensors are installed in the tobacco loading chamber of the curing barn to collect dry-bulb and wet-bulb temperatures. The circulating fan control module records the forward and reverse rotation of the circulating fan and its running time. All monitoring data are synchronously transmitted to the computing unit after being measured and recorded at a unified time.

[0124] Step S3: Identification and determination of tobacco curing status based on multi-information fusion

[0125] The computing unit receives the tobacco leaf images, weight change data, near-infrared spectral data, and curing barn temperature and humidity data collected in step S2, and performs synchronous calibration, outlier removal, and standardization processing.

[0126] First, the computing unit performs background removal, white balance correction, and color segmentation on the tobacco leaf image, extracts the yellow area Sy, green area Sg, dark area Sd, and brown area Sb, calculates the yellowing ratio H and defect color ratio D, and determines the appearance maturity index A based on H and D.

[0127] Secondly, the calculation unit reads the tobacco leaf weight change data collected by the weighing device, calculates the water loss rate M and water loss rate Vm, and determines the moisture migration index W based on M and Vm.

[0128] Then, the computing unit smooths, baselines, and standardizes the near-infrared spectral data, inputs the processed spectral data into the near-infrared correction model, and obtains the predicted values ​​for total sugar (TS), reducing sugar (RS), nicotine (NIC), total nitrogen (TN), and moisture (WN). Based on the target values ​​for each stage, the component coordination index (C) is calculated.

[0129] Finally, the calculation unit identifies and determines the current tobacco curing status based on the appearance maturity index A, moisture migration index W, and component coordination index C.

[0130] Step S4: Phased and precise control based on the results of tobacco leaf curing status assessment

[0131] The calculation unit matches the judgment result obtained in step S3 with the target windows of each baking stage, and sends control commands to the temperature and humidity control module, dehumidification control module, and circulating fan control module according to the current baking stage of the tobacco leaves. This allows for real-time adjustment of dry-bulb temperature, wet-bulb temperature, heating rate, dehumidification method and intensity, temperature stabilization time, and the forward and reverse rotation time of the circulating fan. The specific operation process of this embodiment is as follows:

[0132] a. Preheating equilibrium period

[0133] After the flue gas is loaded, the heating system and circulating fan are started. The dry bulb temperature rises from 30℃ to 35℃, and the wet bulb temperature rises from 30℃ to 34℃, and then the temperature is stabilized at 35℃ and 34℃. The circulating fan operates by rotating clockwise for 60 minutes and counterclockwise for 60 minutes.

[0134] Image monitoring at this stage shows that all layers of tobacco leaves are within the A1-A2 range; weighing monitoring shows that the moisture migration index is W1-S1; and the near-infrared predicted component coordination index is C1. All indicators meet the target requirements for this stage, therefore the system will operate according to the set heating program without further adjustments.

[0135] b. Yellowing period due to low temperature and high humidity

[0136] The dry-bulb temperature was raised from 35℃ to 38℃, and the wet-bulb temperature was raised from 34℃ to 35℃, and then stabilized at 38℃ and 35℃. The circulating fan was operated by rotating clockwise for 60 minutes and counterclockwise for 60 minutes.

[0137] In the later stages of this phase, image recognition showed that the tobacco leaves reached A3, weighing monitoring showed a moisture migration index of W2-S1, and near-infrared predicted component coordination index of C1, indicating that the tobacco leaves had turned yellow sufficiently, the early water loss rate was appropriate, and the component coordination state did not deviate significantly. Therefore, this phase was operated according to normal process, without adjusting the heating rate, wet-bulb temperature, dehumidification method, or airflow time.

[0138] c. Yellowing and water loss adjustment period

[0139] The dry-bulb temperature was increased from 38℃ to 42℃, and the wet-bulb temperature was increased from 35℃ to 35.5℃, and then stabilized at 42℃ and 35.5℃. The circulating fan was operated in a standard mode of 50 minutes forward and 50 minutes reverse, with intermittent dehumidification set.

[0140] When the temperature was stabilized at 42℃ until the later stage of this phase, image recognition showed that the tobacco leaves reached A4, indicating that the yellowing appearance had met the requirements before color fixing; weighing monitoring showed that the moisture migration index was W3-S0, indicating that the cumulative water loss had entered the yellowing-drying coordination stage, but the current water loss rate was slow; the near-infrared predicted component coordination index was C2, which did not deviate significantly.

[0141] Instead of directly proceeding to the next stage, the control system performed the following real-time adjustments: maintaining the dry-bulb temperature at 42℃ and lowering the wet-bulb temperature from 35.5℃ to 35.0℃; adjusting the intermittent dehumidification to dehumidification for 8 minutes followed by a 15-minute stop; adjusting the circulating fan from 50 minutes forward and 50 minutes reverse rotation to 40 minutes forward and 40 minutes reverse rotation; and adding 3 hours of temperature stabilization under the above conditions.

[0142] After adjustment, the moisture migration index changed from W3-S0 to W3-S1, the appearance maturity index remained at A4, and the composition coordination index remained at C2, meeting the conditions for entering the early stage of color stabilization and fixing.

[0143] d. Preliminary stage of color stabilization and fixing

[0144] The dry-bulb temperature was raised from 42℃ to 45℃, while the wet-bulb temperature was maintained at 35.5℃, and then stabilized at 45℃ and 35.5℃. The standard operating mode for the circulating fan was 80 minutes of forward rotation followed by 80 minutes of reverse rotation.

[0145] In the first half of this stage, image recognition showed that the tobacco leaves maintained an A4-A5 grade, with a defect color ratio D ≤ 5%; weighing monitoring showed that the moisture migration index transitioned from W3-S1 to W4-S1; and the near-infrared predicted component coordination index was C2. All indicators met the pre-coloring targets.

[0146] During the later stages of temperature stabilization at 45℃, image recognition showed a slight increase in localized dark areas on the leaf surface, but the defect color ratio D still did not exceed 5%, and the system did not enter the A0 risk state. Therefore, the control system only made a slight modification to the dehumidification method, changing the dehumidification 5min, stop dehumidification 25min to dehumidification 8min, stop dehumidification 20min; the circulating fan remained in forward rotation for 80min, reverse rotation for 80min, without extending the temperature stabilization time in this stage.

[0147] e. Color stabilization and fixing post-processing

[0148] The dry-bulb temperature was raised from 45℃ to 48℃, while the wet-bulb temperature was maintained at 35.5℃, and then stabilized at 48℃ and 35.5℃. The circulating fan was operated by rotating clockwise for 80 minutes and counterclockwise for 80 minutes.

[0149] When the temperature was stabilized at 48℃ until the middle to late stage of this process, image recognition showed that the proportion of defective colors (D) in the middle layer of tobacco leaves reached 5.7%, and the appearance maturity index entered A0, indicating a risk of ash accumulation, discoloration, or browning. At this time, weighing monitoring showed that the moisture migration index was W4-S1, indicating that the rate of water loss was normal; the near-infrared predicted component coordination index was C2, with no obvious component deviation.

[0150] The control system performs the following real-time adjustments: pauses further heating and maintains the dry bulb temperature at 48℃; lowers the wet bulb temperature from 35.5℃ to 35.0℃; adjusts intermittent dehumidification to dehumidification for 10 minutes followed by a 18-minute pause; shortens the cycle of the circulating fan from 80 minutes forward and 80 minutes reverse to 60 minutes forward and 60 minutes reverse; and adds 2 hours of temperature stabilization under the above conditions.

[0151] After adjustment, the proportion of defective color D did not continue to increase. After multiple retests and moving average processing, it stabilized below 5%. The appearance status changed from A0 risk status to A5 judgment status. The moisture migration index remained W4-S1 and the component coordination index remained C2. Then it entered the early stage of stabilizing the aroma and drying the fibers.

[0152] f. Sterilization of dried gluten in the early stage

[0153] The dry-bulb temperature was increased from 48℃ to 54℃, and the wet-bulb temperature was increased from 35.5℃ to 36℃, and then stabilized at 54℃ and 36℃. The circulating fan was operated by rotating clockwise for 100 minutes and counterclockwise for 100 minutes.

[0154] Monitoring at this stage showed that the appearance maturity index remained at A5, with no A0 status observed; the moisture migration index was W4-S1; the near-infrared predicted component coordination index was C2, and the rate of decrease in the predicted moisture value WN did not exceed the target range for this stage. This indicates that the leaf drying process proceeded smoothly, without any risk of rapid drying or aroma loss. Therefore, the original process operation will be maintained at this stage, without adjusting the dehumidification method or the forward and reverse rotation time of the circulating fan.

[0155] g. Sterilized Fragrant Dry Tendon Mid-term

[0156] The dry-bulb temperature was increased from 54℃ to 62℃, and the wet-bulb temperature was increased from 36℃ to 37.5℃, followed by stabilization at 62℃ and 37.5℃. The standard operating mode for the circulating fan was 120 minutes of forward rotation followed by 120 minutes of reverse rotation.

[0157] During the later stages of temperature stabilization at 62℃, weighing monitoring showed that the upper layer of tobacco leaves had entered stage W5, the middle layer was close to stage W5, and some lower layer leaves were still in the W4-S1 range, indicating that the moisture migration of the midrib of the lower layer leaves was slightly delayed. The near-infrared predicted component coordination index was C2, and C3 was not observed.

[0158] The control system does not continue to increase the dry bulb temperature, but continues to maintain a stable temperature at 62℃ and 37.5℃; the dehumidification mode is adjusted to dehumidify for 5 minutes and stop for 25 minutes; the circulating fan is adjusted from rotating forward for 120 minutes and rotating backward for 120 minutes to rotating forward for 90 minutes and rotating backward for 90 minutes.

[0159] After adjustment, the moisture migration index of the lower layer tobacco leaves transitioned from W4-S1 to W5, and the difference in moisture migration between the upper, middle and lower layers narrowed, meeting the conditions for entering the later stage of temperature-limited drying.

[0160] h. Temperature-limited dry gluten later stage

[0161] The dry-bulb temperature was increased from 62℃ to 66℃, and the wet-bulb temperature was increased from 37.5℃ to 39℃, and then stabilized at 66℃ and 39℃. The standard operating mode for the circulating fan was 120 minutes of forward rotation and 120 minutes of reverse rotation.

[0162] During the later stage of temperature stabilization at 66℃, the weighing device showed that the overall water loss rate M had reached over 70%, but the water loss rate Vm of the representative tobacco leaves in the lower layer was still 0.38% / h, and the moisture migration index was W5-S1, indicating that the midrib was still slowly losing water and had not yet reached the termination condition of W5-S0; manual sampling showed that the midrib of the lower tobacco leaves still had toughness. The near-infrared predicted component coordination index was C2, and C3 did not appear.

[0163] The control system maintains the dry bulb temperature at 66℃ and prevents it from rising further; the wet bulb temperature is maintained at 39℃; the dehumidification mode is adjusted to dehumidify for 5 minutes and stop dehumidifying for 30 minutes to avoid continuous strong dehumidification in the later stage; the circulating fan is adjusted from rotating forward for 120 minutes and rotating backward for 120 minutes to rotating forward for 90 minutes and rotating backward for 90 minutes; an additional 5 hours of temperature stabilization is added under the temperature limit conditions.

[0164] After adjustment, the water loss rate Vm decreased to below 0.30% / h and remained stable for more than 1 hour, and the moisture migration index reached W5-S0; manual inspection showed that the main vein was completely dry. Heating was then stopped, and the product was removed from the oven after natural or controlled rehydration.

[0165] Comparative Example

[0166] The comparative example used the same source of fresh tobacco leaves, loading method, curing barn specifications, and heating method as the example, but did not utilize the real-time linkage control of appearance maturity index A, moisture migration index W, and component coordination index C. The comparative example was cured solely according to a conventional fixed temperature and humidity curve and manual observation; the circulating fan operated in a conventional fixed forward and reverse rotation mode, and dehumidification was mainly based on dry-bulb and wet-bulb temperatures and operator experience.

[0167] In the comparative example, the operator judged the yellowing of tobacco leaves, the collapse of the frame, the dryness of the roll and the main vein through the observation window, and carried out heating, stabilization and dehumidification according to the preset time and temperature and humidity nodes; the appearance maturity index A was not calculated based on the image recognition results, the moisture migration index W was not corrected in real time based on the weighing results, and the component coordination index C was not calculated based on the near-infrared spectroscopy results.

[0168] Table 4 Comparative Example of Conventional Baking Process Parameters

[0169] 30 30 0 —— 5 Heating rate: 1℃ / h for dry bulb, 0.8℃ / h for wet bulb 35 34 10 Stable temperature 6 Heating rate: 0.5℃ / h for dry bulb, 0.166℃ / h for wet bulb 38 35 20 Stable temperature 8 Heating rate: 0.5℃ / h for dry bulb, 0.125℃ / h for wet bulb 42 36 23 Stable temperature 8 Heating rate: 0.375℃ / h for dry bulb, 0.0625℃ / h for wet bulb 45 36.5 10 Stable temperature 6 Heating rate: 0.5℃ / h for dry bulb, 0.083℃ / h for wet bulb 48 37 18 Stable temperature 9 Heating rate: 0.667℃ / h for dry bulb, 0.11℃ / h for wet bulb 54 38 14 Stable temperature 8 Heating rate: 1℃ / h for dry bulb, 0.125℃ / h for wet bulb 62 39 2 Stable temperature 5 Heating rate: 0.8℃ / h for dry bulb, 0.2℃ / h for wet bulb 66 40 45.8 Stable temperature

[0170] Baking effect analysis of the example

[0171] After the curing of the examples and comparative examples, the economic traits, appearance quality, sensory quality and main chemical components of the cured tobacco leaves were measured. The results are shown in Tables 5, 6 and 7.

[0172] Table 5. Economic traits of flue-cured tobacco leaves after different treatments

[0173] Example 53.17 27.58 Comparative Example 45.72 25.19

[0174] As shown in Table 5, the tobacco leaves treated with the precise curing method of this invention exhibit better economic characteristics than the comparative example. The proportion of high-grade tobacco after treatment in this example reached 53.17%, an increase of 7.45 percentage points (16.30%) compared to the 45.72% of the comparative example; the average price of the tobacco leaves increased from RMB 25.19 / kg to RMB 27.58 / kg, an increase of RMB 2.39 / kg (9.49%). This demonstrates that the present invention, through real-time monitoring and phased precise control of the appearance maturity index, moisture migration index, and component coordination index, can promote the coordinated processes of yellowing, water loss, color fixing, and drying of tobacco leaves, reduce the formation of low-grade defective tobacco, and improve the grade structure and average economic price of the cured tobacco leaves.

[0175] Table 6 Sensory quality of flue-cured tobacco leaves after different treatments

[0176] Fragrance quality (9 points) 7.8 6.8 Aroma intensity (9 points) 7.6 6.5 Aftertaste (9 points) 7.5 6.7 Mixed gases (9 points) 7.2 6.2 Irritating (9 points) 7.1 6.5 Flammability (5 points) 3.5 3.1 Gray (5 points) 3.9 3.3 Total score (55 points) .1

[0177] As shown in Table 6, the sensory quality of the tobacco leaves treated with the precise roasting method of this invention is superior to that of the comparative example. Compared with the comparative example, the total sensory score of the example reached 44.6 points, which is 5.5 points higher than the 39.1 points of the comparative example, representing an improvement of 14.07%.

[0178] Analysis of individual indicators shows that the aroma score of the example reached 7.8 points, which is 1.0 point higher than that of the comparative example, representing an increase of 14.71%; the aroma quantity score reached 7.6 points, which is 1.1 points higher than that of the comparative example, representing an increase of 16.92%; and the aftertaste score reached 7.5 points, which is 0.8 points higher than that of the comparative example, representing an increase of 11.94%.

[0179] Regarding off-odors and irritation, the off-odor score of the embodiment reached 7.2 points, an increase of 1.0 point (16.13%) compared to the comparative example; the irritation score reached 7.1 points, an increase of 0.6 points (9.23%) compared to the comparative example. Combustion and ash scores reached 3.5 and 3.9 points respectively, increases of 0.4 and 0.6 points respectively compared to the comparative example, representing increases of 12.90% and 18.18% respectively. The results indicate that this invention, through real-time monitoring and phased precise control of the appearance maturity index, moisture migration index, and component coordination index, can improve the aroma performance of tobacco leaves, enhance aftertaste comfort, reduce off-odors and irritation, thereby improving the overall sensory evaluation quality of cured tobacco leaves.

[0180] Table 7. Content of main chemical components in flue-cured tobacco leaves after different treatments

[0181] Total sugar (%) 25.40 28.10 Reducing sugar (%) 22.10 25.50 Total nitrogen (%) 2.01 1.78 Nicotine (%) 2.20 2.75 Potassium (%) 2.36 2.04 chlorine(%) 0.32 0.42 Sugar-base ratio 11.55 10.22 Nitrogen-base ratio 0.91 0.65

[0182] As shown in Table 7, the main chemical components of tobacco leaves treated with the precise curing method of this invention are more harmonious. The total sugar, reducing sugar, and nicotine contents of the example were 25.40%, 22.10%, and 2.20%, respectively, all lower than the comparative examples' 28.10%, 25.50%, and 2.75%. The sugar-to-nicotine ratio and nitrogen-to-nicotine ratio were 11.55 and 0.91, respectively, higher than the comparative examples' 10.22 and 0.65, indicating that the method of this invention is beneficial for improving the sugar-to-nicotine and nitrogen-to-nicotine balance of tobacco leaves. The potassium content of the example was 2.36%, higher than the comparative example's 2.04%; the chlorine content was 0.32%, lower than the comparative example's 0.42%, and the potassium-to-chlorine ratio increased from 4.86 in the comparative example to 7.38, which is beneficial for improving the combustibility and ash appearance of the tobacco leaves. In summary, the method of this invention can improve the harmony of the main chemical components of cured tobacco leaves while enhancing economic traits and sensory quality, providing an intrinsic component basis for improving the sensory evaluation quality of tobacco leaves.

[0183] In summary, this invention constructs a precise tobacco curing state identification system composed of an appearance maturity index (A), a moisture migration index (W), and a component coordination index (C). This system enables dynamic identification of tobacco leaf color changes, water loss processes, and the coordination state of quality-related components. Based on this identification, the dry-bulb temperature, wet-bulb temperature, heating rate, dehumidification method, temperature stabilization time, and forward / reverse rotation parameters of the circulating fan at each curing stage are adjusted. This makes the processes of yellowing, water loss, color fixation, drying, and stabilization of tobacco leaves more coordinated with the curing environment. Results show that after treatment using this method, the proportion of high-grade tobacco and the average economic price are higher than the control group, and the overall sensory evaluation score is improved. Simultaneously, the sugar-alkali ratio, nitrogen-alkali ratio, and potassium-chlorine ratio of the tobacco leaves are improved, and the coordination of major chemical components is enhanced. Therefore, this invention can reduce the formation of low-grade defective tobacco, improve the sensory quality and intrinsic quality of tobacco leaves, thereby improving the quality and economic benefits of tobacco curing.

[0184] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A precise curing method for improving the sensory evaluation quality of tobacco leaves and increasing the percentage of high-grade tobacco, characterized in that, The method is implemented in a bidirectional airflow circulating drying oven and includes the following steps: S1. Establish a state identification indicator system and phased target values. The tobacco leaves to be cured are classified and a state identification index system is established. This system includes the appearance maturity index A, the moisture migration index W, and the component coordination index C. At the same time, the target values ​​of the above indicators (A / W / C) for each curing stage are set, as well as the corresponding benchmark curing parameters. S2: Collect tobacco leaf curing status information Monitoring points are set up on each floor of the drying room to collect multi-dimensional data in real time. The collected data includes: image data, weight data, near-infrared spectral data, dry and wet bulb temperatures, and fan operation data. After being measured and recorded at a unified time, the data is synchronously transmitted to the computing unit. S3: Multi-information fusion recognition and judgment The collected multi-source data is preprocessed and analyzed to quantify the current baking status: Background removal, white balance correction, and color segmentation are performed on the image, and the appearance maturity index A is calculated. The weight data is smoothed, the water loss rate and water loss speed are calculated, and the water migration index W is determined. The spectral data is preprocessed and input into the calibration model to predict the conventional chemical components of tobacco, and then the component coordination index C is calculated. S4: State Determination and Dynamic Feedback The calculated current state indicators (A, W, C) are compared with the current stage switching conditions set in S1 to determine the appropriate outcome. If the condition is "yes", then if A, W, and C meet the switching conditions for the current stage, then proceed to step S4-2. S4-2 Proceed to the next baking stage: Switch to the next baking stage and execute the baking process control parameters set for this stage; then continue to step S2 for real-time monitoring; If the condition is "No": If the switching condition is not met, proceed to step S4-1; S4-1 Dynamic Feedback Control: Based on the deviations of A, W, C from the stage target values, identify the current abnormal state; accordingly adjust the heating rate, wet-bulb temperature, dehumidification method and dehumidification intensity, temperature stabilization time, and forward and reverse rotation time of the circulating fan, and feed the adjusted parameters back to step S2 for continued monitoring and judgment, forming a closed-loop control.

2. The precise baking method according to claim 1, characterized in that, The appearance maturity index A is determined as follows: Background removal, white balance correction, and color segmentation were performed on representative tobacco leaf images to obtain the areas of yellow regions (Sy), green regions (Sg), dark regions (Sd), and brown regions (Sb), and the effective leaf area was calculated. The yellowing ratio H = Sy / S × 100% and the defect color ratio D = (Sd + Sb) / S × 100%; When D > 5%, A is determined to be A0; When D≤5% and H<25%, A is determined to be A1; When D≤5% and 25%≤H<50%, A is judged as A2; when D≤5% and 50%≤H<80%, A is judged as A3. When D≤5% and 80%≤H<95%, A is judged as A4; when D≤5% and H≥95%, A is judged as A5. Among them, A0 is the priority judgment state for defect color risk and does not participate in the ranking of yellowing maturity levels of A1 to A5; when D>5%, it is given priority to be judged as A0; When the appearance maturity index A is determined to be A0, the yellowing ratio H is not used as the basis for entering the next heating stage. Instead, at least one of the following control measures is implemented: pausing heating, reducing wet-bulb temperature, increasing intermittent dehumidification, or shortening the unidirectional operation time of the circulating fan.

3. The precise baking method according to claim 2, characterized in that, The water migration index W is determined by the water loss rate M and the water loss speed Vm, where M = (W0 - Wt) / W0 × 100% and Vm = (Mt - Mt-1) / Δt. W0 is the initial net weight of representative tobacco leaves at the start of curing, Wt is the net weight of representative tobacco leaves at the current monitoring time, Mt is the water loss rate at the current monitoring time, Mt-1 is the water loss rate at the previous monitoring time, and Δt is the interval between two adjacent weighing monitoring. The moisture migration index W includes cumulative water loss stages W1, W2, W3, W4, and W5, divided according to the water loss rate M, and water loss rate states S0, S1, and S2, divided according to the water loss rate Vm. S0 indicates slow water loss, S1 indicates appropriate water loss, and S2 indicates fast water loss.

4. The precise baking method according to claim 1, characterized in that, The cumulative water loss stages are as follows: W1 corresponds to M < 10%, W2 corresponds to 10% ≤ M < 20%, W3 corresponds to 20% ≤ M < 40%, W4 corresponds to 40% ≤ M < 70%, and W5 corresponds to M ≥ 70%. Furthermore, in stage W1, S1 corresponds to 0.1% / h ≤ Vm ≤ 0.5% / h; in stage W2, S1 corresponds to 0.3% / h ≤ Vm ≤ 0.8% / h; in stage W3, S1 corresponds to 0.5% / h ≤ Vm ≤ 1.2% / h; in stage W4, S1 corresponds to 0.4% / h ≤ Vm ≤ 1.5% / h; and in stage W5, S1 corresponds to 0.3% / h ≤ Vm ≤ 0.8% / h. Water loss below the corresponding lower limit of S1 is classified as S0, and water loss above the corresponding upper limit of S1 is classified as S2.

5. In the precise baking method according to claim 4, the component coordination index C is calculated from the predicted total sugar value TS, the predicted reducing sugar value RS, the predicted nicotine value NIC, the predicted total nitrogen value TN, and the predicted moisture value WN obtained by near-infrared spectroscopy, and its calculation formula is: ； in, Gt is the target sugar-alkali ratio for the current baking stage, Rt is the target proportion of reducing sugar to total sugar for the current baking stage, Nt is the target nitrogen-alkali ratio for the current baking stage, and Wc is the target moisture value for the current baking stage. When C≤0.20, it is determined as C1; when 0.20<C≤0.35, it is determined as C2; when C>0.35, it is determined as C3.

6. The precise baking method according to claim 1, characterized in that, The image data, weight data, near-infrared spectral data, dry and wet bulb temperatures, and fan operation data are collected by image acquisition devices, weighing devices, near-infrared spectral acquisition devices, and temperature and humidity sensors installed at monitoring points on each floor of the drying room. After the data is measured and recorded at a unified time, it is synchronously transmitted to the computing unit. The calculation unit outputs the calculation results of A, W, and C to the temperature and humidity control module, the dehumidification control module, and the circulating fan control module.

7. The precise baking method according to claim 6, characterized in that, The baking stages sequentially include the preheating equilibrium period, the low-temperature and high-humidity yellowing period, the yellowing and water loss coordination period, the early stage of color stabilization and fixing, the late stage of color stabilization and fixing, the early stage of aroma stabilization and drying, the middle stage of aroma stabilization and drying, and the late stage of temperature-limited drying. The transition conditions for each baking stage are as follows: During the preheating equilibrium period, if A is A1 to A2, W is W1-S1, and C is C1 or C2, the low-temperature and high-humidity yellowing period begins; during the low-temperature and high-humidity yellowing period, if A is A3, W is W2-S1, and C is C1 or C2, the yellowing and water loss coordination period begins; during the yellowing and water loss coordination period, if A is A4, W is W3-S1, and C is C1 or C2, the early stage of color stabilization and fixing begins; during the early stage of color stabilization and fixing, if A is A4 to A5 and not A0, W transitions from W3-S1 to W4-S1, and C is C1 or C2, the color stabilization and fixing period begins. Later stage; When the color stabilization and fixing stage meets the following conditions, A is A5 and not A0, W is W4-S1 and C is C1 or C2, it enters the early stage of stabilizing aroma and drying the core; When the color stabilization and fixing stage meets the following conditions, A remains A5 and not A0, W remains W4-S1, C is C1 or C2, and the temperature is stabilized at 54℃ for a preset time or the near-infrared predicted moisture value WN reaches the target moisture range for this stage, it enters the middle stage of stabilizing aroma and drying the core; When the color stabilization and fixing stage meets the following conditions, A remains A5 and not A0, W enters W5 and C is C1 or C2, it enters the later stage of temperature-limited drying the core; When the temperature-limited drying stage meets the following conditions, W is W5-S0 and lasts for more than 1 hour, the near-infrared predicted moisture value WN reaches the endpoint moisture threshold or the main vein dryness meets the requirements for exiting the oven, and C is not C3, heating is stopped and it enters the rehydration and exiting the oven stage.

8. The precise baking method according to claim 7, characterized in that, The forward and reverse rotation time of the circulating fan is set according to the baseline value of the baking stage. When the difference between the appearance maturity index A or moisture migration index W between different layers is detected to be more than one level, the one-way operation time of the circulating fan is shortened by 10 to 30 minutes to reduce the differences in heating, humidification and water loss between tobacco leaves in different layers of the curing barn.

9. The precise baking method according to claim 8, characterized in that, When the appearance maturity index A reaches the stage target and the moisture migration index W is in the S0 state, reduce the wet-bulb temperature, increase intermittent dehumidification, or extend the stable temperature period; when the moisture migration index W reaches the stage target or is in the S2 state and the appearance maturity index A does not reach the stage target, reduce the heating rate, reduce dehumidification, or extend the stable temperature period; when the component coordination index C is C3, suspend heating or reduce the heating rate, and reduce continuous dehumidification, extend the stop-dehumidification time, or extend the stable temperature period.

10. The precise baking method according to claim 9, characterized in that, In the later stage of temperature-limited drying, when the moisture migration index W is W5-S1 or the lower layer of tobacco leaves and the main vein slightly moist tobacco leaves have not reached W5-S0, the dry bulb temperature is maintained at 66℃ without further increase, and the main vein is dried by extending the temperature stabilization period, reducing continuous dehumidification and shortening the one-way operation time of the circulating fan; when the moisture migration index W reaches W5-S0 and stabilizes, and the near-infrared predicted moisture value WN reaches the endpoint moisture threshold or the main vein dryness meets the requirements for exiting the furnace, heating is stopped and natural rehumidification or controlled moisture rehumidification is carried out before exiting the furnace.

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