A method for characterizing the moisture absorption characteristics of tobacco leaves

Abstract

The application discloses a kind of tobacco hygroscopicity characterization method, belong to tobacco processing and storage technical field, comprising the following steps: S1, sample preparation;S2, experimental condition setting;S3, dynamic moisture absorption monitoring;S4, multi-parameter calculation;S5, moisture absorption isotherm fitting;S6, temperature sensitivity analysis;S7, result verification and characterization: the repeatability of data is verified by parallel experiment, and output moisture absorption kinetics curve, moisture absorption isotherm and characteristic parameter report.The application can completely describe the "static balance-dynamic process-environment response" characteristics of tobacco hygroscopicity by constructing the multidimensional parameter system of "moisture absorption amount-moisture absorption rate-diffusion capacity-humidity sensitivity", solve the problem of single parameter in traditional method, clear sample pretreatment, humidity control precision, humidity and monitoring interval, ensure that experimental data of different laboratories and different batches are comparable, solve the problem of poor repeatability of traditional method, and reduce the relative standard deviation of data.

Description

Technical Field

[0001] This invention belongs to the field of tobacco processing and storage technology, specifically referring to a method for characterizing the hygroscopic properties of tobacco leaves. Background Technology

[0002] Tobacco leaves are a porous agricultural product rich in cellulose, pectin, and protein. Their hygroscopic properties directly affect the risk of mold growth during storage, the adaptability to processing techniques, and the sensory quality of the final product. Current methods for characterizing the hygroscopic properties of tobacco leaves have the following key shortcomings, making it difficult to meet the needs of precision production:

[0003] The parameter system is too simplistic and the characterization is incomplete: Traditional methods only focus on the "equilibrium moisture content" (i.e., the moisture content when tobacco leaves reach hygroscopic equilibrium with the environment), ignoring kinetic parameters such as the moisture absorption rate (reflecting the speed of moisture absorption) and the effective moisture diffusion coefficient (reflecting the ability of moisture to be transferred within the tobacco leaf). This fails to fully describe the "quantity-rate-effectiveness" relationship of the moisture absorption process. For example, different varieties of tobacco leaves may have similar equilibrium moisture contents, but their moisture absorption rates differ significantly, leading to different risks of mold growth during actual storage. Traditional methods cannot distinguish these differences.

[0004] Non-standardized experimental conditions and poor data repeatability: Existing methods lack unified standards for sample pretreatment (such as tobacco leaf particle size and initial drying conditions). Some studies directly use whole tobacco leaf samples (with uneven thickness and large differences in specific surface area) or arbitrary initial drying conditions (such as natural air drying at room temperature), resulting in the inability to compare experimental data from different laboratories. At the same time, the temperature and humidity control precision of constant temperature and humidity chambers is low, which easily introduces systematic errors.

[0005] In summary, existing methods, due to their limited parameters, non-standard conditions, low model accuracy, and lack of validation, cannot comprehensively and accurately characterize the hygroscopic properties of tobacco leaves. There is an urgent need for a standardized, multi-dimensional, and highly reliable characterization method. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention provides a method for characterizing the hygroscopic properties of tobacco leaves, which effectively solves the problems currently on the market.

[0007] The technical solution adopted in this invention is as follows: This invention proposes a method for characterizing the hygroscopic properties of tobacco leaves, comprising the following steps:

[0008] S1. Sample Preparation: Select tobacco leaves of the same variety and grade, remove the midrib, take the leaf pulp, crush to the preset particle size, and dry to the initial dry basis. Record the initial mass. ;

[0009] S2. Experimental conditions: The temperature of the constant temperature and humidity chamber is controlled at 10-40℃ and the relative humidity is controlled at 30%-90%. At least 3 sets of temperature and humidity gradients are set.

[0010] S3. Dynamic moisture absorption monitoring: Place the initial dry basis sample on a high-precision electronic balance inside a constant temperature and humidity chamber, and record the sample mass every 5-15 minutes. The mass is recorded until the rate of change of mass is ≤0.01% for three consecutive records. This mass is then recorded as the equilibrium mass. ;

[0011] S4. Multi-parameter calculation: Calculate instantaneous moisture absorption based on monitoring data. equilibrium moisture content Instantaneous moisture absorption rate and effective moisture diffusion coefficient ;

[0012] S5. Moisture absorption isotherm fitting: The GAB model was used to fit the moisture absorption isotherm under different relative humidities. The data were fitted to obtain the saturated water content of the monolayer. Adsorption heat related constant and the multilayer adsorption heat-related constant K;

[0013] S6. Temperature Sensitivity Analysis: The Arrhenius equation was used to analyze the temperature sensitivity at different temperatures. The data were fitted to obtain the activation energy of water diffusion. ;

[0014] S7. Result Verification and Characterization: Verify the repeatability of the data through parallel experiments, and output the hygroscopic kinetic curve, hygroscopic isotherm and characteristic parameter report.

[0015] Further, in step S1, the preset particle size is 40-60 mesh, that is, 0.25-0.42 mm. The preparation conditions for the initial dry state are: drying in a constant temperature and humidity chamber at 40℃ and 20% relative humidity for 48 hours until the mass change rate is ≤0.01% / h.

[0016] Furthermore, in step S2, the temperature and humidity gradients include temperature groups of 20℃, 25℃, and 30℃, and relative humidity groups of 40%, 60%, and 80%; the temperature accuracy of the constant temperature and humidity chamber is ±0.5℃, the relative humidity accuracy is ±2%, and it has a built-in wind speed control module with a stable wind speed of 0.5m / s.

[0017] Furthermore, in step S4, the instantaneous moisture absorption... The calculation formula is: ,in Let be the sample mass at time t. Initial dry basis sample mass; equilibrium moisture content The calculation formula is: ,in This represents the sample mass at moisture absorption equilibrium.

[0018] Furthermore, in step S4, the instantaneous moisture absorption rate The calculation formula is: ,in The time interval for quality recording is 10 minutes; effective moisture diffusion coefficient. Based on a simplified derivation of Fick's second law, the calculation formula is: ,in for The slope of the linear fit. The average thickness of the sample after it is laid flat is 0.5-1mm.

[0019] Furthermore, in step S5, the formula for the GAB model is: ,in The relative humidity is used, converted to a decimal before substitution; nonlinear least squares method is used for fitting, and the goodness of fit is... ≥0.98.

[0020] Furthermore, in step S6, the formula for the Arrhenius equation is: ,in Here, is the pre-exponential factor, and R is the ideal gas constant, which is 8.314 J / (mol·K). Absolute temperature =273.15+t, where t is the experimental temperature; through Linear fitting calculation goodness of fit ≥0.95.

[0021] Furthermore, in step S7, three groups of parallel samples are set up for the parallel experiment, and the relative standard deviation (RSD) of each characteristic parameter is ≤5%; the characteristic parameter report includes , Maximum instantaneous moisture absorption rate Monolayer saturated water content Adsorption heat related constant The correlation constants K and Ea for multilayer adsorption heat.

[0022] The beneficial effects achieved by the present invention using the above structure are as follows: It constructs a multi-dimensional parameter system of "hygroscopic capacity - hygroscopic rate - diffusion capacity - temperature and humidity sensitivity", which can completely describe the "static equilibrium - dynamic process - environmental response" characteristics of tobacco leaf hygroscopicity, solve the problem of single parameters in traditional methods, clarify the sample pretreatment, temperature and humidity control accuracy, humidity and monitoring interval, ensure the comparability of experimental data from different laboratories and different batches, solve the problem of poor repeatability in traditional methods, and reduce the relative standard deviation of data. Attached Figure Description

[0023] Figure 1 The flowchart of a method for characterizing the hygroscopic properties of tobacco leaves proposed in this invention Figure 1 ;

[0024] Figure 2 The flowchart of a method for characterizing the hygroscopic properties of tobacco leaves proposed in this invention Figure 2 .

[0025] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0027] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0028] like Figures 1-2 As shown, this invention proposes a method for characterizing the hygroscopic properties of tobacco leaves, comprising the following steps:

[0029] S1. Sample Preparation: Select tobacco leaves of the same variety and grade, remove the midrib, take the leaf pulp, crush to the preset particle size, and dry to the initial dry basis. Record the initial mass. ;

[0030] S2. Experimental conditions: The temperature of the constant temperature and humidity chamber is controlled at 10-40℃ and the relative humidity is controlled at 30%-90%. At least 3 sets of temperature and humidity gradients are set.

[0031] S3. Dynamic moisture absorption monitoring: Place the initial dry basis sample on a high-precision electronic balance inside a constant temperature and humidity chamber, and record the sample mass every 5-15 minutes. The mass is recorded until the rate of change of mass is ≤0.01% for three consecutive records. This mass is then recorded as the equilibrium mass. ;

[0032] S4. Multi-parameter calculation: Calculate instantaneous moisture absorption based on monitoring data. equilibrium moisture content Instantaneous moisture absorption rate and effective moisture diffusion coefficient ;

[0033] S5. Moisture absorption isotherm fitting: The GAB model was used to fit the moisture absorption isotherm under different relative humidities. The data were fitted to obtain the saturated water content of the monolayer. Adsorption heat related constant and the multilayer adsorption heat-related constant K;

[0034] S6. Temperature Sensitivity Analysis: The Arrhenius equation was used to analyze the temperature sensitivity at different temperatures. The data were fitted to obtain the activation energy of water diffusion. ;

[0035] S7. Result Verification and Characterization: Verify the repeatability of the data through parallel experiments, and output the hygroscopic kinetic curve, hygroscopic isotherm and characteristic parameter report.

[0036] In step S1, the preset particle size is 40-60 mesh, i.e., 0.25-0.42 mm. The preparation conditions for the initial dry state are: drying in a constant temperature and humidity chamber at 40°C and 20% relative humidity for 48 h until the mass change rate is ≤0.01% / h.

[0037] In step S2, the temperature and humidity gradients include temperature groups of 20℃, 25℃, and 30℃, and relative humidity groups of 40%, 60%, and 80%. The temperature accuracy of the constant temperature and humidity chamber is ±0.5℃, the relative humidity accuracy is ±2%, and it has a built-in wind speed control module with a stable wind speed of 0.5m / s.

[0038] In step S4, instantaneous moisture absorption The calculation formula is: ,in Let be the sample mass at time t. Initial dry basis sample mass; equilibrium moisture content The calculation formula is: ,in This represents the sample mass at moisture absorption equilibrium.

[0039] In step S4, the instantaneous moisture absorption rate The calculation formula is: ,in The time interval for quality recording is 10 minutes; effective moisture diffusion coefficient. Based on a simplified derivation of Fick's second law, the calculation formula is: ,in for The slope of the linear fit. The average thickness of the sample after it is laid flat is 0.5-1mm.

[0040] In step S5, the formula for the GAB model is: ,in The relative humidity is used, converted to a decimal before substitution; nonlinear least squares method is used for fitting, and the goodness of fit is... ≥0.98.

[0041] In step S6, the formula for the Arrhenius equation is: ,in Here, is the pre-exponential factor, and R is the ideal gas constant, which is 8.314 J / (mol·K). Absolute temperature =273.15+t, where t is the experimental temperature; through Linear fitting calculation goodness of fit ≥0.95.

[0042] In step S7, three parallel groups of samples are set up for the parallel experiment, and the relative standard deviation (RSD) of each characteristic parameter is ≤5%; the characteristic parameter report includes , Maximum instantaneous moisture absorption rate Monolayer saturated water content Adsorption heat related constant The correlation constants K and Ea for multilayer adsorption heat.

[0043] Sample Preparation (S1): Standardized pretreatment to ensure sample consistency. Sampling: Select tobacco leaves of the same variety and grade (e.g., Grade 3 of Central Orange Yellow), remove the midrib (the hygroscopic properties of the midrib differ significantly from those of the leaf mesophyll), and take the leaf mesophyll portion; Grinding: Grind the leaf mesophyll to 40-60 mesh (particle size 0.25-0.42mm) using a high-speed grinder to ensure uniform sample surface area (avoiding uneven thickness of whole tobacco leaves); Initial drying: Place the ground sample in a constant temperature and humidity chamber (40℃, relative humidity (20%)) for 48 hours, record the mass every 12 hours until two consecutive mass change rates are ≤0.01% / h, obtaining the initial dry basis sample. Record the initial mass using a high-precision electronic balance (accuracy 0.0001g). .

[0044] Experimental conditions (S2): Gradient temperature and humidity to cover actual application scenarios. Based on the actual storage (20-30℃, 40%-80%RH) and processing (30-40℃, 30%-60%RH) environments of tobacco leaves, 3-5 sets of temperature and humidity gradients were set, with typical gradients as follows:

[0045] Temperature range: 20℃, 25℃, 30℃ (covering room temperature storage);

[0046] Relative humidity groups: 40%, 60%, 80% (covering low to medium-high humidity);

[0047] The temperature and humidity chamber parameters are controlled as follows: temperature accuracy ±0.5℃, relative humidity accuracy ±2%, and a built-in wind speed control module (wind speed 0.5m / s) to avoid local water vapor concentration differences around the sample.

[0048] Dynamic moisture absorption monitoring (S3): Real-time recording to capture the entire moisture absorption process.

[0049] The initial dry basis sample (mass) Place the contents into a quartz crucible (50mm in diameter and 10mm in height), spread them evenly to a thickness of 0.5-1mm, and place them on a high-precision electronic balance inside a constant temperature and humidity chamber.

[0050] Quality Recording: Sample quality is automatically recorded every 10 minutes. In the initial stage of moisture absorption (first 2 hours), the interval can be shortened to 5 minutes per cycle (capturing the rapid moisture absorption phase), until the mass change rate recorded for three consecutive times is ≤0.01% (determined to have reached moisture absorption equilibrium). Record the equilibrium mass. .

[0051] Multi-parameter calculation (S4): Quantitative derivation, constructing a "quantity-speed-effect" parameter system

[0052] Instantaneous moisture absorption The formula reflects the degree of moisture absorption of tobacco leaves at a given moment. (Dry basis percentage);

[0053] equilibrium moisture content : Reflects the maximum moisture absorption capacity of tobacco leaves, the formula is: ;

[0054] Instantaneous moisture absorption rate The formula reflects the speed of the moisture absorption process. ( =10min, unit % / min), where (Maximum instantaneous moisture absorption rate) corresponds to the rapid adsorption stage in the initial stage of moisture absorption;

[0055] Effective moisture diffusion coefficient This reflects the efficiency of water transfer within the tobacco leaf, and is derived using a simplified derivation based on Fick's second law:

[0056] Initial stage of moisture absorption ( <0.6), the solution of Fick's second law series simplifies to ;

[0057] By performing a linear fit with t, the slope is obtained. ;

[0058] Substitute into the formula calculate (L is the average thickness of the sample, in meters).

[0059] Hygroscopic isotherm fitting (S5): High-precision model covering the entire humidity range

[0060] The GAB model (suitable for 0-90% RH, with higher fitting accuracy than the BET model) was used to fit different RH levels. The data is fitted, and the model formula is as follows: ;

[0061] Meaning of fitting parameters: (Monolayer saturated moisture content) reflects the maximum monolayer moisture that the tobacco leaf surface can adsorb (the core indicator of moisture absorption capacity), C (adsorption heat constant) reflects the initial moisture absorption capacity (the larger the C, the faster the moisture absorption under low humidity), and K (multilayer adsorption heat constant) reflects the multilayer adsorption stability (usually K≈1).

[0062] Fitting tools: Origin or Matlab software is used, and nonlinear least squares fitting is employed to ensure goodness of fit. .

[0063] Results Validation and Characterization (S7): Repeatability validation, output standardized report.

[0064] Parallel experiments: Set up 3 parallel samples under each temperature and humidity condition, calculate the relative standard deviation (RSD) of each characteristic parameter, and require RSD ≤ 5% (to ensure data repeatability);

[0065] Output results:

[0066] Curves: Plot the hygroscopic kinetic curve (Mt-t), hygroscopic isotherm (Me-RH), and Arrhenius curve (lnDeff-1 / T);

[0067] Report: Compiled by Me, Deff, Characteristic parameters such as Mm, C, K and Ea are used to form a complete characterization report of the moisture absorption properties of tobacco leaves.

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] 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.

[0070] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention; the actual structure is not limited thereto. In conclusion, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the spirit of the invention, such designs should fall within the protection scope of the present invention.

Claims

1. A method for characterizing the hygroscopic properties of tobacco leaves, characterized in that: Includes the following steps: S1. Sample Preparation: Select tobacco leaves of the same variety and grade, remove the midrib, take the leaf pulp, crush to the preset particle size, and dry to the initial dry basis. Record the initial mass. ; S2. Experimental conditions: The temperature of the constant temperature and humidity chamber is controlled at 10-40℃ and the relative humidity is controlled at 30%-90%. At least 3 sets of temperature and humidity gradients are set. S3. Dynamic moisture absorption monitoring: Place the initial dry basis sample on a high-precision electronic balance inside a constant temperature and humidity chamber, and record the sample mass every 5-15 minutes. The mass is recorded until the rate of change of mass is ≤0.01% for three consecutive records. This mass is then recorded as the equilibrium mass. ; S4. Multi-parameter calculation: Calculate instantaneous moisture absorption based on monitoring data. equilibrium moisture content Instantaneous moisture absorption rate and effective moisture diffusion coefficient ; S5. Moisture absorption isotherm fitting: The GAB model was used to fit the moisture absorption isotherm under different relative humidities. The data were fitted to obtain the saturated water content of the monolayer. Adsorption heat related constant and the multilayer adsorption heat-related constant K; S6. Temperature Sensitivity Analysis: The Arrhenius equation was used to analyze the temperature sensitivity at different temperatures. The data were fitted to obtain the activation energy of water diffusion. ; S7. Result Verification and Characterization: Verify the repeatability of the data through parallel experiments, and output the hygroscopic kinetic curve, hygroscopic isotherm and characteristic parameter report.

2. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 1, characterized in that: In step S1, the preset particle size is 40-60 mesh, i.e., 0.25-0.42 mm. The preparation conditions for the initial dry state are: drying in a constant temperature and humidity chamber at 40°C and 20% relative humidity for 48 h until the mass change rate is ≤0.01% / h.

3. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 2, characterized in that: In step S2, the temperature and humidity gradients include temperature groups of 20℃, 25℃, and 30℃, and relative humidity groups of 40%, 60%, and 80%. The temperature accuracy of the constant temperature and humidity chamber is ±0.5℃, the relative humidity accuracy is ±2%, and it has a built-in wind speed control module with a stable wind speed of 0.5m / s.

4. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 3, characterized in that: In step S4, instantaneous moisture absorption The calculation formula is: ,in Let be the sample mass at time t. Initial dry basis sample mass; equilibrium moisture content The calculation formula is: ,in This represents the sample mass at moisture absorption equilibrium.

5. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 4, characterized in that: In step S4, the instantaneous moisture absorption rate The calculation formula is: ,in The time interval for quality recording is 10 minutes; effective moisture diffusion coefficient. Based on a simplified derivation of Fick's second law, the calculation formula is: ,in for The slope of the linear fit. The average thickness of the sample after it is laid flat is 0.5-1mm.

6. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 5, characterized in that: In step S5, the formula for the GAB model is: ,in The relative humidity is used, converted to a decimal before substitution; nonlinear least squares method is used for fitting, and the goodness of fit is... ≥0.

98.

7. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 6, characterized in that: In step S6, the formula for the Arrhenius equation is: ,in Here, is the pre-exponential factor, and R is the ideal gas constant, which is 8.314 J / (mol·K). Absolute temperature =273.15+t, where t is the experimental temperature; through Linear fitting calculation goodness of fit ≥0.

95.

8. The method for characterizing the hygroscopic properties of tobacco leaves according to claim 7, characterized in that: In step S7, three parallel groups of samples are set up for the parallel experiment, and the relative standard deviation (RSD) of each characteristic parameter is ≤5%; the characteristic parameter report includes , Maximum instantaneous moisture absorption rate Monolayer saturated water content Adsorption heat related constant The correlation constants K and Ea for multilayer adsorption heat.

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