A method for determining the stem content in cut tobacco based on compression rheology

Abstract

A method for determining the content of stems in tobacco based on compression rheology, using a tobacco compression rheometer, selecting certain compression conditions, obtaining stress relaxation curves of several tobacco samples with known stem content, then using a five-element generalized Maxwell model to process and fit the obtained data, finding the equilibrium stress value of the samples under certain conditions, then processing and linearly fitting the obtained data to obtain a standard curve equation of the stem content, then using the above-mentioned tester to test unknown samples, and substituting the obtained data into the equation to realize the determination of the stem content in a certain tobacco sample. The invention principle lies in: using the difference in stress relaxation behavior caused by the difference in mechanical properties between leaf tobacco and stem tobacco, thereby obtaining the stress relaxation curves of different samples under the set conditions using the above-mentioned tester, and finally obtaining the stem content by analyzing the difference.

Description

Technical Field

[0001] This invention relates to a method for determining the stem content in tobacco shreds based on compression rheology. Specifically, compression conditions are selected in a tobacco rheology tester, and stress relaxation curves of the samples are obtained during the process. By analyzing the differences in stress relaxation curves of different tobacco shred samples, the stem content in the tobacco shreds is obtained. This method belongs to the field of cigarette and cigarette product quality testing. Background Technology

[0002] Cigarette blend tobacco is generally composed of leaf tobacco, stem tobacco, expanded tobacco, and reconstituted tobacco. The stability of the content of these four components has a significant impact on the quality and smoking experience of cigarette products. Among them, stem tobacco plays an important role in improving cigarette draw resistance, reducing the harmfulness of cigarettes, improving cigarette smoke quality, and increasing raw material utilization. Therefore, how to accurately measure the blending ratio of stem tobacco to improve the blending effect of cigarette formulation is a technical challenge in tobacco processing.

[0003] A comprehensive literature review revealed that when a small proportion of stems is added to cigarette formulations, the theoretical ratio of stems often differs significantly from actual measurements, and the stems are unevenly distributed. This results in unstable internal quality within the same batch of cigarettes, affecting their sensory quality. Currently, there are no unified standards for the determination and evaluation of stem content in tobacco shreds, both domestically and internationally. Existing methods mainly evaluate the stem blending ratio based on physical density, tobacco chemical characteristics, and tobacco pyrolysis characteristics. Patent application number 201210324792.9 discloses a method for determining the proportion of stems in tobacco shreds. This method uses density differences and organic solvents to separate stems from tobacco shreds, then dries and weighs them to calculate the stem proportion. However, in an industry where stems are increasingly fibrous and their appearance is resembling leaf shreds, the organic solvents used in this patent, such as n-hexane, are no longer sufficient to accurately distinguish the density differences between stems and leaves. Patent application number 201410448180.X discloses a "method for determining the proportion of stems in tobacco shreds based on computer vision." This method uses an image acquisition system to collect images of each component in the tobacco shreds to be tested, then obtains the image features of each component and calculates the feature data of the stems, establishing a feature database. Based on the correlation calculation results, the stem components are analyzed and identified. A sorting system then sorts out the stems in the tobacco shreds to be tested, weighs them, and calculates the proportion of stem components. This method yields a high accuracy in determining the proportion of stem components, but the modeling process requires a large number of samples, and remodeling is necessary when the morphology and structure of the stems change, making the method inflexible. Furthermore, due to the introduction of the image acquisition and sorting systems, the method is costly and complex to operate, making it unsuitable for online analysis and measurement in production. Patent application number 201811098249.5 discloses a "method for rapidly estimating the actual proportion of stems in tobacco shreds in cigarettes." By measuring the potassium and chlorine content in leaf shreds and stem shreds, the potassium and chlorine content in the blended mixture can be calculated. By accurately measuring the potassium and chlorine content in the tobacco shreds of cigarettes, the actual proportion of stem shreds in the tobacco shreds can be calculated. However, due to problems with the testing method, the measurement process suffers from low sample discrimination and poor repeatability, which is insufficient to achieve the purpose of measuring the stem shred content in tobacco shreds.

[0004] In summary, there is currently a lack of accurate and objective methods for determining the content of stems in tobacco. This invention is proposed to address these issues. Summary of the Invention

[0005] The purpose of this invention is to provide a new method for determining the stem content in tobacco shreds, based on the above-mentioned application background and existing compression rheology theory.

[0006] The principle of this invention lies in utilizing the difference in stress relaxation behavior caused by the difference in mechanical properties between leaf filaments and stem filaments. By using a tobacco compression rheology tester to obtain stress relaxation curves of different samples under set conditions, and by analyzing the differences in stress relaxation curves, the content of stem filaments in tobacco filaments can be finally obtained.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A method for determining the stem content in tobacco shreds based on compression rheology is proposed. This method utilizes a tobacco compression rheology analyzer under specific compression conditions to obtain stress relaxation curves for several tobacco shred samples with known stem contents. The obtained data is then processed and fitted using a five-element generalized Maxwell model (five elements refer to two Maxwell elements (each Maxwell element consists of a spring element and a slug element connected in series) and one spring element connected in parallel. The theoretical basis can be found in Yang Mingshao, *Agricultural Material Rheology* [M]. Beijing: China Agriculture Press, 2010). The equilibrium stress values ​​that show significant differences under certain conditions are identified. The data is then further processed and linearly fitted to obtain a standard curve equation for stem content. Finally, experiments are conducted on unknown samples using the tobacco compression rheology analyzer, and the obtained data is substituted into the standard curve equation to determine the stem content in a specific tobacco shred sample. The specific steps of this method include:

[0009] (1) Sample pretreatment. Leaf shreds and planned stem shreds from a specific brand and formula were selected and passed through a 1.25mm sieve to remove broken shreds. They were then placed in a constant temperature and humidity chamber (temperature: 22℃±1℃, relative humidity: 60%±2%) for 48 hours to equilibrate before use. During the experiment, leaf shreds and stem shreds were blended according to the set blending ratio to obtain tobacco blend samples with different stem shred contents. The set stem shred content values ​​were recorded to form standard samples.

[0010] (2) Compression rheological test of standard samples. Compression rheological tests were conducted on the samples using a tobacco compression rheology analyzer. The experimental conditions were: feed rate ≥ 10.0 g, compression head speed ≤ 10 mm / s, maximum compression force ≤ 5 kg, pressure head position remained unchanged after reaching maximum compression force, and pressure holding time was controlled to be above 60 s. Stress and time test data during the compression rheological process were obtained through a data acquisition system, and data from the stress relaxation stage were analyzed. Each sample was tested three times under the same experimental conditions, and the average value was taken as the stress relaxation data for that sample.

[0011] (3) Establishment of the standard curve equation. The stress relaxation curves of the above-mentioned blended samples were compared and analyzed. The standard curve equation was established using the following method: based on the constitutive equation of the five-element generalized Maxwell model.

[0012]

[0013] σ(t): The stress of the system at time t (in kPa);

[0014] t: time s;

[0015] ε e Initial strain of tobacco shreds;

[0016] σ1: The stress of the first Maxwell element at time t;

[0017] σ2: The stress of the second Maxwell element at time t;

[0018] T1 and T2 are the stress relaxation times (kPa / s) of the two Maxwell elements, respectively.

[0019] The equilibrium stress of the corresponding sample was obtained by fitting the stress relaxation data and the value was recorded. Then, the data was linearly fitted with the fibrous content of the blended sample as the ordinate and the equilibrium stress of the sample as the abscissa to obtain the standard curve equation of fibrous content: Y = A + B * X, where Y is the fibrous content; X is the equilibrium stress of the sample under the set experimental conditions; and A and B are the specific fitting parameters.

[0020] (4) Testing of mixed tobacco samples with unknown stem content. Take a certain amount of mixed tobacco sample to be tested, pre-treat it according to the conditions in step (1), determine the stress relaxation curve of the sample by the method in step (2), and calculate the equilibrium stress by the method in step (3); use the stem content standard curve equation obtained in step (3) to calculate the stem content in the mixed tobacco sample.

[0021] This invention provides a feasible method for effectively determining the stem content in tobacco shreds. The use of this method can provide a technical reference for accurately controlling the proportion of stems in blended tobacco shreds, and can also support the stabilization of the physical and sensory quality of cigarette products. Attached Figure Description

[0022] Figure 1 The stress-time curves are shown during the creep / compression and stress relaxation processes of tobacco shreds.

[0023] Figure 2 The stress relaxation curves are for tobacco samples with different stem contents. The curves from bottom to top are: leaf, 10% stem, 20% stem, 30% stem, 40% stem, 50% stem, and pure stem.

[0024] Figure 3 This is a standard curve plot showing the correlation between stem content and equilibrium stress for tobacco samples with different stem contents, i.e., the fitting result of stem content and equilibrium stress.

[0025] Figure 4 This is a schematic diagram of the structure and principle of a tobacco compression rheology tester.

[0026] Figure 4 The components include: 1. Displacement sensor; 2. Indenter; 3. Pressure sensor; 4. Compression sleeve; and 5. Computer, which collects data such as stress, displacement, and time of the sample in real time during the test. Detailed Implementation

[0027] To make the objectives, technical solutions, and beneficial effects of this invention clearer, detailed descriptions will be provided below in conjunction with embodiments to facilitate understanding by those skilled in the art.

[0028] Example 1: Prediction of stem content in tobacco of a certain brand A.

[0029] 1. Sample Pretreatment. Leaf shreds and planned stem shreds from a specific brand and formula were selected and passed through a 1.25mm sieve to remove broken shreds. They were then placed in a constant temperature and humidity chamber (temperature: 22℃±1℃, relative humidity: 60%±2%) for 48 hours to equilibrate before use. During the experiment, leaf shreds and stem shreds were blended according to the set blending ratio to obtain tobacco blend samples with different stem shred contents. The set stem shred content values ​​were recorded to form standard samples. The blending results of the standard samples are as follows:

[0030]

[0031] 2. Compression rheological experiment and solution of equilibrium stress. A tobacco compression rheology tester (see...) was used. Figure 4 The Zhengzhou Tobacco Research Institute of China National Tobacco Corporation conducted compression rheology experiments on the test samples. Each time, 15g of the blended tobacco sample was slowly loaded into the compression sleeve, maintaining its natural stacking state. During compression, the pressure head's downward speed was set to 1mm / s, and the maximum compression force was 3kg. After reaching the maximum compression force, the pressure head position remained unchanged for 200s. Samples numbered 1, 2, 3, 4, 5, 6, and 7 were tested sequentially. The creep / compression and stress relaxation curves of blended sample 1 are shown in the appendix. Figure 1 The stress relaxation curves of samples numbered 1, 2, 3, 4, 5, 6, and 7 above (which can be directly displayed on the instrument) are attached. Figure 2 ; by appendix Figure 2 It can be seen that the stress relaxation curves of the various blended samples differ significantly under the set experimental conditions. By fitting the stress relaxation curves to the constitutive equation of the five-element generalized Maxwell model, the equilibrium stress results of each blended sample under the experimental conditions are as follows:

[0032]

[0033] 3. Establishment of the standard curve. Using the fibrous content of the blended sample as the ordinate and the equilibrium stress of the sample as the abscissa, a linear fit was performed on the obtained data to obtain the standard curve equation for the fibrous content: Y = -442.528 + 118.465*X, with a correlation coefficient R0. 2 =0.9861, see appendix Figure 3 ;

[0034] 4. Prediction of stem content in actual blended tobacco samples. A certain amount of blended tobacco samples to be measured in the actual process were taken and pretreated according to the conditions in step (1). The stress relaxation curve of the sample was measured and the equilibrium stress was calculated using the method in step (2). The stem content standard curve equation obtained in step (3) was used to calculate the stem content in the blended tobacco sample. The sample was measured 10 times, and the relative error of the ten experiments was calculated as follows:

[0035]

[0036]

[0037] The data in the table shows that the relative deviation is within 5.04%, indicating that the prediction results are accurate and reliable.

[0038] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. The present invention is not limited to the above embodiments; the embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A method for determining the stem content in cut tobacco based on compression rheology, characterized in that: The stress relaxation curves of several kinds of cut tobacco samples with known stem content are obtained in the process by selecting compression conditions using a cut tobacco compression rheometer, the obtained data are then processed and fitted using a five-element generalized Maxwell model, the equilibrium stress values of the samples under certain conditions with obvious differences are found out, the obtained data are then processed and linearly fitted to obtain a stem content standard curve equation, then the unknown sample is tested using the cut tobacco compression rheometer, and the obtained data are substituted into the standard curve equation to realize the determination of the stem content in a certain cut tobacco sample; The specific steps include: (1) sample pretreatment: select the leaf tobacco of the brand and formula to be tested and the stem to be mixed, pass through a 1.25 mm sieve to remove the broken tobacco; then place in a constant temperature and humidity chamber for 48 h of equilibrium and reserve; during the experiment, the leaf tobacco and the stem are mixed according to the set mixing ratio to obtain cut tobacco mixed samples with different stem contents, and the set stem content value is recorded to form standard samples; (2) compression rheological test of the standard samples: a cut tobacco compression rheometer is used to perform a compression rheological test on the samples; the experimental conditions are: the feeding amount is ≥10.0 g, the compression head lowering speed during the compression process is ≤10 mm / s, the maximum compression force is set to ≤5 kg, the compression head position is kept unchanged after reaching the maximum compression force, and the pressure maintaining time is controlled to be more than 60 s; the stress and time test data in the compression rheological process are obtained through a data acquisition system, and the stress relaxation stage data are taken for analysis; each sample is tested 3 times under the same test conditions, and the average value is taken as the stress relaxation data of the sample; (3) establishment of the standard curve equation: the stress relaxation curves of the mixed samples are compared and analyzed, and the following method is used to establish the standard curve equation; according to the constitutive equation of the five-element generalized Maxwell model: ， σ(t): the stress of the system at t time Kpa; t: time s; σ e : initial strain of the tobacco shred; σ1: the stress of the first Maxwell element at t time; σ2: the stress of the second Maxwell element at t time; T1, T2: the stress relaxation times of the two Maxwell elements Kpa / s; The equilibrium stress of the corresponding sample is obtained by fitting the stress relaxation data, and the value is recorded, then the stem content of the mixed sample is taken as the ordinate, and the equilibrium stress of the sample is taken as the abscissa, the obtained data are linearly fitted to obtain the standard curve equation of the stem content: Y=A+B*X, wherein Y is the stem content, X is the equilibrium stress of the sample under the set experimental conditions, and A and B are specific fitting parameters; (4) test of the mixed cut tobacco sample with unknown stem content: take the mixed cut tobacco sample to be determined, pretreat according to the conditions in step (1), determine the stress relaxation curve of the sample by the method in step (2), and obtain the equilibrium stress by the method in step (3); the stem content standard curve equation obtained in step (3) is used to calculate the stem content in the mixed cut tobacco sample.

2. A method of determining the stem content of tobacco shreds based on compression rheology according to claim 1, characterized in that: The specific conditions of the constant temperature and humidity in step (1) are: temperature: 22 ℃±1 ℃, relative humidity: 60 %±2 %.

3. A method of determining the stem content of cut tobacco based on compression rheometry as claimed in claim 1, characterized in that: The experimental conditions in step (2) are as follows: the feeding amount is 15 g-30 g, the speed of the pressure head is 1-5 mm / s during compression, the maximum compression force is set to be ≤2-5 kg, the position of the pressure head is kept unchanged after reaching the maximum compression force, and the pressure maintaining time is controlled to be above 100 s-200 s.

4. A method of determining the stem content of cut tobacco based on compression rheometry as claimed in claim 1, characterized in that: The set blending ratios of cuttings in step (1) are 0, 10, 20, 30, 40, 50 and 100, respectively.

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