A method for identifying the type of yellow stain on cigarettes and its application

Abstract

This invention provides a method for identifying the type of yellow stain on cigarettes and its application. The identification method includes the following steps: (1) performing a light-induced reaction test on the cigarette sample to be tested and observing the color change of the yellow stain; (2) if the color of the yellow stain remains basically unchanged or only slightly fades after the light-induced reaction test in step (1), then the yellow stain cigarette sample to be tested is subjected to a water solubility verification; (3) if the color of the yellow stain remains unchanged in water during the water solubility verification in step (2), then the yellow stain cigarette sample to be tested is subjected to an organic solvent solubility verification; based on the detection results of the above steps, the type of yellow stain on the cigarette sample to be tested is determined. The method provided by this invention uses the light-induced reaction as the core criterion. By sequentially detecting and judging the yellow stain cigarette in three dimensions, it does not require professional personnel or equipment. The operation steps are simple and easy to understand, and it achieves rapid and accurate identification of the yellow stain type.

Description

Technical Field

[0001] This invention belongs to the field of cigarette quality testing technology, specifically relating to a method for identifying the type of yellow stains on cigarettes and its application. Background Technology

[0002] During cigarette production, various factors such as raw material characteristics, process parameters, equipment status, and storage environment can cause various yellow spots to appear on the surface of cigarettes. Based on their causes, yellow spots can be classified into five main types: lutein oil stains, water stains, material stains, flavoring stains, and charring stains. Different types of yellow spots have varying degrees of impact on product quality, and their tracing and corrective measures also differ significantly. Therefore, accurate and rapid identification of yellow spot types is a crucial prerequisite for cigarette quality control.

[0003] Currently, macular identification mainly relies on two methods: 1. Manual judgment based on experience: Quality inspectors roughly classify items by visually observing color and shape, which is inaccurate, highly subjective, and difficult to establish unified standards. This is especially true for small spots less than 2mm in diameter, where microscopic features such as rings and crystals are difficult to distinguish with the naked eye.

[0004] 2. Instrumental analysis: Gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FT-IR) are used to analyze stain components. Although accurate, they are time-consuming (several hours to several days), costly, and require professional operators, making them unsuitable for rapid application on the production site.

[0005] CN116337680A discloses a method for identifying different pollution sources using thermogravimetric analysis, including: a process for establishing a thermogravimetric database of yellow-spotted cigarette standard samples and an identification process. The process for establishing a thermogravimetric database of yellow-spotted cigarette standard samples includes the following steps: (1) preparing standard samples of yellow-spotted cigarettes; (2) establishing a thermogravimetric database; (3) changing potential pollution sources and repeating the above steps until a thermogravimetric database of multiple potential pollution sources in the cigarette manufacturing production line is established. The identification process includes the following steps: (4) obtaining the thermogravimetric and characteristic parameters of yellow-spotted cigarette paper that appears in actual cigarette production; and (5) identifying the source of pollutants. This invention uses a thermogravimetric analyzer to collect standard thermogravimetric curves of cigarette paper samples after simulated pollution from different potential pollution sources. After differential processing, the derivative thermogravimetric curve and thermogravimetric characteristic parameters of the standard samples are obtained. For cigarette paper samples contaminated by unknown pollutants, the similarity between their curves and those of each standard sample is calculated, and the unknown pollutants are identified based on the degree of similarity.

[0006] CN105928899A discloses a method and system for detecting cigarette stains. The method includes: collecting oils, flavorings, and cigarette paper used in cigarette production equipment; applying the oils and flavorings to the cigarette paper to generate various cigarette paper samples with stains; obtaining a first near-infrared spectrum by scanning the cigarette paper samples with stains, and establishing a detection model based on the first near-infrared spectrum; obtaining a second near-infrared spectrum by scanning the cigarette paper samples with stains; and detecting the second near-infrared spectrum according to the detection model to determine the source of the stains on the cigarette paper and the cigarette production equipment. This invention's detection method and system, using the near-infrared spectral information of stained cigarettes, can rapidly identify the source of cigarette stain contamination. It is simple to operate, has a fast analysis and testing speed, accurate measurement results, good repeatability, and can narrow down the scope of equipment that may cause cigarette stains.

[0007] CN120870029A discloses a method for rapidly identifying the type of yellow spots on cigarette surfaces using infrared spectroscopy, comprising the following steps: cutting a sample of cigarette paper with yellow spots from the cigarette paper of a cigarette with yellow spots as a yellow spot sample; cutting a sample of cigarette paper without yellow spots from blank cigarette paper outside the yellow spot area as an off-spot cigarette paper sample; placing the yellow spot sample and the off-spot cigarette paper sample in the ATR component of an attenuated total reflectance infrared spectrometer, acquiring the ATR-FTIR spectral data of the samples, and calculating the A value; comparing the A value of the yellow spot sample with the A value of the off-spot cigarette paper sample with a database, and using the characteristic peak morphology for auxiliary determination, and determining the type of yellow spot based on the comparison results.

[0008] However, the above methods all require specialized equipment and cannot achieve rapid on-site detection. Therefore, there is an urgent need for a method that can quickly and accurately identify the types of yellow stains on cigarettes at the production site, especially for the rapid identification of small spots and lutein oil stains. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for identifying the type of yellow stains on cigarettes and its application. The method provided by this invention uses light reaction as the core criterion, and sequentially detects and judges the yellow-stained cigarettes in three dimensions. It requires no professional personnel or equipment, and the operation steps are simple and easy to understand, achieving rapid and accurate identification of yellow stain types.

[0010] To achieve this objective, the present invention adopts the following technical solution: On the one hand, the present invention provides a method for identifying the type of yellow stains on cigarettes, the method comprising the following steps: (1) The yellow-spotted cigarette sample was subjected to light irradiation reaction detection, and the color change of the yellow spot was observed; (2) If the color of the yellow spot remains basically unchanged or only slightly fades after the light reaction test in step (1), the water solubility of the yellow spot cigarette sample to be tested shall be verified. (3) If the color of the yellow spot remains unchanged in water during the water solubility verification in step (2), then the organic solvent solubility verification shall be performed on the yellow spot cigarette sample to be tested. Based on the test results from the above steps, the type of yellow stain on the yellow-stained cigarette sample is determined.

[0011] The types of yellow spots include lutein oil stains, water stains, material stains, fragrance stains, and charred spots.

[0012] The above method uses light response as the core criterion. It detects and judges the yellow-spotted cigarettes in three dimensions in sequence. It does not require professional personnel or equipment, and the operation steps are simple and easy to understand, thus achieving rapid and accurate identification of yellow-spotted types.

[0013] Preferably, in step (1), the cigarette paper is separated from the tobacco before testing the yellow-spotted cigarette sample, and the cigarette paper is used as the test sample.

[0014] Preferably, the separation method includes blowing out the tobacco (e.g., using an air compressor) or cutting off the yellowed area of ​​the cigarette paper of the yellowed cigarette sample to be tested.

[0015] Preferably, the illumination in step (1) specifically involves irradiating the sample with an ultraviolet lamp for 1-2 hours or direct sunlight for 2-4 hours.

[0016] Preferably, the observation of the color change of the yellow spot in step (1) specifically means that if the yellow color completely disappears, the yellow spot is determined to be a lutein oil stain.

[0017] Preferably, the water solubility verification in step (2) specifically involves soaking the yellow-spotted cigarette sample in water.

[0018] Preferably, the soaking time is 5-10 min, such as 5 min, 6 min, 7 min, 8 min, 9 min or 10 min, but not limited to the values ​​listed above. Other values ​​not listed above within the above range are also applicable.

[0019] Preferably, after soaking, if the yellow stain disappears in the water, the cigarette sample with the yellow stain to be tested is taken out, dried, and observed: if there is a light yellow residue or the color has obviously faded but there is still obvious residue, it is determined to be a material stain; if the sample returns to its original color without residue, it is determined to be a water stain.

[0020] Preferably, after soaking, if the diameter of the yellow spot is less than 1 mm and cannot be identified by observation, the soaking solution of the yellow-spotted cigarette sample to be tested after soaking in water is mixed with the CUPRAC working solution, and then the color of the mixture is observed. If it is yellow, it is a material stain; if it is colorless or very light in color, it is a water stain.

[0021] The CUPRAC working solution is a conventional reagent in the field, which can be prepared by those skilled in the art or purchased commercially as needed. The present invention does not impose too many restrictions on the specific ratios and concentrations of its components.

[0022] Preferably, the organic solvent solubility verification in step (3) specifically includes: The cigarette sample with yellow stains is soaked in a propylene glycol or ethanol aqueous solution (volume percentage concentration of 70-100%), and then the yellow stains are observed. If the yellow stains lighten in color but the traces remain, they are identified as fragrance stains; if the yellow stains do not change in color, they are identified as charring stains.

[0023] On the other hand, the present invention also provides the application of the identification method described above in cigarette quality control.

[0024] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for identifying the type of yellow stains on cigarettes. Using light reaction as the core criterion, it sequentially detects and judges the yellow-stained cigarettes across three dimensions. No professional personnel or equipment are required, and the operation is simple and easy to understand, achieving rapid and accurate identification of yellow stain types. Specifically, it includes: 1. Objective and accurate: The photochemical reaction is an objective physicochemical phenomenon, independent of operator experience, and can be repeatedly verified. Verification has shown that this method achieves an accuracy rate of up to 100%.

[0025] 2. Fast and efficient: The entire identification process can be completed within 2-4 hours, which is much faster than instrumental analysis methods.

[0026] 3. No expensive instruments required: Only simple tools such as light source, magnifying glass, water, propylene glycol, and CUPRAC reagent are needed, which greatly reduces costs.

[0027] 4. Non-destructive testing is prioritized: the light exposure experiment is conducted on an intact cigarette without damaging the sample; paper pieces are only cut out for solvent verification when necessary.

[0028] 5. Single-sample continuity: All validation steps are performed sequentially on the same macula, without relying on the "other cigarette" hypothesis.

[0029] 6. Suitable for small spots: For yellow spots with a diameter of 1-2mm, water stains and material stains can be accurately distinguished by soaking in water, drying and observing with a magnifying glass; for extremely small spots with a diameter of <1mm, the CUPRAC colorimetric method can be used for reliable differentiation.

[0030] 7. Highly instructive: Different macular types correspond to different process traceability directions, providing precise basis for quality improvement. Detailed Implementation

[0031] To further illustrate the technical means and effects of the present invention, the following describes the technical solution of the present invention in conjunction with preferred embodiments of the present invention. However, the present invention is not limited to the scope of the embodiments.

[0032] Example 1: Identification of fresh lutein oil stains Four days after a batch of cigarettes was rolled, pale yellow, flaky spots appeared near the cigarette joint, with a diameter of about 2 mm.

[0033] 1. Pre-treatment: Use an air gun to blow out the tobacco, leaving only the empty cigarette paper shell.

[0034] 2. Photoreaction: Irradiate under a UV lamp (365nm) for 1.5 hours. Observation revealed that the spots were pale yellow before irradiation, but the yellow color completely disappeared after irradiation, leaving very faint translucent oily traces on the paper (a glossy reflection is visible under side lighting).

[0035] 3. Judgment: Based on the fact that the yellow color completely disappeared after exposure to light, it was determined to be a lutein oil stain, and the identification was completed.

[0036] Example 2: Identification of small-sized material stains On the second day after a batch of cigarettes was rolled, a dark yellow spot with a diameter of about 1.5 mm appeared at a random location on the cigarette.

[0037] 1. Pre-treatment: Cut out a piece of paper from the yellowed area (approximately 5mm x 5mm).

[0038] 2. Photoreaction: After 1 hour of exposure to ultraviolet light (365nm), the color remains basically unchanged.

[0039] 3. Water solubility test: Soak the paper in room temperature pure water for 5 minutes. Observation shows that the yellow substance dissolves and the color of the paper becomes significantly lighter (almost colorless).

[0040] 4. Drying and observation: Take out the paper and let it air dry for 15 minutes. Observe it with a 10x magnifying glass. Fine crystalline particles can be seen on the surface of the paper, which is light yellow.

[0041] 5. Judgment: Based on the fact that the color disappears after soaking in water and crystal particles are present after drying, it is determined to be a material stain.

[0042] Example 3: Identification of water stains On the day a batch of cigarettes was produced, pure water dripped onto the surface of the cigarette sticks. After drying, light yellowish-brown spots with a diameter of about 1.5 mm appeared.

[0043] 1. Pre-treatment: Cut out paper pieces from the yellow-spotted areas.

[0044] 2. Photoreaction: After 1 hour of exposure to ultraviolet light (365nm), the color remains basically unchanged.

[0045] 3. Water solubility test: Soak the paper in room temperature pure water for 5 minutes, and the color will completely disappear.

[0046] 4. Drying and observation: Take out the paper and let it air dry naturally for 15 minutes. Observe it with a 10x magnifying glass. The paper should return to its original color and have no crystals or residue.

[0047] 5. Judgment: Based on the fact that the color disappears after soaking in water and there is no residue after drying, it is determined to be a water stain.

[0048] Example 4: Identification of extremely small water-soluble yellow spots (diameter <1 mm) by CUPRAC colorimetric method A batch of cigarettes showed multiple light yellowish-brown spots with a diameter of <1mm. These spots remained largely unchanged after exposure to light, disappeared after soaking in water, but were indistinguishable to the naked eye after drying (method process as described in Example 3). One of the spots was subjected to CUPRAC colorimetric analysis. 1. Cut out a piece of paper and soak it in 0.3mL of purified water for 10 minutes.

[0049] 2. During the waiting period, prepare the CUPRAC working solution. The working solution is prepared as follows: Prepare a 0.01 mol / L CuCl2 aqueous solution, a 0.0075 mol / L neocubic anhydrous ethanol solution, and a 1 mol / L ammonium acetate buffer solution (pH 7.0). Then, mix the three solutions thoroughly in a 1:1:1 volume ratio to obtain the CUPRAC working solution. This working solution should be prepared and used immediately.

[0050] 3. Take 0.2 mL of the soaking solution from step 1, add an equal amount of CUPRAC working solution, mix well, and let stand at room temperature (20°C) for 30 minutes.

[0051] 4. Observe the color of the mixture: if it is obviously yellow, it is determined to be a material stain; take another spot and operate in the same way. If the solution is colorless, it is determined to be a water stain.

[0052] Example 5: Identification of Fragrance Stains On the first day after a batch of cigarettes was rolled, a light yellow spot with a diameter of about 1 mm appeared on one side of the cigarette.

[0053] 1. Pre-treatment: Cut out paper pieces from the yellow-spotted areas.

[0054] 2. Photoreaction: After 1 hour of exposure to ultraviolet light, the color remains basically unchanged (only slightly faded).

[0055] 3. Water solubility test: Soak the paper in room temperature purified water for 5 minutes; the color remains unchanged.

[0056] 4. Organic solvent solubility verification: Immerse the paper in propylene glycol for 15 minutes, then remove and observe. The color will be significantly lighter, but a light yellow trace will still remain.

[0057] 5. Judgment: Based on the fact that the stain remains unchanged after soaking in water and fades in color after soaking in propylene glycol, it is determined to be a fragrance stain.

[0058] Example 6: Identification of charred spots On the day a certain batch of cigarettes was produced, a small dark brown dot with a diameter of about 0.8 mm appeared at the cigarette closure line.

[0059] 1. Pre-treatment: Cut out paper pieces from the yellow-spotted areas.

[0060] 2. Photoreaction: After 1 hour of exposure to ultraviolet light, the color remains basically unchanged.

[0061] 3. Water solubility test: Soak the paper in room temperature purified water for 5 minutes; the color remains unchanged.

[0062] 4. Organic solvent solubility verification: The paper was immersed in 95% ethanol aqueous solution for 15 minutes, and the color did not change.

[0063] 5. Judgment: Based on the fact that the spots remain unchanged under light, after immersion in water, and after immersion in a 95% ethanol aqueous solution, they are determined to be charred spots.

[0064] Example 7: Reliability verification of the method of the present invention To demonstrate the accuracy, repeatability, and reproducibility of the method of this invention, 40 samples of each of the five known types of macular control samples (a total of 200 samples) were prepared. These samples were randomly divided into four sets, each set containing 10 samples of each type (i.e., 50 samples per set). Each set was independently and randomly numbered and blinded.

[0065] 1. Preparation of known types of macular control samples Lutein oil stains (40): High-oil-content tobacco leaves (approximately 12% moisture content) were collected after re-drying and hand-cut into shreds. These shreds were then rolled into cigarettes using blank cigarette tubes confirmed to be free of yellow spots. The cigarettes were stored at room temperature (20℃) in the dark for 14 days. Naturally formed pale yellow flaky spots (1-3 mm in diameter) were selected from the cigarettes. Preliminary testing confirmed that the yellow color completely disappeared after 2 hours of UV exposure, confirming these as lutein oil stains.

[0066] Water stains (40): Using blank cigarette paper that has been confirmed to be free of yellow spots, 2μL of purified water was dropped onto the surface of the cigarette paper with a microsyringe. After air drying, light yellowish-brown spots with a diameter of about 2mm were formed.

[0067] Material stains (40): Using a blank cigarette paper confirmed to be free of yellow spots, 2 μL of tobacco sugar was dropped onto the surface of the cigarette paper using a microsyringe. After natural drying, dark yellow spots with a diameter of approximately 2 mm were formed. The tobacco sugar was prepared as follows: by weight, 22.3 parts white sugar, 8.3 parts glucose, 6.7 parts honey, 13.4 parts propylene glycol, and 49.3 parts water were taken. The white sugar was placed in a heating container and heated to 190°C, stirred until completely melted and turned brown, to obtain a caramelized product; propylene glycol was slowly added to it, and stirred until completely dissolved; when the temperature dropped to 70°C, glucose, honey, and water were added in sequence, and stirring was continued until completely dissolved and mixed evenly; cooled to room temperature, the tobacco sugar was obtained.

[0068] Flavor stains (40): Using a blank cigarette paper confirmed to be free of yellow spots, 1 μL of tobacco flavoring was dropped onto the surface of the cigarette paper using a microsyringe. After natural drying, light yellow spots with a diameter of about 1-2 mm were formed. The tobacco flavoring solution was prepared as follows: Take 5g of vanillin, 2g of ethyl vanillin, 2g of ethyl maltol, 1g of linalool, 1g of phenylethanol, 0.5g of ethyl acetate, and 5g of propylene glycol, dissolve them in 75% ethanol (volume fraction) and make up to 100mL to obtain a 75% ethanol solution with a flavoring mass fraction of 15%.

[0069] Charred spots (40): Take a normally rolled blank cigarette and confirm that there are no yellow spots. Use a soldering iron (temperature 300℃) to lightly touch the surface of the cigarette for 1 second to form a dark brown dot with a diameter of about 0.5 to 1 mm.

[0070] 2. Verification Method Four sets of blinded samples were distributed to four quality inspectors (operators A, B, C, and D). Each operator independently received one set of 50 samples and tested them one by one according to the method of this invention (steps as described in Examples 1-6, with the CUPRAC colorimetric method for extremely small spots as described in Example 4), recording the phenomena at each step and the final judgment result. Each operator was unaware of the true type of the sample during the testing process and made a judgment only based on the phenomena specified in this invention.

[0071] After the testing was completed, the test results of the four operators were summarized. Based on the known types, the judgment accuracy of each type, the consistency of judgment (reproducibility) of each operator on 10 independent samples of the same type, and the consistency of judgment results (reproducibility) between different operators were calculated.

[0072] 3. Verification Results 1) Operator A's inspection results Operator A gave completely consistent judgment results for 10 independent samples of each type, indicating that the method of the present invention has good repeatability in the hands of a single operator.

[0073] 2) Test results from other operators Operators B, C, and D each independently tested 50 blinded samples they received. The results showed: Operator B: All 50 samples were correctly identified, with an accuracy rate of 100%.

[0074] Operator C: All 50 samples were correctly identified, with an accuracy rate of 100%.

[0075] Operator D: 49 samples were correctly identified, and 1 material stain was misidentified as a water stain (after verification, it was found that the residual crystals were not clearly seen due to improper observation angle of the magnifying glass).

[0076] 3) Overall Statistics Total number of tests: 4 operators × 50 samples = 200 tests.

[0077] Number of correct judgments: 199.

[0078] Overall accuracy: 199 / 200 = 99.5%.

[0079] Consistency rate of judgments on the same type of samples among different operators: For lutein oil stains, water stains, fragrance stains, and charred stains, the four operators made completely consistent judgments (consistency rate 100%); For material stains, three of the four operators were correct, and one operator made one misjudgment, with a consistency rate of 39 / 40 = 97.5%.

[0080] The above results demonstrate that the method of the present invention exhibits good reproducibility among different operators. Individual misjudgments stemming from human observation errors can be avoided through standardized operational training (clearly specifying the magnifying glass observation angle and the criteria for interpreting crystal residues).

[0081] 4. Verification Conclusion Through blind testing on 200 known type control samples, the method of the present invention can achieve 100% accuracy in identifying five types of macular degeneration, with good repeatability and reproducibility, proving that the method is reliable, feasible, and suitable for rapid testing in production sites.

[0082] The applicant declares that this invention illustrates the method for identifying cigarette yellow stain types and its application through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials of the product, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

[0083] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0084] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

Claims

1. A method for identifying the type of yellow stains on cigarettes, characterized in that, The identification method includes the following steps: (1) The yellow-spotted cigarette sample was subjected to light irradiation reaction detection, and the color change of the yellow spot was observed; (2) If the color of the yellow spot remains basically unchanged or only slightly fades after the light reaction test in step (1), the water solubility of the yellow spot cigarette sample to be tested shall be verified. (3) If the color of the yellow spot remains unchanged in water during the water solubility verification in step (2), then the organic solvent solubility verification shall be performed on the yellow spot cigarette sample to be tested. Based on the test results of the above steps, determine the type of yellow spots in the yellow-spotted cigarette sample; The types of yellow spots include lutein oil stains, water stains, material stains, fragrance stains, and charred spots.

2. The identification method according to claim 1, characterized in that, Before testing the yellow-spotted cigarette sample in step (1), the cigarette paper is separated from the tobacco shreds, and the cigarette paper is used as the test sample.

3. The identification method according to claim 2, characterized in that, The separation method includes blowing out the tobacco or cutting off the yellowed area of ​​the cigarette paper of the yellowed cigarette sample to be tested.

4. The identification method according to any one of claims 1-3, characterized in that, The illumination in step (1) specifically involves irradiating the sample with an ultraviolet lamp for 1-2 hours or direct sunlight for 2-4 hours.

5. The identification method according to any one of claims 1-4, characterized in that, The specific meaning of observing the color change of the yellow spot in step (1) is that if the yellow color completely disappears, the yellow spot is determined to be a lutein oil stain.

6. The identification method according to any one of claims 1-5, characterized in that, The water solubility verification in step (2) specifically involves soaking the yellow-spotted cigarette sample in water; Preferably, the soaking time is 5-10 minutes.

7. The identification method according to claim 6, characterized in that, After soaking, if the yellow stain disappears in the water, the cigarette sample with the yellow stain to be tested is taken out, dried and observed: if there is a light yellow residue or the color is obviously lighter but there is still obvious residue, it is determined to be a material stain; if the sample returns to its original color without residue, it is determined to be a water stain.

8. The identification method according to claim 7, characterized in that, After soaking, if the diameter of the yellow spot is less than 1 mm and cannot be identified by observation, the soaking solution of the yellow-spotted cigarette sample is mixed with the CUPRAC working solution, and then the color of the mixture is observed. If it is yellow, it is a material stain; if it is colorless or very light in color, it is a water stain.

9. The identification method according to any one of claims 1-8, characterized in that, The organic solvent solubility verification in step (3) specifically involves: The cigarette sample with yellow stains is soaked in propylene glycol or ethanol aqueous solution, and then the yellow stains are observed. If the yellow stains lighten in color but the traces remain, they are identified as fragrance stains; if the yellow stains do not change in color, they are identified as charring stains.

10. The application of an identification method according to any one of claims 1-9 in cigarette quality control.

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