Method for judging significant change of chemical components of fresh tobacco leaves based on CIE-Lab color space value

Abstract

The invention provides a CIE-Lab color space value-based method for judging significant change of chemical components in fresh tobacco leaves, which adopts a paired sample T test method to judge the significant change time of the chemical components in the fresh tobacco leaves based on the CIE-Lab color space value. According to the method, the process of the near infrared spectrum collection test of the fresh tobacco leaves is optimized, the accuracy of the prediction model is improved, and a new thought and method can be provided for chemical component monitoring and quality control of the fresh tobacco leaves.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical component detection, and in particular relates to a method for determining significant changes in the chemical components of fresh tobacco leaves based on CIE-Lab color space values. Background Art

[0002] The chemical content of fresh tobacco leaves is one of the key factors in evaluating the quality of tobacco leaves. By monitoring the dynamic changes of key chemical components of tobacco at different growth stages, targeted agronomic adjustment measures can be provided to tobacco farmers, thereby improving the overall quality of tobacco leaves. However, traditional methods for detecting chemical components of fresh tobacco leaves are not only cumbersome, time-consuming, and costly, but also destructive to samples, resulting in poor timeliness in regulating agronomic measures. In view of these limitations, using near-infrared spectroscopy rapid detection technology to construct a predictive model for the content of key chemical components in fresh tobacco leaves has become a feasible solution. This technology can realize real-time, rapid, and non-destructive monitoring of the chemical composition of fresh tobacco leaves, provide a decision-making basis for the precise regulation of agronomic measures, and promote the refined management of tobacco planting.

[0003] In the process of building a prediction model based on near-infrared spectroscopy technology, obtaining accurate, reliable and stable spectral information of fresh tobacco leaves is a crucial step. However, collecting near-infrared spectral data of fresh tobacco leaves in the field faces multiple challenges. For example, fluctuations in weather factors such as temperature, humidity, and light intensity may have an adverse effect on the stability and reliability of spectral collection information. In order to ensure that the collected near-infrared spectral data is accurate, fresh tobacco leaves are usually picked from the tobacco plants, and appropriate preservation measures are taken, and then they are transported to a laboratory with stable environmental conditions for spectral collection experiments. Therefore, exploring how long the intrinsic chemical quality of fresh tobacco leaves remains stable after picking is the basis for conducting laboratory spectral collection work. However, there is currently a gap in research in this area. Summary of the invention

[0004] The present invention aims to provide a method for judging significant changes in the chemical composition of fresh tobacco leaves based on CIE-Lab color space values, so as to solve the problem that the existing methods for judging the time of significant changes in the chemical quality of fresh tobacco leaves are not accurate and reliable.

[0005] The objective of the present invention is achieved through the following technical solutions:

[0006] A method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values, comprising step S1, wherein S1 is specifically:

[0007] S101, picking fresh tobacco leaf samples in a tobacco field, selecting measurement sites on the surface of the tobacco leaves on site, and measuring the CIE-Lab color space value of each measurement site at an initial time t0;

[0008] S102, the fresh tobacco leaves are sealed and stored away from light, and then the samples are tracked and measured at different measurement time points t at the same interval of time △t according to the same measurement method. i CIE-Lab color space value, where t i It is equal to t0 plus i×△t;

[0009] S103, for different measurement time points t i The CIE-Lab color space value of the sample and the CIE-Lab color space value at the initial time t0 were subjected to paired sample T test, and the time when the T test showed significant difference was determined as the time t when the internal chemical quality of fresh tobacco leaves changed significantly. c .

[0010] In the present invention, the color of tobacco leaves is an important indicator of their intrinsic quality. With the development of colorimetry theory and practice, the color of tobacco leaves can be quantitatively characterized by a spectrophotometer or a colorimeter, and has been widely used in the harvesting, baking and grading of flue-cured tobacco. Studies have shown that the colorimetric parameter L * (from black to white, indicating lightness value), a * (from green to red, indicating the redness value), b * (from blue to yellow, indicating yellowness value) has a significant or extremely significant correlation with chemical indicators such as water-soluble sugar, nicotine, total nitrogen, sugar-alkali ratio, sugar-nitrogen ratio, nitrogen-alkali ratio, potassium-chlorine ratio, volatile alkali, plastid pigment, polyphenols, etc. These research results provide a solid theoretical basis for inferring the change of the overall chemical quality of fresh tobacco leaves by monitoring the change of CIE-Lab color space value. The method of the present invention tracks and measures the CIE-Lab color space value of a fixed point on the fresh tobacco leaves, indirectly reflects the change of the internal chemical composition of the fresh tobacco leaves according to the change of the CIE-Lab color space value, and finally determines the time when the internal chemical quality of the fresh tobacco leaves has changed significantly.

[0011] In the present invention, the fresh tobacco leaf samples in S101 are selected from the fresh tobacco leaves in the middle of the flue-cured tobacco plants in the tobacco field, and the leaves of the fresh tobacco leaves are intact and have a smooth and clean surface. The accuracy of the measurement can be ensured by such a setting.

[0012] In some embodiments of the present invention, the measurement sites in S101 are the upper surface of each tobacco leaf, from the leaf base to the leaf tip, about 1 cm inside the leaf edge, and 10 circles with a diameter of 1.5 cm are marked as fixed measurement sites. The measurement sites selected in this way are representative and have higher measurement accuracy.

[0013] Furthermore, the measurement site needs to ensure that there is no damage, discoloration, spots or contaminants inside each circle.

[0014] In the present invention, the temperature at which the fresh tobacco leaves are sealed and stored away from light in S102 is (20-25)°C.

[0015] The present invention further includes step S2, which verifies the significant changes in the chemical components of the fresh tobacco leaves.

[0016] Furthermore, the S2 specifically includes:

[0017] S201, selecting flue-cured tobacco plants, selecting fresh tobacco leaf samples from the middle of the flue-cured tobacco plants, and dividing them into two groups for storage, with the time being recorded as the initial time T0, wherein the fresh tobacco leaves of the first group are sealed and stored in dry ice, and the fresh tobacco leaves of the second group are sealed and stored away from light;

[0018] S202, pre-treating the two groups of fresh tobacco leaf samples, and then determining the chemical component content, wherein the second group of samples are tracked and determined at different storage time points T at the same interval of time △T. i The chemical composition content of i It is equal to T0 plus i×△T;

[0019] S203, for the second group of different storage time points T i The chemical composition data measured at the first time T0 were analyzed by one-way ANOVA to determine the time point T at which the chemical composition content of fresh tobacco leaves changed significantly. c .

[0020] In the present invention, the temperature at which the fresh tobacco leaves in S202 are sealed and stored away from light is (20-25)°C.

[0021] In the present invention, the chemical components of the fresh tobacco leaves are total sugar, reducing sugar, total nitrogen and total alkaloids.

[0022] The present invention further includes: S204, comparing Tc with tc to confirm the accuracy of the time when the chemical composition of the fresh tobacco leaves undergoes a significant change.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The method for determining significant changes in the chemical composition of fresh tobacco leaves based on CIE-Lab color space values ​​adopts a paired sample T test method to infer changes in the overall chemical quality of fresh tobacco leaves by monitoring changes in CIE-Lab color space values, and ultimately determines the time when significant changes occur in the intrinsic chemical quality of fresh tobacco leaves. The method has high accuracy and stability.

[0025] (2) The method of the present invention optimizes the location, time, measurement site and storage method of tobacco leaf picking and sampling during the fresh tobacco leaf measurement process, further improving the accuracy and stability of the method.

[0026] (3) The method of the present invention adopts a dual determination method combining CIE-Lab color space value judgment and fresh tobacco chemical composition determination to determine the time node when the chemical quality of fresh tobacco leaves changes significantly, indicating the feasibility of tracking the changes in the internal chemical composition of fresh tobacco leaves by monitoring the CIE-Lab color space value, and further improving the accuracy of the determination. At the same time, the chemical composition index of chemical composition detection is optimized, and the time when the chemical composition changes significantly can be accurately determined by detecting total sugar, reducing sugar, total nitrogen and total alkaloids, which greatly saves time, is highly efficient, and has promotion value. DETAILED DESCRIPTION

[0027] The present invention is further described below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solutions of the present invention.

[0028] Example

[0029] A method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values, comprising step S1,

[0030] S1 specifically includes the following steps:

[0031] S101, picking fresh tobacco leaf samples in a tobacco field, selecting measurement sites on the surface of the tobacco leaves on site, and measuring the CIE-Lab color space value of each measurement site at an initial time t0;

[0032] The specific process is as follows:

[0033] Selection and preparation of experimental materials: The middle fresh tobacco leaves of Yunyan 87 variety in Xundian area of ​​Kunming at maturity (one week after topping) were selected as experimental materials. To ensure the accuracy of the test, two middle fresh tobacco leaves were carefully selected in the field, requiring the leaves to be intact, the surface to be flat and clean, and the color to be as uniform as possible. Subsequently, on the upper surface of each tobacco leaf, from the base to the tip of the leaf, about 1 cm inside the leaf edge, 10 circles with a diameter of about 1.5 cm were marked with a marker as fixed measurement sites. It is necessary to ensure that there is no damage, variegated color, spots or contaminants inside each circle to avoid interference with the subsequent CIE-Lab color space value determination. At the same time, the numbers are clearly marked next to each circle for subsequent identification and recording, and the numbers are 1-1 to 1-10 (the first tobacco leaf) and 2-1 to 2-10 (the second tobacco leaf).

[0034] CIE-Lab color space value determination: The first fresh tobacco leaf sample was carefully picked from the tobacco plant, and then the CIE-Lab color space value (L * 、a * 、b *). After three consecutive measurements, the spectrophotometer automatically calculated the average value to ensure the stability of the data. Each site recorded 5 groups of L * 、a * 、b * Chromaticity parameter values ​​are recorded for subsequent analysis. After the first fresh tobacco leaf is measured, the second fresh tobacco leaf is picked from the tobacco plant and the CIE-Lab color space values ​​of its 10 sites are immediately measured using the same method. The time of the first CIE-Lab color space value measurement of each tobacco leaf is recorded, and the time of the first measurement of each fresh tobacco leaf sample is marked as 0h.

[0035] S102, the fresh tobacco leaves are sealed and stored away from light, and then the samples are tracked and measured at different measurement time points t at the same interval of time △t according to the same measurement method. i CIE-Lab color space value, where t i It is equal to t0 plus i×△t;

[0036] The specific process is as follows:

[0037] Sample preservation and follow-up measurement: After each fresh tobacco leaf is tested on site, it is immediately sealed in a ziplock bag and stored in a dark and room temperature environment to minimize moisture loss and light effects. The sample is then brought back to the laboratory for follow-up measurement. During the test, the fresh tobacco leaf samples are repeatedly measured every 2 hours according to the above CIE-Lab color space value determination method. During the entire test, the ambient temperature is (20-25)°C.

[0038] S103, for different measurement time points t i The CIE-Lab color space value of the sample and the CIE-Lab color space value at the initial time t0 were subjected to paired sample T test, and the time when the T test showed significant difference was determined as the time t when the internal chemical quality of fresh tobacco leaves changed significantly. c .

[0039] The specific process is as follows:

[0040] Data processing and result determination: After each determination is completed, the L of each marker site of two fresh tobacco leaves is calculated. * 、a * 、b * IBM SPSS Statistics 19 statistical analysis software was used to analyze the L values ​​of 10 corresponding sites at different measurement time points (starting from 2h) and the initial time (0h). * 、a * 、b *The average values ​​were subjected to paired sample T test. If a paired T test of a colorimetric parameter showed a significant difference (P<0.05), it was determined that the intrinsic chemical quality of the fresh tobacco leaves had changed significantly at this time. In order to confirm the accuracy of the time point of significant change, the test was repeated 2 hours after the first significant difference appeared. If there was still a significant difference, it could be confirmed that the CIE-Lab color space value of the fresh tobacco leaves had changed significantly and the intrinsic chemical quality had changed significantly.

[0041] S2. Verify the significant changes in the chemical composition of fresh tobacco leaves

[0042] The specific steps include:

[0043] S201, selecting flue-cured tobacco plants, selecting fresh tobacco leaf samples from the middle of the flue-cured tobacco plants, and dividing them into two groups for storage, with the time being recorded as the initial time T0, wherein the fresh tobacco leaves of the first group are sealed and stored in dry ice, and the fresh tobacco leaves of the second group are sealed and stored away from light;

[0044] The specific process is as follows:

[0045] Experimental design and sample selection: After completing the monitoring test of the CIE-Lab color space value of fresh tobacco leaves, in order to further verify the changes in the internal chemical composition of fresh tobacco leaves, 60 flue-cured tobacco plants with the same or similar growth status were carefully selected in the same area of ​​the same tobacco field. The tobacco leaves in the same part of the middle of these plants were marked one by one, and one leaf was selected from each plant, totaling 60 fresh tobacco leaves as test samples. After all the marking work was completed, personnel were quickly organized to pick all 60 fresh tobacco leaves in the shortest possible time.

[0046] Sample storage and grouping: Fresh tobacco leaves are grouped immediately after picking. First, 10 leaves are randomly selected and placed in a ziplock bag and sealed, and then immediately placed in dry ice for storage as the first test sample (recorded as 0h storage time). The remaining 50 leaves are stored at room temperature, away from light, and sealed, and are transported to the testing company for subsequent processing within 1 hour.

[0047] S202, pre-treating the two groups of fresh tobacco leaf samples, and then determining the chemical component content, wherein the second group of samples are tracked and determined at different storage time points T at the same interval of time △T. i The chemical composition content of i It is equal to T0 plus i×△T;

[0048] The specific process is as follows:

[0049] Chemical composition determination process: The testing company prepares relevant instruments, equipment and chemical reagents in advance to ensure that fresh tobacco leaf samples can be pre-treated and chemically determined at any time according to standard methods. When 60 fresh tobacco leaves are delivered to the testing company, the chemical composition of 10 fresh tobacco leaves stored in dry ice is first determined. Subsequently, 10 leaves are randomly selected for determination at pre-set time intervals (once every 2 hours) until all leaves have been determined (a total of 6 determinations, 10 leaves each time). Samples at each storage time point must be measured 5 times in parallel to improve the reliability of the data.

[0050] Experimental conditions and determination methods: During the period of light-proof and sealed storage in the laboratory, the indoor temperature of fresh tobacco leaves was (20-25)°C. For each fresh tobacco leaf sample, the chemical composition was determined using an AA3 continuous flow analyzer. The specific determination method refers to industry standards: the mass fraction of total sugar and reducing sugar is determined in accordance with YC / T 159-2019; the mass fraction of total nitrogen is determined in accordance with YC / T 161-2002; the mass fraction of total alkaloids is determined in accordance with YC / T 468-2021.

[0051] S203, for the second group of different storage time points T i The chemical composition data measured at the first time T0 were analyzed by one-way ANOVA to determine the time point T at which the chemical composition content of fresh tobacco leaves changed significantly. c ;

[0052] The specific process is as follows:

[0053] Data analysis and result determination: The above method was used to obtain the chemical composition determination data of fresh tobacco leaves after 0, 2, 4, 6, 8, and 10 hours of storage at room temperature, away from light, and sealed. IBM SPSS Statistics 19 statistical analysis software was used to perform one-way analysis of variance on the total sugar, reducing sugar, total nitrogen, and total alkaloid determination data at different storage time points (starting from 2 hours) and the initial time (0 hours).

[0054] S204. Compare Tc with tc to confirm the accuracy of the time when the chemical composition of the fresh tobacco leaves undergoes significant changes.

[0055] Through this analysis process, the time point when the chemical composition content of fresh tobacco leaves changes significantly can be accurately determined, which is used to verify the accuracy of determining the time when the chemical composition of fresh tobacco leaves changes significantly based on the CIE-Lab color space value.

[0056] Results and Analysis

[0057] 1. Determination of the time when the CIE-Lab color space value of fresh tobacco leaves changes significantly

[0058] After two fresh tobacco leaves were picked, they were stored at room temperature (20-25)℃, away from light, and sealed. * 、a * 、b * The average statistical results and paired T test are shown in Table 1 and Table 2. It can be seen that for L * 、a * 、b * The paired T test of the three chromaticity parameters from 2h to 6h and 0h did not reach a significant level (P>0.05), indicating that the color space value of the fresh tobacco leaves did not change significantly within 6h of storage at room temperature, away from light and sealed after picking; the paired T test of the three chromaticity parameters at 8h, 10h and 0h all reached an extremely significant level (P<0.01), indicating that after the storage time reached 8h, the color space value of the tobacco leaves had undergone extremely significant changes. According to relevant research reports, there is a significant correlation between the color space value of tobacco leaves and their various chemical components. It can be inferred that the overall internal chemical quality of fresh tobacco leaves remains stable and does not change significantly within 6h of storage at room temperature, away from light and sealed, but after the storage time reaches 8h, the content of some of its chemical components begins to change significantly.

[0059] Table 1 Statistical results and paired T test of color space values ​​at different time points at 10 sites on the first fresh tobacco leaf

[0060]

[0061]

[0062] Table 2 Statistical results and paired T test of color space values ​​at different time points at 10 sites on the second fresh tobacco leaf

[0063]

[0064] 2. Determination of the time when the chemical composition content of fresh tobacco leaves undergoes significant changes

[0065] After the fresh tobacco leaves were picked, the mass fractions of total sugar, reducing sugar, total nitrogen and total alkaloids were measured at room temperature (20-25)℃, protected from light and sealed for 0-10h. The results of multiple comparisons of chemical components at different storage time points are shown in Table 4. As can be seen from Table 4, within 0-6h after the fresh tobacco leaves were picked, there was no significant difference in the mass fractions of the four chemical components (P>0.05); the differences in the four chemical components at 8h, 10h and 0h all reached a significant level (P<0.05), indicating that after the storage time reached 8h, the content of some chemical components of the tobacco leaves had changed significantly.

[0066] It can be seen that under the same storage conditions, the time when the chemical composition content of fresh tobacco leaves changes significantly is consistent with the time when the CIE-Lab color space value changes significantly, indicating that it is feasible to monitor the changes in the internal chemical composition of fresh tobacco leaves by using CIE-Lab color space values.

[0067] Table 3 Determination results of total sugar, reducing sugar, total nitrogen and total alkaloid mass fractions of fresh tobacco leaves at different storage times

[0068]

[0069]

[0070] Table 4 Multiple comparisons of total sugar, reducing sugar, total nitrogen and total alkaloids in fresh tobacco leaves at different storage times

[0071]

[0072] Note: Different lowercase letters after the data in the same column indicate significant differences (P<0.05).

[0073] The present invention adopts the paired sample T test method to deeply explore the specific time point when the CIE-Lab color space value of fresh tobacco leaves changes significantly under normal temperature (20-25)°C, light-proof and sealed storage conditions. Furthermore, through multiple comparative analysis, the differences in the content of several key chemical components (including the mass fraction of total sugar, reducing sugar, total nitrogen and total alkaloids) in fresh tobacco leaves at different time points under the same storage environment were evaluated, aiming to verify the accuracy of judging the time of significant changes in the internal chemical components of fresh tobacco leaves based on the CIE-Lab color space value.

[0074] The results showed that after picking fresh tobacco leaves, under the conditions of room temperature (20-25)℃, light-proof and sealed storage, within the first 6 hours, its L * 、a * 、b * None of the three chromaticity parameters changed significantly. However, when the storage time was extended to 8h, the three chromaticity parameters changed significantly compared with 0h. In addition, by measuring the mass fractions of total sugar, reducing sugar, total nitrogen, and total alkaloids of fresh tobacco leaves at different time points under the same storage conditions and performing multiple comparative analysis, it was found that the time point when the chemical component content changed significantly coincided with the time when the CIE-Lab color space value changed significantly. This finding not only confirms that the use of CIE-Lab color space values ​​can effectively determine the time point when the intrinsic chemical quality of fresh tobacco leaves changes significantly, but also shows the feasibility of tracking the changes in the intrinsic chemical composition of fresh tobacco leaves by monitoring the CIE-Lab color space values, thereby providing a new perspective and methodological support for the chemical composition monitoring and quality control of fresh tobacco leaves.

[0075] The above implementation examples have been described in detail the different implementation processes of the present invention, but the implementation methods of the present invention are not limited thereto. Ordinary technicians in the relevant technical field can achieve the purpose of the present invention based on the contents disclosed in the present invention. Any improvements and modifications based on the concept of the present invention fall within the protection scope of the present invention, and the specific protection scope shall be subject to the claims.

Claims

1. A method for determining significant changes in the chemical composition of fresh tobacco leaves based on CIE-Lab color space values, characterized in that: The method comprises step S1, wherein S1 specifically comprises: S101, picking fresh tobacco leaf samples in a tobacco field, selecting measurement sites on the surface of the tobacco leaves on site, and measuring the CIE-Lab color space value of each measurement site at an initial time t0; S102, the fresh tobacco leaves are sealed and stored away from light, and then the samples are tracked and measured at different measurement time points t at the same interval of time △t according to the same measurement method. i CIE-Lab color space value, where t i It is equal to t0 plus i×△t; S103, for different measurement time points t i The CIE-Lab color space value of the sample and the CIE-Lab color space value at the initial time t0 were subjected to paired sample T test, and the time when the T test showed significant difference was determined as the time t when the internal chemical quality of fresh tobacco leaves changed significantly. c .

2. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 1, characterized in that: The S101 medium-fresh tobacco leaf samples are selected from the fresh tobacco leaves in the middle of the flue-cured tobacco plants in the tobacco field. The leaves of the fresh tobacco leaves are intact and the surface is smooth and clean.

3. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 1, characterized in that: The measurement sites in S101 are the upper surface of each tobacco leaf, from the leaf base to the leaf tip, about 1 cm inside the leaf edge, and 10 circles with a diameter of 1.5 cm are marked as fixed measurement sites.

4. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 3, characterized in that: The assay site needs to ensure that there is no damage, discoloration, spots or contaminants inside each circle.

5. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 1, characterized in that: The temperature at which fresh tobacco leaves are sealed and stored away from light in S102 is (20-25)°C.

6. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to any one of claims 1 to 5, characterized in that: The method further includes step S2 of verifying significant changes in the chemical composition of fresh tobacco leaves.

7. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 6, characterized in that: The S2 specifically includes: S201, selecting flue-cured tobacco plants, selecting fresh tobacco leaf samples from the middle of the flue-cured tobacco plants, and dividing them into two groups for storage, with the time being recorded as the initial time T0, wherein the fresh tobacco leaves of the first group are sealed and stored in dry ice, and the fresh tobacco leaves of the second group are sealed and stored away from light; S202, pre-treating the two groups of fresh tobacco leaf samples, and then determining the chemical component content, wherein the second group of samples are tracked and determined at different storage time points T at the same interval of time △T. i The chemical composition content of i It is equal to T0 plus i×△T; S203, for the second group of different storage time points T i The chemical composition data measured at the first time T0 were analyzed by one-way ANOVA to determine the time point T at which the chemical composition content of fresh tobacco leaves changed significantly. c .

8. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 7, characterized in that: The temperature at which the fresh tobacco leaves in S202 are sealed and stored away from light is (20-25)°C.

9. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 6, characterized in that: The chemical components of the fresh tobacco leaves are total sugar, reducing sugar, total nitrogen and total alkaloids.

10. The method for determining significant changes in chemical components of fresh tobacco leaves based on CIE-Lab color space values ​​according to claim 7, characterized in that: Also includes: S204. Compare Tc with tc to confirm the accuracy of the time when the chemical composition of the fresh tobacco leaves undergoes significant changes.

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