Method for measuring tea pigment content in Liupao tea based on chromatic aberration system

Abstract

The invention discloses a method for measuring the content of tea pigment in Liupao tea based on a chromatic aberration system.The method belongs to the field of tea component detection.The method comprises the following steps that any Liupao tea sample is collected, and the content of the tea pigment in the Liupao tea sample is measured through a chemical analysis method; brewing the tea sample according to a tea-water ratio of 1: 50, and measuring a color difference value of tea soup by using a color difference meter to obtain color difference data; constructing a tea pigment content prediction model based on the tea pigment content and the color difference data, and inspecting the tea pigment content prediction model; and predicting the tea pigment content of a to-be-detected tea sample based on the tea pigment content prediction model. The method established by the invention has the advantages of simple operation process, no need of complex pretreatment, obvious shortening of the detection period, improvement of the detection efficiency, reduction of the detection cost, high model accuracy, good precision, realization of rapid detection of the tea pigment of the Liupao tea, and suitableness for detection in the processing process of the Liupao tea.

Description

Technical Field

[0001] This invention belongs to the field of tea component detection technology, and in particular relates to a method for determining the tea pigment content in Liubao tea based on a color difference system. Background Technology

[0002] Liubao tea, a famous historical tea from Guangxi, is renowned for its four unique characteristics: red color, strong flavor, aged quality, and mellow taste. With a history of over 1500 years, it is a national geographical indication agricultural product. In recent years, the Liubao tea industry has developed rapidly, and consumers have increasingly higher demands for tea quality. The biochemical components of Liubao tea are fundamental to its quality. The degree of red color and intensity of Liubao tea is related to the evaluation of the tea liquor color. This quality characteristic originates from the tea pigment components in the tea liquor, including thearubigins, theaflavins, and theabrownins, all of which are oxidation products of polyphenols and affect the color composition of the tea liquor. Among these, the thearubigin and theabrownin content are the most important influencing Liubao tea. Detecting the thearubigin and theabrownin content in tea can provide a theoretical reference for tea quality evaluation.

[0003] Currently, the detection of pigment components in Liubao tea mainly relies on chemical analysis methods, as exemplified by patents CN202111655322 "Method for Determining the Theabrownin Content in Liubao Tea", CN113376103A "A Method and Application for Determining the Content of Tea Components Using Hyperspectral Imaging Technology", and CN202310158541 "A Method for Detecting the Types and Content of Tea Pigments in Tea and Tea Products". These methods require demanding experimental environments, are cumbersome, involve complex pretreatment, have long testing cycles for single samples, and involve complex data processing, resulting in low efficiency. While they offer high accuracy, they are difficult to apply to rapid detection and process control in production settings. Therefore, this invention proposes a method for determining the pigment content in Liubao tea based on a color difference system. This method is convenient, rapid, accurate, and low-cost, suitable for rapid detection in production settings, effectively addressing the shortcomings of relying solely on experience to judge the quality of tea liquor in Liubao tea production. Summary of the Invention

[0004] This invention aims to provide a method for determining the tea pigment content in Liubao tea using a colorimetric system. A regression model is established between the color difference data of Liubao tea and the tea pigment components. A colorimeter is used to directly measure the color difference value of the tea infusion, eliminating the need for complex pretreatment. The color difference data is used to calculate the content of tea pigment components in Liubao tea based on the regression model, achieving rapid detection of tea pigments in Liubao tea. The colorimeter can complete three replicates of tea pigment detection for a single sample within 2 minutes, providing technical support for rapid detection, tea quality, and process control at the Liubao tea production and processing site.

[0005] To achieve the above objectives, the present invention provides a method for determining the tea pigment content in Liubao tea based on a color difference system, comprising: Collect any Liubao tea samples and determine the tea pigment content of the Liubao tea samples using chemical analysis methods; The tea sample was brewed at a tea-to-water ratio of 1:50, and the color difference data was obtained by measuring the color difference of the tea soup using a colorimeter. A tea pigment content prediction model is constructed based on the tea pigment content and the color difference data; the tea pigment content prediction model is then tested. The color difference value of the tea soup is measured using a colorimeter, and the tea pigment content is obtained by substituting the color difference value of the tea soup into the tea pigment content prediction model.

[0006] Optionally, the number of Liubao tea samples is greater than 100.

[0007] Optionally, the chemical analysis method is a systematic analysis method; The process of determining the tea pigment content of Liubao tea samples using chemical analysis includes: measuring each Liubao tea sample three times in parallel, and taking the average value to obtain the tea pigment content, which includes theabrownin and thearubigin.

[0008] Optionally, the process of obtaining the tea infusion measured by the colorimeter includes: brewing the tea at a tea-to-water ratio of 1:50 for 2 minutes, then brewing it for another 5 minutes, and taking the tea infusion brewed for 5 minutes as the tea infusion to be tested. The tea brewing process follows national standards and is conducted using professional tasting cups.

[0009] Optionally, the color difference values ​​of the tea infusion being measured include L*, a*, and b*.

[0010] Optionally, the tea pigment content prediction model is constructed based on tea pigment content and tea soup color difference data, and principal component regression or linear regression is used to establish the model.

[0011] Optionally, the indicators for testing the tea pigment content prediction model are goodness of fit test and root mean square error test.

[0012] Optionally, the tea pigment content prediction model constructed based on the tea pigment content and the color difference data is as follows: Theabrownin (%)=10.3173-0.0931L*+0.09065a*+0.049b*; Thearubigin (%) = 1.097928 + 0.049704L* - 0.048396a* - 0.02616b*; Where L* represents luminance, a* represents red-green hue, and b* represents yellow-blue hue.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention establishes a regression model between the pigment content and color difference of Liubao tea samples by measuring the pigment content and color difference value of the tea liquor. A color difference system is used to directly detect the color difference value of the tea liquor, and the regression model can then be used to quickly calculate the pigment content in the tea. No complex pretreatment is required, the detection method is simple to operate, has low requirements for the experimental environment, a short detection cycle, and improves detection efficiency. The equipment investment cost is low, reducing detection costs. The model has high accuracy, good precision, and strong repeatability, and can be used to detect the pigment content of Liubao tea. This provides technical support for the quality evaluation of the tea liquor color in Liubao tea samples during production, and for rapid detection, tea quality, and process control in Liubao tea production. Attached Figure Description

[0014] Figure 1 This is a scatter plot of the theabrownins, thearubigins, and color difference values ​​L*, a*, and b* of the Liubao tea sample in Embodiment 1 of the present invention. Figure 2 This is a flowchart of an embodiment of the present invention. Detailed Implementation

[0015] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way.

[0016] Example 1 like Figure 2 As shown, the process of establishing the data model for the pigment content and color difference of Liubao tea includes: (1) Collection of Liubao tea samples: 120 Liubao tea samples were collected and stored in a -20 degree refrigerator.

[0017] (2) Collection of pigment data of Liubao tea: The content of pigments in tea samples, including thearubigin and theabrownin, was determined by systematic analysis.

[0018] (3) Collection of color difference data: Weigh 3.0g of Liubao tea sample, tea-to-water ratio 1:50, brew twice. The first brew is brewed with 150mL of boiling water for 2 minutes and then the tea soup is filtered out to obtain the first tea soup. The second brew is brewed with 150mL of boiling water for 5 minutes and then the tea soup is filtered out to obtain the second tea soup. The color difference value of the tea soup (L* / a* / b*) is measured using a colorimeter.

[0019] (4) The prediction model for the pigment content of Liubao tea was established based on the pigment content of Liubao tea and the color difference data of the tea soup after 5 minutes of brewing in the two-infusion method.

[0020] (5) The pigment and color difference data of Liubao tea were obtained by principal component regression model and linear regression model. The equations are as follows: Theabrownin (%)=10.3173-0.0931*L+0.09065*a+0.049*b, R 2 It is 0.88; Thearubigin (%) = 1.097928 + 0.049704 * L - 0.048396 * a - 0.02616 * b, R 2 It is 0.83.

[0021] Where L* represents luminance, a* represents red-green hue, and b* represents yellow-blue hue. A scatter plot of the theabrownins, thearubigins, and color difference values ​​L*, a*, and b* of Liubao tea samples is shown below. Figure 1 As shown.

[0022] (6) Model validation: The evaluation index is the coefficient R. 2 Root mean square error (RMSE). 2 The closer the value is to 1, and the lower the RMSE value, the higher the model readiness. The model R established in this embodiment... 2 The mean square error (RMSE) is 0.83 to 0.88, and the root mean square error (RMSE) is 0.59 to 0.91, indicating that the model has good predictive ability.

[0023] Example 2 The difference from Example 1 is that in step 4, the sample uses the color difference data of tea pigment content and 2-minute brewing in the two-infusion method to establish the model.

[0024] The results show that the established model R 2 The mean square error (RMSE) is 0.78 to 0.88, and the root mean square error (RMSE) is 0.68 to 0.90, indicating that the model also has good predictive ability.

[0025] Example 3 The difference from Example 1 is that in step (1), 100 additional tea samples are taken, and in step (3), the tea samples are prepared using a single-infusion method to obtain the tea soup. Specifically, 3.0g of Liubao tea sample is weighed, the tea-to-water ratio is 1:50, and it is infused once with 150mL of boiling water for 5 minutes. The tea soup is then filtered out, and the color difference value (L* / a* / b*) of the tea soup is measured using a colorimeter. A model is established using the tea pigment content and the color difference data from the single-infusion method after 5 minutes of infusion.

[0026] The results show that the established model R 2 The mean square error (RMSE) is 0.57~0.81, and the root mean square error (RMSE) is 0.87~0.95, indicating that the model also has good predictive ability.

[0027] Example 4 As shown in Table 1, the accuracy and precision of the detection method in Example 1 were verified. Forty-five Liubao tea samples were randomly collected, and 3.0g of each sample was weighed. The tea-to-water ratio was 1:50, and the tea was brewed twice. The first brew was with 150mL of boiling water, steeped for 2 minutes, and the tea liquor was filtered out. The second brew was with 150mL of boiling water, steeped for 5 minutes, and the tea liquor was filtered out. The color difference values ​​(L* / a* / b*) of the tea liquor were measured using a colorimeter. The color difference data of the second 5-minute brew was substituted into the regression model in Example 1 to calculate the tea pigment content of the tea samples. The tea pigment content of the tea samples was determined using systematic analysis, and the model predictions were compared with the actual measurements. The results are shown in the table below. The relative errors between the model predictions and actual values ​​were between 0.02% and 0.47% for theaflavins and between 0.01% and 1.49% for thearubigins, both less than 5%, indicating high accuracy of the regression model.

[0028] Table 1

[0029] The method established in Example 1 was used to test any three Liubao tea samples, with six parallel tests performed. The results are shown in the table below. The standard deviation of thearubigin was between 0.14% and 0.29%, and the standard deviation of theabrownin was between 0.20% and 0.30%, indicating that the method has high precision, as shown in Table 2.

[0030] Table 2

[0031] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A method for determining the content of tea pigments in Liupao tea based on a color difference system, characterized in that, The method comprises the following steps: Collecting a plurality of Liubao tea samples, and determining the tea pigment content of the Liubao tea samples by using a chemical analysis method; Brewing the tea samples at a tea-to-water ratio of 1:50, and determining the color difference value of the tea soup by using a color difference meter to obtain color difference data; Constructing a tea pigment content prediction model based on the tea pigment content and the color difference data; Verifying the tea pigment content prediction model; Determining the color difference value of the tea soup by using the color difference meter, and substituting the color difference value of the tea soup into the tea pigment content prediction model to obtain the tea pigment content.

2. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 1, characterized in that, The number of the Liubao tea samples is greater than 100.

3. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 1, characterized in that, The chemical analysis method is a systematic analysis method. The process of determining the tea pigment content of the Liubao tea samples by using the chemical analysis method comprises the following steps: determining the tea pigment content of each Liubao tea sample three times in parallel, and taking the average value to obtain the tea pigment content, wherein the tea pigment includes theabrownine and thearubigin.

4. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 1, characterized in that, The process of obtaining the tea soup determined by using the color difference meter comprises the following steps: brewing for 2 minutes at a tea-to-water ratio of 1:50, then brewing for 5 minutes, and taking the tea soup brewed for 5 minutes as the tea soup to be determined. The brewing process of the tea soup is performed according to the national standard by using a professional evaluation cup.

5. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 4, characterized in that, The color difference value of the tea soup includes L*, a* and b*.

6. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 1, characterized in that, The construction of the tea pigment content prediction model is based on the tea pigment content and the color difference data of the tea soup, and the model is established by using principal component regression or linear regression.

7. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 6, characterized in that, The indexes for verifying the tea pigment content prediction model are the goodness-of-fit test and the root mean square error.

8. The method for determining the content of tea pigments in Liupu tea according to the color difference system of claim 1, characterized in that, The tea pigment content prediction model constructed based on the tea pigment content and the color difference data is as follows: Theabrownine (%) = 10.3173-0.0931L*+0.09065a*+0.049b*; Thearubigin (%) = 1.097928+0.049704L*-0.048396a*-0.02616b*; Wherein, L* is the brightness, a* is the red-green degree, and b* is the yellow-blue degree.

Images