Method for discriminating producing area of early spring green tea of golden tea

Abstract

The invention discloses a golden tea early spring green tea producing area distinguishing method, and relates to the technical field of tealeaves, the golden tea early spring green tea producing area distinguishing method comprises the following steps: material collection, reagent and equipment preparation, treatment method and result analysing, 48 mineral element components in early spring green tea in six main golden tea producing areas in Hunan are accurately measured by adopting ICP-MS, and the content of the mineral element components in the early spring green tea is measured; according to the method, fingerprints of mineral elements of golden tea from different producing areas are obtained, 44 elements such as Li, Na, K and the like with significant difference, Baojing, Jiyi, chlamydoma and Guo Zhang in four producing areas in Xiangzhou Hunan are screened out, due to the fact that geographic positions are close, the contents of the obtained elements are close, PCA and OPLS-DA discriminant analysis shows that samples in the producing areas are obviously gathered in respective characteristic areas, and the content of the obtained elements is close to the content of the obtained elements in the producing areas in the Xiangzhou Hunan. The production places of the golden green tea in the main production area of Hunan can be effectively distinguished and identified.

Description

Technical Field

[0001] The invention relates to the technical field of green tea origin identification, in particular to a method for identifying the origin of golden tea early spring green tea. Background Art

[0002] Golden Tea is one of Hunan's five major local specialty tea germplasm resources. Due to its advantages such as early germination, high yield, excellent quality, and strong adaptability, it has become one of Hunan's leading premium green tea varieties. The early spring green tea produced from it is characterized by its fragrant, green, fresh, and mellow qualities. Golden Tea originates from Huangjin Village, Hulu Town, Baojing County, Xiangxi Autonomous Prefecture. In recent years, Xiangxi Prefecture has seized the strategic opportunity of the "100 Billion Hunan Tea" initiative to promote the high-quality development of the Xiangxi Golden Tea industry. The main production area has expanded from Baojing County to several counties and cities within the "Greater Xiangxi" region, including Jishou, Guzhang, and Huayuan. Golden Tea from different producing areas exhibits significant differences in quality and price. Some tea products from non-origin regions are being sold as inferior products, leading to market chaos, consumer infringement, and diminished brand credibility. Therefore, the development of a method for tracing and identifying the origin of Golden Tea is urgently needed to protect the brand reputation and consumer rights of tea from origin.

[0003] Tea trees are perennial plants whose growth and development are influenced by the regional environment for a long time, which gives them unique geographical fingerprint information. With the rapid development of modern instruments, the discipline of tea science has carried out a series of explorations in the direction of origin traceability, which can be summarized into three major traceability types based on technical means: organic composition, optical spectrum, and element fingerprint. The organic composition and optical spectrum of tea, a plant-based food, are not only affected by many regional factors such as soil, climate, and ecological environment, but are also closely related to tea variety, processing methods, and storage methods. The mineral elements in tea can objectively reflect information such as its growth environment and farming methods, and do not change with changes in processing and storage methods. Therefore, mineral element fingerprint analysis is one of the currently reliable tea origin traceability technologies. Inductively coupled plasma mass spectrometry (ICP-MS) is a mineral element trace detection technology. To this end, we have improved the above-mentioned existing technologies based on actual usage. Summary of the Invention

[0004] The purpose of this section is to summarize some aspects of the embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract of the specification and the title of the invention of this application to avoid blurring the purpose of this section, the abstract of the specification and the title of the invention, and such simplifications or omissions cannot be used to limit the scope of the invention.

[0005] In view of the above problems and / or the problems existing in the prior art, the present invention is proposed.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for identifying the origin of golden tea early spring green tea comprises the following steps:

[0008] S1: Collect materials. A total of 138 early spring green tea samples made from one bud and one leaf of the Baojing Golden Tea No. 1 tea plant variety were collected from different production areas in Hunan, including 55 samples from Baojing production area (BJ), 28 from Jishou production area (JS), 15 from Guzhang production area (GZ), 15 from Huayuan production area (HY), 15 from Shimen production area (SM), and 15 from Changsha production area (CS).

[0009] S2: Preparation of reagents and equipment. The reagents used are nitric acid solution and 48 element mixed standard solutions. The equipment used are elemental analysis equipment (ICP-MS), pressure digestion tank, constant temperature drying oven and analytical balance.

[0010] S3: processing methods, which include sample pretreatment, mineral element determination, and data processing;

[0011] S4: Result analysis, among which, firstly, 48 mineral elements in the golden tea early spring green tea from different production areas in Hunan were determined based on the mixed standard solution of 48 elements to determine the element differences, and then PCA analysis was performed on the elements with high content and extremely significant difference in the samples, and then OPLS-DA was used to perform discriminant analysis on the samples, and finally Fisher linear discriminant was used to obtain the element index to discriminate the origin of golden tea in the main production areas of Hunan, and the component discriminant model was obtained.

[0012] Further: The sample pretreatment method in step S3 includes the following steps: accurately weighing 0.2g of dry tea powder sample into a pressure digestion tank, adding 5mL of nitric acid solution, soaking overnight, placing it in a constant temperature drying oven for digestion, adjusting the constant temperature drying oven to three constant temperature stages, and then cooling to room temperature, heating the solution until it is almost dry, washing the remaining digestion solution into a 25mL volumetric flask, making up the volume with 1% nitric acid, mixing well for standby use to prepare a sample solution, and at the same time preparing a blank solution.

[0013] Furthermore: the method for determining the mineral elements in step S3 comprises the following steps: introducing the blank solution and the sample solution into an ICP-MS in sequence for element content determination, wherein the instrument power is set to 1550W;

[0014] Plasma flow rate 17L / min;

[0015] Auxiliary gas flow rate 0.8L / min;

[0016] Atomizing gas flow rate is 0.7986L / min;

[0017] The above steps were repeated 3 times.

[0018] Furthermore: the data processing method in step S3 includes the following steps: SPSS 26.0 is used to perform data statistics through variance analysis, post hoc multiple comparisons and Fisher discriminant analysis;

[0019] Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed using SIMCA 14.1 multivariate software;

[0020] GraphPad Prism 9 and Myvi Cloud Platform were used for graphing.

[0021] Further: the three constant temperature stages of the constant temperature drying oven are:

[0022] 80℃ for 2h;

[0023] 120℃ for 2h;

[0024] Then raise the temperature to 160℃ and maintain for 4h.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] The present invention uses ICP-MS to accurately determine 48 mineral element components in the early spring green tea of the six main golden tea producing areas in Hunan, obtains the mineral element fingerprints of golden tea from different production areas, and screens out 44 elements with significant differences, such as Li, Na, and K. The production areas of Baojing, Jishou, Huayuan, and Guzhang in the four Xiangxi prefectures are geographically close, and the obtained element contents are relatively close. PCA and OPLS-DA discriminant analysis show that the samples from each production area are obviously clustered in their respective characteristic areas, which can effectively distinguish and identify the production areas of golden tea green tea in the main production areas of Hunan. Fisher linear discriminant analysis is used to obtain the discriminant model of the six production areas, and 10 elements such as Ba, Al, B, Sm, K, Ga, Te, Rb, Co, and Eu are introduced into the discriminant model. The overall prediction accuracy of the training set and the test set is over 90%, indicating that the origin traceability of golden tea early spring green tea based on mineral element fingerprints is feasible.

[0027] Other features and advantages of the present application will be described in the following description, and in part will become apparent from the description, or will be understood by practicing the present application. The purpose and other advantages of the present application can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings.

[0028] The technical solution of the present application is further described in detail below through the accompanying drawings and examples. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is the PCA score projection diagram of the golden tea green tea sample of the present invention;

[0031] Figure 2 This is the OPLS-DA analysis chart of the golden tea green tea sample of the present invention;

[0032] Figure 3 This is a table showing the mineral element content of golden tea early spring green tea from different production areas in Hunan Province;

[0033] Figure 4 This is a table diagram of the principal component variance contribution rate of the present invention;

[0034] Figure 5 This is a table diagram of the prediction accuracy of the training set and test set of the present invention. DETAILED DESCRIPTION

[0035] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0036] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0037] Next, the present invention is described in detail with reference to schematic diagrams. For ease of illustration, when describing embodiments of the present invention, cross-sectional views illustrating device structures may be partially enlarged and not to scale. Furthermore, these schematic diagrams are merely illustrative and should not limit the scope of protection of the present invention. Furthermore, in actual production, three-dimensional dimensions, including length, width, and depth, should be included.

[0038] Furthermore, the term "one embodiment" or "embodiment" herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in various places throughout this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0039] See also Figure 1-5The present invention provides a technical solution: a method for identifying the origin of golden tea early spring green tea, comprising the following steps:

[0040] S1: Collect materials. A total of 138 early spring green tea samples made from one bud and one leaf of the Baojing Golden Tea No. 1 tea plant variety were collected from different production areas in Hunan, including 55 samples from Baojing production area (BJ), 28 from Jishou production area (JS), 15 from Guzhang production area (GZ), 15 from Huayuan production area (HY), 15 from Shimen production area (SM), and 15 from Changsha production area (CS).

[0041] S2: Preparation of reagents and equipment. The reagents used are nitric acid solution and 48 element mixed standard solutions. The equipment used are elemental analysis equipment (ICP-MS), pressure digestion tank, constant temperature drying oven and analytical balance.

[0042] S3: processing methods, which include sample pretreatment, mineral element determination, and data processing;

[0043] S4: Result analysis, among which, firstly, 48 mineral elements in the golden tea early spring green tea from different production areas in Hunan were determined based on the mixed standard solution of 48 elements to determine the element differences, and then PCA analysis was performed on the elements with high content and extremely significant difference in the samples, and then OPLS-DA was used to perform discriminant analysis on the samples, and finally Fisher linear discriminant was used to obtain the element index to discriminate the origin of golden tea in the main production areas of Hunan, and the component discriminant model was obtained.

[0044] Among them, preferably, the sample pretreatment method in the S3 step includes the following steps: accurately weighing 0.2g of dry tea powder sample into a pressure digestion tank, adding 5mL of nitric acid solution, soaking overnight, and then placing it in a constant temperature drying oven for digestion, adjusting the constant temperature drying oven to form three constant temperature stages, the three constant temperature stages of the constant temperature drying oven are 80℃ for 2h, 120℃ for 2h, and then rising to 160℃ for 4h, and then cooling to room temperature, heating the solution until it is almost dry, washing the remaining digestion solution into a 25mL volumetric flask, making up the volume with 1% nitric acid, mixing well for standby use to prepare a sample solution, and preparing a blank solution at the same time.

[0045] Preferably, the method for determining the mineral elements in step S3 comprises the following steps: sequentially introducing the blank solution and the sample solution into an ICP-MS for element content determination, wherein the instrument power is set to 1550W;

[0046] Plasma flow rate 17L / min;

[0047] Auxiliary gas flow rate 0.8L / min;

[0048] Atomizing gas flow rate is 0.7986L / min;

[0049] The above steps were repeated 3 times.

[0050] Preferably, the data processing method in step S3 comprises the following steps: performing data statistics using SPSS 26.0 through variance analysis, post hoc multiple comparisons, and Fisher discriminant analysis;

[0051] Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed using SIMCA 14.1 multivariate software;

[0052] GraphPad Prism 9 and Myvi Cloud Platform were used for graphing.

[0053] It should be noted that in the result analysis, the determination results of 48 mineral elements in the early spring green tea of Huangjincha from different origins in Hunan are shown in Figure 3 The results show that the contents of various mineral elements in the samples vary greatly.

[0054] Among them, K content is relatively high, with an average content of 13891 mg / kg, followed by P (4955 mg / kg). The average content of elements such as Ca, Mg, Mn, Fe, and Al ranges from 125 to 1899 mg / kg, and the content of elements such as Na, Zn, Rb, Ni, Cu, Ba, B, Sr, Li, and Ti ranges from 2 to 150 mg / kg. The content of other elements is all below 1 mg / kg. This shows that tea plants have a consistent ability to accumulate essential elements, while non-essential elements may be affected by variety, origin, and cultivation methods.

[0055] The significance analysis showed that except for Cr, La, Ce, Tb and other elements, the other 44 elements showed significant differences (P<0.05).

[0056] Seven elements including B, Ba, Eu, Ho, Tm, Yb and Lu are found in the Baojing production area;

[0057] There are 8 elements in the Jishou production area, including Na, Mg, P, Ca, Mo, Rh, Cd, and Sn;

[0058] Two elements, Mn and Tl, are found in the Guzhang production area;

[0059] Two elements, Se and Sb, are found in the Huayuan production area;

[0060] Ten elements including Al, Ti, V, Fe, Cu, Y, Te, Gd, Dy and Yb in the Shimen production area;

[0061] The contents of three elements, Cu, Cs, and Pb, in the Changsha production area were significantly higher than those in other production areas (P<0.05); the contents of four elements, Be, V, Er, and Pb, in the Jishou production area, Zn in the Guzhang production area, Co, Sr, Pr, and Ba in the Huayuan production area, Mn and Co in the Shimen production area, and P, K, and Ni in the Changsha production area were significantly lower than those in other production areas (P<0.05). There was no element in the Baojing production area that was significantly lower than that in other production areas.

[0062] In order to obtain the clustering trend and characteristics of origin categories of Huangjincha early spring green tea samples from the main production areas of Hunan, PCA was performed on 34 highly significant and differential elements in 138 samples, and a total of 11 principal components were extracted, with eigenvalues greater than 1 and a cumulative variance contribution rate of 82.782%. The results are shown in Figure 3. Figure 4 .

[0063] exist Figure 1 From the projection diagram of the principal component scores of PC1 and PC2, we can see that the golden tea and green tea from the six main producing areas in Hunan show a good category clustering trend. Baojing is geographically close to Jishou and Guzhang, and the measured element contents are relatively close, so there is some overlap in the projection.

[0064] In order to find a more effective method to identify the origin of golden tea, OPLS-DA was used to conduct discriminant analysis. Figure 2 As shown in A, the six groups of samples are significantly distinguished, R 2 X and R 2 Y were 0.641 and 0.883 respectively. After 200 permutation tests, the model prediction index Q 2 is 0.828;

[0065] Q 2 The intersection of the regression line and the vertical axis is less than zero ( Figure 2 B), indicating that the model is well constructed.

[0066] Use the variable important in projection (VIP) value greater than 1 to screen the difference elements. Figure 2 C shows that the elements with VIP>1 are Ba, Al, B, Sm, K, Ga, Te, Rb, Co, Eu and other elements. These 10 elements can be identified as the characteristic difference elements of golden tea and early spring green tea from different production areas in Hunan.

[0067] It should be noted that in Figure 2 In the figure, A is the score projection graph; B is the permutation test graph; C is the VIP value bar chart.

[0068] In addition, the Fisher linear discriminant method in step S4 is to perform Fisher linear discriminant on the standardized data of the contents of 10 characteristic elements of origin with P < 0.05 and VIP > 1, with the ratio of training set to test set samples being 9:1, and the discriminant model is established as follows:

[0069] Category 1 (Baojing production area) = -1.951+0.495*Ba+0.230*B+0.420*Sm+0.719*Te-0.355*Al+0.183*Ga+0.384*K-0.554*Rb+0.217*Co+0.079*Eu;

[0070] Category 2 (Changsha production area) = -5.405-0.267*Ba-0.291*B+0.005*Sm-0.880*Te-0.528*Al-0.409*Ga-1.487*K+1.692*Rb+0.216*Co-0.620*Eu;

[0071] Category 3 (Guzhang production area) = -3.108-0.252*Ba-0.241*B-0.067*Sm-0.504*Te+0.353*Al+0.449*Ga-0.405*K-0.853*Rb-0.336*Co-0.148*Eu;

[0072] Category 4 (Huayuan production area) = -4.142-0.952*Ba+0.041*B-0.050*Sm-0.763*Te-0.511*Al+0.119*Ga-0.553*K+1.060*Rb-0.486*Co-0.536*Eu;

[0073] Category 5 (Jishou production area) = -2.582-0.719*Ba-0.116*B-0.637*Sm-0.353*Te-0.116*Al-0.351*Ga+0.477*K-0.489*Rb+0.010*Co+0.634*Eu;

[0074] Category 6 (Shimen production area) = -4.596+0.807*Ba+0.073*B-0.124*Sm+0.499*Te+1.812*Al+0.150*Ga+0.375*K+0.724*Rb-0.249*Co-0.159*Eu;

[0075] The accuracy of the training set and the test set is the proportion of samples that are predicted to belong to a certain category when they are actually in that category; the recall rate is the proportion of samples that are correctly predicted to belong to a certain category when they are actually in that category; the F1-score value is a weighted comprehensive indicator of the accuracy rate and recall rate; the values of these three indicators are positively correlated with the accuracy of the model.

[0076] Depend on Figure 5 The overall prediction accuracy of the 123 training set samples was 94.4%, with accuracy exceeding 90% for each category. The overall recall was 94.3%, with three categories achieving 100% recall. The F1-score values were all above 90%. The overall prediction accuracy, recall, and F1-score values for the 14 test set samples were all above 95%. With the exception of the Jishou production area, the prediction accuracy reached 100% for all samples. The slightly lower accuracy in Jishou may be due to variations in soil element content caused by the application of organic fertilizers in some areas of the region. In summary, the model fit between the training and prediction sets was good, indicating that the 10 element indicators (Ba, Al, B, Sm, K, Ga, Te, Rb, Co, and Eu) are effective in discriminating the origin of golden tea from the main production areas of Hunan.

[0077] It will be appreciated that in the development of any actual embodiment, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will, for those of ordinary skill having the benefit of this disclosure, be a routine undertaking of design, fabrication, and production without undue experimentation.

[0078] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for identifying the origin of golden tea early spring green tea, characterized by: The steps include: S1: Collect materials. A total of 138 early spring green tea samples made from one bud and one leaf of the Baojing Golden Tea No. 1 tea plant variety were collected from different production areas in Hunan, including 55 samples from Baojing production area (BJ), 28 from Jishou production area (JS), 15 from Guzhang production area (GZ), 15 from Huayuan production area (HY), 15 from Shimen production area (SM), and 15 from Changsha production area (CS). S2: Preparation of reagents and equipment. The reagents used are nitric acid solution and 48 element mixed standard solutions. The equipment used are elemental analysis equipment (ICP-MS), pressure digestion tank, constant temperature drying oven and analytical balance. S3: processing methods, which include sample pretreatment, mineral element determination, and data processing; S4: Result analysis, among which, firstly, 48 mineral elements in the golden tea early spring green tea from different production areas in Hunan were determined based on the mixed standard solution of 48 elements to determine the element differences, and then PCA analysis was performed on the elements with high content and extremely significant difference in the samples, and then OPLS-DA was used to perform discriminant analysis on the samples, and finally Fisher linear discriminant was used to obtain the element index to discriminate the origin of golden tea in the main production areas of Hunan, and the component discriminant model was obtained.

2. The method for identifying the origin of golden tea early spring green tea according to claim 1, characterized in that: The sample pretreatment method in step S3 comprises the following steps: accurately weighing 0.2 g of dry tea powder sample into a pressure digestion tank, adding 5 mL of nitric acid solution, soaking overnight, and then placing the sample into a constant temperature drying oven for digestion. The constant temperature drying oven is adjusted to three constant temperature stages, and then cooled to room temperature, and the solution is heated until almost dry. The remaining digestion solution is washed into a 25 mL volumetric flask, and the volume is adjusted with 1% nitric acid. The sample solution is mixed and then prepared for standby use, and a blank solution is prepared at the same time.

3. The method for identifying the origin of golden tea early spring green tea according to claim 1, characterized in that: The method for determining the mineral elements in step S3 comprises the following steps: sequentially introducing the blank solution and the sample solution into an ICP-MS for element content determination, wherein the instrument power is set to 1550W; Plasma flow rate 17L / min; Auxiliary gas flow rate 0.8L / min; Atomizing gas flow rate is 0.7986L / min; The above steps were repeated 3 times.

4. The method for identifying the origin of golden tea early spring green tea according to claim 1, characterized in that: The data processing method in step S3 includes the following steps: SPSS 26.0 is used for data statistics through variance analysis, post hoc multiple comparison and Fisher discriminant analysis; Principal component analysis (PCA) and orthogonal partial least squares discriminant analysis (OPLS-DA) were performed using SIMCA 14.1 multivariate software; GraphPad Prism 9 and Myvi Cloud Platform were used for graphing.

5. The method for identifying the origin of golden tea early spring green tea according to claim 2, characterized in that: The three constant temperature stages of the constant temperature drying oven are: 80℃ for 2h; 120℃ for 2h; Then raise the temperature to 160℃ and maintain for 4h.

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