CN108254482B - Method for distinguishing years of white tea based on year white tea characteristic compounds - Google Patents
Method for distinguishing years of white tea based on year white tea characteristic compounds Download PDFInfo
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Abstract
A white tea year discrimination method based on year white tea characteristic compounds belongs to the technical field of tea leaf discrimination. The method establishes 8-CNLinear equation of the content of ethyl-2-pyrrolidone substituted epigallocatechin gallate and the white tea year by measuring the content of 8-CNSubstituting the quantitative result of the-ethyl-2-pyrrolidone substituted epigallocatechin gallate into the linear equation to obtain the predicted value of the year of the white tea sample. The method provides effective technical support for the judgment of the white tea year in the market. The method has the advantages of simple and convenient operation, data quantification, objective result and high discrimination accuracy.
Description
Technical Field
The invention belongs to the technical field of tea leaf discrimination, and particularly relates to a white tea year discrimination method based on year white tea characteristic compounds.
Background
The white tea is one of six traditional tea types in China, belongs to micro-fermented tea, is created in Fujian in China, and is mainly produced in Fuding, political harmony, Jianyang, Songxi and the like. The white tea has various pharmacological actions, is cold and cool in nature and is a good medicine for reducing pathogenic fire commonly used by people, and modern scientific researches show that the white tea has the effects of regulating blood fat, preventing cardiovascular and cerebrovascular diseases, regulating immunologic function, diminishing inflammation, detoxifying, resisting radiation, resisting oxidation, resisting mutation, resisting cancer and the like.
The storage time (years) is important for the taste and aroma quality of the white tea, especially for the biological activity. The folk of Fujian has a statement of 'one-year tea, three-year medicine and seven-year treasure' about the annual white tea, and the market price of the white tea (old white tea) stored for a long time is often several times, even dozens of times, higher than that of the common white tea. However, it is difficult to accurately distinguish the white tea leaves of different years from the aspects of appearance, liquor color, aroma, taste, leaf bottom and the like of the tea leaves, and the distinguishing processThe subjectivity of the Chinese people is large; in addition, no other compound indexes for distinguishing the year of white tea exist at present. The method provides a good opportunity for black-heart merchants to impersonate the old white tea with the old white tea or make the old white tea from the appearance, which seriously disturbs the white tea market and causes great obstruction to the development of the white tea industry. Therefore, a reliable and effective new method is urgently needed to accurately and objectively distinguish the year of the white tea. In our earlier studies, a new component 8-CNThe content of epigallocatechin gallate (substituted by ethyl-2-pyrrolidone) (chemical structural formula shown in figure 1, IUPAC name is (2R,3R) -8- (1-ethyl-5-oxypyrrolidin-2-yl) -5,7-dihydroxy-2- (3,4,5-trihydroxyphenyl) chroman-3-yl 3,4, 5-trihydroxybenzoate) is increased gradually during white tea storage, and shows good linear relation with the storage years. Therefore, the white tea is about to be 8-CNThe content of the-ethyl-2-pyrrolidone substituted epigallocatechin gallate is used as a distinguishing index of the white tea year and is used for identifying and distinguishing unknown white tea years.
Disclosure of Invention
In view of the problems in the prior art, the invention aims to design and provide a technical scheme of a white tea year discrimination method based on a year white tea characteristic compound, and the method provides effective technical support for commercial white tea year discrimination. The method has the advantages of simple and convenient operation, data quantification, objective result and high discrimination accuracy.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
The method for judging the year of the white tea based on the year white tea characteristic compound is characterized in that 8-CNLinear equation of the content of ethyl-2-pyrrolidone substituted epigallocatechin gallate and the white tea year by measuring the content of 8-CNSubstituting the quantitative result of the-ethyl-2-pyrrolidone substituted epigallocatechin gallate into the linear equation to obtain the predicted value of the year of the white tea sample.
The compound is based on the characteristics of the annual white teaThe method for judging the year of white tea is characterized in that 8-CNThe linear equation of the content of the ethyl-2-pyrrolidone-substituted epigallocatechin gallate and the white tea year is as follows: y =0.0134 x-0.8819.
The method for distinguishing the year of the white tea based on the year white tea characteristic compound is characterized by comprising the following steps of: the method specifically comprises the following steps:
1) Extracting the content of the white tea: collecting white tea samples, grinding into powder, accurately weighing a small amount of white tea powder, extracting chemical components in the white tea powder by using a methanol water solution, and taking supernate after high-speed centrifugation;
2) new year white tea characteristic compound 8-CN-quantitative analysis of ethyl-2-pyrrolidone substituted epigallocatechin gallate;
3) Establishing a linear equation for judging the year of the white tea through a series of white tea samples of known years;
4) 8-value of unknown white tea sampleCNSubstituting the quantitative result of the ethyl-2-pyrrolidone substituted epigallocatechin gallate into a linear equation for white tea year discrimination so as to obtain an estimated value of the white tea sample year.
The discrimination method is characterized in that the small amount of the white tea powder in the step 1) is 0.1 g.
The distinguishing method is characterized in that the proportion of the methanol aqueous solution in the step 1) is 40-95%, the extraction temperature is 50-100 ℃, the extraction time is 10-60 minutes, and the volume is 10 milliliters.
The determination method is characterized in that the rotation speed of the high-speed centrifugation in the step 1) is 5000-.
The discrimination method is characterized in that the quantitative analysis in the step 2) is based on an external standard curve.
The method is characterized in that the linear equation for judging the year of the white tea is established in the step 3), and the linear equation is 8-CNWhite tea with content of (E) -ethyl-2-pyrrolidone substituted epigallocatechin gallate as x variableThe year of the sample is the y variable.
The distinguishing method is characterized in that 1 decimal point is reserved for the pre-estimation value of the year of the white tea sample in the step 4).
Said 8-CN-application of epigallocatechin gallate substituted by ethyl-2-pyrrolidone as a characteristic compound for distinguishing the year of white tea.
the invention distinguishes the year of the white tea by the year white tea characteristic compound, and has the following advantages: 1) the compound used as the white tea year discrimination index is 8-C N-ethyl-2-pyrrolidone substituted epigallocatechin gallate, original creative; 2) human subjective factors related to the conventional white tea year judgment mainly based on tea leaf evaluation are eliminated, unified quantitative data are provided, the result is objective, the inspection can be completed without professional tea leaf evaluation high-end talents, and the requirements on personnel are greatly reduced; 3) the experimental operation and the data analysis are rapid, simple and convenient.
Drawings
FIG. 1 is a schematic view of the processC NThe chemical structural formula of the (E) -ethyl-2-pyrrolidone substituted epigallocatechin gallate.
FIG. 2 is a schematic view of the process of FIG. 8-C NAn extracted ion current chromatogram (A) and a mass spectrum (B) of a liquid chromatography-mass spectrometry analysis of the ethyl-2-pyrrolidone-substituted epigallocatechin gallate.
Fig. 3 is a linear equation for the year discrimination of white tea.
Detailed Description
the following examples of the present invention are described in detail with reference to the accompanying tables: the present embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation manner and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.
Example 1:
And (3) identification and judgment of the white tea year: by 8-C NMeasuring the content of-ethyl-2-pyrrolidone substituted epigallocatechin gallate, and establishing linear discriminant model with yearAnd carrying out year identification and judgment on the white tea samples of unknown years.
the method comprises the following specific operation steps:
1) 18 samples of the pekoe white tea and 26 samples of the white peony white tea in different years are collected, ground into powder and stored at the temperature of-20 ℃.
2) Determination of 8 + in white tea samplesC N-content of ethyl-2-pyrrolidone-substituted epigallocatechin gallate:
Accurately weighing 0.1 g of white tea sample powder into a centrifuge tube, adding 70% methanol aqueous solution, extracting in 70 ℃ water bath for 30 minutes, centrifuging in a high-speed centrifuge at 10000 rpm for 10 minutes, taking 1mL of supernatant into a liquid phase sample injection vial, and performing liquid chromatography-mass spectrometry analysis.
The chromatographic conditions for LC-MS are as follows: the chromatographic column was a Zorbax Eclipse Plus C18 column (150 mm. times.3.0 mm, 1.8 μm, Agilent, USA), mobile phase A was 0.1% formic acid-water, and phase B was methanol; the sample injection amount is 3 mu L; the flow rate was 0.4 mL/min-1(ii) a The column temperature was 40 ℃; the mobile phase linear gradient elution was: 0 min, 10% phase B; 4 min, 15% phase B; 7 min, 25% phase B; 9 min, 32% phase B; 16 min, 40% phase B; 22 min, 55% phase B; 28 min, 95% phase B; 30 minutes, 95% phase B; the post column equilibration time was 5 minutes.
The mass spectrum conditions of the LC-MS are as follows: electrospray ionization (ESI); the scanning mode is a positive ion mode; the capillary voltage is 3500V; the temperature and flow rate of the drying gas are respectively 300 ℃ and 8 L.min-1(ii) a The pressure of atomizing gas is 35 psi; the temperature and flow rate of the sheath gas are respectively 300 ℃ and 11 L.min-1(ii) a The mass spectrum scanning range has a mass-to-charge ratio (m/z) of 100-1000.
8-C NThe peak condition of the-ethyl-2-pyrrolidone-substituted epigallocatechin gallate under the chromatography-mass spectrometry condition is shown in figure 2. The content thereof is 8-C N-ethyl-2-pyrrolidone substituted epigallocatechin gallate standards were quantitated by external standard method. 18 samples of pekoe silver needle, 8-C Nthe content of the (E) -ethyl-2-pyrrolidone-substituted epigallocatechin gallate is shown in Table 1. With whiteIncrease of the year of tea, 8-C NThe content of epigallocatechin gallate substituted by ethyl-2-pyrrolidone is also increased.
TABLE 1 white tea year and 8-C N-ethyl-2-pyrrolidone substituted epigallocatechin gallate content
。
3) Establishment of linear equation for white tea year discrimination
8 + in white tea sampleC NLinear regression was performed with the content of ethyl-2-pyrrolidone-substituted epigallocatechin gallate (μ g/g) as the x variable and the year (year) of the white tea sample as the y variable. The linear equation y =0.0134x-0.8819 for the year discrimination of the white tea is obtained,r 2= 0.8025 (fig. 3).
4) white tea year identification and discrimination
Entrust professional to purchase representative pekoe silver needle and white peony white tea sample 5 respectively, do not reveal its year information in advance for the operating personnel, operate according to instruction manual step 1-4, and appraise and differentiate its year. The experimental result shows that the year estimated value is well matched with the actual year, the discrimination error is 0.3-0.7 year, and the accuracy is high, as shown in Table 2.
TABLE 2.10 samples of white tea 8-C N-ethyl-2-pyrrolidone substituted epigallocatechin gallate content, actual year and predicted year
。
Claims (10)
1. A white tea year discrimination method based on year white tea characteristic compounds is characterized in that 8-fold materials in white tea are establishedCNlinear equation of the content of ethyl-2-pyrrolidone substituted epigallocatechin gallate and the white tea year by measuring the content of 8-CNPyridine derivatives of (E) -ethyl-2-pyrrolidone substituted epigallocatechin gallateThe quantitative results are substituted into the above linear equation to obtain an estimated value of the year of the white tea sample.
2. the method as claimed in claim 1, wherein the method for determining the year of white tea based on the year white tea characteristics compound is characterized in that 8-CNthe linear equation of the content of the ethyl-2-pyrrolidone-substituted epigallocatechin gallate and the white tea year is as follows: y =0.0134 x-0.8819.
3. A method for judging the year of white tea based on a compound characteristic of the year white tea as set forth in claim 1, wherein: the method specifically comprises the following steps:
1) Extracting the content of the white tea: collecting white tea samples, grinding into powder, accurately weighing a small amount of white tea powder, extracting chemical components in the white tea powder by using a methanol water solution, and taking supernate after high-speed centrifugation;
2) New year white tea characteristic compound 8-CN-quantitative analysis of ethyl-2-pyrrolidone substituted epigallocatechin gallate;
3) Establishing a linear equation for judging the year of the white tea through a series of white tea samples of known years;
4) 8-value of unknown white tea sampleCNSubstituting the quantitative result of the ethyl-2-pyrrolidone substituted epigallocatechin gallate into a linear equation for white tea year discrimination so as to obtain an estimated value of the white tea sample year.
4. a method according to claim 3, wherein the amount of the white tea powder in the step 1) is 0.1 g.
5. The discrimination method as claimed in claim 3, wherein the ratio of the methanol aqueous solution in the step 1) is 40 to 95%, the extraction temperature is 50 to 100 ℃, the extraction time is 10 to 60 minutes, and the volume is 10 ml.
6. the method as claimed in claim 3, wherein the rotation speed of the high speed centrifugation in step 1) is 5000-15000 rpm for 5-20 minutes.
7. The method according to claim 3, wherein the quantitative analysis in step 2) is a quantitative analysis based on an external standard curve.
8. The method as claimed in claim 3, wherein the linear equation for the determination of the year of white tea in step 3) is 8-CNThe content of the-ethyl-2-pyrrolidone substituted epigallocatechin gallate is variable x, and the year of the white tea sample is variable y.
9. A discrimination method as claimed in claim 3, characterized in that the predicted value of the year of the white tea sample in the step 4) is retained at 1 decimal point.
10.8-CN-application of epigallocatechin gallate substituted by ethyl-2-pyrrolidone as a characteristic compound for distinguishing the year of white tea.
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