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CN-121978262-A - Method for distinguishing years of Jingyang Fu tea

CN121978262ACN 121978262 ACN121978262 ACN 121978262ACN-121978262-A

Abstract

The invention discloses a method for distinguishing the year of Jingyang Fu tea, which belongs to the technical field of tea year distinguishing, wherein a headspace solid-phase microextraction gas chromatograph-mass spectrometer is adopted to measure and analyze Fu tea samples in different storage years, a machine learning method is integrated according to the characteristics of volatile organic compounds, a Fu tea storage year prediction model is constructed, and the Fu tea storage year is distinguished through the prediction model. The method for judging the year of the Fu tea in the Jingyang is simple in processing steps, convenient to operate, suitable for processing and screening large-scale samples, stable and mature in headspace solid-phase microextraction gas chromatography-mass spectrometer technology, capable of predicting the storage year of the Fu tea body by utilizing the content values of 10 compounds and combining error reference values, simple and objective in operation, free of interference of human factors and capable of remarkably improving the accuracy of identifying the storage year of the Fu tea.

Inventors

  • FENG KEWEI
  • SUN XINYUE
  • WANG YUAN
  • ZHANG SHUTING
  • YUE TIANLI
  • YUAN YAHONG
  • SHENG QINGLIN

Assignees

  • 西北大学

Dates

Publication Date
20260505
Application Date
20260122

Claims (7)

  1. 1. The method for distinguishing the year of the Jingyang Fu tea is characterized by comprising the following steps of: step one, collecting and preprocessing Jingyang Fu tea samples with different storage years, and measuring volatile organic compounds in the samples; screening out key volatile organic compounds with VIP value more than 1 from the volatile organic compounds in the first step based on orthogonal partial least square regression and a support vector machine; Step three, constructing a year prediction model according to the key volatile organic compounds obtained in the step two; and step four, performing year discrimination on the Fu tea samples with unknown storage year by using the year prediction model obtained in the step three.
  2. 2. The method for distinguishing the year of the Fu tea of the Jingyang according to claim 1, wherein in the first step, the pretreatment method comprises the steps of weighing sample tea powder of the Fu tea of the Jingyang, placing the sample tea powder into a 20mL headspace bottle, adding sodium chloride, adding 2-octanol internal standard solution, adding boiling water for brewing, and fully oscillating and uniformly mixing to carry out headspace solid-phase microextraction.
  3. 3. The method for distinguishing the year of the Fu tea of the Jingyang according to claim 1, wherein in the first step, the weighing amount of the sample tea powder of the Fu tea of the Jingyang is 0.5-2g, the adding amount of sodium chloride is 0.5-2g, the using amount of the 2-octanol internal standard solution is 5-10 mu m, the concentration is 1mg/mL, and the using amount of boiling water is 3-10mL.
  4. 4. The method for distinguishing the year of the Fu tea of the Jingyang according to claim 1, wherein in the first step, the conditions of headspace solid-phase microextraction are that the aging temperature of an extraction head is 250-300 ℃, the aging time is 3-10min, the temperature of a heating box is 80-100 ℃, the heating time is 30-60min, the pumping time is 30-60min, and the resolution is 240-250 ℃ for 3-10min.
  5. 5. The method for distinguishing the year of the Jingyang Fu tea according to claim 1 is characterized in that in the first step, GC parameters are an HP-5MS chromatographic column, 30m multiplied by 0.25mm multiplied by mu m, carrier gas He, purity of >99.999 percent and flow rate of 1.8mL/min, the sample injection mode is not split, the temperature of the sample injection port is 240 ℃, the temperature raising program is that the initial temperature is kept at 40 ℃ for 3-10min, the temperature is kept at 2 ℃ to 170 ℃ for 3-10min, and the temperature is kept at 8 ℃ to 240 ℃ for 3-10min; MS conditions are that the temperature of the electron ion source is 200 ℃, the ionization energy of EI is 70eV, the mass scanning range m/z is 30-500, and the temperature of the switching port is 220 ℃.
  6. 6. The method for distinguishing the year of the Fu tea of Jingyang according to claim 1, wherein in the second step, qualitative analysis is carried out by using NIST spectrum library search in combination with retention index calculation, quantitative analysis is carried out by using an internal standard method, the content of the volatile compounds is relatively quantified by using 2-octanol as an internal standard in quantitative analysis, orthogonal partial least squares discriminant analysis is carried out by using SIMCA 14.1 software, and the key volatile organic compounds with VIP value of >1 are screened out as variables of sample data.
  7. 7. The method for distinguishing the year of the Fu tea of the Jingyang according to claim 1, wherein in the third step, the first 10 key volatile organic compounds with VIP value more than 1 are used as modeling variables to obtain a prediction model, wherein the prediction model is shown as a formula (I): Formula (I); Wherein R1 is methyl salicylate content, R2 is 3-hexene-1-ol content, R3 is (1R, 2R,3S, 5R) - (-) -2, 3-pinanediol content, R4 is 6-methyl-5-hepten-2-one content, R5 is phenethyl alcohol content, R6 is alpha-terpineol content, R7 is (Z) -3, 7-dimethyl-2, 6-octadien-1-ol content, R8 is benzyl alcohol content, R9 is 1-Xin Xi-3-ol content, and R10 is trans-beta-ionone content.

Description

Method for distinguishing years of Jingyang Fu tea Technical Field The invention relates to the technical field of tea year identification, in particular to a method for identifying the year of Jingyang Fu tea. Background Fuzhuan tea is black tea produced in China through post fermentation, is also called as Fuzhuan tea, and is prepared from raw black tea through a series of unique preparation processes. Tea aroma is one of main sensory characteristics reflecting tea quality, and key odor substances of tea with different aroma types are identified, so that the basic theory of tea aroma chemistry is enriched, and scientific reference is provided for identification and control of tea aroma quality. In the current report of the influence of the storage life on the flavor of tea leaves, the influence of the storage life on the flavor of the old fully fermented tea like Fuzhuan tea is blank. The related research is focused on Liupu tea, pu' er tea, green tea and white tea samples, and the dynamic evolution of the characteristic flavor of Fu tea in the long-term storage process lacks system tracking and data support. And, how to achieve accurate predictions of storage years based on these chemical fingerprints remains blank. Disclosure of Invention The invention aims to provide a method for distinguishing the year of Jingyang Fu tea, which has the advantages of simple processing steps and convenient operation, is suitable for processing and screening large-scale samples, is stable and mature in a headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-MS) technology, can be completed by only needing less than 2g of tea samples and 3-10mL of purified water in the headspace solid-phase microextraction process, avoids the waste of the tea samples, can predict the storage year of Fu tea bodies by utilizing the content values of 10 compounds to establish a linear regression model and a support vector machine classification model and combining error reference values, is simple and objective to operate, eliminates the interference of human factors, and can remarkably improve the accuracy of identifying the storage year of Fu tea. In order to achieve the purpose, the invention provides a method for distinguishing the year of Jingyang Fu tea, which comprises the following steps: step one, collecting and preprocessing Jingyang Fu tea samples with different storage years, and measuring volatile organic compounds in the samples; screening out key volatile organic compounds with VIP value more than 1 from the volatile organic compounds in the first step based on orthogonal partial least square regression and a support vector machine; Step three, constructing a year prediction model according to the key volatile organic compounds obtained in the step two; and step four, performing year discrimination on the Fu tea samples with unknown storage year by using the year prediction model obtained in the step three. Preferably, in the first step, the pretreatment method comprises the steps of weighing Jingyang Fu tea sample tea powder, placing the powder into a 20mL headspace bottle, adding sodium chloride, adding 2-octanol internal standard solution, adding boiling water for soaking, and fully oscillating and uniformly mixing to perform headspace solid-phase microextraction. Preferably, in the first step, the weighing amount of the Jingyang Fu tea sample tea powder is 0.5-2g, the adding amount of sodium chloride is 0.5-2g, the using amount of the 2-octanol internal standard solution is 5-10 mu m, the concentration is 1mg/mL, and the using amount of boiling water is 3-10mL. Preferably, in the first step, the conditions of headspace solid-phase microextraction are that the aging temperature of an extraction head is 250-300 ℃, the aging time is 3-10min, the temperature of a heating box is 80-100 ℃, the heating time is 30-60min, the suction time is 30-60min, and the analysis is carried out at 240-250 ℃ for 3-10min. Preferably, in the first step, the GC parameters are an HP-5MS chromatographic column with the purity of 30m multiplied by 0.25mm multiplied by mu m, a carrier gas He with the purity of 99.999 percent and the flow rate of 1.8mL/min, a sample injection mode without split flow, wherein the temperature of a sample injection port is 240 ℃, the temperature is kept for 3-10min at an initial temperature of 40 ℃, the temperature is kept for 3-10min at 2 ℃ to 170 ℃ and the temperature is kept for 3-10min at 8 ℃ to 240 ℃; MS conditions are that the temperature of the electron ion source is 200 ℃, the ionization energy of EI is 70eV, the mass scanning range m/z is 30-500, and the temperature of the switching port is 220 ℃. Preferably, in the second step, qualitative analysis is performed by using NIST spectrum library search and retention index calculation, quantitative analysis is performed by using an internal standard method, the content of the volatile compounds is relatively quantified by using 2-octanol