Method for identifying Hanzhong white tea and Fujian white tea from volatile substances

Abstract

The invention relates to the technical field of tea analysis and detection, in particular to a method for identifying Hanzhong white tea and Fujian white tea from volatile substances. Comprising the following steps: collecting a white tea sample to be detected; collecting volatile substances in a headspace; detecting volatile substances of the white tea leaf sample to be detected by utilizing GC-IMS; and comparing and analyzing the detection result by using an endogenous marker, and identifying the variety of the white tea sample to be detected according to the comparison result. According to the method, on the basis of the GC-IMS technology, volatile component analysis is performed on a white tea sample to be detected, key volatile substances in the white tea sample to be detected are determined, the generality and difference of the key volatile substances are analyzed, and variety identification of the Han white tea and the Fujian white tea is performed on the white tea sample to be detected.

Description

Technical Field

[0001] The invention relates to the technical field of tea analysis and detection, and in particular to a method for identifying Hanzhong white tea and Fujian white tea from volatile substances. Background Art

[0002] Tea culture has a long history in China, dating back to the late Western Han Dynasty. It was already popular as a specialty beverage, and by the Wei, Jin, and Southern and Northern Dynasties, tea had become a luxury. White tea is a special delicacy among Chinese teas. As one of China's six major tea types, it is slightly fermented and boasts a fresh aroma, a mellow flavor, a long-lasting fragrance, and a unique flavor. Rich in tea polyphenols, tea polysaccharides, amino acids, caffeine, soluble sugars, and flavonoids, white tea possesses numerous health benefits, including proven anti-cancer, lipid-lowering, liver-protecting, anti-diabetic, neuroprotective, anti-inflammatory, antibacterial, antioxidant, and kidney-protective properties. The absolute content of volatile aroma components in tea is very low, generally accounting for only 0.01% to 0.05% of the dry matter content. Volatile compounds are a key factor in determining tea quality and flavor, playing a crucial role in tea flavor grading and consumer trends.

[0003] The main white tea producing areas are Fuding, Zhenghe, Songxi, and Jianyang counties. Fuding white tea, produced in the "Hometown of Chinese White Tea," is a prime example of white tea. Hanzhong City, located in southern Shaanxi Province, China, boasts a unique ecological environment between the Qinling and Bashan Mountains, making it a renowned producer of tribute tea and premium teas since ancient times. With a history of tea cultivation exceeding 4,000 years, Hanzhong primarily produces green tea, the most famous of which is "Hanzhong Xianhao." Since the successful trial production of white tea in 2018, Hanzhong white tea has gradually gained prominence.

[0004] Although both Fujian and Hanzhong white teas are white teas, they possess distinct flavors due to their different origins. Conventional methods for distinguishing the two types of white tea rely on sensory evaluation based on their appearance or internal qualities. This method requires a high level of tea evaluation expertise. Therefore, a more precise instrumental analytical method for distinguishing Fujian and Hanzhong white teas is needed.

[0005] At present, there is no method to accurately identify Fujian white tea and Hanzhong white tea using their volatile substances. Summary of the Invention

[0006] In order to solve the problem that there is no method in the existing technology to accurately identify Fujian white tea and Hanzhong white tea by using their volatile substances, the present invention uses gas chromatography-ion mobility spectrometry (GC-IMS) technology, which is at the forefront of research on food volatile substances in recent years, to study the differences in volatile substances between Hanzhong white tea and Fuding white tea after brewing, aiming to establish a method for identifying Hanzhong white tea and Fujian white tea based on their volatile substances.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] Gas chromatography-ion mobility spectrometry (GC-IMS) combines the outstanding separation characteristics of gas chromatography with the advantages of rapid response and high sensitivity of ion mobility spectrometry. It has the characteristics of fast response, high sensitivity, no need for pretreatment, simple operation, and low cost. It is a technology that effectively separates and sensitively detects volatile organic compounds. At present, there is no application of GC-IMS technology in the identification of Fujian white tea and Hanzhong white tea varieties. Based on this, the present invention provides a method for identifying Hanzhong white tea and Fujian white tea from volatile substances, comprising the following steps:

[0009] (1) Collect the white tea samples to be tested.

[0010] (2) Sample pretreatment: Take the white tea sample to be tested, grind it, and soak it in boiling water at 85-95℃ for 4-6 minutes.

[0011] (3) Place the soaked tea in a headspace bottle and inject the sample.

[0012] (4) The volatile substances in the white tea samples were detected using GC-IMS technology to obtain a GC-IMS result graph (fingerprint spectrum).

[0013] (5) Multivariate statistical analysis of the volatile substances and their relative concentration data measured by GC-IMS: The characteristic value area on the GC-IMS result graph was extracted using the comparative method.

[0014] (6) Principal component analysis (PCA) of the relative concentrations of the measured volatile substances: Using the Dynamic PCA plug-in, cluster analysis and similarity analysis are performed on the white tea samples to be tested, and the volatile substances of the white tea samples to be tested are identified by combining the fingerprints. The varieties of the white tea samples to be tested are then identified based on the identification results of the characteristic volatile substances. The characteristic volatile substances are the endogenous markers.

[0015] In the white tea sample to be tested, if the relative content of the endogenous marker is threshold A, the white tea sample to be tested is Fujian white tea; if the relative content of the endogenous marker is threshold B, the white tea sample to be tested is Hanzhong white tea.

[0016] The relative content refers to the content of the endogenous marker measured in the white tea sample to be tested relative to the content of all volatile substances measured in the white tea sample to be tested.

[0017] Threshold A is greater than threshold B. Threshold A is the average value of the endogenous marker content in Fujian white tea measured within 3 years of the detection time. Threshold B is the average value of the endogenous marker content in Hanzhong white tea measured within 3 years of the detection time.

[0018] Hanzhong white tea and Fujian white tea are white teas from different origins. Due to differences in origin, production process, tea tree varieties, etc., the characteristic volatile substances contained in them are different, but the differences are not particularly large. There is a certain difference in the content of endogenous markers in the two, but the difference is also within a relative range. The method for identifying Hanzhong white tea and Fujian white tea from volatile substances provided by the present invention uses endogenous markers with little difference in content to identify Hanzhong white tea and Fujian white tea in the white tea samples to be tested. Compared with the traditional method for distinguishing tea varieties, it has the characteristics of high sensitivity, simple operation, short analysis time and low detection cost.

[0019] In one embodiment of the present invention, by testing Hanzhong white tea and Fujian white tea produced in 2020-2023, the obtained threshold A range is 20.5-21.0%; the threshold B range is 19.8-20.2%.

[0020] The endogenous markers (characteristic substances) include acetic acid, (E)-heptenoic acid dimer, allyl isothiocyanate, cumene, (E)-heptenoic acid monomer, 2-acetyl-3-methylpyrazine, 6-methyl-3,5-heptadien-2-one, trans-2-hexenol, linalool oxide, ethyl acetoacetate, furfuryl methyl disulfide, limonene, and 2-acetylpyrrole.

[0021] The present invention provides a method for distinguishing Hanzhong white tea from Fujian white tea based on volatile compounds. This method utilizes the aforementioned endogenous markers to distinguish Hanzhong white tea from Fujian white tea in a sample of white tea. Compared to traditional methods for distinguishing tea varieties, this method has the advantages of high sensitivity, simple operation, short analysis time, and low detection cost.

[0022] Among them, (1) the conditions for collecting volatile substances in the headspace are as follows:

[0023] The headspace incubation temperature was set to 80°C, the incubation time was set to 10 min, the heating mode was oscillating heating, the headspace injection needle temperature was 85°C, the injection volume was 1 mL, and the splitless mode was used. The carrier gas was high-purity nitrogen, and the purge time was 0.5 min.

[0024] (2) GC conditions are as follows:

[0025] The chromatographic column is FS-SE-54-CB-0.5, column length: 15m, inner diameter: 0.53mm; the injection port temperature is 80℃; the injection mode is splitless mode; the chromatographic column temperature is 60℃; the running time is 20min; the carrier gas is nitrogen, the carrier gas flow rate is 2mL / min, maintained for 2min, and linearly increased to 150mL / min from 2 to 20min.

[0026] (3) IMS conditions are as follows:

[0027] The migration tube was set to 98 mm in length and at a temperature of 45°C. The ion source was Tritium in positive ion mode. The drift gas was high-purity nitrogen. The flow rate was 150 mL / min and the IMS detector temperature was 45°C.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] The present invention provides a method for identifying Hanzhong white tea and Fujian white tea from volatile substances. The differences in volatile components of Hanzhong white tea from three production areas and Fuding white tea from three production areas are studied by gas chromatography-ion mobility spectrometry, which can lay a foundation for further comparison of the differences in sensory aroma between Hanzhong white tea and Fuding white tea.

[0030] The technical solution of the present invention is as follows: First, the 3D spectrum is analyzed to find that the distribution of the volatile component points and the color depth of the points of Hanzhong white tea and Fuding white tea samples are relatively similar, and the similarity is relatively high. For further analysis, the two-dimensional spectrum of each sample is qualitatively analyzed, and 54 identical volatile substances are qualitatively identified in Hanzhong white tea and Fuding white tea. At the same time, the fingerprint spectrum is used to more intuitively and visually show that there is almost no difference in the content of 80% of the volatile substances in Hanzhong white tea and Fuding white tea, and about 20% of the volatile substances show characteristic differences in each sample of Fuding white tea and Hanzhong white tea, which can be used as distinguishing feature markers to distinguish samples. At the same time, by normalizing the peak volumes of each volatile substance and calculating the relative content of each volatile substance, it was found that the relative total contents of acids, aldehydes, ketones, esters, alcohols, ethers, furans, heterocyclics, olefins, and alkanes in Hanzhong white tea and Fuding white tea samples were very similar. The independent sample T test found that the P values ​​of the comparison results of each type of compound were all greater than 0.05, indicating that there was no significant difference in the relative contents of the ten types of compounds in Hanzhong white tea and Fuding white tea. Finally, the principal component analysis (PCA) method was used to analyze the similarity of volatile substances in Hanzhong white tea and Fuding white tea. It was found that the volatile components of white tea from the three production areas of Hanzhong and the white tea from Bailin Town and Panxi Town in Fuding were relatively similar, but the volatile components of white tea from Guanyang Town in Fuding City were quite different. In summary, it can be seen that the types and contents of volatile substances in Hanzhong white tea and Fuding white tea after brewing are very similar. The smell of white tea from the two origins is relatively close. From the perspective of volatile substances, the difference between Hanzhong white tea and Fuding white tea is relatively small.

[0031] The present invention establishes a method for identifying Hanzhong white tea and Fujian white tea from volatile substances. The method can use the content difference of endogenous markers in different tea samples to quickly identify Hanzhong white tea and Fujian white tea. Compared with traditional tea variety identification methods, the method has the characteristics of high sensitivity, simple operation, short analysis time and low detection cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a three-dimensional map of volatile substances in the Hanzhong white tea and Fuding white tea tea samples of the present invention.

[0033] Figure 2 This is the GC-IMS qualitative analysis of the volatile components of the Hanzhong white tea samples of the present invention.

[0034] Figure 3 This is the GC-IMS qualitative analysis of the volatile components of the Fuding white tea sample of the present invention.

[0035] Figure 4 This is the fingerprint of volatile substances of the Hanzhong white tea and Fuding white tea tea samples of the present invention.

[0036] Figure 5is the relative content of various odor compounds in the Hanzhong white tea and Fuding white tea samples of the present invention.

[0037] Figure 6 This is a similarity analysis of the volatile components of the Hanzhong white tea and Fuding white tea tea samples of the present invention. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to the accompanying drawings and specific examples, but they should not be construed as limiting the present invention. Unless otherwise specified, the technical means used in the following examples are conventional means well known to those skilled in the art, and the materials, reagents, etc. used in the following examples, unless otherwise specified, can be obtained from commercial sources.

[0039] The materials, instruments and equipment used in the following examples are as follows:

[0040] 1. Materials

[0041] Hanzhong white tea selected the tea tree variety Shaanxi Tea No. 1; fresh white tea samples were collected from three production areas in Xixiang County, Hanzhong, southern Shaanxi, with three samples taken from each production area, numbered for example: S1-1, S1-2, S1-3.

[0042] Fujian white tea selected the Fuding Dabaicha variety; fresh white tea samples were collected from three production areas in Fuding City, Fujian Province, with three samples taken from each production area, numbered for example: S4-1, S4-2, S4-3.

[0043] Detailed information of all the above tea samples is shown in Table 1.

[0044] Table 1 Sample information of Hanzhong white tea and Fuding white tea

[0045] Sample number Tea tree varieties Origin Collection time S1-1, S1-2, S-3 Shaanxi Tea No. 1 Tea Tree Liushu Town, Xixiang County, Hanzhong City July-September S2-1, S2-2, S3-3 Shaanxi Tea No. 1 Tea Tree Xiakou Town, Xixiang County, Hanzhong City July-September S3-1, S3-2, S3-3 Shaanxi Tea No. 1 Tea Tree Luo Town, Xixiang County, Hanzhong City July-September S4-1, S4-2, S4-3 Fuding big white tea tree Bailin Town, Fuding City May-August S5-1, S5-2, S5-3 Fuding big white tea tree Panxi Town, Fuding City May-August S6-1, S6-2, S6-3 Fuding big white tea tree Guanyang Town, Fuding City May-August

[0046] 2. Instruments and equipment

[0047] FlavourSpec 1H1-00053 GC-IMS; GAS, Germany.

[0048] CTC-PAL automatic sample injection device; CTCAnalyticsAG, Switzerland.

[0049] FS-SE-54-CB-115m ID, 0.53mm capillary column; Restek, USA.

[0050] BSA24S, 1 / 10,000 electronic balance; Sartorius, Germany.

[0051] Example 1

[0052] A method for identifying Hanzhong white tea and Fujian white tea from volatile substances comprises the following steps:

[0053] (1) Prepare the white tea samples to be tested according to the sample information collected in Table 1.

[0054] (2) Sample pretreatment: Grind the white tea sample to be tested, weigh about 5.00 g, and add 250 mL of 90°C boiling water to soak for 5 min.

[0055] (3) The tea soup after soaking was placed in a 20 mL headspace bottle, incubated at 500 rpm and 80 °C for 10 minutes, and then injected. 1 mL of the sample was injected, the injection needle temperature was 85 °C, and the carrier gas was high-purity N2 (purity ≥99.999%).

[0056] The gas chromatography conditions were as follows: column FS-SE-54-CB-0.515m ID, 0.53mm; column temperature, 60°C; run time, 20 min; carrier gas, high-purity N2, with a carrier gas flow rate starting at 2 mL / min and increasing linearly to 50 mL / min over 2 to 20 min.

[0057] Ion mobility spectrometry conditions: ion source: Tritium (6.5 keV), positive ion mode, drift tube length: 9.8 cm, drift gas flow rate: 150 mL / min; drift tube temperature: 45°C.

[0058] (3) Based on the above determination conditions, the volatile substances of the above white tea samples to be tested are detected using GC-IMS technology.

[0059] GC×IMS Library Search and LAV (Laboratory Analytical Viewer) software were used to acquire data and process spectra. Volatile flavor components were qualitatively analyzed using the built-in NIST and IMS databases. Dynamic PCA plug-in was used for cluster analysis of principal components of volatile compounds. Reporter and Gallery Plot plug-ins were used to quantitatively compare the differences in volatile compounds among the white tea samples. The volatile compound identification results were used to identify the white tea varieties tested.

[0060] Among the white tea samples to be tested, if the relative content of the endogenous marker is threshold A, the white tea sample to be tested is Fujian white tea; conversely, if the relative content of the endogenous marker is threshold B, the white tea sample to be tested is Hanzhong white tea.

[0061] The relative content refers to the content of the endogenous marker measured in the white tea sample to be tested relative to the content of all volatile substances measured in the white tea sample to be tested.

[0062] Threshold A is greater than threshold B. Threshold A is the average value of the endogenous marker content in Fujian white tea measured within 3 years of the detection time. Threshold B is the average value of the endogenous marker content in Hanzhong white tea measured within 3 years of the detection time.

[0063] Among them, the endogenous markers (characteristic substances) are acetic acid, (E)-heptenoic acid dimer, allyl isothiocyanate, cumene, (E)-heptenoic acid monomer, 2-acetyl-3-methylpyrazine, 6-methyl-3,5-heptadien-2-one, trans-2-hexenol, linalool oxide, ethyl acetoacetate, furfuryl methyl disulfide, limonene, and 2-acetylpyrrole.

[0064] The specific research on the detection of white tea samples using GC-IMS method is as follows;

[0065] 1. Obtaining 3D spectra of volatile compounds in Hanzhong white tea and Fuding white tea using GC-IMS technology

[0066] pass Using a GC-IMS instrument, the volatile components of three Hanzhong white tea samples (S1, S2, and S3) from Hanzhong and three Fujian white tea samples (S4, S5, and S6) from Fuding were detected and analyzed. Using the retention time (unit: s) of the gas chromatographic (GC), the migration time (unit: ms) of the ion mobility spectrometer (IMS), and the signal intensity (peak intensity) values ​​of various volatile components, the GC-IMS's built-in LAV (Laboratory Analytical Viewer) analysis software was used to obtain 3D spectra of volatile compounds from six white tea samples from Hanzhong and Fuding. The results are shown in Figure 2. Figure 1 .

[0067] The Y axis represents retention time, the X axis represents migration time, and the Z axis represents signal intensity. Figure 1The six 3D images from left to right in the figure represent white tea samples S1, S2, and S3 from three production areas in Hanzhong, and white tea samples S4, S5, and S6 from three production areas in Fuding. Each point in the figure represents a volatile substance, and the depth of the color indicates the content of the volatile substance. The darker the red color, the higher the content, and the lighter the white color, the lower the content. Based on the principle of ion mobility spectrometry, a volatile substance may produce 1, 2, or more points on the graph at the same retention time (representing monomers, dimers, or trimers of the volatile substance, respectively). When the concentration of the volatile substance is less than the concentration of the water and proton peaks, a monomer is formed. When the concentration of the volatile substance is greater than the concentration of hydrated protons, dimers begin to form. When the concentration of the volatile substance is much greater than the concentration of hydrated protons, polymers begin to form. In the black oval box in the 3D figure, the volatile substances of the Hanzhong white tea samples S1, S2, and S3 are almost identical in quantity, distribution position, and color depth, indicating that the volatile substances contained in the three white tea samples from Hanzhong are very similar. The volatile substances of the Fuding white tea samples S4, S5, and S6 in the black oval box are also generally consistent in quantity, distribution position, and color depth, indicating that the volatile substances contained in the three white tea samples from Fuding are consistent. Overall, comparing the Hanzhong white tea and Fuding white tea samples, it is found that the main volatile substances they contain are all distributed in the black oval circle, and the quantity and distribution position of the volatile substances are relatively similar. There are differences in color depth, but the changes are not large. This shows that the volatile substances of the Hanzhong white tea and Fuding white tea samples are relatively similar.

[0068] 2. Qualitative analysis of volatile substances in Hanzhong white tea and Fuding white tea samples by GC-IMS

[0069] GC-IMS uses C4-C9 normal ketones (2-butanone, 2-pentanone, 2-hexanone, 2-heptanone, 2-octanone and 2-nonanone) as external standards for calibration. By comparing the retention time and migration time of the external standard compounds, the retention index of the volatile substances is determined, and then matched with the ion mobility spectrum migration time database to achieve qualitative identification of the volatile substances. Figure 2 This is the qualitative analysis spectrum of volatile substances in Hanzhong white tea, taking S1 sample as an example. Figure 3 This is a qualitative analysis of the volatile compounds in Fuding white tea, using sample S4 as an example. Similar to the 3D plot, each numbered point represents a specific volatile compound. Darker red dots indicate higher levels of that compound, while lighter white dots indicate lower levels.

[0070] from Figure 2 and Figure 3It can be seen that the same types and quantities of 56 volatile substances were identified in the Hanzhong white tea and Fuding white tea samples, including furfuryl alcohol monomer, furfuryl alcohol dimer, (E)-2-heptenal monomer, and (E)-2-heptenal dimer, a total of 54 volatile substances, including 10 ketones, 8 esters, 6 aldehydes, 6 alcohols, 3 furans, 5 heterocyclic compounds, 7 olefin compounds, 4 alkane compounds, 3 acid compounds, and 2 ether compounds. It can be seen that the small molecular volatile substances contained in the Hanzhong white tea and Fuding white tea samples are mainly ketones, esters, aldehydes, alcohols, olefin compounds, and heterocyclic compounds. Specific information is shown in Table 2.

[0071] Table 2 List of qualitative volatile compounds in Hanzhong white tea and Fuding white tea samples

[0072]

[0073]

[0074]

[0075]

[0076]

[0077] Table 2 shows that the majority of volatile compounds detected by GC-IMS are small molecules with a molecular weight of less than 200. Published research using GC-MS for white tea analysis reveals that GC-IMS and GC-MS detect the same broad spectrum of volatile compounds, primarily aldehydes, esters, ketones, alcohols, and hydrocarbons. However, GC-IMS primarily detects volatile compounds with fewer than 10 carbon atoms, while GC-MS primarily detects compounds with greater than 10 carbon atoms. For example, hydrocarbons detected by GC-IMS are primarily small olefins and alkanes with fewer than 10 carbon atoms, while those detected by GC-MS are primarily alkanes and aromatic compounds with greater than 10 carbon atoms. Other compounds, such as ketones, aldehydes, and esters, exhibit similar patterns. This is primarily due to the headspace sampling method used by GC-IMS, which has a maximum incubation temperature of 80°C. Therefore, only some volatile compounds with lower boiling points in tea can be detected. GC-MS uses programmed temperature increase, with the maximum heating temperature reaching over 200°C, so it mostly detects compounds with larger molecular weight and relatively higher boiling points.

[0078] 3. Fingerprint analysis and relative content differences of volatile compounds in Hanzhong white tea and Fuding white tea samples obtained by GC-IMS technology

[0079] Figure 4 The fingerprints of volatile substances in the three origins of Hanzhong white tea samples S1, S2, and S3 and the three origins of Fuding white tea samples S5, S6, and S7 were obtained through GC-IMS analysis. Each column in the figure represents a volatile substance, and each row represents a sample. The darker the red color of the dot, the higher the content of the volatile substance, and the lighter the white color, the lower the content of the volatile substance. The red box A area in the fingerprint belongs to the aroma compounds shared by Hanzhong white tea and Fuding white tea. These compounds are almost consistent in the two white teas, indicating that the two varieties and origin factors have almost no effect on these aroma substances. It can also be seen that there are 43 kinds of these aroma compounds, accounting for 80% of the number of aroma compounds contained in white tea. The 13 aroma compounds to the right of the red frame are compared to the main aroma compounds in white tea. The content of these 13 compounds in the two varieties of white tea samples is relatively low. At the same time, when comparing the two varieties of white tea samples, it is found that the content of these 13 compounds in the Fuding white tea sample is slightly higher than that in the Hanzhong white tea sample. Secondly, it can also be seen that there are some significant differences in the content of these 13 compounds among the different white tea samples. The content of the six aroma compounds in the yellow frame B area is very high in the white tea sample (S6) from Guanyang Town, Fuding City, but is relatively low in other Fuding white tea and Hanzhong white tea samples. They are trans-2-hexenol, 6-methyl-3,5-heptadien-2-one, 2-acetyl-3-methylpyrazine, (E)-2-heptenal, cumene, and allyl isothiocyanate. They are characteristic markers of the white tea sample (S6) from Guanyang Town, Fuding City. The three aroma compounds in the green box, region C, are found at relatively high levels in white tea samples from Bailin Town and Panxi Town in Fuding City, and can serve as characteristic markers for white tea from these two producing areas. These compounds are 2-acetylpyrrole, limonene, and furfuryl methyl disulfide. The four aroma compounds in the brown box, region D, are found at relatively high levels in white tea from Xiakou Town, Xixiang County, Hanzhong City, but at relatively low levels in white tea samples from the other two producing areas in Hanzhong and from Fuding City. These compounds are ethyl acetoacetate, linalool oxide, trans-2-hexenol, and 6-methyl-3,5-heptadien-2-one. Overall, the aroma compounds in the Hanzhong and Fuding white tea samples are 80% identical, though some characteristic aroma compounds are also present. This suggests that the aroma of Hanzhong white tea is sensoryally similar to that of Fuding white tea.

[0080] 4. Analysis of the differences between Hanzhong white tea and Fuding white tea samples by the relative content of various compounds

[0081] exist Figure 5To clearly compare the differences in volatile compounds between Hanzhong and Fuding white tea samples, the relative contents of aroma compounds between samples were normalized based on the peak volumes of the detected volatile compounds. The aroma compounds (volatile compounds) in Hanzhong and Fuding white tea samples can be broadly categorized as acids, aldehydes, ketones, esters, alcohols, ethers, furans, heterocyclics, alkenes, and alkanes. In Hanzhong white tea samples S1, S2, and S3, aldehydes account for approximately 9.90% to 11.82%, alcohols account for approximately 7.59% to 11.74%, ketones account for approximately 25.10% to 27.90%, esters account for approximately 9.51% to 13.54%, acids account for approximately 3.75% to 7.10%, ethers account for approximately 1.95% to 4.03%, furans account for approximately 3.69% to 5.84%, hybrids account for 12.46% to 17.07%, alkenes account for approximately 6.37% to 9.64%, and alkanes account for 3.57% to 4.64%. In Fuding white tea S4, S5, and S6, aldehydes account for approximately 7.57% to 12.44%, alcohols account for approximately 7.10% to 10.56%, ketones account for approximately 25.32% to 26.71%, esters account for approximately 11.85% to 12.32%, acids account for approximately 4.17% to 8.20%, ethers account for approximately 0.83% to 4.63%, furans account for approximately 4.87% to 6.26%, hybrids account for 10.75% to 18.53%, alkenes account for approximately 9.96% to 13.09%, and alkanes account for 2.95% to 3.92%. By comparison, it was found that the contents of acids, aldehydes, ketones, esters, alcohols, ethers, furans, heterocyclic compounds, olefins and alkanes in Hanzhong white tea and Fuding white tea samples were relatively close. At the same time, the relative contents of ten types of compounds in the two white teas were analyzed for significant differences through independent sample T test. The analysis results are shown in Table 3.

[0082] Table 3 Independent Samples T Test (%)

[0083]

[0084]

[0085] The results in Table 3 show that the P values ​​for the comparison of acids, aldehydes, ketones, esters, alcohols, ethers, furans, heterocyclics, alkenes, and alkanes in Hanzhong white tea samples S1-S3 and Fuding white tea samples S4-S6 were all greater than 0.05, indicating that there was no significant difference in the relative content of the ten types of compounds between Hanzhong and Fuding white tea samples. In summary, it can be seen that there is no significant difference in the relative content of aroma compounds between Hanzhong and Fuding white tea, and the two white tea samples have a high degree of sensory similarity in their odor.

[0086] 5. Principal component similarity analysis of Hanzhong white tea and Fuding white tea samples

[0087] The similarity of the tea samples of Hanzhong white tea and Fuding white tea was studied by principal component analysis (PCA) method. Figure 6 It can be seen from the similarity analysis diagram that the tea samples S1, S2 and S3 of Hanzhong white tea and the tea samples S4 and S5 of Fuding white tea are gathered together in the lower right corner of the large ellipse, and the distances are relatively close, indicating that the similarity of the volatile substances of these tea samples is relatively high. The tea sample S6 of Fuding white tea is located in the upper right corner of the ellipse and is far away from the samples in the large ellipse, indicating that the similarity of the volatile components of the tea sample S6 of Fuding white tea with the tea samples S1, S2, S3 of Hanzhong white tea and the tea samples S4 and S5 of Fuding white tea is not high. In summary, it can be seen that the volatile components of the tea samples of Hanzhong white tea of three origins are relatively close to those of Fuding Bailintown white tea and Pankxi Town white tea, and are quite different from those of Fuding Guanyang Town white tea.

[0088] From the above experimental results, the method for identifying Hanzhong white tea and Fujian white tea from volatile substances provided by the present application uses GC-IMS method to detect and analyze the volatile substances of the tea samples S1, S2 and S3 of Hanzhong white tea of three origins in Hanzhong and the tea samples S4, S5 and S6 of Fujian white tea of three origins in Fuding. The results are as follows: the relative content of the endogenous marker in the tea samples S1, S2 and S3 of Hanzhong white tea of three origins in Hanzhong is 20.8%, and the content of the endogenous marker in the tea samples S4, S5 and S6 of Fujian white tea of three origins in Fuding is 20.0%. The relative content of the endogenous marker in the tea samples S1, S2 and S3 of Hanzhong white tea of three origins in Hanzhong is slightly lower than that of the endogenous marker in the tea samples S4, S5 and S6 of Fujian white tea of three origins in Fuding.

[0089] At the same time, the method for identifying Hanzhong white tea and Fujian white tea from volatile substances provided in Example 1 is used to identify white tea varieties.

[0090] Among them, the white tea tea samples to be tested are selected from Hanzhong white tea with Hanzhong City as the origin, Fujian white tea (Fuding white tea) with Fuding City as the origin, Fujian white tea (Zhenghe white tea) with Zhenghe as the origin, Fujian white tea (Jianyang white tea) with Jianyang City as the origin and Yunnan white tea (Jinggu white tea) with Jinggu as the origin.

[0091] The above materials are randomly selected for detection, and are numbered according to their detection order, and are respectively recorded as white tea tea sample 1, white tea tea sample 2, white tea tea sample 3, white tea tea sample 4 and white tea tea sample 5. Each material is distinguished and marked before detection, that is, after the detection order is randomly selected, the actual variety of each white tea tea sample to be tested is known.

[0092] By testing Hanzhong white tea and Fujian white tea produced between 2020 and 2023, the present invention obtains that the range of threshold A is 20.5-21.0%; the range of threshold B is 19.8-20.2%.

[0093] The test results are as follows:

[0094] The relative content of the endogenous marker in the white tea sample 1 to be tested is 20.6%. According to the identification method provided by the present invention, the tea variety of the white tea sample 1 to be tested is Fujian white tea, and the actual variety is Fuding white tea. The results of the two are consistent.

[0095] The relative content of the endogenous marker in the white tea sample 2 to be tested is 19.9%. According to the method provided by the present invention, the tea variety of the white tea sample 1 to be tested is Hanzhong white tea, and the actual variety is Hanzhong white tea. The results of the two are consistent.

[0096] The relative content of the endogenous marker in the white tea sample 3 to be tested is 21.0%. According to the identification method provided by the present invention, the tea variety of the white tea sample 1 to be tested is Fujian white tea, and the actual variety is Jinggu white tea. The results of the two are consistent.

[0097] The relative content of the endogenous marker in the white tea sample 4 to be tested is 20.5%. According to the identification method provided by the present invention, the tea variety of the white tea sample 1 to be tested is Fujian white tea, and the actual variety is Jianyang white tea. The results of the two are consistent.

[0098] The relative content of the endogenous marker in the white tea sample 5 to be tested is 20.7%. According to the identification method provided by the present invention, the tea variety of the white tea sample 1 to be tested is Fujian white tea, and the actual variety is Zhenghe white tea. The results of the two are consistent.

[0099] This application also uses the method disclosed in "Identification of the Origin of Fujian White Tea Based on GC-IMS Technology" by Luo Yuqin et al. to identify the above 5 white tea samples with different origins. The results are: only 2 of the 5 white tea samples have the same origin as the actual origin.

[0100] The above results demonstrate that the method provided by the present invention for distinguishing Hanzhong white tea from Fujian white tea based on volatile compounds utilizes the aforementioned endogenous markers to identify the origins of Hanzhong white tea and Fujian white tea in the white tea samples tested. Compared with traditional methods for distinguishing tea varieties, this method has the advantages of high sensitivity, simple operation, short analysis time, and low detection cost.

[0101] While the preferred embodiments of the application have been described, additional variations and modifications can be made to these embodiments by those skilled in the art once they have the benefit of the present disclosure without departing from the spirit and scope of the application. Accordingly, it is intended that the appended claims include all such modifications and variations as fall within the scope of the present application.

[0102] It is apparent that those skilled in the art can make various changes and modifications to the application without departing from the spirit and scope of the application. It is therefore intended that the present application cover all such changes and modifications that are within its scope.

Claims

1. A method for distinguishing Hanzhong white tea and Fujian white tea from volatile substances, characterized in that: The steps include: Collect the white tea samples to be tested; collect volatile substances in the headspace; The volatile substances in the white tea samples were detected using GC-IMS technology; Using endogenous markers, the test results are compared and analyzed, and the variety of the white tea sample to be tested is identified based on the comparison results; The endogenous markers include acetic acid, (E)-heptenoic acid dimer, allyl isothiocyanate, cumene, (E)-heptenoic acid monomer, 2-acetyl-3-methylpyrazine, 6-methyl-3,5-heptadien-2-one, trans-2-hexenol, linalool oxide, ethyl acetoacetate, furfuryl methyl disulfide, limonene, and 2-acetylpyrrole.

2. The method according to claim 1, characterized in that The GC-IMS technique is used to obtain the fingerprint of the volatile substances of the white tea samples to be tested. By comparing the differences in the content of volatile substances, the tea varieties and origins can be identified.

3. The method according to claim 2, characterized in that Selecting characteristic volatile substances in the detected spectrum to prepare a fingerprint of the white tea sample to be tested, obtaining the relative content of the volatile substances, and then performing principal component analysis on the samples to determine the characteristic volatile substances in the white tea sample to be tested, so as to distinguish different tea varieties; The characteristic volatile substance is the endogenous marker; If the content of the endogenous marker in the white tea sample to be tested is threshold A, it is Fujian white tea; if the content of the endogenous marker in the white tea sample to be tested is threshold B, it is Hanzhong white tea; wherein, threshold A is greater than threshold B.

4. The method according to claim 3, characterized in that The threshold value A is the average value of the content of the endogenous marker in Fujian white tea measured within 2 to 5 years of the detection time; the threshold value B is the average value of the content of the endogenous marker in Hanzhong white tea measured within 2 to 5 years of the detection time.

5. The method according to claim 1, wherein The detection conditions include GC conditions and IMS conditions.

6. The method according to claim 5, characterized in that The GC conditions are as follows: The chromatographic column is FS-SE-54-CB-0.5, column length: 13~17m, inner diameter: 0.52~0.54mm; the injection port temperature is 78~82℃; the injection mode is splitless mode; the chromatographic column temperature is 58~62℃; the running time is 18~22min; the carrier gas is nitrogen, the carrier gas flow rate is 1.8~2.2mL / min, maintained for 1.5~2.5min, and linearly increased to 148~152mL / min in 2~20min.

7. The method according to claim 3, characterized in that The IMS conditions are as follows: The migration tube was set to 96-100 mm in length and 40-50°C; the ion source was Tritium, in positive ion mode; the drift gas was high-purity nitrogen; the flow rate was 145-155 mL / min, and the IMS detector temperature was 40-50°C.

8. The method according to claim 7, characterized in that The IMS conditions included a drift tube length of 98 mm, a drift gas flow rate of 150 mL / min, and a drift tube temperature of 45°C.

9. The method according to claim 1, characterized in that The conditions for headspace sampling of volatile substances were as follows: The headspace incubation temperature was set to 78-82°C, the incubation time was set to 8-12 min, the heating mode was oscillating heating, the headspace injection needle temperature was 80-90°C, the injection volume was 0.8-1.2 mL, splitless mode, the carrier gas was high-purity nitrogen, and the purge time was 0.4-0.6 min.

10. The method according to claim 1, characterized in that The white tea sample to be tested was crushed, soaked in 85-95°C hot water, and volatile substances were collected from the headspace of the soaked tea soup.

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