CN113740458A - Method for identifying picking season of shoumei white tea leaves - Google Patents

Abstract

The invention discloses a method for identifying picking seasons of the tea leaves of shoume white tea, which comprises the steps of selecting the white tea leaves in different seasons of the same tea garden, preparing the shoume white tea by the same process, measuring the content of 32 characteristic metabolic components in the shoume white tea, establishing a sample matrix by taking the content of the obtained characteristic metabolic components as an index, applying a principal component analysis method, selecting a chemical component with the maximum weight in the principal component as a distinguishing factor, and determining the picking seasons of the white tea leaves by taking the distinguishing factor as an independent variable. The method can realize effective identification of the shoumei white tea in different picking seasons, and provides a new method and a new idea for quickly, comprehensively and accurately judging the taste and quality of the tea.

Description

Method for identifying picking season of shoumei white tea leaves

Technical Field

The invention belongs to the field of analytical chemistry, and particularly relates to a method for identifying the picking season of the tea leaves of shoumei white tea.

Background

The white tea is a kind of light fermented tea in six kinds of tea in China, and is processed without stir-frying and only by two procedures of withering and baking, during the process, the moisture of fresh leaves is dissipated, the cell membrane permeability is changed, chemical reactions such as chlorophyll degradation, polyphenol substance partial oxidation, protein hydrolysis, starch hydrolysis, amino acid oxidation and desinsection are promoted to occur, and the typical quality characteristics of white and dark green dry tea, apricot yellow and bright soup color, and sweet and refreshing taste are formed. Meanwhile, the quality components of the white tea formed by the characteristic process also have biological effects of oxidation resistance, antibiosis, inflammation diminishing and the like, and are highly favored by consumers. With the improvement of consumption ability and continuous improvement of quality and life requirements of people, the consumption concept is changed from emphasizing the appearance of tea leaves to emphasizing the endoplasmic manifestations of tea leaf fragrance, taste and the like. The taste quality characteristics serve as an important aspect of the inner quality judgment, the weight of the inner quality characteristics accounts for 30% -35% of the five-factor percentage judgment, and the inner quality characteristics are core factors of the tea quality judgment.

In the world of tea, the quality of tea is closely related to weather and climate, the climate changes all the year round, and the produced tea is different in nature and is divided into spring tea, summer tea, autumn tea and winter tea. When the white tea is purchased, whether the white tea is worthy of purchase or not is judged through some information of the white tea, and one piece of information is the picking season of the tea leaves. Tea plucking time varies depending on the region, tea plant species and tea making species. The spring tea of white tea can be mined before and after the april is clear, and the bud and leaf germination meets the picking standard, and the yield accounts for about 50% of the total annual yield in the last ten days of May. The yield is about 25% when the plant is collected from June to July in summer. Autumn tea is collected after July. From the quality aspect, the spring tea is the best, the leaf quality is soft, the bud center is fat and strong, the antler hair is white, the tea body is heavy, the soup is thick and tasty, and therefore the proportion of the high-grade tea in the spring tea is high. Summer tea has a small bud center, hard leaves, light and floating tea body, and thin or slightly astringent soup. Autumn tea quality is between spring and summer tea. The shoumei is one of white tea, is mainly prepared by taking one bud and two leaves of tender tips of tea trees as raw materials, withering and drying; the tea has the characteristics of abundant appearance, thick tea stalk, multiple branches of bud leaves, small bud heads and prominent flower fragrance, and is the most characteristic of shoume. The longevity eyebrows can be divided into spring longevity eyebrows, summer longevity eyebrows and autumn longevity eyebrows according to different picking time, and are characterized in that the spring longevity eyebrows are higher in freshness and more sufficient in flower fragrance, because tea trees grow faster in spring, new leaves are tender and more fresh; autumn shoume is not as floral as spring shoume, but because of recuperative growth in the whole summer, the leaf is bigger, the thickness is thicker, and the pectin content is more. Therefore, the prices of the white tea shoumei in different seasons on the market are greatly different. The method takes the white tea as a research object, analyzes the flavor characteristic attributes of the white tea, and analyzes by utilizing the attributes of 32 characteristic metabolic components in the white tea so as to provide a new method and a new thought for quickly, comprehensively and accurately judging the flavor quality of the tea.

Disclosure of Invention

The invention aims to provide a method for identifying the picking season of the tea leaves of shoumei white tea.

In order to achieve the purpose, the invention adopts the following technical scheme:

a method for identifying the picking season of the Yangmei white tea leaves comprises the steps of selecting the white tea leaves in different seasons of the same tea garden, preparing the Yangmei white tea leaves by the same process, measuring the content of 32 characteristic metabolic components, establishing a sample matrix by taking the content of the characteristic metabolic components as an index, applying a principal component analysis method, selecting a chemical component with the highest weight in the principal component as a distinguishing factor, and determining the picking season of the white tea leaves by taking the distinguishing factor as an independent variable.

The preparation process of the shoumei white tea comprises the following steps:

1) picking: picking tea leaves with two leaves in one bud and 1.5-2.0 cm in bud length, finely picking and removing impurities to achieve the purposes of tenderness, uniformity and cleanness;

2) frying: spreading the picked tea leaves on a bamboo plaque for 3 hours, and then frying in a pot at 120-140 ℃ until the leaves are soft and dark;

3) rubbing to show hair: in a pot with the temperature of 75 ℃, by adopting the methods of shaking, sorting, rubbing and grabbing, firstly sorting straight tea strips, then folding and rubbing the tea strips by using double palms until the tea strips are round and slightly flat, fuzz appears, and when the dryness reaches about seven percent, reducing the temperature of the pot to 50-60 ℃;

4) hui pan: parching at slow speed until the color of the tea leaves is revealed, heating the pot to about 10 deg.C to evaporate water, smoothing tea strips, fixing shape, taking out when the tea leaves give off lasting fragrance and twist tea to obtain powder and the water content is below 6%, and spreading for cooling and storing.

The 32 characteristic metabolic components are epigallocatechin gallate (EGCG), Caffeine (Caffeine), quercetin 3-O-glucosylrutin, epicatechin gallate (ECG), Rutin (Rutin), Theanine Isomer 2 (Theanine Isomer 2), kaempferol-3-O-galactosylrutin (kaempferol-3-O-galactosylrutin), Apigenin 6-C-glucoside 8-C-arabinoside (Apigenin 6-C-glucosyl 8-C-arabinoside), epigallocatechin-epicatechin gallate dimer (EGC-ECG dimer), theobromine (theobromine), Theanine Isomer 1 (Theanine Isomer 1), kaempferol-3-O-glucosylrutin (kaempferol-3-O-glucosylrutin), Quercetin 3-O-galactosylrutinoside (quercetin 3-O-galactosylglucoside), epicatechin-epigallocatechin gallate dimer (EC-EGCG dimer), isovitexin (isovitexin), gallol (theogallin), tea saponin F (theasinsin F), camel B (camellianin B), vitexin rhamnoside (vitexin rhamnoside), Gallocatechin (GC), kaempferol-3-O-glucoside (epamopferol-3-O-glucoside), vitexin (vitexin), 3-gallic acid 8-ascorbyl glyceride (8-C-ascorbyl epigastrin 3-gallate), catechin (C), ECG glycoside A (camellliquercetiside A, Apigenin 4 '-O-O-glucoside (Apigenin 4' -O-O-catechin), and catechin (O-3-methyl gallate) (3) " Me), epigallocatechin-Epicatechin dimer ((E) GC- (E) C dimer), Epicatechin ((epi) afzelechin), (+) -Epicatechin ((+) -Epicatechin).

The content of 32 characteristic metabolic components in the prepared shoumei white tea is determined by adopting an ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry system, and the specific determination steps are as follows:

1) sample extraction: taking 0.1g SHOUMEI white tea sample, adding 1mL of 80wt% methanol solution, stirring and mixing at room temperature for 10min, centrifuging at 9000rpm at 4 deg.C for 15min, and collecting supernatant;

2) preparation of sample solution: repeatedly extracting the residue obtained after centrifugation for 2 times according to the conditions in the step 1), merging the obtained supernatant into a volumetric flask, and fixing the volume to 5mL by using 80wt% methanol solution;

3) and (3) detection of the sample: filtering the obtained sample solution by a 0.45-micron microporous filter membrane, and detecting by using UPLC/TOF-MS;

wherein, the detection conditions of the UPLC are as follows: BEH C18 chromatography column, specification: 100 mm × 2.1 mm, 1.7 μm; the column temperature was 40 ℃; gradient elution is carried out by taking an aqueous solution containing 0.1vol% of formic acid as a mobile phase A and an acetonitrile solution containing 0.1vol% of formic acid as a mobile phase B, wherein the flow rate of the mobile phase is 0.3 mL/min, and the elution procedure comprises that the volume ratio of the mobile phase A is reduced from 100% to 95% in 0-2 min, the volume ratio of the mobile phase A is reduced from 95% to 50% in 2-13 min, the volume ratio of the mobile phase A is reduced from 50% to 0% in 13-14 min, and the volume ratio of the mobile phase A is increased from 0% to 100% in 14-17 min;

analysis conditions for TOF-MS were: an ion source: ESI; detection mode: ESI^-(ii) a Capillary voltage: 1.5 kV; series voltage: 10-40 eV; the scanning range is 50-1200 Da; the ion source temperature is 120 ℃; the desolvation temperature is 500 ℃; the desolvation flow rate is 800L/h; the taper hole voltage is 40V.

The invention has the following remarkable advantages: the method can realize effective identification of the shoumei white tea in different picking seasons, and can provide a new method and a new idea for quickly, comprehensively and accurately judging the taste and quality of the tea.

Drawings

FIG. 1 is a principal component analysis chart.

Fig. 2 is a graph of cluster analysis.

Detailed Description

In order to make the present invention more comprehensible, the technical solutions of the present invention are further described below with reference to specific embodiments, but the present invention is not limited thereto.

Examples

1) In a certain tea garden in the administrative and county, 6 batches of white tea leaves (1 in spring, 2 in summer, 2 in autumn and 1 in winter) picked in four seasons (4-5 last ten months), 6 batches of white tea leaves picked in summer (6 middle and last ten years-8 last ten months), 6 batches of white tea leaves picked in autumn (9 middle and last ten months-11 months) and 6 batches of winter tea leaves picked in 11 middle and last ten months) are selected and sequentially marked as A-F (each sample is provided with 3 biological repetitions and respectively marked as 1, 2 and 3), and the picking time is shown in Table 1.

TABLE 1 picking time of different batches of white tea leaves

2) Respectively preparing the selected tea leaves into the shoumei white tea; the preparation process comprises the following steps:

a) picking: picking tea leaves with two leaves in one bud and 1.5-2.0 cm in bud length, finely picking and removing impurities to achieve the purposes of tenderness, uniformity and cleanness;

b) frying: spreading the picked tea leaves on a bamboo plaque for 3 hours, and then frying in a pot at 120-140 ℃ until the leaves are soft and dark;

c) rubbing to show hair: in a pot with the temperature of 75 ℃, by adopting the methods of shaking, sorting, rubbing and grabbing, firstly sorting straight tea strips, then folding and rubbing the tea strips by using double palms until the tea strips are round and slightly flat, fuzz appears, and when the dryness reaches about seven percent, reducing the temperature of the pot to 50-60 ℃;

d) hui pan: parching at slow speed until the color of the tea leaves is revealed, heating the pot to about 10 deg.C to evaporate water, smoothing tea strips, fixing shape, taking out when the tea leaves give off lasting fragrance and twist tea to obtain powder and the water content is below 6%, and spreading for cooling and storing.

3) Measuring contents of 32 characteristic metabolic components (EGCG, Caffeine, quercetin 3-O-glucosyl rutinoside, ECG, Rutin, Theanine Isomer 2, kaempferol-3-O-galactosyl rutinoside, Apigenin 6-C-glucosyl 8-C-arabinoside, EGC-ECG dimer, theobromine, Theanine Isomer 1, kaempferol-3-O-glucosyl rutinoside, quercetin 3-O-galactosyl rutinoside, EC-EGdimer, isovitexin, theogallin, theasinensin F, camellianin B, vitexin, GC, kaempferol-3-O-glucosyl rutinoside, EC-EGdimer, isovitexin, theogallin, theasinensin F, camelin B, vitexin B, virosine, GC, kaempferol-3-O-glucosyl rutinoside, ECG-3-O-agarose, 35oligosaccharide C-4-acetyl-E, or E-4-acetyl-D-glucoside C-3-O-acetyl-D-E, the specific determination steps are as follows:

i) sample extraction: taking 0.1g SHOUMEI white tea sample, adding 1mL of 80wt% methanol solution, stirring and mixing at room temperature for 10min, centrifuging at 9000rpm at 4 deg.C for 15min, and collecting supernatant;

ii) preparation of sample solution: repeatedly extracting the residue obtained after centrifugation for 2 times according to the conditions in the step i), combining the obtained supernatant into a volumetric flask, and fixing the volume to 5mL by using 80wt% methanol solution;

iii) detection of the sample: filtering the obtained sample solution by a 0.45-micron microporous filter membrane, and detecting by using UPLC/TOF-MS;

wherein, the detection conditions of the UPLC are as follows: a chromatographic column: BEH C18 (100 mm. times.2.1 mm, 1.7 μm); the column temperature was 40 ℃; gradient elution is carried out by taking an aqueous solution containing 0.1vol% of formic acid as a mobile phase A and an acetonitrile solution containing 0.1vol% of formic acid as a mobile phase B, wherein the flow rate of the mobile phase is 0.3 mL/min, and the elution procedure comprises that the volume ratio of the mobile phase A is reduced from 100% to 95% in 0-2 min, the volume ratio of the mobile phase A is reduced from 95% to 50% in 2-13 min, the volume ratio of the mobile phase A is reduced from 50% to 0% in 13-14 min, and the volume ratio of the mobile phase A is increased from 0% to 100% in 14-17 min;

analysis conditions for TOF-MS were: an ion source: ESI; detection mode: ESI^-(ii) a Capillary voltage: 1.5 kV; series voltage: 10-40 eV; the scanning range is 50-1200 Da; the ion source temperature is 120 ℃; the desolvation temperature is 500 ℃; the desolvation flow rate is 800L/h; the taper hole voltage is 40V.

The results are shown in Table 2.

TABLE 2 characteristic metabolic components and their contents (μ g/g, DW) in different batches of SHOUMei white tea

4) After the absolute peak areas of the 32 common peaks of the 6 batches of samples were normalized, the main component analysis was performed by using SPSS 24.0 software, and the eigenvalue and variance contribution rates were calculated, the results of which are shown in table 3. As can be seen from Table 3, 3 principal component factors were obtained, and their characteristic values were 34.464%, 28.004%, and 13.006%, respectively, which suggests that the principal component factors 1, 2, and 3 can be used as evaluation indexes of shoumei white tea, and are suitable for principal component analysis. Therefore, 6 shoumei samples were evaluated by using the main component factors 1, 2, and 3 as indices, and the results are shown in Table 4.

TABLE 3 principal Components eigenvalues

TABLE 4 principal Components eigenvalues

5) The value obtained by dividing the peak area of each common peak by the sample weighing is used as the original data, the cluster analysis is carried out on 6 batches of shoume samples by adopting SPSS 24.0 software and combining the interclass connection method with the squared Euclidean distance, and the result is shown in figure 2. As can be seen from FIG. 2, the 6 batches of Youmei samples can be grouped into four types, spring tea A1-A3, summer tea B1-C3, autumn tea D1-E3 and winter tea F1-3. The results show that the quality of the summer tea sample and the autumn tea sample in the shoumei sample in different months is similar, the quality difference between the summer tea sample and the autumn tea sample and the spring tea sample and the winter tea sample is large, and the tea leaves in the spring, the autumn, the summer and the winter can be distinguished through a matrix formed by the composition and the content of the 32 compounds, main component analysis and cluster analysis.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.

Claims (4)

1. A method for identifying the picking season of the tea leaves of shoumei white tea is characterized in that: selecting white tea leaves in different seasons of the same tea garden, preparing the shoumei white tea by the same process, measuring the content of 32 characteristic metabolic components, establishing a sample matrix by taking the content of the obtained characteristic metabolic components as an index, applying a principal component analysis method, selecting a chemical component with the maximum weight in the principal component as a distinguishing factor, and determining the picking season of the white tea leaves by taking the distinguishing factor as an independent variable.

2. The method of identifying the plucking season of shoumei white tea leaves as set forth in claim 1, wherein: the preparation process of the shoumei white tea comprises the following steps:

1) picking: picking tea leaves with two leaves and one bud and 1.5-2.0 cm long, finely picking and removing impurities;

2) frying: spreading the picked tea leaves on a bamboo plaque for 3 hours, and then frying at 120-140 ℃ until the leaves are soft and dark in color;

3) rubbing to show hair: in a pot with the temperature of 75 ℃, the method of shaking, sorting, rubbing and grabbing is adopted, tea strips are sorted firstly, then the tea strips are folded and rubbed by the two palms until the tea strips are round and slightly flat, fuzz appears, and when the dryness reaches seven percent, the temperature of the pot is reduced to 50-60 ℃;

4) hui pan: parching with slow speed until the color of cornu Cervi Pantotrichum is revealed, heating the pot to 10 deg.C, stirring tea leaves with lasting fragrance to obtain powder, taking out when the water content is below 6%, and spreading for cooling.

3. The method of identifying the plucking season of shoumei white tea leaves as set forth in claim 1, wherein: the 32 characteristic metabolic components are EGCG, caffeine, quercetin 3-O-glucosyl rutin glycoside, ECG, rutin, theanine isomer 2, kaempferol-3-O-galactosyl rutin glycoside, apigenin 6-C-glucoside 8-C-arabinoside, EGC-ECG dimer, theobromine, theanine isomer 1, kaempferol-3-O-glucosyl rutin glycoside, quercetin 3-O-galactosyl rutin glycoside, EC-EGCG dimer, isovitexin, gallicin, theasaponin F, camelina B, vitexin rhamnoside, GC, kaempferol-3-O-glucoside, vitexin, 3-gallic acid 8-ascorbyl glyceride, C, camellin A, apigenin 4'-O-rhamnoside, apigenin B, rutin B, catechin, C-O-rhamnoside, catechin A, and D, wherein the characteristic metabolic components are EGCG, caffeine, quercetin isomer 2, kaempferol-3-O-galactosyl rutin glycoside, apigenin A, apigenin 4' -O-rhamnoside, and D, epigallocatechin-3-O- (3-O-methyl) gallate, (E) GC- (E) C dimer, epicatechin, and (+) -epicatechin.

4. The method of identifying the plucking season of shoumei white tea leaves as set forth in claim 1, wherein: the content of 32 characteristic metabolic components in the prepared shoumei white tea is determined by adopting an ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry system, and the specific determination steps are as follows:

1) sample extraction: taking 0.1g SHOUMEI white tea sample, adding 1mL of 80wt% methanol solution, stirring and mixing at room temperature for 10min, centrifuging at 9000rpm at 4 deg.C for 15min, and collecting supernatant;

2) preparation of sample solution: repeatedly extracting the residue obtained after centrifugation for 2 times according to the conditions in the step 1), merging the obtained supernatant into a volumetric flask, and fixing the volume to 5mL by using 80wt% methanol solution;

3) and (3) detection of the sample: filtering the obtained sample solution by a 0.45-micron microporous filter membrane, and detecting by using UPLC/TOF-MS;

wherein, the detection conditions of the UPLC are as follows: BEH C18 chromatography column, specification: 100 mm × 2.1 mm, 1.7 μm; the column temperature was 40 ℃; gradient elution is carried out by taking an aqueous solution containing 0.1vol% of formic acid as a mobile phase A and an acetonitrile solution containing 0.1vol% of formic acid as a mobile phase B, wherein the flow rate of the mobile phase is 0.3 mL/min, and the elution procedure comprises that the volume ratio of the mobile phase A is reduced from 100% to 95% in 0-2 min, the volume ratio of the mobile phase A is reduced from 95% to 50% in 2-13 min, the volume ratio of the mobile phase A is reduced from 50% to 0% in 13-14 min, and the volume ratio of the mobile phase A is increased from 0% to 100% in 14-17 min;

analysis conditions for TOF-MS were: an ion source: ESI; detection mode: ESI^-(ii) a Capillary voltage: 1.5 kV; series voltage: 10-40 eV; the scanning range is 50-1200 Da; the ion source temperature is 120 ℃; the desolvation temperature is 500 ℃; the desolvation flow rate is 800L/h; the taper hole voltage is 40V.

Images