Method for determining the end point of Wuyi rock tea making green

Abstract

The present application belongs to the field of intelligent control and rapid detection technology of tea processing quality, and particularly relates to a method for determining the end point of Wuyi rock tea making green. The method comprises the following steps: detecting the aroma emitted during the making green process by using a portable gas chromatograph-mass spectrometer, and determining beta-myrcene and cis-3-hexenyl acetate in the aroma; when the area percentage of cis-3-hexenyl acetate is less than or equal to 15% or the ratio of beta-myrcene to cis-3-hexenyl acetate is greater than 3.0:1 for the first time in two consecutive detections, the end point of making green is determined. The method does not require complex pretreatment, and the single detection time is short. The area percentage of aroma substances beta-myrcene and cis-3-hexenyl acetate in tea green can be determined in real time. The determination method can significantly reduce the misjudgment rate and improve the stability and consistency of tea quality.

Description

Technical Field

[0001] This invention belongs to the field of intelligent control and rapid detection technology for tea processing quality, specifically relating to a method for determining the endpoint of the processing of Wuyi rock tea. Background Technology

[0002] The core process of Wuyi rock tea processing, known as "making green," involves alternating between shaking and air-drying. This process directly determines key qualities of the finished tea, such as its floral and fruity aromas, rocky character, and grassy notes. Traditionally, the processing master relied on their sensory perception to determine the degree of aroma component transformation and thus the final stage of the processing.

[0003] Current technologies also involve pre-processing with different methods to extract and concentrate the withered samples, and then using a benchtop gas chromatography-mass spectrometry (GC-MS) instrument in the laboratory to analyze the differences in aroma components and content at different withering levels. For example, Wang Zan et al.: Research progress on the influence of withering process on characteristic aroma components of oolong tea.

[0004] However, existing technologies do not publicly disclose the use of benchtop GC-MS to detect the endpoint of the withering process. Even if benchtop GC-MS is used, the following problems exist: 1. Benchtop GC-MS is bulky and fixed, requiring tea samples to be taken back to the laboratory for testing. This limits the testing scenario and makes it impossible to apply in real time on-site. It can only be used for post-processing verification of the maturity of the withering process under laboratory conditions. The test results lag behind the on-site withering process. The withering process is irreversible, and the test results cannot guide production control in real time, resulting in poor practicality. 2. Benchtop GC-MS testing requires complex pretreatment such as solvent extraction, concentration, and purification. A single test takes more than 2 hours. The pretreatment is cumbersome, the testing efficiency is low, and it cannot match the rapid cycle of withering, shaking, and drying. 3. It only samples and tests at a single point at the end of the withering process, without monitoring the dynamic changes of aroma substances. It cannot predict the maturity trend of the withering process, lacks dynamic process monitoring, has a high risk of misjudgment, and is prone to under- or over-withering. Summary of the Invention

[0005] The technical problem to be solved by this invention is: how to conveniently and accurately determine the endpoint of the greening process.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a method for determining the endpoint of the processing of Wuyi rock tea, comprising the following steps: using a portable gas chromatography-mass spectrometry instrument to detect the aroma emitted during the processing, and measuring β-ocimene and cis-3-hexenyl acetate in the aroma; When the area percentage of cis-3-hexenyl acetate is ≤15% or the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1 for the first two consecutive monitoring sessions, it is determined as the greening endpoint.

[0007] The beneficial effects of this invention are as follows: At the processing site of Wuyi rock tea, this invention uses a portable gas chromatography-mass spectrometry (GC-MS) instrument to collect and rapidly analyze the aroma emitted during the withering process. No complex pretreatment is required, and each detection session is short. It can measure the area percentage of aroma compounds β-ocimene and cis-3-hexen-1-ol acetate (Z-) in the tea leaves in real time. When the area percentage of cis-3-hexen-1-ol is ≤15% for the first two consecutive monitoring sessions, or when the β-ocimene:cis-3-hexen-1-ol ratio is greater than 3.0:1, the withering process is considered complete, withering is stopped, and the tea enters the fixation process. This significantly reduces the misjudgment rate and improves the stability and consistency of the finished tea quality. Attached Figure Description

[0008] Figure 1 This is a statistical chart showing the aroma detection results obtained by Master A during the greening process using the method of Example 1 in this invention; Figure 2 This is a statistical chart showing the aroma detection results obtained by Master B during the greening process using the method of Example 1 in this invention; Figure 3 The chromatogram of total ion content of aroma from fresh leaves before processing, as described in Example 1 of this invention; Figure 4 The image shows the total ion chromatogram of aroma at the endpoint of green processing, obtained using the method described in Example 1 of this invention. Detailed Implementation

[0009] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0010] This invention is applicable to industrial tea-making applications, enabling accurate determination of the withering endpoint through a portable gas chromatography-mass spectrometry (GC-MS) instrument.

[0011] A method for determining the endpoint of the processing of Wuyi rock tea includes the following steps: using a portable gas chromatography-mass spectrometry (GC-MS) instrument to detect the aroma emitted during the processing, and measuring β-ocimene and cis-3-hexenyl acetate in the aroma; When the area percentage of cis-3-hexenyl acetate is ≤15% for the first two consecutive monitoring tests or the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1, it is determined as the endpoint for greening.

[0012] That is, when the area percentage of cis-3-hexenyl acetate is ≤15% for the first two consecutive monitoring tests, it is determined as the endpoint of the greening process; Alternatively, the endpoint for greening is determined when the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1 in two consecutive monitoring tests for the first time. Wherein, the area percentage = the integral area of ​​a certain component's chromatographic peak ÷ the total peak area of ​​all detected components × 100%.

[0013] As can be seen from the above description, the beneficial effects of the present invention are as follows: At the processing site of Wuyi rock tea, the present invention uses a portable gas chromatography-mass spectrometry (GC-MS) instrument to collect and rapidly analyze the aroma emitted during the withering process. No complex pretreatment is required, and the single detection time is short. It can determine the area percentage of aroma substances β-ocimene and cis-3-hexenyl acetate in the tea leaves in real time. β-ocimene has a sweet floral, herbaceous, and fruity aroma with a delicate terpene fragrance, and is the main floral and fruity aroma substance during the withering process, gradually increasing with the degree of withering. cis-3-hexenyl acetate has a strong grassy and tender leaf aroma, and is the main substance responsible for the grassy aroma of the tea leaves, gradually decreasing with the degree of withering. After multiple experiments, it was found that when the area percentage of cis-3-hexenyl acetate is ≤15% for the first two consecutive monitoring tests, or the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1, it is considered the end point of the withering process. At this point, the grassy aroma is relatively weak, achieving the purpose of withering, and the aroma changes tend to be stable. Stopping withering and proceeding to the fixation process can significantly reduce the misjudgment rate and improve the stability and consistency of the finished tea quality. Furthermore, the higher the area percentage of β-ocimene, the better; the initial grouping can be based on the area percentage of β-ocimene.

[0014] This invention, through two consecutive verifications, can effectively prevent equipment fluctuations and sampling errors, significantly reduce the misjudgment rate, and greatly improve the stability and consistency of tea quality.

[0015] Furthermore, the aroma emitted during the withering process is tested after each shaking.

[0016] Furthermore, the aroma emitted during the withering process was tested every half hour.

[0017] Furthermore, the sampling time for portable gas chromatography-mass spectrometry (GC-MS) is 1–60 min.

[0018] Preferably, the sampling time for portable gas chromatography-mass spectrometry (GC-MS) is 1-5 minutes.

[0019] As can be seen from the above description, the sampling time mainly depends on the concentration of aroma substances and the time requirements. In order to match the rapid progress of the withering process, the sampling time of the target substance concentration is shortened to 1~5 minutes.

[0020] Furthermore, a single data collection and analysis session lasts 10-15 minutes.

[0021] As can be seen from the above description, when the sampling time is shortened to 1-5 minutes, the time for a single collection and analysis in this application is only 10-15 minutes.

[0022] Furthermore, the temperature of the collection tube during portable gas chromatography-mass spectrometry (GC-MS) testing is 30–80°C.

[0023] As can be seen from the above description, in order to prevent certain substances in the sample from condensing in the sampling tube, the temperature of the sampling tube is adjusted to 30~80℃.

[0024] Furthermore, the temperature of the sampling tube during portable gas chromatography-mass spectrometry (GC-MS) testing is 30-40℃.

[0025] As can be seen from the above description, since the ambient temperature during the processing is basically controlled above 30℃ but not exceeding 40℃, the temperature of the collection tube is adjusted to 30~40℃ based on the natural cooling requirement of the collection tube.

[0026] Furthermore, the split ratio of the chromatogram during detection by the portable gas chromatography-mass spectrometry (GC-MS) is 1:20 to 1:40.

[0027] Preferably, the split ratio of the chromatogram is 1:20 to 1:25 when using a portable gas chromatography-mass spectrometry (GC-MS) instrument.

[0028] As can be seen from the above description, the diversion ratio is relatively small, which can ensure the concentration of the target aroma substances during the withering process.

[0029] Furthermore, the column flow rate for detection using a portable gas chromatography-mass spectrometry (GC-MS) instrument is 0.6–1.5 mL / min.

[0030] Preferably, the column flow rate of the chromatogram is 0.8~1.2 mL / min when using a portable gas chromatography-mass spectrometry (GC-MS) instrument.

[0031] As can be seen from the above description, the column flow rate affects the elution time and peak width of aroma substances, and the elution time and peak shape of the target aroma substances are optimal when the flow rate is 0.8~1.2 mL / min.

[0032] Furthermore, the initial column temperature for chromatographic analysis using a portable gas chromatography-mass spectrometry (GC-MS) instrument is 48–52 °C.

[0033] As can be seen from the above description, the initial temperature in the heating process should be higher than the ambient temperature. When the initial column temperature is 48~52℃, it is easier to reach the peak of the aroma components without affecting the cooling process.

[0034] Furthermore, the portable gas chromatography-mass spectrometry (GC-MS) instrument can perform a full scan of mass spectrometry from 45 to 300 amu.

[0035] As can be seen from the above description, considering that the molecular weight of oxygen in the air is 32 and the molecular weight of carbon dioxide is 44, the peaks of both will affect the display of the target aroma substances, and the molecular weight of aroma substances generally does not exceed 300. Therefore, the full scan range has been adjusted from the conventional 30~550 amu to 45~300 amu.

[0036] Embodiment 1 of the present invention is: a method for determining the endpoint of the processing of Wuyi rock tea, the specific steps of which are as follows: S1: A portable gas chromatography-mass spectrometry (GC-MS) instrument was used to detect the aroma emitted during the withering process after each shaking, and to determine the β-ocimene and cis-3-hexenyl acetate in the aroma. Each collection and analysis lasted 10-15 minutes. During the detection process, the sample injection method was adsorption concentration, the sampling time was 1 min, the backflush time was 120 s, the injection time was 15 s, and the temperature of the collection tube was 40℃. Chromatographic conditions were: injection port temperature 130℃, split ratio 1:20, column flow rate 1mL / min, valve box temperature 100℃; column oven temperature program was: initial temperature 50℃, hold for 3 min, increase to 200℃ at 25℃ / min and hold for 1 min, total run time 10 min. The mass spectrometry conditions were: solvent delay 1.0 min, ion source temperature 200℃, transfer line temperature 200℃, and scan type 45~300 amu full scan. S2: When the area percentage of cis-3-hexenyl acetate is ≤15% for the first two consecutive monitoring tests or the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1, it is determined to be the end point of the greening process, and the greening process is stopped and the fixation process begins.

[0037] The topping process of two random topping masters was monitored in real time: 1. Master A first used the judgment method of Example 1 to test and determined that the end point of the withering process should be after three shakings. Then, through human sensory judgment, he stopped the withering process after six shakings when the grassy aroma dropped to an acceptable level. The aroma test results during this process are shown in Table 1 and... Figure 1 .

[0038] Table 1

[0039] The quality of Wuyi rock tea after three and six shaking processes was scored according to the five-factor method of primary processing tea in GB / T 23776-2018 "Sensory Evaluation Methods for Tea". The scoring results were as follows: the quality score of Wuyi rock tea after three shaking was 80.5 points, and the quality score of Wuyi rock tea after six shaking was 73.8 points. As shown in Table 1, the β-ocimene with floral and fruity aroma decreased rapidly after four shaking, indicating obvious over-processing.

[0040] As can be seen from the above, relying on experience to manually judge the endpoint of the greening process is prone to errors, has a high misjudgment rate, and results in low quality consistency.

[0041] 2. Master B first used the judgment method of Example 1 to test and determined that the end point of the withering process should be after six shakings. Then, through human sensory judgment, he stopped the withering process after the grassy aroma dropped to an acceptable value after seven shakings. The aroma test results during this process are shown in Table 2 and... Figure 2 .

[0042] Table 2

[0043] The quality of the Wuyi rock tea after six and seven shakes was scored, and the results were as follows: the quality score of the Wuyi rock tea after six shakes was 93.4 points, and the quality score of the Wuyi rock tea after seven shakes was 92.5 points.

[0044] As can be seen from the withering trends of the two masters, real-time monitoring can effectively determine the end point of withering, predict the withering trend, prevent over-withering, improve the quality of the finished tea, and thus get rid of the subjectivity of traditional human experience judgment.

[0045] 3. The quality of the Wuyi Rock Tea primary processed tea after the first to sixth shaking in Table 1 was scored sequentially. The scoring results are as follows: the quality of the Wuyi Rock Tea primary processed tea after the first and second shaking did not meet the quality scoring requirements; the quality score of the Wuyi Rock Tea primary processed tea before the third shaking was 81.2 points; the quality score of the Wuyi Rock Tea primary processed tea after the third shaking was 80.5 points; the quality score of the Wuyi Rock Tea primary processed tea after the fourth shaking was 79.0 points; the quality score of the Wuyi Rock Tea primary processed tea after the fifth shaking was 75.5 points; and the quality score of the Wuyi Rock Tea primary processed tea after the sixth shaking was 73.8 points.

[0046] The quality of the Wuyi Rock Tea primary processed tea before the first to the seventh shaking in Table 2 was scored sequentially. The scoring results are as follows: the quality of the Wuyi Rock Tea primary processed tea before the first to the third shaking did not meet the quality scoring requirements; the quality score of the Wuyi Rock Tea primary processed tea after the fourth shaking was 77.0 points; the quality score of the Wuyi Rock Tea primary processed tea after the fifth shaking was 91.2 points; the quality score of the Wuyi Rock Tea primary processed tea after the sixth shaking was 92.9 points; and the quality score of the Wuyi Rock Tea primary processed tea after the seventh shaking was 92.0 points.

[0047] As can be seen from the above, the method for determining the greening endpoint of the present invention is accurate. When the area percentage of cis-3-hexenyl acetate is ≤15% or the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1, the greening endpoint can be successfully determined. Embodiment 2 of the present invention is: a method for determining the endpoint of the processing of Wuyi rock tea, the specific steps of which are as follows: S1: A portable gas chromatography-mass spectrometry (GC-MS) instrument was used to detect the aroma emitted during the withering process every half hour, and to determine the β-ocimene and cis-3-hexenyl acetate in the aroma. Each collection and analysis lasted 10-15 minutes. During the detection process, the sample injection method was adsorption concentration, the sampling time was 5 min, the backflush time was 120 s, the injection time was 15 s, and the temperature of the collection tube was 30℃. The chromatographic conditions were as follows: injection port temperature 130℃, split ratio 1:30, column flow rate 0.6mL / min, valve box temperature 100℃; the column oven temperature program was as follows: initial temperature 48℃, hold for 3 min, increase to 200℃ at 25℃ / min and hold for 1 min, total run time 10 min. The mass spectrometry conditions were: solvent delay 1.0 min, ion source temperature 200℃, transfer line temperature 200℃, and scan type 45~300 amu full scan. S2: When the area percentage of cis-3-hexenyl acetate is ≤15% for the first two consecutive monitoring tests, it is determined to be the end point of the greening process, and the greening process is stopped and the fixation process begins.

[0048] Embodiment 3 of the present invention is: a method for determining the endpoint of the processing of Wuyi rock tea, the specific steps of which are as follows: S1: A portable gas chromatography-mass spectrometry (GC-MS) instrument was used to detect the aroma emitted during the withering process after each shaking, and to determine the β-ocimene and cis-3-hexenyl acetate in the aroma. Each collection and analysis lasted 10-15 minutes. During the detection process, the sample injection method was adsorption concentration, the sampling time was 60 min, the backflush time was 120 s, the injection time was 15 s, and the temperature of the collection tube was 80℃. The chromatographic conditions were as follows: injection port temperature 130℃, split ratio 1:40, column flow rate 1.5mL / min, valve box temperature 100℃; the column oven temperature program was as follows: initial temperature 52℃, hold for 3 min, increase to 200℃ at 25℃ / min and hold for 1 min, total run time 10 min. The mass spectrometry conditions were: solvent delay 1.0 min, ion source temperature 200℃, transfer line temperature 200℃, and scan type 45~300 amu full scan. S2: When the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1 for the first two consecutive monitoring tests, it is determined to be the end point of the greening process, and the greening process is stopped and the fixation process begins.

[0049] In summary, the method for determining the endpoint of the processing of Wuyi rock tea provided by this invention has the following advantages: 1. Portable gas chromatography-mass spectrometry (GC-MS) is used to replace the traditional benchtop GC-MS. The equipment is mobile and allows direct injection of tea aroma gases, enabling real-time detection at the processing site. This solves the problems of benchtop instruments being unable to be used on-site and the detection being lagging behind. It is adapted to the production rhythm and can directly guide the control of the tea processing process, making it highly practical. 2. It eliminates complex pretreatment steps and adopts rapid gas injection detection, which greatly shortens the detection time and is compatible with the shaking-drying cycle rhythm; no organic solvent extraction, concentration and other pretreatment are required, which greatly improves the detection speed and meets the needs of rapid quality control. 3. By introducing dynamic change monitoring of aroma substances, the withering trend can be predicted, avoiding misjudgments caused by relying solely on single-point detection; through two consecutive verifications, equipment fluctuations and sampling errors can be effectively prevented, significantly reducing the misjudgment rate and greatly improving the stability and consistency of the finished tea quality. 4. To digitize and standardize the processing of Wuyi rock tea, thus eliminating the subjectivity of traditional manual experience-based judgment.

[0050] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for determining the endpoint of the processing of Wuyi rock tea, characterized in that, Includes the following steps: The aroma emitted during the withering process was detected using a portable gas chromatography-mass spectrometry (GC-MS) instrument, and the β-ocimene and cis-3-hexenyl acetate in the aroma were determined. When the area percentage of cis-3-hexenyl acetate is ≤15% or the ratio of β-ocimene to cis-3-hexenyl acetate is greater than 3.0:1 for the first two consecutive monitoring sessions, it is determined as the greening endpoint.

2. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The aroma emitted during the withering process is tested after each shaking.

3. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The aroma emitted during the withering process is checked every half hour.

4. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The sampling time for the portable gas chromatography-mass spectrometry (GC-MS) instrument is 1 to 60 minutes.

5. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The temperature of the acquisition tube during the detection by the portable gas chromatography-mass spectrometry instrument is 30~80℃.

6. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The split ratio of the chromatogram during detection by the portable gas chromatography-mass spectrometry instrument is 1:20 to 1:

40.

7. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The column flow rate of the portable gas chromatography-mass spectrometry (GC-MS) instrument during detection is 0.6~1.5 mL / min.

8. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The initial column temperature of the chromatogram during detection by the portable gas chromatography-mass spectrometry (GC-MS) is 48-52℃.

9. The method for determining the endpoint of the processing of Wuyi rock tea according to claim 1, characterized in that, The portable gas chromatography-mass spectrometry instrument performs a full scan of mass spectrometry from 45 to 300 amu.

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