A method for identifying storage years of pu'er tea

Abstract

The application discloses a kind of pu'er tea storage age identification method, its method first optimizes sampling point, by sampling in multiple specific areas, while meeting the randomness, it improves the confidence of sampling;Second, different sampling points are matched with different, more targeted detection indexes;Then, according to the order of safety indexes, true and false indexes and quality indexes, the probability of misjudgment is reduced, and the detection efficiency is also taken into account.Finally, the comprehensive determination of age is obtained by fusing chemical composition age and physical parameters.The application solves the problem of strong subjectivity of artificial identification and insufficient reliability of single dimension detection in the prior art, and reduces the misjudgment rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tea detection, in particular to a Pu'er tea storage year identification method. BACKGROUND

[0002] As a unique post-fermented tea in China, the quality of Pu'er tea is significantly positively correlated with the aging years, and the more aged the tea is, the more fragrant it is. The aging years become the core basis for pricing, collecting and trading Pu'er tea. However, there are many irregularities in the market, such as selling new tea as old tea, mixing old tea with new tea, and wet warehouse fraud, especially for raw tea, which has a high value for fraud. If not discovered in time, it will cause great losses to the purchasers.

[0003] Currently, the identification of the years of Pu'er tea mainly relies on the manual identification of appraisers. The manual identification relies on the sensory judgment of the practitioners, and mainly infers the years by observing the color of the dry tea, the color of the tea soup after brewing, and the aroma and taste. This method is completely subject to personal experience accumulation and is highly subjective, and is prone to misjudgment and difficult to promote.

[0004] The prior art also proposes to use scientific means for detection. For example, CN105241929A proposes a method for quickly identifying the storage years of Pu'er tea based on taste information, which uses an electronic tongue system to detect taste to determine the years. For another example, patent application CN110749565A proposes a method for quickly identifying the storage years of Pu'er tea, which uses spectral recognition to determine the storage years. The common advantage of the two is that they are fast, but the detection dimension is single and the misjudgment rate is high. SUMMARY

[0005] One of the purposes of the present application is to provide a Pu'er tea storage year identification method to solve the problem of high misjudgment rate in the existing Pu'er tea year identification.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] S1, sampling at the middle layer center position, the upper surface layer random position and the lower surface layer random position of the Pu'er tea respectively, grinding and sieving each sample to obtain a first sample, a second sample and a third sample respectively, and collecting a fourth sample at the same position of the first sample;

[0008] S2, determining the aflatoxin B1 and artificial synthetic spices of the second sample and the third sample, identifying whether the aflatoxin B1 exceeds the safety threshold and whether the artificial synthetic spices are detected, if yes, determining unqualified; if no, executing S3;

[0009] S3, determining the theabrownin of the first sample, the second sample and the third sample, identifying whether the coefficient of variation of the theabrownin is less than a preset threshold, if yes, executing S4; if no, determining suspected adulterated tea;

[0010] S4, determine the chemical composition of the third sample, match with the reference feature library, determine the chemical age;

[0011] S5, determine the physical parameters of the third sample and the fourth sample, match with the reference feature library, determine the physical age;

[0012] S6, identify whether the difference between the chemical age and the physical age exceeds the preset value, if yes, remind of the abnormality; if no, give the chemical age the main weight, the physical age the secondary weight, and obtain the comprehensive determination age by fusion.

[0013] Further, the middle layer center position samples of Pu'er tea of different years, different regions, different storage environments and different specifications are collected to determine the characteristic indexes to form the reference feature library.

[0014] Further, in S1, the tea needles with a diameter of 0.8-1.0 mm are obliquely sampled, and the sampling amount of the single sample of the middle layer center, the upper surface layer and the lower surface layer is 0.5-0.8 g; the particle size after sieving is controlled at 180±10 μm, and the sieved samples are sealed and stored in a desiccator.

[0015] Further, in S2, the aflatoxin B1 is determined by liquid chromatography, and the safety threshold is set to 5 μg / kg; the artificial synthetic perfume is determined by gas chromatography-mass spectrometry, and when the mass spectrometry library matching degree is ≥95%, it is determined to be detected.

[0016] Further, in S3, the coefficient of variation = standard deviation / average value × 100%, and the preset threshold is 6%.

[0017] Further, S4 includes: determining the contents of the theabrownine, tea polyphenol and benzyl alcohol, respectively matching with the reference feature library to determine the corresponding age of each; identifying whether the difference between the theabrownine and the tea polyphenol corresponding age exceeds the threshold, if yes, reminding of the abnormality; if no, taking the theabrownine age as the main weight, the tea polyphenol and benzyl alcohol age as the secondary weight, and obtaining the chemical age by fusion.

[0018] Further, the theabrownine is detected by HPLC method, the tea polyphenol is detected by Folin phenol colorimetry, and the benzyl alcohol is detected by GC-MS method.

[0019] Further, S5 includes: determining the leaf cell damage rate of the fourth sample, matching with the reference feature library, identifying whether the difference between the leaf cell damage rate and the tea polyphenol corresponding age exceeds the threshold, if yes, reminding of the abnormality; if no, determining the color parameter of the third sample and the tea soup transmittance, if no, giving the color parameter age the main weight, the tea soup transmittance age and the leaf cell damage rate age the secondary weight, and obtaining the physical age by fusion.

[0020] Further, in S4, the weight of theabromine age is 55-65%, the weight of tea polyphenol is 20-30, and the weight of benzyl alcohol is 10-20%; in S5, the weight of the color parameter is 45-55%, the weight of the tea soup transmittance age is 25-35%, and the weight of the leaf cell damage rate age is 15-25%; in S6, the weight of the chemical age is 65-75%, and the weight of the physical age is 25-35%.

[0021] Further, the color parameter is obtained by a scanner; the tea soup transmittance is measured by an ultraviolet spectrophotometer at a set wavelength; and the leaf cell damage rate is observed by a biological microscope, and the number of damaged cells is counted, and the damage rate = damaged cell number / total cell number x 100%.

[0022] Compared with the background art, the present application has the following advantages after adopting the above technical solution:

[0023] The application provides a Pu'er tea storage age identification method, which effectively eliminates toxic tea and adulteration interference by sampling at the middle layer center, the upper surface layer and the lower surface layer, and combining aflatoxin detection and theabromine variation coefficient analysis; and the method solves the problems of strong subjectivity of artificial identification and insufficient reliability of single dimension detection in the prior art, and reduces the misjudgment rate. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a whole process schematic diagram of the present application;

[0025] Figure 2 It is a chemical component detection process schematic diagram of the present application;

[0026] Figure 3 It is a physical parameter detection process schematic diagram of the present application. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application is further described in detail below with reference to the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application. EMBODIMENT

[0028] Please refer to Figure 1 The embodiment of the present application provides a Pu'er tea storage age identification method, which includes:

[0029] S1, sampling at the middle layer center position, the upper surface layer random position and the lower surface layer random position of the Pu'er tea respectively, grinding and sieving each sample to obtain a first sample, a second sample and a third sample respectively, and collecting a fourth sample at the same position of the first sample;

[0030] S2, determine aflatoxin B1 and artificial flavor of the second sample and the third sample, identify whether the aflatoxin B1 exceeds the safety threshold, and whether the artificial flavor is detected, if yes, determine unqualified; if not, execute S3;

[0031] S3, determine the theabromine of the first sample, the second sample and the third sample, identify whether the coefficient of variation of the theabromine is less than the preset threshold, if yes, execute S4; if not, determine as suspected adulterated tea;

[0032] S4, determine the chemical components of the third sample, match with the reference feature library, and determine the chemical age;

[0033] S5, determine the physical parameters of the third sample and the fourth sample, match with the reference feature library, and determine the physical age;

[0034] S6, identify whether the difference between the chemical age and the physical age exceeds the preset value, if yes, remind of the abnormality; if not, give the chemical age the primary weight and the physical age the secondary weight, and obtain the comprehensive determination age by fusion.

[0035] Firstly, the application divides the identification indexes into safety indexes, authenticity indexes and quality indexes, directly determines the tea not meeting the safety indexes as unqualified, outputs a warning for the adulterated tea with suspected authenticity, and finally detects the quality indexes to identify the age, which not only reduces unnecessary monitoring, but also improves the safety of tea.

[0036] Secondly, the application optimizes the sampling positions and identification indexes, wherein the second sample and the third sample are collected at the surface layer, because the synthesis of aflatoxin B1 requires oxygen and high humidity, and the surface layer is more likely to meet this condition than the inside of the tea cake, therefore, the surface layer is the highest place of aflatoxin B1, if the surface layer also meets the safety indexes, it can be determined that the tea cake meets the safety indexes. In addition, because the wet storage tea is promoted to age by high temperature and high humidity, it is easy to produce aflatoxin B1, and through the detection of aflatoxin B1, such artificially aged tea can be excluded in the first stage. At the same time, the content of benzyl alcohol in new tea is low, and it lacks fragrance, so the counterfeiters often add artificial flavor to make up for the defect of fragrance, thereby, such flavor tea can also be excluded. Random sampling at the upper surface layer and the lower surface layer reduces the phenomenon of targeted counterfeiting by suppliers against the detection method.

[0037] Furthermore, theabromine is the final product of the aging of Pu'er tea, its formation depends on long-term oxidation polymerization, and its reaction process is relatively uniform in the tea cake, and it has high stability, in other words, the theabromine content in the surface layer and the middle layer of the normal aged Pu'er tea has little difference. Therefore, in S3, the application can quickly identify the common counterfeited tea of scattering surface tea (the surface layer is aged tea, and the core is new tea) through the difference of theabromine in the middle layer and the surface layer.

[0038] In addition, the center position of the middle layer of the tea cake is uniformly pressed by the pressing pressure, the raw material distribution is most stable, the air contact is moderate, the aging speed is balanced, so that the chemical composition and the physical parameters are most stable, the natural difference is smallest, it is easy to match with the reference feature library, and the part is difficult to be intentionally adulterated, therefore, the third test sample and the fourth test sample are sampled from the position, to truly reflect the overall aging state of the tea cake.

[0039] Finally, the application combines the detection of chemical composition and physical parameters to comprehensively evaluate from two dimensions, and improves the accuracy of judgment. Specifically, the essence of Pu'er tea aging is chemical change, so the chemical composition can more directly reflect the post-fermentation aging process, and the physical parameter is an indirect embodiment of the aging process, therefore, the chemical composition is more directional than the physical parameter, and at the same time, the detection of chemical composition is relatively more accurate than the physical parameter, so the application takes the chemical composition age as the main weight. But at the same time, the physical composition is supplemented, to avoid some wet storage tea which is not moldy although it is aged in high temperature and high humidity.

[0040] Therefore, the application realizes multi-dimensional year determination through close cooperation of each step from sample collection to safety screening, consistency verification, and determination and fusion of chemical and physical age, effectively overcomes the problems of strong subjectivity and high misjudgment rate of artificial identification, and also solves the limitation of single detection dimension of the existing scientific method.

[0041] It should be understood that the accuracy of the judgment result of the present application when making year judgment also depends on the reference feature library, which is consistent with the prior art using electronic tongue or spectral detection. This is because the characteristic index of Pu'er tea changes with the year, which is related to its place of origin, storage environment, specification and other factors and varies greatly, and can only be determined by actual sample measurement to establish a reference database to obtain prior knowledge for comparison. However, this does not hinder the implementation of the present application and related prior art, because Pu'er tea has its particularity: 1. Based on the food safety and detection cost of tea, tea merchants usually purchase tea products of fixed origin, fixed tea warehouse and customized specification, and mostly in bulk, rather than individual collection or loose tea of unknown origin. Therefore, when purchasing, the supplier will provide the corresponding traceability certificate and parameter description of the tea product. The core purpose of such detection technology is to verify the supplier's self-reported parameters to avoid high economic losses caused by the introduction of large amounts of abnormal tea in bulk purchase; 2. Unlike other tea varieties, Pu'er tea has a strong place of origin attribute, and only Pu'er tea from a market-recognized place of origin has a high market value. Therefore, tea merchants can collect features for these high-value categories to establish a reference feature library; 3. Based on the strong site attribute of Pu'er tea, tea suppliers will purposefully establish large tea warehouses corresponding to the site to store and age Pu'er tea to obtain year tea, and the storage conditions are relatively fixed after the completion of the tea warehouse construction, so the year is relatively easy to verify through its characteristic index; 4. After the establishment of the reference feature library, it is not static, but is enriched with the increase of real samples obtained by tea merchants, and the characteristic index of the same tea product is also corrected with the increase of the real sample.

[0042] Therefore, the present application further proposes to collect middle layer center position samples of Pu'er tea of different years, different regions, different storage environments and different specifications to form a reference feature library.

[0043] As described above, the center position of the middle layer is the most stable position, and by unifying the reference feature library and the position of the subsequent identification sample, the result can be easily compared. In addition, as shown in Table 1, the reference feature library includes parameters of different regions, different storage environments and different tea cake specifications, so that the reference feature library and the test sample are easily matched, and the theoretical parameters of the test sample are easily compared with the self-reported parameters of the supplier, thereby identifying abnormalities. It should be understood that Table 1 is only an example of the reference feature library, and in the actual feature library, the years can be divided into finer granularity, such as months, and finer granularity is beneficial to more accurately determine the age.

[0044]

[0045] The application further proposes that in the above-mentioned Pu'er tea storage year identification method, the tea needles with a diameter of 0.8-1.0 mm are obliquely sampled in S1; a 80-mesh stainless steel standard sieve is used for sieving, and the particle size of the tea powder is controlled to be 180±10 μm, and the tea powder is immediately sealed and stored in a desiccator after sieving.

[0046] The application samples the superfine tea needles with a diameter of 0.8-1.0 mm, only leaves the pinhole-level trace which is difficult to observe by naked eyes after sampling, at the same time, the oblique 45° insertion can disperse the stress, avoid the tea cake cracks and looseness caused by the stress concentration when vertically sampling, avoid the damage to the tea cake caused by sampling and harm its collection or sales value. Through grinding and sieving, the cell wall is destroyed, the ingredient extraction efficiency is improved, and the consistency of the sample is ensured, and the detection difference caused by different particles is avoided. Through sealing preservation, hygroscopicity and oxidation are avoided, and the benzyl alcohol volatilization is inhibited.

[0047] The application further proposes that in S2, the aflatoxin B1 is determined by liquid chromatography, and the safety threshold is set to 5 μg / kg; the artificial synthetic perfume is determined by gas chromatography-mass spectrometry, and when the mass spectrometry library matching degree is ≥95%, it is determined to be detected.

[0048] Specifically, in one example, 0.1 g of the second sample and the third sample are weighed, placed in a 2 mL microcentrifuge tube, 1 mL of a methanol-water mixture (7:3, v / v) is added, vortexed for 2 min, ultrasonic extraction is performed for 30 min, the power is 400 W, the temperature is 50°C, then 12000 rpm centrifugation is performed for 15 min, 0.5 mL of supernatant is taken, and filtration is performed through a 0.22 μm organic phase filter membrane. Then, the filtered liquid is passed through a micro-immune affinity column (column capacity ≥10 ng, column volume 0.5 mL) at a flow rate of 0.5 drops / sec, washed with 1 mL of PBS buffer, eluted with 0.5 mL of methanol, and the eluent is directly injected. A narrow-diameter C18 column is selected for the chromatographic column, the mobile phase is methanol-water (45:55, v / v), the flow rate is 0.3 mL / min; a fluorescence detector is used for detection, the excitation wavelength of the fluorescence detector is 365 nm, the emission wavelength is 450 nm, the gain value is increased to 1.5 times, the injection amount is 50 μL, and the detection of aflatoxin B1 is completed.

[0049] Take 0.1 g of the second sample and the third sample, place them in a 5 mL headspace bottle, add 1 mL of ultrapure water, seal and ultrasonic for 15 min, constant temperature at 85℃ for 30 min, magnetic stirring speed 500 rpm; headspace injection needle temperature 120℃, injection volume 0.5 mL. Gas chromatography uses a DB-5MS capillary column, carrier gas flow rate 0.8 mL / min, programmed temperature, initial temperature 40℃, hold for 1 min, increase to 250℃ at a rate of 8℃ / min, hold for 3 min; mass spectrometry EI source temperature 250℃, SIM mode ion residence time 100 ms, scan range m / z=50-400, match target flavors such as benzaldehyde m / z=106, maltol m / z=126.

[0050] The application further proposes that the coefficient of variation in S3 = standard deviation / average value x 100%, and the preset threshold is 6%.

[0051] For example, the thearubigin content of the upper layer is 7%, the thearubigin content of the middle layer is 2%, and the thearubigin content of the lower layer is 7%, then the average value is 7%+2%+7%÷3=5.333%, the square of the difference is the upper layer 1.667%²≈2.778%², the middle layer -3.333%²≈11.111%², and the lower layer 1.667%²≈2.778%², the sum of squares =2.778+11.111+2.778≈16.667%², the standard deviation =√[16.667÷(3-1)]=2.887%, the coefficient of variation =2.887%÷5.333%)x100%≈54.13%, and it is determined that the tea is adulterated, that is, the surface is old tea and the inside is new tea.

[0052] Please refer to Figure 2 As shown in the figure, the application further proposes the following scheme: the contents of thearubigin, tea polyphenol, and benzyl alcohol are determined, matched with the reference feature library respectively to determine the corresponding age; it is identified whether the age difference of thearubigin and tea polyphenol exceeds the threshold value, if yes, an abnormality is reminded; if no, the chemical age is obtained by fusing thearubigin age as the main weight, and tea polyphenol and benzyl alcohol age as the secondary weight.

[0053] In one example, the thearubigin is detected by HPLC method, the mobile phase is methanol-0.1% phosphoric acid (50:50), the flow rate is 1.0 mL / min, and the detection wavelength is 460 nm; the extract is filtered through a 0.22 μm filter membrane before injection; the tea polyphenol is detected by Folin phenol colorimetry, the absorbance is determined by 765 nm wavelength, the standard curve is drawn with gallic acid as the standard, and the total polyphenol content is calculated; the benzyl alcohol is detected by GC-MS method, the characteristic ion m / z=108 is monitored in SIM mode, and the external standard method is used for quantification.

[0054] Since theabrownin is converted from tea polyphenols, the increase of theabrownin will inevitably lead to the decrease of tea polyphenols in the normal aging process. Therefore, the application compares the corresponding age of theabrownin and tea polyphenols. If the difference exceeds the threshold value (such as 2 years), it is abnormal and reminds the tester to check the sample, instrument and recheck the process to determine the abnormality of the tea cake.

[0055] If the tea cake is normal, theabrownin age is further taken as the main weight, and the age of tea polyphenols and benzyl alcohol is taken as the secondary weight, and the chemical age is obtained by fusion.

[0056] Please refer to Figure 3 As shown in the figure, the application further comprises S5: determining the leaf cell damage rate of the fourth sample, matching with the reference feature library, identifying whether the age difference of the leaf cell damage rate corresponding to the tea polyphenol exceeds the threshold value, if yes, reminding the abnormality; if no, determining the color parameter and the tea soup light transmittance of the third sample, if no, giving the color parameter age main weight, the tea soup light transmittance age and the leaf cell damage rate age secondary weight, and obtaining the physical age by fusion.

[0057] In natural aging, the cell wall of tea will be gradually damaged with the change of microbial metabolism and chemical composition, and the damage rate is strongly positively correlated with the age. Artificial fake is difficult to simulate uniform and natural damage state. At the same time, tea polyphenols are oxidized and degraded with aging, and the rule is stable, which is highly synchronized with the change trend of leaf cell damage rate. In natural aging, the age difference between the two is ≤1.5 years. Therefore, the application can further identify the fake tea with different physical and chemical aging marks by whether the age difference of the leaf cell damage rate corresponding to the tea polyphenol exceeds the threshold value, and avoid the misjudgment of dyeing tea with high material age in the subsequent color parameter age detection due to the high weight of color parameter.

[0058] After no abnormality is identified, the subsequent physical parameter detection is continued. The color parameter adopts a 400 dpi resolution scanner to obtain CIELab value, and the detection environment brightness is ≤500 lux. The tea soup light transmittance is measured by ultraviolet spectrophotometer at 600 nm wavelength, and the brewing ratio is tea powder: boiling water = 1:50. The leaf cell damage rate is observed by 400 times biological microscope, and the damage number of 200-300 complete cells is counted, and the damage rate = damage cell number / total cell number × 100%.

[0059] The color parameters L* / a* / b* are dimensionless values, L* is a lightness index (0 = pure black, 100 = pure white), a* is a red-green component index (positive number is red, negative number is green), and b* is a yellow-blue component index (positive number is yellow, negative number is green). The L* value decreases with the increase of theabrine, and the a* value increases with the increase of the thearubigin, and the correlation coefficient with the age is usually greater than 0.96, which is the parameter closest to the essence of aging among physical parameters, therefore, L* and a* which directly reflect the content changes of theabrine and thearubigin are taken as age control indexes to determine the age, and then L* is taken as the calculation index. The tea soup transmittance is an indirect physical index of chemical composition stability, the longer the aging time, the more sufficient the degradation of easily scattered substances such as tea polyphenols and soluble proteins, and the higher the transmittance, which is strongly positively correlated with the age. Therefore, the color parameter is given a higher weight, then the tea soup transmittance, and then the leaf cell damage rate.

[0060] The initial weight of each single index in the present application is calculated by the Pearson correlation coefficient and the coefficient of variation, and this process does not consider the aging essence of Pu'er tea.

[0061] Firstly, the Pearson correlation coefficient R is calculated by querying each index in the sample table such as Table 2, and then:

[0062]

[0063] In the formula, n is the sample quantity, which is not less than 100 groups, is the index content value of the ith sample, is the average value of the index content of the n samples, is the true age value of the ith sample, is the average value of the true age of the n samples.

[0064]

[0065] Secondly, the ratio of the standard deviation to the average value is calculated by detecting the same index of the same sample for 5 times, and the coefficient of variation CV is obtained, and Table 3 is obtained.

[0066]

[0067] Finally, the initial weight is calculated by classifying the chemical indexes and the physical indexes respectively, and then:

[0068]

[0069] In the formula, = the Pearson correlation coefficient (absolute value) of the index, = the detection coefficient of variation of the index; = the number of indexes in the same category, Pearson correlation coefficient of the same category index, Index detection coefficient of variation of the same category index.

[0070] The initial weight of theabrownine in the chemical index is about 38%, the initial weight of tea polyphenols is about 35%, and the initial weight of benzyl alcohol is about 27%; in the physical index, the initial weight of the color parameter is about 37%, the initial weight of the tea soup transmittance is about 33%, and the initial weight of the leaf cell damage rate is about 30%.

[0071] After obtaining the initial weight, the initial weight is adjusted based on the aforementioned qualitative analysis of the aging rule of Pu'er tea to obtain the weight of each index.

[0072] Specifically, on the basis of the initial weight, the weight gradient grouping as shown in Table 4 is designed:

[0073]

[0074] Select real year 1-10 year Pu'er tea samples, 10 groups of samples per year, and calculate the comprehensive age with weight groups G0-G8, and calculate the MAE value compared with the real age, then,

[0075]

[0076] In the formula, n is the number of samples, which is 100 here, and Table 5 is obtained by calculation.

[0077]

[0078] It can be seen that the essence of aging of Pu'er tea is chemical change, and appropriately increasing the overall weight of chemical age is beneficial to improve the accuracy of age determination, and theabrownine as the final product of aging has the strongest stability, and increasing its weight can suppress the interference of tea polyphenols and the volatilization interference of benzyl alcohol due to the difference of raw materials; physical change is an indirect manifestation of chemical change, and among them, the color parameter directly maps the chemical pigment change, and by increasing the weight of the color parameter, the interference of chemical index can be calibrated to make the detection accuracy more accurate.

[0079] Therefore, through the above verification, the weight of the chemical age is preferably 70% (in the calculation of the chemical age, the weight of theabrownine is preferably 60%, the weight of tea polyphenols is preferably 25%, and the weight of benzyl alcohol is preferably 15%), and the weight of the physical age is preferably 30% (in the calculation of the physical age, the weight of the color parameter L* is preferably 50%, the weight of the tea soup transmittance is preferably 30%, and the weight of the leaf cell damage rate is preferably 20%).

[0080] The above weight is applicable to Pu'er tea year determination of Pu'er producing areas and Lincang producing areas. On this basis, for tea leaves of different producing areas, a weight range of ±5% is configured, and targeted fine tuning can be performed in the weight range, so as to balance the universality and accuracy of the application.

[0081] The above merely describes a preferred specific embodiment of the application, but the protection scope of the application is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application. Therefore, the protection scope of the application should be subject to the protection scope of the claims.

Claims

1. A method for determining the storage age of Pu-erh tea, characterized in that, include: S1. Samples were taken from the center of the middle layer, a random position on the upper surface, and a random position on the lower surface of the Pu'er tea. Each sample was ground and sieved to obtain the first sample, the second sample, and the third sample. A fourth sample was collected from the same position as the first sample. S2. Measure the aflatoxin B1 and artificial flavoring in the second and third samples, and identify whether aflatoxin B1 exceeds the safety threshold and whether artificial flavoring is detected. If yes, it is deemed unqualified; if no, proceed to S3. S3. Measure the theabrownins in the first, second, and third samples, and identify whether the coefficient of variation of theabrownins is less than a preset threshold. If yes, proceed to S4; otherwise, determine that it is suspected adulterated tea. S4. Determine the chemical composition of the third sample and match it with the benchmark feature library to determine the chemical age: Determine the content of theabrownin, tea polyphenols, and benzyl alcohol, and match them with the benchmark feature library to determine the corresponding age; Identify whether the age difference corresponding to theabrownin and tea polyphenols exceeds the threshold. If so, alert for an anomaly; if not, use the age of theabrownin as the main weight and the ages of tea polyphenols and benzyl alcohol as the secondary weights to obtain the chemical age. S5. Measure the physical parameters of the third and fourth samples and match them with the benchmark feature library to determine the physical age: Measure the leaf cell damage rate of the fourth sample and match it with the benchmark feature library. Identify whether the difference between the leaf cell damage rate and the age corresponding to tea polyphenols exceeds the threshold. If so, alert for an anomaly; if not, measure the color parameters and tea infusion transmittance of the third sample, assign primary weight to the age of the color parameters, secondary weight to the age of the tea infusion transmittance and the age of the leaf cell damage rate, and fuse them to obtain the physical age. S6. Identify whether the difference between chemical age and physical age exceeds the preset value. If so, issue an error warning. If not, assign primary weight to chemical age and secondary weight to physical age, and combine them to obtain a comprehensive age determination.

2. The method for determining the storage age of Pu'er tea as described in claim 1, characterized in that: Samples of Pu'er tea from different years, regions, storage environments, and specifications were collected from the center of the middle layer. Their chemical composition and physical parameters were measured to form a baseline feature library.

3. The method for determining the storage age of Pu'er tea as described in claim 1, characterized in that: In S1, tea needles with a diameter of 0.8–1.0 mm were used for oblique sampling, and the sample size for a single sample was 0.5–0.8 g. The particle size after sieving was 180±10 μm, and the samples were sealed and stored in a desiccator after sieving.

4. The method for determining the storage age of Pu'er tea as described in claim 1, characterized in that: Aflatoxin B1 in S2 was determined by liquid chromatography, with a safety threshold set at 5 μg / kg; synthetic fragrances were determined by gas chromatography-mass spectrometry, and were considered to be detected when the mass spectral library matching degree was ≥95%.

5. The method for determining the storage age of Pu'er tea as described in claim 1, characterized in that: In S3, the coefficient of variation is calculated as the standard deviation / mean × 100%, with a preset threshold of 6%.

6. The method for determining the storage age of Pu'er tea as described in claim 1, characterized in that: Theabrownins were detected by HPLC, tea polyphenols by Folin-Ciocalteu colorimetric method, and benzyl alcohol by GC-MS method.

7. The method for identifying the storage age of Pu'er tea as described in claim 1, characterized in that: In S4, the weight of the age of theabrownin is 55-65%, the weight of tea polyphenols is 20-30%, and the weight of benzyl alcohol is 10-20%. In S5, the weight of color parameters is 45-55%, the weight of tea liquor transmittance over years is 25-35%, and the weight of leaf cell damage rate over years is 15-25%. In S6, the weight of chemical age is 65-75%, and the weight of physical age is 25-35%.

8. The method for determining the storage age of Pu'er tea as described in claim 1, characterized in that: Color parameters were obtained using a scanner; the transmittance of the tea infusion was measured using an ultraviolet spectrophotometer at a set wavelength; the leaf cell damage rate was observed using a biological microscope, and the number of damaged cells was counted. Damage rate = number of damaged cells / total number of cells × 100%.

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