Method for identifying fresh cocoons and dried cocoons based on stable isotope technology

Abstract

The invention relates to the technical field of silkworm cocoon identification methods, and discloses a method for identifying fresh cocoons and dried cocoons based on a stable isotope technology, and the method comprises the following steps: 1) carrying out decontamination treatment on the surfaces of a collected fresh cocoon sample and a collected dried cocoon sample; 2) pre-drying the fresh cocoon sample and the dried cocoon sample, and placing the dried samples in a standard atmospheric environment for moisture absorption balance; 3) crushing the fresh cocoon sample and the dried cocoon sample which reach the moisture absorption balance into fine particles for detection; and 4) measuring the isotope ratio of hydrogen and oxygen in the sample by using an isotope ratio mass spectrometer, and calculating a delta value according to a calculation formula: delta = (R sample / R standard-1) * 1000. The method is non-destructive, can effectively avoid subjective factors and errors in a traditional identification method, and can be widely applied to identification of fresh cocoons and dried cocoons in the silk industry.

Description

Technical Field

[0001] The invention belongs to the technical field of silkworm cocoon identification methods, and more specifically relates to a method for identifying fresh cocoons and dry cocoons based on stable isotope technology. Background Art

[0002] Fresh cocoons usually refer to the purchase of fresh cocoons that are freeze-dried and stored, while dry cocoons are stored after being processed using traditional high-temperature drying technology. Since fresh cocoons do not require high-temperature cocoon drying and cocoon boiling processes during the production process, the energy consumption is low, and fresh cocoons are easier to reel than dry cocoons, so their production efficiency is high and the labor cost of workers is low. Therefore, the price of fresh cocoons is low, which has become the development trend of raw silk processing. In addition, fresh cocoon reeling companies can also make full use of silkworm pupae, a by-product of fresh cocoon silk production, to obtain higher economic profits. However, due to its high moisture content, it may affect the quality and production efficiency of silk in the short term. In contrast, dry cocoons have a lower moisture content, better quality, better storage and stability, a wider market, and can be stored and exported for a long time. It is the main product in the international silk market. Therefore, the undesirable phenomenon of trading frozen fresh cocoons as dry cocoons to seek high profits often occurs. Summary of the invention

[0003] The main purpose of the present invention is to provide a method for distinguishing fresh cocoons from dry cocoons based on a stable isotope technology in order to solve the above problems. The method adopts elemental analysis-isotope ratio mass spectrometry to measure the hydrogen and oxygen isotope ratios in fresh cocoons and dry cocoons, and establishes a method for distinguishing and identifying the two. The method has a small sampling amount (1-2 mg), high sensitivity, and a simple method, and can effectively distinguish fresh cocoons from dry cocoons.

[0004] In order to achieve the above object, the present invention is implemented by the following technical solutions:

[0005] A method for identifying fresh cocoons and dried cocoons based on stable isotope technology comprises the following steps:

[0006] 1) Decontamination treatment is performed on the surfaces of the collected fresh cocoon samples and the dried cocoon samples;

[0007] 2) then pre-drying the fresh cocoon samples and the dried cocoon samples, and placing the dried samples in a standard atmosphere for moisture absorption equilibrium;

[0008] 3) crushing the fresh cocoon samples and the dry cocoon samples that have reached moisture absorption equilibrium into fine particles for testing;

[0009] 4) Use an isotope ratio mass spectrometer to measure the isotope ratio of hydrogen and oxygen in the sample, and then calculate the δ value according to the calculation formula: δ=(R 样品 / R 标准 -1)×1000;

[0010] where δ represents the per mille difference between the isotope ratio of the sample and that of the internationally recognized standard sample, with the unit of ‰; R 样品 is the isotope ratio of the heavy element to the light element in the sample; R 标准 is the isotope ratio of the heavy element to the light element in the internationally recognized standard sample;

[0011] 5) Identifying fresh cocoons and dry cocoons based on the δ value: The δ 2 H of the hydrogen isotope value ratio of dry cocoons is more positive compared to the δ 2 H of the hydrogen isotope value ratio of fresh cocoons, while the δ18O of the oxygen isotope value ratio of dry cocoons is more negative compared to the δ18O of the oxygen isotope value ratio of fresh cocoons.

[0012] The sample needs to undergo moisture absorption equilibrium before isotope ratio determination. Conducting isotope ratio determination directly without moisture absorption equilibrium will affect the stability of the measurement results and introduce errors. The storage time, temperature, and humidity conditions of fresh cocoons and dry cocoons in different environments are different, resulting in different internal moisture contents. Since the stable isotope ratios of hydrogen and oxygen mainly come from the moisture in the sample, changes in moisture content will directly affect the stability of the measured values. Since the absolute contents of C, H, O, and N in fresh cocoons and dry cocoons change little, it is difficult to use them as a distinguishing standard. During the evaporation and moisture absorption processes of cocoon moisture, a stable isotope fractionation effect will occur, resulting in changes in δ2H and δ18O. The heavy isotope (2H) is enriched relative to the international standard, while the heavy isotope (18O) is depleted relative to the international standard. Due to the influence of different preparation processes and internal moisture on dry cocoons and fresh cocoons, there will be an obvious difference in the δ2H and δ18O values between the two.

[0013] Using the isotope ratios (δ2H, δ18O) of hydrogen and oxygen instead of individual isotope values is because the isotope ratio is usually expressed as the per mille difference between its isotope ratio and that of the international standard (such as VSMOW). Using the ratio can eliminate the systematic error in the absolute value and ensure the comparability of data. The isotope ratio directly measured by IRMS may be affected by factors such as moisture state and environmental humidity and cannot accurately reflect the essential differences between fresh cocoons and dry cocoons. Therefore, through δ value correction, the influence of experimental conditions and instrument drift on data can be reduced, the stability and comparability of the measured values can be improved, and fresh cocoons and dry cocoons can be more effectively distinguished.

[0014] Further preferably, the decontamination treatment includes: cleaning the surface of the cocoon with deionized water to remove pollutants that affect stable isotope analysis, including soil and impurities.

[0015] Further preferably, the number of times of deionized water cleaning treatment is 2 - 3 times.

[0016] Further preferably, at least 10 samples should be collected separately for fresh cocoon samples and dry cocoon samples, and each sample should include the front, middle, and rear parts of the cocoon to ensure the comprehensiveness of the extracted data.

[0017] Further preferably, the drying temperature is 60 - 80 °C and the time is 1 - 2 h.

[0018] Further preferably, the time for moisture absorption and equilibrium in the standard atmospheric environment is: 8 - 12 h for fresh cocoons and 4 - 6 h for dry cocoons.

[0019] Further preferably, the size obtained by crushing should meet within 3 mm × 3 mm.

[0020] Further preferably, the model of the isotope ratio mass spectrometer is MAT253.

[0021] Further preferably, during the use of the isotope ratio mass spectrometer, the sample to be measured needs to be wrapped in a silver cup, and H2 and CO are used as reference gases. The combustion furnace temperature is 1300 - 1400 °C, the chromatographic column temperature is 70 - 80 °C, and the helium purge flow rate is 150 - 200 mL / min.

[0022] Further preferably, during the use of the isotope ratio mass spectrometer, standard samples IAEA-CH-7 and USGS42 are selected to correct the sample test results.

[0023] Further preferably, δ 2 H and δ 18 O's relative standard R 标准 is VSMOW.

[0024] Compared with the prior art, the present invention has the following advantages:

[0025] (1) The present invention adopts stable isotope analysis technology, which does not require sample destruction, is suitable for batch rapid detection, and retains sample integrity. Compared with traditional moisture measurement or appearance inspection methods, this method has higher applicability and convenience, avoiding the waste and inaccuracy caused by destructive detection.

[0026] (2) The present invention uses stable isotope technology to analyze the isotope ratio differences between fresh cocoons and dry cocoons, which can provide more accurate identification results. It can also exclude the interference of environmental factors on the results and improve the reliability of identification.

[0027] (3) The present invention can be applied to different production, storage, and transportation links of fresh cocoons and dry cocoons, with a wide range of applications. Compared with the prior art, the operation of this method is simpler and faster, and can be completed by conventional equipment (such as isotope ratio mass spectrometer IRMS), reducing the requirements for experimental equipment and technical thresholds.

[0028] (4) The present invention does not use any chemical reagents, and the environmental pollution is zero. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 Isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) for fresh cocoons and dried cocoons in Example 1;

[0030] Figure 2 Isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) for fresh cocoons and dried cocoons in Example 2;

[0031] Figure 3 Isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) for fresh cocoons and dried cocoons in Example 3;

[0032] Figure 4 Isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) for fresh cocoons and dried cocoons in Example 4;

[0033] Figure 5 Isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) for fresh cocoons and dried cocoons in Comparative Example 1;

[0034] Figure 6 Isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) for fresh cocoons and dried cocoons in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0035] The following further elaborates on the above content of the present invention through examples, but it should not be understood that the scope of the above subject matter of the present invention is limited to the following examples. Any technology implemented based on the above content of the present invention falls within the scope of the present invention.

[0036] Example 1

[0037] 1) Perform decontamination treatment on the surfaces of the collected fresh cocoons of Zhejiang 24 and dried cocoons of Zhejiang 23. Wash the surfaces of the cocoons 3 times with deionized water to remove soil, impurities, and other pollutants that may affect stable isotope analysis.

[0038] 2) Then, select 10 samples each from the collected fresh cocoons of Zhejiang 24 and dried cocoons of Zhejiang 23, dry them in an oven at 60°C for 6 hours, and place the dried samples in a standard atmospheric environment for moisture absorption equilibrium. The equilibrium time for fresh cocoons is 10 hours, and the equilibrium time for dried cocoons is 5 hours.

[0039] 3) Then, take a part from each of the front, middle, and rear parts of the cocoon sample, cut them into small particles of 1.5 mm × 1.5 mm, mix them together, and store them in a sample bottle in a desiccator for future measurement.

[0040] 4) Use an isotope ratio mass spectrometer (IRMS) of model MAT253 to measure the hydrogen and oxygen isotope ratios of the sample. The sample is wrapped in a silver cup (3.3 mm x 5 mm), enters the elemental analyzer through an auto-sampler, and uses H2 and CO as reference gases. The combustion furnace temperature is 1380 °C; the chromatographic column temperature is 80 °C; the helium purge flow rate is 180 mL / min. After separation in the constant-temperature chromatographic column and dilution with helium, it enters the isotope ratio mass spectrometer for detection: Select standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δ 18 O = 8.57‰) to correct the test results of the sample. To ensure the accuracy of the test results, insert 1 standard sample every 12 samples, and repeat the measurement of each sample 3 times and then take the average value.

[0041] 5) Calculate according to the calculation formula: δ = (R 样品 / R 标准 -1) × 1000.

[0042] Example 2

[0043] 1) Perform a decontamination treatment on the surfaces of the collected fresh cocoons of Henan 24 and dried cocoons of Henan 23. Wash the surfaces of the cocoons 3 times with deionized water to remove soil, impurities, and other pollutants that may affect stable isotope analysis.

[0044] 2) Then, select 10 samples from each of the collected fresh cocoons of Henan 24 and dried cocoons of Henan 23, dry them in an oven at 70 °C for 8 h, and place the dried samples in a standard atmospheric environment for moisture absorption equilibrium. The equilibrium time for fresh cocoons is 8 h, and the equilibrium time for dried cocoons is 4 h.

[0045] 3) Then, take a part from each of the front, middle, and rear parts of the cocoon sample, cut them into small particles of 2 mm × 2 mm, mix them together, and store them in a sample bottle in a desiccator for future measurement.

[0046] 4) Use an isotope ratio mass spectrometer (IRMS) of model MAT253 to measure the hydrogen and oxygen isotope ratios of the sample. The sample is wrapped in a silver cup (3.3 mm x 5 mm), enters the elemental analyzer through an auto-sampler, and uses H2 and CO as reference gases. The combustion furnace temperature is 1380 °C; the chromatographic column temperature is 80 °C; the helium purge flow rate is 180 mL / min. After separation in the constant-temperature chromatographic column and dilution with helium, it enters the isotope ratio mass spectrometer for detection: Select standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δ 18Calibrate the test results of the samples with the standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δO = 8.57‰). To ensure the accuracy of the test results, insert 1 standard sample every 12 samples, and take the average value after repeating the measurement of each sample 3 times.

[0047] 5) Calculate according to the calculation formula: δ = (R 样品 / R 标准 - 1) × 1000.

[0048] Example 3

[0049] 1) Perform decontamination treatment on the surfaces of the collected fresh cocoons of Jiangsu 24 and dry cocoons of Jiangsu 23. Wash the surfaces of the cocoons 3 times with deionized water to remove soil, impurities and other pollutants that may affect stable isotope analysis.

[0050] 2) Then select 15 samples each from the collected fresh cocoons of Jiangsu 24 and dry cocoons of Jiangsu 23 and dry them in an oven at 60 °C for 6 h. Place the dried samples in a standard atmospheric environment for moisture absorption and equilibrium, where the equilibrium time for fresh cocoons is 12 h and the equilibrium time for dry cocoons is 6 h.

[0051] 3) Then take a part from the front, middle and rear parts of the cocoon samples respectively, cut them into small particles of 1.5 mm × 1.5 mm, mix them together and store them in a sample bottle in a desiccator for testing.

[0052] 4) Use an isotope ratio mass spectrometer (IRMS) of model MAT253 to measure the hydrogen and oxygen isotope ratios of the samples. The samples are wrapped in silver cups (3.3 mm x 5 mm) and enter the elemental analyzer through an automatic sampler, and use H2 and CO as reference gases. The temperature of the combustion furnace is 1380 °C; the temperature of the chromatographic column is 80 °C; the helium purge flow rate is 180 mL / min. After separation in the constant temperature chromatographic column and dilution with helium, enter the isotope ratio mass spectrometer for detection: Calibrate the test results of the samples with the standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δ 18 O = 8.57‰). To ensure the accuracy of the test results, insert 1 standard sample every 12 samples, and take the average value after repeating the measurement of each sample 3 times.

[0053] 5) Calculate according to the calculation formula: δ = (R 样品 / R 标准 - 1) × 1000.

[0054] Example 4

[0055] 1) Perform decontamination treatment on the surfaces of the collected fresh cocoons of Fujian 24 and dry cocoons of Fujian 23. Wash the surfaces of the cocoons 3 times with deionized water to remove soil, impurities and other pollutants that may affect stable isotope analysis.

[0056] 2) Then, 15 samples were selected from the collected 24 fresh cocoons and 23 dry cocoons in Fujian, dried in an oven at 60 °C for 10 h, and the dried samples were placed in a standard atmospheric environment for moisture absorption and equilibrium. The equilibrium time for fresh cocoons was 12 h, and the equilibrium time for dry cocoons was 6 h.

[0057] 3) Then, a part was taken from each of the front, middle, and rear parts of the cocoon samples, cut into small particles of 1.5 mm × 1.5 mm, mixed together, and stored in a desiccator with a sample bottle for later measurement.

[0058] 4) Use an isotope ratio mass spectrometer (IRMS) of model MAT253 to measure the hydrogen and oxygen isotope ratios of the samples. The samples are wrapped in silver cups (3.3 mm x 5 mm), enter the elemental analyzer through an automatic sampler, and use H2 and CO as reference gases. The temperature of the combustion furnace is 1380 °C; the temperature of the chromatographic column is 80 °C; the helium purge flow rate is 180 mL / min. After separation in a constant-temperature chromatographic column and dilution with helium, it enters the isotope ratio mass spectrometer for detection: Standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δ 18 O = 8.57‰) are used to correct the test results of the samples. To ensure the accuracy of the test results, 1 standard sample is inserted every 12 samples, and each sample is repeatedly measured 3 times and the average value is taken.

[0059] 5) Calculate according to the calculation formula: δ = (R 样品 / R 标准 -1) × 1000.

[0060] Comparative Example 1 (selecting the same samples as in Example 1, but without moisture absorption and equilibrium)

[0061] 1) Perform decontamination treatment on the surfaces of the collected 24 fresh cocoons and 23 dry cocoons in Zhejiang. Wash the surfaces of the cocoons 3 times with deionized water to remove soil, impurities, and other pollutants that may affect stable isotope analysis.

[0062] 2) Then, 10 samples were selected from the collected 24 fresh cocoons and 23 dry cocoons in Zhejiang and dried in an oven at 60 °C for 6 h.

[0063] 3) Then, a part was taken from each of the front, middle, and rear parts of the cocoon samples, cut into small particles of 1.5 mm × 1.5 mm, mixed together, and stored in a desiccator with a sample bottle for later measurement.

[0064] 4) The hydrogen and oxygen isotope ratios of the samples were determined using an isotope ratio mass spectrometer (IRMS) of model MAT253. The samples were wrapped in silver cups (3.3 mm x 5 mm), entered the elemental analyzer through an auto-sampler, and used H2 and CO as reference gases. The combustion furnace temperature was 1380 °C; the chromatographic column temperature was 80 °C; the helium purge flow rate was 180 mL / min. After separation in the constant-temperature chromatographic column and dilution with helium, they entered the isotope ratio mass spectrometer for detection: Standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δ 18 O = 8.57‰) were used to correct the test results of the samples. To ensure the accuracy of the test results, 1 standard sample was inserted every 12 samples, and each sample was repeatedly measured 3 times and the average value was taken.

[0065] 5) Calculate according to the calculation formula: δ = (R 样品 / R 标准 -1) × 1000.

[0066] Comparative Example 2 (selecting the same samples as in Example 2, but without moisture absorption and equilibrium)

[0067] 1) The surfaces of the collected fresh cocoons of Henan 24 and dry cocoons of Henan 23 were decontaminated, and the surfaces of the cocoons were washed 3 times with deionized water to remove soil, impurities and other pollutants that may affect stable isotope analysis.

[0068] 2) Then, 10 samples were selected from the collected fresh cocoons of Henan 24 and dry cocoons of Henan 23 and dried in an oven at 70 °C for 8 h.

[0069] 3) Then, a part of each of the front, middle and rear parts of the cocoon samples was cut into small particles of 2 mm × 2 mm, mixed together, and then stored in a sample bottle in a desiccator for testing.

[0070] 4) The hydrogen and oxygen isotope ratios of the samples were determined using an isotope ratio mass spectrometer (IRMS) of model MAT253. The samples were wrapped in silver cups (3.3 mm x 5 mm), entered the elemental analyzer through an auto-sampler, and used H2 and CO as reference gases. The combustion furnace temperature was 1380 °C; the chromatographic column temperature was 80 °C; the helium purge flow rate was 180 mL / min. After separation in the constant-temperature chromatographic column and dilution with helium, they entered the isotope ratio mass spectrometer for detection: Standard samples IAEA-CH-7 (δH = -100.3‰) and USGS42 (δ 18 O = 8.57‰) were used to correct the test results of the samples. To ensure the accuracy of the test results, 1 standard sample was inserted every 12 samples, and each sample was repeatedly measured 3 times and the average value was taken.

[0071] 5) Calculate according to the calculation formula: δ = (R样品 / R 标准 -1) × 1000。

[0072] Result analysis:

[0073] The isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) of fresh cocoons and dry cocoons in Example 1 are as shown Figure 1 in; The isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) of fresh cocoons and dry cocoons in Example 2 are as shown Figure 2 in; The isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) of fresh cocoons and dry cocoons in Example 3 are as shown Figure 3 in; The isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) of fresh cocoons and dry cocoons in Example 4 are as shown Figure 4 in; The isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) of fresh cocoons and dry cocoons in Comparative Example 1 are as shown Figure 5 in; The isotope ratio data graphs of hydrogen (δ 2 H) and oxygen (δ18O) of fresh cocoons and dry cocoons in Comparative Example 2 are as shown Figure 6 in.

[0074] It can be clearly seen from the results shown Figures 1-6 that there are significant differences in the hydrogen and oxygen stable isotopes of silkworm cocoons from different regions. The δ 2 H of the hydrogen isotope ratio of fresh cocoons is generally negatively biased, and the δ18O of the oxygen isotope ratio is generally positively biased. The δ 2 H of the hydrogen isotope ratio of dry cocoons is more positively biased compared to the δ 2 H of the hydrogen isotope ratio of fresh cocoons, while the δ18O of the oxygen isotope ratio of dry cocoons is more negatively biased compared to the δ18O of the oxygen isotope ratio of fresh cocoons. Moreover, it can be seen that the samples in Comparative Examples 1 - 2 were not subjected to moisture absorption equilibrium, which would lead to large fluctuations in the δ 2 H and δ18O data, and there is no obvious difference between the data of fresh cocoons and dry cocoons. Thus, it can be proved that the method of the present invention can distinguish and identify fresh cocoons and dry cocoons, and the identification result has high accuracy.

[0075] The raw materials and equipment used in the present invention, unless otherwise specified, are all common raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0076] The above are only the preferred embodiments of the present invention, and do not impose any limitations on the present invention. Any simple modifications, changes, and equivalent transformations made to the above embodiments according to the technical essence of the present invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology, characterized in that: The steps include: 1) Decontamination treatment is performed on the surfaces of the collected fresh cocoon samples and the dried cocoon samples; 2) then pre-drying the fresh cocoon samples and the dried cocoon samples, and placing the dried samples in a standard atmosphere environment for moisture absorption equilibrium; 3) crushing the fresh cocoon samples and the dry cocoon samples that have reached moisture absorption equilibrium into fine particles for testing; 4) Use an isotope ratio mass spectrometer to measure the isotope ratio of hydrogen and oxygen in the sample, and then calculate the δ value according to the calculation formula: δ=(R 样品 / R 标准 -1)×1000; Where δ represents the difference between the isotope ratio of the sample and the isotope ratio of the internationally recognized standard, in ‰; R 样品 is the isotope ratio of heavy elements to light elements in the sample; R 标准 It is the isotope ratio of heavy elements to light elements in internationally recognized standards; 5) Identification of fresh and dried cocoons based on δ values: δ of the hydrogen isotope ratio of dried cocoons 2 The δ value of the hydrogen isotope ratio of H to fresh cocoons 2 H is positive, while the δ18O of the oxygen isotope value ratio of dry cocoons is negative compared with that of fresh cocoons.

2. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1, characterized in that: The decontamination treatment includes: using deionized water to clean the surface of the silk cocoon to remove pollutants including dirt and impurities that affect stable isotope analysis.

3. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1 or 2, characterized in that: At least 10 samples should be collected from fresh cocoon samples and dried cocoon samples respectively, and each sample should include the front, middle and back parts of the cocoon to ensure the comprehensiveness of the extracted data.

4. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1, characterized in that: The drying temperature is 60-80° C. and the drying time is 1-2 hours.

5. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1 or 4, characterized in that: The time for moisture absorption equilibrium in the standard atmosphere is 8-12 hours for fresh cocoons and 4-6 hours for dry cocoons.

6. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1 or 4, characterized in that: The size of the pulverized particles should be within 3 mm × 3 mm.

7. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1, characterized in that: The model of the isotope ratio mass spectrometer is MAT253.

8. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1 or 7, characterized in that: During use of the isotope ratio mass spectrometer, the sample to be tested needs to be wrapped in a silver cup, and H2 and CO are used as reference gases. The combustion furnace temperature is 1300-1400°C, the chromatographic column temperature is 70-80°C, and the helium purge flow rate is 150-200mL / min.

9. A method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1 or 7, characterized in that: During use of the isotope ratio mass spectrometer, standard materials IAEA-CH-7 and USGS42 are selected to calibrate the sample test results.

10. The method for identifying fresh cocoons and dried cocoons based on stable isotope technology as claimed in claim 1, characterized in that: δ 2 H and δ 18 Relative standard R of O 标准 For VSMOW.

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