Mutton origin tracing method based on isotope ratio analysis

Abstract

The invention discloses a mutton origin traceability method based on isotope ratio analysis, which comprises the following steps: taking a standard mutton sample of a known origin, performing freeze drying and grinding treatment, and determining the isotope ratio of carbon, nitrogen and strontium and the content of trace elements such as strontium, iron, zinc, selenium and calcium in the sample; establishing three key matching indexes according to the determination result, namely a ratio of carbon isotope to iron / zinc, a ratio of nitrogen isotope to selenium / calcium and a ratio of strontium isotope to strontium content, and obtaining a matching feature vector of the standard sample; after a to-be-detected sample is subjected to same treatment and analysis, whether the to-be-detected sample and the standard sample are in the same origin area or not is judged by calculating the standardized Euclidean distance of matching feature vectors; according to the method, isotope and trace element indexes are combined, the defect that the discrimination degree of a single index is limited is overcome, and a new technical scheme is provided for tracing of agricultural and sideline products.

Description

Technical Field

[0001] The present invention relates to the technical field of agricultural and sideline product traceability, and in particular to a method for tracing the origin of mutton based on isotope ratio analysis. Background Art

[0002] At present, the commonly used methods for tracing the origin of mutton mainly include single isotope ratio analysis and trace element content analysis. Among them, the isotope ratio analysis method mainly judges the origin of mutton based on the differences in isotope composition caused by environmental factors in different regions (such as water, soil, vegetation, etc.), but this method is easily affected by the feeding method, and the discrimination of single isotope indicators is limited. The trace element content analysis method determines the origin by measuring the content of characteristic elements in mutton, but the trace element content is easily affected by human factors such as feed additives, which reduces the reliability of the traceability results.

[0003] Therefore, there is an urgent need to develop a new method for tracing the origin of mutton that can effectively overcome the above problems. Summary of the invention

[0004] The purpose of the present invention is to solve the problems existing in the single isotope ratio or trace element content analysis method in the prior art, and to achieve the purpose of accurately tracing the origin of mutton by utilizing the correlation ratio analysis of isotope ratio and trace element content based on the characteristics of biological metabolic network.

[0005] In order to achieve the above-mentioned purpose of the present invention, the present invention adopts the following technical solutions:

[0006] A method for tracing the origin of mutton based on isotope ratio analysis, the method comprising the following steps:

[0007] Step S1, freeze-drying and grinding a standard sample into powder, wherein the standard sample is a mutton sample of known origin, and determining the isotope ratio and trace element content in the standard sample.

[0008] This step ensures the accuracy and repeatability of the measurement results through a strictly controlled sample processing process; the standard sample is taken from the muscle tissue of the hind leg of a sheep, freeze-dried at -80°C for 48 hours, and the dried sample is ground to 100 mesh and divided into two equal parts, A and B. Part A is used for isotope ratio determination, and part B is used for trace element content determination; the sampling method avoids cross contamination and ensures the independence of the determination of various indicators.

[0009] The isotope ratio determination includes: carbon isotope ratio δ 13 C. Nitrogen isotope ratio δ 15 N, Sr isotope ratio ( 87 Sr / 86The trace element content includes: strontium Sr, iron Fe, zinc Zn, selenium Se, calcium Ca, the unit is mg / kg, and the selection of these indicators is based on their important role in the biological metabolism process and their indicative significance to the geographical environment.

[0010] Step S2, calculating the key matching index of the standard sample according to the isotope ratio and the trace element content to obtain a first matching feature vector.

[0011] The key matching indexes of the standard sample include: carbon isotope and iron / zinc ratio KRI 1 , Nitrogen isotopes and Selenium / Calcium ratio KRI 2 , and the ratio of strontium isotopes to strontium content KRI 3 ; These three ratio indexes reflect the nutritional metabolic characteristics, physiological metabolic characteristics and geographical environment characteristics of the samples respectively.

[0012]

[0013] Among them, R Fe ,R Zn ,R Se ,R Ca ,R Sr Respectively represent the content of Fe, Zn, Se, Ca, Sr elements, the unit is mg / kg;

[0014] The first matching feature vector is expressed as: V = [KRI 1 ,KRI 2 ,KRI 3 ].

[0015] A plurality of standard samples are collected to obtain a plurality of groups of first matching ratio feature vectors, wherein the number of the standard samples is no less than 50.

[0016] Step S3, obtaining the key ratio index of the sample to be tested and obtaining the second ratio feature vector, wherein the sample to be tested is a mutton sample of unknown origin; calculating the distance between the first ratio feature vector and the second ratio feature vector, and determining whether the sample to be tested and the standard sample are from the same origin based on the distance.

[0017] The sample to be tested is also taken from the muscle tissue of the hind leg of sheep. The same processing method as the standard sample is used to obtain the key ratio index of the sample to be tested, and then the second ratio feature vector is obtained: V′=[KRI 1 ′,KRI 2 ′,KRI 3 ′], where KRI 1 ′, KRI 2 ′, KRI 3′ are the ratio of carbon isotope to iron / zinc, the ratio of nitrogen isotope to selenium / calcium, and the ratio of strontium isotope to strontium content of the tested samples, respectively.

[0018] Compute the normalized Euclidean distance of the matching feature vectors: Among them, KRI i ′ is the i-th ratio index value of the sample to be tested, is the mean value of the i-th ratio index of the standard sample, σ i is the standard deviation of the i-th matching index of the standard sample.

[0019] Based on the standardized Euclidean distance, while considering the similarity of the overall characteristics, the deviation degree of each indicator is also taken into account; if and only if the following conditions are met at the same time, it is determined that the sample to be tested and the standard sample are of the same origin:

[0020] Otherwise, it is determined that the sample to be tested and the standard sample are not of the same origin.

[0021] Furthermore, in the isotope ratio determination, a continuous flow isotope mass spectrometer is used to determine the carbon isotope ratio δ in portion A. 13 C and nitrogen isotope ratios δ 15 N; The strontium isotope ratio in the A portion was determined by thermal ionization mass spectrometry ( 87 Sr / 86 Sr).

[0022] The trace element content determination adopts inductively coupled plasma mass spectrometer ICP-MS to determine the trace element content in the B portion sample.

[0023] Furthermore, the measurement accuracy requirement is:

[0024] Isotope ratio δ 13 C is better than 0.1‰, δ 15 N is better than 0.2‰, ( 87 Sr / 86 Sr) is better than 0.00001;

[0025] The relative standard deviation (RSD) of trace element content was less than 3%, and the detection limit was better than 0.01 mg / kg.

[0026] Furthermore, in the calculation of the key ratio index in step S2, the ratio of strontium isotope to strontium content reflects the geographical environment characteristics, and the strontium content of the standard sample and the sample to be tested must be greater than 0.2 mg / kg;

[0027] When the strontium content of the standard sample is no more than 0.2 mg / kg, the method based on isotope ratio analysis cannot be used to trace the origin of mutton;

[0028] When the strontium content of the standard sample is greater than 0.2 mg / kg, and the strontium content of the sample to be tested is not greater than 0.2 mg / kg, it is determined that the sample to be tested and the standard sample are not of the same origin.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention realizes accurate traceability of the origin of mutton by establishing three key ratio indexes: the ratio of carbon isotope to iron / zinc, the ratio of nitrogen isotope to selenium / calcium, and the ratio of strontium isotope to strontium content, combined with the standardized Euclidean distance determination method. This method not only takes into account the individual indicators of isotopes and trace elements, but more importantly, reveals the intrinsic relationship between them, reflects the complex metabolic network characteristics in organisms, and makes the traceability results more reliable. This method can be extended to the traceability of other agricultural and sideline products, and has a good application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a flow chart of a method for tracing the origin of mutton based on isotope ratio analysis according to an embodiment of the present invention. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention is described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0033] It should be noted that the key ratio index used in the present invention is accurate and difficult to simulate in the traceability of mutton; in the carbon isotope and iron / zinc ratio, the carbon isotope reflects the dietary structure of the sheep, and the ratio of iron to zinc reflects the muscle metabolism characteristics. There is a balance between the two: the grass eaten by the sheep will affect the carbon isotope, and the nutrients in the grass will also affect the absorption ratio of iron and zinc. If you want to simulate it artificially, you must not only adjust the carbon isotope of the feed, but also ensure that the absorption ratio of iron and zinc is just right, which is almost impossible; in the nitrogen isotope and selenium / calcium ratio, the isotope reflects the protein metabolism level The ratio of selenium and calcium reflects the characteristics of nutrient absorption, and this ratio is affected by the entire growth cycle: from nutrient absorption from forage, to metabolism in the body, to the formation of muscle tissue. To simulate this indicator, it is necessary to maintain specific nutritional conditions throughout the growth cycle, and also to consider the issue of bioavailability; in the ratio of strontium isotopes to strontium content, the strontium isotope ratio comes from the local soil and water, and the strontium content is affected by biological enrichment. This ratio reflects the "fingerprint" of the geographical environment. Even if strontium is added artificially, it is difficult to adjust the relationship between the isotope ratio and content at the same time.

[0034] These three indicators are interrelated, not independent. Combining them with the standardized Euclidean distance can effectively solve the problem of tracing the origin of mutton. If you want to falsify it, adjusting one indicator may affect other indicators. It is necessary to control multiple parameters at the same time and consider the complex metabolic network in the body, which is almost impossible to do in actual operation.

[0035] At the same time, these characteristics are formed during the entire growth cycle of the sheep and cannot be achieved by short-term breeding. They require long-term growth in a specific environment, which ensures the stability and authenticity of the characteristics. Therefore, the reliability of the method of the present invention comes from its capture of the complex metabolic network characteristics in the organism, rather than a simple single indicator.

[0036] like Figure 1 As shown, it is a flow chart of a method for tracing the origin of mutton based on isotope ratio analysis disclosed in this embodiment. The method is applied to the origin tracing of Albas mutton, and the method comprises the following steps:

[0037] Step S1, freeze-drying and grinding a standard sample into powder, wherein the standard sample is a mutton sample of known origin, and determining the isotope ratio and trace element content in the standard sample.

[0038] In this example, 100 2-3 year old Albas sheep from the Albas region of Inner Mongolia were selected as the research subjects. Albas sheep is a local breed with strong adaptability and excellent meat quality. Its growth environment is unique and it is mainly distributed in typical grassland areas at an altitude of 1200-1500 meters. All these sheep are raised by grazing and use local natural pasture as the main food source. The sampling time is January 2024 to ensure that the samples are well representative.

[0039] The standard sample is taken from the muscle tissue of the hind leg of a sheep, freeze-dried at -80°C for 48 hours, ground into 100 meshes, and divided into two equal parts, A and B. Part A is used for isotope ratio determination, and part B is used for trace element content determination.

[0040] For the processing of Albas mutton samples, the sampling environment temperature is strictly controlled below 4°C, and the amount of each sample is 50±0.5g; the program temperature is used in the freeze-drying process: -80°C is maintained for the first 12 hours, and then 10°C is increased every 12 hours until the processing is completed in 48 hours. Liquid nitrogen cryogenic grinding technology is used in the grinding process to prevent sample deterioration. The sampling process adopts the quartering method to ensure the uniformity and representativeness of samples A and B. The specific processing parameters are shown in Table 1:

[0041] Table 1 Processing parameters of Albas mutton samples

[0042] step Parameter Control Quality Control Indicators sampling 4℃,50±0.5g Integrity ≥ 98% Freeze drying -80℃→-30℃,48h Moisture content ≤ 2% Grinding Liquid nitrogen temperature, -196℃ Particle size 100 mesh Sampling Four-part method Uniformity RSD≤1%

[0043] The isotope ratio determination includes: carbon isotope ratio δ 13 C. Nitrogen isotope ratio δ 15 N, Sr isotope ratio ( 87 Sr / 86 The trace element content includes: strontium Sr, iron Fe, zinc Zn, selenium Se, and calcium Ca, and the unit is mg / kg.

[0044] The isotope ratio determination was calibrated using international standard materials USGS40 and USGS41, and one standard sample was inserted into every 10 samples for verification. The trace element content was determined by preparing the standard solution using matrix matching, and SRM 1546 (meat standard material) was used as the quality control sample; the specific determination results are shown in Table 2:

[0045] Table 2 Results of the determination of Albas mutton samples (n=100)

[0046]

[0047]

[0048] Step S2, calculating the key matching index of the standard sample according to the isotope ratio and the trace element content to obtain a first matching feature vector.

[0049] The key matching indexes of the standard sample include: carbon isotope and iron / zinc ratio KRI 1 , Nitrogen isotopes and Selenium / Calcium ratio KRI 2 , and the ratio of strontium isotopes to strontium content KRI 3 .

[0050]

[0051] Among them, R Fe ,R Zn ,R Se ,R Ca ,R Sr Respectively represent the content of Fe, Zn, Se, Ca, Sr elements, the unit is mg / kg;

[0052] The first matching feature vector is expressed as: V = [KRI 1 ,KRI 2 ,KRI 3 ].

[0053] A plurality of standard samples are collected to obtain a plurality of groups of first matching ratio feature vectors, wherein the number of the standard samples is no less than 50.

[0054] Based on the measurement data of Albas sheep, we calculated the key ratio index. The results showed that Albas sheep samples from the same production area have similar ratio characteristics; these characteristics are closely related to the local special geographical environment and grazing conditions: carbon isotopes reflect the characteristics of grassland vegetation dominated by C3 plants; the iron-zinc ratio reflects the nutritional intake characteristics related to grazing methods; the selenium-calcium ratio shows the distribution characteristics of trace elements in the local soil; the specific ratio index calculation results are shown in Table 3:

[0055] Table 3 Statistical results of key ratio index of Albas mutton samples (n=100)

[0056] Matching index Calculation formula Mean ± SD 95% Confidence Interval <![CDATA[KRI 1 ]]> <![CDATA[δ 13 C·Fe / Zn]]> -17.5±0.8 [-19.1,-15.9] <![CDATA[KRI 2 ]]> <![CDATA[δ 15 N Se / Ca]]> 0.099±0.008 [0.083,0.115] <![CDATA[KRI 3 ]]> <![CDATA[( 87 Sr / 86 Sr) / Sr·10 3 ]]> 1.58±0.07 [1.44,1.72]

[0057] Step S3, obtaining the key ratio index of the sample to be tested and obtaining the second ratio feature vector, wherein the sample to be tested is a mutton sample of unknown origin; calculating the distance between the first ratio feature vector and the second ratio feature vector, and determining whether the sample to be tested and the standard sample are from the same origin based on the distance.

[0058] The sample to be tested is also taken from the muscle tissue of the hind leg of sheep. The same processing method as the standard sample is used to obtain the key ratio index of the sample to be tested, and then the second ratio feature vector is obtained: v′=[KRI 1 ′,KRI 2 ′,KRI 3 ′], where KRI 1 ′, KRI 2 ′, KRI 3 ′ are the ratio of carbon isotope to iron / zinc, the ratio of nitrogen isotope to selenium / calcium, and the ratio of strontium isotope to strontium content of the tested samples, respectively.

[0059] Compute the normalized Euclidean distance of the matching feature vectors: Among them, KRI i ′ is the i-th ratio index value of the sample to be tested, is the mean value of the i-th ratio index of the standard sample, σ i is the standard deviation of the i-th matching index of the standard sample.

[0060] Based on the standardized Euclidean distance, the sample to be tested and the standard sample are determined to be of the same origin if and only if the following conditions are met at the same time:

[0061] Otherwise, it is determined that the sample to be tested and the standard sample are not of the same origin.

[0062] In practical application, we conducted traceability analysis and verification on 20 mutton samples of unknown origin. These samples included 15 samples from the Albas region and 5 samples from other regions. By measuring the isotope ratios and trace element contents of these samples, their characteristic vectors were calculated and compared with standard samples. The results showed that this method successfully identified all 15 Albas mutton samples with an accuracy of 100%. For the 5 samples from non-Albas regions, their standardized Euclidean distance D values ​​were all greater than 3.5, and the deviations of each item exceeded 2σ, which was obviously different from the characteristic range of Albas mutton samples.

[0063] In the isotope ratio determination, a continuous flow isotope mass spectrometer is used to determine the carbon isotope ratio δ in portion A. 13 C and nitrogen isotope ratios δ 15 N; The strontium isotope ratio in the A portion was determined by thermal ionization mass spectrometry ( 87 Sr / 86 Sr).

[0064] The trace element content determination adopts inductively coupled plasma mass spectrometer ICP-MS to determine the trace element content in the B portion sample.

[0065] In terms of instrument selection, this embodiment uses the Flash 2000 element analyzer and DELTA V Advantage isotope mass spectrometer system of German Thermo Company for C and N isotope determination, with sensitivities of 0.06‰ and 0.08‰ respectively. The Triton mass spectrometer of German Thermo Company is used for Sr isotope determination, with a precision better than 0.00001. Agilent 7700x ICP-MS is used for trace element determination, with a detection limit better than 0.01ppm. All equipment is calibrated and maintained regularly to ensure the accuracy and reliability of the measurement results.

[0066] The measurement accuracy requirement is: isotope ratio δ 13 C is better than 0.1‰, δ 15 N is better than 0.2‰, ( 87 Sr / 86 sr) is better than 0.00001; the relative standard deviation RSD of trace element content is less than 3%, and the detection limit is better than 0.01 mg / kg; in the actual measurement process, a strict quality control system was established for Albas mutton samples; the reliability of the measurement results was ensured through parallel sample analysis, spike recovery test and standard reference material determination.

[0067] In the calculation of the key ratio index in step S2, the ratio of strontium isotope to strontium content reflects the geographical environment characteristics, and the strontium content of the standard sample and the sample to be tested must be greater than 0.2 mg / kg;

[0068] When the strontium content of the standard sample is no more than 0.2 mg / kg, the method based on isotope ratio analysis cannot be used to trace the origin of mutton;

[0069] When the strontium content of the standard sample is greater than 0.2 mg / kg, and the strontium content of the sample to be tested is not greater than 0.2 mg / kg, it is determined that the sample to be tested and the standard sample are not of the same origin.

[0070] To verify the stability of the method, we conducted repeated measurements and long-term stability studies on 100 samples of Albas mutton; the intra-batch relative standard deviation (RSD) of repeated measurements on the same day was between 1.2-2.8%, the inter-batch RSD of repeated measurements on the same day was between 2.1-4.2%, and the RSD of the 3-month long-term stability test was less than 5%, indicating that the method has good stability and repeatability.

[0071] In order to improve the anti-interference ability of the method, we designed a feeding method interference experiment; 30 Albas sheep were selected and fed in three ways: pure grazing, semi-housed feeding and full housed feeding for 3 months; the results showed that although different feeding methods would cause certain fluctuations in KRI1 and KRI2 (the change rates were 3.2-7.8% and 2.8-6.5% respectively), KRI3 based on geographical environment characteristics remained relatively stable, with a change rate of only 1.5-2.1%; this shows that this method has a strong anti-interference ability. The specific data are shown in Table 4:

[0072] Table 4 Effects of different feeding methods on traceability indicators

[0073]

[0074] This method has been applied in a certain autonomous region quality supervision and inspection institute for one year, and has completed the origin identification of more than 500 mutton samples; the actual application results show that the overall accuracy of the method reached 96.6%, the average detection time was 4.5 hours, the cost of a single sample detection was about 850 yuan, and the daily detection capacity could reach 12 samples / day; compared with the existing single isotope method, trace element method and DNA molecular labeling method, this method has obvious advantages in accuracy, anti-interference ability, method stability and other aspects.

[0075] The innovation of this method is mainly reflected in the establishment of a new ratio index system; KRI1 reflects nutritional metabolic characteristics, with a coefficient of variation of less than 5%; KRI2 reflects physiological metabolic characteristics, with a coefficient of variation of less than 6%; KRI3 reflects geographical environmental characteristics, with a coefficient of variation of less than 3%. In particular, it was found that the fluctuation range of KRI3 values ​​of samples from the same production area is less than 5%, while the difference in KRI3 values ​​of samples from different production areas is greater than 15%, which provides a reliable technical basis for tracing the origin of mutton.

[0076] The method was tested on samples of different ages (6 months to over 3 years old) and different seasons, and its wide applicability was verified. The results showed that the discrimination accuracy was maintained above 96% under various conditions. The discrimination accuracy of mature samples (1-2 years old) was the highest, reaching 97.2%. Among the seasonal factors, the discrimination accuracy of summer green grass period was the highest, also reaching 97.2%.

[0077] The application of this method provides strong technical support for the brand protection of Albas mutton, which increases the price of branded mutton by 15-20%, and the detection rate of counterfeit products reaches 98.5%, which significantly improves market confidence and generates considerable economic benefits. The verification results of these systems fully prove the reliability, practicality and innovation of the method of the present invention, and provide strong technical support for the protection of geographical indication agricultural products in my country.

[0078] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for tracing the origin of mutton based on isotope ratio analysis, characterized in that: The method comprises the following steps: Step S1, taking a standard sample, freeze-drying it, and grinding it into powder, wherein the standard sample is a mutton sample of known origin, and determining the isotope ratio and trace element content in the standard sample; The standard sample is taken from the muscle tissue of the hind leg of sheep, freeze-dried at -80°C for 48 hours, and the dried sample is ground into 100 mesh and divided into two equal parts, A and B. Part A is used for isotope ratio determination, and part B is used for trace element content determination; The isotope ratio determination includes: carbon isotope ratio δ 13 C. Nitrogen isotope ratio δ 15 N, Sr isotope ratio ( 87 Sr / 86 The trace element content includes: strontium Sr, iron Fe, zinc Zn, selenium Se, calcium Ca, the unit is mg / kg; Step S2, calculating the key matching index of the standard sample according to the isotope ratio and the trace element content to obtain a first matching feature vector; The key ratio indexes of the standard sample include: carbon isotope and iron / zinc ratio KRI1, nitrogen isotope and selenium / calcium ratio KRI2, and strontium isotope and strontium content ratio KRI3; Among them, R Fe ,R Zn ,R Se ,R Ca ,R Sr Respectively represent the content of Fe, Zn, Se, Ca, Sr elements, the unit is mg / kg; The first matching feature vector is expressed as: V = [KRI1, KRI2, KRI3]; Collecting a plurality of standard samples to obtain a plurality of groups of first matching ratio feature vectors, wherein the number of the standard samples is no less than 50; Step S3, obtaining a key ratio index of the sample to be tested, and obtaining a second ratio feature vector, wherein the sample to be tested is a mutton sample of unknown origin; calculating the distance between the first ratio feature vector and the second ratio feature vector, and determining whether the sample to be tested and the standard sample are of the same origin based on the distance; The sample to be tested is also taken from the muscle tissue of the hind leg of a sheep, and the key ratio index of the sample to be tested is obtained by the same processing method as the standard sample, and then the second ratio characteristic vector is obtained: V′=[KRI1′, KRI2′, KRI3′], wherein KRI1′, KRI2′, KRI3′ are the ratio of carbon isotope to iron / zinc, the ratio of nitrogen isotope to selenium / calcium, and the ratio of strontium isotope to strontium content of the sample to be tested, respectively; Compute the normalized Euclidean distance of the matching feature vectors: Among them, KRI i ′ is the i-th ratio index value of the sample to be tested, is the mean value of the i-th ratio index of the standard sample, σ i is the standard deviation of the i-th matching index of the standard sample; Based on the standardized Euclidean distance, the sample to be tested and the standard sample are determined to be of the same origin if and only if the following conditions are met at the same time: Otherwise, it is determined that the sample to be tested and the standard sample are not of the same origin.

2. The method for tracing the origin of mutton based on isotope ratio analysis according to claim 1, characterized in that: In the isotope ratio determination, a continuous flow isotope mass spectrometer is used to determine the carbon isotope ratio δ in portion A. 13 C and nitrogen isotope ratios δ 15 N; The strontium isotope ratio in the A portion was determined by thermal ionization mass spectrometry ( 87 Sr / 86 Sr); The trace element content determination adopts inductively coupled plasma mass spectrometer ICP-MS to determine the trace element content in the B portion sample.

3. The method for tracing the origin of mutton based on isotope ratio analysis according to claim 2, characterized in that: The measurement accuracy requirements are: Isotope ratio δ 13 C is better than 0.1‰, δ 15 N is better than 0.2‰, ( 87 Sr / 86 Sr) is better than 0.00001; The relative standard deviation (RSD) of trace element content was less than 3%, and the detection limit was better than 0.01 mg / kg.

4. The method for tracing the origin of mutton based on isotope ratio analysis according to claim 1, characterized in that: In the calculation of the key ratio index in step S2, the ratio of strontium isotope to strontium content reflects the geographical environment characteristics, and the strontium content of the standard sample and the sample to be tested must be greater than 0.2 mg / kg; When the strontium content of the standard sample is no more than 0.2 mg / kg, the method based on isotope ratio analysis cannot be used to trace the origin of mutton; When the strontium content of the standard sample is greater than 0.2 mg / kg, and the strontium content of the sample to be tested is not greater than 0.2 mg / kg, it is determined that the sample to be tested and the standard sample are not of the same origin.

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