A method for tracing the origin of mutton based on isotope ratio analysis

Abstract

The invention discloses a method for tracing the origin of mutton based on isotope ratio analysis. The method takes a standard mutton sample of known origin, adopts freeze-drying and grinding treatment, and measures the carbon, nitrogen and strontium isotope ratios and the contents of trace elements such as strontium, iron, zinc, selenium and calcium in the sample; three key ratio indices are established according to the measurement results: 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, to obtain a ratio characteristic vector of the standard sample; after the sample to be tested is subjected to the same treatment and analysis, the standardized Euclidean distance of the ratio characteristic vector is calculated to determine whether it has the same origin as the standard sample; the method of the invention combines isotope and trace element indicators, overcomes the defect of limited discrimination of a single indicator, and provides a new technical solution for tracing the origin 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 determines 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 existing technology of single isotope ratio or trace element content analysis method. Based on the characteristics of biological metabolic network, the correlation ratio analysis of isotope ratio and trace element content is used to achieve the purpose of accurate traceability of mutton production.

[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-dry a standard sample and grind it into powder. The standard sample is a mutton sample of known origin, and the isotope ratio and trace element content in the standard sample are determined.

[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 sheep hind leg, 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, strontium isotope ratio ( 87 Sr / 86The trace element content includes: strontium Sr, iron Fe, zinc Zn, selenium Se, calcium Ca content, the unit is mg / kg, these indicators are selected based on their important role in the biological metabolism process and their indicative significance to the geographical environment.

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

[0011] The key ratio indices 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; these three ratio indices respectively reflect the nutritional metabolic characteristics, physiological metabolic characteristics and geographical environment characteristics of the sample.

[0012]

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

[0014] The first matching ratio feature vector is expressed as: V=[KRI1, KRI2, KRI3].

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

[0016] Step S3, obtain the key ratio index of the sample to be tested and obtain a second ratio feature vector, where the sample to be tested is a mutton sample of unknown origin; calculate the distance between the first ratio feature vector and the second ratio feature vector, and determine whether the sample to be tested and the standard sample are of 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 a 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 characteristic vector is obtained: V′=[KRI1′, KRI2′, KRI3′], wherein KRI1′, KRI2′, and KRI3′ are the carbon isotope and iron / zinc ratios, nitrogen isotope and selenium / calcium ratios, and strontium isotope and strontium content ratios of the sample to be tested, 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, σi is the standard deviation of the i-th ratio 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; the sample to be tested and the reference sample are determined to be of the same origin if and only if the following conditions are simultaneously met:

[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; Sr isotope ratios in fraction A were determined using thermal ionization mass spectrometry ( 87 Sr / 86 Sr).

[0022] The trace element content in the B sample was determined using an inductively coupled plasma mass spectrometer (ICP-MS).

[0023] Furthermore, the measurement accuracy requirements are:

[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 the 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] This study establishes three key ratio indices: the ratio of carbon isotopes to iron / zinc, the ratio of nitrogen isotopes to selenium / calcium, and the ratio of strontium isotopes to strontium content. Combined with a standardized Euclidean distance method, this method accurately traces the origin of mutton. This method not only considers individual isotope and trace element indicators but, more importantly, reveals the inherent connections between them, reflecting the complex metabolic networks within organisms. This makes traceability results more reliable and can be extended to trace the origin of other agricultural and sideline products, demonstrating its promising application prospects. 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 in an embodiment of the present invention. DETAILED DESCRIPTION

[0032] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention are described clearly and completely below. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts 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 iron and zinc ratio 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 artificially simulate it, 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 level of protein metabolism. 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 the issue of bioavailability must also be considered; in the ratio of strontium isotopes to strontium content, the strontium isotope ratio comes from 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 organism. This 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 through 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 FIG. 1 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 includes the following steps:

[0037] Step S1: freeze-dry a standard sample and grind it into powder. The standard sample is a mutton sample of known origin, and the isotope ratio and trace element content in the standard sample are determined.

[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 are a local breed with strong adaptability and excellent meat quality. They thrive in a unique environment, primarily distributed in typical grassland areas at altitudes of 1200-1500 meters. All of these sheep were raised by grazing, using local natural forage as their primary diet. Sampling was collected in January 2024 to ensure the sample's representativeness.

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

[0040] For the processing of Albas lamb samples, the sampling environment temperature was strictly controlled below 4°C, and the sample size for each sample was 50±0.5g. A programmed temperature ramp was used during the freeze-drying process: -80°C was maintained for the first 12 hours, and then the temperature was increased by 10°C every 12 hours until the 48-hour processing was completed. Liquid nitrogen cryogenic grinding technology was used during the grinding process to prevent sample deterioration. The quartering method was used during the sampling process to ensure the uniformity and representativeness of the two 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, strontium isotope ratio ( 87 Sr / 86The trace element content includes: strontium Sr, iron Fe, zinc Zn, selenium Se, and calcium Ca, and the unit is mg / kg.

[0044] Isotope ratio determinations were calibrated using international reference materials USGS40 and USGS41, with one reference sample inserted for every 10 samples. Trace element content was determined using a matrix-matched standard solution, with SRM 1546 (meat reference material) used as a quality control sample. The specific measurement results are shown in Table 2:

[0045] Table 2 Measurement results of Albas mutton samples (n=100)

[0046]

[0047]

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

[0049] 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.

[0050]

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

[0052] The first matching ratio feature vector is expressed as: V=[KRI1, KRI2, KRI3].

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

[0054] Based on the data from the Albas sheep, we calculated key ratio indices. The results showed that Albas sheep samples from the same production area had similar ratio characteristics. These characteristics are closely related to the unique local 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; and 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[KRI1]]> <![CDATA[δ 13 C·Fe / Zn]]> -17.5±0.8 [-19.1,-15.9] <![CDATA[KRI2]]> <![CDATA[δ 15 N Se / Ca]]> 0.099±0.008 [0.083,0.115] <![CDATA[KRI3]]> <![CDATA[( 87 Sr / 86 Sr) / Sr·10 3 ]]> 1.58±0.07 [1.44,1.72]

[0057] Step S3, obtain the key ratio index of the sample to be tested and obtain a second ratio feature vector, where the sample to be tested is a mutton sample of unknown origin; calculate the distance between the first ratio feature vector and the second ratio feature vector, and determine whether the sample to be tested and the standard sample are of 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 a 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 characteristic vector is obtained: v′=[KRI1′, KRI2′, KRI3′], wherein KRI1′, KRI2′, and KRI3′ are the carbon isotope and iron / zinc ratios, nitrogen isotope and selenium / calcium ratios, and strontium isotope and strontium content ratios of the sample to be tested, 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 ratio 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 simultaneously met:

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

[0062] In practical applications, we conducted traceability analysis and verification on 20 mutton samples of unknown origin. These samples included 15 from the Albas region and 5 from other regions. By measuring the isotope ratios and trace element contents of these samples, their characteristic vectors were calculated and compared with those of standard samples. The results showed that this method successfully identified all 15 Albas mutton samples with 100% accuracy. For the five non-Albas samples, their standardized Euclidean distance (D) values were all greater than 3.5, and all deviations exceeded 2σ, indicating that they were clearly distinct 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; Sr isotope ratios in fraction A were determined using thermal ionization mass spectrometry (87 Sr / 86 Sr).

[0064] The trace element content in the B sample was determined using an inductively coupled plasma mass spectrometer (ICP-MS).

[0065] In terms of instrument selection, this example employed a Thermo Fisher Scientific Flash 2000 elemental analyzer coupled with a DELTA V Advantage isotope mass spectrometer for C and N isotope determination, achieving sensitivities of 0.06‰ and 0.08‰, respectively. A Thermo Fisher Scientific Triton mass spectrometer was used for Sr isotope determination, achieving a precision better than 0.00001. Trace element determination was performed using an Agilent 7700x ICP-MS, achieving detection limits better than 0.01 ppm. All equipment was regularly calibrated and maintained 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 The relative standard deviation (RSD) of trace element content was less than 3%, and the detection limit was better than 0.01 mg / kg. During the actual determination process, a strict quality control system was established for Albas mutton samples. The reliability of the determination 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 Albas mutton samples; 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] To test the method's ability to resist interference, we designed a feeding experiment involving 30 Albas sheep, each reared for three months using pure grazing, semi-housing, and full housing methods. The results showed that while different feeding methods led to some fluctuations in KRI1 and KRI2 (with rates of change ranging from 3.2% to 7.8% and 2.8% to 6.5%, respectively), KRI3, which is based on geographical characteristics, remained relatively stable, with a rate of change of only 1.5% to 2.1%. This demonstrates the method's strong ability to resist interference. See Table 4 for specific data.

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

[0073]

[0074] This method has been used in a certain autonomous region's 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 lies primarily in the establishment of a novel 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%; and KRI3 reflects geographical environmental characteristics, with a coefficient of variation of less than 3%. In particular, the method discovered a significant pattern: while KRI3 values for samples from the same production area fluctuate within a range of less than 5%, those from different production areas vary by greater than 15%, providing a reliable technical basis for tracing the origin of mutton.

[0076] The method's broad applicability was verified by testing samples of varying ages (6 months to over 3 years old) and seasons. Results showed that the accuracy remained above 96% across all conditions. The highest accuracy, at 97.2%, was achieved for mature samples (1-2 years old). Among seasonal factors, the highest accuracy was achieved during the summer grassy period, also reaching 97.2%.

[0077] The application of this method provides strong technical support for brand protection of Albas lamb, increasing the price of branded lamb by 15-20% and achieving a 98.5% detection rate for counterfeit products, significantly boosting market confidence and generating substantial economic benefits. These system validation results fully demonstrate the reliability, practicality, and innovative nature of the method, providing 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 then 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 was taken from the muscle tissue of the hind leg of sheep, freeze-dried at -80°C for 48 hours, ground into 100 mesh, and divided into two equal parts, A and B. Part A was used for isotope ratio determination, and part B was used for trace element content determination; The isotope ratio determination includes: carbon isotope ratio δ 13 C. Nitrogen isotope ratio δ 15 N, strontium isotope ratio ( 87 Sr / 86 The trace element content includes: strontium Sr, iron Fe, zinc Zn, selenium Se, calcium Ca content, the unit is mg / kg; Step S2, calculating the key ratio index of the standard sample according to the isotope ratio and the trace element content to obtain a first ratio characteristic vector; The key ratio indices of the standard sample include: the ratio of carbon isotope to iron / zinc KRI1, the ratio of nitrogen isotope to selenium / calcium KRI2, and the ratio of strontium isotope to strontium content KRI3; Among them, R Fe ,R Zn ,R Se ,R Ca ,R Sr Respectively represent the content of Fe, Zn, Se, Ca, and Sr elements, the unit is mg / kg; The first matching ratio feature vector is expressed as: V = [KRI1, KRI2, KRI3]; Collecting multiple standard samples to obtain multiple groups of first 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 to obtain 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 have the same origin based on the distance; The test sample is also taken from the muscle tissue of the hind leg of a sheep. The same processing method as the standard sample is used to obtain the key ratio index of the test sample, and then obtain the second ratio characteristic vector: V′=[KRI1′, KRI2′, KRI3′], wherein KRI1′, KRI2′, and KRI3′ are the carbon isotope to iron / zinc ratio, nitrogen isotope to selenium / calcium ratio, and strontium isotope to strontium content ratio of the test sample, 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 ratio 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 simultaneously met: 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; Sr isotope ratios in fraction A were determined using thermal ionization mass spectrometry ( 87 Sr / 86 Sr); The trace element content in the B sample was determined using an inductively coupled plasma mass spectrometer (ICP-MS).

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 the 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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