Method for identifying grassland grazing sheep and grassland grazing mutton and application thereof

Abstract

The application provides a grassland grazing sheep and a grassland grazing sheep meat identification method and application thereof, and belongs to the technical field of food authenticity detection. 13 C, and delta 15 N stable isotope values are detected, and it can be determined whether the sheep belongs to the grassland grazing sheep. 13 The grassland grazing sheep meat identification method provided by the application comprises the following steps: detecting the delta 15 C, delta 13 N stable isotope values, the content of fatty acids, flavor amino acids and total amino acids in the sheep meat; if the following conditions are met simultaneously: delta 15 C≤-19.0‰, delta N≥4.0‰, the ratio of omega-6 to omega-3 in the fatty acids is less than or equal to 2.5, and the ratio of flavor amino acids to total amino acids is greater than or equal to 50%, the sheep meat is determined as the grassland grazing sheep meat. The identification method highlights the essential characteristics of the grassland grazing sheep meat through the joint of multiple indexes, and can eliminate the influence of factors such as breeds, regions, ages and human interference, and the identification accuracy reaches 100%.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of food authenticity detection, and particularly relates to a method for identifying grassland grazing sheep and grassland grazing mutton and application thereof. BACKGROUND

[0002] In the development process of modern animal husbandry, consumers' attention to the quality and origin of mutton is increasing. Sheep meat, as an important meat product, is mainly produced by two modes: indoor feeding and grazing. Compared with indoor feeding mutton, grassland grazing mutton is favored in the market due to its unique flavor, high protein content, low fat content, and rich vitamins and minerals, and can often obtain a higher price, which is also in line with the current consumer trend of pursuing healthy and natural food. However, it is difficult to accurately distinguish between the two by relying on traditional sensory identification methods, such as observing the color and texture of the meat, and touching the meat quality, because the appearance of grassland grazing mutton and indoor feeding mutton is very similar.

[0003] To effectively solve this problem, a series of methods for identifying grassland grazing mutton and indoor feeding mutton have been proposed. In terms of traditional identification methods, domestic and foreign researches have focused on the analysis of conventional physicochemical indicators of meat products. Some studies have measured and compared the color, pH value, shear force, and cooking loss of grazing and indoor feeding mutton. It has been found that the color of grassland grazing mutton is usually brighter, and the pH value is relatively stable, which may be closely related to the large amount of exercise of grazing sheep and the consumption of natural pasture. However, these traditional methods have obvious limitations and are easily affected by various factors, such as the breed, age, and slight differences in the feeding environment of sheep, which can cause fluctuations in physicochemical indicators, thereby affecting the accuracy and reliability of identification. At the same time, instrument analysis technology has also been widely used in the field of sheep meat identification. For example, by analyzing the spectral characteristics of sheep meat in the near-infrared band, the chemical composition and structural information of the meat can be obtained. However, this technology has high requirements for sample pretreatment, and the spectral data analysis process is complex and easily affected by environmental factors, such as changes in temperature and humidity, which can cause deviations in spectral data and affect the identification results. In summary, the existing methods for identifying grassland grazing mutton have certain shortcomings in accuracy, reliability, convenience, and cost-effectiveness, and cannot meet the urgent need for rapid and accurate identification of grassland grazing mutton in the market. Therefore, it is an urgent problem in the field to develop a more accurate, reliable, efficient, and cost-effective method for identifying grassland grazing mutton. SUMMARY

[0004] To solve the problems in the prior art, the first purpose of the present application is to provide a grassland grazing sheep and a method for identifying grassland grazing mutton, with an accuracy rate of 100%.

[0005] The second object of the present application is to provide the application of the above method in the quality monitoring of mutton.

[0006] In order to achieve the above-mentioned objects, the present application provides the following technical solutions.

[0007] The present application provides a method for identifying grassland grazing sheep, comprising the following steps:

[0008] Detecting the stable isotope values of delta 13 C, delta 15 N in the neck hair of sheep; if the following conditions are met simultaneously: delta 13 C≤-19.0‰, delta 15 N≥4.0‰, the sheep is determined to be a grassland grazing sheep.

[0009] Preferably, the method for detecting the stable isotope values of delta 13 C, delta 15 N in the neck hair of sheep comprises the following steps: cutting and grinding the neck hair of sheep, using Soxhlet extraction method with petroleum ether as the solvent, degreasing and air-drying to obtain the sample to be tested; and determining the sample to be tested by using a stable isotope mass spectrometer.

[0010] The present application provides a method for identifying grassland grazing mutton, comprising the following steps:

[0011] Detecting the stable isotope values of delta 13 C, delta 15 N, the contents of fatty acids, flavor amino acids and total amino acids in the mutton; if the following conditions are met simultaneously: delta 13 C≤-19.0‰, delta 15 N≥4.0‰, the ratio of omega-6 to omega-3 in fatty acids≤2.5, and the ratio of flavor amino acids to total amino acids≥50%, the mutton is determined to be grassland grazing mutton.

[0012] Preferably, the method for detecting the stable isotope values of delta 13 C, delta 15 N in the mutton comprises the following steps: removing fat from the mutton, stirring and crushing, freeze-drying and grinding, using Soxhlet extraction method with petroleum ether as the solvent, degreasing and air-drying to obtain the sample to be tested; and determining the sample to be tested by using a stable isotope mass spectrometer.

[0013] Preferably, the amount of omega-6 in the fatty acids is the total amount of linoleic acid, gamma-linolenic acid, eicosatrienoic acid and arachidonic acid.

[0014] Preferably, the amount of omega-3 in the fatty acids is the total amount of alpha-linolenic acid, DHA and EPA.

[0015] Preferably, the amount of flavor amino acids is the total amount of glutamic acid, aspartic acid, phenylalanine, alanine, glycine and tyrosine.

[0016] Preferably, the total amount of amino acids is the total amount of aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, and arginine.

[0017] Preferably, the grassland-grazed mutton includes grassland-grazed sheep meat or grassland-grazed goat meat.

[0018] This invention also provides the application of the above-mentioned identification method in the quality monitoring of mutton.

[0019] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0020] This invention identifies the neck hair of live sheep from the perspective of stable carbon and nitrogen isotopes. It can be used to assess whether the subject is a pasture-grazing sheep, and the identification accuracy for pasture-grazing sheep reaches 99.2%.

[0021] This invention establishes a precise identification technology for grassland-grazing mutton from multiple perspectives, including carbon and nitrogen stable isotopes, the ω-6 / ω-3 fatty acid ratio, and the proportion of flavor-enhancing amino acids. It highlights the essential characteristics of grassland-grazing mutton and can eliminate the influence of factors such as breed, region, age, and human interference on grassland-grazing mutton, achieving an identification accuracy of 100%. Attached Figure Description

[0022] Figure 1 The correlation between stable C and N isotopes in mutton and stable isotopes in sheep neck hair;

[0023] Figure 2 δ of neck wool from pasture-grazing sheep versus neck wool from stall-fed sheep 13 C value;

[0024] Figure 3 δ of neck wool from pasture-grazing sheep versus neck wool from stall-fed sheep 15 N value;

[0025] Figure 4 δ0.05 of grassland-grazed mutton versus stall-fed mutton 13 C value;

[0026] Figure 5 δ0.05 of grassland-grazed mutton versus stall-fed mutton 15 N value;

[0027] Figure 6 : Distribution of fatty acid ω-6 / ω-3 in grassland-grazed mutton and stall-fed mutton;

[0028] Figure 7 Distribution of flavor amino acids / total amino acids in grazing-fed mutton and stall-fed mutton. Detailed Implementation

[0029] The application provides a method for identifying grassland grazing sheep, comprising the following steps: detecting the stable isotope values of δ 13 C, δ 15 N of the neck hair of the sheep; if the following conditions are met simultaneously: δ 13 C≤-19.0‰, δ 15 N≥4.0‰, the sheep is determined as a grassland grazing sheep. 13 C, δ 15 N of the sheep can be used for identifying the grassland grazing sheep before the sheep are put on the market or slaughtered, and can be used for identifying whether the sheep to be slaughtered is a grassland grazing sheep in advance.

[0030] In the application, the method for detecting the stable isotope values of δ 13 C, δ 15 N of the sheep comprises the following steps: the neck hair of the sheep is cut and ground, Soxhlet extraction is adopted, petroleum ether is used as a solvent, the sample is defatted and dried to obtain a sample to be detected; the sample to be detected is detected by using a stable isotope mass spectrometer. The neck hair of the sheep is preferably cut to 0.5 cm and ground to 100 meshes, the sample is wrapped in filter paper, Soxhlet extraction is adopted, petroleum ether is used as a solvent, the sample is defatted at 60 DEG C for 6 hours, and then naturally dried to obtain the sample to be detected of the stable isotope of the hair.

[0031] The application provides a method for identifying grassland grazing sheep meat, comprising the following steps: detecting the stable isotope values of δ 13 C, δ 15 N of the sheep meat, the contents of fatty acids, flavor amino acids and total amino acids; if the following conditions are met simultaneously: δ 13 C≤-19.0‰, δ 15 N≥4.0‰, the ratio of omega-6 to omega-3 in the fatty acids is less than 2.5, and the ratio of flavor amino acids to total amino acids is greater than 50%, the sheep meat is determined as grassland grazing sheep meat.

[0032] In the application, the method for detecting the stable isotope values of δ 13 C, δ 15The method for determining the N stable isotope value comprises the following steps: removing fat from mutton, stirring, freeze-drying, grinding, using Soxhlet extraction method, using petroleum ether as a solvent, defatting, and air-drying to obtain a sample to be measured; and using a stable isotope mass spectrometer to measure the sample to be measured. The mutton can be front leg meat, and as an optional embodiment, the mutton collected on site is sealed in a ziplock bag and stored at -20 DEG C, and before detection, the frozen mutton is thawed at 4 DEG C, and a sample in a semi-thawed state is taken for detection. As another optional embodiment, the sample on site is directly detected on site. After the mutton to be measured is defatted, the mutton is cut into meat cubes, the mutton is stirred, and vacuum freeze-drying is performed; the conditions of the vacuum freeze-drying can be selected as -70 DEG C freezing for 48 h. The mutton after freeze-drying is crushed and ground to 100 mesh, the sample is wrapped in filter paper, Soxhlet extraction method is used, petroleum ether is used as a solvent, defatting is performed at 60 DEG C for 6 h, and then natural air-drying is performed to obtain a stable isotope sample to be measured.

[0033] In the present application, the instrument determination conditions for measurement by the stable isotope mass spectrometer are as follows: the helium gas purging flow of the sample injector is 200 mL / min, the combustion furnace temperature is 960 DEG C, the reduction furnace temperature is 650 DEG C, and the carrier gas He flow is 90-100 mL / min. The He dilution pressure is 0.6 bar, the CO2 gas pressure is 0.6 bar, and the N2 gas pressure is 1.0 bar. USGS24 (delta 13 CPDB=-16.00 ‰) is used to calibrate the CO2 cylinder, IAEAN (delta 15 Nair=0.4 ‰) is used to calibrate the CO2 cylinder, and the calibrated cylinder is used as a standard.

[0034] In the present application, the content of fatty acids is preferably determined by gas chromatography, and the determination method is preferably according to GB5009.168-2016 'National Food Safety Standard Determination of Fatty Acids in Food'. The method of the present application can detect the content of 37 kinds of fatty acids, and the amount of omega-6 in the fatty acids is the total amount of linoleic acid, gamma-linolenic acid, eicosatrienoic acid and arachidonic acid; the amount of omega-3 in the fatty acids is the total amount of alpha-linolenic acid, DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid).

[0035] In the present application, the amino acid content is preferably determined using an amino acid analyzer, and the determination method is preferably according to GB 5009.124-2016 "Determination of Amino Acids in Food" of "National Food Safety Standard". The method of the present application can detect the content of 16 kinds of hydrolyzed amino acids. The amount of flavor amino acid (FAA) is the total amount of glutamic acid, aspartic acid, phenylalanine, alanine, glycine and tyrosine; the amount of total amino acid (TAA) is the total amount of aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine and arginine.

[0036] In the present application, the grassland grazing sheep meat includes grassland grazing sheep meat or grassland grazing goat meat.

[0037] The present application also provides the application of the above-mentioned identification method in the quality monitoring of sheep meat.

[0038] The technical solutions in the present application will be clearly and completely described below in combination with the embodiments in the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0039] In the following examples, if not specifically stated, all are conventional methods.

[0040] In the following examples, the materials, reagents and the like used, if not specifically stated, can be obtained from commercial channels.

[0041] Example 1

[0042] A method for identifying grassland grazing sheep meat: detecting the values of stable isotopes δ 13 C, δ 15 N, the contents of fatty acids, flavor amino acids and total amino acids in sheep meat; if δ 13 C≤-19.0‰, δ 15 N≥4.0‰, ω-6:ω-3≤2.5 in fatty acids, and the ratio of flavor amino acids to total amino acids≥50%, it is determined as grassland grazing sheep meat.

[0043] The front leg part of sheep meat is taken as the sample for determination of stable isotopes, fatty acids and amino acids. 2.0 kg of front leg sheep meat is collected, and the collected sheep meat is packaged in a self-sealing bag and stored at-20℃. When determination is needed, the frozen sheep meat is placed at room temperature, and the sample is taken for detection when it is in a semi-thawed state.

[0044] δ 13 C, δ 15 N stable isotope value: when detecting mutton, remove the fat part, cut the mutton into 1 cm 3 small meat pieces, use a meat grinder to stir the mutton, transfer it to a surface dish, place the ground sample in a vacuum freeze dryer and freeze dry at-70℃ for 48 h, after freeze drying, crush and grind to 100 mesh using a ball mill, wrap the sample in filter paper, use Soxhlet extraction method, use petroleum ether as solvent, defat at 60℃ for 6 h, then air dry to obtain the stable isotope sample to be tested; use stable isotope mass spectrometer to determine, instrument determination conditions: helium gas purging flow of sample injector is 200 mL / min, combustion furnace temperature is 960℃, reduction furnace temperature is 650℃, carrier gas He flow is 90~100 mL / min. He dilution pressure is 0.6 bar, CO2 reference gas pressure is 0.6 bar, N2 reference gas pressure is 1.0 bar. USGS24 (δ 13 CPDB=-16.00 ‰) is used to calibrate CO2 cylinder, IAEAN (δ 15 Nair=0.4 ‰) is used to calibrate CO2 cylinder, and the calibrated cylinder is used as a standard.

[0045] Detecting fatty acids in mutton: cut the mutton into 1 cm 3small pieces, using a meat grinder to stir the mutton, transfer to a surface dish, place the minced sample in a vacuum freeze dryer -70°C freeze drying for 48 h, after freeze drying, crush and grind to 100 mesh using a ball mill. The determination method is based on GB 5009.168-2016 "National food safety standard Determination of fatty acids in food", the specific process is: take 0.5 g of sample, transfer to a 250 mL flat-bottom flask, accurately add 2.0 mL of glyceryl tridecanoate internal standard solution, add about 200 mg of pyrogallol, add a few zeolites, then add 2 mL of 95% ethanol and 4 mL of water, mix well, add 10 mL of 8.3 mol / L hydrochloric acid solution and mix well, put the flask in a 80°C water bath and hydrolyze for 40 min, after hydrolysis, take out the flask and cool to room temperature. After hydrolysis, add 10 mL of 95% ethanol to the sample, mix well, and transfer the hydrolysis liquid in the flask to a separatory funnel, rinse the flask and plug with 50 mL of ether and petroleum ether (1:1 by volume), pour the washing liquid into the separatory funnel, cover it, shake for 5 min, stand for 10 min, collect the ether layer extract into a 250 mL flask, repeat the extraction 3 times according to the above steps, combine the ether layer extract, concentrate to dryness on a rotary evaporator, and obtain the fat extract. Add 8 mL of 2% sodium hydroxide methanol solution to the fat extract, connect the reflux condenser, and reflux on a 80°C water bath until the oil droplets disappear. From the top of the reflux condenser, add 7 mL of 15% boron trifluoride methanol solution, continue to reflux at 80°C for 2 min. Rinse the reflux condenser with a small amount of water. Stop heating, remove the flask from the water bath, and cool quickly to room temperature. Accurately add 20 mL of n-heptane, shake for 2 min, then add saturated sodium chloride aqueous solution, stand for separation. Take 5 mL of the upper n-heptane extract solution into a 25 mL test tube, add 5 g of anhydrous sodium sulfate, shake for 1 min, stand for 5 min, and then take the upper solution into a sample bottle for determination. The gas chromatography conditions are: chromatographic column (polydicyclopentylsiloxane strong polarity stationary phase, column length 100 m, inner diameter 0.25 mm, film thickness 0.2 um), injector temperature 270°C, detector temperature 280°C, carrier gas N2, split ratio 100:1, sample volume 100:1.

[0046] Detection of amino acids in mutton: cut the mutton into 1 cm 3Small pieces of meat, using a meat grinder to stir the lamb, transfer to the surface of the dish, the sample is placed in a vacuum freeze dryer-70℃ freeze drying 48 h, after freeze drying, crushing and using a ball mill to 100 mesh. Determination method according to GB 5009.124-2016 "national food safety standard determination of amino acids in food" is carried out. The specific process is: accurately take 0.5 g of sample in the hydrolysis tube, add 15 mL of 6 mol / L hydrochloric acid solution, add 3~4 drops of phenol, freeze the hydrolysis tube with liquid nitrogen for 3 min, vacuum, nitrogen, repeat 3 times, seal under the condition of nitrogen, put the sealed hydrolysis tube in the electric heating air drying constant temperature box hydrolysis 22 h, take out, cool to room temperature. The hydrolysis liquid is filtered into a 50 mL volumetric flask, and the water is set to the scale line, and the shaking is shaken. For the determination of amino acids. Instrument test conditions: the chromatographic column is sulfonic acid type cation resin, and the detection wavelength is 570 nm and 440 nm.

[0047] Example 2

[0048] A method for identifying grassland grazing sheep: detecting the δ 13 C, δ 15 N stable isotope value; if δ 13 C≤-19.0‰, δ 15 N≥4.0‰, it is determined as grassland grazing sheep.

[0049] Collecting sheep neck hair as a stable isotope determination sample. Detecting δ 13 C, δ 15 N stable isotope value: collect sheep neck hair, cut to 0.5 cm, grind to 100 mesh using a ball mill, wrap the sample in filter paper, use soxhlet extraction method, degrease at 60℃ for 6 h, and then naturally dry to obtain the hair stable isotope sample; use stable isotope mass spectrometer for determination, the instrument determination conditions are the same as "detecting δ 13 C, δ 15 N stable isotope value" in example 1.

[0050] Test example 1

[0051] Taking δ 13 C and δ 15 N of sheep neck hair as technical index, its formation and establishment are based on the following: collecting grassland grazing sheep neck hair and corresponding sheep meat samples, respectively, measuring δ 13 C and δ 15 N value of sheep meat and sheep neck hair, using correlation analysis method to establish linear model of sheep neck hair and sheep meat, revealing δ 13 C, δ 15 N and δ 13C, δ 15 N of the correlation degree. The δ 13 C and δ 15 N of the sheep neck hair were determined by the method of Example 1. 13 C and δ 15 N of the sheep neck hair were determined by the method of Example 2.

[0052] The results are shown in Table 1. Figure 1 As shown in Table 1, the results show that the δ 13 C in the sheep meat is in a very significant positive correlation with the δ 13 C in the sheep neck hair, and the correlation coefficient reaches 0.917, and the δ 15 N in the sheep meat is in a very significant positive correlation with the δ 15 N in the sheep neck hair, and the correlation coefficient reaches 0.9414. Therefore, the sheep neck hair is included in the identification technical index system of the grassland grazing sheep meat.

[0053] Test Example 2

[0054] 1. 180 samples of sheep neck hair were collected, including 80 samples of grassland grazing sheep and 100 samples of stall-fed sheep. The samples of grassland grazing sheep covered the four major pastoral areas of Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing and Yunnan in China and the grassland and grass slope grazing areas in southern China. The samples of stall-fed sheep covered the typical stall-fed breeding areas in China, such as Hebei, Shanxi, Inner Mongolia and Shandong. The carbon stable isotope (δ 13 C) and nitrogen stable isotope (δ 15 N) were detected by the method in Example 2, and the results are shown in Table 1. Figures 2-3

[0055] The determination of the carbon stable isotope (δ 13 C) shows that the maximum value of the δ 13 C of the grassland grazing sheep neck hair is -19.05‰, the minimum value is -24.0‰, the average value is -21.36‰, and the median value is -21.32‰. The maximum value of the δ 13 C of the stall-fed sheep neck hair is -11.83‰, the minimum value is -18.44‰, the average value is -15.45‰, and the median value is -15.71‰.

[0056] The determination of the nitrogen stable isotope (δ 15 N) shows that the maximum value of the δ 15 N of the grassland grazing sheep neck hair is 12.0‰, the minimum value is 4.0‰, the average value is 5.0‰, and the median value is 6.1‰. The maximum value of the δ 15 N of the stall-fed sheep neck hair is 9.8‰, the minimum value is 1.8‰, the average value is 4.5‰, and the median value is 6.5‰.

[0057] ​2, 180 samples of mutton were collected, including 100 samples of grassland grazing mutton and 80 samples of stall-feeding mutton. The grassland grazing mutton samples covered the four major pastoral areas in China, i.e. Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing and Yunnan, and the grassland grazing areas in southern China. The stall-feeding mutton samples covered the typical stall-feeding areas in China, i.e. Hebei, Shanxi, Inner Mongolia and Shandong. The carbon stable isotope (δ 13 C) and nitrogen stable isotope (δ 15 N) were detected by the method in Example 1, and the results are shown in Table 1. Figures 4-5

[0058] The determination of the carbon stable isotope (δ 13 C) showed that the maximum value of δ 13 C of the grassland grazing mutton was -19.27‰, the minimum value was -24.15‰, the average value was -21.76‰, and the median value was -21.88‰. The maximum value of δ 13 C of the stall-feeding mutton was -13.5‰, the minimum value was -18.36‰, the average value was -15.79‰, and the median value was -15.92‰.

[0059] The determination of the nitrogen stable isotope (δ 15 N) showed that the maximum value of δ 15 N of the grassland grazing mutton was 9.8‰, the minimum value was 4.0‰, the average value was 7.0‰, and the median value was 8.0‰. The maximum value of δ 15 N of the stall-feeding mutton was 8.8‰, the minimum value was 1.6‰, the average value was 5.3‰, and the median value was 7.1‰.

[0060] 3, 180 samples of mutton were collected, including 100 samples of grassland grazing mutton and 80 samples of stall-feeding mutton. The grassland grazing mutton samples covered the four major pastoral areas in China, i.e. Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing and Yunnan, and the grassland grazing areas in southern China. The stall-feeding mutton samples covered the typical stall-feeding areas in China, i.e. Hebei, Shanxi, Inner Mongolia and Shandong. The fatty acid content was determined and analyzed by the method in Example 1, and the results are shown in Table 2. Figure 6

[0061] The results showed that there was a significant difference in the ω-6 / ω-3 ratio between the grassland grazing mutton and the stall-feeding mutton. The maximum value of the ω-6 / ω-3 ratio of the grassland grazing mutton was 3.01, the minimum value was 0.71, the average value was 1.87, and the median value was 1.77. The maximum value of the ω-6 / ω-3 ratio of the stall-feeding mutton was 10.9, the minimum value was 3.1, the average value was 8.17, and the median value was 6.66.

[0062] ​​4, 180 samples of mutton were collected, including 100 samples of grassland grazing mutton and 80 samples of stall-fed mutton. The grassland grazing mutton samples covered the four major pastoral areas in China, i.e. Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing and Yunnan, and the stall-fed mutton samples covered the typical stall-fed breeding areas in China, i.e. Hebei, Shanxi, Inner Mongolia and Shandong. The amino acid content was determined and analyzed by the method in Example 1, and the results are shown in Table 3. Figure 7

[0063] The results showed that the maximum value of FAA / TAA of grassland grazing mutton was 57.52%, the minimum value was 47.19%, the average value was 52.00%, and the median value was 52.68%. The maximum value of stall-fed mutton was 56.27%, the minimum value was 45.38%, the median value was 49.93%, and the average value was 49.97%.

[0064] 5, The samples were classified and discriminated by SPSS software, and the results are shown in Table 1.

[0065] Table 1 Discrimination analysis results of grassland grazing mutton and stall-fed mutton under different indexes

[0066]

[0067] The results showed that when a single index was used for discrimination, the original verification rate and cross-validation rate of δ 13 C, δ 13 C and δ 15 N, and the ratio of ω-6 / ω-3 fatty acids were all above 90%, and the original verification rate and cross-validation rate of FAA / TAA amino acid composition were all above 70%. When a combination of indexes, i.e. δ 13 C and δ 15 N, and the ratio of ω-6 / ω-3 and FAA / TAA were used for discrimination, the original verification rate and cross-validation rate were significantly improved, both reaching 100%.

[0068] Test Example 3

[0069] 120 samples of sheep neck hair were randomly collected, including 60 samples of grassland grazing sheep and 60 samples of stall-fed sheep. The samples were uniformly numbered, information was summarized, and the feeding categories were distinguished according to the actual sampling situation. The samples were entrusted to a third-party laboratory for testing and analysis of C and N isotopes. The experimental test results of δ 13 C and δ 15 N of sheep neck hair were used to verify whether the sample categories were consistent with the actual situation of sample collection. The technical indexes in Example 2 were used as the discrimination standards for grassland grazing sheep and stall-fed sheep to realize the verification and application of the discrimination method for grassland grazing sheep, and the results are shown in Table 2.

[0070] Table 2 Application results of C and N isotopes of sheep neck hair as the discrimination method for grassland grazing sheep ​

[0071]

[0072] 100 samples of mutton were collected nationwide, including 50 samples of grassland grazing mutton and 50 samples of stall-feeding mutton, which were numbered and information was collected, and the samples were sent to the laboratory for δ 13 C and δ 15 N, fatty acid ratio and amino acid ratio were tested, and the test method was the same as that in Example 1. The technical indexes of Example 1 were used as the identification standard of grassland grazing mutton and stall-feeding mutton to verify and apply the identification method of grassland grazing mutton, and the results are shown in Table 3.

[0073] Table 3 Application results of the identification method of grassland grazing mutton

[0074]

[0075] The results show that, using single δ 13 C as the identification standard, the accuracy rate is 94%, using ω-6 / ω-3 ratio as the identification standard, the result accuracy rate is 93%, using FAA / TAA ratio as the identification standard, the accuracy rate is 70%, using δ 13 C and δ 15 N, ω-6 / ω-3 and FAA / TAA combined index as the identification standard, the result accuracy rate is 100%.

[0076] The above only describes the preferred embodiments of the present application, and it should be noted that for ordinary skilled in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, and these improvements and refinements should also be considered as the protection scope of the present application.

Claims

1. A method of identifying grass-fed lamb, characterised in that, comprising the steps of: determination of δ 13 C、δ 15 N stable isotope values, fatty acid, flavor amino acid and total amino acid content; if δ 13 C≤-19.0‰, δ 15 N≥4.0‰, ω-6:ω-3 in fatty acid≤2.5, flavor amino acid:total amino acid≥50%, it is determined as grassland grazing mutton; the amount of omega-6 in the fatty acids is the total amount of linoleic acid, gamma-linolenic acid, eicosatrienoic acid and arachidonic acid; the amount of omega-3 in the fatty acids is the total amount of alpha-linolenic acid, DHA and EPA; the amount of the flavor amino acids is the total amount of glutamic acid, aspartic acid, phenylalanine, alanine, glycine and tyrosine; the amount of the total amino acids is the total amount of aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine and arginine.

2. The authentication method according to claim 1, characterized in that, A method for detecting δ 13 C, δ 15 The method for detecting stable isotope values of N includes the following steps: removing fat from mutton, stirring, freeze-drying, grinding, using Soxhlet extraction method, using petroleum ether as solvent, defatting, and air-drying to obtain a sample to be measured; and using a stable isotope mass spectrometer to measure the sample to be measured.

3. The method of any one of claims 1-2, wherein, The grass-fed sheep meat includes grass-fed mutton or grass-fed goat meat.

4. Use of the method of any one of claims 1 to 3 for monitoring the quality of sheep meat.

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