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

Abstract

The invention provides a grassland grazing sheep and grassland grazing mutton identification method and application thereof, and belongs to the technical field of food authenticity detection. The stable isotope values of delta 13C and delta 15N of the sheep neck hair are detected, and whether the sheep belongs to grassland grassland can be judged. The identification method for grassland grazing mutton provided by the invention comprises the following steps: detecting stable isotope values of delta 13C and delta 15N and the contents of fatty acid, flavor amino acid and total amino acid in mutton; if delta13C is less than or equal to-19.0 per mill, delta15N is more than or equal to 4.0 per mill, omega-6: omega-3 in fatty acid is less than or equal to 2.5, and flavor amino acid: total amino acid is more than or equal to 50%, determining that the mutton is grassland grazing mutton. According to the identification method, the essential characteristics of grassland grazing mutton are highlighted from a multi-index combined angle, the influence of factors such as variety, region, month age and man-made interference can be eliminated, and the identification precision reaches 100%.

Description

Technical Field

[0001] The invention belongs to the technical field of food authenticity detection, and in particular relates to a method for identifying grassland-grazing sheep and grassland-grazing mutton and an application thereof. Background Art

[0002] With the development of modern animal husbandry, consumers are increasingly concerned about the quality and origin of lamb. As an important meat consumer product, lamb is produced primarily in two modes: confinement and pasture-raised. Compared to confinement-raised lamb, pasture-raised lamb is highly sought after in the market due to its unique flavor, higher protein content, lower fat content, and richness in various vitamins and minerals. It often fetches higher prices and better aligns with current consumer trends towards healthy, natural foods. However, due to the striking similarity in appearance between pasture-raised and confinement-raised lamb, it is difficult to accurately distinguish between the two using traditional sensory identification methods, such as observing the color and texture of the meat and touching the texture. To effectively address this issue, a series of identification methods for pasture-raised and barn-fed lamb have been proposed. Traditional identification methods, both domestic and international, focus on analyzing conventional physical and chemical parameters of the meat. Some studies have measured and compared parameters such as color, pH, shear stress, and cooking loss between pasture-raised and barn-fed lamb. These studies have found that pasture-raised lamb generally has a brighter color and a more stable pH, likely due to the high levels of exercise and natural pasture intake of pasture-raised lambs. However, these traditional methods have significant limitations and are susceptible to various factors, such as subtle differences in breed, age, and rearing environment, which can lead to fluctuations in physical and chemical parameters and affect the accuracy and reliability of identification. Meanwhile, instrumental analysis techniques have also been widely used in lamb identification. For example, by analyzing the spectral characteristics of lamb in the near-infrared band, chemical composition and structural information can be obtained. However, this technique requires extensive sample pretreatment, the spectral data analysis process is complex, and it is susceptible to environmental factors, such as changes in temperature and humidity, which can cause spectral data deviations and affect identification results. In summary, existing methods for identifying pasture-raised lamb have certain deficiencies in accuracy, reliability, convenience, and cost-effectiveness, making it difficult to meet the market's urgent need for rapid and accurate identification of pasture-raised lamb. Therefore, developing a more accurate, reliable, efficient, and cost-effective method for identifying pasture-raised lamb is an urgent need in this field. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the first purpose of the present invention is to provide a grassland-grazing sheep and a method for identifying grassland-grazing mutton, with an identification result accuracy rate of 100%.

[0004] The second object of the present invention is to provide an application of the above method in monitoring mutton quality.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions: The present invention provides a method for identifying grassland grazing sheep, comprising the following steps: Detection of sheep neck wool δ 13 C, δ 15 N stable isotope value; if δ 13 C≤-19.0‰, δ 15 If N≥4.0‰, it is judged as grassland grazing sheep.

[0006] Preferably, the sheep neck hair δ 13 C, δ 15 The method for determining the N stable isotope value includes: chopping and grinding sheep neck wool, performing Soxhlet extraction with petroleum ether as solvent, defatting, and air-drying to obtain a sample to be tested; and measuring the sample to be tested using a stable isotope mass spectrometer.

[0007] The present invention provides a method for identifying grassland-grazing mutton, comprising the following steps: Detection of δ 13 C, δ 15 N stable isotope value, 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≤2.5 in fatty acids, flavor amino acids: total amino acids ≥50%, it is determined to be grassland-grazed lamb.

[0008] Preferably, the δ 13 C, δ 15 The method for determining the N stable isotope value includes: removing fat from mutton, mincing, freeze-drying, and grinding, using Soxhlet extraction with petroleum ether as a solvent, defatting, and air-drying to obtain a sample to be tested; and measuring the sample to be tested using a stable isotope mass spectrometer.

[0009] Preferably, the amount of ω-6 fatty acids is the total amount of linoleic acid, gamma-linolenic acid, eicosatrienoic acid and arachidonic acid.

[0010] Preferably, the amount of omega-3 fatty acids is the total amount of α-linolenic acid, DHA and EPA.

[0011] Preferably, the amount of the flavor amino acids is the total amount of glutamic acid, aspartic acid, phenylalanine, alanine, glycine and tyrosine.

[0012] Preferably, the amount of 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.

[0013] Preferably, the pasture-grazing lamb comprises pasture-grazing lamb or pasture-grazing goat meat.

[0014] The present invention also provides application of the identification method in monitoring mutton quality.

[0015] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: The present invention uses carbon and nitrogen stable isotopes to identify the neck hair of living sheep, which can be used to assess whether the object to be tested is a grassland-grazing sheep. The identification accuracy of grassland-grazing sheep reaches 99.2%.

[0016] The present invention establishes a precise identification technology for grassland-grazing mutton from the perspective of multiple indicators, including carbon and nitrogen stable isotopes, ω-6 / ω-3 fatty acid ratio and flavor amino acid proportion, highlighting the essential characteristics of grassland-grazing mutton. It can eliminate the influence of factors such as breed, region, age and human interference on grassland-grazing mutton, and the identification accuracy of grassland-grazing mutton reaches 100%. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 :Correlation between C and N stable isotopes in mutton and sheep neck hair; Figure 2 :δ of neck wool from grassland-grazing sheep and sheep fed in sheds 13 C value; Figure 3 :δ of neck wool from grassland-grazing sheep and sheep fed in sheds 15 N value; Figure 4 : The δ of grassland-grazing lamb and house-fed lamb 13 C value; Figure 5 : The δ of grassland-grazing lamb and house-fed lamb 15 N value; Figure 6 : Distribution of fatty acids ω-6 / ω-3 in meat from pasture-fed and house-fed lamb; Figure 7 : Distribution of flavor amino acids / total amino acids in grassland-grazed and house-fed lamb. DETAILED DESCRIPTION

[0018] The present invention provides a method for identifying grassland grazing sheep, comprising the following steps: detecting the δ 13 C, δ 15 N stable isotope value; if δ13 C≤-19.0‰, δ 15 N≥4.0‰, it is determined to be grassland grazing sheep. 13 C, δ 15 The identification method of N can be used for identifying grassland grazing sheep before they are put on the market or before live sheep are slaughtered, and can be used to identify in advance whether the sheep to be slaughtered are grassland grazing sheep.

[0019] In the present invention, the sheep neck hair δ 13 C, δ 15 The method for determining the nitrogen stable isotope value comprises: chopping and grinding sheep neck hair, performing Soxhlet extraction with petroleum ether as a solvent, degreasing, and air-drying to obtain a sample to be tested; and performing stable isotope mass spectrometry on the sample to be tested. The sheep neck hair is preferably chopped to 0.5 cm, ground to 100 mesh, and the sample is wrapped in filter paper. The sample is then degreased at 60°C for 6 hours using Soxhlet extraction with petroleum ether as a solvent, and then naturally dried to obtain the hair stable isotope sample to be tested.

[0020] The present invention provides a method for identifying grassland-grazing mutton, comprising the following steps: detecting δ 13 C, δ 15 N stable isotope value, 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≤2.5 in fatty acids, flavor amino acids: total amino acids ≥50%, it is determined to be grassland-grazed lamb.

[0021] In the present invention, the δ 13 C, δ 15 The method for determining the nitrogen stable isotope value comprises: removing fat from mutton, mincing, freeze-drying, and grinding. Soxhlet extraction is performed using petroleum ether as a solvent, defatting, and air-drying to obtain a sample to be tested; the sample to be tested is then analyzed using a stable isotope mass spectrometer. The mutton can be front leg meat. As an optional embodiment, the present invention seals the mutton collected on-site in sealed ziplock bags and stores it at -20°C. Prior to testing, the frozen mutton is thawed at 4°C, and a semi-thawed sample is taken for testing. As another optional embodiment, the present invention uses on-site samples for direct on-site testing. The mutton to be tested is removed of fat, minced, and vacuum freeze-dried. The vacuum freeze-drying conditions of the present invention can be frozen at -70°C for 48 hours. The freeze-dried mutton is then pulverized and ground to a 100-mesh size. The sample is wrapped in filter paper and subjected to Soxhlet extraction using petroleum ether as a solvent. After defatting at 60°C for 6 hours, the sample is air-dried to obtain a sample to be tested for stable isotopes.

[0022] In the present invention, the instrument measurement conditions for the stable isotope mass spectrometer are as follows: the helium purge flow rate of the sampler is 200 mL / min, the combustion furnace temperature is 960°C, the reduction furnace temperature is 650°C, and the carrier gas He flow rate 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 (δ 13 CPDB=-16.00‰) to calibrate CO2 cylinders, using IAEAN (δ 15 Nair=0.4‰) to calibrate CO2 cylinders, using the calibrated cylinder as the standard.

[0023] In the present invention, the fatty acid content is preferably determined by gas chromatography, preferably in accordance with GB5009.168-2016, "National Food Safety Standard - Determination of Fatty Acids in Food." The method described herein can detect the contents of 37 fatty acids. The ω-6 fatty acid content is defined as the sum of linoleic acid, γ-linolenic acid, eicosatrienoic acid, and arachidonic acid; and the ω-3 fatty acid content is defined as the sum of α-linolenic acid, DHA (docosahexaenoic acid), and EPA (eicosapentaenoic acid).

[0024] In the present invention, the amino acid content is preferably determined using an amino acid analyzer, preferably in accordance with GB 5009.124-2016, "National Food Safety Standard - Determination of Amino Acids in Food." The method described herein can detect the content of 16 hydrolyzed amino acids. The amount of flavor amino acids (FAA) is the sum of glutamic acid, aspartic acid, phenylalanine, alanine, glycine, and tyrosine; the amount of total amino acids (TAA) is the sum of aspartic acid, threonine, serine, glutamic acid, proline, glycine, alanine, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, histidine, lysine, and arginine.

[0025] In the present invention, grassland-grazing mutton includes grassland-grazing sheep meat or grassland-grazing goat meat.

[0026] The present invention also provides application of the identification method in monitoring mutton quality.

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0028] In the following examples, unless otherwise specified, all methods are conventional.

[0029] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0030] Example 1 A method for identifying grassland-grazing lamb: Detection of δ 13 C, δ 15 N stable isotope value, 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≤2.5 in fatty acids, flavor amino acids: total amino acids ≥50%, it is determined to be grassland-grazed lamb.

[0031] The front leg of mutton was taken as the sample for the determination of stable isotopes, fatty acids and amino acids. 2.0 kg of mutton from the front leg was collected and sealed in a ziplock bag and stored at -20°C. When waiting for testing, the frozen mutton was placed at room temperature. When it was in a semi-thawed state, samples were taken for testing.

[0032] Detection of δ 13 C, δ 15 N stable isotope value: When testing mutton, remove the fat part and cut the mutton into 1 cm 3 The mutton was minced with a meat grinder and transferred to a surface dish. The minced sample was placed in a vacuum freeze dryer at -70℃ and freeze-dried for 48 hours. After freeze-drying, it was crushed and ground into 100 mesh using a ball mill. The sample was wrapped in a filter paper bag and subjected to Soxhlet extraction with petroleum ether as the solvent. After degreasing at 60℃ for 6 hours, the sample was naturally dried to obtain the sample to be tested for stable isotopes. The stable isotope mass spectrometer was used for determination. The instrumental determination conditions were as follows: the helium purge flow rate of the injector was 200mL / min, the combustion furnace temperature was 960℃, the reduction furnace temperature was 650℃, and the carrier gas He flow rate was 90~100mL / min. The He dilution pressure was 0.6 bar, the CO2 reference gas pressure was 0.6 bar, and the N2 reference gas pressure was 1.0 bar. The USGS24 (δ 13 CPDB=-16.00‰) to calibrate CO2 cylinders, using IAEAN (δ 15 Calibrate CO2 cylinders with a Nair value of 0.4‰ and use the calibrated cylinder as a standard.

[0033] Detection of fatty acids in mutton: Cut the mutton into 1 cm 3Use a meat grinder to mince the mutton, transfer it to a watch glass, and freeze-dry the minced sample in a vacuum freeze dryer at -70°C for 48 hours. After freeze-drying, crush it and grind it 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 Foods." The specific procedure is as follows: Weigh 0.5 g of the sample and transfer it to a 250 mL flat-bottom flask. Accurately add 2.0 mL of undecanoic acid triglyceride internal standard solution, add approximately 200 mg of pyrogallic acid, add a few grains of zeolite, then add 2 mL of 95% ethanol and 4 mL of water, mix thoroughly, add 10 mL of 8.3 mol / L hydrochloric acid solution, and hydrolyze the flask in an 80°C water bath for 40 minutes. After the hydrolysis is complete, remove the flask and cool it to room temperature. After hydrolysis, add 10 mL of 95% ethanol to the sample and mix thoroughly. Transfer the hydrolyzed solution from the flask to a separatory funnel. Rinse the flask and stopper with 50 mL of ether and petroleum ether (1:1 volume ratio). Combine the rinse solution in the separatory funnel, cover, and shake for 5 minutes. Let stand for 10 minutes. Collect the ethereal extract into a 250 mL flask. Repeat the above extraction procedure three times. Combine the ethereal extracts and concentrate to dryness on a rotary evaporator to obtain the fat extract. Add 8 mL of 2% sodium hydroxide in methanol to the fat extract. Connect a reflux condenser and reflux in an 80°C water bath until the oil droplets disappear. Add 7 mL of 15% boron trifluoride in methanol from the top of the reflux condenser and continue reflux at 80°C for 2 minutes. Rinse the reflux condenser with a small amount of water. Stop heating, remove the flask from the water bath, and quickly cool to room temperature. Accurately add 20 mL of n-heptane, shake for 2 minutes, then add saturated sodium chloride solution and let stand to separate the layers. Pipette 5 mL of the n-heptane extract from the upper layer into a 25 mL test tube, add 5 g of anhydrous sodium sulfate, shake for 1 minute, let stand for 5 minutes, and then transfer the upper layer to an injection vial for analysis. Gas chromatography conditions were: column (polydicyanopropylsiloxane strong polar stationary phase, column length 100 μm, inner diameter 0.25 mm, film thickness 0.2 μm), injector temperature 270°C, detector temperature 280°C, carrier gas N2, split ratio 100:1, injection volume 100:1.

[0034] Detection of amino acids in mutton: Cut the mutton into 1 cm 3Use a meat grinder to mince the mutton, transfer it to a watch glass, and freeze-dry the minced sample in a vacuum freeze dryer at -70°C for 48 hours. After freeze-drying, crush it and grind it to 100 mesh using a ball mill. The determination method is based on GB 5009.124-2016, "National Food Safety Standard - Determination of Amino Acids in Foods." The specific procedure is as follows: Accurately weigh 0.5 g of the sample and place it in a hydrolysis tube. Add 15 mL of 6 mol / L hydrochloric acid solution and 3-4 drops of phenol. Freeze the hydrolysis tube with liquid nitrogen for 3 minutes, evacuate the tube, and then fill it with nitrogen three times. Seal the tube while still filled with nitrogen, and hydrolyze it in an electric forced-air drying oven at 110°C for 22 hours. Remove the tube and cool it to room temperature. Filter the hydrolyzate into a 50 mL volumetric flask, dilute to the mark with water, and shake well. This is used for amino acid determination. Instrument test conditions: The chromatographic column is a sulfonic acid cationic resin, and the detection wavelengths are 570 nm and 440 nm.

[0035] Example 2 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 If N≥4.0‰, it is judged as grassland grazing sheep.

[0036] Sheep neck hair was collected as a sample for stable isotope determination. 13 C, δ 15 N stable isotope value: Sheep neck hair was collected, cut into 0.5 cm pieces, and ground into 100 mesh using a ball mill. The sample was wrapped in a filter paper bag and subjected to Soxhlet extraction using petroleum ether as the solvent. After degreasing at 60°C for 6 h, the hair was naturally dried to obtain the hair stable isotope sample to be tested. The stable isotope mass spectrometer was used for determination. The instrumental determination conditions were the same as those in Example 1 for the “Detection of δ 13 C, δ 15 N stable isotope values” are the same.

[0037] Test Example 1 The δ of sheep neck wool 13 C and δ 15 N is a technical indicator, and its formation and establishment are based on the following: collect neck hair and corresponding mutton samples from grassland grazing sheep, and measure the δ 13 C and δ 15 N value, the linear model of sheep neck wool and mutton was established by correlation analysis, revealing the δ 13 C, δ 15 N and sheep neck wool δ 13 C, δ 15The correlation degree of N. mutton δ 13 C and δ 15 The determination method of N is the same as that in Example 1, and the sheep neck hair δ 13 C and δ 15 The determination method of N is the same as in Example 2.

[0038] The results are as follows Figure 1 As shown, the results showed that δ 13 C and δ in sheep neck wool 13 C showed a very significant positive correlation, with a correlation coefficient of 0.917. 15 N and δ of sheep neck hair 15 N showed an extremely significant positive correlation, with a correlation coefficient of 0.9414. Therefore, sheep neck hair was included in the technical indicator system for identifying grassland-grazing mutton.

[0039] Test Example 2 1. 180 samples of sheep neck wool were collected, including 80 samples from grassland grazing sheep and 100 samples from stall-fed sheep. The grassland grazing sheep samples covered the four major pastoral areas of Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing, and Yunnan, as well as the grassland and slope grazing areas in the south. The stall-fed sheep samples 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 isotopes (δ 15 N) to test, the results are as follows Figure 2~Figure 3 shown.

[0040] Stable carbon isotopes (δ 13 C) showed that the δ 13 The maximum value of C was -19.05‰, the minimum value was -24.0‰, the average value was -21.36‰, and the median value was -21.32‰; while the δ 13 The maximum value of C is -11.83‰, the minimum value is -18.44‰, the average value is -15.45‰, and the median value is -15.71‰.

[0041] Stable nitrogen isotopes (δ 15 N) showed that the δ 15 The maximum value of N was 12.0‰, the minimum value was 4.0‰, the average value was 5.0‰, and the median value was 6.1‰; 15 The maximum value of N is 9.8‰, the minimum value is 1.8‰, the average value is 4.5‰, and the median value is 6.5‰.

[0042] 2. 180 mutton samples were collected, including 100 samples of grassland-grazing mutton and 80 samples of house-fed mutton. The grassland-grazing mutton samples covered the four major pastoral areas of China, including Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing, and Yunnan, as well as the grassland and slope grazing areas in the south. The house-fed mutton samples covered the house-fed breeding areas in typical agricultural areas of China, such as Hebei, Shanxi, Inner Mongolia, and Shandong. The carbon stable isotope (δ 13 C) and nitrogen stable isotopes (δ 15 N) to test, the results are as follows Figure 4~Figure 5 shown.

[0043] Stable carbon isotopes (δ 13 C) showed that the δ 13 The maximum value of C was -19.27‰, the minimum value was -24.15‰, the average value was -21.76‰, and the median value was -21.88‰; while the δ 13 The maximum value of C is -13.5‰, the minimum value is -18.36‰, the average value is -15.79‰, and the median value is -15.92‰.

[0044] Stable nitrogen isotopes (δ 15 The determination of N) showed that the δ 15 The maximum value of N was 9.8‰, the minimum value was 4.0‰, the average value was 7.0‰, and the median value was 8.0‰; 15 The maximum value of N is 8.8‰, the minimum value is 1.6‰, the average value is 5.3‰, and the median value is 7.1‰.

[0045] 3. 180 mutton samples were collected, including 100 samples of grassland-grazing mutton and 80 samples of shed-fed mutton. The grassland-grazing sheep samples covered the four major pastoral areas of China, including Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing, and Yunnan, as well as the grassland and slope grazing areas in the south. The shed-fed sheep samples covered the typical shed-fed farming areas in China, such as Hebei, Shanxi, Inner Mongolia, and Shandong. The fatty acid content was determined and analyzed using the method in Example 1. The results are as follows: Figure 6 shown.

[0046] The results showed that the ω-6 / ω-3 ratio of grassland-grazing and house-fed lamb was significantly different. The maximum ω-6 / ω-3 value of grassland-grazing lamb was 3.01, the minimum was 0.71, the average was 1.87, and the median was 1.77; while the maximum ω-6 / ω-3 value of house-fed lamb was 10.9, the minimum was 3.1, the average was 8.17, and the median was 6.66.

[0047] 4. 180 mutton samples were collected, including 100 samples of grassland-grazing mutton and 80 samples of house-fed mutton. The grassland-grazing sheep samples covered the four major pastoral areas of China, including Inner Mongolia, Xinjiang, Tibet, Qinghai, Chongqing, and Yunnan, as well as the grassland and slope grazing areas in the south. The house-fed sheep samples covered the typical house-fed breeding areas in China, including Hebei, Shanxi, Inner Mongolia, and Shandong. The amino acid content was determined and analyzed using the method in Example 1. The results are as follows: Figure 7 shown.

[0048] The results showed that the maximum FAA / TAA of grassland-grazing lamb was 57.52%, the minimum was 47.19%, the average was 52.00%, and the median was 52.68%. The maximum FAA / TAA of house-fed lamb was 56.27%, the minimum was 45.38%, the median was 49.93%, and the average was 49.97%.

[0049] 5. SPSS software was used to perform classification and discriminant analysis on the samples. The results are shown in Table 1.

[0050] Table 1 Results of discriminant analysis between grassland-grazing mutton and barn-fed mutton under different indicators

[0051] The results show that when using a single indicator for discrimination, δ 13 C, δ 13 C and δ 15 The original validation rate and cross validation rate of N, ω-6 / ω-3 fatty acid ratio reached more than 90%, and the original validation rate and cross validation rate of FAA / TAA amino acid composition reached more than 70%. 13 C and δ 15 When N, ω-6 / ω-3, and FAA / TAA were discriminated simultaneously, the original validation rate and cross-validation rate were significantly improved, both reaching 100%.

[0052] Test Example 3 120 samples of sheep neck hair were randomly collected, including 60 samples from grazing sheep and 60 samples from barn-fed sheep. They were uniformly numbered, information was summarized, and the breeding categories were distinguished according to the actual sampling situation. The samples were commissioned to a third-party laboratory for C and N isotope testing and analysis. The δ 13 C and δ 15 The experimental test results of N were used to verify whether the sample category was consistent with the actual situation of sample collection. The technical indicators of Example 2 were used as the identification criteria for grassland grazing sheep and barn-fed sheep to realize the verification and application of the grassland grazing sheep identification method. The results are shown in Table 2.

[0053] Table 2 Results of using sheep neck wool C and N isotopes as a method for identifying grassland grazing sheep

[0054] 100 mutton samples were collected nationwide, including 50 samples from grassland-grazing mutton and 50 samples from shed-fed mutton. The samples were uniformly numbered and their information was summarized. The samples were uniformly sent to the laboratory for δ 13 C and δ 15 The test methods for the indicators of N, fatty acid ratio, and amino acid ratio were the same as those in Example 1. The technical indicators in Example 1 were used as the identification criteria for grassland-grazing and barn-fed mutton to verify and apply the identification method for grassland-grazing mutton. The results are shown in Table 3.

[0055] Table 3 Application results of identification methods for grassland-grazing lamb

[0056] The results show that with a single δ 13 The accuracy rate of the identification criteria was 94% when the ω-6 / ω-3 ratio was used as the identification criteria, the accuracy rate was 93%, the accuracy rate of the FAA / TAA ratio was 70%, and the accuracy rate of the δ 13 C and δ 15 The combined indicators of N, ω-6 / ω-3 and FAA / TAA were used as identification criteria, and the accuracy rate of the results was 100%.

[0057] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for identifying sheep grazing on grassland, characterized in that: The steps include: Detection of sheep neck wool δ 13 C, δ 15 N stable isotope value; if δ 13 C≤-19.0‰, δ 15 If N≥4.0‰, it is judged as grassland grazing sheep.

2. The identification method according to claim 1, characterized in that: Detection of sheep neck wool δ 13 C, δ 15 The method for determining the N stable isotope value includes: chopping and grinding sheep neck wool, performing Soxhlet extraction with petroleum ether as solvent, defatting, and air-drying to obtain a sample to be tested; and measuring the sample to be tested using a stable isotope mass spectrometer.

3. A method for identifying grassland-grazing mutton, characterized in that: The steps include: Detection of δ 13 C, δ 15 N stable isotope value, 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≤2.5 in fatty acids, flavor amino acids: total amino acids ≥50%, it is determined to be grassland-grazed lamb.

4. The identification method according to claim 3, characterized in that: Detection of δ 13 C, δ 15 The method for determining the N stable isotope value includes: removing fat from mutton, mincing, freeze-drying, and grinding, using Soxhlet extraction with petroleum ether as a solvent, defatting, and air-drying to obtain a sample to be tested; and measuring the sample to be tested using a stable isotope mass spectrometer.

5. The identification method according to claim 3, characterized in that: The amount of omega-6 fatty acids is the sum of linoleic acid, gamma-linolenic acid, eicosatrienoic acid, and arachidonic acid.

6. The identification method according to claim 3, characterized in that: The amount of omega-3 fatty acids is the sum of α-linolenic acid, DHA, and EPA.

7. The identification method according to claim 3, characterized in that: The amount of the flavor amino acids is the total amount of glutamic acid, aspartic acid, phenylalanine, alanine, glycine and tyrosine.

8. The identification method according to claim 3, characterized in that: The amount of 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.

9. The identification method according to any one of claims 3 to 8, characterized in that: The pasture-grazing lamb includes pasture-grazing lamb or pasture-grazing goat meat.

10. Use of the identification method according to any one of claims 3 to 9 in monitoring mutton quality.

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