A method for comprehensive evaluation of mutton quality

Abstract

A comprehensive evaluation method for mutton quality belongs to the fields of food science and animal husbandry. This method includes: (1) determination of multi-dimensional indicators: measuring the meat color brightness L... * , redness a * Yellowness b * (1) Shear force, water loss rate, pH value at 45 minutes and 24 hours post-slaughter, muscle fiber diameter, density, total area, area and total number of individual fibers, marbling grade, and key metabolites such as inosinic acid and fatty acids; (2) Standardized scoring conversion: convert the 14 indicators into 1 to 5 points according to preset thresholds; (3) Comprehensive scoring calculation: T=∑Sᵢ(i=1~14); (4) Quality grade classification: Special grade (T≥65), Excellent grade (55≤T<65), Good grade (35≤T<55), Ordinary grade (15≤T<35), Poor grade (T<15). This invention realizes the multi-dimensional integrated evaluation of sensory, texture, physicochemical, microstructure, appearance and flavor quality, and solves the problems of single indicators, inconsistent dimensions and lack of unified standards across parts in existing methods, providing technical support for accurate grading of mutton, market pricing and breed selection.

Description

Technical Field

[0001] This invention belongs to the fields of food science and animal husbandry, and relates to a method for evaluating the quality of animal meat, specifically a comprehensive evaluation method for the quality of mutton. Background Technology

[0002] Mutton is an important meat product consumed in my country. As the mutton industry develops towards large-scale, standardized, and high-quality production, accurate evaluation of mutton quality has become a crucial technical foundation affecting product grading, market pricing, and breed selection. Its quality is influenced by various factors, including breed, feeding methods, and muscle cuts. Taking Hu sheep as an example, significant differences exist in meat color, tenderness, and muscle fiber structure among different parts such as the longissimus dorsi, biceps femoris, and tail muscle, necessitating the establishment of a unified evaluation method across different muscle parts.

[0003] In the prior art, there have been some studies on comprehensive evaluation methods for the quality of other livestock and poultry meat. For example, Chinese patent application CN105891432A discloses a comprehensive evaluation method for goose meat quality, which uses principal component analysis to construct a comprehensive scoring model and selects pH, protein content, fat content, moisture content, collagen content, and cholesterol content as evaluation indicators. However, this method is designed for goose meat, whose muscle fiber type and fat deposition characteristics differ significantly from those of mutton. Furthermore, the selected indicators mainly focus on nutritional and processing quality, failing to fully reflect the tenderness, juiciness, and flavor—qualities directly perceived by consumers—making it difficult to directly apply to the evaluation of mutton quality. As another example, Chinese patent CN107389884B discloses a comprehensive evaluation method for the quality of snow mountain chicken, which establishes a weighted index model based on ATP, IMP, pH, water-holding capacity, shear force, meat color, and intramuscular fat content. Although this method involves edible quality-related indicators, there are fundamental differences between the two in terms of muscle fiber diameter, muscle fiber density, marbling distribution, and flavor metabolite composition. Furthermore, the index weights of this method are determined based on the genetic parameters of chicken meat, and are not applicable to the quality evaluation of mutton.

[0004] Therefore, the evaluation methods in the existing technology still have the following significant shortcomings:

[0005] (1) The evaluation dimensions are too limited and lack the integration of multiple indicators. Existing technologies often rely on a single or a few indicators for evaluation, such as using shear force to characterize tenderness or pH value to judge changes in meat. However, the quality of mutton is determined by multiple factors such as muscle fiber structure, fat deposition and metabolic level, and a single indicator is difficult to reflect the overall quality.

[0006] (2) There is a lack of unified quantitative standards among multiple indicators. Different indicators have different dimensions and numerical ranges (such as shear force measured in N, pH as a dimensionless value, and muscle fiber density as an area count), making it difficult to directly compare and integrate them, which limits the comparability and generalizability of the evaluation results.

[0007] (3) Ignoring microstructure and metabolite information, structural parameters such as muscle fiber diameter and density are key factors that determine tenderness and water retention, but the existing evaluation system does not include them in a unified model; at the same time, flavor metabolites such as inosinic acid and unsaturated fatty acids are not included in the scoring system, resulting in a discrepancy between the evaluation results and the actual eating quality.

[0008] (4) There is a lack of a unified comprehensive scoring model and cross-site evaluation standards. At present, there is no standardized model that integrates physicochemical indicators, tissue structure and metabolic information. Moreover, the significant differences between different muscle sites make it difficult for existing methods to achieve unified evaluation across sites, which affects industrial applications. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies in evaluating mutton quality, which suffer from single indicators, inconsistent standards, and an inability to conduct comprehensive assessments. This invention proposes a comprehensive evaluation method for mutton quality. By integrating, standardizing, and quantifying multiple indicators of mutton muscle characteristics, this method enables an objective, accurate, and repeatable comprehensive assessment of mutton quality. This further facilitates precise grading of mutton quality and provides an important technical foundation for market pricing and breed selection.

[0010] The method for comprehensive evaluation of mutton quality provided in this application adopts the following technical solution:

[0011] A method for comprehensive evaluation of mutton quality, characterized by comprising the following steps:

[0012] (1) Multidimensional index measurement

[0013] The meat quality evaluation indicators for mutton samples were determined, and the meat quality evaluation indicators included:

[0014] Sensory quality index: flesh color brightness L * flesh-colored redness a * flesh-colored yellowness b * ;

[0015] Texture quality indicators: shear force, water loss rate;

[0016] Physicochemical quality indicators: pH value 45 minutes after slaughter and pH value 24 hours after slaughter;

[0017] Microstructural quality indicators: muscle fiber diameter, muscle fiber density, total muscle fiber area, area of ​​a single muscle fiber, and total number of muscle fibers;

[0018] Appearance quality indicators: Marble pattern grade;

[0019] Flavor quality indicators: key metabolites;

[0020] (2) Standardized scoring conversion

[0021] The data obtained from each of the meat quality evaluation indicators are converted into corresponding indicator scores according to a preset scoring standard, wherein S1 to S... 13 The score range is 1 to 5 points, corresponding to three levels: Average, Good, and Excellent. Average is 1 point, Good is 3 points, and Excellent is 5 points. 14 The bonus points for metabolites range from 0 to 5 points.

[0022] (3) Calculation of comprehensive score

[0023] Substituting the scores of each indicator into the comprehensive scoring formula, the comprehensive score T for mutton quality is calculated:

[0024] T=S1+S2+S3+S4+S5+S6+S7+S8+S9+S 10 +S 11 +S 12 +S 13 +S 14 ;

[0025] In the formula: S1 is the flesh-colored brightness L * The corresponding indicator score; S2 represents the flesh-colored redness a. * The corresponding index score; S3 represents the yellowness of the flesh tone (b). * The corresponding index scores are as follows: S4 is the index score corresponding to shear force; S5 is the index score corresponding to water loss rate; S6 is the index score corresponding to pH value 45 minutes after slaughter; S7 is the index score corresponding to pH value 24 hours after slaughter; S8 is the index score corresponding to muscle fiber diameter; S9 is the index score corresponding to muscle fiber density; S 10 S represents the index score corresponding to the total area of ​​muscle fibers. 11 The index score corresponding to the area of ​​a single muscle fiber; S 12 S represents the index score corresponding to the total number of muscle fibers. 13 S represents the index score corresponding to the marble texture grade. 14 The score represents the indicator value corresponding to the key metabolites;

[0026] (4) Quality grade classification

[0027] The quality grades of mutton are classified according to the range of the comprehensive score T: Special grade: T≥65; Excellent grade: 55≤T<65; Good grade: 35≤T<55; Average grade: 15≤T<35; Poor grade: T<15.

[0028] By adopting the above technical solution and constructing a four-step evaluation system of measurement, conversion, calculation, and grading, 14 indicators across six dimensions—sensory, texture, physicochemical, microstructure, appearance, and flavor—are standardized and quantified. A weighted summation model is used to calculate the comprehensive score, achieving a fusion evaluation of multi-dimensional quality information. This solves the problems of existing evaluation methods, such as the reliance on single indicators that cannot comprehensively reflect mutton quality; the lack of unified quantitative standards for indicators of different dimensions, making integration and comparison difficult; and the lack of standardized evaluation models across different parts and varieties. It provides the industry with a standardized quality judgment tool.

[0029] Furthermore, the flesh-colored brightness L * flesh-colored redness a * flesh-colored yellowness b * The measurement method is as follows: a colorimeter is used for measurement, with a D65 standard light source and a 2° observation angle. Measurements are taken continuously 3 to 9 times at the same location, and the flesh color brightness (L) is recorded. * flesh-colored redness a * flesh-colored yellowness b * The average value is taken as the final result.

[0030] By adopting the above technical solution and using the CIE standard colorimetric system (D65 light source, 2° field of view), and averaging through multi-point sampling, errors in measurement location and operation are eliminated, ensuring the accuracy and reproducibility of flesh color data. This solves the problems of flesh color measurement being greatly affected by light source conditions, observation angle, and sampling location, leading to unstable evaluation results due to data fluctuations. Standardized measurement conditions improve the accuracy and comparability of flesh color data, ensuring objective and reliable evaluation results.

[0031] Furthermore, the shear force was measured in accordance with the standard procedure of NY / T 1180-2006 "Determination of Meat Tenderness - Shear Force Test".

[0032] By adopting the above technical solution and using the Warner-Bratzler shear force measurement method, and through standardized tools and operating procedures, the muscle's ability to resist shear can be quantified, indirectly reflecting the muscle's tenderness, making the data measurement more standardized and comparable.

[0033] Furthermore, the water loss rate was determined using the pressure method, following the standard procedure of NY / T 1333-2007 "Determination of Meat Quality of Livestock and Poultry".

[0034] By employing the above technical solution and applying standardized mechanical pressure, the proportion of water lost from muscle under specific conditions is quantitatively measured, reflecting the water-retention capacity of the muscle. This achieves objective quantification of water retention, providing a basis for evaluating meat quality and juiciness.

[0035] Furthermore, the method for determining the pH value 45 minutes and 24 hours after slaughter is as follows: a portable pH meter is used for measurement. Before measurement, the meat sample is stored at 0℃~4℃. During measurement, the pH electrode is directly inserted into the muscle. The measurement is repeated 3 times at different parts of the same sample and the average value is taken.

[0036] By employing the above technical solution and utilizing the potential response characteristics of glass electrodes, the muscle acidification process is monitored at specific time points (45 minutes and 24 hours post-slaughter) to reflect the muscle glycolysis rate and final pH value, thereby determining the presence of abnormal acidification or DFD (digestive disease) meat. This dual-time-point monitoring allows for a comprehensive understanding of muscle acidification dynamics, timely detection of abnormal meat, and improved evaluation accuracy.

[0037] Furthermore, the methods for determining the muscle fiber diameter, muscle fiber density, total muscle fiber area, area of ​​a single muscle fiber, and total number of muscle fibers are as follows: the determination is carried out using histological methods. The muscle sample is fixed with 4% paraformaldehyde, dehydrated, embedded, sectioned, and then stained with hematoxylin and eosin. The sample is observed and images are acquired under a microscope at 400x magnification. The muscle fiber diameter, total muscle fiber area, and number of muscle fibers are measured using image analysis software, and the area of ​​a single muscle fiber and the muscle fiber density are calculated accordingly.

[0038] By employing the above-mentioned technical solutions, muscle fiber morphology is preserved using tissue fixation and staining techniques. Structural parameters such as diameter, density, and area of ​​the muscle fibers are then deduced from two-dimensional sections using microscopic imaging and image analysis software. Incorporating these microstructural parameters into the evaluation system reveals the structural basis of quality formation, enabling the evaluation to move from phenotypic to the tissue level.

[0039] Furthermore, the marbled texture grade is evaluated using a visual scoring method. Under natural light or standard light source conditions, the cross-section of the muscle is compared with a standard marbled texture scoring board. The grade is determined based on the uniformity and obviousness of fat distribution, referring to the NY / T 2781-2015 "Grading Specifications for Lamb Carcasses". Grades 1 to 3 are grade A, grades 4 to 6 are grade B, and grades 6 and above are below grade B.

[0040] By employing the above technical solution, and combining sensory evaluation with standard atlas comparison, the fat distribution characteristics of marbling are transformed into graded classifications, which are then mapped to quantitative scores. This achieves a semi-quantitative evaluation of intramuscular fat distribution, and is simple to operate and inexpensive.

[0041] Furthermore, the key metabolites are detected using metabolomics methods. Gas chromatography-mass spectrometry or gas chromatography-olfactometry is used to perform qualitative and quantitative analysis of flavor-related metabolites in the sample. The detected metabolites include maltose, taurine, carnosine, inosinic acid, oleic acid, linoleic acid, and linolenic acid.

[0042] By employing the above-mentioned technical solutions, utilizing the separation capabilities of gas chromatography and the qualitative and quantitative capabilities of mass spectrometry, or combining them with flavor activity screening using olfactory detection, characteristic metabolites related to flavor can be identified and measured. This achieves precise qualitative and quantitative analysis of flavor-related metabolites, providing objective molecular-level evidence for flavor quality evaluation.

[0043] Furthermore, in this step, the data measured for each meat quality evaluation indicator are converted into corresponding indicator scores according to a preset scoring standard. The conversion standard is as follows:

[0044] index Medium (1 point) Good (3 points) Excellent (5 points) <![CDATA[Flesh color brightness L * > 34.39～41.39 41.40～45.40 45.41～48.91 <![CDATA[Meat color redness a * > 10.03～11.88 11.89～12.53 12.54～13.48 <![CDATA[Flesh color yellowness b * > 5.82～8.46 4.84～5.81 3.99～4.83 Shear force (N) 23.87～26.40 22.41～23.82 11.74～22.36 Water loss rate (%) 14.23～19.55 11.89～14.22 8.49～11.88 <![CDATA[pH 45min ]]> <5.80 or >6.20 6.00～6.20 5.80～6.00 <![CDATA[pH 24h ]]> <5.45 or >5.80 5.60～5.80 5.45～5.60 Muscle fiber diameter (μm) 35.08～38.82 29.48～35.07 25.54～29.47 Muscle fiber density (fibers / mm²) 142.16～147.29 147.30～151.50 151.51～157.13 Total surface area of ​​muscle fibers (μm²) <![CDATA[7×10 4 ~9×10 4 ]]> <![CDATA[5.5×10 4 ~7×10 4 ]]> <![CDATA[4.5×10 4 ~5.5×10 4 ]]> Area of ​​a single muscle fiber (μm²) 967～1184 682～966 512～682 Total number of muscle fibers (units) 50～69 70～89 90～110 Marble pattern Not up to Grade B Grade B (Grades 4-6) Grade A (Levels 1-3)

[0045] By adopting the above technical solution, based on a large sample of muscle data from 29 parts of Hu sheep, a three-level scoring threshold for each indicator was established using the statistical quantile method. This discretized the continuous variable into ordered levels of 1-3-5 points, achieving standardized conversion of indicators with different dimensions. A scoring conversion system based on sheep meat quality data was established, eliminating the influence of dimensions and enabling the fusion calculation of multiple indicators.

[0046] Furthermore, the index score S corresponding to the key metabolite 14 The following criteria are used to determine whether an evaluation condition is met: when the inosinic acid content is higher than 2.5 mg / g, or the total amount of oleic acid, linoleic acid and linolenic acid is higher than 15 mg / g, or the content of any one of maltose, taurine, and carnosine is higher than 120% of the average value of the reference population of the same variety, it is considered as meeting one evaluation condition. When three evaluation conditions are met, a score of 5 is assigned; when two evaluation conditions are met, a score of 3 is assigned; when one evaluation condition is met, a score of 1 is assigned; and when no condition is met, a score of 0 is assigned.

[0047] By adopting the above technical solution, key metabolites (umami substances, healthy fatty acids, and antioxidant peptides) are designated as bonus items. A flexible scoring mechanism based on conditional counting is used, rather than a rigid threshold judgment, to encourage the synergistic improvement of multiple indicators in high-quality meat. The bonus item design reflects the importance of flavor quality while avoiding excessive impact on the overall score balance; the multi-condition progressive design incentivizes the improvement of multi-dimensional meat quality.

[0048] In summary, the present invention has at least one of the following beneficial technical effects:

[0049] (1) This invention constructs a 14-item index system covering six dimensions: sensory quality, texture quality, physicochemical quality, microstructure quality, appearance quality, and flavor quality. It incorporates various parameters such as meat color, tenderness, water retention, pH change, muscle fiber structure, marbling, and key metabolites into a unified evaluation framework. This breaks through the limitations of existing technologies that rely on a single or few indicators (such as using shear force to characterize tenderness only). It can more comprehensively and objectively reflect the true edible quality of mutton and provide a scientific basis for the accurate grading of mutton quality.

[0050] (2) Based on a large sample of muscle data from 29 sites, this invention uses the statistical quantile method to establish a three-level scoring threshold for each indicator (1 point for medium, 3 points for good, and 5 points for excellent). It standardizes and converts continuous variables of different dimensions (such as shear force measured in N, pH as a dimensionless value, and muscle fiber density as an area count) into a unified score, eliminating the incomparability caused by differences in dimensions and numerical ranges, realizing the dimensionless fusion calculation of multi-dimensional indicators, and significantly improving the scientificity, comparability, and generalizability of the evaluation results.

[0051] (3) This invention calculates a comprehensive score using a weighted summation model and classifies the quality into five grades: excellent, good, average, and poor, based on the score range, thus establishing a unified comprehensive scoring standard. This model is applicable to the evaluation of meat quality from different parts of the sheep, such as the longissimus dorsi, biceps femoris, and tail muscles. It overcomes the problem of fragmented evaluation standards caused by differences in parts in existing methods, providing a standardized quality judgment tool for the sheep industry and helping to achieve accurate grading of mutton quality, market pricing, and breed selection.

[0052] (4) This invention incorporates microstructural indicators such as muscle fiber diameter, density, and area, as well as key flavor metabolites such as inosinic acid, unsaturated fatty acids, and carnosine into a comprehensive evaluation model. It reveals the structural basis and metabolic characteristics of meat quality formation at the tissue and molecular levels, making up for the shortcomings of existing evaluation systems that ignore microstructural and metabolite information. This makes the evaluation results closer to the actual edible quality and provides new technical targets for the genetic selection and feeding regulation of high-quality meat sheep.

[0053] (5) This invention sets key metabolites as bonus items and uses conditional counting method for flexible scoring, which not only reflects the importance of flavor quality, but also avoids the excessive influence of metabolite indicators on the overall score balance. At the same time, the multi-condition progressive design encourages producers to improve meat quality from multiple dimensions such as umami substances, healthy fatty acids, and antioxidant peptides, which promotes the standardization of high-quality mutton production and the formation of a high-quality price mechanism. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the appearance quality grade standard for mutton in this invention. Detailed Implementation

[0055] The present invention will be further illustrated below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are only for illustrating the present invention and not for limiting the scope of the present invention. After reading the present invention, any modifications of the present invention in various equivalent forms by those skilled in the art will fall within the scope defined by the appended claims.

[0056] Example 1: Comprehensive evaluation of meat quality of the longissimus dorsi muscle of Hu sheep

[0057] Sample source: Six-month-old female Hu sheep were selected. After slaughtering according to standard slaughtering procedures, the longissimus dorsi muscle was immediately taken and stored at 0℃~4℃ for testing.

[0058] Index determination: Following the method described in this invention, 14 indicators were systematically determined for the longest back muscle.

[0059] The measurement results are shown in Table 1 below.

[0060] Table 1

[0061] Serial Number index Determination methods Measurement results 1 <![CDATA[Flesh color brightness L * > Colorimeter, D65 light source, 2° observation angle, 5 measurements taken and averaged. 38.95 2 <![CDATA[Meat color redness a * > Same as above 12.30 3 <![CDATA[Flesh color yellowness b * > Same as above 4.50 4 Shear force NY / T 1180-2006, Shearing Method 24.50 N 5 Water loss rate NY / T 1333-2007, Pressure Method 13.50% 6 <![CDATA[pH 45min ]]> Portable pH meter, measured 45 minutes post-mortem. 6.55 7 <![CDATA[pH 24h ]]> Portable pH meter, measured 24 hours post-mortem. 5.55 8 muscle fiber diameter Histological methods: HE staining, 400× microscopic observation. 32.00 μm 9 muscle fiber density Image analysis software measurement calculation 149.50 strands / mm² 10 Total area of ​​muscle fibers Image analysis software measurement <![CDATA[4.8×10 4 μm²]]> 11 Area of ​​a single muscle fiber Calculation 700μm² 12 Total number of muscle fibers Image analysis software counting 80 pieces 13 Marble pattern grade Visual inspection scoring method, refer to NY / T 2781-2015 Grade B (Level 4) 14 Key metabolites GC-MS detection Inosinic acid 2.8 mg / g, with a high oleic acid content.

[0062] Scoring Conversion: Based on the scoring criteria in Table 1 above, the measurement results of each indicator are converted into corresponding scores, as shown in Table 2 below.

[0063] Table 2

[0064] index Measurement results Corresponding interval Score <![CDATA[Flesh color brightness L * > 38.95 34.39~41.39 (Medium) 1 <![CDATA[Meat color redness a * > 12.30 11.89~12.53(good) 3 <![CDATA[Flesh color yellowness b * > 4.50 3.99~4.83 (Excellent) 5 Shear force 24.50 N 23.87~26.40 (Medium) 1 Water loss rate 13.50% 11.89~14.22(good) 3 <![CDATA[pH 45min ]]> 6.55 >6.20 (Middle) 1 <![CDATA[pH 24h ]]> 5.55 5.45~5.60 (Excellent) 5 muscle fiber diameter 32.00 μm 29.48~35.07(good) 3 muscle fiber density 149.50 strands / mm² 147.30~151.50(good) 3 Total area of ​​muscle fibers <![CDATA[4.8×10 4 μm²]]> <![CDATA[4.5×10 4 ~5.5×10 4 (Excellent) 5 Area of ​​a single muscle fiber 700 μm² 682~966(good) 3 Total number of muscle fibers 80 pieces 70~89(good) 3 Marble pattern grade Grade B (Level 4) Grade B (Levels 4-6) (Good) 3 Key metabolites Inosinic acid 2.8 mg / g (>2.5 mg / g), with a high oleic acid content. Two conditions must be met 3

[0065] Overall score calculation:

[0066] T=S1+S2+S3+S4+S5+S6+S7+S8+S9+S 10 +S 11 +S 12 +S 13 +S 14 =1+3+5+1+3+1+5+3+3+5+3+3+3+3=42 points.

[0067] Quality grade determination: 35≤T<55, the evaluation grade of the longissimus dorsi muscle sample of this lake sheep is good.

[0068] Results analysis: This sample showed excellent yellowness of flesh color and pH. 24h Normal, the total area of ​​muscle fibers is excellent, but the flesh color brightness is low, the shear force is high (tenderness is average), and the pH is low. 45min The pH level is slightly high (potentially indicating stress or DFD), but key metabolites show good performance. Overall, this sample is of medium to high quality, suitable for fresh sale or low-temperature processing. Improved pre-slaughter management is recommended to optimize the pH profile.

[0069] Example 2: Comprehensive evaluation of meat quality of Hu sheep biceps femoris muscle

[0070] Sample source: Six-month-old female Hu sheep from the same batch as in Example 1 were selected. The biceps femoris muscle was taken immediately after slaughter and stored at 0℃~4℃ for testing.

[0071] Indicator determination: as shown in Table 3 below.

[0072] Table 3

[0073] Serial Number index Determination methods Measurement results 1 <![CDATA[Flesh color brightness L * > Colorimeter, D65 light source, 2° observation angle, 5 measurements taken and averaged. 44.20 2 <![CDATA[Meat color redness a * > Same as above 12.80 3 <![CDATA[Flesh color yellowness b * > Same as above 4.20 4 Shear force NY / T 1180-2006, Shearing Method 18.50 N 5 Water loss rate NY / T 1333-2007, Pressure Method 10.20% 6 <![CDATA[pH 45min ]]> Portable pH meter, measured 45 minutes post-mortem. 5.92 7 <![CDATA[pH 24h ]]> Portable pH meter, measured 24 hours post-mortem. 5.52 8 muscle fiber diameter Histological methods: HE staining, 400× microscopic observation. 27.50μm 9 muscle fiber density Image analysis software measurement calculation 154.20 strands / mm² 10 Total area of ​​muscle fibers Image analysis software measurement <![CDATA[5.0×10 4 μm²]]> 11 Area of ​​a single muscle fiber Calculation 620μm² 12 Total number of muscle fibers Image analysis software counting 95 pieces 13 Marble pattern grade Visual inspection scoring method, refer to NY / T 2781-2015 Grade A (Level 2) 14 Key metabolites GC-MS detection Inosinic acid 3.2 mg / g, total oleic acid, linoleic acid, and linolenic acid 18.5 mg / g, and carnosine content 130% higher than the reference population average.

[0074] Scoring conversion: as shown in Table 4 below.

[0075] Table 4

[0076] index Measurement results Corresponding interval Score <![CDATA[Flesh color brightness L * > 44.20 41.40~45.40(good) 3 <![CDATA[Meat color redness a * > 12.80 12.54~13.48 (Excellent) 5 <![CDATA[Flesh color yellowness b * > 4.20 3.99~4.83 (Excellent) 5 Shear force 18.50 N 11.74~22.36 (Excellent) 5 Water loss rate 10.20% 8.49~11.88 (Excellent) 5 <![CDATA[pH 45min ]]> 5.92 5.80~6.00 (Excellent) 5 <![CDATA[pH 24h ]]> 5.52 5.45~5.60 (Excellent) 5 muscle fiber diameter 27.50μm 25.54~29.47 (Excellent) 5 muscle fiber density 154.20 strands / mm² 151.51~157.13 (Excellent) 5 Total area of ​​muscle fibers <![CDATA[5.0×10 4 μm²]]> <![CDATA[4.5×10 4 ~5.5×10 4 (Excellent) 5 Area of ​​a single muscle fiber 620μm² 512~682 (Excellent) 5 Total number of muscle fibers 95 roots 90-110 (Excellent) 5 Marble pattern grade Grade A (Level 2) Grade A (Levels 1-3) (Excellent) 5 Key metabolites It meets three conditions (inosinic acid > 2.5 mg / g; total amount of the three fatty acids > 15 mg / g; carnosine > 120% of the average value). Meet 3 conditions 5

[0077] Overall score calculation:

[0078] T = 3 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 + 5 = 68 points.

[0079] Quality grade determination: T≥65, the evaluation grade of the biceps femoris muscle sample of this lake sheep is excellent.

[0080] Results Analysis: This sample performed excellently across all 14 indicators, with meat color, tenderness, water retention, pH change, muscle fiber structure, marbling, and key metabolites all reaching superior levels. In particular, it is rich in inosinic acid (a umami substance), high in healthy fatty acids, and exhibits strong carnosine antioxidant activity, demonstrating excellent edible quality and nutritional value. This sample is suitable for high-end fresh sales, chilled delivery, and the development of high-value-added products, and can serve as a benchmark for high-quality mutton production.

[0081] Example 3: Comprehensive evaluation of the meat quality of Hu sheep tail muscle

[0082] Sample source: Healthy 6-month-old female Hu sheep from the same batch as in Example 1 were selected. The tail muscle was taken immediately after slaughter and stored at 0℃~4℃ for testing.

[0083] Indicator determination: as shown in Table 5 below.

[0084] Table 5

[0085] Serial Number index Measurement results 1 <![CDATA[Flesh color brightness L * > 36.50 2 <![CDATA[Meat color redness a * > 11.50 3 <![CDATA[Flesh color yellowness b * > 7.00 4 Shear force 25.80 N 5 Water loss rate 16.80% 6 <![CDATA[pH 45min ]]> 6.35 7 <![CDATA[pH 24h ]]> 5.75 8 muscle fiber diameter 36.50 μm 9 muscle fiber density 144.00 strands / mm² 10 Total area of ​​muscle fibers <![CDATA[8.0×10 4 μm²]]> 11 Area of ​​a single muscle fiber 1050 μm² 12 Total number of muscle fibers 62 roots 13 Marble pattern grade Not up to Grade B (Level 7) 14 Key metabolites Only the inosine monophosphate content of 2.6 mg / g met the bonus requirement; the rest did not.

[0086] Scoring conversion: as shown in Table 6 below.

[0087] Table 6

[0088] index Measurement results Corresponding interval Score (Sᵢ) <![CDATA[Flesh color brightness L * > 36.50 34.39~41.39 (Medium) 1 <![CDATA[Meat color redness a * > 11.50 10.03~11.88 (Medium) 1 <![CDATA[Flesh color yellowness b * > 7.00 5.82~8.46 (medium) 1 Shear force 25.80 N 23.87~26.40 (Medium) 1 Water loss rate 16.80% 14.23~19.55 (Medium) 1 <![CDATA[pH 45min ]]> 6.35 >6.20 (Middle) 1 <![CDATA[pH 24h ]]> 5.75 5.60~5.80(good) 3 muscle fiber diameter 36.50 μm 35.08~38.82 (Medium) 1 muscle fiber density 144.00 strands / mm² 142.16~147.29 (Chinese) 1 Total area of ​​muscle fibers <![CDATA[8.0×10 4 μm²]]> <![CDATA[7×10 4 ~9×10 4 (Chinese) 1 Area of ​​a single muscle fiber 1050 μm² 967~1184 (middle) 1 Total number of muscle fibers 62 roots 50-69 (Medium) 1 Marble pattern grade Not up to Grade B (Level 7) Not up to Grade B (Medium) 1 Key metabolites Meet one condition Meet one condition 1

[0089] Overall score calculation:

[0090] T = 1 + 1 + 1 + 1 + 1 + 1 + 3 + 1 + 1 + 1 + 1 + 1 + 1 + 1 = 16 points.

[0091] Quality grade determination: 15≤T<35, the evaluation grade of the sheep tail muscle sample from this lake is ordinary.

[0092] Results Analysis: The overall quality of this sample was poor, mainly manifested in dark meat color (low brightness, high yellowness), poor tenderness (high shear force), poor water retention (high water loss rate), coarse and low-density muscle fibers, uneven marbling distribution, and insufficient accumulation of metabolites. The tail muscle, as a frequently moved part, naturally has coarse muscle fibers and abundant connective tissue, making its quality inferior to the longissimus dorsi and biceps femoris muscles. This sample is suitable for heavily seasoned processing (such as stewing and braising) or as industrial raw meat, and is not recommended for use as a high-end fresh product.

[0093] Conclusion: The three embodiments above demonstrate that the method of the present invention can effectively distinguish the quality differences of different parts of the same breed (Hu sheep). Through comprehensive evaluation of 14 indicators, it objectively reflects the edible quality characteristics and commercial value of each part of the meat. The biceps femoris muscle in Example 2 scored the highest (Excellent), followed by the longissimus dorsi muscle in Example 1 (Good), and the tail muscle in Example 3 scored the lowest (Ordinary). The evaluation results are highly consistent with actual production experience and consumer perception, proving the scientific nature, accuracy, and practicality of the method of the present invention.

Claims

1. A comprehensive evaluation method for mutton quality, characterized in that, Includes the following steps: (1) Multidimensional index measurement The meat quality evaluation indicators for mutton samples were determined, and the meat quality evaluation indicators included: Sensory quality index: flesh color brightness L * flesh-colored redness a * flesh-colored yellowness b * ; Texture quality indicators: shear force, water loss rate; Physicochemical quality indicators: pH value 45 minutes after slaughter and pH value 24 hours after slaughter; Microstructural quality indicators: muscle fiber diameter, muscle fiber density, total muscle fiber area, area of ​​a single muscle fiber, and total number of muscle fibers; Appearance quality indicators: Marble pattern grade; Flavor quality indicators: key metabolites; (2) Standardized scoring conversion The data obtained from each of the meat quality evaluation indicators are converted into corresponding indicator scores according to a preset scoring standard, wherein S1 to S... 13 The score range is 1 to 5 points, corresponding to three levels: Average, Good, and Excellent. Average is 1 point, Good is 3 points, and Excellent is 5 points. 14 The bonus points for metabolites range from 0 to 5 points. (3) Calculation of comprehensive score Substituting the scores of each indicator into the comprehensive scoring formula, the comprehensive score T for mutton quality is calculated: T=S1+S2+S3+S4+S5+S6+S7+S8+S9+S 10 +S 11 +S 12 +S 13 +S 14 ; In the formula: S1 is the flesh-colored brightness L * The corresponding indicator score; S2 represents the flesh-colored redness a. * The corresponding index score; S3 represents the yellowness of the flesh tone (b). * The corresponding index scores are as follows: S4 is the index score corresponding to shear force; S5 is the index score corresponding to water loss rate; S6 is the index score corresponding to pH value 45 minutes after slaughter; S7 is the index score corresponding to pH value 24 hours after slaughter; S8 is the index score corresponding to muscle fiber diameter; S9 is the index score corresponding to muscle fiber density; S 10 S represents the index score corresponding to the total area of ​​muscle fibers. 11 The index score corresponding to the area of ​​a single muscle fiber; S 12 S represents the index score corresponding to the total number of muscle fibers. 13 S represents the index score corresponding to the marble texture grade. 14 The score represents the indicator value corresponding to the key metabolites; (4) Quality grade classification The quality grades of mutton are classified according to the range of the comprehensive score T: Special grade: T≥65; Excellent grade: 55≤T<65; Good grade: 35≤T<55; Average grade: 15≤T<35; Poor grade: T<15.

2. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The flesh color brightness L * flesh-colored redness a * flesh-colored yellowness b * The measurement method is as follows: a colorimeter is used for measurement, with a D65 standard light source and a 2° observation angle. Measurements are taken continuously 3 to 9 times at the same location, and the flesh color brightness (L) is recorded. * flesh-colored redness a * flesh-colored yellowness b * The average value is taken as the final result.

3. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The shear force was determined in accordance with the standard procedure of NY / T 1180-2006 "Determination of Meat Tenderness - Shear Force Test".

4. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The water loss rate was determined by the pressure method, following the standard procedure of NY / T 1333-2007 "Determination of Meat Quality of Livestock and Poultry".

5. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The method for determining the pH value 45 minutes and 24 hours after slaughter is as follows: a portable pH meter is used for measurement. Before measurement, the meat sample is stored at 0℃~4℃. During measurement, the pH electrode is directly inserted into the muscle. The measurement is repeated 3 times at different parts of the same sample and the average value is taken.

6. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The methods for determining the muscle fiber diameter, muscle fiber density, total muscle fiber area, area of ​​a single muscle fiber, and total number of muscle fibers are as follows: the muscle samples are fixed with 4% paraformaldehyde, dehydrated, embedded, sectioned, and then stained with hematoxylin and eosin. The samples are observed and images are acquired under a microscope at 400x magnification. The muscle fiber diameter, total muscle fiber area, and number of muscle fibers are measured using image analysis software, and the area of ​​a single muscle fiber and the muscle fiber density are calculated accordingly.

7. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The marble texture grade is evaluated using a visual scoring method. Under natural light or standard light source conditions, the cross-section of the muscle is compared with a standard marble texture scoring board. The grade is determined based on the uniformity and obviousness of fat distribution, with grades 1-3 being grade A, grades 4-6 being grade B, and grades 6 and above being below grade B.

8. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: The key metabolites were detected using metabolomics methods. Gas chromatography-mass spectrometry or gas chromatography-olfaction was used to perform qualitative and quantitative analysis of flavor-related metabolites in the samples. The detected metabolites included maltose, taurine, carnosine, inosinic acid, oleic acid, linoleic acid, and linolenic acid.

9. The method for comprehensive evaluation of mutton quality according to claim 1, characterized in that: In step (2), the data measured for each meat quality evaluation indicator are converted into corresponding indicator scores according to a preset scoring standard. The conversion standard is as follows:

10. The comprehensive evaluation method for mutton quality according to any one of claims 1-9, characterized in that: The index score S corresponding to the key metabolite 14 The following criteria are used to determine whether an evaluation condition is met: when the inosinic acid content is higher than 2.5 mg / g, or the total amount of oleic acid, linoleic acid and linolenic acid is higher than 15 mg / g, or the content of any one of maltose, taurine, and carnosine is higher than 120% of the average value of the reference population of the same variety, it is considered as meeting one evaluation condition. When three evaluation conditions are met, a score of 5 is assigned; when two evaluation conditions are met, a score of 3 is assigned; when one evaluation condition is met, a score of 1 is assigned; and when no condition is met, a score of 0 is assigned.

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