Method for determining the maturity time of mutton after slaughter based on the degree of myofibrillar protein oxidation

Abstract

The present invention discloses a method for determining the post-slaughter maturation time of mutton based on the degree of myofibrillar protein oxidation. The method uses myofibrillar protein as an oxidation index with obvious differences in the post-slaughter maturation process, thereby determining the post-slaughter maturation time of meat according to the degree of myofibrillar protein oxidation in the meat. The present invention determines the post-slaughter maturation time of mutton for the first time, provides a basis for reflecting the degree of myofibrillar protein oxidation in the post-slaughter maturation process of mutton, and can determine the post-slaughter maturation time of mutton according to the degree of myofibrillar protein oxidation. It is a new meat quality evaluation method, which is conducive to creating more profits for meat companies and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of meat product quality detection, and in particular relates to a method for determining the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation. Background Art

[0002] Meat is one of the important foods in people's lives. With the improvement of people's living standards, people's demand for meat is not only based on quantity, but also on the quality of meat. In order to improve consumer acceptance, mutton needs to be matured in a low-temperature refrigerated environment after slaughter to improve appearance and palatability. During its maturation process, it is often accompanied by the oxidation of muscle fibers, especially the oxidation of protein in fresh lean meat, which leads to changes in mutton quality. Protein oxidation is currently one of the hot spots in the study of changes in meat maturation and storage. The protein content in fresh lean meat of goats is about 25%, which is easily attacked by reactive oxygen species, causing group changes and structural damage, leading to polypeptide chain breakage and the formation of intermolecular polymers. The hydroxyl groups of amino acid side chains form carbonyl compounds due to oxidation, and the sulfhydryl groups form disulfide bonds due to oxidation, which damage the spatial conformation of myofibrillar proteins and sarcoplasmic proteins, resulting in weakened or lost protein function.

[0003] Goat meat is not only a traditional meat used for both food and medicine, but also one of the important red meats in the diet. It has a long history of consumption in countries around the world. In China, goat meat is a delicacy. Compared with other animals, goat meat is low in fat, high in protein, and rich in various nutrients. The output value of mutton in my country has been growing steadily in recent years, and the market demand is large. The post-slaughter maturation stage is an important step in improving the quality of meat. Therefore, it is of great practical significance to determine a method for accurately identifying the post-slaughter maturation time of mutton. In addition, protein oxidation in the post-slaughter maturation stage of mutton has a great impact on its meat quality. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation. The method can determine the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation.

[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present invention consists of the following steps:

[0006] (1) Immediately after slaughter, the longissimus dorsi muscles on both sides of intact male goats were collected at the slaughterhouse. After removing visible fat and connective tissue, the longissimus dorsi muscles were placed in an ice box at -2 to 1°C and transported to the laboratory within 5 hours. The meat samples were matured in plastic bags at 4°C for 0 hours, 12 hours, 24 hours, and 48 hours respectively.

[0007] (2) taking the meat samples matured at different times in step (1) and cutting them into small pieces, extracting myofibrillar protein, and freeze-drying the extracted myofibrillar protein at -60 to -50°C;

[0008] (3) mixing the freeze-dried myofibrillar protein powder obtained in step (2) with fully dried potassium bromide, grinding the mixture into a fine powder, and pressing the mixture into a tablet, and measuring the Fourier infrared spectrum;

[0009] (4) Use PeakFit software to process the FT-IR spectrum from 1700 to 1600 cm in step (3). -1 The spectral data of the amide I region of the band were subjected to baseline correction, smoothing and curve fitting, and the content ratio of various myofibrillar protein secondary structures was obtained by dividing the peak area of ​​each myofibrillar protein secondary structure by the sum of the peak areas of all myofibrillar protein secondary structures;

[0010] (5) If the β-fold content ratio of myofibrillar protein secondary structure is 15%-20%, the α-helix content ratio is 25%-30%, the β-turn content ratio is 18%-22%, and the random coil content ratio is 30%-33%, it means that the mutton matures within 24 hours after slaughter; if the β-fold content ratio of myofibrillar protein secondary structure is 20%-30%, the α-helix content ratio is 30%-40%, the β-turn content ratio is 22%-31%, and the random coil content ratio is 0-5%, it means that the mutton matures more than 24 hours but within 48 hours after slaughter;

[0011] (6) Take a mutton sample at the post-slaughter maturity stage to be tested, and perform testing according to the methods of steps (2) to (5) to determine the post-slaughter maturity time of the mutton sample.

[0012] In the above step (2), the method for extracting myofibrillar protein is: adding the meat sample to a solution containing 100 mmol / L NaCl and 2 mmol / L MgCl 25-8 mL of phosphate buffer with a pH of 7.0-7.5 and 1 mmol / L EDTA-2Na was added to each gram of meat sample, and homogenized at 10000-12000 r / min in an ice bath for 1-2 min; after homogenization, centrifuge at 4°C and 2500-3000×g for 15-20 min, remove the supernatant, add the above phosphate buffer, repeat the centrifugation 2-3 times, and add 100 mmol / L The pH value of NaCl in phosphate buffer solution is 6.25-6.5, homogenized at 10000-12000 r / min in an ice bath for 1-2 min, then centrifuged at 4°C and 2500-3000×g for 15-20 min. After removing the supernatant, phosphate buffer solution with a pH value of 6.0 is added, homogenized at 10000-12000 r / min in an ice bath for 1-2 min, the homogenate is filtered through double gauze to remove connective tissue, and centrifuged at 4°C and 2500-3000×g for 15-20 min. The resulting precipitate is myofibrillar protein.

[0013] In the above step (3), the freeze-dried myofibrillar protein powder of step (2) is preferably mixed with fully dried potassium bromide in a mass ratio of 1:80 to 120, ground into powder, and then pressed into tablets to measure the Fourier infrared spectrum.

[0014] In the above step (4), the Fourier transform infrared spectroscopy measurement conditions are: 4000-400cm -1 Scan 32 to 40 times within the range, with a resolution of 2 cm -1 .

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] 1. The present invention is the first to determine the post-slaughter maturity time of mutton by the degree of myofibrillar protein oxidation.

[0017] 2. The present invention can determine the maturity time of meat after slaughter based on the degree of myofibrillar protein oxidation, providing a new method for evaluating meat quality.

[0018] 3. The present invention has broad application prospects and helps us understand the protein changes that lead to the decline of meat quality during the post-slaughter maturation process of meat.

[0019] 4. The present invention is of great significance for the quality control of meat during the post-slaughter maturation process, and is conducive to creating more profits for meat companies. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a Fourier transform infrared spectrum of myofibrillar protein in mutton at different maturation times after slaughter measured in Example 1.

[0021] Figure 2 is based on Figure 1 The obtained ratio diagram of the secondary structure content of myofibrillar protein in mutton at different maturation times after slaughter. DETAILED DESCRIPTION

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0023] Example 1

[0024] 1. Nine healthy male Xinjiang goats aged 1.5 years (uncastrated) were selected from the same farm and all animals were slaughtered using the standard procedures of a commercial slaughterhouse. Immediately after slaughter, the longissimus dorsi muscles on both sides were collected, and after removing visible fat and connective tissue, the longissimus dorsi muscles were placed in an ice box at -2 to 1°C and transported to the laboratory within 5 hours. The meat samples were matured in plastic bags at 4°C for 0 hours, 12 hours, 24 hours, and 48 hours.

[0025] 2. Take the meat samples from step 1 and cut them into small pieces. Take 5g of the meat and add them into 30mL of 100mmol / L NaCl and 2mmol / L MgCl. 2 and 1mmol / L EDTA-2Na in a phosphate buffer solution with a pH value of 7.0, homogenized at 10000r / min in an ice bath for 1min; after homogenization, centrifuged at 4°C and 2500×g for 15min, removed the supernatant, added 100mL of the above phosphate buffer solution, and repeated the centrifugation 3 times; then added 100mL of phosphate buffer solution with a pH value of 6.25 containing 100mmol / L NaCl, homogenized at 10000r / min in an ice bath for 1min; then centrifuged at 4°C and 2500×g for 15min, removed the supernatant, added 100mL of phosphate buffer solution with a pH value of 6.0, and homogenized at 10000r / min in an ice bath for 1min. The homogenate was filtered through double gauze to remove connective tissue, centrifuged at 4°C and 2500×g for 15min, and the resulting precipitate was freeze-dried at -50°C to obtain myofibrillar protein powder.

[0026] 3. Mix the myofibrillar protein powder and fully dried potassium bromide in a mass ratio of 1:100, grind them into fine pieces, and then press them into tablets. Measure the Fourier infrared spectrum. The infrared spectrum of each sample is between 4000 and 400 cm -1 Scan 32 times within the range with a resolution of 2cm -1 The results of the measurement are shown in Figure 1 .

[0027] 4. Use PeakFit software version 4.12 to process the FT-IR spectrum obtained in step 3 from 1700 to 1600 cm -1The spectral data of the amide I region of the band were baseline corrected, smoothed and curve fitted, and the content ratio of various myofibrillar protein secondary structures was obtained by dividing the peak area of ​​each myofibrillar protein secondary structure by the sum of the peak areas of all myofibrillar protein secondary structures.

[0028] 5. If the β-fold content ratio of myofibrillar protein secondary structure is 15% to 20%, the α-helix content ratio is 25% to 30%, the β-turn content ratio is 18% to 22%, and the random coil content ratio is 30% to 33%, it means that the mutton matures within 24 hours after slaughter; if the β-fold content ratio of myofibrillar protein secondary structure is 20% to 30%, the α-helix content ratio is 30% to 40%, the β-turn content ratio is 22% to 31%, and the random coil content ratio is 0% to 5%, it means that the mutton matures more than 24 hours but within 48 hours after slaughter. The content ratio determination results of myofibrillar protein secondary structure at different maturation times are as follows: Figure 2 As shown, at 0h after slaughter, the proportions of β-sheet, α-helix, β-turn and random coil were 18%, 30%, 19.48% and 32.66% respectively; at 12h after slaughter, the proportions of β-sheet, α-helix, β-turn and random coil were 19.14%, 29.34%, 21.09% and 30.43% respectively; at 24h after slaughter, the proportions of β-sheet, α-helix, β-turn and random coil were 19.83%, 28.28%, 21.15% and 30.74% respectively; at 48h after slaughter, the proportions of β-sheet, α-helix, β-turn and random coil were 28.5%, 39.23%, 30.73% and 0 respectively. The test results all met the above criteria.

[0029] 6. Take a mutton sample at the post-slaughter maturity stage to be tested, and perform testing according to the methods in steps 2 to 5 to determine the post-slaughter maturity time of the mutton sample.

Claims

1. A method for determining the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation, Features The method consists of the following steps: (1) Immediately after slaughter, the longissimus dorsi muscles on both sides of intact male goats were collected at the slaughterhouse. After removing visible fat and connective tissue, the longissimus dorsi muscles were placed in an ice box at -2 to 1°C and transported to the laboratory within 5 hours. The meat samples were matured in plastic bags at 4°C for 0 hours, 12 hours, 24 hours, and 48 hours respectively. (2) taking the meat samples matured at different times in step (1) and cutting them into small pieces, extracting myofibrillar protein, and freeze-drying the extracted myofibrillar protein at -60 to -50°C; (3) mixing the freeze-dried myofibrillar protein powder obtained in step (2) with fully dried potassium bromide, grinding the mixture into a fine powder, and pressing the mixture into a tablet, and measuring the Fourier infrared spectrum; (4) Use PeakFit software to process the FT-IR spectrum from 1700 to 1600 cm in step (3). -1 The spectral data of the amide I region of the band were subjected to baseline correction, smoothing and curve fitting, and the content ratio of various myofibrillar protein secondary structures was obtained by dividing the peak area of ​​each myofibrillar protein secondary structure by the sum of the peak areas of all myofibrillar protein secondary structures; (5) If the β-fold content ratio of myofibrillar protein secondary structure is 15%-20%, the α-helix content ratio is 25%-30%, the β-turn content ratio is 18%-22%, and the random coil content ratio is 30%-33%, it means that the mutton matures within 24 hours after slaughter; if the β-fold content ratio of myofibrillar protein secondary structure is 20%-30%, the α-helix content ratio is 30%-40%, the β-turn content ratio is 22%-31%, and the random coil content ratio is 0-5%, it means that the mutton matures more than 24 hours but within 48 hours after slaughter; (6) Take a mutton sample at the post-slaughter maturity stage to be tested, and perform testing according to the methods of steps (2) to (5) to determine the post-slaughter maturity time of the mutton sample.

2. The method for determining the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation according to claim 1, Features: In step (2), the myofibrillar protein is extracted by adding the meat sample to a solution containing 100 mmol / L NaCl and 2 mmol / L MgCl 2 5-8 mL of phosphate buffer with a pH of 7.0-7.5 and 1 mmol / L EDTA-2Na was added to each gram of meat sample, and homogenized at 10000-12000 r / min in an ice bath for 1-2 min; after homogenization, centrifuge at 4°C and 2500-3000×g for 15-20 min, remove the supernatant, add the above phosphate buffer, repeat the centrifugation 2-3 times, and add 100 mmol / L The pH value of NaCl in phosphate buffer solution is 6.25-6.5, homogenized at 10000-12000 r / min in an ice bath for 1-2 min, then centrifuged at 4°C and 2500-3000×g for 15-20 min. After removing the supernatant, phosphate buffer solution with a pH value of 6.0 is added, homogenized at 10000-12000 r / min in an ice bath for 1-2 min, the homogenate is filtered through double gauze to remove connective tissue, and centrifuged at 4°C and 2500-3000×g for 15-20 min. The resulting precipitate is myofibrillar protein.

3. The method for determining the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation according to claim 1, Features: In step (3), the freeze-dried myofibrillar protein powder of step (2) is mixed with fully dried potassium bromide in a mass ratio of 1:80 to 120, ground into powder, and then pressed into tablets, and the Fourier infrared spectrum is measured.

4. The method for determining the post-slaughter maturity time of mutton based on the degree of myofibrillar protein oxidation according to claim 1, Features: In step (3), the Fourier transform infrared spectroscopy measurement conditions are: 4000-400cm -1 Scan 32 to 40 times within the range, with a resolution of 2 cm -1 .

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