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Effect of Nitric Oxide Synthetase Inhibitor on Yak Meat Quality During Post-Mortem Aging     LI XueRu,SHI XiXiong,WANG JianZhong,ZHANG PanGao,TIAN Zhu,HAN Ling Scientia Agricultura Sinica   2020,53(8 ):1617 -1626. DOI:10.3864/j.issn.0578-1752.2020.08.011 Abstract  （494） HTML （14） PDF（pc） （452KB）（597） Save 【Objective】The effect of nitric oxide on the yak meat quality of post-mortem was studied to provide a theoretical basis for improving the yak meat quality. 【Method】 The Longissimus Doris (LD) muscles of 3-5-year-old castrated Gannan yak were used as the material. After removing the fascia and fat, the LD was cut into uniform-sized slices (8 cm × 8 cm), and uniformly pierced with a 20 G needle. Subsequently, a part of each sample were immersed at deionized water (as the control group), and the remainders of the muscle samples were immersed at 1, 10, and 100 mmol L -1nitric oxide synthase (NOS) inhibitor (N-nitro-L-arginine methyl ester hydrochloride) then aged at 4℃ for 0, 1, 3, 5, and 7 d, which served as treatment group. Then, the NOS activity, the content of nitric oxide, sulfhydryl, and carbonyl, the myofibrillar fragmentation index (MFI), pH and color were analyzed. 【Result】 The NOS activity and nitric oxide content of the meat sample in NOS inhibitor group were significantly decreased; at 7 d, the NOS activity of each NOS inhibitor treatment group was 30.9%, 43.6% and 74.7% lower than that of the control group, respectively. Nitric oxide levels were 4.7%, 12.5%, and 21.5% lower than the control group, respectively. The pH in the treatment group significantly decreased; at 7d, the treatment groups were 0.8%, 5.7%, and 15.2% lower than the control group, respectively. The 10 and 100 mmol L -1 NOS inhibitor treatment groups were significantly different compared with the control group. The treatment significantly reduced the carbonyl content of the yak meat; at 7 d, treatment groups were 4.1%, 19.0%, and 22.2% lower than the control group, respectively. The MFI of the treatment group increased significantly; at 7 d, treatment groups were 31.1%, 23.3%, and 9.6% lower than the control group, respectively. The total sulfhydryl content was significantly increased in the treatment groups; at 7d, the control group was 3.2%, 3.7%, and 2.7% lower than the NOS inhibitor treatment groups. In addition, the treatment significantly reduced the a* value and significantly increased the L* value of samples; at 7d, the a* values of each treatment groups were 7.1%, 40.2%, and 30.7% lower than the control group, respectively. The L* value of treatment groups were 1.1%, 2.0%, and 1.1% higher than the control group, respectively. 【Conclusion】 Nitric oxide promoted protein oxidation of yak meat post-mortem, inhibited tenderness of yak meat, decreased L * value and increased a * value, which adversely affected the quality of yak meat during post-mortem aging; NOS inhibitor inhibited NOS activity in muscle. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Selection of Water-Soluble Compounds by Characteristic Flavor in Chahua Chicken Muscles Based on Metabolomics     ZHAO WenHua,WANG GuiYing,XUN Wen,YU YuanRui,GE ChangRong,LIAO GuoZhou Scientia Agricultura Sinica   2020,53(8 ):1627 -1642. DOI:10.3864/j.issn.0578-1752.2020.08.012 Abstract  （472） HTML （22） PDF（pc） （2232KB）（537） Save 【Objective】 The biomarkers in the chest and thigh muscles of Chahua Chicken before and after heat treatment were screened by using metabolomics combined with multivariate statistical methods, the aim of this study was to screen and characterize water-soluble compounds in different parts of Chahua Chicken, so as to provide scientific and theoretical basis for establishing evaluation standards of high-quality local chicken.【Method】Using liquid chromatography-quadrupole electrostatic field orbitrap mass spectrometry (LC-Q-Exactive-MS) and 300-day-old Yunnan native Chahua Chicken, the water-soluble compounds in the chest and thigh muscles before and after heat treatment were tested. Also, the spectrum was identified based on the network database Metlin, the relative content of each substance were calculated by the concentration of DL-o-Chlorophenylalanine, and the multivariate statistical analysis was used to detect substances. The relationship model between metabolite expression and sample groups was established by using orthogonal partial least squares discrimination analysis (OPLS-DA) to predict the sample category. The representative biomarkers was screened by S-plot to determine whether the model had over-fitting by observing the slope of the line of the 200 test plots of the permutations, and to discriminate the influence intensity and interpretation ability of each metabolite expression pattern on the classification and discrimination of each group of samples by the variable important of the projection (VIP). Therefore, the study achieved the purpose of screening markers: combining the calculation for Taste Activity Value (TAV) by relative content results with sensory evaluation results evaluate the characteristic flavor of Chahua Chicken muscles.【Result】The results showed that 106 species and 43 metabolites were detected in the chest and thigh muscles of Chahua Chicken before and after heat treatment in the positive ion mode and the negative ion mode, including amino acids, vitamins, nucleotides, organic acids, and fatty acids. Among them, creatine, carnosine, amino acid, and nucleotide were water-soluble compounds which had differences between before and after heat treatment of Chahua Chicken muscles, which could be used as a biomarker for the characteristics of the tribute. The TAV value results showed that the largest TAV value in the chest muscles was gamma-aminobutyric acid (TAV=23.00), and the followed by Histidine (TAV=1.14). The highest TAV value in the thigh muscles was gamma-aminobutyric acid (TAV=37.50), and the followed by Betaine (TAV=2.00). Through sensory evaluation, it was found that the overall taste of the chest muscles and thigh muscles was mainly sweet and umami.【Conclusion】After metabolomics analysis, the characteristic taste substances were obtained, and through the taste theory and sensory evaluation values, the study determined that the taste of the breast and leg muscles of Chahua chicken was mainly sweet and fresh meat, and the leg muscles were superior to the chest muscles. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Improving Quality and Delaying Oxidation in Goat Meat Refrigeration by Polyphenols from Thinned Young Kiwifruit     GU MingHui,LIU YongFeng,SHEN Qian,QIAO ChunYan Scientia Agricultura Sinica   2020,53(8 ):1643 -1654. DOI:10.3864/j.issn.0578-1752.2020.08.013 Abstract  （426） HTML （18） PDF（pc） （741KB）（510） Save 【Objective】The objective of this study was to research the function of thinned young kiwifruit discarded in “Blossom and Fruit Thinning” in goat meat cold storage and to provide useful information for lengthening the shelf life of refrigerated goat meat, maintaining goat meat quality and delaying the oxidation of goat meat. 【Method】The goat meat was sprayed with 1 mg·mL -1 polyphenols from thinned young kiwifruit, epicatechin and potassium sorbate solution, control group was treated with distilled water, then preserved at 4℃ refrigerator in ziplock bags. The microstructure, texture characteristics, pH, fatty acid content, thiobarbituric acid reactive substance assay (TBARS) and volatile base nitrogen (TVB-N) of goat meat were measured during 8 d refrigeration. 【Result】As time went on, the goat meat microstructure of the four groups became tender and muscle fibers were gradually loosened and relaxed. During the cold storage period, the hardness of goat meat in four groups showed a decreasing trend. In the first 3 days, the hardness values were ranked as follows: potassium sorbate group> epicatechin group> blank group> thinned kiwifruit polyphenol group. After 5 days, the hardness values of the groups became similar. At the end of cold storage, the hardness of the thinned kiwifruit polyphenol group, epicatechin group, potassium sorbate group and blank group decreased by 50.52%, 41.73%, 39.63% and 51.56%, respectively. The springing of goat meat in four groups was first increased and then remained stable. In the first 3 days, the springing value of the polyphenols group was lower than that of the other three groups. At the end of cold storage, the springing values of the thinned kiwifruit polyphenol group, epicatechin group, potassium sorbate group and blank group were reduced by 45.23%, 33.34%, 44.64% and 41.31%, respectively; the chewiness of goat meat in four groups showed a downward trend as a whole, and the chewiness of the thinned kiwifruit polyphenol group, epicatechin group, potassium sorbate group and blank group decreased by 72.06%, 61.46%, 62.00% and 67.37%, respectively. The cohesiveness and resilience of the thinned kiwifruit polyphenol group were relatively stable, and the cohesiveness of the potassium sorbate group was in the same trend. With the prolongation of time, the content of polyunsaturated fatty acids (PUFA) in the thinned kiwifruit polyphenol group was remained stable, and the PUFA content of epicatechin and potassium sorbate groups was peaked at 6 d, while the content of blank group showed a downward trend. At the end, the PUFA content of thinned kiwifruit polyphenol group was 1.11, 1.40 and 1.86 times of the epicatechin, potassium sorbate and blank groups, respectively. The content of monounsaturated fatty acid (MUFA) in the thinned kiwifruit polyphenol group was increased first and then decreased. The highest value of MUFA content in the thinned kiwifruit polyphenol group was reached in 4 d, while other groups showed a downward trend. At the end of cold storage, the MUFA content of thinned kiwifruit polyphenol group was 1.10, 1.17 and 1.21 times of the epicatechin, potassium sorbate and blank groups, respectively. The content of the saturated fatty acids (SFA) and total fatty acids (TFA) in the thinned kiwifruit polyphenol, epicatechin and blank groups was decreased, while the content of potassium sorbate group decreased first and then stabilized. The TFA content of thinned kiwifruit polyphenol group was higher than that of the other three groups in 2-4 days. The TFA content of the thinned kiwifruit polyphenol and epicatechin groups was higher than that of the other two groups in 4-8 days. The TBARS values of goat meat in four groups decreased firstly after storage, and after 3 days, their values were ranked as follows: thinned kiwifruit polyphenol group < epicatechin group < blank group < potassium sorbate group. At the end of cold storage, the TBARS values of thinned kiwifruit polyphenol group were 90.84%, 56.83% and 59.45% of the epicatechin, potassium sorbate and blank groups, respectively. With the prolongation of time, the TVB-N value of goat meat gradually increased while the pH increased first and then stabilized. Compared with the epicatechin, potassium sorbate and blank groups, the chilled time of goat meat in the thinned kiwifruit polyphenol group was extended by 0.48, 1.13 and 1.61 d, respectively. 【Conclusion】Thinned young kiwifruit polyphenols could prolong the shelf life of meat and improve meat quality by delaying the rise of goat meat pH, inhibiting lipid oxidation, slowing down PUFA oxidation, and helping maintain cohesiveness and resilience stability. Table and Figures丨 Reference丨 Related Articles丨 Metrics

Prediction of Center Temperature of Beijing Roast Duck Based on Quality Index     LIU YanXia,WANG ZhenYu,ZHENG XiaoChun,ZHU YaoDi,CHEN Li,ZHANG DeQuan Scientia Agricultura Sinica   2020,53(8 ):1655 -1663. DOI:10.3864/j.issn.0578-1752.2020.08.014 Abstract  （393） HTML （17） PDF（pc） （499KB）（624） Save 【Objective】 The aim of this study was to solve the problem in detecting center temperature of Beijing roast duck during traditional Gua-lu roasting accurately and timely. 【Method】 The prediction models of center temperature were established by using multiple linear regression, partial least-squares regression, support vector regression and artificial neural network according to the quality indicators. 【Result】 The results showed that the models were effective to identify center temperature of Beijing roast duck by L*, a*, b*, deoxymyoglobin, oxymyoglobin, metmyoglobin, moisture and fat content, as well as protein secondary structure of duck breast. The R 2C of multiple linear regression and partial least-squares regression were 0.9543 and 0.9384, and SEC of 5.8205℃ and 6.7634℃, respectively. The prediction effect of multiple linear regression was better than partial least-squares regression, while the prediction model of support vector regression was superior to artificial neural network. R 2C and R 2CV of support vector regression were 0.9837 and 0.9496, SEC and SECV were 3.5215℃ and 6.1236℃, respectively, so the support vector regression was the best prediction model of center temperature. The R 2V of the verified models of support vector regression was 0.9748, and the SEV was 5.5204℃. The model obtained by support vector regression together with the modeling results could accurately predict the center temperature of Beijing roast duck. 【Conclusion】 The color, myoglobin, water content, fat content and protein secondary structure of the breast of Beijing roast duck could effectively identify the central temperature. The SVR model was the most accurate prediction model for the center temperature. Table and Figures丨 Reference丨 Related Articles丨 Metrics