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In order to clarify the mechanism underlying the regulatory effect of oxidative phosphorylation (OXPHOS) on the color stability of Tan sheep meat during postmortem storage, the M. longissimus dorsi of 6-month-old Tan sheep was stored at 4 ℃ after slaughter and evaluated for the activity of endogenous antioxidant enzymes and the content of reactive oxygen species (ROS) after 0, 4 and 8 days. Proteomics based on isobaric tags for relative and absolute quantitation (iTRAQ) was used to study protein expression in Tan sheep meat at different storage times. The results showed that during 0–8 days of storage, the activity of endogenous antioxidant enzymes showed a decreasing trend (P < 0.05), and the ROS content significantly increased with storage time (P < 0.05). Eight differentially expressed proteins were identified as the core proteins affecting the color stability of Tan sheep meat, namely ATP synthase F1 subunit alpha (ATP5A1), ATP synthase peripheral stalk subunit OSCP (ATP5O), ATP synthase peripheral stalk subunit D (ATP5H), cytochrome c oxidase subunit II (COX2), cytochrome c oxidase subunit 5A (COX5A), succinate dehydrogenase complex iron sulfur subunit B (SDHB), ADP/ATP translocase 1 (SLC25A4), and cytochrome c (CYCS). These proteins affected the color stability of Tan sheep meat mainly through the energy metabolism and redox processes. These results indicated that the loss of the activity of antioxidant enzymes in Tan sheep meat during postmortem storage caused the accumulation of ROS, which led to the destruction of the mitochondrial integrity of muscle cells and aberrant gene expression of complex subunits such as ATP5A1, ATP5O, ATP5H, COX2, COX5A, SDHB, SLC25A4 and CYCS in the oxidative phosphorylation pathway, thus contributing to changes in the structure and function of mitochondrial complexes and blockage of the oxidative phosphorylation process, and ultimately affecting the color stability of Tan sheep meat.

The hindleg meat of Tan sheep was injected postmortem with the phosphoinositide 3-kinase (PI3K) inhibitor LY294002 at a concentration of 10 μmol/L and stored at 4 ℃. After 0, 2, 4, 6 and 8 days, the protein expression of PI3K and protein kinase B (AKT) was analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot so as to verify whether the PI3K/AKT signaling pathway was effectively inhibited. Meanwhile, we analyzed changes in energy factors, oxidative stress levels, the degree of mitochondrial damage and cysteine aspastic acid-specific protease 3 (caspase-3) activity in order to explore the mechanism by which the PI3K/AKT signaling pathway induces the pathways of cell apoptosis during chilled storage of Tan sheep meat. The results showed that during storage, the protein expression levels of PI3K and AKT showed a decreasing trend, indicating that LY294002 inactivated the PI3K/AKT signaling pathway. Compared with the control group, LY294002 treatment significantly reduced mitochondrial ATP, glycogen content, succinate dehydrogenase (SDH) and citrate synthase (CS) activity (P < 0.05), gradually increased mitochondrial reactive oxygen species (ROS) levels, elevated the levels of oxidative stress and the opening of mitochondrial permeability transition pore (MPTP), significantly decreased membrane potential (P < 0.05), and significantly augmented the activity of caspase-3 (P < 0.05), indicating that the PI3K/AKT signaling pathway mediates the activation of downstream caspase-3 by promoting the production of ROS to interact with PI3K, damaging the structure and function of mitochondria, leading to the opening of MPTP and decreased membrane potential, and ultimately inducing cell apoptosis.

In order to elucidate the relationship between the oxidative phosphorylation and the color stability of Tan sheep meat during postmortem storage, the changes in the color stability and oxidative phosphorylation of the Longissimus dorsi of 6-month-old Tan sheep were determined after 0, 1, 2, 3, 4, 6 and 8 days of postmortem storage at 4 ℃. The results showed that L*, a* and b* values increased first and then decreased during 0–8 days of storage (P < 0.05), and so did R630/R580 ratio (P < 0.05). The relative content of metmyoglobin (MetMb) showed a decreasing and then increasing trend (P < 0.05), whereas the relative content of oxymyoglobin (OxyMb) exhibited the opposite trend (P < 0.05), and the relative content of deoxymyoglobin (DeoMb) showed a decreasing trend (P < 0.05). Mitochondrial membrane permeability significantly increased (P < 0.05), and mitochondrial membrane potential significantly decreased (P < 0.05). The activity of mitochondrial complex I, II, III and IV significantly decreased (P < 0.05), while the activity of complex V significantly increased (P < 0.05). Reactive oxygen species (ROS) levels significantly increased (P < 0.05). The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) significantly decreased (P < 0.05). Catalase (CAT) activity first increased and then decreased (P < 0.05). The contents of ATP, ADP and AMP significantly decreased (P < 0.05). The relative contents of MetMb, OxyMb and DeoMb and meat color parameters were significantly correlated with oxidative phosphorylation. The above results indicate that the failure of endogenous antioxidant enzymes in Tan sheep meat during postmortem storage led to excessive ROS production in myocytes, which damaged the integrity of mitochondria, and then affected the activities of enzymes related to mitochondrial oxidative phosphorylation and consequently the activity of MetMb reductase in myocytes, which resulted in the failure of MetMb reduction, thereby leading to deterioration of the color stability of Tan sheep meat.

Mutton is a high-quality meat with high nutritional value. However, the typical species-specific flavor (odor) of mutton affects its quality and limits its consumer acceptance. Studies have shown that the major substances that cause mutton odor are 4-alkyl branched fatty acids, 3-methylindole, 4-methylphenol, stearic acids, and amino acids. The composition and formation pathway of mutton odor substances are complex and influenced by various factors such as nutrition, feeding system, variety, sex, age, and tissue position, so it is difficult to reduce mutton odor. Therefore, this article reviews the sources and formation mechanisms of mutton odor substances, the factors affecting the formation of mutton odor substances, and deodorization methods, which will provide a basis for scientifically regulating the flavor of mutton and its products.

In this study, the Longissimus dorsi muscle of Qinchuan beef stored at 4 ℃ after slaughter was determined for its quality indicators, energy level and proteasome activity. Meanwhile, differentially expressed proteins (DEPs) associated with proteasomes were identified. Bioinformatics methods were used to analyze the response mechanism of proteasomes to the quality and energy metabolism of postmortem beef. The results showed that pH decreased and then increased with increasing storage time, b* and myofibrillar fragmentation index (MFI) increased, L*, a*, centrifugal loss, cooking loss and shear force increased first and then decreased, the contents of the basic energy substances ATP, ADP and AMP decreased, and the relative activity of the 20S proteasome decreased significantly (P < 0.05). The correlation analysis showed that the activity of the 20S proteasome was significantly negatively correlated with b* (P < 0.05), positively correlated with ADP content (P < 0.05), positively correlated with AMP content (P < 0.01), and negatively correlated with MFI (P < 0.01), indicating a close relationship between proteasome activity and energy metabolism as well as beef quality. Using 4D label-free quantitative (LFQ) proteomics, eight differentially expressed proteasome subunits and 27 DEPs were identified. Gene Ontology (GO) annotation analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that these proteasome subunits and related DEPs had molecular functions such as endopeptidase activity, actin binding, microfilament motor activity, and were involved in biological processes such as ubiquitin-dependent proteolytic metabolism, skeletal muscle contraction, muscle contraction, and glycolysis, thus causing changes in the quality of Qinchuan beef. During the early postmortem period, the proteasomes regulated the biological pathways by consuming energy substances to catabolize proteins, and during the later period, when the energy substances were depleted, the proteasomes catabolized proteins in postmortem beef through the energy provided by glycolysis and non-ATP-dependent proteasome subunits, which eventually affected the quality of Qinchuan beef.

In order to explore the effects of basigin (BSG) on the mitogen activated protein kinase (MAPK) signaling pathway and apoptosis in Qinchuan cattle muscle during postmortem maturation, the changes in BSG and related differentially expressed proteins were analyzed by 4D-label free quantification (4D-LFQ). The BSG inhibitor tunicamycin was injected into the longissimus dorsi of Qinchuan cattle after slaughter, and the expression levels of key proteins in the MAPK signaling pathway during storage at 4 ℃ were determined by Western blotting. An apoptosis detection kit was used to determine the change in the activity of caspase-3. The results showed that the expression of BSG increased first and then decreased during the postmortem storage period of Qinchuan cattle muscle. Through Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, it was found that BSG and related differentially expressed proteins were significantly annotated to the oxidative phosphorylation pathway, calcium signal pathway and MAPK signaling pathway, indicating that BSG played an important role through the MAPK signaling pathway. In addition, for the tunicamycin group, the relative expression of the key proteins in the MAPK signaling pathway was significantly down-regulated, indicating that BSG inactivated the MAPK signaling pathway. This finding lays a good foundation for exploring the effect of BSG on the MAPK signaling pathway. After inhibiting BSG expression, caspase-3 activity in the tunicamycin group increased significantly, indicating that apoptosis was an important link in cell injury mechanism, and tunicamycin acted on the N-terminal structure of BSG to deglycosylate the protein and inhibited the folding of intracellular proteins and consequently their biological activity, thereby inducing cell apoptosis.

In order to clarify the relationship between the degree of glycolysis and water-holding capacity during the maturation of Tan sheep meat, the M. longissimus dorsi of six-month-old Tan sheep was aged at 4 ℃ postmortem and evaluated for drip loss, purge loss, calpain-1 activity, myofibril fragmentation index (MFI), ATP content, glucose content, glycogen content, lactic acid content, lactate dehydrogenase (LDH) activity, pyruvate kinase (PK) activity and pH after 0, 1, 2, 3, 4 and 8 days. The results showed that as maturation time increased, drip loss, purge loss and centrifugal loss increased first and then decreased (P < 0.05), reaching their maximum values on day 4. ATP and glycogen contents continued to decrease (P < 0.05). The contents of glucose and lactic acid increased first and then decreased (P < 0.05), and so did LDH activity (P < 0.05), reaching its maximum level on day 4. PK activity showed a constant decreasing trend (P < 0.05). The correlation analysis showed that glycogen content was negatively correlated with drip loss (P < 0.05) as well as purge loss and centrifugal loss (P < 0.01), and positively correlated with nuclear magnetic resonance (NMR) transverse relaxation times (T21, T22 and T23) (P < 0.05 or P < 0.01). LA content was significantly positively correlated with drip loss (P < 0.001) as well as purge loss and centrifugal loss (P < 0.01), but had no correlation with T21, T22 or T23. Therefore, the glycolysis process of Tan sheep meat was activated rapidly after slaughter, which caused change in the activity of glycolysis-related enzymes and the contents of metabolites, thereby resulting in changes in the water adsorption capacity of muscle proteins, and ultimately affecting the water-holding capacity of Tan sheep meat after slaughter.

In order to uncover the role of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) (PI3K/AKT) signaling pathway in metabolic regulation in Tan sheep meat during chilled storage, the transcriptome changes of lamb meat injected with the PI3K inhibitor LY294002 after 0, 4 and 8 days of chilled storage were studied by high-throughput sequencing. Altogether, 474, 96, and 13 differentially expressed genes (DEGs) between the control and LY294002 treatment groups were identified on days 0, 4, and 8, respectively. Functional enrichment analysis showed that the DEGs were mainly related to metabolic homeostasis, such as amino acid biosynthesis, glycolysis/gluconeogenesis, and glyceride metabolism. In addition, tissue section analysis showed that the gap between muscle fibers in the LY294002 group increased and the diameter of muscle fibers decreased significantly relative to the control group, indicating muscle atrophy. These results indicated that the PI3K/AKT signaling pathway played a crucial role in maintaining metabolic balance during the storage of Tan mutton, which in turn ensured the normal growth of muscle. This study provides a new direction for further elucidating the molecular mechanism by which the PI3K/AKT signaling regulates metabolic homeostasis in Tan mutton during chilled storage.

In this study, microcapsules were prepared using conjugated linoleic acid (CLA) from Tan sheep tail fat as the core material and whey protein isolate (WPI) and maltodextrin (MD) as the wall material, and their physicochemical properties were characterized using scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) analysis. Besides, the oxidative stability and release behavior of the microcapsules were analyzed through accelerated storage experiments and in vitro simulated digestion experiments, and their antioxidant and cholesterol lowering activities were evaluated as well. The results showed that the particles of the CLA microcapsules were intact, with a relatively smooth surface, and had good thermal stability, oxidative stability, and sustained-release performance. After gastrointestinal digestion, the antioxidant stability and cholesterol lowering activity of the microcapsules were significantly higher than those of free CLA. At the end of in vitro simulated digestion, the scavenging rates of the microcapsules against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) cation radical, and superoxide anion radical were (70.84 ± 3.97)%, (78.53 ± 4.28)%, and (59.88 ± 2.58)%, respectively. The inhibition rate against cholesterol micelles was (73.48 ± 2.53)%, and the binding rates to sodium taurocholate, sodium glycine cholate, and sodium cholate were (40.62 ± 3.14)%, (66.79 ± 3.01)%, and (55.43 ± 2.39)%, respectively. This study indicates that microencapsulation not only significantly enhances the oxidative stability of Tan sheep tail fat CLA, but also improves its antioxidant and cholesterol lowering activity. This study provides a theoretical basis for the deep processing and comprehensive utilization of Tan sheep tail fat CLA.

In this study, a phylogenetic tree was constructed using bovine heat shock protein A6 (HSPA6) sequences and those of other organisms, and bioinformatic methods were used to analyze the basic physicochemical properties and hydrophilicity of bovine HSPA6 protein. Meanwhile, a protein interaction network was constructed to investigate the structural and functional properties of the protein encoded by the HSPA6 gene. The results showed that bovine HSPA6 protein had high similarity in amino acid sequence with those of sheep, Yangtze finless porpoise and other mammals. The molecular mass of bovine HSPA6 protein was 70 570.64 u, the theoretical isoelectric point was 5.66, and it was an acidic hydrophilic protein without transmembrane structure or signal peptide. Bovine HSPA6 protein may have 11 phosphorylation sites with score greater than 0.900 and N-glycosylation sites at the terminal bases, and it was a relatively stable protein with a secondary structure consisting mainly of 40.38% α-helix and 33.65% random coil, containing two major structural domains, the N-terminal nucleotide-binding domain and the C-terminal peptide-binding domain, which played a role in the cytoplasm. The constructed protein network showed that bovine HSPA6 protein mainly interacted with BAG1, DNAJA4, DNAJB1 and DNAJC2, and was involved in the activity of adenylate exchange factors, ATPase activity and chaperone binding, indicating that the HSPA6 protein exerted a potential function in biological processes such as energy metabolism in the bovine organism. These multiple bioinformatic analyses provide a theoretical basis for an in-depth investigation of the mechanism of the effect of bovine HSPA6 protein on meat quality.

This study was performed in order to uncover the molecular mechanism by which postmortem glycolysis affects meat quality traits for the purpose of promoting the research and development of prediction technologies for the quality change of chilled Tan lamb and promoting the improvement of its processing, storage and transportation technologies. High-throughput sequencing technology was used for transcriptome sequencing and analysis of the hind leg meat from Yanchi Tan lambs after 0, 4 and 8 days of chilling. The results showed that the differential expression genes (DEGs) were mainly enriched in cellular amide metabolism, ATP metabolism, skeletal muscle contraction and ribosomes and involved in glycolysis, ribosomes and the p53 signaling pathway, and these DEGs constituted a key part of muscle cell function. The phosphofructokinase (PFKM), glyceraldehyde-3-phosphate dehydrogenase (GADPH), phosphoglycerate mutase 2 (PGAM2), enolase 3 (ENO3) and pyruvate kinase (PKM) genes were the core genes involved in the glycolytic metabolism of Tan lambs, which changed meat quality mainly by affecting the structure of muscle fibers, the degradation degree of structural proteins, the activity of glycolytic enzymes, the production of ATP and the activity of complexes.

This study addressed the effect of adenosine 5’-diphosphate (ADP) ribosylation on the mitochondrial function and quality of Qinchuan cattle meat during early postmortem aging. The Longissimus dorsi muscle of Qinchuan cattle treated with 20 µmol/L rucaparib, a poly(ADP-ribose) polymerase 1 (PARP1) inhibitor, were evaluated for mitochondrial indices, myofibrillar fragmentation index (MFI), shear force, pH, and other quality indices after being stored for 0 h, 6 h, 12 h, 2 d, 4 d, and 8 d and the expression levels of PARP1 and desmin were detected using Western blot. The results showed that the content of reactive oxygen species (ROS) in the treated group was significantly lower than that in the control group (P < 0.05) during 0 h–8 d (except 12 h) after slaughter. The caspase-3 activity and MFI in the treated group were significantly lower than those in the control group (P < 0.05) during 0–12 h. Mitochondrial membrane potential during 2–4 d as well as succinate dehydrogenase (SDH) activity during 4–8 d were significantly higher in the treated group than in the control group (P < 0.05). These findings indicate that PARP1 inhibition, which characterizes ADP ribosylation, can slow down the decrease in mitochondrial membrane potential and increase SDH activity, preserving mitochondrial function to some extents and delaying the decrease in MFI and the degradation of desmin and thereby meat tenderization.

Our purpose was to clarify the effect of CaCl2 treatment on the energy level and quality of Tan sheep meat during postmortem aging. Tan sheep hind leg meat was injected with 200 mmol/L CaCl2 solution, and aged at 4 ℃ for 0, 2, 4, 6, and 8 days. The protein expression of phosphofructokinase (PFKM) was detected by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot to verify whether the glycolysis pathway could be activated by CaCl2. At the same time, the energy level and meat quality indexes were measured during postmortem aging to analyze the mechanism by which the glycolysis pathway affects the metabolic level and quality of Tan sheep meat. The results showed that the protein expression of PFKM decreased during postmortem aging, indicating activation of the glycolytic pathway. CaCl2 treatment accelerated the glycolysis process after slaughter, thereby promoting the decomposition of glycogen, increasing the production of lactic acid, and resulting in a rapid decrease in pH. Water-holding capacity (WHC), myofibril fragmentation index (MFI) and b* value were higher and shear force and a* were lower in the treatment group than in the control and blank groups. Therefore, CaCl2 could affect the color, WHC and tenderness of Tan sheep meat at different aging stages. By accelerating the decrease of pH and the accumulation of energy metabolites, the glycolytic pathway increased the level of energy metabolism during postmortem aging, while inhibiting the production of oxymyoglobin, activating the activity of calpain, changing the structure of myofibrils and shortening the space between muscle protein molecules, which accelerated the process of myofibril fragmentation and the hydrolysis of myofibrillar protein, and led to a deterioration in meat color and an increase in water loss and meat tenderness.

In this study, the Longissimus dorsi muscle of Qinchuan cattle was injected with the proteasome inhibitor MG-132 immediately postmortem and then stored at 4 ℃. The effect of the ubiquitin-proteasome pathway (UPP) on protein degradation as well as changes in the proteasome activity, ubiquitin content and microstructure of the muscle during postmortem storage was explored in order to provide theoretical support for precise postmortem regulation of beef quality. With the extension of storage time, proteasome activity was lower and the contents of total soluble protein and ubiquitin were higher in the MG-132 group than in the control group. The sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that the band intensity of total soluble proteins between 40 and 250 kDa was greater in the MG-132 group than in the control group; muscle structure was better preserved in the MG-132 group, and the Z line and the boundary between light and dark bands were clearer than those in the control group. The contents of total soluble protein and ubiquitin showed a significantly positive correlation (P < 0.05). In conclusion, postmortem injection of MG-132 inhibited the proteasome activity and the degradation of ubiquitinated proteins in the UPP in Qinchuan beef, which in turn altered protein degradation and attenuated muscle damage. This suggests that the UPP has a potential role in meat quality formation; the proteasome not only degrades proteins by itself alone to destroy beef myofibrillar structure, but also influences postmortem beef protein degradation through mediating the UPP, ultimately affecting postmortem beef quality.

This research investigated the relationship between mitochondrial damage and meat tenderness of Tan sheep during postmortem aging. The M. Longissimus dorsi muscles from six-month-old Tan sheep were divided into lipopolysaccharide (LPS) treatment and blank control groups. Mitochondrial reactive oxygen species (ROS) content, membrane potential, mitochondrial permeability transition pore (MPTP) openness, mitochondrial swelling, pH, cooking loss, texture, moisture distribution, shear force and myofibril fragmentation index (MFI) in each group were measured at 0, 6, 12, 24, and 72 hours postmortem. The results showed that during postmortem aging, MPTP openness gradually increased in both groups. ROS content, cooking loss rate and MFI value showed an increasing trend as well. Mitochondrial membrane potential, pH, elasticity, T22 peak area and shear force showed a decreasing trend. Hardness, chewability and cohesiveness increased at first and then decreased. Therefore, disruption of oxidative homeostasis in muscle cells of Tan sheep resulted in an increase of ROS content, which caused mitochondrial damage by inducing the opening of MPTP and decreasing mitochondrial membrane potential. Moreover, the structural changes of myofibrils shortened the gap between muscle protein molecules, resulting in increased water loss rate and poorer water retention in muscles, promoting the process of myofibril fragmentation and improving the tenderness of Tan sheep meat. Correlation analysis showed that mitochondrial damage and tenderization occurred simultaneously during the postmortem aging of Tan sheep meat, and the more serious the mitochondrial damage was, the better the tenderness was.

In order to investigate the effects of lipopolysaccharide (LPS) on the mitochondrial signaling pathway in muscle cells of Tan sheep, M longissimus dorsi muscles from six-month-old Tan sheep were aged at 4 ℃ for 0, 6, 12, 24 and 72 h postmortem and evaluated for pH, ATP content, cell apoptosis rate, cell apoptosis-related enzyme activity, succinatedehydrogenase (SDH) activity, citrate synthase (CS) activity, B-cell lymphoma 2 (Bcl-2) family protein contents, and cytochrome c (Cyt-c) and cysteinyl aspartate specific proteinase 3 (Caspase-3) expression levels. The results showed that the apoptosis rate and Bcl-2-associated X protein (Bax)/Bcl-2 ratio in the control and LPS-induced groups were significantly increased during postmortem aging (P < 0.05). The activities of Caspase-3 and Caspase-9 increased first and then decreased. After LPS treatment, the activities of Caspase-3 and Caspase-9 were higher than those in the control group at all time points. The pH, Cyt-c reduction level and mitochondrial ATP content were significantly decreased overall (P < 0.05). The relative expression level of Cyt-c was significantly increased in both groups at 12 h postmortem, and decreased during 24–72 h in the LPS group. The content of Caspase-3 activated fragment protein in the LPS treatment group was higher than that in control group at the same time points. In conclusion, LPS could activate Caspase-3 and Caspase-9, and reduce the mitochondrial content of ATP and consequently energy metabolism level, thus affecting the activities of SDH and CS, promoting the release of Cyt-C, and increasing Bax/Bcl-2 ratio, and finally inducing cell apoptosis through the mitochondrial signaling pathway.

In order to investigate the effect of differential expression of heat shock protein family A (Hsp70) member 6 (HSPA6) on the meat quality of Qinchuan cattle during postmortem maturation, the Longissimus dorsi muscle of Qinchuan cattle was stored at 4 ℃ and evaluated for meat quality at 0, 2, 4, 6 and 8 days postmortem. 4D-Label free quantification (4D-LFQ) was used to analyze the expression of HSPA6 and related differential proteins. The results showed that the expression of HSPA6 decreased with increasing storage time, the contents of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and reduced form of nicotinamide-adenine dinucleotide (NADH) decreased, the myofibril fragmentation index (MFI) increased, and the shear force and centrifugal loss increased and then decreased. Correlation analysis showed that HSPA6 expression was positively correlated with the contents of ATP and NADH and shear force (P < 0.05) and negatively correlated with MFI and centrifugal loss (P < 0.01), indicating that HSPA6 degradation was closely related to energy metabolism and water retention in beef during storage. Proteomics identified 24 significantly differentially expressed proteins (DEPs) associated with HSPA6 expression, which could cause proteasome-mediated ubiquitin-dependent proteolytic metabolism and cellular proteolysis through carbohydrate derivative binding and purine nucleoside triphosphate binding, in turn causing metabolic disorders or imbalances. These DEPs could also control protein degradation and cell apoptosis, in turn affecting structural changes in muscle and reducing tissue energy levels, and ultimately affecting the tenderness, MFI and water retention of Qinchuan beef through resistance to cellular structural protein degradation.

The moisture distribution and key volatile flavor compounds of beef tallow from Qinchuan cattle roasted for different periods were analyzed by low field-nuclear magnetic resonance (LF-NMR) spectroscopy and headspace solid-phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). The results showed that the L* value significantly decreased (P 0.05), while the proportion of immobile water first increased and then decreased, and the proportion of free water showed an overall downward trend (P > 0.05). The relaxation time T23 and T24 showed a significant decreasing trend as roasting time increased (P < 0.05), indicating that the binding between water molecules and macromolecular substances such as protein and lipid became tighter. Beef tallow samples roasted for different periods could be effectively distinguished by electronic nose and the roasting process had a significant effect on the contents of alcohols, aromatic compounds, terpenes, and organic sulfur compounds in beef tallow according to principal component analysis (PCA) of the electronic nose data. A total of 95 volatile compounds were identified in all samples. The contents of 1-methoxy-2-propanol, 1-octene-3-ol, hexanal, nonanal, acetic acid, nonanoic acid, and acetamide were relatively higher in each sample, whereas ketones, heterocycles and amine compounds occurred mostly in the later stages of roasting. In total 19 key aroma components were identified based on odor activity value (OAV) and most of the substances have the largest OAV at 12 min of roasting.

To investigate the influence of freezing rate on the volatile flavor compounds in hand-grab mutton, the differences in the volatile flavor compounds among unfrozen samples (control) and those frozen at three different freezing rates, namely 0.26 (?18 ℃), 0.56 (?40 ℃) and 2.00 cm/h (?80 ℃) were analyzed by headspace solid phase micro-extraction (HS-SPME) coupled with gas chromatography-mass spectrometry (GC-MS) and electronic nose. The results showed that the eutectic point temperature of hand-grab mutton was (?9.66 ± 0.24) ℃. In terms of overall odor perception, the electronic nose could distinguish hand grab mutton frozen at different freezing rates. Totally 44, 40, 49 and 53 volatile substances were identified in the control, ?18 ℃ frozen, ?40 ℃ frozen and ?80 ℃ frozen samples, respectively, among which aldehydes, alcohols and ketones were the major ones. The content of total volatile substances in these frozen samples was 30.78%, 40.79% and 70.75% of that in the control group, respectively. The contents of aldehydes, alcohols, ketones, acids and esters decreased with decreasing freezing rate. For all samples, hexanal, heptanal, octanal, nonanal, (E)-2-octenal, 2,4-decadienal and 1-octen-3-ol were determined as key aroma compounds based on relative odor activity value (ROAV). The higher the freezing rate, the greater the ROAV values of these compounds. The sensory scores of the four samples followed the decreasing order of control > ?80 ℃ > ?40 ℃ > ?18 ℃ (P < 0.05). In summary, we concluded that the freezing of hand-grab mutton can cause losses of a large number of volatile aroma components, but higher freezing rates can reduce the loss of volatile aroma components, maintaining the original flavor to a large extent.

Rapid non-destructive testing technologies are effectively used to analyze and evaluate the linoleic acid content while processing fresh meat products. In current study, hyperspectral imaging (HSI) technology was combined with deep learning optimization algorithm to model and analyze the linoleic acid content in 252 mixed red meat samples. A comparative study was conducted by experimenting mixed sample data preprocessing methods and feature wavelength extraction methods depending on the distribution of linoleic acid content. Initially, convolutional neural network Bi-directional long short-term memory (CNN-Bi-LSTM) model was constructed to reduce the loss of the fully connected layer extracted feature information and optimize the prediction effect. In addition, the prediction process of overfitting phenomenon in the CNN-Bi-LSTM model was also targeted. The Bayesian-CNN-Bi-LSTM (Bayes-CNN-Bi-LSTM) model was proposed to improve the linoleic acid prediction in red meat through iterative optimization of Gaussian process acceleration function. Results showed that best preprocessing effect was achieved by using the detrending algorithm, while 11 feature wavelengths extracted by variable combination population analysis (VCPA) method effectively contained characteristic group information of linoleic acid. The Bi-directional LSTM (Bi-LSTM) model combined with the feature extraction data set of VCPA method predicted 0.860 Rp2 value of linoleic acid content in red meat. The CNN-Bi-LSTM model achieved an Rp2 of 0.889, and the optimized Bayes-CNN-Bi-LSTM model was constructed to achieve the best prediction with an Rp2 of 0.909. This study provided a reference for the rapid synchronous detection of mixed sample indicators, and a theoretical basis for the development of hyperspectral on-line detection equipment. [ABSTRACT FROM AUTHOR]

The content of fatty acids, amino acids, nucleotides of Tan sheep from Yanchi, Ningxia roasted for different periods were analyzed. The results showed that the total protein content increased from 19.92% to 40.51%, and the total fat content increased from 3.51% to 12.75%. The total fatty acid content increased first (roasted for 0-8 min) and then decreased (roasted for 8-12 min) and increased finally (roasted for 12-20 min) with no significant difference (C>0.05). The content of oleic acid, stearic acid and palmitic acid were the highest among 25 fatty acid identified in all samples and their content exceeds 100 mg/100 g. The content of total hydrolyzed amino acids increased significantly (C<0.05), increased from 18.5 g/100 g in fresh meat to 49.42 g/100 g. Among all amino acid, lysine, leucine, and cysteine showed the most significant increases. Among the free amino acids, the contents of arginine, alanine and cysteine showed an increasing trend, the contents of histidine showed an decreasing trend and the changes of other free amino acids were not significant (P>0.05). The taste activity value (TAV) method identified that the key umami amino acids in roasted Tan mutton was glutamic acid, the key sweet amino acid was alanine, and the key bitter amino acids were methionine, phenylalanine, valine, and arginine. The main taste substances 5'-adenylic acid and 5'-guanylic acid in roasted Tan mutton increased significantly with increase of time. Collectively, the results of PCA analysis indicated that fatty acids, hydrolyzed amino acids, free amino acids and nucleotides in Tan mutton were significantly different during the roasting process. [ABSTRACT FROM AUTHOR]

In this paper, SSR sites were screened from the sheep expression sequence tag in NCBI system (EST) database by SSR Finder software and MISA technology, and sheep EST-SSR fluorescent primers were designed using Primer 3.0 to differentiate the products of Ningxia Tan lamb, Xinjiang fine-wool sheep meat and Tibetan lamb. Experiments were PCR amplified using liver DNA from three sheep as templates for designed EST-SSR primers and detected SSR typing using capillary electrophoresis. The results showed that the fluorescent primers p2105.1 :248-559, p2025.1 : 896-1059 and p2104.1:704-1015 designed by EST-SSR labeling showed good specificity in Ningxia Tan mutton, Xinjiang fine lamb and Tibetan mutton, indicating that the distinction of three sheep varieties was achieved. This study accurately judged the varieties of three pure-bred mutton through EST-SSR marker technology science, which was of important significance for the development and utilization of sheep genetic resources, variety identification and rich molecular marker types. [ABSTRACT FROM AUTHOR]