Influence of oxidative damage to proteins on meat tenderness using a proteomics approach

Characterization of the effects of micro-bubble treatment on the cleanliness of intestinal sludge, physicochemical properties, and textural quality of shrimp (Litopenaeus vannamei)

This study assessed the effects of Micro-bubble (MB; average size of 36.50 μm) on the physicochemical properties of live shrimp (Litopenaeus vannamei) and cooked ones. This study also examined the visual appearance, intestinal sludge's presence, microbial decontamination efficacy, and shrimp meat's textural properties. In addition, sensory evaluation was conducted to appraise the impact of MB on the gustatory and aromatic attributes of shrimp. This study showed that MB treatment was substantially better than traditional aeration (TA) treatment in terms of appearance, color, and intestinal sludge cleanliness. Specifically, all the above indicators exhibited optimal performance by the MB 30 group. Moreover, the MB treatment effectively decontamination microbes, reduced total volatile bases nitrogen (TVB-N; from 15.27 to 10.30 mg/100 g) and improved the textural indicators, while the best performed with the MB30 group. The sensory evaluation showed that the MB treatment groups exhibited enhanced aroma and taste profiles (7.45 to 8.00 points) of the shrimp compared to the TA (6.80 and 7.80 points) and control (7.15 and 7.25 points) groups, favored by the evaluation panels. Therefore, the findings of this study reveal that MB treatment provides a practical and invaluable theoretical framework to effectively address concerns about the quality and safety of live shrimp. Refraining from contamination during initial production would benefit stakeholders by reducing food and economic losses while ensuring longer shelf-life and safety of shrimp.

Meta-Analysis of Dietary Tannins in Small Ruminant Diets: Effects on Growth Performance, Serum Metabolites, Antioxidant Status, Ruminal Fermentation, Meat Quality, and Fatty Acid Profile

Tannins are secondary metabolites naturally present in various plants as a defense mechanism. In animal nutrition, they play a dual role, acting as both antinutritional factors and bioactive agents, with potential benefits in nutrient metabolism and product quality. This meta-analysis aimed to evaluate the effects of dietary tannin on nutrient intake and digestibility, blood serum metabolite levels, growth performance, carcass characteristics, and meat quality in small ruminants. Ninety-seven studies were included in this meta-analysis. The effects of tannins were analyzed using a random-effects model to determine the weighted mean difference between treatments with tannins and the control (without tannins). Publication bias and heterogeneity between studies were explored, and meta-regression and subgroup analyses were performed. The results indicated that tannin significantly increased the intake of dry matter, crude protein, nitrogen (N), fecal N, and meat fatty acids (FA), such as C18:2 ω6, C18:3 ω3, C20:4 ω6, C20:5 ω3, total ω3 and ω6 FA, and total polyunsaturated FA (PUFA). However, NH3-N, urinary N, blood urea nitrogen, cold carcass weight, subcutaneous fat thickness, drip loss, and nutrient digestibility decreased. In conclusion, tannin in small ruminants did not affect animal productivity and antioxidative status, but mainly modified nitrogen metabolism and improved the fatty acid profile of meat.

Proteomic analysis of wild boar meat: Effect of storage method and time on muscle protein stability

Oxidation processes affect proteins from various molecular pathways and are crucial for wild boar meat quality, shelf life and human health. This study investigated the effects of different storage methods on the formation and composition of oxygen-induced protein aggregates in the muscles of European wild boar (Sus scrofa scrofa). Vacuum packaging (VAC), modified atmosphere packaging (MAP) and dry-ageing (DA) were compared over a 21-day storage period. The results showed significant differences in protein aggregation depending on the method and storage time. The most intense protein aggregation occurred in the MAP (80 % O2), while air DA (20.9 % O2) resulted in intermediate levels of protein aggregation. Crucial myofibrillar proteins involved in aggregate formation were titin, myosin isoforms (MYH1, MYH2 and MYH7) and nebulin, which were cross-linked with small sarcoplasmic enzymes, such as muscle creatine kinase, isocitrate dehydrogenase and ATPase 1. High‑oxygen storage conditions also promoted the oxidation of ATP synthase, beta-enolase 3, ADP/ATP translocase and myoglobin.

Differential regulation of physicochemical properties and myofibrillar protein degradation of yak meat by interactions between reactive oxygen species and reactive nitrogen species during postmortem aging

BACKGROUND

This study aimed to explore how interactions between reactive oxygen species (ROS) and reactive nitrogen species (RNS) affect oxidative properties, nitrosative properties, and myofibrillar protein degradation during postmortem aging of yak meat.

RESULTS

Yak longissimus dorsi was incubated with saline, ROS activator (H2O2)/inhibitor N-Acetyl-L-cysteine (NAC) and RNS activator S-Nitrosoglutathione (GSNO)/inhibitor L-NAME hydrochloride (L-NAME) combined treatments at 4 °C for 12, 24, 72, 120, and 168 h. The results indicated that regardless of whether RNS was activated or inhibited, activated ROS played a dominant role in myofibrillar protein degradation by oxidative modification to increase carbonyl content, disulfide bonds, surface hydrophobicity, and dimerized tyrosine while decreasing sulfhydryl content, thereby degrading nebulin, titin, troponin-t and desmin. Notably, the Warner-Bratzler shear force (WBSF) of the H2O2 + L-NAME group was the smallest, whereas that of the NAC + GSNO group was smaller than that of the NAC + L-NAME group.

CONCLUSION

These findings provide new insights into meat tenderization patterns through the interaction between ROS and RNS. © 2024 Society of Chemical Industry.

Elucidating the degradation mechanism of beef myofibrillar proteins under hydroxyl radical oxidation through the lens of cysteine oxidation modifications

The study aimed to assess the oxidative modification behavior of bovine myofibrillar proteins (MPs) cysteines (Cys) by hydroxyl radical (·OH) through the construction of an in vitr Fenton reaction system. The ·OH generated by the Fenton reaction induced large-scale oxidative modification of Cys, and redox proteomics identified a total of 1192 differential oxidation sites (Dos), 59 Dos were located in the MPs structure. The Cys of actin (17 Dos), myosin/myomesin (16 Dos), tenascin (12 Dos) and sarcomere (10 Dos) in the MPs structure showed active oxidative modification behavior towards ·OH, especially with the "-C-X-X-X-X-W-" structure amino acid sequence showed high sensitivity. Notably, the oxidative modification of Cys by ·OH was an irreversible process, as evidenced mainly by a significant decrease (p < 0.05) in protein sulfhydryl groups and unfolding of protein secondary and tertiary structures. While the intermolecular forces of MPs were altered, with the most direct result being the degradation of MPs, which had a positive effect on beef tenderness and a negative effect on water-holding capacity.

TMT-based quantitative proteomics reveals the effects of electromagnetic field and freezing preservation techniques on mutton quality

This study investigated the effects of electromagnetic field preservation (EP) and freezing storage (FS) on the quality of northern Qianbei Ma mutton. Using tandem mass tagging (TMT)-labeled quantitative proteomics and bioinformatics, it was observed that EP more effectively inhibited pH increase and maintained a* and b* values compared to FS. Furthermore, the EP group was able to better maintain the water-holding capacity and tenderness of the mutton under prolonged storage. Proteomics analysis identified 397 differentially expressed proteins (DEPs) between the two storage methods at the same storage duration. GO and KEGG enrichment analyses indicated that proteins such as A0A452DSW4, A0A452E8M7, and D3JYV6 were involved in energy metabolism and redox processes, while A0A452EJ66, A0A452DSW4, and A0A452FJE8 played significant roles in protein binding. Overall, EP technology demonstrated superior benefits for maintaining mutton quality, suggesting a novel approach for mutton preservation.

Unveils key proteins in Xinjiang goat muscle linked to post-mortem meat quality: A TMT-based proteomic analysis

An extensive proteomic analysis utilizing the tandem mass tag (TMT) method was conducted to investigate the changes in protein expression in the longissimus dorsi muscle of Xinjiang goats over various post-mortem intervals: immediately after death within 0 h, 12 h, 24 h and 48 h. The investigation carefully identified around 108 proteins that showed significant changes in expression during these intervals. Among these proteins, six were highlighted for their crucial roles in muscle growth and differentiation of muscle fibers post-mortem. These proteins, namely COL12A1, MRPL46, CTNNB1, MYH1, CAPZA1, and MYL9, have a direct effect on the meat's quality attributes, such as tenderness and color. Further discuss observed a progressive increase in the expression of proteins linked with oxidative metabolism (MSRB2, ENOX1, LOC102170282, GSTM1, and AOC3) as the post-mortem aging period extended, particularly between 24 h to 48 h. These proteins are instrumental in defining the color and flavor profiles of goat meat, underscoring the importance of precise processing and storage conditions to preserve meat quality during the critical aging phase. This enhanced understanding of protein expression dynamics offers significant implications for optimizing meat quality and provides a scientific basis for post-mortem handling practices in the goat meat industry.

Sequential window acquisition of all theoretical mass spectra (SWATH-MS) as an emerging proteomics approach for the discovery of dark-cutting beef biomarkers

Recent advances in "omics" technologies have enabled the identification of new beef quality biomarkers and have also allowed for the early detection of quality defects such as dark-cutting beef, also known as DFD (dark, firm, and dry) beef. However, most of the studies conducted were carried out on a small number of animals and mostly applied gel-based proteomics. The present study proposes for the first time a Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS) proteomics approach to characterize and comprehensively quantify the post-mortem muscle proteome of DFD (pH24 ≥ 6.2) and CONTROL (5.4 ≤ pH24 ≤ 5.6) beef samples within the largest database of DFD/CONTROL beef samples to date (26 pairs of the Longissimus thoracis muscle samples of young bulls from Asturiana de los Valles breed, n = 52). The pairwise comparison yielded 35 proteins that significantly differed in their abundances between the DFD and CONTROL samples. Chemometrics methods using both PLS-DA and OPLS-DA revealed 31 and 36 proteins with VIP > 2.0, respectively. The combination of different statistical methods these being Volcano plot, PLS-DA and OPLS-DA allowed us to propose 16 proteins as good candidate biomarkers of DFD beef. These proteins are associated with interconnected biochemical pathways related to energy metabolism (DHRS7B and CYB5R3), binding and signaling (RABGGTA, MIA3, BPIFA2B, CAP2, APOBEC2, UBE2V1, KIR2DL1), muscle contraction, structure and associated proteins (DMD, PFN2), proteolysis, hydrolases, and activity regulation (AGT, C4A, GLB1, CAND2), and calcium homeostasis (ANXA6). These results evidenced the potential of SWATH-MS and chemometrics to accurately identify novel biomarkers for meat quality defects, providing a deeper understanding of the molecular mechanisms underlying dark-cutting beef condition.

Comparative proteomic analyses to investigate premature browning in high‑oxygen modified atmosphere packaged beef patties

This study compared the proteomics of beef patties under high‑oxygen modified atmosphere packaging (HiOx-MAP) and vacuum packaging (VP) during heating. The color and oxidation stability of fresh patties, and myoglobin denaturation of cooked patties were also measured. The results suggested that HiOx-MAP patties contained more oxymyoglobin in fresh meat and had higher myoglobin denaturation during heating than VP patties, resulting in premature browning (PMB) during cooking. Proteomic analysis found that the overabundance of proteasome subunit beta type-2 (PSMB2) and peroxiredoxin-2 (PRDX2) in HiOx-55 °C, which can remove the damaged proteins and inhibit oxidation respectively, are of benefit to meat color stability during storage, however, this was still insufficient to inhibit the occurrence of PMB during cooking. The high abundance of lamin B1 (LMNB1) in VP-55 °C can maintain the stability of meat color. This research provides greater understanding, based on proteomic perspectives, of the molecular mechanism of PMB.

Leveraging Functional Genomics for Understanding Beef Quality Complexities and Breeding Beef Cattle for Improved Meat Quality

Consumer perception of beef is heavily influenced by overall meat quality, a critical factor in the cattle industry. Genomics has the potential to improve important beef quality traits and identify genetic markers and causal variants associated with these traits through genomic selection (GS) and genome-wide association studies (GWAS) approaches. Transcriptomics, proteomics, and metabolomics provide insights into underlying genetic mechanisms by identifying differentially expressed genes, proteins, and metabolic pathways linked to quality traits, complementing GWAS data. Leveraging these functional genomics techniques can optimize beef cattle breeding for enhanced quality traits to meet high-quality beef demand. This paper provides a comprehensive overview of the current state of applications of omics technologies in uncovering functional variants underlying beef quality complexities. By highlighting the latest findings from GWAS, GS, transcriptomics, proteomics, and metabolomics studies, this work seeks to serve as a valuable resource for fostering a deeper understanding of the complex relationships between genetics, gene expression, protein dynamics, and metabolic pathways in shaping beef quality.

Quantitative proteomic analysis to identify potential biomarkers linked to quality traits of beef tripe from different sources

In this work, the 4D data-independent acquisition (DIA) quantitative strategy was used for differential proteomic analysis of four beef tripe samples from different sources to explore the associations between differentially expressed proteins (DEPs) and meat quality traits. A total of 68 shared DEPs were identified in all comparison groups, which were mainly involved in phosphorylation signaling pathway, peroxisome proliferator-activated receptor (PPAR) signaling pathway, and glucuronic acid pathway. In the correlation analysis between DEPs and quality traits of beef tripe, it was found that 21 proteins were significantly associated with the quality traits in beef tripe, which could be considered as the potential biomarkers of beef tripe quality. This study has successfully uncovered the protein composition of beef tripe for the very first time, which helps to understand the key proteins and biological processes associated with the quality traits of beef tripe from different sources and improve the quality control of beef tripe.

Proteomics reveals the mechanism of protein degradation and its relationship to sensorial and texture characteristics in dry-cured squid during processing

Proteolysis in dry-cured squid contributes to the development of sensory and textural attributes. In this study, label-free quantitative proteomics was conducted to study the mechanism of proteolysis and its correlation with quality changes. The results showed that the protein profile of dry-cured squid changed markedly during processing, which was confirmed by the quantification of myofibrillar protein, amino nitrogen and total free acids, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis. Thirty-two key differentially abundant proteins were found to be correlated with sensory and texture characteristics, including myofibrillar protein, tubulin beta chain, collagens, heat shock proteins and cytochrome c. The correlation analysis indicated that myosin regulatory light chain and tubulin beta chain played the most important role in the development of texture and sensory attributes in squid samples during the dry-curing process. The results offered novel insights into proteolysis in dry-cured squid and its relationship to quality changes.

Valorization of Dairy and Fruit/Berry Industry By-Products to Sustainable Marinades for Broilers' Wooden Breast Meat Quality Improvement

The study aims to improve the quality of wooden breast meat (WBM) via the use of newly developed marinades based on selected strains of lactic acid bacteria (LAB) in combination with the by-products of the dairy and fruit/berry industries. Six distinct marinades were produced based on milk permeate (MP) fermented with Lacticaseibacillus casei (Lc) and Liquorilactobacillus uvarum (Lu) with the addition of apple (ApBp) and blackcurrant (BcBp) processing by-products. The microbiological and acidity parameters of the fermented marinades were evaluated. The effects of marinades on the microbiological, technical, and physicochemical properties of meat were assessed following 24 and 48 h of WBM treatment. It was established that LAB viable counts in marinades were higher than 7.00 log10 colony-forming units (CFU)/mL and, after 48 h of marination, enterobacteria and molds/yeasts in WBM were absent. Marinated (24 and 48 h) WBM showed lower dry-matter and protein content, as well as water holding capacity, and exhibited higher drip loss (by 8.76%) and cooking loss (by 12.3%) in comparison with controls. After WBM treatment, biogenic amines decreased; besides, the absence of spermidine and phenylethylamine was observed in meat marinated for 48 h with a marinade prepared with Lu. Overall, this study highlights the potential advantages of the developed sustainable marinades in enhancing the safety and quality attributes of WBM.

Early postmortem beef muscle proteome and metabolome variations due to supranutritional zinc and ractopamine hydrochloride supplementation

It was hypothesized that the longissimus thoracis (LT) muscle proteome, phosphoproteome, and metabolome could explain postmortem metabolism and tenderness differences in muscle from cattle supplemented zinc (Zn) and/or ractopamine hydrochloride (RH). High percentage Angus steers (N = 20) were fed in a 2 × 2 factorial assigned to Zn and RH treatments: control (CON; n = 10; analyzed 36 mg Zn/kg dry matter [DM]) or supranutritional Zn supplementation (SUPZN; n = 10; control diet + 60 mg Zn/kg DM [from ZnSO4] + 60 mg Zn/kg DM [from Zn-amino acid complex]) for the entire 89-d trial. During the 28 d before harvest, steers were blocked by body weight within Zn treatments to RH treatments of 0 (NO; n = 10) or 300 mg (RAC; n = 10) per steer per day. Steers were harvested at the Iowa State Meat Laboratory, where pH decline (1, 3, 6, and 24 h postmortem) was measured. At 24 h postmortem, LT muscle sections were removed from carcasses, and steaks were analyzed for Warner-Bratzler shear force (WBSF) values at 1, 3, 7, and 14 d postmortem. Muscle samples were taken at 1 h, 1, 3, 7, and 14 d postmortem for the following analysis: troponin-T degradation (1, 3, 7, and 14 d postmortem), myosin heavy chain analysis (1 h postmortem), sarcoplasmic proteome analysis through tandem mass tagging analysis (1 h and 1 d postmortem), metabolome analysis (1 h and 1 d postmortem), and phosphoproteome analysis (1 h postmortem). SUPZN-NO tended to have a lower (P = 0.06) pH at 6 h postmortem and a lower WBSF value (P = 0.06) at 1 d postmortem. CON-RAC had a higher (P = 0.04) pH at 6 h postmortem and WBSF value (P < 0.01) at 1 d postmortem. A lower pH at 6 h postmortem and lower WBSF value at 1 d postmortem in the SUPZN-NO treatment was accompanied by more sorbitol and fructose at 1 d postmortem, and less myosin regulatory light chain 2 at 1 h postmortem, and less adenosine monophosphate deaminase 1 (AMPD1) at 1 d postmortem than all other treatments. A higher pH at 6 h postmortem and higher WBSF value at 1 d postmortem in CON-RAC and SUPZN-RAC was accompanied by more soluble structural proteins (troponin-T and myosin-7) at 1 h postmortem than CON-NO. At 1 h postmortem, CON-RAC had more glyceraldehyde-3-phosphate dehydrogenase than CON-NO or SUPZN-RAC. Differences in energy metabolism enzymes, metabolites, and structural proteins may affect ATP production, rigor development, and lactate buildup which may explain the differences in postmortem metabolism and tenderness development at 1 d postmortem.

Proteomic and metabolomic profiling of aged pork loin chops reveals molecular phenotypes linked to pork tenderness

The ability to predict fresh pork tenderness and quality is hindered by an incomplete understanding of molecular factors that influence these complex traits. It is hypothesized that a comprehensive description of the metabolomic and proteomic phenotypes associated with variation in pork tenderness and quality will enhance the understanding and inform the development of rapid and nondestructive methods to measure pork quality. The objective of this investigation was to examine the proteomic and metabolomic profiles of ~2-wk aged pork chops categorized across instrumental tenderness groups. One hundred pork loin chops from a larger sample (N = 120) were assigned to one of the four categories (n = 25) based on instrumental star probe value (Category A, x¯ =4.23  kg, 3.43-4.55 kg; Category B, x¯ =4.79  kg, 4.66-5.00 kg; Category C, x¯ =5.43  kg, 5.20-5.64 kg; and Category D, x¯ =6.21  kg, 5.70-7.41 kg). Soluble protein from ~2 wk aged pork loin was prepared using a low-ionic-strength buffer. Proteins were digested with trypsin, labeled with 11-plex isobaric tandem mass tag reagents, and identified and quantified using a Q-Exactive Mass Spectrometer. Metabolites were extracted in 80% methanol from lyophilized and homogenized tissue samples. Derivatized metabolites were identified and quantified using gas chromatography-mass spectrometry. Between Categories A and D, 84 proteins and 22 metabolites were differentially abundant (adjusted P < 0.05). Fewer differences were detected in comparison between categories with less divergent tenderness measures. The molecular phenotype of the more tender (Category A) aged chops is consistent with a slower and less extended pH decline and markedly less abundance of glycolytic metabolites. The presence and greater abundance of proteins in the low-ionic-strength extract, including desmin, filamin C, calsequestrin, and fumarate hydratase, indicates a greater disruption of sarcoplasmic reticulum and mitochondrial membranes and the degradation and release of structural proteins from the continuous connections of myofibrils and the sarcolemma.

The effect of modified atmosphere packaging at an early postmortem stage on lamb meat quality during subsequent aging

This study explores the influence of modified atmosphere packaging (MAP) on fresh lamb meat quality with respect to gas concentration, rigor state, and post-mortem aging time. A comparison was done for the quality characteristics of lamb Longissimus thoracis lumborum chops that had been packaged separately in air, 75%O2  + 25%CO2 MAP or 50%O2  + 50%CO2 MAP at 1, 6, and 24 h post-mortem and then stored for 6, 12, 24, 72, and 144 h post-mortem, and the quality of lamb chops had been evaluated at each post-mortem period separately. Chops packaged at 1 and 6 h post-mortem in MAP had reduced pH decline, less purge loss, and enhanced redness at early post-mortem storage times. Lamb color stability was evidently greater in 75%O2  + 25%CO2 MAP than in 50%O2  + 50%CO2 MAP during the early storage period when a* and R630/R580 were taken into account. Shear force values were lowest in lambs packaged at 1 h post-mortem with 75%O2  + 25%CO2 MAP at 12 h post-mortem and then increased until 72 h post-mortem, suggesting that rigor has been delayed by such a high O2 MAP. Thus, fresh lamb quality was maintained most effectively when packaged at 1 h post-mortem in 75%O2  + 25%CO2 MAP for consumption at 12 h post-mortem. The exact mechanisms and optimization of MAP based on Chinese retail conditions should be considered in future studies. PRACTICAL APPLICATION: In this study, three slaughter patterns in the meat industry involving boning immediately after dressing (hot-boning) and chilling for a short period (warm-boning) or overnight (cold-boning) are considered, as well as the behavior of non-immediate consumption after purchase. Modified atmosphere packaging provides an effective preservation of early post-mortem muscles with enhanced color stability, water holding capacity, and texture during refrigerated storage. This could provide new insights into how to process lamb muscles in the early post-mortem period to improve and stabilize lamb quality.

The absorption of bovine milk small extracellular vesicles largely depends on galectin 3 and galactose ligands in human intestinal cells and C57BL/6J mice

Small extracellular vesicles in milk (sMEVs) have attracted attention in drug delivery and as bioactive food compounds. Previous studies implicate galactose residues on the sMEV surface in sMEV transport across intestinal and endothelial barriers in humans, but details of glycoprotein-dependent transport are unknown. We used a combination of cell biology and genetics protocols to identify glycoproteins on the sMEV surface that facilitate sMEV absorption. We identified 256 proteins on the bovine sMEVs surface by using LC-MS/MS, and bioinformatics analysis suggested that 42, 13, and 13 surface proteins were N-, O-, and 13 C-glycosylated, respectively. Lectin blots confirmed the presence of mannose, galactose, N-acetyl galactose, fucose, and neuraminate. When surface proteins were removed by various treatment with various proteases, sMEV uptake decreased by up to 58% and 67% in FHs-74 Int and Caco-2 cells, respectively, compared with controls (P < 0.05). When glycans were removed by treatment with various glycosidases, sMEV uptake decreased by up to 54% and 74% in FHs-74 Int and Caco-2 cells, respectively (P < 0.05). When galactose and N-acetyl galactosamine residues were blocked with agglutinins, sMEV uptake decreased by more than 50% in FHs-74 Int cells (P < 0.05). When bovine sMEVs were administered to Galectin-3 knockout mice by oral gavage, hepatic sMEV accumulation decreased by 56% compared with wild-type mice (P < 0.05), consistent with a role of β-galactoside glycan structures in the absorption of sMEVs. We conclude that sMEVs are decorated with glycoproteins, and Galectin-3 and its galactose ligands are particularly important for sMEV absorption.NEW & NOTEWORTHY This is the first paper to assess the role of unique glycans and their Galectin-3 receptor in the transport and distribution of small extracellular vesicles ("exosomes") from milk in mammals. The research assessed milk exosome transport and distribution by using multiple approaches and platforms including cell cultures, various exosome labels, knockout and mutant mice, enzymatic removal of surface proteins and glycans, and lectin blocking of glycans.

Quantitative proteomic analysis of cattle-yak and yak longissimus thoracis provides insights into the differential mechanisms of meat quality

In this study, proteins of cattle-yak longissimus thoracis (CYLT) and yak longissimus thoracis (YLT) were compared using tandem mass tag-labeled quantitative proteomic analysis. A total of 157 proteins were screened as differentially abundant proteins (DAPs) derived from 1551 quantitative proteins. Bioinformatics analysis revealed that the upregulated DAPs in CYLT were mainly involved in energy metabolism, oxidative stress, muscle fiber structure, and extracellular matrix (ECM), while the downregulated DAPs were mainly involved in energy metabolism and ECM function. The upregulated myoglobin, downregulation of NADH dehydrogenase, and upregulation of cytochrome oxidase indicated that CYLT initiates compensatory regulation in response to hypoxic high-altitude environments. Two differentially abundant myosins and five collagens suggested that CYLT and YLT may have distinct differences in the assembly structure of muscle fibers and connective tissue. These differences in energy metabolism and muscle structure will inevitably affect the postmortem physiology of "muscle to meat" and consequently the meat qualities. Therefore, our results will provide important clues to gain insight into the potential causes of meat quality differences between cattle-yak and yak based on high-altitude response.

Green tea catechin prevents oxidative stress-regulated autophagy and apoptosis signaling, and inhibits tenderness in postmortem bovine longissimus thoracis et lumborum muscle

Although green tea catechin has been reported to be an antioxidant and preservative in meat, the extent to which it affects the tenderization of bovine muscle remains largely unknown. This study seeks to evaluate the effect of catechin on the interplay between apoptosis and autophagy, and subsequently, the development of bovine muscle tenderness. The results indicate that catechin significantly alleviated oxidative stress. A concomitant reduction of autophagic markers LC3-II/LC3-I ratio, Beclin-1, and Atg7 levels were caused by catechin. Besides, aforementioned autophagy inhibition was further augmented by PI3K/Akt/mTOR activation. Additionally, catechin protected against mitochondrial dysfunction and inhibited mitochondria-dependent caspase apoptosis pathway. Furthermore, there was a reciprocal inhibition between autophagy and apoptosis. Ultimately, tenderness at 24 and 120 h, an increase in the gap between muscle fiber bundles, and disintegration of myofibrillar architectures were all inhibited by catechin. Therefore, despite alleviating oxidative stress, catechin may hamper tenderization pattern of postmortem bovine muscle.

Molecular Mechanism of ε-Polylysine Treatment of Animal-Derived Foods: Glycine Amidinotransferase Activity Implicates Upregulation of l-Arginine and Creatine

ε-Polylysine is a novel food preservative approved by the U.S. Food and Drug Administration (FDA), yet the mechanism of its effect on animal-derived foods remains unclear. Assessment of the effect of preservatives on goat meat products is necessary. Herein, metabolite accumulation and protein expression of ε-polylysine (0.025%, w/w) spiked with goat meat were investigated by nontarget metabolomics and proteomics combined with ultrahigh performance liquid chromatography quadrupole-Orbitrap high-resolution-mass spectrometry (UHPLC-Q-Orbitrap HRMS) in a simulated in vitro digestion model. The amino side chain of ε-polylysine increased the activity of glycine aminotransferase due to its nucleophilic nature, inducing a significant upregulation of l-arginine (0.43-0.72 mg kg-1) and creatine (3.98-6.89 mg kg-1), with an improvement in muscle quality of goat meat. Downregulation of enzyme phenylalanine hydroxylase expression led to upregulation of l-phenylalanine (2.26-3.25 mg kg-1) and l-tyrosine (0.98-1.29 mg kg-1). Collectively, this study first revealed the biochemical mechanism of ε-polylysine in goat meat products, which makes available new prospects for more accurate use of ε-polylysine in animal-derived foods.

Molecular mechanisms contributing to the development of beef sensory texture and flavour traits and related biomarkers: Insights from early post-mortem muscle using label-free proteomics

Beef sensory quality comprises a suite of traits, each of which manifests its ultimate phenotype through interaction of muscle physiology with environment, both in vivo and post-mortem. Understanding variability in meat quality remains a persistent challenge, but omics studies to uncover biological connections between natural variability in proteome and phenotype could provide validation for exploratory studies and offer new insights. Multivariate analysis of proteome and meat quality data from Longissimus thoracis et lumborum muscle samples taken early post-mortem from 34 Limousin-sired bulls was conducted. Using for the first-time label-free shotgun proteomics combined with liquid chromatography-tandem mass spectrometry (LC-MS/MS), 85 proteins were found to be related with tenderness, chewiness, stringiness and flavour sensory traits. The putative biomarkers were classified in five interconnected biological pathways; i) muscle contraction, ii) energy metabolism, iii) heat shock proteins, iv) oxidative stress, v) regulation of cellular processes and binding. Among the proteins, PHKA1 and STBD1 correlated with all four traits, as did the GO biological process 'generation of precursor metabolites and energy'. Optimal regression models explained a high level (58-71%) of phenotypic variability with proteomic data for each quality trait. The results of this study propose several regression equations and biomarkers to explain the variability of multiple beef eating quality traits. Thanks to annotation and network analyses, they further suggest protein interactions and mechanisms underpinning the physiological processes regulating these key quality traits. SIGNIFICANCE: The proteomic profiles of animals with divergent quality profiles have been compared in numerous studies; however, a wide range of phenotypic variation is required to better understand the mechanisms underpinning the complex biological pathways correlated with beef quality and protein interactions. We used multivariate regression analyses and bioinformatics to analyse shotgun proteomics data to decipher the molecular signatures involved in beef texture and flavour variations with a focus on multiple quality traits. We developed multiple regression equations to explain beef texture and flavour. Additionally, potential candidate biomarkers correlated with multiple beef quality traits are suggested, which could have utility as indicators of beef overall sensory quality. This study explained the biological process responsible for determining key quality traits such as tenderness, chewiness, stringiness, and flavour in beef, which will provide support for future beef proteomics studies.

Validation of protein biological markers of lamb meat quality characteristics based on the different muscle types

This work investigated the ability of 8 potential biomarkers (phosphoglycerate kinase-1 (PGK1), pyruvate kinase-M2 (PKM2), phosphoglucomutase-1 (PGM1), β-enolase (ENO3, myosin-binding protein-C (MYBPC1), myosin regulatory light chain-2 (MYLPF), troponin C-1 (TNNC1) and troponin I-1 (TNNI1)) to characterize meat quality by analyzing their relative abundance and enzymatic activity. Two different meat quality groups (Quadriceps femoris (QF) and Longissimus thoracis (LT) muscles) were selected at 24 h postmortem from 100 lamb carcasses. The relative abundance of PKM2, PGK1, PGM1, ENO3, MYBPC1, MYLPF, and TNNI1 was significantly different between LT and QF muscle groups (P < 0.01). Moreover, PKM, PGK, PGM, and ENO activity in LT muscle group was significantly lower than that in QF muscle (P < 0.05). Suggesting that PKM2, PGK1, PGM1, ENO3, MYBPC1, MYLPF, and TNNI1 can be used as robust biomarkers of lamb meat quality, providing the reference for understanding the molecular mechanism of postmortem meat quality formation in future.

Genome-Wide Re-Sequencing Data Reveals the Population Structure and Selection Signatures of Tunchang Pigs in China

Tunchang pig is one population of Hainan pig in the Hainan Province of China, with the characteristics of delicious meat, strong adaptability, and high resistance to diseases. To explore the genetic diversity and population structure of Tunchang pigs and uncover their germplasm characteristics, 10 unrelated Tunchang pigs were re-sequenced using the Illumina NovaSeq 150 bp paired-end platform with an average depth of 10×. Sequencing data from 36 individuals of 7 other pig breeds (including 4 local Chinese pig breeds (5 Jinhua, 5 Meishan, 5 Rongchang, and 6 Wuzhishan), and 3 commonly used commercial pig breeds (5 Duorc, 5 Landrace, and 5 Large White)) were downloaded from the NCBI public database. After analysis of genetic diversity and population structure, it has been found that compared to commercial pigs, Tunchang pigs have higher genetic diversity and are genetically close to native Chinese breeds. Three methods, FST, θπ, and XP-EHH, were used to detect selection signals for three breeds of pigs: Tunchang, Duroc, and Landrace. A total of 2117 significantly selected regions and 201 candidate genes were screened. Gene enrichment analysis showed that candidate genes were mainly associated with good adaptability, disease resistance, and lipid metabolism traits. Finally, further screening was conducted to identify potential candidate genes related to phenotypic traits, including meat quality (SELENOV, CBR4, TNNT1, TNNT3, VPS13A, PLD3, SRFBP1, and SSPN), immune regulation (CD48, FBL, PTPRH, GNA14, LOX, SLAMF6, CALCOCO1, IRGC, and ZNF667), growth and development (SYT5, PRX, PPP1R12C, and SMG9), reproduction (LGALS13 and EPG5), vision (SLC9A8 and KCNV2), energy metabolism (ATP5G2), cell migration (EPS8L1), and olfaction (GRK3). In summary, our research results provide a genomic overview of the genetic variation, genetic diversity, and population structure of the Tunchang pig population, which will be valuable for breeding and conservation of Tunchang pigs in the future.

Integrating identification and targeted proteomics to discover the potential indicators of postmortem lamb meat quality

The aim of this study was to identify the potential indicators of lamb meat quality by TMT and PRM-based proteomics combined with bioinformatic analysis. Lamb muscles were divided into three different meat quality groups (high, middle and low) according to tenderness (shear force, MFI value), colour (a* value, R630/580), and water-holding capacity (cooking loss, drip loss) at 24 h postmortem. The results showed that the abundance of phosphoglycerate kinase 1 (PGK1), β-enolase (ENO3), myosin-binding protein C (MYBPC1) and myosin regulatory light chain 2 (MYLPF) was significantly different in the three groups and could be used as potential indicators to characterize meat quality. Moreover, the postmortem processes of glycolysis, oxidative phosphorylation, and muscle contraction remarkably changed in different groups, and were the key biological pathways influencing meat quality. Overall, this study depicted the proteomic landscape of meat that furthers our understanding of the molecular mechanism of meat quality and provides a reference for developing non-destructive detection technology for meat quality.

First insights into the dynamic protein changes in goat Semitendinosus muscle during the post-mortem period using high-throughput proteomics

Proteomics plays a key and insightful role in meat research in the post-genomic era. This study aimed to unveil using a shotgun proteomics approach the temporal dynamic changes in early post-mortem proteome of goat Semitendinosus muscle. Therefore, the evolution and comparison of the muscle proteome over three post-mortem times (1, 8, and 24 h) was assessed. The temporal proteomics profiling quantified 748 proteins, from which 174 were differentially abundant (DAPs): n = 55 between 1 h versus 8 h, n = 52 between 8 h versus 24 h, and n = 154 between 1 h versus 24 h. The DAPs belong to myriad interconnected pathways. Binding, transport and calcium homeostasis, as well as muscle contraction and structure, exhibited an equivalent contribution during post-mortem, demonstrating their central role. Catalytic, metabolism and ATP metabolic process, and proteolysis were active pathways from the first hours of animal bleeding. Conversely, oxidative stress, response to hypoxia and cell redox homeostasis along chaperones and heat shock proteins accounted for the large proportion of the biochemical processes, more importantly after 8 h post-mortem. Overall, the conversion of muscle into meat is largely orchestrated by energy production as well as mitochondrial metabolism and homeostasis through calcium and permeability transition regulation. The study further evidenced the role of ribosomal proteins in goat post-mortem muscle, signifying that several proteins experiencing changes during storage, also undergo splicing modifications, which is for instance a mechanism known for mitochondrial proteins. Overall, temporal proteomics profiling of early post-mortem muscle proteome offers an unparalleled view of the sophisticated post-mortem biochemical and proteolytic events associated with goat meat quality determination.

A strategy to link the changes in the quality traits of Japanese sea bass (Lateolabrax japonicus) muscle and proteins in its exudate during cold storage using mass spectrometry

In this study, Japanese sea bass (Lateolabrax japonicus) was used as a model to link the changes in the quality traits of fish muscle during storage to the change of protein in muscle exudate. Matrix-assisted laser desorption time-of-flight mass spectrometry (MALDI-TOF MS) combined with variables importance in projection (VIP) analysis, and high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), were applied to identify the proteins by analyzing the enzymatic hydrolysates of exudates of fish muscle. The link in the identified proteins to the change in the quality traits of fish muscle during storage was explored using pyramid diagrams. Nine proteins were identified from the exudate of Japanese sea bass muscle during 12 days of storage at 4 °C. Of these, four proteins, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), heat shock protein 90 (HSP90), and peroxiredoxin 1 (PRX1), and beta-actin were found to be responsible for the changes in the quality traits of fish muscle. It is promising to correlate the changes in the quality traits of fish muscle and proteins in muscle exudate via MS-based protein identification and the construction of a relationship diagram to understand the mechanism of muscle change at the molecular level.

Mechanism of textural properties changes of cooked chicken in early postmortem: Effect of protein degradation induced by calpain on heating shrinkage

Although the relationship between myofibrillar protein status and cooked meat quality is well documented, its underlying mechanism still need to be clarified. In this study, the effect of calpain-induced myofibrillar degradation on the cooked chicken quality was discussed by comparing the difference in muscle fiber's heat shrinkage state. In early postmortem, the protein around Z-line was degraded, which would cause the unstable Z-line and released into the sarcoplasm, according to WB results. This phenomenon will aggravate the lateral contraction of muscle fragments during the heating process. Then along comes a higher cooking loss and lower texture properties of meat. Above findings indicate that the Z-line dissociation caused by calpain in the early postmortem period is an essential reason for the quality difference of mature chicken. This study provided a fresh light on the mechanism underlying the impact of myofibril degradation in the early postmortem on the quality of cooked chicken.

A TMT-based proteomic approach for investigating the effect of electron beam irradiation on the textural profiles of Litopenaeus vannamei during chilled storage

To elucidate the effect of electron beam irradiation (EBI) on the textural quality of Litopenaeus vannamei, the tandem-mass-tag labeled proteomic method was conducted to illustrate the protein changes in shrimp muscle. The results suggested that shrimp irradiated with 5 kGy exhibited optimum textural traits of hardness, springiness, and chewiness. In total, 486 proteins were identified as differentially abundance proteins (DAPs) in multiple comparison groups. Bioinformatics analysis revealed that most of DAPs participated in cellular process, binding, and catalytic. etc. Various signaling pathways, such as RNA transport and oxidative phosphorylation, were notably enriched by DAPs. The correlation analysis indicated that some DAPs such as Myosin-XVIIIa, projectin, and beta-thymosin 3 were remarkably correlated with the textural properties, which could be proposed as potential biomarkers to assess the irradiation-induced textural variation in shrimp. This study provided an insightful understanding at the protein level to improve the application of EBI to shrimp preservation.

iTRAQ-based proteomic analysis reveals the underlying mechanism of postmortem tenderization of refrigerated porcine Longissimus thoracis et lumborum muscle

The isobaric tags for relative and absolute quantitation (iTRAQ) technology was used for differential proteomic analysis of refrigerated porcine Longissimus thoracis et lumborum (LTL) muscle at different time points postmortem (45 min, 4 h, 8 h, 12 h, 24 h, 48 h, 72 h and 96 h) to mechanistically elucidate the postmortem tenderization. Compared with the proteins identified in porcine LTL muscle at 45 min postmortem (control), 862 proteins were significantly expressed at 4 h, 8 h, 12 h, 24 h, 48 h, 72 h and 96 h postmortem. Moreover, clustering and path analysis showed that the quality traits of porcine LTL muscle, including pH, shear force, myofibril fragmentation index, correlated significantly with 2, 6 and 6 differentially expressed proteins, respectively, with the lowest or highest expression at 8 h or 12 h postmortem. Overall, the tenderness of refrigerated porcine LTL muscle might be significantly affected by changes in quality traits at 8 h and 12 h postmortem.

Relationships between the abundance of 29 proteins and several meat or carcass quality traits in two bovine muscles revealed by a combination of univariate and multivariate analyses

We aimed to evaluate the relationships between meat or carcass properties and the abundance of 29 proteins quantified in two muscles, Longissimus thoracis and Rectus abdominis, of Rouge des Prés cows. The relative abundance of the proteins was evaluated using a high throughput immunological method: the Reverse Phase Protein array. A combination of univariate and multivariate analyses has shown that small HSPs (CRYAB, HSPB6), fast glycolytic metabolic and structural proteins (MYH1, ENO3, ENO1, TPI1) when assayed both in RA and LT, were related to meat tenderness, marbling, ultimate pH, as well as carcass fat-to-lean ratio or conformation score. In addition to some small HSP, ALDH1A1 and TRIM72 contributed to the molecular signature of muscular and carcass adiposity. MYH1 and HSPA1A were among the top proteins related to carcass traits. We thus shortened the list to 10 putative biomarkers to be considered in future tools to manage both meat and carcass properties. SIGNIFICANCE: In three aspects this manuscript is notable. First, this is the first proteomics study that aims to evaluate putative biomarkers of both meat and carcass qualities that are of economic importance for the beef industry. Second, the relationship between the abundance of proteins and the carcass or meat traits were evaluated by a combination of univariate and multivariate analyses on 48 cows that are representative of the biological variability of the traits. Third, we provide a short list of ten proteins to be tested in a larger population to feed the pipeline of biomarker discovery.

Application of 2-D DIGE to study the effect of ageing on horse meat myofibrillar sub-proteome

Considering the high relevance of meat tenderness for consumer acceptability, the aim of this study was to investigate post-mortem changes in myofibrillar sub-proteome in steaks from longissimus thoracis et lumborum muscle of six Hispano-Bretón horses. Indeed, the ageing process that leads to meat tenderization has been scarcely studied in this species. Steaks (n = 24) were aged (4 °C) in the dark under vacuum for 0, 7, 14 and 21 days and the myofibrillar sub-proteome was extracted. Using 2-D DIGE minimal labelling, 35 spots that were differentially abundant between 0 and 21 days aged meat were detected. Of them, 24 were analysed by LC-MS/MS, identifying a total of 29 equine proteins. These were structural and metabolic proteins, and among them, four (Actin, Troponin T and Myosin binding proteins 1 and 2) were selected for Western blot analysis, reporting changes in their abundance after 0, 7, 14 and 21 days of ageing. Results revealed that they should be further studied as potential protein biomarkers of horse meat tenderization. Additionally, several protein fragments increased after ageing, as was the case of glyceraldehyde-3-phosphate dehydrogenase. Fragments of this protein were present in four protein spots, and their study could be useful for monitoring horse meat tenderization. SIGNIFICANCE: Tenderization during ageing has been widely studied in meat from several farm animal species; however, both research and standardized ageing practices are lacking for the particular case of horse meat. In this regard, this study presents novel proteomic findings related to post-mortem evolution of horse muscle proteins. Acquired knowledge would support the development and optimization of efficient ageing practices by horse meat industry.

Cooking Delicacy with Ice-Nanobubble Isolation Switches Stewing to 'BBQ'

The key role of ice in cooking has been neglected. Here, we found negatively charged bulk nanobubbles (BNBs: average size ~60 nm and zeta potential <-20 mV) can be generated in ice-melted water through freeze/thaw-induced cavitation when we studied a local delicacy, 'ice-stewed mutton'. Freeze/thaw-induced BNBs are so robust that they can, in turn, isolate food from water; in this way, they protect and enhance the delicacy by protecting protein structures and preventing flavorful components from being lost. In comparison to cooking with ordinary water, cooking with ice can switch 'stewing' to 'BBQ', which has been proved experimentally via diverse characterization from the nano to micro scale. This study not only provides a novel mechanism for ice-based cooking but also might shed light on the design of potential applications of BNBs in chemical engineering and biomedicine.

Effect of Animal Age, Postmortem Calcium Chloride Marination, and Storage Time on Meat Quality Characteristics of M. longissimus thoracis et lumborum of Buffalo Bulls

This study investigated the effect of animal age, calcium chloride marination, and storage time on meat quality characteristics of buffalo bulls to suggest a cost-effective method of improving buffalo meat quality. The current study was designed considering the importance of buffalo meat and the usage of meat from spent buffalo animals in local markets of South Asian countries. A total of 36 animals comprised of 18 young and 18 spent buffalo bulls were selected. After slaughtering and 24 h of postmortem chilling, striploins were separated and cut into 16 steaks and equally divided into two groups, i.e., either marinated with calcium chloride or not. Meat quality characteristics were recorded on 0, 2, 4, 6, 8, and 10 days of storage. The results showed that the pH value of young animals was higher than the value of spent animals and pH was increased over the storage time. Color b*, C*, and h* values were higher in spent animals as compared with the young animals; however, values of colors L* and h* were higher and a* was lower in marinated samples than the values of non-marinated samples. Color a* and C* values were increased and h* was decreased with lengthening the storage time. The meat cooking loss was higher in marinated and the water-holding capacity was higher in non-marinated meat samples. Shear force values were lower in young animals and marinated samples than the values of spent animals and non-marinated meat samples, respectively. Sensory characteristic scores of marinated samples were better than the non-marinated samples. In conclusion, calcium chloride marination can be used to improve the quality characteristics of buffalo meat.

Metabolic, proteomic and microbial changes postmortem and during beef aging

The purpose of this review is to provide an overview of the current knowledge about proteomic and metabolic changes in beef, the microbiological alteration postmortem and during aging, and observe the influence on beef quality parameters, such as tenderness, taste and flavor. This review will also focus on the different aging types (wet- and dry-aging), the aging or postmortem time of beef and their effect on the proteome and metabolome of beef. The Ca2+ homeostasis and adenosine 5'-triphosphate breakdown are the main reactions in the pre-rigor phase. After rigor mortis, the enzymatic degradation of connective tissues and breakdown of energy metabolism dominate molecular changes in beef. Important metabolic processes leading to the formation of saccharides, nucleotides, organic acids (e.g. lactic acid), creatine and fatty acids are considered in this context as possible flavor precursors or formers of beef flavor and taste. Flavor precursors are substrates for lipid oxidation, Strecker degradation and Maillard reaction during cooking or roasting. The findings presented should serve as a basis for a better understanding of beef aging and its molecular effects and are intended to contribute to meeting the challenges of improving beef quality.

Transcriptomic Analysis of the Porcine Gut in Response to Heat Stress and Dietary Soluble Fiber from Beet Pulp

This study aimed to investigate the impact of heat stress (HS) and the effects of dietary soluble fiber from beet pulp (BP) on gene expression (differentially expressed genes, DEGs) of the porcine jejunum. Out of the 82 DEGs, 47 genes were up-regulated, and 35 genes were downregulated between treatments. The gene ontology (GO) enrichment analysis showed that the DEGs were related mainly to the actin cytoskeleton organization and muscle structure development in biological processes, cytoplasm, stress fibers, Z disc, cytoskeleton, and the extracellular regions in cellular composition, and actin binding, calcium ion binding, actin filament binding, and pyridoxal phosphate binding in the molecular function. The KEGG pathway analysis showed that the DEGs were involved in hypertrophic cardiomyopathy, dilated cardiomyopathy, vascular smooth muscle contraction, regulation of actin cytoskeleton, mucin type O-glycan biosynthesis, and African trypanosomiasis. Several of the genes (HSPB6, HSP70, TPM1, TAGLN, CCL4) in the HS group were involved in cellular oxidative stress, immune responses, and cellular differentiation. In contrast, the DEGs in the dietary BP group were related to intestinal epithelium integrity and immune response to pathogens, including S100A2, GCNT3, LYZ, SCGB1A1, SAA3, and ST3GAL1. These findings might help understand the HS response and the effect of dietary fiber (DF) regarding HS and be a valuable reference for future studies.

The Changes Occurring in Proteins during Processing and Storage of Fermented Meat Products and Their Regulation by Lactic Acid Bacteria

Protein, which is the main component of meat, is degraded and oxidized during meat fermentation. During fermentation, macromolecular proteins are degraded into small peptides and free amino acids, and oxidation leads to amino acid side chain modification, molecular crosslinking polymerization, and peptide chain cleavage. At different metabolic levels, these reactions may affect the protein structure and the color, tenderness, flavor, and edible value of fermented meat products. Lactic acid bacteria are currently a research hotspot for application in the fermented meat industry. Its growth metabolism and derivative metabolites formed during the fermentation of meat products regulate protein degradation and oxidation to a certain extent and improve product quality. Therefore, this paper mainly reviews the changes occurring in proteins in fermented meat products and their effects on the quality of the products. Referring to studies on the effects of lactic acid bacteria on protein degradation and oxidation from all over the world, this review aims to provide a relevant reference for improving the quality of fermented meat products.

Tandem mass tag labeling to assess proteome differences between intermediate and very tender beef steaks

Tenderness is considered as one of the most important quality attributes dictating consumers' overall satisfaction and future purchasing decisions of fresh beef. However, the ability to predict and manage tenderness has proven very challenging due to the numerous factors that contribute to variation in end-product tenderness. Proteomic profiling allows for global examination of differentially abundant proteins in the meat and can provide new insight into biological mechanisms related to meat tenderness. Hence, the objective of this study was to examine proteomic profiles of beef longissimus lumborum (LL) steaks varying in tenderness, with the intention to identify potential biomarkers related to tenderness. For this purpose, beef LL muscle samples were collected from 99 carcasses at 0 and 384 h postmortem. Based on Warner-Bratzler shear force values at 384 h, 16 samples with the highest (intermediate tender, IT) and lowest (very tender, VT) values were selected to be used for proteomic analysis in this study (n = 8 per category). Using tandem mass tag-based proteomics, a total of 876 proteins were identified, of which 51 proteins were differentially abundant (P < 0.05) between the tenderness categories and aging periods. The differentially identified proteins encompassed a wide array of biological processes related to muscle contraction, calcium signaling, metabolism, extracellular matrix organization, chaperone, and apoptosis. A greater (P < 0.05) relative abundance of proteins associated with carbohydrate metabolism and apoptosis, and a lower (P < 0.05) relative abundance of proteins involved in muscle contraction was observed in the VT steaks after aging compared with the IT steaks, suggesting that more proteolysis occurred in the VT steaks. This may be explained by the greater (P < 0.05) abundance of chaperonin and calcium-binding proteins in the IT steaks, which could have limited the extent of postmortem proteolysis in these steaks. In addition, a greater (P < 0.05) abundance of connective tissue proteins was also observed in the IT steaks, which likely contributed to the difference in tenderness due to added background toughness. The established proteomic database obtained in this study may provide a reference for future research regarding potential protein biomarkers that are associated with meat tenderness.

Oxidative Stress Contributes to Cytoskeletal Protein Degradation of Esox lucius through Activation of Mitochondrial Apoptosis during Postmortem Storage

This study investigated the role of oxidative stress in the mitochondrial apoptotic pathways and structural protein degradation of fish during postmortem storage by measuring oxidative stress levels, mitochondrial antioxidant enzyme activity, mitochondrial dysfunction, apoptotic factors, and structural protein degradation (n = 3). The results revealed that reactive oxygen species (ROS) increased gradually within the first 12 h and then decreased (p < 0.05) in mitochondria. Lipid peroxidation was increased, and superoxide dismutase, catalase, and glutathione peroxidase activities were decreased in mitochondria (p < 0.05). Furthermore, oxidative stress induced mitochondrial membrane opening, mitochondrial swelling, as well as the depolarization of mitochondrial potential. This led to an increase in the release of cytochrome c from mitochondria and caspase-3 activation. Ultimately, oxidative stress promoted small protein degradation (troponin-T and desmin) and induced myofibril susceptibility to proteolysis. These observations confirmed that oxidative stress mediated the activation of mitochondrial apoptotic factors-promoted protein degradation, initiating the deterioration of fish muscle through the mitochondrial apoptotic pathway.

Ultrasonication of Milk Decreases the Content of Exosomes and MicroRNAs in an Exosome-Defined Rodent Diet

BACKGROUND

Bovine milk exosomes (BMEs) harbor regulatory proteins, lipids, and microRNAs. Consumption of an exosome- and RNA-depleted (ERD) diet elicited phenotypes compared with controls fed an exosome- and RNA-sufficient (ERS) diet in mice. All other ingredients were identical in the diets. ERD and ERS diets were prepared by substituting ultrasonicated and nonultrasonicated milk, respectively, for casein in the AIN-93G formulation.

OBJECTIVES

The objective of this study was to assess the effect of ultrasonication of milk on exosome content and bioavailability, and cargo content.

METHODS

Bovine milk was ultrasonicated and exosomes were isolated by ultracentrifugation [ultrasonicated exosomes (USEs)]; controls were not ultrasonicated [nonultrasonicated exosomes (NSEs)]. Exosome count, size, and morphology were assessed using a nanoparticle tracker and electron microscopy. RNAs, lipids, and proteins were analyzed by RNA sequencing and MS. Intestinal transport, bioavailability, and distribution were measured by using fluorophore-labeled USEs and NSEs in Caco-2 cells, FHs 74 Int cells, and C57BL/6J mice (n = 3; age: 6-8 wk).

RESULTS

The exosome count was 76% ± 22% lower in USEs than in NSEs (P < 0.05). Ultrasonication caused a degradation of ≤100% of microRNAs. USEs and NSEs contained 145 and 332 unique lipid signatures, respectively (P < 0.05). We detected a total of 525 and 484 proteins in USEs and NSEs, respectively. The uptake of USEs decreased by 46% ± 30% and 40% ± 27% compared with NSEs in Caco-2 and FHs 74 Int cells, respectively (P < 0.05). The hepatic accumulation of USEs was 48% ± 28% lower than the accumulation of NSEs in mice (P < 0.05).

CONCLUSIONS

Ultrasonication of milk depletes bioavailable BMEs in studies of Caco-2 cells, FHs 74 Int cells, and C57BL/6J mice and causes a near-complete degradation of microRNA cargos.

Quantitative proteomics reveals the relationship between protein changes and off-flavor in Russian sturgeon (Acipenser gueldenstaedti) fillets treated with low temperature vacuum heating

This study aimed to reveal the molecular mechanisms associated with off-flavor generation in sturgeon fillets treated by low temperature vacuum heating (LTVH). Label-free quantitative proteomics was used to identify 120 favor-related proteins, 27 proteins were screened as differentially expressed for bioinformatics analysis. 17 of KEGG pathways were identified. Particularly, proteins involved in proteasome and peroxisome were highly correlated with off-flavor formation. They were primarily implicated in the structures of proteins, including binding and proteasome pathways. The results indicated that the LTVH reduced the binding sites by down-regulating protease and superoxide dismutase expression. LTVH increased the myofibrillar protein and sulfhydryl content and decreased the total volatile basic nitrogen and thiobarbituric acid reactive substance, which confirmed that protein oxidation was related to off-flavor. This proteomics study provided new insights into the off-flavor of sturgeon with LTVH, and proposed potential link between biological processes and off-flavor formation.

The Quality Changes and Proteomic Analysis of Cattle Muscle Postmortem during Rigor Mortis

Rigor mortis occurs in a relatively early postmortem period and is a complex biochemical process in the conversion of muscle to meat. Understanding the quality changes and biomarkers during rigor mortis can provide a theoretical basis for maintaining and improving meat quality. Herein, a tandem mass tag proteomic method is used to investigate the effects of differentially expressed proteins on the meat quality of cattle Longissimus lumborum muscle postmortem (0, 6, and 24 h). The pH, total sulfhydryl content and sarcomere length decrease significantly during storage. In contrast, meat color values (L*, a*, and b*) and the myofibril fragmentation index increase significantly. Altogether, 147 differentially expressed proteins are identified, most being categorized as metabolic enzymes, mitochondrial proteins, necroptosis and ferroptosis proteins and structural proteins. The results also reveal additional proteins that are potentially involved in rigor mortis, such as cardiac phospholamban, acetyl-coenzyme A acyltransferase, and ankyrin repeat domain 2. The current results provide proteomic insights into the changes in meat quality during rigor mortis.

Proteomic analysis of exudates in thawed fillets of bighead carp (Hypophthalmichthys nobilis) to understand their role in oxidation of myofibrillar proteins

For frozen fillets, the formation of ice crystals destroys the integrity of cell and organelle membranes and causes the release of enzymes that are capable of catalyzing oxidation of myofibrillar proteins (MPs). Exudates from fresh, freeze-thaw (F-T) treated, and frozen stored fillets that were contained those enzymes were collected to explore the protein composition and changes in abundance of the main protein oxidation-related enzymes. Results indicated that enzymes with oxidative capacity were up-regulated and some antioxidant enzymes were down-regulated in exudates collected from 5 months frozen fillets. Changes in abundance of MPs in exudates suggested that degradation of MPs in thawed fillets was a comprehensive result of the F-T treatment, enzymatic degradation, and protein oxidation. The oxidative capacity of exudates was confirmed because incubation with exudates enhanced carbonyls and Schiff bases contents in MPs. Overall, the results of our study suggested that enzymes in exudates were a potential factor in protein oxidation in thawed fillets.

Growth Performance, Meat Quality and Antioxidant Status of Sheep Supplemented with Tannins: A Meta-Analysis

The objective of this study was to evaluate the effects of dietary supplementation with tannins (TANs) on productive performance, carcass characteristics, meat quality, oxidative stability, and blood serum antioxidant capacity of sheep through a meta-analysis. Using Scopus, Web of Science, ScienceDirect, and PubMed databases, a systematic search was performed for studies published in scientific journals that investigated the effects of TANs supplementation on the variables of interest. Only studies with weaned or older sheep were included. The data analyzed were extracted from 53 peer-reviewed publications. The sheep included in the present study were between 2 and 6 months old, and between 12 and 31 kg of body weight. The effects of TANs were analyzed using random-effects statistical models to examine the standardized mean difference (SMD) between treatments with TANs and control (no TANs). Heterogeneity was explored by meta-regression and a subgroup analysis was performed for covariates that were significant. Supplementation with TANs did not affect dry matter intake, pH, color (L* and b*), Warner-Bratzler shear force, cooking loss and meat chemical composition (p > 0.05). Supplementation with TANs increased daily weight gain (SMD = 0.274, p < 0.05), total antioxidant capacity (SMD = 1.120, p < 0.001), glutathione peroxidase enzyme activity (SMD = 0.801, p < 0.001) and catalase (SMD = 0.848, p < 0.001), and decreased malondialdehyde (MDA) concentration in blood serum (SMD = -0.535, p < 0.05). Supplementation with TANs decreased feed conversion rate (SMD = -0.246, p < 0.05), and the concentration of MDA (SMD = -2.020, p < 0.001) and metmyoglobin (SMD = -0.482, p < 0.05) in meat. However, meat redness (SMD = 0.365), hot carcass yield (SMD = 0.234), cold carcass yield (SMD = 0.510), backfat thickness (SMD = 0.565) and the Longissimus dorsi muscle area (SMD = 0.413) increased in response to TANs supplementation (p < 0.05). In conclusion, the addition of tannins in sheep diets improves productive performance, antioxidant status in blood serum, oxidative stability of meat and some other characteristics related to meat and carcass quality.