Proteome changes during meat aging in tough and tender beef suggest the importance of apoptosis and protein solubility for beef aging and tenderization

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.

Electrical stimulation to improve meat quality: Factors at interplay, underlying biochemical mechanisms and a second look into the molecular pathways using proteomics

Ensuring consistent beef eating quality is paramount for meeting consumer demands and sustaining the meat industry. Electrical stimulation (ES) is a post-slaughter intervention used to accelerate post-mortem glycolysis, to avoid cold shortening, to control the tenderization rate of meat through sophisticated physical, chemical and biochemical mechanisms including proteolysis, to improve beef tenderness and to achieve normal pHu that might lead to positive impact on color. This review comprehensively examines the multifaceted effects of ES on beef quality, encompassing factors and settings influencing its efficacy and the underlying biochemical mechanisms revealed using traditional biochemistry methods. It then delves into the molecular pathways modulated by ES, as unveiled by muscle proteomics, aiming to provide a second look and an unprecedented understanding of the underlying biochemical mechanisms through an integrative proteomics analysis of low-voltage ES (LVES) proteomics studies. The proteins changing as a result of ES were gathered in a compendium of 67 proteins, from which 14 were commonly identified across studies. In-depth bioinformatics of this compendium allowed a comprehensive overview of the molecular signatures and interacting biochemical pathways behind electrically stimulated beef muscles. The proteins belong to interconnected molecular pathways including the ATP metabolic process and glycolysis, muscle structure and contraction, heat shock proteins, oxidative stress, proteolysis and apoptosis. Understanding the intricate interplay of molecular pathways behind ES could improve the efficiency of beef production, ensuring consistent meat quality and meeting consumer expectations. The integrative analysis approach performed in this study holds promise for the meat industry's sustainability and competitiveness.

Effects of Premortem Stress on Protein Expression, Steak Color, Oxidation, and Myofibrillar Fragmentation Index in the Longissimus Lumborum

Forty castrated Holstein calves underwent an adrenocorticotropic hormone (ACTH) challenge to assess the effects of premortem stress on the longissimus lumborum (LL) following harvest. LL biopsies were collected before the challenge, at different harvest times (2, 12, 24, and 48 h; n = 10), and after 14 d aging. The expression of small heat shock proteins (SHSPs), deglycase 1 (DJ-1), and troponin were analyzed. Blood was analyzed throughout the ACTH challenge and at harvest for cortisol, oxidative stress, and complete blood count (CBC). Color and myofibrillar fragmentation index (MFI) were measured in aged samples. Unexpectedly, calves from different harvest times differed (p = 0.05) in cortisol response. Calves were divided into two different cortisol response groups (high or low; n = 20). Statistical analysis assessed the effects of cortisol response (n = 20), harvest time (n = 10), and their interaction. Harvest time altered SHSPs (p = 0.03), DJ-1 (p = 0.002), and troponin (p = 0.02) expression. Harvest time and cortisol response impacted steak color (p < 0.05), and harvest time altered steak pH (p < 0.0001). Additionally, various CBCs were changed (p < 0.05) by harvest time. Harvest time changed (p = 0.02) MFI. These data demonstrate that the protein expression, color, and MFI of the LL may be influenced by premortem stress.

Identification of Candidate Genes and Pathways Linked to the Temperament Trait in Sheep

Temperament can be defined as the emotional variability among animals of the same species in response to the same stimulus, grouping animals by their reactivity as nervous, intermediate, or calm. Our goal was to identify genomic regions with the temperament phenotype measured by the Isolation Box Test (IBT) by single-step genome-wide association studies (ssGWAS). The database consisted of 4317 animals with temperament records, and 1697 genotyped animals with 38,268 effective Single Nucleotide Polymorphism (SNP) after quality control. We identified three genomic regions that explained the greatest percentage of the genetic variance, resulting in 25 SNP associated with candidate genes on chromosomes 6, 10, and 21. A total of nine candidate genes are reported for the temperament trait, which is: PYGM, SYVN1, CAPN1, FADS1, SYT7, GRID2, GPRIN3, EEF1A1 and FRY, linked to the energetic activity of the organism, synaptic transmission, meat tenderness, and calcium associated activities. This is the first study to identify these genetic variants associated with temperament in sheep, which could be used as molecular markers in future behavioral research.

Physiological and transcriptomic analysis dissects the molecular mechanism governing meat quality during postmortem aging in Hu sheep (Ovis aries)

Introduction

Hu sheep, known for its high quality and productivity, lack fundamental scientific research in China.

Methods

This study focused on the effects of 24 h postmortem aging on the meat physiological and transcriptomic alteration in Hu sheep.

Results

The results showed that the 24 h aging process exerts a substantial influence on the mutton color, texture, and water content as compared to untreated group. Transcriptomic analysis identified 1,668 differentially expressed genes. Functional enrichment analysis highlighted the importance of glycolysis metabolism, protein processing in endoplasmic reticulum, and the FcγR-mediated phagocytosis pathway in mediating meat quality modification following postmortem aging. Furthermore, protein-protein interaction analysis uncovered complex regulatory networks involving glycolysis, the MAPK signaling pathway, protein metabolism, and the immune response.

Discussion

Collectively, these findings offer valuable insights into the molecular mechanisms underlying meat quality changes during postmortem aging in Hu sheep, emphasizing the potential for improving quality control strategies in mutton production.

Relationship between peptides and the change in quality characteristics of beef strip loin (M. longissimus lumborum) and tenderloin (M. psoas major)

Peptides in fresh and aged beef strip loin (M. longissimus lumborum) and tenderloin (M. psoas major) were quantified to investigate the relationship between proteolysis-induced peptides and beef quality characteristics. A total of 409 and 450 peptides were quantified from strip loin and tenderloin, respectively, and found to be significantly correlated to beef quality characteristics. Changes in redness and yellowness were significantly correlated to the peptides derived from G3P, ENOB, and KCRM in both muscles during 14 days of storage. The peptides produced from MYG, ENOB, HBA, PGK1, and TPIS were strongly associated with improved tenderness, while those derived from major myofibrillar proteins, such as MYH1, MYH2, ACTS, and DESM, were associated with changes in tenderloin color. These results improve our understanding of the association between peptides and changes in meat quality during cold storage, indicating that proteolysis-induced peptides can be indicators of the quality characteristics of fresh and aged meat.

Impact of sampling location and aging on the Longissimus thoracis et lumborum muscle proteome of dry-aged beef

This study aimed to explore the differences in the proteome and molecular pathways between two sampling locations (external, internal) of bovine Longissimus thoracis et lumborum (LTL) muscles at 0, 21, and 28 days of dry-aging (i.e. 3, 24, and 31 days post-mortem). It further assessed the impact of post-mortem aging on the meat proteome changes and the biological processes at interplay. Proteins related to defence response to bacterium and regulation of viral entry into host cell were identified to be more abundant on the external location before dry-aging, which may be associated to the oxidative conditions and microbial activity to which post-mortem muscle is exposed during dressing, chilling, and/or quartering of the carcasses. This highlights the relevance of sampling from interior tissues when searching for meat quality biomarkers. As dry-aging progressed, the meat proteome and related biological processes changed differently between sampling locations; proteins related to cell-cell adhesion and ATP metabolic processes pathways were revealed in the external location at 21 and 28 days, respectively. On the other hand, the impact of aging on the proteome of the interior meat samples, evidenced that muscle contraction and structure together with energy metabolism were the major pathways driving dry-aging. Additionally, aging impacted other pathways in the interior tissues, such as regulation of calcium import, neutrophil activation, and regeneration. Overall, the differences in the proteome allowed discriminating the three dry-aging times, regardless of the sampling location. Several proteins were proposed for validation as robust biomarkers to monitor the aging process (tenderization) of dry-aged beef: TTN, GRM4, EEF1A1, LDB3, CILP2, TNNT3, GAPDH, SERPINI1, and OMD.

Multi-Omics Approaches to Improve Meat Quality and Taste Characteristics

With rapid advances in meat science in recent decades, changes in meat quality during the pre-slaughter phase of muscle growth and the post-slaughter process from muscle to meat have been investigated. Commonly used techniques have evolved from early physicochemical indicators such as meat color, tenderness, water holding capacity, flavor, and pH to various omic tools such as genomics, transcriptomics, proteomics, and metabolomics to explore fundamental molecular mechanisms and screen biomarkers related to meat quality and taste characteristics. This review highlights the application of omics and integrated multi-omics in meat quality and taste characteristics studies. It also discusses challenges and future perspectives of multi-omics technology to improve meat quality and taste. Consequently, multi-omics techniques can elucidate the molecular mechanisms responsible for changes of meat quality at transcriptome, proteome, and metabolome levels. In addition, the application of multi-omics technology has great potential for exploring and identifying biomarkers for meat quality and quality control that can make it easier to optimize production processes in the meat industry.

Contribution of mitochondria to postmortem muscle tenderization: a review

Postmortem meat tenderization is a process mediated by a series of biochemical reactions related to muscle cell death. Cell death is considered a sign that muscle has started to transform into meat. Mitochondria play a significant role in regulating and executing cell death, as they are an aggregation point for many cell death signals and are also the primary target organelle damaged by tissue anoxia. Mitochondrial damage is likely to have an expanded role in postmortem meat tenderization. This review presents current findings on mitochondrial damage induced by the accumulation of reactive oxygen species during postmortem anaerobic metabolism and on the impact of mitochondrial damage on proteolysis and discusses how this leads to improved tenderness during aging. The underlying mechanisms of mitochondrial regulation of postmortem muscle tenderization likely focus on the mitochondria's role in postmortem cell death and energy metabolism. The death process of postmortem skeletal muscle cells may exhibit multiple types, possibly involving transformation from autophagy to apoptosis and, ultimately, necroptosis or necrosis. Mitochondrial characteristics, especially membrane integrity and ATP-related compound levels, are closely related to the transformation of multiple types of dead postmortem muscle cells. Finally, a possible biochemical regulatory network in postmortem muscle tenderization is proposed.

Meat Quality Changes in Aged Pork Loin using Jeju Volcanic Scoria Earthenware

This study aimed to investigate changes in the quality of meat aged using Jeju scoria earthenware. Water-holding properties, pH, color, tenderization, fatty acid composition, and free amino acid characteristics of aged pork loin were evaluated to determine the effects of wet and dry (normal and Jeju Scoria) aging methods and aging time (0, 10, 20, 30, and 40 days) on meat quality. The aging methods altered pH and CIE L* after 10 days of aging. However, the aging method did not alter the pH and CIE L* of the aged pork loin after 10 days of aging. The shear force was significantly lower in the Scoria aging method than in the wet aging method after 10 and 20 days of aging. Both the normal and Scoria aging methods increased aging loss compared to the wet aging method, which could be attributed to longer air exposure times of the two non-packaged aging methods than in the packaged aging method. The scoria aging method had significantly higher contents and ratios of saturated (SFA) to mono-unsaturated fatty acids but lower ratios of poly-unsaturated fatty acids to SFA than the wet aging method. The content of most free amino acids significantly increased with aging time, especially those related to the sweet, and umami categories. In summary, this study suggests that the Scoria aging method provides positive aspects of eating quality, such as improvement of meat tenderness and taste, including umami, with minimum changes in the overall meat quality.

Analysis of physicochemical properties of dry-cured beef made from Hanwoo and Holstein meat distributed in South Korea

The purpose of the study is to check the possibility of developing dry-cured meat from Hanwoo (South Korean native cattle) and Holstein cattle considering the differences between breeds and use this data for the preparation and development of dry cured ham unique to South Korea. Same-grade Semitendinosus muscle from Hanwoo and Holstein was cured using a curing agent with 4.6% salt content at 4 °C for 7 days, and then aged for 70 days. Data was analyzed through physicochemical characterization, and the manufacturing period was established through weight loss, volatile basic nitrogen (VBN), thiobarbituric acid reactive substances (TBARS). Moisture content and weight loss of both samples significantly decreased during the manufacturing process (P < 0.05). TBARS was significantly higher in Hanwoo and VBN in Holstein (P < 0.05). According to the values of VBN (less than 20 mg/100 g) and TBARS (less than 2 mg MDA/kg), dry aging for 5 weeks is appropriate for both samples. The principal component analysis of 5 weeks-aged Holstein showed a dramatically changing trend due to myofibril fragmentation as indicated by Sodium dodecyl sulfate-polyacrylamide-gel electrophoresis. In addition, 5 weeks-aged Holstein contains methanethiol (cheese), butan-2-one (butter), and 3-3-ethyl-2-methyl-1,3-hexadiene (fatty acid-derive) compounds that represent fermentation and aging flavors. Therefore, the possibility of product development was confirmed by the 5-week aging of Holstein dry-cured ham.

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.

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.

Investigation of changes in proteomes of beef exudate and meat quality attributes during wet-aging

This study was performed to evaluate the effects of wet-aging (3, 7, 14, 21, and 28 d at 2 °C) on beef (longissimus lumborum muscles) exudate proteome and meat quality changes. The pH, purge loss, and tenderness of beef increased with aging (P < 0.05), while color and lipid oxidative stabilities decreased, especially when long-term (14 and 21 d) aged meat were repackaged and displayed under retail condition (P < 0.05). Nineteen proteins changed significantly with aging (FDR < 0.05), in which most of them progressively accumulated in exudates over aging periods. Combined with partial least squares discriminant analysis, 16 proteins (including 9 structural proteins, 3 metabolic enzymes, 1 heat shock protein, 2 binding proteins, and KBTBD10 protein) were screened as characteristic proteins that could be used for potential meat quality indication. These findings offered novel insight into the utilization of exudates for meat quality assessment.

Effect of hazelnut skin by-product supplementation in lambs' diets: Implications on plasma and muscle proteomes and first insights on the underlying mechanisms

This study aimed to evaluate the effect of hazelnut skin by-product supplementation on lamb meat quality characteristics and plasma and muscle proteomes. Twenty-two Valle del Belice male lambs were divided into two experimental groups: control (C), fed a maize-barley diet and hazelnut (H), fed hazelnut skin by-product as maize partial replacer in the concentrate diet. The meat of lambs fed hazelnut skin showed greater values of lightness, redness, yellowness, and chroma color parameters together with the highest myofibril fragmentation index. Two-dimensional electrophoresis and mass spectrometry applied on plasma proteome identified 20 protein spots corresponding to 18 unique gene names to be differently expressed due to hazelnut skin by-product substitution. For the early post-mortem muscle, 23 protein spots (42 unique gene names) were significantly up-regulated due to hazelnut skin by-product supplementation. Four proteins these being APOA1, PHB, ACTG1 and ALB, were found to be common to the two proteomes suggesting that these proteins could be candidate biomarkers to monitor in vita and post-mortem lamb meat quality traits. This study evidenced the main mechanisms involved in the supplementation of hazelnut skin by-product in lambs' diet and confirmed the possibility of using plasma proteome as a non-invasive way to predict lamb meat quality. SIGNIFICANCE: Maximizing the use of agro-industrial by-products as replacers of traditional feedstuff for improving animal products is one of the important challenges to preserving natural resources and guaranteeing environmental sustainability. Hazelnut (Corylus avellana L.) skin, obtained as a results of hazelnut roasting, represents a valuable by-products due to its high content in unsaturated fatty acids, tannins, and vitamins. Thus, including hazelnut skin by-product in small ruminant nutrition could reduce the costs of animal feedings for farmers as well as improve meat nutritional and sensorial characteristics. Additionally, monitoring the meat quality characteristics with fast, accurate, and non-invasive tools to find, before slaughter, animals with desired quality characteristics is of growing interest in the last years. In this regard, the objectives of this study were to assess i) the effect of hazelnut skin supplementation on lamb meat quality characteristics and plasma and muscle proteomes, and ii) whether analyzing plasma proteome by using a gel-based proteomic approach could effectively offer a more readily available option for determining lamb meat quality. Taken together, the proteomic approach applied to plasma and muscle proteomes, allowed us to reveal the pathways and the potential candidate plasma biomarkers to predict lamb meat production in the pre-slaughter phase.

Early postmortem muscle proteome and metabolome of beef longissimus thoracis muscle classified by pH at 6 hours postmortem

The objective was to identify metabolome and proteome differences at 1 h and 1 d postmortem between longissimus thoracis (LT) muscle classified based on 6 h pH values. Twenty beef LT rib sections were sorted based on 6 h postmortem pH values into low (LpH; pH < 5.55; n = 9) and high (HpH; pH > 5.84; n = 8) pH classifications. Warner-Bratzler shear force (WBSF), desmin degradation, and calpain-1 autolysis were measured. Two-dimensional difference in gel electrophoresis (3-10, 4-7, and 6-9 pH range) and Tandem mass tagging (TMT) protein analyses were employed to determine how the sarcoplasmic protein profile varied across pH classification. Non-targeted metabolomic analyses were conducted on extracts prepared at 1 h and 1 d postmortem. The LpH classification had a lower WBSF value at 1 d postmortem, which was explained by greater calpain-1 autolysis and desmin degradation at 1 d postmortem. Proteome and metabolome analysis revealed a phenotype that promotes more rapid energy metabolism in the LpH group. Proteome and metabolome analyses identified energy production, apoptotic, calcium homeostasis, and proteasome systems influencing pH classifications that could explain the observed pH, proteolysis, and beef tenderness differences. SIGNIFICANCE: This study is the first to identify proteomic and metabolomic variations early (1 h and 1 day) postmortem that are linked to differences in early (6 h) postmortem pH values and to tenderness differences at 1 day postmortem. This study integrates postmortem biochemical features (protein degradation, proteome, and metabolome variations) to postmortem pH decline and eating quality of beef steaks. Potential biomarkers of more rapid postmortem metabolism linked to earlier tenderization in beef are suggested. Identification of these biochemical features will assist in predicting the eating quality of beef products.

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.

Proteomic analyses of mitochondrial damage in postmortem beef muscles

BACKGROUND

The objective of the study was to examine the expression profiles of mitochondrial proteins in at-death and 24 h postmortem (PM) using tandem mass tag (TMT) approach to characterize the mitochondria possible mechanisms that are affiliated with tenderization.

RESULTS

Results showed that the tender meat at 24 h PM emerged with more serious mitochondrial damage. Altogether 456 mitochondrial proteins were identified, including 442 down-regulated and 14 up-regulated proteins. These differentially-expressed proteins were primarily involved in the progress of PM energy metabolism, apoptosis, and the morphological alterations of mitochondrial. Among them, 47 subunits (such as NDUFA2, COX4I1, and ATP5PB) were annotated into the oxidative phosphorylation pathway. VDAC1, VDAC2, and VDAC3 involving in the damage of MPTP, and IMMT, CHCHD3, APOL and APOO modulating the morphology of mitochondria, and DIABLO and AIFM1 released from mitochondria affect caspase's activation. HSPD1 and HSPE1 involved in apoptosis, mitochondrial physiological and morphological alterations.

CONCLUSION

The earlier-mentioned proteins were validated as potential indicators of tenderness regulated by mitochondrial damage. These results highlighted that mitochondrial damage possibly participate in PM tenderization of beef muscles by energy metabolism and cell apoptosis status. © 2022 Society of Chemical Industry.

Production of cultured meat from pig muscle stem cells

Cultured meat is meat for consumption produced in a more sustainable way. It involves cell harvesting and expansion, differentiation into myotubes, construction into muscle fibres and meat structuring. We isolated 5.3 × 104 porcine muscle stem cells from 1 g of neonatal pig muscle tissue. According to calculations, we need to expand muscle stem cells 106-107 times to produce 100 g or 1 kg of cultured meat. However, the cells gradually lost the ability to express stemness and mature muscle cell markers (PAX7, MyHC). To tackle this critical issue and maintain cell function during cell expansion, we found that long-term culture with (100 μM) l-Ascorbic acid 2-phosphate (Asc-2P) accelerated cell proliferation while preserving the muscle cell differentiation. We further optimized a scalable PDMS mold. Porcine muscle stem cells formed structurally-organized myotubes similar to muscle fibres in the mold. Asc-2P enhanced porcine muscle cells grown as 3D tissue networks that can produce a relatively large 3D tissue networks as cultured meat building blocks, which showed improved texture and amino acid content. These results established a realistic workflow for the production of cultured meat that mimics the pork meat structurally and is potentially scalable for industry.

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.

Quality Properties of Dry-Aged Beef (Hanwoo Cattle) Crust on Pork Patties

This study evaluated the effects of crust derived from dry-aged beef (Hanwoo cattle) on the quality of pork patties. Pork patty samples were prepared with different amounts of crust (0—control, 1, 2, and 3%). The protein, fat, and ash contents in the crust samples were significantly higher than those in the control sample (p < 0.05). The CIE b* value of uncooked pork patties with crust added was significantly lower than that of the control patties (p < 0.05). The pH and CIE L* values of uncooked patty batter samples decreased with increasing concentrations of crust (p < 0.05). However, the viscosity increased proportionally with an increase in crust (p < 0.05). Samples containing 3% crust showed significantly higher uncooked and cooked CIE a*, water-holding capacity, cooking yield, and shear force than the control sample (p < 0.05). Moreover, samples containing 2% and 3% crust showed significantly lower diameter and thickness reductions than those of the control sample (p < 0.05). The sensory evaluation conferred by the crust was significantly higher than that of the control sample (p < 0.05). Overall, our results suggest that pork patties supplemented with 3% crust have improved properties.

Proteomic and parallel reaction monitoring approaches to evaluate biomarkers of mutton tenderness

Intensive fattening usually results in the changes of meat quality. Tenderness is a central attribute for mutton sensory qualities and consumers' choice. Here, we reported that intensive fattening mutton was more tender than that of traditionally raised sheep. By proteomic approach, we found 49 differentially expressed proteins in longissimus dorsi muscle. After bioinformatics analysis, 5 cytoskeletal proteins, 3 protein binding proteins and 7 metabolic enzymes were identified as potential biomarkers for mutton tenderness. Finally, we verified the expression of these abundant proteins by parallel reaction monitoring (PRM). Collectively, our results reveal that the mutton of sheep raised by intensive fattening is more tender than that of traditionally raised sheep. Myosin-2, myosin-13, vimentin, carbonic anhydrase, carbonic anhydrase-2, Glutathione S-transferase and Microtubule-associated protein 4 isoform X1 can be candidate biomarkers for mutton tenderness. Our data also indicate a central role of cytoskeletal proteins and metabolic enzymes in determining mutton tenderness.

Early postmortem degradation of actin muscle protein in Algerian Sahraoui dromedaries

The present study aimed to evaluate actin degradation during the early postmortem time in Longissimus Lumborum muscle according to Sahraoui dromedary's age. A sample of eight males, young (2 years old) and adult (8 years old) dromedaries, was used to investigate meat quality traits and actin proteolysis during the conversion of muscle to meat. Results demonstrated higher pH values in young compared to adult with a polyphasic pH drop profile. While, age did not affect drip loss (DL) and the values at 72 h postmortem varied from 5 to 9%. Western blot revealed that actin proteolysis occurred since 1 h postmortem and that it was affected by age and postmortem time. In particular, the 32 and 25 kDa actin fragments could be potential markers of ongoing meat tenderization.

Estimation of the proteome affecting changes in tenderness of yak meat during storage by label-free mass spectrometry

Background

Tenderness is the main quality of meat products. However, the meat tenderness formation is a complex biological process, and pathways and proteins that affect the tenderness of yak meat are unknown.

Methods

Label‐free proteomics method was used to explore the effects of differentially expressed proteins on the tenderness of yak skeletal muscle (tenderloin) during post‐mortem storage (0, 3, and 7 days) at 3 ± 1°C.

Results

The tenderness of yak skeletal muscle improved significantly during storage. A total of 91 differentially expressed proteins of yak skeletal muscle during post‐mortem storage were identified by the following comparisons: day 3 versus 0, day 7 versus 0, and day 7 versus 3. NDUFS6, CYCS, COX6A2, LDB3, HSPB7, TPM4, TAGLN, COL1A1, LUM, MYH11, ACTC1, and MYOZ1 proteins showed a significant difference during yak skeletal muscle post‐mortem storage. Furthermore, bioinformatics analyses revealed that the identified proteins were related to carbon metabolism, citrate cycle, glycolysis, oxidative phosphorylation, and RNA degradation.

Conclusion

The results of the present study could provide proteomic insights into changes in yak skeletal muscle tenderness during storage and may be a valuable resource for future investigations.

Proteomic Technologies and their Application for Ensuring Meat Quality, Safety and Authenticity

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Proteomic tools were extensively used to understand the relationship between muscle proteome and conversion of muscle to meat, post-mortem proteolysis, meat texture, and variation in meat color. Developments in proteomic tools have also resulted in their application for addressing the safety and authenticity issues including meat species identification, detection of animal byproducts, non-meat ingredients and tissues in meat products, traceability, identification of genetically modified ingredients, chemical residues and other harmful substances. Proteomic tools are also being used in some of the potential areas like understanding the effect of animal transportation, stunning, slaughter stress, halal authentication and issues related to animal welfare. Emerging advances in proteomic and peptidomic technologies and their application in traceability, meat microbiology, safety and authentication are taking a major stride as an interesting and complementary alternative to DNA-based methods currently in use. Future research in meat science need to be linked to emerging metabolomic, lipidomic and other omic technologies for ensuring integrated meat quality and safety management. In this paper, a comprehensive overview of the use of proteomics for the assessment of quality and safety in the meat value chain and their potential application is discussed.

Effect of Protein Thermal Denaturation on the Texture Profile Evolution of Beijing Roast Duck

To investigate the mechanism of the texture formed by protein thermal denaturation, the profile and formation of texture and thermal denaturation of protein were evaluated using texture profile analysis (TPA) and transmission electron microscopy (TEM) combined with differential scanning calorimeter (DSC). Results indicated that the surface temperature of Beijing roast duck increased from 23.9 to 174.4 °C, while the center temperature rose from 20.6 to 99.3 °C during roasting. Shear force decreased significantly during the first 20 min, and the texture profile largely changed at 20 and 40 min. Firstly, Band I was broken and twisted, Band A was overstruck, and Z-line was diffused and finally disappeared, resulting in a blurred myofibril structure. The sarcomere considerably contracted within 30 min. Secondly, the main myofibrillar proteins were denatured at 20 and 40 min, respectively. The formation of hydrophobic interactions and the reduction of ionic bonds were observed. Thirdly, roasting induced protein thermal denaturation, which was correlated with interprotein forces, texture profile, and the shear force. Muscle fibers were damaged and shrunken, accompanied by the formation of hydrophobic interactions and the reduction of ionic bonds. The turning points were at 20 and 40 min, and the main proteins were denatured, leading to the formation of tenderness of Beijing roast duck.

Associations of Apoptotic and Anti-Apoptotic Factors with Beef Quality, Histochemical Characteristics, and Palatability of Hanwoo Longissimus thoracis Muscle

This study compared the meat quality, histochemical traits, palatability, and expression levels of apoptotic (cytochrome c and caspases) and anti-apoptotic (small heat shock proteins) factors at 45 min and 24 h post-mortem of Hanwoo Longissimus thoracis muscles in groups categorized by Warner-Bratzler shear force (WBS) values to investigate the association between beef tenderness variation and apoptosis-related molecules. There were no differences in marbling scores, meat quality traits, or histochemical characteristics among the WBS groups (p > 0.05) indicating no significant effect on the tenderness variation in the current study. On the other hand, the low group exhibited higher levels of apoptotic and anti-apoptotic factors (except for αβ-crystallin) at 45 min post-mortem compared to the high WBS group, resulting in higher scores of tenderness attributes (p < 0.05). However, the level of αβ-crystallin at 45 min post-mortem was lower in the low and medium WBS groups compared to the high WBS group (p < 0.0106). At 24 h post-mortem, no significant differences were observed in the expression levels of apoptosis-related factors among the WBS groups (p > 0.05) except for heat shock protein 27 (p < 0.05).

Housekeeping Proteins in Meat Quality Research: Are They Reliable Markers for Internal Controls in Western Blot? A Mini Review

Advancements in technology and analytical methods enable researchers to explore the biochemical events that cause variation in meat quality. Among those, western blot techniques have been successfully used in identifying and quantifying the key proteins that have critical functions in the development of meat quality. Housekeeping proteins, like β-actin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and tubulins are often used as internal controls in western blots to normalize the abundance of the protein of interest. However, there are increasing concerns about using housekeeping proteins for western blot normalization, as these proteins do not demonstrate any loading differences above the relatively small total protein loading amounts of 10μg. In addition, the interaction between these housekeeping proteins and programmed cell death processes highlights the concerns about using the housekeeping protein as the internal control in meat quality research. Moreover, recent proteomic research has indicated that the abundance of some housekeeping proteins, like β-actin, GAPDH, and tubulin, can be altered by preslaughter stress, dietary supplementation, sex, slaughter method, genotype, breed, aging period, muscle type, and muscle portion. Furthermore, these housekeeping proteins could have differential expression in meat with differing color stability, tenderness, and water holding capacity. Therefore, this review aims to examine the realities of using housekeeping proteins as the loading control in meat quality research and introduce some alternative methods that can be used for western blot normalization.

Effects of Neck-Arm Restraint Suspension of Beef Carcasses on Meat Quality and Proteome of Different Muscles During Post-mortem Aging

Beef quality is the first deciding factor for consumers to consider before purchasing. The aim of this study was to evaluate the effects of suspension and aging time on beef quality. We compared the differences in pH, drip loss, cooking loss, color, shear force, myofibril fragmentation index (MFI), and electron microscope of three muscle tissues between Achilles tendon (AT) and neck-arm restraint (NR) suspensions during seven aging periods (days 0, 1, 2, 3, 7, 14, and 21) after slaughter using the carcasses of six Xinjiang brown cattle. We found that NR suspension could significantly increase the water loss rate and MFI, as well as reduce the shear force compared to AT suspension. The muscle fiber structure with NR suspension was more severely damaged. The proteomics of longissimus dorsi was checked for the post-mortem days 1, 7, and 14. We detected 50, 26, and 29 differentially expressed proteins between NR and AT suspension at post-mortem days 1, 7, and 14, respectively. These proteins were involved in metabolic and muscle structure associated pathways and contributed to a comprehensive understanding of suspension-dependent meat quality regulation by proteins in beef cattle. To conclude, NR suspension can accelerate the aging time of beef carcasses, which will reduce the cost of carcass suspension and bring more benefits in the beef industry.

Peptidomic analysis characterising proteolysis in thaw-aging of beef short plate

Recent studies have suggested that thaw-aging can improve sensory attributes of freeze-thawed meat. Acceleration of proteolysis is expected to promote tenderisation and improve taste; however, the details of protein degradation, including substrate proteins and cleavage sites, remain unclear. Here, we report a time course overview of the peptidome of beef short plates during thaw-aging. The accelerated degradation of key proteins for meat tenderisation, such as troponin T and desmin, was confirmed. Additionally, 11 cleavage sites in troponin T related to taste-active peptide generation were identified. Terminome analysis showed that the contribution of each protease varies depending on the substrate proteins and the thaw-aging period. Based on our results; proteases, not only calpains, but also others contributed to the degradation of myofibrillar proteins. The techniques employed indicate that meat proteolysis during thaw-aging is not constant but dynamic.

New Insights on the Impact of Cattle Handling on Post-Mortem Myofibrillar Muscle Proteome and Meat Tenderization

This study investigated the effect of different cattle management strategies at farm (Intensive vs. Extensive) and during transport and lairage (mixing vs. non-mixing with unfamiliar animals) on the myofibrillar subproteome of Longissimus thoracis et lumborum (LTL) muscle of "Asturiana de los Valles" yearling bulls. It further aimed to study the relationships with beef quality traits including pH, color, and tenderness evaluated by Warner-Bratzler shear force (WBSF). Thus, comparative proteomics of the myofibrillar fraction along meat maturation (from 2 h to 14 days post-mortem) and different quality traits were analyzed. A total of 23 protein fragments corresponding to 21 unique proteins showed significant differences among the treatments (p < 0.05) due to any of the factors considered (Farm, Transport and Lairage, and post-mortem time ageing). The proteins belong to several biological pathways including three structural proteins (MYBPC2, TNNT3, and MYL1) and one metabolic enzyme (ALDOA) that were affected by both Farm and Transport/Lairage factors. ACTA1, LDB3, and FHL2 were affected by Farm factors, while TNNI2 and MYLPF (structural proteins), PKM (metabolic enzyme), and HSPB1 (small Heat shock protein) were affected by Transport/Lairage factors. Several correlations were found between the changing proteins (PKM, ALDOA, TNNI2, TNNT3, ACTA1, MYL1, and CRYAB) and color and tenderness beef quality traits, indicating their importance in the determination of meat quality and their possible use as putative biomarkers.

Proteomics discovery of protein biomarkers linked to yak meat tenderness as determined by label-free mass spectrometry

Tenderness is one of the most important qualities in meat. A proteomic approach is a suitable way to ensure meat tenderness. Thirty-six tenderloin samples from yak were classified as exhibiting high (n = 12) or low (n = 12) tenderness and were evaluated using label-free proteomics for the identification of the proteins and pathways most influential in tenderness variability. Between the two groups, proteomic changes were mainly caused by 33 differentially expressed proteins as displayed in reference patterns in heat maps. The expression of ENO2, SUCLG2, ETFDH, PGM1, TNNT3, TNNT1, HSDL2, GPI, ALAD, and COL1A1 proteins was very different between yak meats with high and low tenderness, and therefore, they are candidate biomarkers of yak meat tenderness. Furthermore, bioinformatics analyses revealed that the identified proteins are related to pentose phosphate, glycolysis, the citrate cycle, fatty acid metabolism, and the calcium signaling pathway.

Proteomic analysis to understand the relationship between the sarcoplasmic protein patterns and meat organoleptic characteristics in different horse muscles during aging

The study investigates the changes in meat organoleptic characteristics and sarcoplasmic proteins of 3 horse muscles during aging. Longissimus lumborum (LL), semimembranosus (SM) and semitendinosus (ST) muscles, were removed from 12 Italian Heavy Draft Horse carcasses and aged for 1, 3, 6, 9 and 14 days. The lowest values of hardness and chewiness were found in LL muscle. During aging, a decrease of hardness was observed in ST muscle reaching the lowest value at 14 days. 2DE revealed a decrease of 15 sarcoplasmic protein spots in all muscles. Muscle-differences were found at 14 days. An increase of tropomyosin spots was found in LL muscle while, ST was characterized by a rise of superoxide dismutase, phosphoglucomutase-1 and two isoforms of myoglobin. Principal component analysis applied to color, texture parameters and spots volume differentiated the muscles into three different clusters. Data revealed that myofibrillar, glycolytic and mitochondrial proteins are potential muscle-biomarkers to monitor post-mortem processes and meat quality characteristics in horse meat.

Kohonen Artificial Neural Network and Multivariate Analysis in the Identification of Proteome Changes during Early and Long Aging of Bovine Longissimus dorsi Muscle Using SWATH Mass Spectrometry

To study proteomic changes involved in tenderization of Longissimus dorsi, Charolais heifers and bulls muscles were sampled after early and long aging (12 or 26 days). Sensory evaluation and instrumental tenderness measurement were performed. Proteins were analyzed by gel-free proteomics. By pattern recognition (principal component analysis and Kohonen's self-organizing maps) and classification (partial least squares-discriminant analysis) tools, 58 and 86 dysregulated proteins were detected after 12 and 26 days of aging, respectively. Tenderness was positively correlated mainly with metabolic enzymes (PYGM, PGAM2, TPI1, PGK1, and PFKM) and negatively with keratins. Downregulation in hemoglobin subunits and carbonic anhydrase 3 levels was relevant after 12 days of aging, while mimecan and collagen chains levels were reduced after 26 days of aging. Bioinformatics indicated that aging involves a prevalence of metabolic pathways after late and long periods. These findings provide a deeper understanding of changes involved in aging of beef and indicate a powerful method for future proteomics studies.

Ultrasonication of beef improves calpain-1 autolysis and caspase-3 activity by elevating cytosolic calcium and inducing mitochondrial dysfunction

The objective of this study was to investigate if ultrasonication of bovine longissimus thoracis et lumborum (LTL) steaks increases calpain-1 and caspase-3 activities, and if so, to explore the underlying mechanisms that trigger their activation. Post-rigor bovine LTL steaks were subjected to ultrasonication at 40 kHz and 12 W/cm² for 40 min and subsequently aged for 14 d at 4 °C. Ultrasonication improved beef tenderness (P < 0.05) without negatively impacting pH, color, or cook loss (P > 0.05). Improved tenderness in the ultrasonicated steaks was associated with greater degradation of titin, desmin, troponin-T, and calpastatin and increased calpain-1 autolysis and caspase-3 activity (P < 0.05). In addition, ultrasonicated steaks had greater levels of cytosolic calcium and reactive oxygen species and lower mitochondrial oxygen consumption rate (P < 0.05). These data indicate that improved beef tenderness following ultrasonication is, in part, a function of increased calpain-1 and caspase-3 activities, potentially by elevating cytosolic calcium and inducing mitochondrial dysfunction, respectively.

Redox Biomarker Baseline Levels in Cattle Tissues and Their Relationships with Meat Quality

Cattle breeds or crossbreds with high productivity traits have been developed to meet a growing demand for food. When intensive farming practices are followed, animals face several challenges which can result in poor performance, compromised welfare and the reduced quality of their products. Our study aims to highlight the resting values of the physiological oxidative stress that three cattle breeds exhibit, and their potential relationship with meat quality. For this purpose, we determined the levels of five common redox biomarkers (glutathione (GSH), catalase (CAT), total antioxidant capacity (TAC), thiobarbituric reactive substances (TBARS) and protein carbonyls (CARBS)) in the tissues of three commonly used beef cattle breeds (Charolais (CHA), Limousin (LIM) and Simmental (SIM)) and their association with specific meat quality traits that depend on color, pH and texture. The results revealed that LIM cattle breed animals have elevated intrinsic antioxidant defense systems in comparison to CHA and SIM cattle breed animals. In addition, the meat quality parameters were associated with the redox biomarkers. We propose that the determination of specific antioxidant parameters in the blood might be used as potential biomarkers to predict meat quality. This would allow farmers to nutritionally intervene to improve the quality of their products.

Relationship Between Meat Quality, Carcass Characteristics, and Protein Abundance of HSPβ1, HSPA, and DJ1 in Beef Longissimus thoracis Pre-Rigor or After 14 Days’ Aging

This study evaluated associations of heat shock proteins (HSP) and an oxidative stress protein, protein deglycase (DJ1), with beef quality and tenderness. Samples from the longissimus thoracis (N = 99) were collected pre-rigor (day 0) and after 14-d aging. Warner-Bratzler shear force (WBSF), myofibrillar fragmentation index (MFI), and a trained sensory panel were used to determine meat quality. Protein abundance of DJ1 and 2 HSP—HSPβ1 and HSPA—were assessed. Regression analyses demonstrated that DJ1 abundance after 14 d of aging is a predictor of WBSF (P &lt; 0.001), MFI (P = 0.02), and sensory panel tenderness (P &lt; 0.001). Abundance of HSPβ1 after 14 d of aging is also a predictor of MFI (P = 0.03). Additionally, abundance of both HSPβ1 and DJ1 pre-rigor are predictors of juiciness (P &lt; 0.05). Abundance of HSPβ1 pre-rigor was correlated with WBSF (R = 0.67), sensory panel tenderness (R = −0.44), juiciness (R = −0.30), and umami (R = −0.20). Abundance of DJ1 pre-rigor was also correlated with WBSF (R = 0.72), sensory panel tenderness (R = −0.44), juiciness (R = − 0.24), and umami (R = −0.31). After 14-d aging, HSP β 1 abundance was cor- related with WBSF (R = 0.66), sensory panel tenderness (R = −0.34), juiciness (R = −0.34), umami (R = −0.33), and brown/ roasted (R = −0.30). Abundance of DJ1 after 14-d aging was also correlated with WBSF (R = 0.68), sensory panel tenderness (R = −0.41), juiciness (R = −0.21), and umami (R = −0.28). These results demonstrate that abundance of HSPβ1 and DJ1 both pre-rigor and after 14 d of aging are correlated with meat tenderness and end-product quality as assessed by a trained sensory panel. Regression analyses further reveal that abundance of DJ1 and HSPβ1 after 14 d of aging is causative in development of beef tenderness and juiciness, respectively. Taken together, these results suggest that abundance of DJ1 is a predictor of tenderness, whereas abundance of HSPβ1 is related to meat quality but cannot be used to predict tenderness.

Post mortem changes in M. iliotibialis lateralis muscle protein profile of emu (Dromaius novaehollandiae)

The available literature lacks information on the metabolic processes taking place in emu muscles after the cessation of circulation. Hence, this study was undertaken to examine the physicochemical characteristics (pH, drip loss, WHC, TBARS, L*, a*, b*) with concomitant changes in protein expression patterns (SDS-PAGE) of femoral muscle (M. iliotibialis lateralis) that occur post mortem and during the first days (0 h, 24 h, 48 h) of its maturation in 1- and 3-year-old emus. Our results indicated that the interaction between emus age and storage time had significant impact on meat pH and all color indicators. Furthermore, we detected 24 differentially expressed protein bands, representing 22 different gene products. ClueGO pathways analysis revealed that these proteins were mainly involved in glycolysis/gluconeogenesis pathway, pyruvate metabolism and pyrophosphate hydrolysis-driven proton transmembrane transporter activity. Based on the results obtained it can be assumed that early post-mortem metabolism of emu muscle is predominantly based on the glycolysis as reflected by the relative abundance alterations of the glycogenolytic and glycolytic enzymes. Moreover, the energy supplies provided by ATP and other high-energy substances degradation is higher in the group of older emus. Our findings also highlighted the complexity of the molecular mechanisms underlying the conversion of muscle to meat.

iTRAQ-mediated analysis of the relationship between proteomic changes and yak longissimus lumborum tenderness over the course of postmortem storage

To identify differentially expressed proteins associated with energy metabolism and tenderness during the postmortem aging of yak longissimus lumborum muscle samples, we collected tissue samples from yaks raised at different altitudes. At 12 h post-slaughter, we identified 290 differentially expressed proteins (DEPs) in these samples, whereas 436 such DEPs were detected after 72 h. Identified DEPs were clustered into four main functional categories: cell structural proteins, glycogen metabolic proteins, energy reserve metabolic proteins, and cellular polysaccharide metabolic proteins. Further bioinformatics analysis revealed that these proteins were associated with carbon metabolism, glycolysis, and the biosynthesis of amino acids. Our functional insights regarding these identified proteins contribute to a more detailed molecular understanding of the processes of energy metabolism in yak muscle tissue, and represent a valuable resource for future investigations.

Proteomics analysis as an approach to understand the formation of pale, soft, and exudative (PSE) pork

We investigated ten pale, soft, and exudative (PSE), and ten normal meat samples from pig carcasses. The meat quality at 0, 5, 12, and 24 h post-mortem and the key enzyme activities at 0 and 24 h post-mortem were determined. We selected three PSE and three normal samples for proteomics analysis at 0 h and 24 h post-mortem. No remarkable differences in pyruvate kinase (PK) and lactate dehydrogenase (LDH) activity were observed between samples at 0 h post-mortem; however, creatine kinase (CK) activity was significantly higher in PSE meat. Hexokinase (HK) activity in PSE samples was higher than that in normal samples at 24 h post-mortem. Bioinformatics analysis of the proteome showed that PSE was related to glycolysis, TCA cycle, oxidative phosphorylation, muscle tissue structure, signal transduction, and molecular chaperones. This research found that proteins such as troponin T slow skeletal muscle isoform X, GADPH, L-lactate dehydrogenase A chain, and gamma-enolase isoform X1 might be responsible for PSE.

Proteomic pipeline for biomarker hunting of defective bovine meat assisted by liquid chromatography-mass spectrometry analysis and chemometrics

A wide variety of factors prior to slaughter may affect the stress status of beef cattle, giving rise to well-known 'dark-cutting' defective meats characterised by a high ultimate pH (pHu). To understand the underlying mechanisms of pHu fluctuations in beef cattle there was studied the proteome changes caused by pre-slaughter stress through a gel-free proteomic approach. Comparative peptidomic analysis was carried out on 12 loin samples at 24 h post-mortem from Longissimus thoracis et lumborum bovine muscle of crossbred animals, previously sorted into two different groups according to their pHu values: normal (pHu < 6.0) and high (pHu ≥ 6.0). Tryptic peptides from direct protein extracts were approached by combining untargeted (intact mass, MS¹) and targeted (Selected Reaction Monitoring, SRM) quantitative LC-MS assays followed by chemometric analysis. Seventeen peptide biomarkers belonging to 10 different proteins appropriately discriminated sample groups assayed. Results may promote the use of this simple and effective methodology towards the creation of new insights in meat quality research. SIGNIFICANCE: The significance of this study was the optimization of an affordable straightforward gel-free proteomic approach addressing the differentiation of the muscle sub-proteome of normal and high pHu meat samples. This strategy allowed the study of tryptic peptides from direct meat protein extracts by combining untargeted MS¹ and targeted SRM quantitative assays performed by conventional LC-MS detection. Affordability, simplicity and robustness of this methodology can facilitate its readily implementation in routine protocols for quality assessment of meat.

Physicochemical and microbial characteristics of longissimus lumborum and biceps femoris muscles in Korean native black goat with wet-aging time

This study examined the effects of different wet-aging times on the physicochemical characteristics and microbial profile of longissimus lumborum (LL) and biceps femoris (BF) muscles from Korean native black goat (KNBG) meat. The water holding capacity (WHC), pH, cooking loss, shear force, meat color, free amino acid, total bacteria, and coliform count of KNGB meat were analyzed at 0, 5, 10, and 15 days of wet-aging at 4°C under vacuum packaging. The results showed that different wet-aging times led to significant pH variations between the muscles throughout the aging period. The wet-aging time did not affect the WHC and cooking loss in meat from the LL muscle. In the BF muscle, however, meat wet-aged for five days had a significantly higher WHC and less cooking loss than meat aged for 0, 10, and 15 days. The meat from the LL muscle wet-aged for five days produced tenderer meat (low shear force value) than the unaged meat (p < 0.05). Moreover, the color was similar in the LL muscle regardless of the number of aging days. In the BF muscle, the redness (a*) was higher in the meat wet-aged for 15 days compared to that aged for 0, 5, and 10 days (p < 0.05). Regardless of the muscles, an increase in wet-aging time led to an increase in the total free amino acids contents in both muscles (p < 0.05). On the other hand, the tasty/bitter amino acid ratio was significantly higher for five days of wet-aged meat than 10 and 15 days of aging from the BF muscle. In addition, regardless of the muscles, the total bacteria and coliform counts were significantly lower for five days of wet-aged meat than 10 and 15 days of aging (p < 0.05). Therefore, chevon wet-aged for five days is an optimal aging period under vacuum packaging that fortifies meat quality with a minimal microbial negative defect.

The Extent and Rate of the Appearance of the Major 110 and 30 kDa Proteolytic Fragments during Post-Mortem Aging of Beef Depend on the Glycolysing Rate of the Muscle and Aging Time: An LC-MS/MS Approach to Decipher Their Proteome and Associated Pathways

Post-mortem (p-m) muscle undergoes a myriad of complex physical and biochemical changes prior to its conversion to meat, which are influential on proteolysis and hence tenderization. A more in-depth understanding of the mechanisms underpinning these dynamics is a key to consistently providing tender beef. Using an LC-MS/MS approach, with state-of-art mass spectrometry Q Exactive HF-X, the proteome and associated pathways contributing to the appearance of the proteolytic breakdown products appearing over 14 days p-m, at two important molecular weights (110 and 30 kDa) on 1D SDS-PAGE gels, have been investigated in beef longissimus thoracis et lumborum muscles exhibiting four rates of pH decline differentiated on the basis of time at pH 6 (fast glycolysing, <3 h; medium, 3-5 h; slow, 5-8 h; and very slow, 8+ h). Both 110 and 30 kDa bands appeared during aging and increased in intensity as a function of p-m time in a pH decline-dependent manner. The 110 kDa band appeared as early as 3 h p-m and displayed an incremental increase in all groups through to 14 days p-m. From 2 days p-m, this increase in abundance during aging was significantly (P < 0.001) influenced by the glycolytic rate: fast > or = medium > slow > very slow. The day 2 p-m appearance of the 30 kDa band was most evident for the fast glycolysing muscle with little or no evidence of appearance in slow and very slow. For days 7 and 14 p-m, the strength of appearance was dependent on glycolysing groups fast > medium > or = slow > very slow. LC-MS/MS analysis yielded a total of 22 unique proteins for the 110 kDa fragment and 13 for the 30 kDa, with 4 common proteins related to both the actin and fibrinogen complex. The Gene Ontology analysis revealed that a myriad of biological pathways are influential with many related to proteins involved primarily in muscle contraction and structure. Other pathways of interest include energy metabolism, apoptotic mitochondrial changes, calcium and ion transport, and so on. Interestingly, most of the proteins composing the fragments were so far identified as biomarkers of beef tenderness and other quality traits.

Physicochemical properties of crust derived from dry-aged Holstein and Hanwoo loin

This study evaluated the quality characteristics of crust derived from dry-aged Holstein and Hanwoo loins and their effects on food as additives. With respect to physicochemical properties, we examined the proximate composition, pH value, salinity, color, water and fat absorption, emulsifying capacity, and swelling yield. The protein and ash contents in the Holstein crust were significantly higher than those in the Hanwoo crust (p < 0.0001). The fat content in the Hanwoo crust was significantly higher than that in the Holstein crust (p < 0.01). The salinity, lightness, and yellowness of the Hanwoo crust were significantly lower than those of the Holstein crust (p < 0.001). Furthermore, the pH value and emulsifying capacity of the Hanwoo crust were significantly higher than those of the Holstein crust (p < 0.001). The fat absorption of the Holstein crust was significantly higher than that of the Hanwoo crust (p < 0.001). The swelling yield of the Holstein crust was significantly higher than that of the Hanwoo crust at pH 3 and 4 (p < 0.001), whereas the swelling yield of the Hanwoo crust was significantly higher than that of the Holstein crust at pH 7 (p < 0.001). Principal component analysis of dry-aged Hanwoo, Holstein, and non-aged Holstein showed different flavor patterns for each sample. Finally, the results showed that the crusts derived from dry-aged Hanwoo and Holstein loins were suitable flavor enhancers.

Molecular signatures of beef tenderness: Underlying mechanisms based on integromics of protein biomarkers from multi-platform proteomics studies

Over the last two decades, proteomics have been employed to decipher the underlying factors contributing to variation in the quality of muscle foods, including beef tenderness. One such approach is the application of high-throughput protein analytical platforms in the identification of meat quality biomarkers. To broaden our understanding about the biological mechanisms underpinning meat tenderization across a large number of studies, an integromics study was performed to review the current status of protein biomarker discovery targeting beef tenderness. This meta-analysis is the first to gather and propose a comprehensive list of 124 putative protein biomarkers derived from 28 independent proteomics-based experiments, from which 33 robust candidates were identified worthy of evaluation using targeted or untargeted data-independent acquisition proteomic methods. We further provide an overview of the interconnectedness of the main biological pathways impacting tenderness determination after multistep analyses including Gene Ontology annotations, pathway and process enrichment and literature mining, and specifically discuss the major proteins and pathways most often reported in proteomics research.