Understanding Early Post-Mortem Biochemical Processes Underlying Meat Color and pH Decline in the Longissimus thoracis Muscle of Young Blond d'Aquitaine Bulls Using Protein Biomarkers

In-depth exploration of the high and normal pH beef proteome: First insights emphasizing the dynamic protein changes in Longissimus thoracis muscle from pasture-finished Nellore bulls over different postmortem times

This study aimed to evaluate for the first time the temporal dynamic changes in early postmortem proteome of normal and high ultimate pH (pHu) beef samples from the same cattle using a shotgun proteomics approach. Ten selected carcasses classified as normal (pHu < 5.8; n = 5) or high (pHu ≥ 6.2; n = 5) pHu beef from pasture-finished Nellore (Bos taurus indicus) bulls were sampled from Longissimus thoracis muscle at 30 min, 9 h and 44 h postmortem for proteome comparison. The temporal proteomics profiling quantified 863 proteins, from which 251 were differentially abundant (DAPs) between high and normal pHu at 30 min (n = 33), 9 h (n = 181) and 44 h (n = 37). Among the myriad interconnected pathways regulating pH decline during postmortem metabolism, this study revealed the pivotal role of energy metabolism, cellular response to stress, oxidoreductase activity and muscle system process pathways throughout the early postmortem. Twenty-three proteins overlap among postmortem times and may be suggested as candidate biomarkers to the dark-cutting condition development. The study further evidenced for the first time the central role of ribosomal proteins and histones in the first minutes after animal bleeding. Moreover, this study revealed the disparity in the mechanisms underpinning the development of dark-cutting beef condition among postmortem times, emphasizing multiple dynamic changes in the muscle proteome. Therefore, this study revealed important insights regarding the temporal dynamic changes that occur in early postmortem of high and normal muscle pHu beef, proposing specific pathways to determine the biological mechanisms behind dark-cutting determination.

Stunning methods before slaughter induce oxidation changes of large yellow croaker during cold storage: the role of mitochondria and underlying mechanisms

BACKGROUND

Improper stunning methods before slaughter could cause fish to deteriorate more quickly during cold storage. However, it is unclear how stunning methods affect the mitochondrial structure and the role of mitochondria in oxidation in muscle-based food.

RESULTS

This study explored the potential mechanism of oxidation induced by different stunning methods (hit on the head, T1 ; gill cut, T2 ; immersion in ice/water slurry, T3 ; CO2 asphyxiated, T4 ; 40% CO2  + 30% N2  + 30% O2 , T5 ) in large yellow croaker during cold storage. The results showed that T4 samples had the minimum stress response and the mitochondrial membrane potential and permeability were less damaged. Besides, the mitochondrial functional structure and peroxisome of T4 samples were less damaged compared with other samples, which was reflected in higher total superoxide dismutase, catalase and glutathione peroxidase activities. In terms of oxidation indices, the T4 samples showed higher pH values and iron myoglobin contents and lower total volatile basic nitrogen and thiobarbituric acid reactive substances after 168 h cold storage, indicating that the T4 samples significantly maintained oxidative stability of large yellow croaker.

CONCLUSION

The CO2 asphyxiation had the least oxidative damage to large yellow croaker during cold storage, possibly because it had the least effect on mitochondrial structure, reactive oxygen species and antioxidant enzyme activity. © 2023 Society of Chemical Industry.

Tryptophan improves antioxidant capability and meat quality by reducing responses to stress in nervous Hu sheep

In sheep, the effect of tryptophan (Trp) on behavioural traits that are associated with temperament and any effects on production traits is unknown. The hypothesis of this study is that the supplementation of Trp would improve temperament by enhancing serotonin production, which is beneficial to meat production subsequently in sheep. Twelve ewes that had the lowest and 12 ewes that had the highest behavioural responses to human contact were selected into the calm and the nervous groups respectively. Then, the ewes from each group were equally assigned into two treatments that were treated with the basal diet and the diet with extra 90 mg/kg/d Trp for 30 d. The temperament traits, the growth performance, the biochemicals that are related to health the slaughter performance and meat quality were measured at the end of feeding experiment. The findings in this study suggested the Hu sheep with calm temperament would experience less stress during production, resulting in less oxidative stress, better growth performance, slaughter traits and carcass traits, compared to the nervous sheep. Meanwhile, the dietary supplementation of Trp reduced stress responses by enhancing production of 5-HT in sheep from the nervous group which is beneficial to improve the production traits that mentioned above.

In-depth characterization of the sarcoplasmic muscle proteome changes in lambs fed with hazelnut skin by-products: Relationships with meat color

This study investigated the effect of agro-industrial hazelnut skin by-products supplementation on lamb meat color variation and the changes in the sarcoplasmic muscle proteome during post-mortem storage (0, 4 and 7 days). Gel-based proteomics and bioinformatics approaches were applied to better understand the potential role of feeding strategies in modulating the mechanisms underpinning meat discoloration and post-mortem changes during storage. Therefore, twenty-two Valle del Belice male lambs were randomly assigned to two dietary treatments: control (C), lambs fed with maize-barley diet, and hazelnut skin (H), lambs fed hazelnut skin by-product as maize partial replacer in the concentrate diet. Hazelnut dietary treatment led to better lamb meat color stability as evidenced by the lowest decrease in redness and saturation index values. Proteomics and bioinformatics results revealed changes in the abundance of 41 proteoforms, which were mainly involved in glycolytic processes, responses to oxidative stress, and immune and endocrine system. The proteins allowed revealing interconnected pathways to be behind meat color variation as a consequence of using hazelnut skin by-products to sustainable feed lamb. The proteins can be used as potential predictors of lamb meat color variation. Accordingly, the regression equations developed in this paper revealed triosephosphate isomerase (TPI1) as a reliable candidate biomarker of color stability in lamb meat. SIGNIFICANCE: The use of agro-industrial by-products in animal feeding can be a potential sustainable strategy to reduce the environmental impacts of the food production chain and consequently improve animal welfare and product quality. The inclusion of hazelnut skin by-products in the animal's diet, due to the high concentration of polyphenols, represents an effective strategy to improve the oxidative stability of meat, with significant implications on color. The use of proteomics combined with bioinformatics on the sarcoplasmic proteome is a powerful approach to decipher the underlying mechanism. Accordingly, this approach allowed in this trial a deeper understanding of the molecular mechanisms involved in the post-mortem processes through the discovery of several biological pathways linked with lamb meat color variation. Glycolysis, followed by responses to oxidative stress, and other proteins involved in the immune and endocrine system were found as the major interconnected pathways that could act as potential predictors of lamb meat color stability. Candidate proteins biomarkers were further revealed in this study to be related with multiple meat color traits.

Proteomics and metabolomics profiling of meat exudate to determine the impact of postmortem aging on oxidative stability of beef muscles

The objective of this study was to characterize the major proteomes and metabolites in beef exudate and determine their relationship to color and oxidative quality of beef muscles. Beef loin (LD) and tenderloin (PM) muscles were cut into sections, individually vacuum-packaged, and aged for 9, 16 and 23 days at 2 °C. Following aging, beef exudates were collected and analyzed for both proteomics and metabolomics profiles. Proteome analysis indicated clustering by muscle types, while metabolomics profiling further clustered the samples based on the aging periods. The PM exudate had a greater concentration of oxidative enzymes, while the LD exudate contained more glycolytic enzymes. Greater lipid, nucleotide, carnitine and glucoside metabolites were observed in LD and 23d exudates. HSP70 and laminin proteins, together with glucosides metabolites, were correlated to muscle oxidative stability. The results indicated that meat exudate could be a viable analytical matrix to determine changes in quality attributes of meat with aging.

Towards the discovery of goat meat quality biomarkers using label-free proteomics

This study aimed to identify for the first time protein biomarkers of meat quality traits from Longissimus thoracis (LT) muscle of goats (Capra hircus). Male goats of similar age and weight reared under extensive rearing conditions were used to relate the LT muscle proteome with multiple meat quality traits. The early post-mortem muscle proteome analyzed using label-free proteomics was compared among three texture clusters built using hierarchical clustering analysis. Twenty-five proteins were differentially abundant and their mining using bioinformatics revealed three major biological pathways to be involved: 10 muscle structure proteins (MYL1, MYL4, MYLPF, MYL6B, MYH1, MYH2, ACTA1, ACTBL2, FHL1 and MYOZ1); 6 energy metabolism proteins (ALDOA, PGAM2, ATP5F1A, GAPDH, PGM1 and ATP5IF1), and two heat shock proteins: HSPB1 (small) and HSPA8 (large). Seven other miscellaneous proteins belonging to pathways such as regulation, proteolysis, apoptosis, transport and binding, tRNA processing or calmodulin-binding were further identified to play a role in the variability of goat meat quality. The differentially abundant proteins were correlated with the goat meat quality traits in addition to multivariate regression models built to propose the first regression equations of each quality trait. This study is the first to highlight in a multi-trait quality comparison the early post-mortem changes in the goat LT muscle proteome. It also evidenced the mechanisms underpinning the development of several quality traits of interest in goat meat production along the major biochemical pathways at interplay. SIGNIFICANCE: The discovery of protein biomarkers in the field of meat research is an emerging topic. In the case of goat meat quality, very few studies using proteomics have been conducted with the aim of proposing biomarkers. Therefore, this study is the first to quest for biomarkers of goat meat quality using label-free shotgun proteomics with a focus on multiple quality traits. We identified the molecular signatures underlying goat meat texture variation, which were found to belong to muscle structure and related proteins, energy metabolism and heat shock proteins along with other proteins involved in regulation, proteolysis, apoptosis, transport and binding, tRNA processing or calmodulin-binding. We further evaluated the potential of the candidate biomarkers to explain meat quality using the differentially abundant proteins by means of correlation and regression analyses. The results allowed the explanation of the variation in multiple traits such as pH, color, water-holding capacity, drip and cook losses traits and texture.

Post-mortem muscle proteome of crossbred bulls and steers: Relationships with carcass and meat quality

This study investigated the skeletal muscle proteome of crossbred bulls and steers with the aim of explaining the differences in carcass and meat quality traits. Therefore, 640 post-weaning Angus-Nellore calves were fed a high-energy diet for a period of 180 days. In the feedlot trial, comparisons of steers (n = 320) and bulls (n = 320) showed lower (P < 0.01) average daily gain (1.38 vs. 1.60 ± 0.05 kg/d), final body weight (547.4 vs. 585.1 ± 9.3 kg), which resulted in lower hot carcass weight (298.4 vs. 333.7 ± 7.7 kg) and ribeye area (68.6 vs. 81.0 ± 2.56 cm²). Steers had higher (P < 0.01) carcass fatness, meat color parameters (L*, a*, b*, chroma (C*), hue (h°)) and lower ultimate pH. Moreover, lower (P < 0.01) Warner-Bratzler shear force (WBSF) were observed in steers compared to bulls (WBSF = 3.68 vs. 4.97 ± 0.08 kg; and 3.19 vs. 4.08 ± 0.08 kg). The proteomic approach using two-dimensional electrophoresis, mass spectrometry and bioinformatics procedures revealed several differentially expressed proteins between steers and bulls (P < 0.05). Interconnected pathways and substantial changes were revealed in biological processes, molecular functions, and cellular components between the post-mortem muscle proteomes of the compared animals. Steers had increased (P < 0.05) abundance of proteins related to energy metabolism (CKM, ALDOA, and GAPDH), and bulls had greater abundance of proteins associated with catabolic (glycolysis) processes (PGM1); oxidative stress (HSP60, HSPA8 and GSTP1); and muscle structure and contraction (TNNI2 and TNNT3). The better carcass (fatness and marbling degree) and meat quality traits (tenderness and color parameters) of steers were associated with higher abundance of key proteins of energy metabolism and lower abundance of enzymes related to catabolic processes, oxidative stress, and proteins of muscle contraction SIGNIFICANCE: Sexual condition of cattle is known to be an important factor affecting animal performances and growth as well as the carcass and meat quality traits. The investigation of skeletal muscle proteome help a better understanding of the origin of the differences in quality traits between bulls and steers. The inferior meat quality of bulls was found to be due to the greater expression of proteins associated with primary and catabolic processes, oxidative stress, and muscle contraction. Steers had greater expression of proteins, from which several are known biomarkers of beef quality (mainly tenderness).

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.

Improving animal welfare status and meat quality through assessment of stress biomarkers: A critical review

Stress induces various physiological and biochemical alterations in the animal body, which are used to assess the stress status of animals. Blood profiles, serum hormones, enzymes, and physiological conditions such as body temperature, heart, and breathing rate of animals are the most commonly used stress biomarkers in the livestock sector. Previous exposure, genetics, stress adaptation, intensity, duration, and rearing practices result in wide intra- and inter-animal variations in the expression of various stress biomarkers. The use of meat proteomics by adequately analyzing the expression of various muscle proteins such as heat shock proteins (HSPs), acute phase proteins (APPs), texture, and tenderness biomarkers help predict meat quality and stress in animals before slaughter. Thus, there is a need to identify non-invasive, rapid, and accurate stress biomarkers that can objectively assess stress in animals. The present manuscript critically reviews various aspects of stress biomarkers in animals and their application in mitigating preslaughter stress in meat production.

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.

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.

Exploratory lipidome and metabolome profiling contributes to understanding differences in high and normal ultimate pH beef

The aim of this work was to compare the lipidome and metabolome profiling in the Longissimus thoracis muscle early and late postmortem from high and normal ultimate pH (pHu) beef. Lipid profiling discriminated between high and normal pHu beef based on fatty acid metabolism and mitochondrial beta-oxidation of long chain saturated fatty acids at 30 min postmortem, and phospholipid biosynthesis at 44 h postmortem. Metabolite profiling also discriminated between high and normal pHu beef, mainly through glutathione, purine, arginine and proline, and glycine, serine and threonine metabolisms at 30 min postmortem, and glycolysis, TCA cycle, glutathione, tyrosine, and pyruvate metabolisms at 44 h postmortem. Lipid and metabolite profiles showed reduced glycolysis and increased use of alternative energy metabolic processes that were central to differentiating high and normal pHu beef. Phospholipid biosynthesis modification suggested high pHu beef experienced greater oxidative stress.

Electrospinning as a Promising Process to Preserve the Quality and Safety of Meat and Meat Products

Fresh and processed meat products are staple foods worldwide. However, these products are considered perishable foods and their deterioration depends partly on the inner and external properties of meat. Beyond conventional meat preservation approaches, electrospinning has emerged as a novel effective alternative to develop active and intelligent packaging. Thus, this review aims to discuss the advantages and shortcomings of electrospinning application for quality and safety preservation of meat and processed meat products. Electrospun fibres are very versatile, and their features can be modulated to deliver functional properties such as antioxidant and antimicrobial effects resulting in shelf-life extension and in some cases product quality improvement. Compared to conventional processes, electrospun fibres provide advantages such as casting and coating in the fabrication of active systems, indicators, and sensors. The approaches for improving, stabilizing, and controlling the release of active compounds and highly sensitive, rapid, and reliable responsiveness, under changes in real-time are still challenging for innovative packaging development. Despite their advantages, the active and intelligent electrospun fibres for meat packaging are still restricted to research and not yet widely used for commercial products. Industrial validation of lab-scale achievements of electrospinning might boost their commercialisation. Safety must be addressed by evaluating the impact of electrospun fibres migration from package to foods on human health. This information will contribute into filling knowledge gaps and sustain clear regulations.

Are muscle fiber types different between normal and dark-cutting beef?

Muscle fiber (MF) characteristics of Longissimus thoracis (LT) muscles from heifer (n = 11) and steer (n = 12) carcasses graded Canada AA (AA, normal, n = 4/sex) or dark-cutting (Canada B4) were examined and related to beef quality. Atypical (AB4, pH < 5.9, n = 4/sex) and typical (TB4, pH > 5.9, n = 3 and 4 for heifers and steers, respectively) dark-cutting carcasses were represented. Muscle fiber type proportions did not differ between AA, AB4 and TB4 muscles, although type I and IIB muscle fiber diameters were greater in TB4 than in AA LT. That AB4 muscle fiber proportions were not different from AA and TB4 muscles suggests that the increased MF diameter of TB4 muscle was due to water retained by muscle proteins at high ultimate pH, as evidenced by decreased cooking loss. Dark-cutting was therefore unrelated to muscle fiber proportions, and increased Type I and IIB diameters in dark cutting LT were likely driven by elevated intramuscular ultimate pH.

Proteomic Changes in Sarcoplasmic and Myofibrillar Proteins Associated with Color Stability of Ovine Muscle during Post-Mortem Storage

The objective of this study was to investigate the proteomic characteristics for the sarcoplasmic and myofibrillar proteomes of M. longissimus lumborum (LL) and M. psoasmajor (PM) from Small-tailed Han Sheep. During post-mortem storage periods (1, 3, and 5 days), proteome analysis was applied to elucidate sarcoplasmic and myofibrillar protein changes in skeletal muscles with different color stability. Proteomic results revealed that the identified differentially abundant proteins were glycolytic enzymes, energy metabolism enzymes, chaperone proteins, and structural proteins. Through Pearson’s correlation analysis, a few of those identified proteins (Pyruvate kinase, Adenylate kinase isoenzyme 1, Creatine kinase M-type, and Carbonic anhydrase 3) were closely correlated to representative meat color parameters. Besides, bioinformatics analysis of differentially abundant proteins revealed that the proteins mainly participated in glycolysis and energy metabolism pathways. Some of these proteins may have the potential probability to be predictors of meat discoloration during post-mortem storage. Within the insight of proteomics, these results accumulated some basic theoretical understanding of the molecular mechanisms of meat discoloration.

Protein Biomarkers of Bovine Defective Meats at a Glance: Gel-Free Hybrid Quadrupole-Orbitrap Analysis for Rapid Screening

An understanding of biological mechanisms that could be involved in the stress response of animal cattle prior to slaughter is critical to create effective strategies aiming at the production of high-quality meat. The sarcoplasmic proteome of directly extracted samples from normal and high ultimate pH (pHu) meat groups was studied through a straightforward gel-free strategy supported by liquid chromatography hybrid quadrupole-Orbitrap high-resolution mass spectrometry (LC-HRMS) analysis. A stepped proteomic pipeline combining rapid biomarker hunting supported by qualitative protein Mascot scores followed by targeted label-free peptide quantification revealed 26 descriptors that characterized meat groups assayed. The functional study of the proposed biomarkers suggested their relevant role in metabolic, chaperone/stress-related, muscle contractility/fiber organization, and transport activities. The efficiency, flexibility, rapidity, and easiness of the methodology proposed can positively contribute to the creation of innovative proteomic alternatives addressing meat quality assessment.

Dark-cutting beef: A brief review and an integromics meta-analysis at the proteome level to decipher the underlying pathways

Comprehensive characterization of the post-mortem muscle proteome defines a fundamental goal in meat proteomics. During the last decade, proteomics tools have been applied in the field of foodomics to help decipher factors underpinning meat quality variations and to enlighten us, through data-driven methods, on the underlying mechanisms leading to meat quality defects such as dark-cutting meat known also as dark, firm and dry (DFD) meat. In cattle, several proteomics studies have focused on the extent to which changes in the post-mortem muscle proteome relate to dark-cutting beef development. The present data-mining study firstly reviews proteomics studies which investigated dark-cutting beef, and secondly, gathers the protein biomarkers that differ between dark-cutting versus beef with normal-pH in a unique repertoire. A list of 130 proteins from eight eligible studies was curated and mined through bioinformatics for Gene Ontology annotations, molecular pathways enrichments, secretome analysis and biological pathways comparisons to normal beef color from a previous meta-analysis. The major biological pathways underpinning dark-cutting beef at the proteome level have been described and deeply discussed in this integromics study.

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.

Understanding the Determination of Meat Quality Using Biochemical Characteristics of the Muscle: Stress at Slaughter and Other Missing Keys

Despite increasingly detailed knowledge of the biochemical processes involved in the determination of meat quality traits, robust models, using biochemical characteristics of the muscle to predict future meat quality, lack. The neglecting of various aspects of the model paradigm may explain this. First, preslaughter stress has a major impact on meat quality and varies according to slaughter context and individuals. Yet, it is rarely taken into account in meat quality models. Second, phenotypic similarity does not imply similarity in the underlying biological causes, and several models may be needed to explain a given phenotype. Finally, the implications of the complexity of biological systems are discussed: a homeostatic equilibrium can be reached in countless ways, involving thousands of interacting processes and molecules at different levels of the organism, changing over time and differing between animals. Consequently, even a robust model may explain a significant part, but not all of the variability between individuals.

Insights on meat quality from combining traditional studies and proteomics

Following a century of major discoveries on the mechanisms determining meat colour and tenderness using traditional scientific methods, further research into complex and interactive factors contributing to variations in meat quality is increasingly being based on data-driven "omics" approaches such as proteomics. Using two recent meta-analyses of proteomics studies on beef colour and tenderness, this review examines how knowledge of the mechanisms and factors underlying variations in these meat qualities can be both confirmed and extended by data-driven approaches. While proteomics seems to overlook some sources of variations in beef toughness, it highlights the role of post-mortem energy metabolism in setting the conditions for development of meat colour and tenderness, and also points to the complex interplay of energy metabolism, calcium regulation and mitochondrial metabolism. In using proteomics as a future tool for explaining variations in meat quality, the need for confirmation by further hypothesis-driven experimental studies of post-hoc explanations of why certain proteins are biomarkers of beef quality in data-driven studies is emphasised.

Biomolecular Interactions Governing Fresh Meat Color in Post-mortem Skeletal Muscle: A Review

Appearance is an important sensory property that significantly influences consumers' perceptions of fresh meat quality. Failure to meet consumer expectations can lead to rejection of meat products, concomitant loss in value, and potential production of organic waste. Immediately after animal harvest, skeletal muscle metabolism changes from aerobic to anaerobic. However, anoxic post-mortem muscle is biochemically active, and biomolecular interaction between myoglobin, mitochondria, metabolites, and lipid oxidation determines meat color. This review examines how metabolites and mitochondrial activity can influence myoglobin oxygenation and metmyoglobin reducing activity. Further, the review highlights recent research that has examined myoglobin redox dynamics, sarcoplasmic metabolite changes, and/or post-mortem biochemistry.

Strategies to limit meat wastage: Focus on meat discoloration

Limiting meat waste is a significant factor that can help meet future needs to provide high-quality animal protein while maximizing the utilization of natural resources. Fresh meat waste occurs during production, processing, distribution, and marketing to various points of consumption. Consumers' expectation for muscle food quality is often associated with its appearance, and a bright-red color of red meat is an indicator of freshness and wholesomeness. Meat discoloration is a natural process resulting from interactions between the physical structure of meat and the oxidation of the ferrous forms of myoglobin. Understanding the biochemical processes that influence discoloration such as oxygen consumption, metmyoglobin reducing activity, lipid oxidation, and microbial growth help to develop innovative strategies to limit meat waste. The focus of this chapter is to discuss the factors involved in meat discoloration and any other color deviations that may lead to discounted pricing and/or meat loss. The impact of meat waste, economic loss, the role of packaging, and the application of high-throughput techniques to understand the biochemical basis of meat discoloration are also discussed.

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.

Protein Array-Based Approach to Evaluate Biomarkers of Beef Tenderness and Marbling in Cows: Understanding of the Underlying Mechanisms and Prediction

This study evaluated the potential of a panel of 20 protein biomarkers, quantified by Reverse Phase Protein Array (RPPA), to explain and predict two important meat quality traits, these being beef tenderness assessed by Warner-Bratzler shear force (WBSF) and the intramuscular fat (IMF) content (also termed marbling), in a large database of 188 Protected Designation of Origin (PDO) Maine-Anjou cows. Thus, the main objective was to move forward in the progression of biomarker-discovery for beef qualities by evaluating, at the same time for the two quality traits, a list of candidate proteins so far identified by proteomics and belonging to five interconnected biological pathways: (i) energy metabolic enzymes, (ii) heat shock proteins (HSPs), (iii) oxidative stress, (iv) structural proteins and (v) cell death and protein binding. Therefore, three statistical approaches were applied, these being Pearson correlations, unsupervised learning for the clustering of WBSF and IMF into quality classes, and Partial Least Squares regressions (PLS-R) to relate the phenotypes with the 20 biomarkers. Irrespective of the statistical method and quality trait, seven biomarkers were related with both WBSF and IMF, including three small HSPs (CRYAB, HSP20 and HSP27), two metabolic enzymes from the oxidative pathway (MDH1: Malate dehydrogenase and ALDH1A1: Retinal dehydrogenase 1), the structural protein MYH1 (Myosin heavy chain-IIx) and the multifunctional protein FHL1 (four and a half LIM domains 1). Further, three more proteins were retained for tenderness whatever the statistical method, among which two were structural proteins (MYL1: Myosin light chain 1/3 and TNNT1: Troponin T, slow skeletal muscle) and one was glycolytic enzyme (ENO3: β-enolase 3). For IMF, two proteins were, in this trial, specific for marbling whatever the statistical method: TRIM72 (Tripartite motif protein 72, negative) and PRDX6 (Peroxiredoxin 6, positive). From the 20 proteins, this trial allowed us to qualify 10 and 9 proteins respectively as strongly related with beef tenderness and marbling in PDO Maine-Anjou cows.

Research in Beef Tenderness and Palatability in the Era of Big Data

For decades, research has focused on predicting beef palatability using muscle biochemical traits, and various biomarkers. In these approaches, a precise definition of the variable to predict (tenderness assessed by panelists, untrained consumers, or shear force), and repeatability of the measurements are crucial for creating significant data resources for the derivation of robust predictive models, and rigorous validation testing. This “big data” approach also requires careful definition of traits and transparent principles for data sharing and management. As in other fields, meat science researchers should improve the Findability, Accessibility, Interoperability, and Reuse of data (known as the FAIR principles). Furthermore, with the rapid evolution of new measurement technologies, the traits that they measure must be consistently described, enhancing our ability to integrate these new measurements into existing description systems. For beef, strategic choices have been made in order to consider real consumers’ expectations, not well estimated correctly by lab approaches. This strategy has been successfully developed in Australia, which set up the “Meat Standards Australia” grading scheme, now partly adopted by the beef industry. The ambitions of the International Meat Research 3G Foundation is to develop beef ontology, to set up an international database with a huge number of consumers’ scores related to beef palatability and collected according to standard protocols. The foundation also aims to support the beef industry by offering an international predictive model of beef palatability, flexible enough to take into account any local livestock characteristics or regional consumer specificity. This approach is supported by the United Nations Economic Commission for Europe (UNECE), which is promoting development of regulations and norms, technical cooperation and exchange of best expertise and practices. This will substantially improve the transparency of data flow and price signaling between all participants of the value chain, from beef producers through to consumers at retail.

Recent Updates in Meat Color Research: Integrating Traditional and High-Throughput Approaches

Deviation from a bright cherry-red color of fresh meat results in less consumer acceptance and either discounted or discarded products in the value chain. Tissue homeostasis changes immediately after exsanguination, leading to acidification of muscle. Any alteration in pH drop can influence both muscle structure and enzymatic activity related to oxygen consumption and the redox state of myoglobin. This review focuses on both fundamental and applied approaches to under-stand the effects of pH on biochemical changes, oxygen diffusion, and its impact on meat color. Recent updates utilizing high-throughput “omics” approaches to elucidate the biochemical changes associated with high-pH meat are also dis-cussed. The fundamental aspects affecting fresh meat color are complex and highly interrelated with factors ranging from live animal production to preharvest environmental issues, muscle to meat conversion, and numerous facets along the merchandising chain of marketing meat to consumers.

Effects of Farm Management Practices and Transport Time on Post-Mortem Changes of Longissimus lumborum Muscle Proteins in Suckling Goat Kids

The combined effect of farm management practices, transport time, and ageing time on the electrophoretic changes of sarcoplasmic (SPP) and myofibrillar (MFP) protein fractions of goat kids was studied. A total of 64 suckling goat kids were withdrawn from two farms with "high" (GW) and "low" (DW) welfare-friendly management practices, and they were transported for 2 or 6 h immediately before slaughtering. Longissimus lumborum samples were obtained at 3, 8, and 21 days post-mortem, and muscle proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis SDS-PAGE. Both protein extracts displayed significant changes attributable to meat maturation. Managing conditions of kids in DW farms increased the post-mortem susceptibility of muscle proteins. Some MFP of Longissimus lumborum muscle, such as troponin T, as well as 26-30 and 35-37 kDa fractions were influenced significantly by deficient on-farm management, and therefore, these protein fragments might be considered as indicators of low-welfare on-farm management in goat kids.

Sarcoplasmic Proteome Profile and Internal Color of Beef Longissimus Lumborum Steaks Cooked to Different Endpoint Temperatures

The complex relationship between endpoint temperature, sarcoplasmic proteome, and internal color in cooked steaks is yet to be examined. The objective of the present study was to characterize the changes in sarcoplasmic proteome and their influence on the internal color of beef longissimus lumborum (LL) steaks cooked to different endpoint temperatures. Two 2.5-cm-thick LL steaks were fabricated from 9 beef strip loins and were cooked to an internal endpoint temperature of either 60°C (C-60) or 71°C (C-71). Cooked steaks were cooled and sliced parallel to the grilled surface, and internal color was evaluated instrumentally. Sarcoplasmic proteome from the interiors of the cooked steaks was analyzed using two-dimensional electrophoresis, and the gel images were digitally analyzed. The protein spots exhibiting more than 2-fold intensity differences (P &lt; 0.05) were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry. The C-60 steaks demonstrated greater (P &lt; 0.05) redness and color stability than the C-71 ones. Eleven differentially abundant protein spots were identified, and they belonged to 6 functional groups (transport proteins, enzymes in energy metabolism, chaperones, antioxidant proteins, enzymes in amino acid metabolism, and glycolytic enzymes). While 10 spots were overabundant (P &lt; 0.05) in C-60 steaks, 1 spot was overabundant (P &lt; 0.05) in C-71 steaks. The spot overabundant in C-71 samples was identified as myoglobin, suggesting the possible role of post-translational modifications in the heme protein’s thermal stability. The results indicated that the endpoint cooking temperature influenced sarcoplasmic proteome profile and internal color of cooked beef LL steaks. The overabundant proteins in steaks cooked to 60°C may be exploited as potential biomarkers for undercooked beef, which is a source for foodborne infections.

Muscle Fiber Properties in Cattle and Their Relationships with Meat Qualities: An Overview

The control of meat quality traits constitutes an important target for any farm animal production, including cattle. Therefore, better understanding of the biochemical properties that drive muscle development and final outcomes constitutes one of the main challenging topics of animal production and meat science. Accordingly, this review has focused on skeletal muscle fibers in cattle and their relationships with beef qualities. It aimed to describe the chemical and structural properties of muscle fibers as well as a comprehensive review of their contractile and metabolic characteristics during the life of the animal. The existing methods for the classification of muscle fibers were reviewed, compared, and discussed. Then, the different stages of myogenesis in cattle were defined. The main factors regulating fetal and postnatal growth and the plasticity of muscle fibers were evidenced, especially the role of myostatin growth factor and the impact of nutritional factors. This review highlights that the knowledge about muscle fibers is paramount for a better understanding of how to control the muscle properties throughout the life of the animal for better management of the final eating qualities of beef. Accordingly, the associations between bovine muscle fibers and different meat eating qualities such as tenderness, pH decline, and color traits were further presented.

Lipid oxidation, pre-slaughter animal stress and meat packaging: Can dietary supplementation of vitamin E and plant extracts come to the rescue?

Normand cull-cows received a diet enriched in n-3 polyunsaturated fatty acids (PUFA), known to enhance nutritional quality, but to decrease beef lipid stability. Half of the cows received a supplementation of vitamin E and plant extracts rich in polyphenols during the finishing period. Half of each feeding group was slaughtered under limited, the others under added stress conditions. Longissimus thoracis (LT) and Semitendinosus (ST) were evaluated after storage under air, or 70% O₂/30% CO₂ or vacuum conditions. Irrespectively of diet, pre-slaughter stress i) increased post-mortem malondialdehyde (MDA) formation except in vacuum-stored meat, ii) decreased vitamin A levels in the LT, iii) decreased vitamin E levels in meat stored in 70% O₂/30% CO₂ and total anti-oxidant status in vacuum stored meat. Effects were global; dietary supplementation with vitamin E and plant extracts was associated with lower MDA levels and MetMb percentage and higher levels of vitamin A and E.

Predicting the Quality of Meat: Myth or Reality?

This review is aimed at providing an overview of recent advances made in the field of meat quality prediction, particularly in Europe. The different methods used in research labs or by the production sectors for the development of equations and tools based on different types of biological (genomic or phenotypic) or physical (spectroscopy) markers are discussed. Through the various examples, it appears that although biological markers have been identified, quality parameters go through a complex determinism process. This makes the development of generic molecular tests even more difficult. However, in recent years, progress in the development of predictive tools has benefited from technological breakthroughs in genomics, proteomics, and metabolomics. Concerning spectroscopy, the most significant progress was achieved using near-infrared spectroscopy (NIRS) to predict the composition and nutritional value of meats. However, predicting the functional properties of meats using this method-mainly, the sensorial quality-is more difficult. Finally, the example of the MSA (Meat Standards Australia) phenotypic model, which predicts the eating quality of beef based on a combination of upstream and downstream data, is described. Its benefit for the beef industry has been extensively demonstrated in Australia, and its generic performance has already been proven in several countries.

Beef Tenderness Prediction by a Combination of Statistical Methods: Chemometrics and Supervised Learning to Manage Integrative Farm-To-Meat Continuum Data

This trial aimed to integrate metadata that spread over farm-to-fork continuum of 110 Protected Designation of Origin (PDO)Maine-Anjou cows and combine two statistical approaches that are chemometrics and supervised learning; to identify the potential predictors of beef tenderness analyzed using the instrumental Warner-Bratzler Shear force (WBSF). Accordingly, 60 variables including WBSF and belonging to 4 levels of the continuum that are farm-slaughterhouse-muscle-meat were analyzed by Partial Least Squares (PLS) and three decision tree methods (C&RT: classification and regression tree; QUEST: quick, unbiased, efficient regression tree and CHAID: Chi-squared Automatic Interaction Detection) to select the driving factors of beef tenderness and propose predictive decision tools. The former method retained 24 variables from 59 to explain 75% of WBSF. Among the 24 variables, six were from farm level, four from slaughterhouse level, 11 were from muscle level which are mostly protein biomarkers, and three were from meat level. The decision trees applied on the variables retained by the PLS model, allowed identifying three WBSF classes (Tender (WBSF ≤ 40 N/cm²), Medium (40 N/cm² < WBSF < 45 N/cm²), and Tough (WBSF ≥ 45 N/cm²)) using CHAID as the best decision tree method. The resultant model yielded an overall predictive accuracy of 69.4% by five splitting variables (total collagen, µ-calpain, fiber area, age of weaning and ultimate pH). Therefore, two decision model rules allow achieving tender meat on PDO Maine-Anjou cows: (i) IF (total collagen < 3.6 μg OH-proline/mg) AND (µ-calpain ≥ 169 arbitrary units (AU)) AND (ultimate pH < 5.55) THEN meat was very tender (mean WBSF values = 36.2 N/cm², n = 12); or (ii) IF (total collagen < 3.6 μg OH-proline/mg) AND (µ-calpain < 169 AU) AND (age of weaning < 7.75 months) AND (fiber area < 3100 µm²) THEN meat was tender (mean WBSF values = 39.4 N/cm², n = 30).

Gender status effect on carcass and meat quality traits of feedlot Angus × Nellore cattle

The study evaluated the effect of gender status on carcass and meat quality of feedlot Angus × Nellore cattle. A total of 176 cattle, 20 months old, were confined for 190-days and assigned to four treatments: bulls, immunocastrated, steers, and heifers. Bulls had greater rib eye area and HCW (p = 0.0001). Heifers had increased fat thickness (p = 0.0001). Steers and heifers had higher marbling scores (p = 0.0001). There was interaction between gender and aging time for Warner-Bratzler Shear Force (p = 0.0002), L* (p = 0.0118), and b* (p = 0.0113) values of beef. The sensory panel results showed that beef from bulls had the lowest consumer overall acceptance (p = 0.0278). Especially, regardless tenderness, steers and immunocastrated beef were considered tender, independent of aging time. Beef produced by heifers, steers, and immunocastrated is considered to be of higher quality than bulls. Thus, it is may be an interesting alternative to produce high-quality beef than bulls, to attend the consumer demand for high-quality products. Additionally, the low fatty acids n6 levels and low n6:n3 ratio, high levels of CLA, MUFAs, and oleic acid suggests that the heifer meat is favorable for human health.

The associations between proteomic biomarkers and beef tenderness depend on the end-point cooking temperature, the country origin of the panelists and breed

Steaks of 74 animals from 3 young bull breeds (Aberdeen Angus, Limousin and Blond d'Aquitaine) were cooked at two end-point cooking temperatures (55 and 74 °C) and evaluated for tenderness by trained panelists from France (FR) and the United Kingdom (UK). Using principal component regressions, the tenderness scores of each breed, country origin of the panelists and cooking temperature were linked with the abundances of 21 protein biomarkers belonging to five biological pathways. Twelve regression equations were built and explained 68 to 95% of tenderness variability. A high dissimilarity in the retained biomarkers was observed among the equations and differences exist among breeds, cooking temperatures and country origin of the panelists. Among the 21 biomarkers, 6 proteins including structural (MyHC-I, MyHC-IIa, MyHC-IIx), oxidative stress (DJ-1, PRDX6) and proteolysis (CAPN1) were retained robustly in positive or negative directions in the tenderization process of Longissimus thoracis, regardless the breed, the end-point cooking temperature or the country origin of the panelist.

Beef tenderness and intramuscular fat proteomic biomarkers: Effect of gender and rearing practices

This study analyzed the effect of gender on the abundances of 20 protein biomarkers of tenderness and/or intramuscular fat content in five muscles: Longissimus thoracis, previously identified as biomarkers of tenderness and/or intramuscular Semimembranosus, Rectus abdominis, Triceps brachii and Semitendinosus, from cows and steers of the Protected Designation Origin Maine Anjou. The protein abundances were quantified using Reverse Phase Protein Array with specific validated antibodies. Among the 20 studied proteins, the abundance of 8 biomarkers involved in energetic metabolism, contraction and cellular stress, was different according to gender. The gender effect was different depending on the muscle type with greater abundances in Semitendinosus, Rectus abdominis and Longissimus thoracis muscles. On the basis of animal characteristics and rearing factors, three rearing practices classes were identified for cows. Among the factors, fattening duration modified the abundance of 12 proteins mainly in Triceps brachii muscle. A positive correlation between the abundance of the small HSP20 and slaughter age was observed in the 5 muscles. Two proteins, Four and a half LIM domains 1 (FHL1) and Glycogen phosphorylase (PYGB) appeared to be muscle, gender and rearing practices independent. These results constitute valuable data to understand how to manage beef quality by controlling these different factors. SIGNIFICANCE: This study is the first to compare the relative abundance of 20 proteins previously identified as biomarkers of tenderness and/or intramuscular fat (IMF) content of beef meat between cows and steers among 5 different muscles. Its originality is in the use of Reverse Phase Protein Array for fast quantification of the proteins and the integration of data from rearing factors, carcass characteristics and biomarkers of meat qualities. The findings provide evidence for modulating biomarker levels by controlling the choice of animal type and rearing factors according to the type of muscle that would produce animals with the desired meat qualities.