The color of fresh pork: Consumers expectations, underlying farm-to-fork factors, myoglobin chemistry and contribution of proteomics to decipher the biochemical mechanisms

The color of fresh pork is a crucial quality attribute that significantly influences consumer perception and purchase decisions. This review first explores consumer expectations and discrimination regarding pork color, as well as an overview of the underlying factors that, from farm-to-fork, contribute to its variation. Understanding the husbandry factors, peri- and post-mortem factors and consumer preferences is essential for the pork industry to meet market demands effectively. This review then delves into current knowledge of pork myoglobin chemistry, its modifications and pork discoloration. Pork myoglobin, which has certain peculiarities comparted to other meat species, plays a weak role in determining pork color, and a thorough understanding of the biochemical changes it undergoes is crucial to understand and improve color stability. Furthermore, the growing role of proteomics as a high-throughput approach and its application as a powerful research tool in meat research, mainly to decipher the biochemical mechanisms involved in pork color determination and identify protein biomarkers, are highlighted. Based on an integrative muscle biology approach, the available proteomics studies on pork color have enabled us to provide the first repertoire of pork color biomarkers, to shortlist and propose a list of proteins for evaluation, and to provide valuable insights into the interconnected biochemical processes implicated in pork color determination. By highlighting the contributions of proteomics in elucidating the biochemical mechanisms underlying pork color determination, the knowledge gained hold significant potential for the pork industry to effectively meet market demands, enhance product quality, and ensure consistent and appealing pork color.

The potential of metabolomics in meat science: Current applications, future trends, and challenges

Metabolites are the final products of metabolism and provide insights into the biochemical balance of tissue systems. A cascade of reactions involving proteins, carbohydrates, and lipids affects meat color, tenderness, and flavor, specifically, metabolites that are key biomolecules in biochemical reactions associated with attainment of acceptable meat quality. Bioinformatics platforms, such as Kyoto Encyclopedia of Genes and Genomes (KEGG) databases and MetaboAnalyst, are utilized to help understanding the role of differentially abundant metabolites and characterizing their roles in cellular function/metabolism. However, the inability to identify all metabolites using a single platform and limited metabolite libraries specifically for meat/food remains a challenge. Therefore, the advances in metabolite separation, easy-to-use data processing, increased resolution of mass-spectrometry, and data analysis will help to make inferences or develop biomarkers related to meat quality. This review discusses how metabolomics can be exploited to characterize meat quality, the challenges, and current trends. SIGNIFICANCE: Metabolites are the final products of metabolism and provide insights into the biochemical balance of tissue systems. They play an important role in quality traits (i.e., color, texture, and flavor) and nutritive value of foods. Visual appearance of fresh foods, such as muscle foods, are utilized by consumers to assess the quality at the retail market before making purchases. Similarly, tenderness and flavor of meats influence eating satisfaction and re-purchase decisions. Inconsistencies in meat quality lead to huge economic losses to food industry. For instance, consumers often associate a bright-cherry red color with freshness, and the US beef industry loses $3.74 billion annually due to discoloration during storage. Both pre-and post-harvest factors influence the extent of meat quality changes. Metabolomics offer robust tools to get a snapshot of small molecules such as acids, amino acids, glycolytic- and tricarboxylic acids, fatty acids, and sugars present in post-mortem muscle tissue and their role in meat quality. Further, using bioinformatics platforms enables characterizing the role of differentially present metabolites in meat quality as well as identifying biomarkers for desirable quality traits such as tender meat or color-stable carcasses. Innovative applications of metabolomics can be exploited to elucidate the underpinnings of meat quality and to develop novel strategies to enhance marketability of retail fresh meats.

Proteomic approaches to characterize biochemistry of fresh beef color

Color of retail fresh beef is the most important quality influencing the consumers' purchase decisions at the point of sale. Discolored fresh beef cuts are either discarded or converted to low-value products, before the microbial quality is compromised, resulting in huge economic loss to meat industry. The interinfluential interactions between myoglobin, small biomolecules, proteome, and cellular components in postmortem skeletal muscles govern the color stability of fresh beef. This review examines the novel applications of high-throughput tools in mass spectrometry and proteomics to elucidate the fundamental basis of these interactions and to explain the underpinning mechanisms of fresh beef color. Advanced proteomic research indicates that a multitude of factors endogenous to skeletal muscles critically influence the biochemistry of myoglobin and color stability in fresh beef. Additionally, this review highlights the potential of proteome components and myoglobin modifications as novel biomarkers for fresh beef color. SIGNIFICANCE: Color of retail fresh beef is the most important quality influencing the consumers' purchase decisions at the point of sale. Discolored fresh beef cuts are either discarded or converted to low-value products, before the microbial quality is compromised, resulting in huge economic loss to meat industry. The interinfluential interactions between myoglobin, small biomolecules, proteome, and cellular components in postmortem skeletal muscles govern the color stability of fresh beef. High-throughput tools in mass spectrometry and proteomics are exploited to elucidate the fundamental basis of these interactions and to explain the underpinning mechanisms of fresh beef color. Advanced proteomic research also highlights the potential of proteome components and myoglobin modifications as novel biomarkers for fresh beef color. The novel findings from proteomic studies would help engineering innovative strategies to improve fresh beef color, minimize food waste, and maximize the economic competitiveness of global meat industry.

Characterization of Pork Loin Chop Color Stability Using Loin Quality Traits and Instrumental Discoloration Measures

The objective of this study was to characterize the color stability of pork loin chops using fresh quality traits and instrumental measures of discoloration. Boneless pork loins (N=484) were evaluated for quality traits at 11 or 14 d post-mortem. One chop was cut from each loin near the 10th rib for retail display, overwrapped, and displayed under constant fluorescent lighting for 7 d. Objective color, myoglobin redox forms, and subjective visual discoloration traits were evaluated daily. After retail display, chops were categorized based on final visual discoloration (Day 7) as Very Color Stable (VCS; 0% to 5% discoloration), Color Stable (CS; 5% to 10% discoloration), Neutral (10% to 25% discoloration), Color Labile (CL; 25% to 30% discoloration), or Very Color Labile (VCL; >30% discoloration). Quality and color traits were analyzed using the GLIMMIX (visual discoloration) or MIXED (all other measures) procedure of SAS. Retail display data were analyzed as repeated measures. Chops ultimately classified as CS or VCS were darker, redder, and had lesser surface metmyoglobin (P<0.01) than CL and VCL chops at both Day 1 of retail display and throughout display. Stable chops also had generally increased R630/580 values as well as decreased visual discoloration scores and yellowness during display. A group×day interaction was observed for all traits measured during retail display (P<0.0001). No differences in aged loin ventral surface redness were observed between color stability groups (P≥0.16). Overall, chops ultimately classified as CS came from aged loins that were generally darker, redder, and less yellow, with greater pH values, greater marbling scores,and decreased purge loss.

Supranutritional Supplementation of Vitamin E Influences Myoglobin Post-Translational Modifications in Postmortem Beef Longissimus Lumborum Muscle

Post-translational modifications (PTM) in myoglobin (Mb) can influence fresh meat color stability. Dietary supplementation of vitamin E improves beef color stability by delaying lipid oxidation–induced Mb oxidation and influences proteome profile of postmortem beef skeletal muscles. Nonetheless, the influence of vitamin E on Mb PTM in postmortem beef skeletal muscles has yet to be investigated. Therefore, the objective of the current study was to examine the effect of dietary vitamin E on Mb PTM in postmortem beef longissimus lumborum muscle. Beef longissimus lumborum muscle samples (24 h postmortem) were obtained from the carcasses of 9 vitamin E–supplemented (VITE; 1,000 IU vitamin E diet/heifer·d−1for 89 d) and 9 control (CONT; no supplemental vitamin E) heifers. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to separate Mb from other sarcoplasmic proteins of beef longissimus lumborum muscle. Tandem mass spectrometry identified multiple PTM (phosphorylation, acetylation, 4-hydroxynonenalalkylation, methylation, dimethylation, trimethylation, and carboxymethylation) in the protein bands (17 kDa) representing Mb. The amino acids susceptible to phosphorylation were threonine (T) and tyrosine (Y), whereas lysine (K) residues were prone to other PTM. The same sites of phosphorylation (T34, T67, Y103), carboxymethylation (K77, K78), and 4-hydroxynonenal alkylation (K77, K78, K79) were identified in Mb from CONT and VITE samples, indicating that these PTM were not influenced by the vitamin E supplementation in cattle. Nonetheless, differential occurrence of acetylation, methylation, dimethylation, and trimethylation were identified in Mb from CONT and VITE samples. Overall, a greater number of amino acids were modified in CONT than VITE, suggesting that the supplementation of vitamin E decreased thenumbers of post-translationally modified residues in Mb. Additionally, PTM at K87, K96, K98, and K102 were unique to CONT, whereas PTM at K118 were unique to VITE. These findings suggested that dietary supplementation of vitamin E in beef cattle might protect amino acid residues in Mb—especially those located spatially close to proximal histidine—from undergoing PTM, thereby improving Mb redox stability.

Color attributes and myoglobin chemistry exhibit relationships with tenderness and calpain-1 abundance in postmortem Longissimus lumborum muscles from Holstein heifers

The objective of this study was to determine the extent that myoglobin and beef color are associated with calpain-1 relative abundance relative and tenderness. Longissimus lumborum (LL) samples from the left side of Holstein beef carcasses (n = 31) were collected immediately post-evisceration for 0 h analyses. At 48 h postmortem six steaks were removed from the right side of each carcass for analyses at 48 and 336 h postmortem. Myoglobin concentrations resulted in negative correlations (P < 0.05) to Warner-Bratzler shear force (WBSF) values at 336 h postmortem. L*, a*, and b* values at 48 h resulted in positive correlations (P < 0.05) with WBSF values at 48 and 336 h. Values for b* at 336 h had positive correlations with calpain-1 concentration at 0 and 336 h. Data from this study indicate a potential relationship between myoglobin concentration and meat color with tenderness aspects and calpain-1 relative abundance.

Myoglobin and hemoglobin: discoloration, lipid oxidation and solvent access to the heme pocket

Conversion of the heme iron in myoglobin (Mb) and hemoglobin (Hb) from Fe2+ to Fe3+is a critical step that causes quality deterioration in muscle foods, such as discoloration and generation of oxidative species, including dissociated heme that oxidize lipids and proteins. Increased solvent access to the heme pocket has been proposed to cause oxidation of the heme iron and decrease heme affinity, although empirical results are lacking.&nbsp; This review introduces plasma induced modification of biomolecules (PLIMB) as an approach to modify amino acids of Mb and Hb and thereby assess solvent access to the heme pocket. After PLIMB, liquid chromatography tandem mass spectrometry (LC-MS/MS) peptide analysis and a user-friendly, software platform is utilized to quantify modified amino acid side chains of the heme proteins. Our current findings indicate that PLIMBàLC-MSMS provides a platform to measure solvent access to portions of the heme pocket environment. Evaluation of PLIMB at additional conditions (e.g.&nbsp;different pH values) is underway to better delineate the role of solvent access to the heme pocket relative to the ‘outer-sphere’ mechanism of heme protein oxidation and the ability of hydrogen bonding to stabilize heme within metHbs. Some aspects of heme protein-mediated lipid oxidation that occur at low O2&nbsp;partial pressures are discussed in relation to solvent access to the heme pocket. Other approaches to study mechanisms of discoloration and lipid oxidation related to Mb/Hb oxidation and heme loss from metHb are also discussed.

AMSA Meat Color Measurement Guidelines

Meat color is an important aspect of consumer’spurchase decisions regarding meat products.&nbsp;Perceived meat color results from the interaction of light, a detector(i.e. human eye), and numerous factors that are both intrinsic and extrinsic tothe muscle which influence the chemical state of myoglobin.&nbsp; The complex nature of these interactions dictatesthat decisions regarding evaluations of meat color be made carefully, and thatinvestigators have a basic knowledge of the physical and chemical factorsaffecting their evaluations.&nbsp; Theseguidelines were compiled to aid investigators in navigating the pitfalls ofmeat color evaluation and ensure the reporting of information needed forappropriate interpretation of the resulting data.&nbsp; The guidelines provide an overview ofmyoglobin chemistry, the perception of meat color, in addition to details ofinstrumentation used in meat color evaluation.&nbsp;Moreover, these guidelines detail practical considerations for simulatedretail display studies and provide details of the most common laboratorytechniques used in meat color literature.&nbsp;Importantly, the guidelines indicate the information that should beincluded when reporting meat color research to aid in appropriateinterpretation.&nbsp; Practical considerationsneeded for troubleshooting meat color problems in a commercial setting areincluded as well.&nbsp; Investigators areencouraged to review the entire guidelines before designing and conducting meatcolor research.

Tandem Mass Tag Labeling-Based Analysis to Characterize Muscle-Specific Proteome Changes during Postmortem Aging of Bison Longissimus Lumborum and Psoas Major Muscles

The objective of the study was to examine the variations in sarcoplasmic proteomes of bison longissimus lumborum (LL) and psoas major (PM) muscles during postmortem aging utilizing tandem mass tag (TMT) isobaric labeling coupled with liquid chromatography mass-spectrometry (LC-MS/MS) for the categorization of muscles with muscle-specific inherent color stability. A total of 576 proteins were identified (P < 0.05) in both bison LL and PM muscles, where 97 proteins were identified as differentially abundant (fold change > 1.5, P < 0.05) from the three comparisons between muscles during postmortem aging periods (PM vs LL at 2 d, 7 d and 14 d). Among those proteins, the most important protein groups based on functions are related to electron transport chain (ETC) or oxidative phosphorylation, tricarboxylic acid cycle (TCA), ATP transport, carbohydrate metabolism, fatty acid oxidation, chaperones, oxygen transport, muscle contraction, calcium signaling, and protein synthesis. In PM, most of the proteins from ETC, TCA cycle, fatty acid oxidation, ATP and oxygen transport, and muscle contraction were more abundant or exhibited increased expression during aging compared to LL. On the other hand, the proteins involved in carbohydrate metabolism, chaperone function and protein synthesis mostly exhibited decreased expression in PM muscle relative to LL. These results clearly demonstrate that the proteins associated with oxidative metabolism showed increased expression in PM muscles. This indicates that oxidative damage or subsequent color deterioration resulted in bison PM muscles being attacked by the reactive oxygen species produced during those metabolic process. In contrast, proteins involved in glycolysis and chaperone activity exhibited a decrease in expression in bison PM muscles, resulting decline in color stability compared with LL. Because glycolytic enzymes and chaperones maintain oxidative and/or color stability by producing reducing equivalents in glycolytic pathway and with the protein folding ability of chaperones, respectively in LL muscles.

Variations in intramuscular fat content and profile in Angus x Nellore steers under different feeding strategies contribute to color and tenderness development in longissimus thoracis

Muscle from cattle reared under different finishing regime (grain vs. forage) and growth rate may have divergent metabolic signatures that are reflective of their inherent differences in biochemical processes that may impact its subsequent transformation into high quality beef. Differences in muscle lipid profiles were characterized in Angus x Nellore crossbred steers, using multiple reaction monitoring (MRM)-profiling, to identify potential metabolic signatures correlated to beef color and tenderness in the longissimus thoracis muscle of cattle fed in either a feedlot- or pasture-based system programmed to achieve either a high or low growth rate. A total of 440 MRMs were significant, which were related mainly to triglycerides and phosphatidylcholine lipids. Distinct clusters between feeding strategies for the lipid dataset were revealed, which affected glycerolipid metabolism (P = 0.004), phospholipid metabolism (P = 0.009), sphingolipid metabolism (P = 0.050) and mitochondrial beta-oxidation of long chain saturated fatty acids (P = 0.073) pathways. Lipid content and profile differed to feeding strategies, which were related to L*, a*, and tenderness. These findings provide a comprehensive and in-depth understanding of lipidomic profiling of beef cattle finished under different feeding strategies and provides a basis for the relationship between lipid content and profiles and beef quality development.

Differential Abundance of Mitochondrial Proteome Influences the Color Stability of Beef <i>Longissimus Lumborum</i> and <i>Psoas Major</i> Muscles

Mitochondrial functionality affects muscle-specific beef color stability. Nonetheless, the relationship between mitochondrial proteome and muscle-specific beef color stability is yet to be examined. Therefore, the objective of the present study was to differentiate the proteomes of mitochondria from beef longissimus lumborum (LL; color-stable muscle) and psoas major (PM; color-labile muscle) steaks during retail display. LL and PM muscles from 7 beef carcasses (USDA Choice; 48 h postmortem) were fabricated into 1.92-cm-thick steaks and were aerobically packaged and retail displayed for 6 d. Mitochondria were isolated on day 3 and 6, whereas instrumental color and biochemical attributes were evaluated on day 0, 3, and 6. Mitochondrial proteome was analyzed employing two-dimensional electrophoresis. The protein spots exhibiting 1.5-fold or more intensity differences (P &lt; 0.05) between the muscles and display days were subjected to tryptic digestion and identified by tandem mass spectrometry. Whereas color stability decreased in both muscles during retail display, LL steaks demonstrated greater (P &lt; 0.05) color stability during display than their PM counterparts. Mitochondria could not be isolated from PM steaks on day 6 because of extensive degradation. Seven proteins were differentially abundant ( P &lt; 0.05) in LL and PM on day 3 of display. In LL steaks, 7 proteins were more abundant (P &lt; 0.05) on day 3 than on day 6 of retail display. The differentially abundant proteins were enzymes, binding proteins, and proteins involved in biosynthesis. These results indicated that differential abundance of mitochondrial proteome could also contribute to the variations in color stability of beef LL and PM muscles during retail display.

Myoglobin Post-Translational Modifications Influence Color Stability of Beef Longissimus Lumborum

Post-translational modifications (PTM) of proteins play critical roles in biological processes. PTM of muscle proteins influence meat quality. Nonetheless, myoglobin (Mb) PTM and their impact on fresh beef color stability have not been characterized yet. Therefore, our objectives were to identify Mb PTM in beef longissimus lumborum muscle during postmortem aging and to characterize their influence on color stability. The longissimus lumborum muscles from 9 (n = 9) beef carcasses (24 h postmortem) were subjected to wet aging for 0, 7, 14, and 21 d. At the end of each wet-aging period, steaks were fabricated. One steak for analyses of PTM was immediately frozen at −80°C, whereas other steaks were assigned to refrigerated storage in the darkness under aerobic packaging. Instrumental color and biochemical attributes were evaluated on day 0, 3, or 6 of storage. Mb PTM were analyzed using two-dimensional electrophoresis and tandem mass spectrometry. Surface redness (a* value), color stability, and Mb concentration decreased (P &lt; 0.05) upon aging. Gel image analyses identified 6 Mb spots with similar molecular weight (17 kDa) but different isoelectric pH. Tandem mass spectrometry identified multiple PTM (phosphorylation, methylation, carboxymethylation, acetylation, and 4-hydroxynonenal alkylation) in these 6 isoforms. The amino acids susceptible to phosphorylation were serine (S), threonine (T), and tyrosine, whereas other PTM were detected in lysine (K), arginine (R), and histidine residues. Additionally, distal histidine (position 64), critical to heme stability, was found to be alkylated. Overall, Mb PTM increased with aging. The aging-induced PTM, especially those occurring close to hydrophobic heme pocket, could disrupt Mb tertiary structure, influence heme affinity, and compromise oxygen binding capacity, leading to decreased color stability of fresh beef. Furthermore, PTM at K45, K47, and K87 were unique to Mb from non-aged beef, whereas PTM at R31, T51, K96, K98, S121, R139, and K147 were unique to Mb from aged counterparts, indicating that these Mb PTM could be used as novel biomarkers for fresh beef color stability.

Broiler genetics influences proteome profiles of normal and woody breast muscle

Wooden or woody breast (WB) is a myopathy of the pectoralis major in fast-growing broilers that influences the quality of breast meat and causes an economic loss in the poultry industry. The objective of this study was to evaluate growth and proteome differences between 5 genetic strains of broilers that yield WB and normal breast (NB) meat. Eight-week-old broilers were evaluated for the WB myopathy and divided into NB and WB groups. Differential expression of proteins was analyzed using 2-dimensional gel electrophoresis and LC-MS/MS to elucidate the mechanism behind the breast myopathy because of the genetic backgrounds of the birds. The percentages of birds with WB were 61.3, 68.8, 46.9, 45.2, and 87.5% for strains 1-5, respectively, indicating variability in WB myopathy among broiler strains. Birds from strains 1, 3, and 5 in the WB group were heavier than those in the NB group (P < 0.05). Woody breast meat from all strains were heavier than NB meat (P < 0.05). Within WB, strain 5 had a greater breast yield than strains 1, 3, and 4 (P < 0.0001). Woody breast from strains 2, 3, 4, and 5 had a greater breast yield than NB (P < 0.05). Six proteins were more abundant in NB of strain 5 than those of strains 2, 3, and 4, and these proteins were related to muscle growth, regeneration, contraction, apoptosis, and oxidative stress. Within WB, 14 proteins were differentially expressed between strain 5 and other strains, suggesting high protein synthesis, weak structural integrity, intense contraction, and oxidative stress in strain 5 birds. The differences between WB from strain 3 and strains 1, 2, and 4 were mainly glycolytic. In conclusion, protein profiles of broiler breast differed because of both broiler genetics and the presence of WB myopathy.

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.

Early Postmortem Proteome Changes in Normal and Woody Broiler Breast Muscles

Early postmortem changes in the whole muscle proteome from normal broiler (NB) and woody broiler (WB) breasts at 0 min, 15 min, 4 h, and 24 h after slaughter were analyzed using two-dimensional gel electrophoresis (2DE) and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Elongation factor 2, EH domain-containing protein 2, phosphoglycerate mutase 1 (PGAM1), and T-complex protein 1 subunit gamma were differentially abundant in both NB and WB muscles during the early postmortem storage. Twenty additional proteins were differentially abundant among four postmortem time points in either NB or WB muscles. In the postmortem WB, changes in protein degradation were observed, including the degradation of desmin fragments, ovotransferrin chain A, and troponin I chain I. Additionally, a few glycolytic proteins in the WB might have undergone post-translational modification, including enolase, phosphoglucomutase-1, PGAM1, and pyruvate kinase. These changes in protein biomarkers highlight the impact of WB myopathy on postmortem proteome changes and increase our understanding of the relationship between WB conditions, postmortem biochemistry, and meat quality.

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.

Thermal Instability Induced by 4-Hydroxy-2-Nonenal in Beef Myoglobin

The secondary products of lipid oxidation, such as 4-hydroxy-2-nonenal (HNE), compromise myoglobin (Mb) redox stability and can thus impact thermal stability. Previous studies examined HNE-induced redox instability in beef Mb, whereas investigations are yet to be undertaken to evaluate the relationship between lipid oxidation and thermal stability of beef Mb. Therefore, the objective of the present study was to investigate the direct influence of HNE on thermal stability of beef Mb at meat conditions. Beef oxymyoglobin (0.15 mM) was incubated with HNE (1.0 mM) at pH 5.6 and 4°C for 21 d in the dark. Metmyoglobin formation, percentage Mb denaturation (PMD), and HNE adduction sites in Mb were examined on days 0, 7, 14, and 21. The experiment was replicated 3 times (n = 3). The data were evaluated using the MIXED procedure of SAS, and the differences among means were detected at the 5% level using the least significant difference test. The HNE-treated samples exhibited greater (P &lt; 0.05) metmyoglobin formation and PMD than the controls. Additionally, the PMD difference between HNE-treated and control samples increased (P &lt; 0.05) over time. Mass spectrometric analyses indicated that the number of HNE adduction sites increased with storage, and 6 histidines (positions 24, 36, 64, 93, 113, and 152) were adducted on day 21. HNE adduction at the distal histidine (position 64), which is critical to he me stability, was observed only on days 14 and 21. An increase in PMD on days 14 and 21 in HNE-treated samples could be partially due to the adduction at distal histidine. These findings indicated that HNE compromises thermal stability of beef Mb, possibly through altering the conformation of the heme protein by nucleophilic adduction.

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.

Metabolites and Metabolic Pathways Correlated With Beef Tenderness

Metabolite profile has been used to understand the causes of variability in beef tenderness, but still little is known about how metabolites contribute to beef quality. Therefore, this study was carried out to evaluate how meat metabolites and their metabolic pathways correlate to variability in beef tenderness. Carcasses from 60 noncastrated male cattle were selected, and three 2.5-cm-thick longissimus thoracis steaks were obtained and aged (0°C to 4°C) for 7d. Warner-Bratzler shear force (WBSF) was performed (steak 1). Based on WBSF data, 2 tenderness classes (n = 30; 15 per class [tender and tough]) were created to perform sarcomere length (steak 2) and metabolom ic analysis (steak 3). Meat ultimate pH did not differ between tenderness classes. However, steaks classified as tender had greater sarcomere length (P = 0.019) than those classified as tough. Acetyl-carnitine (P = 0.026), adenine (P = 0.026), beta-alanine (P = 0.005), fumarate (P = 0.022), glutamine (P = 0.043), and valine (P = 0.030) concentration were higher in tender beef compared with tough beef. The 4 most important compounds differing between tender and tough beef were lactate, glucose, creatine, and glutamine, which may indicate that metabolic pathways such as D-glutamine and D-glutamate metabolism, beta-alanine metabolism, purine metabolism, and tricarboxylic acid cycle affected the tenderness classes. Beta-alanine (r = − 0.45), acetyl-carnitine (r = − 0.40), fumarate (r = − 0.38), valine (r = − 0.34), glucose (r = − 0.32), glutamine (r = − 0.31), and adenine (r = −0.31) were negatively correlated with WBSF values. Metabolite profile in tender beef indicated a greater oxidative metabolism, which promoted modifications in the muscle structure and proteolysis, favoring its tenderization.

Proteomic Characterization of Normal and Woody Breast Meat from Broilers of Five Genetic Strains

Woody breast (WB) is an emergent broiler myopathy that is macroscopically characterized by hardened areas of the Pectoralis major muscle. Five genetic strains (strains 1–5) of mixed-sex broilers were fed either a control or an amino acid (AA)-reduced diet (20% reduction of digestible lysine, total sulfur AAs, and threonine) for 8 wk. Differences between whole-muscle proteome profiles of normal breast (NB; n = 6 gels) and WB tissue (n = 6 gels) were characterized for (1) broiler strains 1–5 that were fed with a control diet and collected at 0 min; (2) strain 5 (control diet) that were collected at 15 min, 4 h, and 24 h; (3) strain 5 (0 min) that were fed with a control and an AA-reduced diet. Birds that yielded WB were heavier and had a greater pH at death (pH0min) than normal birds. Results indicated that 21 proteins were more abundant (P &lt; 0.05) and 3 proteins were less abundant (P &lt; 0.05) in WB compared with NB. The differentially abundant proteins in each comparison were consistently upregulated or downregulated in WB tissue although the different protein profiles were noticed for each comparison. Strains 2 and 5 had more protein profile differences between WB and NB meat than strains 1, 3, and 4, which potentially indicates a stronger genetic component for strains 2 and 5 with respect to WB formation. The proteins that were more abundant in WB compared to NB are involved in carbohydrate metabolism, oxidative stress, cytoskeleton structure, and transport and signaling. Ingenuity Pathway Analysis indicated that regulated pathways in WB were mainly related to carbohydrate metabolism, cellular repair, cellular organization and maintenance, and cell death and survival. The results support the potential causes of WB myopathy, including the presence of hypoxia, oxidative stress, increased apoptosis, misfolded proteins, and inflammation.

Muscle-specific color stability in fresh beef from grain-finished Bos indicus cattle

Objective

To investigate the color and oxidative stabilities of longissimus lumborum (LL) and psoas major (PM) muscles from grain-finished Bos indicus cattle in Brazil.

Methods

The LL and PM muscles were obtained 24 h post-mortem from eight (n = 8) Nellore bull carcasses, fabricated into 1.5-cm steaks, aerobically packaged, and stored at 4°C for nine days. Steaks were analyzed for myoglobin concentration, pH, instrumental color, metmyoglobin reducing activity (MRA) and lipid oxidation.

Results

The LL steaks exhibited greater (p<0.05) redness, color stability, and MRA than their PM counterparts on days 5 and 9. The LL and PM steaks demonstrated similar (p>0.05) lightness and yellowness on days 0, 5, and 9. On the other hand, PM steaks exhibited greater (p<0.05) myoglobin concentration, pH, and lipid oxidation than their LL counterparts.

Conclusion

These results indicated that muscle source influenced the color and oxidative stabilities of beef from grain-finished Bos indicus animals. These results highlighted the necessity of muscle-specific strategies to improve the color stability of beef from grain-fed Bos indicus cattle.

Muscle-Specific Color Stability of Fresh Meat from Springbok (Antidorcas marsupialis)

Springbok (Antidorcas marsupialis), a popular South African game species, has significant potential in meat production. Considering the importance of fresh meat color on consumers’ purchasing intent, the objective of this study was to evaluate the color stability of 3 economically important springbok muscles, infraspinatus (IS), longissimus thoracis et lumborum (LTL), and biceps femoris (BF). The IS, LTL, and BF muscles from both sides of 12 (6 male and 6 female) springbok carcasses were utilized. The muscles were fabricated (72 h postmortem) into 2.5-cm thick steaks, which were aerobically over-wrapped and stored for 8 d at 2°C. Surface color, myoglobin redox forms, pH, metmyoglobin reducing activity, total iron content, and myoglobin concentration were evaluated. Data were analyzed using mixed model repeated measures ANOVA. The IS exhibited greater (P < 0.05) redness, chroma, color stability, pH, oxymyoglobin content, and metmyoglobin reducing activity than its LTL and BF counterparts. Moreover, metmyoglobin formation and total iron content were lower in IS than in LTL and BF. The IS demonstrated stable redness and chroma throughout the storage, whereas the LTL and BF exhibited a steady decline. The results indicated that springbok IS muscle was the most color stable, while the LTL and BF did not differ in color stability from each other. These findings also suggested that muscle-specific processing methods could be utilized to improve retail color stability for fresh meat from springbok.

Harvest Method Influences Color Stability of Longissimus Lumborum Steaks from Bos indicus Cattle

Brazil is a major beef exporter to countries where religious slaughter without stunning is mandatory. Fresh beef color influences consumers’ purchase decisions, and harvest method influences beef quality attributes, such as color, water holding capacity, pH, and lipid oxidation. Beef color is a breed-specific trait, and the excitable temperament of Bos indicus cattle can affect fresh meat color. Nonetheless, the effects of harvest method on color and oxidative stabilities of beef from Bos indicus cattle have not been investigated yet. Therefore, our objective was to evaluate the impact of harvest method on color and oxidative stabilities of longissimus lumborum (LL) steaks from Bos indicus beef cattle. The LL muscles (24 h post-mortem) were obtained from 12 Nellore bull carcasses, harvested by either captive bolt stunning (CBP; n = 6) or without stunning (NST; n = 6). The muscles were fabricated into 2.54-cm steaks, aerobically packaged, and stored for 9 d at 4°C in darkness. Myoglobin concentration was analyzed on d 0, whereas pH, instrumental color, lipid oxidation, and water holding capacity were evaluated on d 0, 3, 6, and 9. While CBP and NST steaks exhibited similar (P > 0.05) myoglobin concentration (4.84 mg/g in CBP; 4.84 mg/g in NST), CBP steaks exhibited greater (P < 0.05) surface redness and color stability than their NST counterparts throughout the storage. On the other hand, NST steaks exhibited greater (P < 0.05) pH, yellowness, and water holding capacity than CBP steaks. Overall, the lightness and lipid oxidation were greater (P < 0.05) in NST steaks than their CBP counterparts. These results indicated that harvest method influences surface discoloration and oxidative stability of fresh LL steaks from Bos indicus cattle.

Muscle-Specific Mitochondrial Functionality and Its Influence on Fresh Beef Color Stability

Fresh beef color stability is a muscle-specific trait. Mitochondria remain biochemically active in postmortem beef muscles and influence meat color. Although several intrinsic factors governing muscle-specific beef color have been studied extensively, the role of mitochondrial functionality in muscle-dependent color stability is yet to be examined. Therefore, the objective of this study was to examine mitochondrial oxygen consumption rate (OCR), mitochondrial metmyoglobin reducing activity (MMRA), and instrumental color attributes in beef Longissimus lumborum (LL) and Psoas major (PM) during retail display. Using a split-plot design, six (n = 6) beef LL and PM muscles were fabricated into 2.54-cm-thick steaks, packaged in polyvinylchloride overwrap, and randomly assigned to instrumental color measurement for six days and mitochondrial isolation for days 0, 1, 3, or 5 of display at 4 °C. Mitochondria isolated from steaks were used to assess the effects of muscle and display time on OCR and MMRA. The PM steaks were less color-stable (p < 0.05) during display compared with the LL counterparts. For both muscles, OCR decreased during display, albeit the decrease was more rapid in PM than in the LL. Similarly, MMRA decreased during display for the LL and PM. However, this decrease was less (p < 0.05) for mitochondria from LL steaks, which were more resistant to display-mediated effects on OCR and MMRA. These results indicated that the muscle-specific differences in mitochondrial activity may contribute partially to the variations in color stability of beef LL and PM muscles.

PRACTICAL APPLICATION

During retail display tenderloin steaks packaged in PVC overwrap discolor quicker than strip loin steaks. This research determines the basis for muscle-specific differences in color stability. The results indicate that mitochondria present in tenderloin lose its functionality faster than strip loin mitochondria. Developing strategies to minimize muscle-specific differences in mitochondrial changes can increase color stability and value of fresh beef.

Meat quality traits and proteome profile of woody broiler breast (pectoralis major) meat

Woody breast meat has recently become prevalent in the broiler industry in both the United States and European Union. Recent publications have described the meat quality characteristics of woody breast meat as having hardened areas and pale ridge-like bulges at both the caudal and cranial regions of the breast. The present study investigated the meat quality (pH, color, cooking loss, and shear force) and protein quality characteristics (protein and salt-soluble protein content) in woody breast meat as compared to normal breast meat. In addition, the differences in the muscle proteome profiles of woody and normal breast meat were characterized. Results indicated that woody breast meat had a greater average pH (P < 0.0001) and cooking loss (P = 0.001) than normal breast meat, but woody breast meat did not differ in shear force (P > 0.05) in comparison to normal breast meat samples. The L*, a*, and b* values of woody breast fillets were greater than normal breast fillets (P < 0.0001 to L*; P = 0.002 to a*; P = 0.016 to b*). The woody breast meat had more fat (P < 0.0001) and moisture (P < 0.021) and less protein (P < 0.0001) and salt-soluble protein (P < 0.0001) when compared with normal breast fillets. Whole muscle proteome analysis indicated 8 proteins that were differentially expressed (P < 0.05) between normal and woody breast meat samples. The differences in muscle proteome between normal and woody breast meat indicated an increased oxidative stress in woody breast meat when compared to normal meat. In addition, the abundance of some glycolytic enzymes, which are critical to the regeneration of adenosine triphosphate (ATP) in postmortem muscles, was lower in woody breast meat than in normal breast meat. Proteomic differences provide additional information on the biochemical pathways and genetic variations that lead to woody breast meat. Further research should be conducted to elucidate the genetic and nutritional contributions to the proliferation of woody breast meat in the United States.

Color Stability of Fallow Deer (Dama dama) Infraspinatus, Longissimus Thoracis et Lumborum, and Biceps Femoris Muscles During Refrigerated Storage

Fallow deer (Dama dama) meat comprises a relatively small proportion of the game meat market in South Africa, despite having huge potential. To exploit its market potential, the quality attributes of fresh meat from fallow deer need to be characterized. Limited studies have been undertaken on the color stability of economically important muscles in game species. Therefore, the objective of the present study was to examine the color stability of 3 major muscles, i.e., infraspinatus (IS), longissimus thoracis et lumborum (LTL), and biceps femoris (BF), from fallow deer. The IS, LTL, and BF muscles were removed from both sides of 12 (6 male and 6 female) fallow deer carcasses. The muscles were fabricated into 2.5-cm steaks. The steaks were aerobically over-wrapped and stored at 2°C for 8 d. Meat pH, instrumental color, surface myoglobin redox forms, and metmyoglobin reducing activity were evaluated at specific intervals. Data were analyzed using mixed model repeated measures ANOVA, with gender, muscle, and time as fixed effects. The IS muscle exhibited greater (P < 0.05) pH, surface redness, color stability, oxymyoglobin content, and metmyoglobin reducing activity than the LTL and BF counterparts. In addition, surface metmyoglobin and total iron contents were lower in IS than in LTL and BF. While the IS demonstrated stable redness throughout the storage, the LTL and BF remained color stable only for 1 to 2 d. These findings suggested that fallow deer IS muscle is more color stable than the LTL and BF during refrigerated storage.

Impact of Light Source on Color and Lipid Oxidative Stabilities from a Moderately Color-Stable Beef Muscle during Retail Display

Consumers’ purchasing decisions are heavily impacted by fresh meat color, which they consider an indicator of quality in a retail setting. The objectives of this study were to evaluate the impact of light source on surface color and lipid oxidation during retail display of fresh steaks from semimembranosus (SM), a beef muscle with moderate oxidative and color stabilities. Steaks (n = 240) from the SM (n = 20) were packaged on Styrofoam trays and overwrapped with oxygen-permeable polyvinyl chloride. Steaks were then assigned to 1 of 3 lighting treatments, high UV fluorescent (HFLO), low UV fluorescent (FLO), and light emitting diode (LED) to mimic current storage conditions with a variety of industry available fluorescent bulbs, and evaluate emerging lighting conditions with LED. Steaks were removed on retail display d 1, 3, 5, and 7 for evaluation of instrumental color (L*, a*, and b* values), surface myoglobin redox forms, metmyoglobin reducing activity, and lipid oxidation. Light source influenced (P < 0.05) redness (a* values), with HFLO-displayed steaks having greatest (P < 0.05) a* values and LED-displayed steaks exhibiting lowest (P < 0.05) a* values. Surface redness decreased (P < 0.05) over retail display day. Steaks displayed in HFLO and FLO had greater (P < 0.05) oxymyoglobin percentages than those displayed under LED, indicating that LED accelerated surface discoloration compared to HFLO and FLO lights. Metmyoglobin (MMb) percentages increased over retail display, with LED-exposed steaks having greater (P < 0.05) percentages of MMb than those displayed in HFLO and FLO. By d 7 of retail display, HFLO-exposed steaks had lower (P < 0.05) MMb percentages than the steaks displayed in both FLO and LED. Lighting type did not influence (P > 0.05) lipid oxidation in SM steaks, however, lipid oxidation increased (P < 0.05) over retail display. The findings indicated that light source influenced the color stability in SM steaks during retail display and that HFLO light can minimize surface discoloration in moderate color stability beef muscles.

Intramuscular Variations in Color and Sarcoplasmic Proteome of Beef Semimembranosus during Postmortem Aging

Beef semimembranosus exhibits intramuscular difference in color stability, and the inside region (ISM) of the muscle is color-labile, whereas the outside region (OSM) is color-stable. Variations in sarcoplasmic proteins are known to contribute to this intramuscular color difference. Sarcoplasmic proteome and beef color are affected by postmortem aging. The objective of the present study was to examine the effect of aging on intramuscular color variations and the sarcoplasmic proteome of beef semimembranosus. Semimembranosus muscles obtained from 8 beef carcasses (n = 8) were subjected to aging at 2°C for 0, 7, 14, and 21 d. On each aging day, the muscles were fabricated into ISM and OSM steaks and allotted to refrigerated storage (2°C) under aerobic packaging. Instrumental color and metmyoglobin reducing activity were evaluated on d 0, 3, and 6 of storage. Samples frozen on d 0 and d 21 of aging were utilized for sarcoplasmic proteome analysis. Color attributes of both ISM and OSM steaks were influenced by aging, with steaks aged for 21 d having the lowest (P < 0.05) color stability. The ISM steaks had greater (P < 0.05) lightness than OSM counterparts, and the difference in lightness was not negated by aging. The ISM and OSM had similar (P > 0.05) redness on d 0 of storage, whereas ISM had lower (P < 0.05) redness compared to OSM on d 3 and d 6 of storage. Several proteins associated with glycolysis and energy metabolism were of greater abundance (P < 0.05) in OSM than in ISM after 21-d aging. Furthermore, the influence of 21-d aging on sarcoplasmic proteome was observed at a greater extent in OSM than in ISM, indicating that the effect of aging on sarcoplasmic proteome of beef semimembranosus was influenced by the location within the muscle.

Changes in the Sarcoplasmic Proteome of Beef Muscles with Differential Color Stability during Postmortem Aging

Beef color is a muscle-specific trait, and sarcoplasmic proteome influences muscle-specific variations in beef color stability. Postmortem aging influences the color and sarcoplasmic proteome of beef muscles. Nonetheless, muscle-specific changes in sarcoplasmic proteome of beef muscles with differential color stability during aging have not been characterized yet. Therefore, our objective was to examine the changes in the sarcoplasmic proteome of 3 differentially color stable muscles from beef hindquarters during postmortem aging. Longissimus lumborum (LL), psoas major (PM), and semitendinosus (ST) separated from 8 (n = 8) beef carcasses (24 h postmortem) were subjected to aging in vacuum packaging (2°C) for 0, 7, 14, and 21 d. On each aging day, steaks were fabricated, and allotted to refrigerated storage (2°C) under aerobic packaging. Samples for proteome analysis obtained during fabrication were frozen at –80°C. Instrumental color and metmyoglobin reducing activity were evaluated on d 0, 3, and 6 of storage. Sarcoplasmic proteome was analyzed, and differentially abundant proteins were identified using mass spectrometry. Color attributes and biochemical parameters were influenced by muscle source and aging (P < 0.05); LL and ST had greater (P < 0.05) surface redness than PM. Aging also influenced surface redness, with 7-d aged steaks demonstrating greatest values (P < 0.05). Proteome analysis identified 135 protein spots differentially abundant (P < 0.05) between the muscles and aging time points indicating muscle-specific changes during aging. The identified proteins included glycolytic enzymes, proteins associated with energy metabolism, antioxidant proteins, chaperones, and transport proteins. Overall, the glycolytic enzymes were more abundant (P < 0.05) in color-stable muscles and at aging times with greater color stability, indicating that these proteins could be used as potential biomarkers for beef color.

Exogenous and Endogenous Factors Influencing Color of Fresh Meat from Ungulates

Biochemistry of post-mortem muscle tissue is complex, and several factors affect the fresh meat color and color stability, both of which influence consumer acceptance. Therefore, improving meat color and meat color stability is of significant value to the meat industry and consumers. While extensive literature is available on the color and color stability of domestic ungulates, literature on wild ungulates is notably lacking. With an increasing global demand for meats from wild ungulates, it is critical to identify the knowledge gaps regarding their color and color stability. The objective of this paper is to overview the exogenous and endogenous factors influencing the color and color stability of fresh meats from domestic and wild ungulates. The literature highlighted that the pre- and post-harvest factors influencing meat color and meat color stability are interrelated and not mutually exclusive. Current research indicates that the effects of several of these factors are specific to species, breed, and muscle source. Novel ways to manipulate these factors using a biosystems approach should be explored to improve color attributes of fresh ungulate meats.

Light Source Influences Color Stability and Lipid Oxidation in Steaks from Low Color Stability Beef Triceps brachii Muscle

AbstractColor of retail fresh meat is one of the most important quality attributes affecting purchasing decisions for consumers. The objective of this study was to evaluate the impact of different light sources on surface color and lipid oxidation during retail display of fresh steaks from beef Triceps brachii (TB), a muscle with low color and lipid oxidative stabilities. Steaks (n = 12) from 20 TB muscles were overwrapped with oxygen-permeable polyvinyl chloride, and assigned to one of three lighting treatments, i.e., high UV fluorescent (HFLO), low UV fluorescent (FLO), and light emitting diode (LED), in temperature-controlled deli cases. Steaks were removed on retail display d 1, 3, 5, and 7 for evaluating instrumental color (L*, a*, and b* values), surface myoglobin redox forms, metmyoglobin reducing ability, and lipid oxidation. Surface redness (a* values) of TB steaks decreased (P < 0.05) during retail display. Light source influenced a* values, with HFLO-displayed steaks having higher (P < 0.05) a* values than steaks exposed to both FLO and LED light sources. Oxymyoglobin levels were higher (P < 0.05) for TB steaks displayed under HFLO lights than those displayed under FLO (on d 3 and 7) or LED (on d 5 and 7) lights. Steaks displayed under HFLO lights had lower (P < 0.05) metmyoglobin levels than those exposed to both FLO and LED lights on d 5 and 7. Lipid oxidation increased over retail display time, and on d 7 of retail display, steaks exposed to HFLO had less (P < 0.05) lipid oxidation than those displayed in FLO or LED. The results of the present study indicated that color stability and lipid oxidation in TB steaks during retail display are impacted by light source. The HFLO lighting may help to minimize surface discoloration and lipid oxidation in low color stability beef muscles.

Proteomic approach to characterize biochemistry of meat quality defects

Proteomics can be used to characterize quality defects including pale, soft, and exudative (PSE) meat (pork and poultry), woody broiler breast meat, reddish catfish fillets, meat toughness, and beef myoglobin oxidation. PSE broiler meat was characterized by 15 proteins that differed in abundance in comparison to normal broiler breast meat, and eight proteins were differentially expressed in woody breast meat in comparison to normal breast meat. Hemoglobin was the only protein that was differentially expressed between red and normal catfish fillets. However, inducing low oxygen and/or heat stress conditions to catfish fillets did not lead to the production of red fillets. Proteomic data provided information pertaining to the protein differences that exist in meat quality defects. However, these data need to be evaluated in conjunction with information pertaining to genetics, nutrition, environment of the live animal, muscle to meat conversion, meat quality analyses and sensory attributes to understand causality, protein biomarkers, and ultimately how to prevent quality defects.

Differential abundance of muscle proteome in cultured channel catfish (Ictalurus punctatus) subjected to ante-mortem stressors and its impact on fillet quality

The effects of environmental and handling stress during catfish (Ictalurus punctatus) aquaculture were evaluated to identify the biochemical alterations they induce in the muscle proteome and their impacts on fillet quality. Temperature (25°C and 33°C) and oxygen (~2.5mg/L [L] and >5mg/L [H]) were manipulated followed by sequential socking (S) and transport (T) stress to evaluate changes in quality when fish were subjected to handling (25-H-ST; temperature-oxygen-handling), oxygen stress (25-L-ST), temperature stress (33-H-ST) and severe stress (33-L-ST). Instrumental color and texture of fillets were evaluated, and muscle proteome profile was analyzed. Fillet redness, yellowness and chroma decreased, and hue angle increased in all treatments except temperature stress (33-H-ST). Alterations in texture compared to controls were observed when oxygen levels were held high. In general, changes in the abundance of structural proteins and those involved in protein regulation and energy metabolism were identified. Rearing under hypoxic conditions demonstrated a shift in metabolism to ketogenic pathways and a suppression of the stress-induced changes as the severity of the stress increased. Increased proteolytic activity observed through the down-regulation of various structural proteins could be responsible for the alterations in color and texture.

Proteome basis for intramuscular variation in color stability of beef semimembranosus

The objective of the present study was to characterize the proteome basis for intramuscular color stability variations in beef semimembranosus. Semimembranosus muscles from eight carcasses (n=8) were fabricated into 2.54-cm thick color-labile inside (ISM) and color-stable outside (OSM) steaks. One steak for sarcoplasmic proteome analysis was immediately frozen, whereas other steaks were allotted to retail display under aerobic packaging. Color attributes were evaluated instrumentally and biochemically on 0, 2, and 4days. Sarcoplasmic proteome was analyzed using two-dimensional electrophoresis and tandem mass spectrometry. ISM steaks demonstrated greater (P<0.01) abundance of glycolytic enzymes (fructose-bisphosphate aldolase A, phosphoglycerate mutase 2, and beta-enolase) and phosphatidylethanolamine-binding protein 1 than their OSM counterparts. Possible rapid post-mortem glycolysis in ISM, insinuated by over-abundance of glycolytic enzymes, could lead to rapid pH decline during early post-mortem, which in turn could potentially compromise its color stability. These results indicated that differential abundance of sarcoplasmic proteome contributes to intramuscular variations in beef color stability.