Endpoint Temperature Influences Sarcoplasmic Proteome Profile of Cooked Beef Longissimus Lumborum

ObjectivesCooking ensures safety and enhances the palatability attributes of meat. Denaturation of myoglobin results in the dull-brown color of cooked meats. The denaturation of sarcoplasmic proteins is influenced by the degree of heat treatment, and their solubility is decreased with an increase in the endpoint cooking temperature. While previous studies examined the relationship between myoglobin denaturation, cooked color, and internal temperature in beef, investigations are yet to be undertaken to characterize the association between endpoint temperature, sarcoplasmic proteome, and color attributes in cooked steaks. Therefore, the objective of the present study was to examine the influence of endpoint cooking temperature (60 and 71°C) on sarcoplasmic proteome and internal color of beef longissimus lumborum (LL) steaks.Materials and MethodsEight (n = 8) beef LL muscles (14 d postmortem; USDA Choice) were obtained from a commercial packing plant. Two 2.5-cm thick steaks were fabricated from the center of the muscles and were cooked to internal endpoint temperature of 60°C (C-60) or 71°C (C-71) in a clam-shell grill. Cooked steaks were immediately cooled in slushed ice, sliced parallel to the grilled surface, and internal redness (a* value) and color stability (R630/580) were evaluated instrumentally. Sarcoplasmic proteome from the interiors of the cooked steaks was analyzed using 2-dimensional electrophoresis, and the gel images were digitally analyzed. The protein spots exhibiting more than 2.5-fold intensity differences (P < 0.05) between C-60 and C-71 were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry.ResultsThe C-60 steaks demonstrated greater (P < 0.05) a* and R630/580 than their C-71 counterparts. Seven differentially abundant proteins were identified and were over-abundant (P < 0.05) in C-60 compared to C-71. The differentially abundant proteins belong to 6 functional groups, i.e., transport proteins (serum albumin and hemoglobin), energy metabolism (adenylate kinase isoenzyme 1), chaperones (heat shock protein β-1), antioxidant (thioredoxin-dependent peroxide reductase), glycolytic enzymes (fructose-bisphosphate aldolase B), and protease (cytosol aminopeptidase).ConclusionThe findings indicated that the endpoint cooking temperature influences the internal cooked color and the sarcoplasmic proteome profile of beef LL steaks. The overabundant proteins in steaks cooked to 60°C may be utilized as potential biomarkers for undercooked beef, which is a source for foodborne infections.

Aging Influences Shear Force of Beef in a Muscle-Specific Manner

ObjectivesTenderness is an important sensory attribute that influences consumers’ overall eating satisfaction and repurchase decisions of beef. However, beef tenderness is a muscle-specific and highly variable trait, with different muscles from the same carcass exhibiting considerable variations. Retailing single-muscle beef cuts, based on quality and palatability traits, can improve value of carcasses. Postmortem wet aging of beef subprimals under vacuum packaging is a widely used industry practice in the U.S. to improve beef tenderness. Although beef muscles differ in their biochemical attributes, different muscles undergo similar aging procedure because wet aging is generally preformed on the subprimals. While beef muscles may respond differentially to wet aging, the effects of aging time on tenderness of three economically important beef hindquarter muscles, i.e., longissimus lumborum (LL), psoas major (PM), and semitendinosus (ST), are yet to be examined. Therefore, the objective of the current study was to examine the effect of aging on tenderness of beef LL, PM, and ST muscles.Materials and MethodsThe LL, PM, and ST muscles were excised (24 h postmortem) from both sides of eight (n = 8) beef carcasses (USDA Choice; A maturity) and was further separated into two equal-length sections, resulting in four muscle sections per carcass. The muscle sections were vacuum packaged and randomly assigned to aging at 2°C for either 0, 7, 14, or 21 d. At the end of each aging period, 2.5-cm steaks were fabricated. The steaks were cooked to an internal temperature of 71°C and chilled to 4°C overnight. Six cylindrical cores (1.27-cm of diameter) parallel to the muscle fiber orientation were obtained from each steak with a hand-held coring device. Shear force was determined by shearing each core with V-shaped blade of Warner-Bratzler shear device, and the values were recorded as the peak force (N). The main effects of muscle source and aging days, and their interactions were analyzed using the Mixed Procedure of SAS. The least square means for protected F-tests (P < 0.05) were separated by using least significant differences and were considered significant at P < 0.05.ResultsMuscle source and aging days influenced (P < 0.05) the tenderness, with an improvement (P < 0.05) in tenderness observed with aging. Moreover, a muscle × aging day interaction (P < 0.05) was observed for tenderness. Shear force of LL decreased (P < 0.05) with aging, although there was no difference (P > 0.05) in tenderness between 7 and 14-d aged LL. However, aging beyond 7 d did not improve (P > 0.05) the tenderness of already tender PM steaks. On the other hand, improvement (P < 0.05) in tenderness was observed in ST until 14 d. After 21 d of aging, LL was the most tender, while ST remained the toughest (P < 0.05).ConclusionThe results indicated that different muscles in beef hindquarters responded differentially to postmortem aging, and the processors could optimize aging time depending on the muscles to improve beef tenderness.

Supranutritional Supplementation of Vitamin E Influences the Abundance of Antioxidant Proteins in Postmortem Longissimus Lumborum from Heifers

ObjectivesVitamin E is a lipid-soluble antioxidant that can inhibit lipid oxidation and improve beef color stability. The effect of vitamin E on fresh beef color, from the standpoint of lipid oxidation-induced myoglobin oxidation, have been extensively studied. However, the influence of vitamin E on sarcoplasmic proteome profile of beef skeletal muscles is yet to be investigated. Therefore, the objective of this study was to examine the effect of dietary vitamin E on sarcoplasmic proteome of postmortem beef longissimus lumborum (LL) muscle.Materials and MethodsCrossbred heifers, managed with a GrowSafe feeding system, were fed ad libitum corn-based diet containing either no supplemental (CONT) or 1000 IU vitamin E/heifer per day (VITE) for 89 d. The animals were harvested, and carcasses were chilled. The LL muscle samples were obtained from the carcasses of nine (n = 9) VITE and nine (n = 9) CONT heifers 24 h postmortem. The muscle samples were individually vacuum-packaged and frozen at –80°C for proteome analysis. Sarcoplasmic proteome was analyzed using two-dimensional electrophoresis, employing immobilized pH gradient strips (pH 3–10; 17 cm) in the first dimension and 12% sodium dodecyl sulfate polyacrylamide gel electrophoresis in the second dimension. The gels were scanned, and the digital gel images were analyzed. The protein spots exhibiting more than 1.5-fold intensity differences (P < 0.10) between VITE and CONT were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry.ResultsFive differentially abundant spots were identified using mass spectrometry, and all the spots were over-abundant in CONT. The proteins in the differentially abundant spots were antioxidant proteins (thioredoxin-dependent peroxide reductase, peroxiredoxin-6, and serum albumin) and glycolytic enzymes (β-enolase and triosephosphate isomerase). The antioxidant proteins minimize oxidation of lipids and proteins in muscle matrix, whereas the glycolytic enzymes generate NADPH, which helps maintain the antioxidant proteins in their reduced forms.ConclusionThe strong antioxidant protection offered by vitamin E could have possibly led to less expression of antioxidant proteins as well as glycolytic enzymes that generate antioxidant metabolites in the VITE group, whereas the lack of such protection in CONT group may have led to increased expression of these proteins in the skeletal muscles.

Ractopamine-Induced Changes in the Mitochondrial Proteome of Postmortem Beef Longissimus Lumborum

ObjectivesRactopamine is a β-adrenergic agonist approved as growth promotant in beef cattle, and it increases muscle deposition while limiting fat deposition. Dietary ractopamine causes a muscle fiber shift in cattle, and the biochemistry of mitochondria in postmortem beef skeletal muscles is influenced by fiber type. Therefore, dietary ractopamine may potentially affect mitochondrial functionality. Nonetheless, the influence of ractopamine on beef skeletal muscle mitochondrial proteome has not been evaluated. Therefore, the objective of this study was to examine the effects of ractopamine on mitochondrial proteome of postmortem longissimus lumborum (LL) from beef cattle.Materials and MethodsPen-housed crossbred steers were fed either a corn-based basal diet (CON) or a diet top-dressed with Optaflexx 45 (Elanco Animal Health) to provide 400 mg of ractopamine hydrochloride/steer per day (RAC). Ractopamine was fed the last 28 d prior to the harvest. The animals were harvested, and carcasses were chilled for 24 h. The LL muscle samples were obtained from nine (n = 9) RAC and nine (n = 9) CON carcasses. Mitochondrial proteome was analyzed using two-dimensional electrophoresis, and the digital gel images were analyzed. The protein spots exhibiting more than 1.5-fold intensity differences (P < 0.10) between RAC and CON were subjected to in-gel tryptic digestion and were identified by tandem mass spectrometry.ResultsSeven differentially abundant proteins were identified in the mitochondrial proteome. Three proteins were over-abundant (P < 0.10) in RAC, whereas four spots were over-abundant in CON. The proteins over-abundant in RAC mitochondrial proteome was complement component 1 Q subcomponent-binding protein, very long-chain specific acyl-CoA dehydrogenase, and aconitate hydratase. On the other hand, ATP synthase subunit β, prohibitin, Cytochrome b-c1 complex subunit, and thioredoxin-dependent peroxide reductase were over-abundant in CON samples. The differentially abundant proteins belong to four functional groups; i.e., energy metabolism (ATP synthase subunit β, Cytochrome b-c1 complex subunit 1, and aconitate hydratase), chaperone activity (complement component 1 Q subcomponent-binding protein and prohibitin), antioxidant activity (thioredoxin-dependent peroxide reductase), and lipid metabolism (very long-chain specific acyl-CoA dehydrogenase).ConclusionDietary ractopamine impacts mitochondrial proteome in postmortem beef LL muscle and influences the abundance of proteins involved in cellular metabolism and protective mechanisms. The increased protein synthesis and leanness previously reported in ractopamine-fed cattle may be attributed to the decreased expression of enzymes involved in respiratory electron transport pathways and the increased expression of enzymes involved in lipolysis.

Quantitative Proteomic Characterization Associated with Woody Breast Meat from Broilers Fed a Standard or an Amino Acid-Reduced Diet

ObjectivesWoody or wooden breast (WB) is an emergent myopathy of broilers and is macroscopically characterized by hardened areas of the Pectoralis major muscle. Woody broiler breast fillets can result in harder texture, higher pH, lower amounts of proteins, lower water-holding capacity, and increased cook loss when compared to normal breasts. The impaired meat quality of WB has been reported to be closely associated with improved nutrition and fast-growth rates. The present research compared the proteome of normal and woody breast muscle from broilers that were fed with either a control diet or an amino acid (AA)-reduced diet.Materials and MethodsMixed-sex broilers were assigned to 16 pens (15 chicks per pen) and fed with control or reduced AA diets (20% reduction of digestible lysine, total sulfur amino acids, and threonine). At 8 wk of age, live broilers were evaluated manually for WB myopathy. Within each diet group, 4 male broilers with normal breast and 4 male broilers with WB were selected (one bird in each pen) and euthanized using CO2 gas. The breast muscle from the cranial portion was immediately sampled after bleeding and snap-frozen in liquid nitrogen. All experimental procedures were approved by the Institutional Animal Care and Use Committee of Mississippi State University (IACUC-16-542). Whole muscle proteins of normal and woody breast were extracted from frozen samples of three birds within each treatment. Two-dimensional gel electrophoresis (2-DE; 6 gels per treatment) coupled with image analysis and mass spectrometry were used to investigate differences in the expression levels of proteins (more than 2.0-fold intensity differences) from chicken breast muscle. Differences were evaluated using Student’s t test at a confidence interval of 95%.ResultsWhen the broilers were fed with the control diet, 10 proteins were expressed differentially between normal and woody breasts. Apolipoprotein A-I, desmin, annexin A2, annexin A5, and ubiquitin carboxyl-terminal hydrolase were overexpressed (P < 0.05) in WB. Peptidyl-prolyl cis-trans isomerase, four and a half LIM domains protein 1 isoform X3, and an uncharacterized protein were only present in WB muscle, but not in normal chicken breast. Two proteins, keratin, type II cytoskeletal 8 and α-1,4 glucan phosphorylase, were overexpressed (P < 0.05) in normal chicken breast. These differentially expressed proteins were involved in glycolytic metabolism, cell structure, and cellular defense.Interestingly, only one protein (heat shock protein β-1) was expressed differentially between normal and woody breasts when broilers were fed with the AA-reduced diet. This protein was overexpressed (P < 0.05) in WB samples and found to play a role in stress resistance and actin organization.ConclusionThe protein profiles of normal and woody chicken breast samples were different, which might help explain the changes in meat quality. Essential amino acid intake resulted in minimizing difference in protein profiles between normal and woody chicken breasts.

Thermal Stability of Beef Myoglobin is Compromised by Reactive Lipid Oxidation Products

ObjectivesBrown color of cooked meat is the result of heat-induced denaturation of myoglobin (Mb). The denaturation temperature of Mb is governed by its redox state in raw meat; metmyoglobin (MMb) undergoes denaturation at a lower temperature than oxymyoglobin (OMb) and deoxymyoglobin (DMb). The secondary products of lipid oxidation, such as the 4-hydroxy-2-nonenal (HNE), compromise Mb redox stability and can thus impact cooked meat color. While previous investigations extensively studied lipid oxidation-induced Mb redox instability, studies are yet to be undertaken to examine the relationship between lipid oxidation and Mb thermal stability. Therefore, the objective of the present study was to investigate the direct influence of lipid oxidation (using HNE as a model aldehyde) on thermal stability of beef Mb at typical meat conditions.Materials and MethodsBeef Mb was purified, and OMb was incubated with HNE (0.15 mM Mb + 1.0 mM HNE) at pH 5.6 and 4°C for 21 d. The controls consisted of OMb plus a volume of ethanol used to deliver HNE to treatments. The samples were scanned spectrophotometrically from 650 to 500 nm on d 0, 7, 14, and 21, and MMb formation was calculated. The Mb samples were removed on d 0, 7, 14, and 21, and were digested with trypsin. The tryptic peptides were analyzed using liquid chromatography tandem-mass spectrometry (LC-MS/MS) for detecting HNE adduction sites. The thermal stability of Mb in the presence of HNE was assessed on d 0, 7, 14, and 21 by determining the percentage myoglobin denaturation (PMD) at 71°C in a water bath for 10 min. The experiment was replicated three times (n = 3). The effects of HNE on Mb redox and thermal stabilities during incubation were evaluated using the mixed procedure of SAS. The differences among means were detected at the 5% level using the least significant difference (LSD) test.ResultsWhile MMb formation increased (P < 0.05) during the storage in both control and HNE-treated samples, the oxidation was higher (P < 0.05) in HNE-treated samples. The PMD values increased (P < 0.05) in both treatments during the storage, and the HNE-treated samples exhibited greater (P < 0.05) PMD than the controls throughout the storage. Additionally, the PMD difference between HNE-treated and control samples increased over time. The LC-MS/MS analyses indicated that the number of histidines adducted by HNE increased with storage. HNE adducted four histidines (positions 24, 36, 93, and 152) on d 7, whereas five (positions 24, 36, 64, 93, and 152) and six (positions 24, 36, 64, 93, 113, and 152) residues were adducted on d 14 and 21, respectively.ConclusionThe mass spectrometric data indicated that thermal stability of beef Mb was compromised by reactive lipid oxidation products. The HNE adduction at the distal histidine (position 64), which is critical to heme stability, observed on d 14 and 21 as well as the increased number of histidines adducted by HNE on d 14 and 21 could be the possible reasons for the increased PMD on these time points. The adduction of HNE to histidines can alter the heme protein’s tertiary structure and thus exposes the heme to oxidation, thereby accelerating the formation of MMb, which is more susceptible to thermal denaturation than the ferrous Mb redox forms.

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.

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.

Bovine mitochondrial oxygen consumption effects on oxymyoglobin in the presence of lactate as a substrate for respiration

Research suggests that NADH formed from lactate addition can increase mitochondrial oxygen consumption. However, limited research has assessed the subsequent effects of lactate-mediated mitochondrial oxygen consumption on oxymyoglobin. Therefore, our objective was to assess the effects of bovine mitochondrial oxygen consumption on oxymyoglobin in the presence of lactate, LDH, and NAD. Isolated beef cardiac and skeletal muscle mitochondria (n=5) were reacted with lactate (40 mM), LDH (100 units), and NAD (0.02 mM) to initiate oxygen consumption. Myoglobin redox state was measured to assess the effects of oxygen consumption on oxymyoglobin. The addition of lactate-LDH-NAD to mitochondria increased (p<0.05) both oxygen consumption and conversion of oxymyoglobin to deoxymyoglobin compared with control mitochondria without substrates. The addition of antimycin A to mitochondria decreased oxygen consumption and deoxymyoglobin formation (p<0.05). The results suggest that increased oxygen consumption can influence myoglobin redox state and this effect might be partially responsible for the darkening effect in lactate enhanced beef.

Effects of 4-hydroxy-2-nonenal on beef heart mitochondrial ultrastructure, oxygen consumption, and metmyoglobin reduction

The effects of 4-hydroxy-2-nonenal (HNE) on mitochondria isolated from bovine hearts (n=5) were assessed using ultrastructure, oxygen consumption, membrane permeability, HNE binding, and metmyoglobin reduction in vitro. Pre-incubation (pH 5.6 and 7.4 at 25°C) of mitochondria with HNE decreased oxygen consumption compared with samples without HNE (P<0.05). Electron microscopy revealed that HNE-treated mitochondria were swollen and had increased membrane permeability at pH 7.4, compared with ethanol controls. Conversely, mitochondria incubated with HNE at pH 5.6 had decreased volume and permeability. Fluorescence studies indicate that HNE binds to the membrane of mitochondria isolated from bovine cardiac muscle (at pH 5.6 and 7.4). HNE-treated mitochondria at both pH 5.6 and 7.4 had lower metmyoglobin reduction and NADH dependent metmyoglobin reductase activity compared with control mitochondria without HNE (P<0.05). In addition to covalent binding with myoglobin, HNE may influence beef color stability by interacting with mitochondria.

Characterization of bison (Bison bison) myoglobin

Bison is an alternate meat species gaining increased popularity in North America. Although previous investigations reported that bison meat discolors faster than beef, the molecular basis of this observation has not been investigated. Therefore, the objective of the present study was to determine the redox stability, thermostability, and primary structure of bison myoglobin (Mb), in comparison with beef Mb. Purified bison and beef myoglobins were analyzed for autoxidation, lipid oxidation-induced oxidation, and thermostability. Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry was utilized for determining the exact molecular mass of bison Mb, whereas Edman degradation was employed to determine the amino acid sequence. Bison and beef myoglobins behaved similarly in autoxidation, lipid oxidation-induced oxidation, and thermostability. The observed molecular mass of bison and beef myoglobins was 16,949 Da, and the primary structure of bison Mb shared 100% similarity with beef and yak myoglobins. Noticeably, the amino acid sequence of bison Mb was different from other ruminant myoglobins, such as water-buffalo, sheep, goat, and red-deer. The present study is the first to report the primary structure of bison Mb. Same primary structure and similar biochemical attributes of bison and beef myoglobins suggested that the observed rapid discoloration in bison meat could not be attributed to biochemistry of bison Mb.

Primary structure of goat myoglobin

Color stability attributes of goat meat are different from those of sheep meat, possibly due to species-specific differences in myoglobin (Mb) biochemistry. An examination of post-genomic era protein databases revealed that the primary structure of goat Mb has not been determined. Therefore, our objective was to characterize the primary structure of goat Mb. Goat Mb was isolated from cardiac muscles employing ammonium sulfate precipitation and gel-filtration chromatography, and Edman degradation was utilized to determine the amino acid sequence. Sequence analyses of intact Mb as well as tryptic- and cyanogen bromide-peptides yielded the complete primary structure of goat Mb, which shared 98.7% similarity with sheep Mb. Similar to other livestock myoglobins goat Mb has 153 residues. Comparison of the sequences of goat and sheep myoglobins revealed two amino acid substitutions - THRgoat8GLNsheep and GLYgoat52GLUsheep. Goat Mb contains 12 histidine residues. As observed in other meat-producing livestock species, distal and proximal histidines, responsible for stabilizing the heme group and coordinating oxygen-binding, are conserved in goat Mb.