Pulmonary hypertension is a noninfectious disease of cattle at altitudes > 1524 m (5,000 ft). Mean pulmonary arterial pressures (PAP) are used as an indicator for pulmonary hypertension in cattle. High PAP cattle (≥ 50 mmHg) entering the feedlot at moderate elevations have lower feed efficiency as compared to low PAP cattle (< 50 mmHg). The impact of pulmonary arterial pressure on mitochondrial function, oxidative phosphorylation (OXPHOS) protein abundance, and meat color was examined using longissimus lumborum (LL) from high (98 ± 13 mmHg; n = 5) and low (41 ± 3 mmHg; n = 6) PAP fattened Angus steers (live weight of 588 ± 38 kg) during early postmortem period (2 h and 48 h) and retail display (day 1 to 9), respectively. High PAP muscle had greater (P = 0.013) OXPHOS-linked respiration and proton leak-associated respiration than low PAP muscles at 2 h postmortem but rapidly declined to be similar (P = 0.145) to low PAP muscle by 48 h postmortem. OXPHOS protein expression was higher (P = 0.045) in low PAP than high PAP muscle. During retail display, redness, chroma, hue, ratio of reflectance at 630 nm and 580 nm, and metmyoglobin reducing activity decreased faster (P < 0.05) in high PAP steaks than low PAP. Lipid oxidation significantly increased (P < 0.05) in high PAP steaks but not (P > 0.05) in low PAP. The results indicated that high PAP caused a lower OXPHOS efficiency and a greater fuel oxidation rates under conditions of low ATP demand in premortem beef LL muscle, this could explain the lower feed efficiency in high PAP feedlot cattle compared to low PAP counterparts. Mitochondrial integral function (membrane integrity or/and protein function) declined faster in high PAP than low PAP muscle at early postmortem. LL steaks from high PAP animals had lower color stability than those from the low PAP animals during simulated retail display, which could be partially attributed to the loss of muscle mitochondrial function at early postmortem by ROS damage in high PAP muscle. Pulmonary arterial hypertension could also decrease type I/type II muscle fiber ratio in skeletal muscle, which needs to be investigated further.

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

Rapid evaporative ionization mass spectrometry (REIMS) is a novel technique that provides rapid chemical information on biological tissues and has the potential to predict beef quality attributes in real time. This study aims to assess the ability of analysis by REIMS coupled with chemometric modeling to predict the quality attributes of wet-aged beef at the grading time. USDA Select and upper two-thirds Choice (n=42, N=84) striploins (longissimus lumborum [LL]) and tenderloins (psoas major [PM]) were collected 36 h postmortem from a commercial beef abattoir. The LL and PM were cut into portions and aged for 3, 14, and 28 d. Aged samples were analyzed for slice shear force,Warner-Bratzler shear force (WBS), and trained sensory panels (tenderness, juiciness, and flavor attributes), and results were used to categorize both LL and PM into binary classes. Additionally, slivers of the longissimus dorsi muscle between the 12th and 13th rib were collected during grading (36 h postmortem) and analyzed using REIMS. The REIMS data were used to build predictive models for tenderness, juiciness, and flavor classes for the 3 aging periods and 2 muscles. Prediction accuracies of all models were higher than classifying the samples by chance (P0.05). However, model accuracies were not too high, which could be due to overlaps between classes, small sample sizes, and unbalanced data, which could negatively affect predictive models. Results demonstrated that the chemical finger-prints obtained with REIMS could potentially sort carcasses by flavor, juiciness, and tenderness in real time. However, the full realization of this approach will require an increased sample size and the development of a sampling method that allows improved separation between sensory classes.

Fresh pork tenderness contributes to consumer satisfaction with the eating experience. Postmortem proteolysis of proteins within and between myofibrils has been closely linked with pork tenderness development. A clear understanding of the molecular features associated with pork tenderness development will provide additional targets and open the door to new solutions to improve and make pork tenderness development more consistent. Therefore, the objective was to utilize liquid chromatography and mass spectrometry with tandem mass tag (TMT) multiplexing to evaluate myofibrillar sub-proteome differences between pork chops of different instrumental star probe values. Pork loins (N = 120) were collected from a commercial harvest facility at 24 h postmortem. Quality and sensory attributes were evaluated at 24 h postmortem and after approximately 2 weeks of postmortem aging. Pork chops were grouped into 4 groups based on instrumental star probe value (Group A, $x¯$ = 4.23 kg, 3.43–4.55 kg; Group B, $x¯$ = 4.79 kg, 4.66–5.00 kg; Group C, $x¯$ = 5.43 kg, 5.20–5.64 kg; Group D, $x¯$ = 6.21 kg, 5.70–7.41 kg; n = 25 per group). Myofibrillar proteins from the samples aged approximately 2 weeks were fractionated, washed, and solubilized in 8.3 M urea, 2 M thiourea, and 1% dithiothreitol. Proteins were digested with trypsin, labeled with 11-plex isobaric TMT reagents, and identified and quantified using a Q-Exactive Mass Spectrometer. Between Groups A and D, 54 protein groups were differentially abundant (Adjusted P < 0.05). Group A had a greater abundance of proteins related to the thick and thin filament and a lesser abundance of Z-line-associated proteins and metabolic enzymes than Group D chops. These data highlight that distinct myofibrillar sub-proteomes are associated with pork chops of different tenderness values. Future research should evaluate changes immediately and earlier postmortem to further elucidate myofibrillar sub-proteome differences over the postmortem aging period.

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

Bovine longissimus lumborum (LL) and psoas major (PM) muscles biopsy samples were collected from four carcasses (n = 4) at 45 min, 12 h, and 36 h postmortem from a commercial beef processing facility. Proteins present in the early postmortem LL and PM proteomes were identified and quantified using tandem mass tag (TMT) labelled, fractionated peptides coupled to liquid chromatography tandem mass spectrometry (LC-MS/MS). The data are supplied in this article and are related to “Tandem mass tag labeling to characterize muscle-specific proteome changes in beef during early postmortem period” by Zhai et al. [1].