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.

Effects of beef carcass size, and subsequent aging time, on yield and color characteristics of top round steaks

Variation in cut size and weight of fabricated subprimals is a challengeof increased beef carcass weights. Subsequently, variation in carcass size hasresulted in consistency challenges during retail display. Theobjective of this study was to assess the retail shelf-life of commerciallyavailable top rounds from varying carcass weights. In the current study, 21industry average weight (AW, 340-409 kg; no industry discount) beef carcassesand 21 oversized (OS, exceeding 454 kg; receive a discount) beef carcasses wereevaluated. Carcasses were selected at a commercial beef packing plant, wherethe left and right (paired) top round subprimals of each carcass were procured.Paired top rounds were assigned to a short (8d), average (23d), or extended(42d) postmortem aging period. After wet-aging, subprimals were fabricated intosteaks for additional analysis. Steaks were evaluated as whole top round steaksor further fabricated into “superficial” and “deep” portions at 5.08 cm fromthe superficial edge of the Semimembranosus and the Adductor muscle.Top rounds and steaks from OS carcasses were larger (P &lt; 0.01) thanthose from AW carcasses. Quantitative color of the anatomically deep locationsof the OS steaks had the greatest mean L* (lightness; P &lt; 0.01), a*(redness; P &lt; 0.01) and b* (yellowness; P &lt; 0.01) values. Extendingthe aging timeline increased L* (lightness; P &lt; 0.01), decreased a*(redness; P &lt; 0.01), and decreased b* (yellowness; P &lt;0.01). Alternative top round steak fabrication which separates the deep andsuperficial anatomical locations could be an effective means of providing moreuniform steaks.&nbsp;

Influence of Ca2+ on mitochondrial apoptosis activation and yak meat tenderization during postmortem aging

The objective of this study was to investigate the underlying molecular mechanisms of mitochondrial Ca2+ homeostasis disequilibrium in mitochondrial apoptosis and its impact on yak meat tenderness. Results indicated that CaCl2 treatment significantly promoted glycolysis by increasing lactic acid level and decreasing glycogen content, pH, and ATP production (P < 0.01 and P < 0.05). The activities of Na+-K+-ATPase pump and Ca2+-ATPase pump in the early aging stage were significantly influenced by CaCl2 treatment. The activities of synchronous digital hierarchy and citrate synthase were also significantly improved by CaCl2 treatment (P < 0.01 and P < 0.05). Mitochondrial reactive oxygen species (ROS) levels were significantly higher in the CaCl2 group than in the control group (P < 0.01); at 24 h, the value in the Ca2+ group was 64.27% higher than that in the control group. Furthermore, CaCl2 treatment significantly enhanced the mitochondrial apoptosis cascade reaction and meat tenderization by improving the myofibril fragmentation index and shear force (P < 0.01). These results demonstrated that the imbalance of mitochondrial Ca2+ homeostasis played a significant role in the mitochondrial apoptosis pathway by regulating energy metabolism factors, meat intracellular environment, mitochondrial functions, and ROS-mediated oxidative stress. These conditions further improved meat tenderization during postmortem aging.

Can Tumbling without Brine Improve Tenderness and Proteolysis of Beef Loin Muscles?

Tumbling of intact muscle foods has been widely applied toprocessed meats using brine solution. However, the use of tumbling withoutbrine on fresh beef muscles has not been fully examined. Therefore, this studyaimed to evaluate fresh beef tumbling on meat quality and proteolytic featuresof loin (longissimus lumborum)muscles. Moreover, interactions with the duration of postmortem aging wereinvestigated. Loins (n=9) at 7d postmortem were sectioned and allocated among twotumbling (T) treatment groups at 60 (T60) or 90 (T90) minutes, as well as a non-tumbledcontrol (T0) group. After treatment, sub-sections were made and divided among0d, 7d, or 14d of further aging. Meat quality was assessed by shear forcevalues, water-holding ability, and color attributes. The extent of proteolysiswas determined by quantification of desmin and troponin-T, myofibrilfragmentation index (MFI), and transmission electron microscopy. An interactionbetween fresh beef tumbling and aging duration was observed in shear forcevalues (P=0.032). At 0d, muscles fromT90 exhibited lower shear force (21.6 N) compared to T0 (34.8 N) and T60 (24.7N) groups. Muscles from T60 and T90 groups maintained lower shear force than T0controls at each respective aging duration.Higher cooking loss (P=0.011) but notpurge loss (P=0.412) was observed in theT60 and T90 groups compared to T0. Shear force results were supported by higherMFI in T60 and T90 groups than T0 controls (P&lt;0.001), as well as the disappearance of intact troponin-T withfurther aging (P=0.009). Transmissionelectron microscopy supported increased initial tenderness would owe primarily tophysical disruptions to myofibrillar structure, though fresh beef tumbling may facilitateproteolysis with further aging.

Effects of extended postmortem aging and intramuscular location on protein degradation, muscle fiber morphometrics, and tenderness of beef longissimus lumborum and semitendinosus steaks

The objective of this study was to determine effects of extended aging and intramuscular location on Warner-Bratzler shear force (WBSF), muscle fiber cross-sectional area (CSA), and protein degradation of semitendinosus (ST) and longissimus lumborum (LL) steaks. Left ST and LL were removed from 40 carcasses at 6 d postmortem. The ST was fabricated into 5 locations (LOC), with LOC 1 being most proximal and LOC 5 being most distal. The posterior LL was fabricated into 3 LOC, with LOC 1 being most anterior. Vacuum sealed ST steaks were aged 7, 14, 28, 56, or 112 d postmortem, while LL steaks were aged 7, 28, or 112 d postmortem at 2 ± 1°C. A steak from each LOC was assigned to WBSF or laboratory analyses. There were no Day of Aging (DOA) × LOC interactions for all dependent variables (P &gt; 0.06). There were DOA effects for ST and LL WBSF values and degraded 38-kDa desmin (DES; P &lt; 0.01). Day-7 ST-steak WBSF value was greater than all other days (P &lt; 0.01) and d-14 steaks had greater WBSF value than remaining days (P &lt; 0.05). Day-28 ST-steak WBSF values were greater than d-56 and -112 (P &lt; 0.01), which did not differ (P = 0.53). In the LL, d-7 steaks had greater WBSF values than the other two timepoints (P &lt; 0.01) and d-28 steaks had greater (P &lt; 0.01) WBSF values than d-112 steaks. Degraded ST 38-kDa DES content was less on d 7 and 14 compared to all other days (P &lt; 0.03), but did not differ (P = 0.79) from each other. Days 28 and 56 38-kDa DES content was less than d 112 (P &lt; 0.01), but did not differ (P = 0.34) from each other. Degraded LL 38-kDa DES content was less on d 7 than d 28 and 112 (P &lt; 0.02), which did not differ (P = 0.67). There were LOC effects for only ST WBSF and muscle fiber CSA (P &lt; 0.05). Semitendinosus steak LOC 1 and 2 had greater WBSF values than all other locations (P &lt; 0.01), but did not differ (P = 0.32) from each other. Semitendinosus steak LOC 3 and 5 had greater WBSF values than LOC 4 (P &lt; 0.01), but did not differ (P = 0.85) from each other. The CSA of all ST fiber types were largest in LOC 1 compared to all other fiber types (P &lt; 0.01). The CSA of all LOC 2 and 3 fiber types was greater than LOC 4 and 5 (P &lt; 0.01), but were not different from each other (P &gt; 0.81), and LOC 4 had greater CSA than LOC 5 (P &lt; 0.01). Steak aging WBSF value improvements seemed proteolysis catalyzed, while the ST intramuscular tenderness gradient was more likely due to muscle fiber CSA.

Determining the longissimus lumborum and psoas major beef steak color life threshold and effect of post-mortem aging time using meta-analysis

longissimuslumborum (LL) and psoas major (PM) steaks duringretail display and the effect of postmortem aging time (PMT) on the displaycolor life of LL and PM steaks using meta-analysis was determined. In phaseone, data were retrieved from 13 and 3 referred journal articles, for LL andPM, respectively, that included a* and subjective visual scores. The total display dayobservations for LL and PM were 148 and 27, respectively. Lower bound estimatesusing a 95% confidence interval for a* as a borderline for the display colorlife of LL and PM steaks were 20.24 and 20.99, respectively. For phase two, datawere retrieved from 26 and 10 referred journal articles, for LL and PM,respectively, that included a* and PMT. The total display dayobservations for LL and PM in phase two were 255 and 71, respectively. For LLsteaks, the actual PMT was grouped into five categories: 0-7 d; 8-14 d; 15-21d; 22-28 d; and 29-65 d. Additionally, the PMT of PM steaks was grouped intotwo categories: 0-7 d and 8-21 d. The first 21 d PMT for LL steaks had thelongest color life with 7 d of color life. Additionally, 22-28 and 29-65 d ofPMT had 5 and 4 d, respectively, of color life for LL steaks. The borderlineacceptability estimated for PM steaks with 0-7 d and 8-21 of PMT was 3 and 2 dof color life, respectively. Estimations from this meta-analysis demonstrate that usingLL and PM subprimals having a PMT of 21 d or less and 7 d or less, respectively,would optimize retail display color life of aerobically packaged steaks.&nbsp;

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

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

Utilizing Pork Exudate Metabolomics to Reveal the Impact of Aging on Meat Quality

This study was performed to assess the changes in meat quality and metabolome profiles of meat exudate during postmortem aging. At 24 h postmortem, longissimus lumborum muscles were collected from 10 pork carcasses, cut into three sections, and randomly assigned to three aging period groups (2, 9, and 16 d). Meat quality and chemical analyses, along with the metabolomics of meat exudates using ultra-high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer (UHPLC-QTOF-MS) platform, were conducted. Results indicated a declined (p < 0.05) display color stability, and increased (p < 0.05) purge loss, meat tenderness, and lipid oxidation as aging extended. The principal component analysis and hierarchical clustering analysis exhibited distinct clusters of the exudate metabolome of each aging treatment. A total of 39 significantly changed features were tentatively identified via matching them to METLIN database according to their MS/MS information. Some of those features are associated with adenosine triphosphate metabolism (creatine and hypoxanthine), antioxidation (oxidized glutathione and carnosine), and proteolysis (dipeptides and tripeptides). The findings provide valuable information that reflects the meat quality’s attributes and could be used as a source of potential biomarkers for predicting aging times and meat quality changes.