Postmortem Meat Research Articles

Ante-mortem glutathione peroxidase 4 inhibition by RSL3 affects post-mortem meat quality in broiler chickens

ABSTRACT 1. This study investigated the role of glutathione peroxidase 4 (GPX4), a key regulator of ferroptosis, a form of programmed cell death, in muscle biochemistry and meat quality, utilising broiler chickens whose ante-mortem GPX4 activity was inhibited pharmacologically. 2. Male broilers were divided into two groups, each receiving ante-mortem administration of the GPX4 inhibitor, Ras-selective lethal 3 (RSL3), or a vehicle only. After slaughter, breast muscles were collected and stored for 48 h. The expressions of ferroptosis-related genes, glutathione levels, pH, colour and water-holding capacity were evaluated at multiple time points during the storage period. 3. The RSL3 treatment decreased the expression of GPX4 and ferritin heavy chain 1, which are negative regulators of ferroptosis, while it increased the expression of a ferroptosis accelerator, acyl-CoA synthetase long chain family member 4. The ratio of reduced to oxidised glutathione was significantly decreased in the RSL3 group. The RSL3 treatment decelerated post-mortem pH decline and colour changes, such as a decrease in L* and an increase in a* were observed in the RSL3 group. In addition, the RSL3 group showed increased levels of water-holding capacity. 4. These findings suggested that ante-mortem GPX4 activity plays a role in determining meat quality, implying the possible involvement of ferroptosis in the mechanism by which skeletal muscle is converted after slaughter into meat that is eaten.

The correlation between Smac, IAPs and mitochondrial apoptosis, muscle tenderness during postmortem aging of Oula Tibetan sheep meat

Oula Tibetan sheep meat has rich nutritional value but relatively poor tenderness. Recently, apoptosis of muscle cells has gradually become a research hotspot for improving meat tenderness during postmortem aging. Smac can promote the decrease of IAPs expression in tumor cells, thereby inducing mitochondrial apoptosis. However, the relationship between Smac, IAPs and mitochondrial apoptosis, muscle tenderness during postmortem meat aging is still unclear. Thus, the aim of this work was to explore the relationship between Smac, IAPs and mitochondrial apoptosis as well as muscle tenderness during postmortem meat aging. Smac concentration, IAPs concentration, pH value, ATP content, SDH activity, MPTP opening degree, MMP, caspase-3/9 activity, apoptotic rate, MFI and shear force value of Oula Tibetan sheep meat were measured at different aging times and correlation analysis was performed. Correlation analysis revealed that Smac, IAPs were markedly related to mitochondrial apoptosis and muscle tenderness during postmortem aging of Tibetan sheep meat. The results suggest that Smac may regulate IAPs to promote mitochondrial apoptosis and muscle tenderization in Oula Tibetan sheep meat during postmortem aging.

Muscle Proteins, Technological Properties, and Free Amino Acids of Epaxial Muscle Collected from Asian Seabass (Lates calcarifer) at Different Postmortem Durations

The aim of this study was to compare the changes in the epaxial muscle proteins of Asian seabass at two different postmortem durations. The epaxial muscles of Asian seabass were collected 1 h or 24 h postmortem (PM). Whole, ungutted fish were stored in an ice box, with the ice refilled every two hours. The results show significant increases in the MFI values and the contents of solubilized sarcoplasmic proteins, with a molecular weight of proteins of 47 kDa in the 24 h PM samples (p < 0.05). Myofibrillar and alkaline-soluble proteins in the epaxial muscle remained intact 24 h postmortem. Compared with the 1 h PM samples, the 24 h PM meat exhibited lower degrees of expressible water and hardness (p < 0.05), indicating superior water-holding capacity and meat tenderness. However, no differences in springiness or cohesiveness of the cooked meat were observed. Free L-glutamic acid, known as an umami-tasting amino acid, was significantly increased upon the extension of postmortem duration, and its level was above the taste threshold concentration. Overall, the findings indicated that the 24 h PM epaxial muscle of Asian seabass exhibited superior technological properties, along with higher contents of taste-related amino acids.

Unveils key proteins in Xinjiang goat muscle linked to post-mortem meat quality: A TMT-based proteomic analysis

An extensive proteomic analysis utilizing the tandem mass tag (TMT) method was conducted to investigate the changes in protein expression in the longissimus dorsi muscle of Xinjiang goats over various post-mortem intervals: immediately after death within 0 h, 12 h, 24 h and 48 h. The investigation carefully identified around 108 proteins that showed significant changes in expression during these intervals. Among these proteins, six were highlighted for their crucial roles in muscle growth and differentiation of muscle fibers post-mortem. These proteins, namely COL12A1, MRPL46, CTNNB1, MYH1, CAPZA1, and MYL9, have a direct effect on the meat's quality attributes, such as tenderness and color. Further discuss observed a progressive increase in the expression of proteins linked with oxidative metabolism (MSRB2, ENOX1, LOC102170282, GSTM1, and AOC3) as the post-mortem aging period extended, particularly between 24 h to 48 h. These proteins are instrumental in defining the color and flavor profiles of goat meat, underscoring the importance of precise processing and storage conditions to preserve meat quality during the critical aging phase. This enhanced understanding of protein expression dynamics offers significant implications for optimizing meat quality and provides a scientific basis for post-mortem handling practices in the goat meat industry.

Role of Heat-Shock Proteins in the Determination of Postmortem Metabolism and Meat Quality Development of DFD Meat.

This research explored the potential role of various heat-shock proteins (HSPs) in the determination of postmortem metabolism and the development of meat quality of normal, atypical DFD, and typical DFD beef. Beef longissimus thoracis muscle samples were classified into normal, atypical DFD, and typical DFD beef. The HSP27, HSP70, and HSP90 levels, meat quality parameters, and glycolytic metabolites were tested. The results showed that color coordinates (L*, a*, and b*), glycogen, and lactate contents were lower, whereas water-holding capacity was higher in the typical DFD beef than in the normal and atypical DFD beef (p < 0.05). The expression of HSP27 on day 1 was higher in atypical DFD beef. However, expressions of HSP70 on days 1 and 3 were higher in typical DFD, while the expression of HSP90 on day 1 was higher in atypical and typical DFD compared to the normal beef (p < 0.05). Interestingly, the expression of HSP27 was positively correlated with shear force readings. HSP70 and HSP90 presented a direct correlation with pH and water-holding capacity and an indirect correlation with a* and b*, glycogen and lactate contents (p < 0.05). The study concluded that the heat-shock proteins could influence the formation of DFD beef possibly by regulating the development of postmortem metabolism and meat quality traits.

Packaging and pH Effects on Meat Discoloration through Electrochemistry

Myoglobin is the sarcoplasmic heme protein that determines the color of the meat. The oxidation state of myoglobin results in different forms of myoglobin, such as deoxy-, oxy-, and metmyoglobin. As the deviation from the bright red color of beef affects consumers' purchase decisions, meat packaging is done to retain the meat color and delay spoilage. In these studies, UV-spectrophotometric analysis is combined with the electrochemical method. Meat packaged under different conditions was considered. Two packaging conditions, vacuum and polyvinyl chloride, were compared with the normal unpackaged sarcoplasmic beef sample. Electrochemical regions of both positive and negative potential were diagnosed for sensory peaks where the data of vacuum packaging implied more color stability. To assess the effect of pH on meat discoloration, pH conditions of the physiological state (pH 7.4) and post-mortem meat (pH 5.6) were mainly considered. The rate of meat discoloration was higher at pH 5.6 than at pH 7.4. Electrochemical insights with regard to various packaging effects on meat discoloration will be discussed further.

Effects of oyster mushroom (Pleurotus ostreatus) stem residue supplementation on growth performance, meat quality and health status of broilers

Oyster mushroom stem residue, a by-product with medicinal and nutritive values, might be a prospective feed supplement in poultry nutrition. The study focused on evaluating the impact of oyster mushroom (Pleurotus ostreatus) stem residue (OMSR) powder supplementation on growth performance, carcass traits, meat quality, blood characteristics, and the cecal bacterial count in Arbor Acres broilers raised 35 d. A total of 144 day-old chicks, with an average weight of 40.27± 2.45 g, were divided into 3 groups: control (received a standard basal diet), antibiotic (basal diet + 75 mg/kg chlortetracycline), and OMSR (fed a basal diet with 300 mg/kg OMSR), where each group comprises 8 replications of 6 chicks. Supplementation of 300 mg/kg of OMSR powder in the broiler diet significantly (P < 0.05) enhanced the average daily gain (ADG) and final body weight as opposed to the control and antibiotic treatments, though the average daily feed intake was not influenced by OMSR supplementation during the whole experimental period. However, in comparison to the control and antibiotic groups, OMSR significantly reduced the postmortem breast meat drip loss percentage (P < 0.05) at 24 hours and on the seventh d. Furthermore, the OMSR group reported significantly elevated levels of Hb and RBC counts (P < 0.05), and decreased levels of serum triglyceride (TG) and total cholesterol (TC) concentrations (P < 0.05) on d 35 in comparison to broilers in the control and antibiotic groups. Additionally, the OMSR group exhibited an improved Heterophil/Lymphocytes (H/L) ratio (P < 0.05) relative to the broilers of the control and antibiotic groups. In contrast, the inclusion of OMSR in the broiler diet did not significantly (P > 0.05) influence other serum biochemical and hematological values tested. Broilers in OMSR group had reduced number (P < 0.05) of E. coli and Salmonella spp., but higher presence of Lactobacillus spp. (P < 0.05) in contrast to the control broilers. To summarize, the study's findings revealed that 300 mg of OMSR powder supplementation per kg of basal diet could be act as a natural growth promoter, and confer favorable effects on health and meat quality of broilers.

Effects of oxidative stress and protein S-nitrosylation interactions on mitochondrial pathway apoptosis and tenderness of yak meat during postmortem aging

To reveal the interaction of oxidative stress and protein S-nitrosylation on mitochondrial pathway apoptosis and tenderness development in postmortem yak meat. Herein, we selected yak longissimus dorsi muscle as the research object and treated hydrogen peroxide (H2O2) with S-nitrosoglutathione agent (GSNO) as well as Nω-nitro-L-arginine methyl ester hydrochloride (L-NAME) in mixed injections with 0.9 % saline as a control group, followed by incubation at 4 °C for 12, 24, 72, 120 and 168 h. Results showed that this interaction significantly increased mitochondrial ROS and NO content (P < 0.05) while weakening the antioxidant capacity of GSH and TRX redox response systems or accelerating the Ca2+ release process, leading to mitochondrial functional impairment and increased apoptosis rate. Notably, the H2O2 + L-NAME group showed more pronounced apoptosis. Hence, we suggest that the interaction between oxidative stress and protein S-nitrosylation could positively regulate yak meat tenderization.

Mitochondrial oxidative stress-mediated ferroptosis as a contributing factor of refrigerated beef tenderness: From mitochondrial biochemistry and proteomics perspective

This study aimed to investigate the mechanism of ferroptosis mediated by mitochondrial oxidative stress and its potential associations with tenderness of beef during refrigeration. Results showed that mitochondrial reactive oxygen species (ROS) reached a maximum at day 3 (116.67 ± 8.50 mg protein), the degree of mitochondrial swelling, mitochondrial membrane permeability increased with the increase of refrigeration time, and mitochondrial free iron content increased significantly (p < 0.05), while mitochondria showed the morphological features of ferroptosis. In addition, the decreased levels of reduced glutathione, total antioxidant capacity and the activity of glutathione peroxidase, and the accumulation of malondialdehyde reflected an imbalance in mitochondrial antioxidant defense system, presenting the physiological characteristics of ferroptosis. Furthermore, mitochondrial TMT quantitative proteomics identified 7 differentially expressed proteins (DEPs) enriched to the ferroptosis pathway, including ACSL1, LOC788801, ACSL4, PRNP, VDAC2, ACSL3 and LPCAT3, which were primarily involved in lipid metabolism pathway and were the major mitochondrial pathway involved in ferroptosis during beef refrigeration. Besides, ROS and lipid peroxidation from mitochondrial oxidative stress-mediated ferroptosis attacked tissue myofibril structure and increased myofibrillar fragmentation index, which promoted the improvement of postmortem meat tenderness. These findings provided new perspectives on the role of mitochondria in cell death and the effect of ferroptosis on muscle tenderization.

Microstructural evolution and mechanics behavior of postmortem meat subjected to resonance

The tenderness of meat is determined by muscle components, mainly including myofibrillar and connective tissues. In the present study, the microstructures evolution and mechanics behavior of yak postmortem muscle subjected to resonance vibration treatment was investigated by experimental and numerical investigation, in order to illustrate the resonance tenderization mechanism and the mechanical relationship of muscle components. The results show that there are three orders of natural frequencies of the raw yak meat, and the resonance frequency is determined as 26 Hz. By vibration treatment at this frequency, the shear force and MFI of the vibrated meat is 35.70 N and 62, respectively, exhibiting remarkable tenderizing effect compared with the raw sample and other frequencies treated samples. The microstructures and vibration modal simulation have revealed that the stress concentration happens in the junction of muscle fibers and extracellular matrix (collagenous connective tissues), leading to the detachment of endomysium connective tissues from muscle fibers and the disappearance of M-bands in myofibrils, thus resulting the significant tenderization. The resonance also causes the stress-strain behaviors of meat transiting from plastic deformation to elastic deformation. The experimental and numerical results reveal that the physical destruction of the cross-linkings or interactions between muscle fibers and endomysium connective tissues induced by resonance, plays a crucial role in the detachment of muscle components, transformation of stress-strain behavior and the significant tenderization effect.

Effects of Different Na+ Concentrations on cAMP-Dependent Protein Kinase Activity in Postmortem Meat.

cAMP-dependent protein kinase (PKA) activity regulates protein phosphorylation, with Na+ playing a crucial role in PKA activity. The aim of this study was to investigate the effects of different Na+ concentrations on PKA activity and protein phosphorylation level in postmortem muscle. The study consisted of two experiments: (1) NaCl of 0, 20, 100, 200 and 400 mM was added to a muscle homogenate incubation model to analyze the effect of Na+ concentration on PKA activity, and (2) the same concentrations were added to pure PKA in vitro incubation models at 4 °C to verify the effect of Na+ on PKA activity. The PKA activity of the muscle homogenate model increased with storage time in groups with different Na+ concentrations. High concentrations of Na+ inhibited sarcoplasmic protein phosphorylation. The PKA activity at 24 h of storage and the sarcoplasmic protein phosphorylation level at 12 h of storage in the group with 200 mM Na+ was lower than that of the other groups. After 1 h incubation, the PKA activity of samples in the 200 mM Na+ group was inhibited and lower than that in the other Na+ groups in the in vitro incubation model. These results suggest that the Na+ concentration at 200 mM could better inhibit PKA activity. This study provided valuable insights for enhancing curing efficiency and improving meat quality.

Secondary Lipid Oxidation Products as Modulators of Calpain-2 Functionality In Vitro.

The objective was to understand the impacts of secondary lipid oxidation products on calpain-2 activity and autolysis and, subsequently, to determine the quantity and localization of modification sites. 2-Hexenal and 4-hydroxynonenal incubation significantly decreased calpain-2 activity and slowed the progression of autolysis, while malondialdehyde had minimal impact on calpain-2 activity and autolysis. Specific modification sites were determined with LC-MS/MS, including distinct malondialdehyde modification sites on the calpain-2 catalytic and regulatory subunits. 2-Hexenal modification sites were observed on the calpain-2 catalytic subunit. Intact protein mass analysis with MALDI-MS revealed that a significant number of modifications on the calpain-2 catalytic and regulatory subunits are likely to exist. These observations confirm that specific lipid oxidation products modify calpain-2 and may affect the calpain-2 functionality. The results of these novel experiments have implications for healthy tissue metabolism, skeletal muscle growth, and post-mortem meat tenderness development.

Postmortem mitochondria function in longissimus lumborum of Angus and Brahman steers

Mitochondria function and integrity may impact postmortem metabolism and meat quality development. Adaptations in heat tolerant Brahman may persist to limit cellular stress postmortem. Our objective was to evaluate glycolysis, pH decline, and mitochondria function in longissimus lumborum (LL) from Angus and Brahman steers (N = 28) early postmortem (1 to 6 h) and after rigor (24 h). We evaluated metabolites of anaerobic glycolysis, ATP, pH, and temperature, and determined mitochondria oxygen consumption rate (OCR) in permeabilized fibers. The main effects of breed (b) and time (t) and the interaction were tested. Brahman LL contained greater ATP during the first 6 h postmortem; Brahman also tended to exhibit a slower pH decline (b × t, P = 0.07) and more rapid temperature decline (b × t, P < 0.001), but metabolites of anaerobic glycolysis were not different. Mitochondria in Brahman and Angus LL were well-coupled and respired at 1 h postmortem. However, outer membrane integrity became increasingly compromised postmortem (t, P < 0.001). Brahman tended to exhibit greater electron transport system capacity (b, P < 0.1) and had greater capacity for oxidative phosphorylation (complex I and II substrates) at 6 h compared with Angus (P < 0.001). In totality, greater ATP, slower pH decline, and enhanced mitochondria capacity indicate that Brahman possess mitochondrial properties or cellular adaptations that help protect the cell during energy stress postmortem. Slower pH and more rapid temperature decline in LL from Brahman may also help preserve mitochondria function postmortem.

Integrated metabolome, proteome, and transcriptome analysis explored the molecular mechanism of phosphoglycerate kinase 1 and pyruvate kinase M2 characterizing the postmortem meat quality

AbstractPhosphoglycerate kinase 1 (PGK1) and pyruvate kinase M2 (PKM2) have been identified as the postmortem meat quality biomarkers. However, the precise molecular mechanism through which they affect and regulate the development of meat quality remains unclear. In this work, the high‐ and low‐activity groups (n = 10) were selected from 60 lamb muscles at 24 h postmortem based on the activity levels of PGK1 and PKM2. The metabolomic, proteomic, and transcriptomic analyses combined with deeply integrated multi‐omics analysis were used to elucidate the mechanisms by which PGK1 and PKM2 characterize meat quality. The results indicated that glycolysis played a crucial role in regulating PGK1 and PKM2 activity at the metabolome, proteome, and transcriptome levels. In glycolysis pathway, we identified several key components closely related to PGK1 and PKM2 activity, including differential metabolites (adenosine triphosphate, adenosine diphosphate, glucose‐6‐phosphate, nicotinamide adenine dinucleotide phosphate, fructose‐6‐phosphate, dihydroxyacetone phosphate, 3‐phosphoglycerate, NAD+ nicotinamide adenine dinucleotide, lactate, and pyruvate), different abundance proteins (lactate dehydrogenase B and fructose bisphosphate aldolase B), and differentially expressed genes (hexokinase and fructose‐1,6‐bisphosphatase 1). It was concluded that PGK1 and PKM2 may affect the formation of meat quality by regulating these critical substrates. Additionally, PGK1 and PKM2 could also affect the tricarboxylic acid cycle, oxidative phosphorylation, and muscle contraction in postmortem and then influence meat quality. This integrative omics study offers valuable insight into unraveling the molecular mechanisms underlying postmortem meat quality development.

Remote post-mortem veterinary meat inspections in bovine and analysis of post-mortem inspection outcomes: preliminary results

The work aimed to collect and analyse data obtained from the routine post-mortem veterinary inspection of bovine viscera and to evaluate the reliability of remote veterinary meat inspections. A comparative study was conducted on viscera belonging to 30 bovines. For each bovine, findings were recorded simultaneously by two veterinarians, one conducting an on-site post-mortem inspection and another performing the remote inspection through a tablet. A total of 10 (33.33 %) bovines were healthy. In a total of 18 (60.00 %) and 11 animals (33.00 %) pulmonary and hepatic lesions were respectively, observed. The most reported finding was pleuritis recorded in 17 animals (56.67 %), followed by pneumonia (16.67 %). The agreement between the two methods used for the post-mortem inspection of bovines was generally high. In an overall 73.33 % of bovines the findings recorded by the veterinarian who conducted the on-site post-mortem inspection and those recorded by the veterinarian performing the remote inspection were overlapping. In conclusion, a move to a remote post-mortem inspection has a negligible negative impact on public health since the most frequently detected lesions recorded were of scarce significance and in most cases, they were effectively detected by the veterinarian through the tablet.

Phosphofructokinase mainly affects glycolysis and influences meat quality in postmortem meat

The aim of this study was to evaluate the comparative effects of hexokinase (HK), phosphofructokinase (PFK) and pyruvate kinase (PK) on glycolysis in postmortem meat. Three specific inhibitors were respectively added to postmortem lamb to produce a HK inhibition (HKI) group, a PFK inhibition (PFKI) group and a PK inhibition (PKI) group. Meat samples that assigned to these three groups and a control (CON) group were stored at 4 °C for 5 d. The results indicated that the activity of HK, PFK and PK were effectively restrained during storage. PFK activity was significantly correlated with lactate content (P < 0.05), but HK and PK activity showed a weak relationship with lactate content (P > 0.05). The myofibrillar fragmentation index of the PFKI and PKI groups were significantly lower than that of the CON and HKI groups (P < 0.05). The degradation levels of troponin T and desmin were the smallest in the PFKI group. The result of the myoglobin spectrum at 540 nm and 580 nm showed a decreasing level of oxymyoglobin after HK, PFK and PK inhibition. In conclusion, PFK showed a more dominant effect on glycolysis than HK and PK in postmortem muscle, which may provide a targeted strategy for meat quality regulation through glycolysis.

The Effects of Different Zilpaterol Hydrochloride Feed Supplements and Extended Aging Periods on the Meat Quality of Feedlot Bulls

This study researched the effects of two commercially available zilpaterol hydrochloride (ZH) β-adrenergic agonists, denoted as ZH-A and ZH-B, on the meat quality characteristics of typical South African feedlot bulls (taurine × indicus composites), over extended aging periods of up to 120 days. The effects of ZH were studied to address concerns about the possible adverse effects of ZH on beef quality following extended aging, which typically occurs during the exportation of beef by boat. The completely randomized control study consisted of 3 homogenous experimental groups, with 3 replicates per treatment and 50 bulls per replicate = 450 animals. Treatments were a negative control (CT) with no ZH supplementation added to the basal diet or a basal diet supplemented with either zilpaterol hydrochloride A (ZH-A) or zilpaterol hydrochloride B (ZH-B), both at 105 g ZH/ton, fed from the first day of the finishing period (D0) for 30 days. Subsamples were collected from 38 random carcasses from each treatment for proximate analysis and meat quality analysis using Longissimus dorsi samples. ZH supplementation decreased meat tenderness (Warner–Bratzler shear force values (WBSF)) of bulls fed ZH-A or ZH-B, compared to those fed the CT diet (p &lt; 0.05; η2 = 0.24). The WBSF values of both ZH treatments were about 0.5–0.8 kg higher during the aging periods compared to the CT, but ZH did not affect post-mortem meat aging or meat quality characteristics differently compared to the CT. Post-mortem aging per se influenced all meat quality characteristics investigated (p &lt; 0.001; η2 &gt; 0.30), showing improvements in WBSF, a decrease in meat colour and an increase in drip and cooking losses. L*-values increased from 3 to 56 days of aging and then decreased to day 120 (p &lt; 0.001; η2 = 032). Chroma values decreased from day 3 to day 120 (p &lt; 0.001; η2 = 0.50). Hue° decreased from day 3 to day 7 and stabilized until day 120 (p &lt; 0.001; η2 = 0.40). Moisture and cooking loss (CL) increased to 56 days and then decreased to 120 days.

Effects of pre-slaughter fasting on antemortem skeletal muscle protein degradation levels and postmortem muscle free amino acid concentrations in broiler chickens

This study investigated the effects of pre-slaughter fasting time on the relationship between skeletal muscle protein degradation levels at slaughter and chicken meat quality after 48 h of postmortem aging. Twenty-four broiler chicks at 0 d of age were used in this study until 28 d of age. At 27 d of age, the chickens were assigned to 4 treatment groups: 0 h of fasting (0H), 8 h of fasting (8H), 16 h of fasting (16H), or 24 h of fasting (24H). They were slaughtered at 28 d of age. Blood samples were collected before fasting and immediately before slaughter. Plasma Nτ-methylhistidine concentration, an index of skeletal muscle protein degradation level, and muscle free amino acid concentration were analyzed. Antemortem changes in individual plasma Nτ-methylhistidine concentrations were significantly increased in 8H, 16H, and 24H compared to that in 0H (P < 0.05). After 48 h of postmortem storage, the glutamic acid content in the pectoralis major muscles increased with fasting time (P < 0.05), and the umami taste of chicken soup in the fasting groups (8H, 16H, 24H) was higher than that in the 0H group (P < 0.05). The antemortem changes in plasma Nτ-methylhistidine concentrations were correlated with glutamic acid content in the pectoralis major muscles (r = 0.57, P < 0.05) and umami taste (r = 0.66, P < 0.05). These results suggest that skeletal muscle protein degradation levels at slaughter are related to postmortem chicken meat quality, especially glutamic acid content and umami taste.

87 Mitochondria: Life, Death, and the In-Between

Abstract Skeletal muscles exhibit considerable variation in their metabolic and contractile properties, which allows them to accomplish diverse functions in the living animal. Mitochondria content and function are key features driving oxidative capacity, and hence, the energy producing capacity of muscle fibers. In turn, these intrinsic muscle properties also influence postmortem muscle metabolism and the events that occur as living muscle becomes meat. This period is critical to the development of meat quality attributes. Yet, there is much that remains poorly understood regarding the conversion of muscle to meat. Considering that oxygen supply is removed at harvest, early efforts to understand postmortem metabolism primarily focused on glycolytic capacity. More recently, efforts have been redirected to mitochondria; not only are they critical for energy production, but mitochondria also influence calcium dynamics, apoptosis signaling, and reactive oxygen species production. These functions have been implicated in the development of meat quality attributes, including color variation, protein degradation, and tenderness. Defining the mitochondrial contributions to postmortem metabolism and meat quality is complex due to the heterogeneous nature of muscle fibers and the changes in cellular conditions (e.g., temperature, pH) that occur postmortem. Nonetheless, evidence supports that mitochondria retain at least some capacity for energy production early postmortem, indicating they are structurally intact and functional. Both inherent muscle characteristics as well as factors related to slaughter and processing appear to impact the subsequent decline in functional and structural integrity of mitochondria. Unraveling the structural and functional changes that occur in mitochondria postmortem will advance our understanding of early postmortem metabolism and meat quality development.

Validation of protein biological markers of lamb meat quality characteristics based on the different muscle types.

This work investigated the ability of 8 potential biomarkers (phosphoglycerate kinase-1 (PGK1), pyruvate kinase-M2 (PKM2), phosphoglucomutase-1 (PGM1), β-enolase (ENO3, myosin-binding protein-C (MYBPC1), myosin regulatory light chain-2 (MYLPF), troponin C-1 (TNNC1) and troponin I-1 (TNNI1)) to characterize meat quality by analyzing their relative abundance and enzymatic activity. Two different meat quality groups (Quadriceps femoris (QF) and Longissimus thoracis (LT) muscles) were selected at 24h postmortem from 100 lamb carcasses. The relative abundance of PKM2, PGK1, PGM1, ENO3, MYBPC1, MYLPF, and TNNI1 was significantly different between LT and QF muscle groups (P<0.01). Moreover, PKM, PGK, PGM, and ENO activity in LT muscle group was significantly lower than that in QF muscle (P<0.05). Suggesting that PKM2, PGK1, PGM1, ENO3, MYBPC1, MYLPF, and TNNI1 can be used as robust biomarkers of lamb meat quality, providing the reference for understanding the molecular mechanism of postmortem meat quality formation in future.