Postmortem Muscle Metabolism Research Articles

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.

Ractopamine does not rescue Halothane and Rendement Napole metabolism postmortem

The objective of this study was to determine if ractopamine (RAC) impacts postmortem muscle metabolism and subsequent pork quality in Halothane (HAL) and Rendement Napole (RN) mutant pigs. All RAC fed pigs had increased (P < 0.04) L* values. HAL and RN mutants muscle had lower (P < 0.01) pH values but RAC feeding had no effect. RN mutants had higher and lower (P < 0.05) muscle pH and temperatures, respectfully at 15 min and RN mutant pigs had greater (P < 0.0001) glycogen initially but lactate levels similar to wild type (WT) pigs at 24 h. RAC lowered (P < 0.05) glycogen in RN mutants but not in HAL mutated or WT pig muscle. These data show RAC feeding changes postmortem energy metabolism but does not change pH and pork quality hallmark of two major pig gene mutations and supports our contention that ultimate meat quality traits and their biochemical drivers may be more complex than originally reasoned.

RNA-Seq exploration of the influence of stress on meat quality in Spanish goats

Studies exploring the transcriptome of stress and its effects on meat quality are very limited, particularly in goats. Fifty-four male Spanish goats (8-mo old; BW = 29.7 ± 2.03 kg) were randomly subjected to one of three treatments (TRT; n = 18 goats/treatment): (1) transported for 180 min, (2) transported for 30 min, or (3) held in pens (control) to analyze the transcriptome of stress and meat quality in goats using RNA-seq technology. Blood samples were collected before and after treatment, and meat samples were collected after humane slaughter for stress hormone, meat quality (Longissimus dorsi), and transcriptomic analysis. Plasma epinephrine concentrations were higher (P < 0.01) in 180 min and 30 min groups compared to the control group; however, norepinephrine concentrations were not affected by the treatment. Muscle glycogen concentrations (15 min postmortem) were lower (P < 0.01) in both 30 min and 180 min groups compared to the control group. Calpastatin levels were higher (P < 0.01) in 180 min and 30 min groups than the control group. Warner–Bratzler shear force values of loin chops were the highest in the 180 min group (4 ± 0.15, kg), lowest in the control group (3.51 ± 0.10, kg), and intermediate in the 30 min group (3.78 ± 0.09, kg; P < 0.01) both at day 1 and day 6 aging time. Additionally, desmin levels of day 6 samples were lowest in the control group, highest in 180 min group, and intermediate in 30 min group (P < 0.05). RNA-seq results showed that a total of 10,633 genes were differentially expressed (5194 up regulated; 5439 down regulated) among all comparisons (blood and day 1 and day 6 muscle samples). Among these differentially expressed genes (DEGs), KLF9, AMPK, FOXO3, PTX3, GADD45, PTPN1, CASP7, MAPK4, HSPA12A, and JAK-STAT were probably associated with the effects of stress on skeletal muscle proteins and involved in biological process such as cellular response to corticosteroid stimulus, endoplasmic reticulum stress, insulin resistance, DNA repair, apoptosis, MAPK cascade and regulation of proteolysis. The KEGG analysis revealed that AMPK and JAK-SAT signaling pathways and autophagy were among the top 20 enriched pathways in our treatment comparisons. The results provide an understanding of the genes and pathways involved in stress responses and related changes in postmortem muscle metabolism and meat quality characteristics in goats.

- Invited Review - Postmortem skeletal muscle metabolism of farm animals approached with metabolomics.

Skeletal muscle metabolism regulates homeostatic balance in animals. The metabolic impact persists even after farm animal skeletal muscle is converted to edible meat through postmortem rigor mortis and aging. Muscle metabolites resulting from animal growth and postmortem storage have a significant impact on meat quality, including flavor and color. Metabolomics studies of postmortem muscle aging have identified metabolisms that contain signatures inherent to muscle properties and the altered metabolites by physiological adaptation, with glycolysis as the pivotal metabolism in postmortem aging. Metabolomics has also played a role in mining relevant postmortem metabolisms and pathways, such as the citrate cycle and mitochondrial metabolism. This leads to a deeper understanding of the mechanisms underlying the generation of key compounds that are associated with meat quality. Genetic background, feeding strategy, and muscle type primarily determine skeletal muscle properties in live animals and affect post-mortem muscle metabolism. With comprehensive metabolite detection, metabolomics is also beneficial for exploring biomarker candidates that could be useful to monitor meat production and predict the quality traits. The present review focuses on advances in farm animal muscle metabolomics, especially postmortem muscle metabolism associated with genetic factors and muscle type.

An insight into farm animal skeletal muscle metabolism based on a metabolomics approach

Farm animal skeletal muscle, formed through development, growth, and maturation processes, is converted to edible meat during postmortem rigor mortis and aging. Live and postmortem muscle metabolism is the phenotypic determinant of muscle characteristics and meat quality traits such as flavor and color. Meanwhile, animal muscle metabolism, originally programmed by genetic program, is modulated by feeding and environmental conditions through changes in the biosynthetic network. Metabolomics deepens our understanding of metabolisms underlying skeletal muscle growth, maturation, abnormality, and postmortem meat aging. The metabolomics approach is beneficial to explore biomarkers to monitor meat production processes and products, leading to improvements in livestock productivity and meat quality. One of the recent metabolomics findings in animal muscle could be the impact of mitochondrial activity and energy metabolisms on meat quality. The present review overviews the advances in metabolomics studies of farm animal skeletal muscle, to gain an insight into the muscle metabolisms associated with livestock production and meat quality.

Hypoxia-inducible factor-1α nuclear accumulation via a MAPK/ERK-dependent manner partially explains the accelerated glycogen metabolism in yak longissimus dorsi postmortem under oxidative stress

Although exhaustive studies have established that oxidative stress is a key contributor to accelerated postmortem metabolism, the specific reasons remain fully undefined. We hypothesized that nuclear accumulation of hypoxia-inducible factor-1α (HIF-1α), a significant transcription factor for energy metabolism, regulates postmortem glycolysis under oxidative stress. Postmortem yak longissimus dorsi (LD) muscles were incubated with saline, hydrogen peroxide (H2O2), H2O2 plus MAPK/ERK inhibitor (U0126), or H2O2 plus U0126 and HIF-1α activator, dimethyloxalylglycine (DMOG), respectively. Changes in HIF-1α, MAPK/ERK signaling pathway, and postmortem metabolism levels were measured in muscles collected from all time points. Oxidative stress significantly activated MAPK/ERK pathway and increased HIF-1α expression and nuclear translocation (P < 0.05) although its mRNA levels were hardly affected (P > 0.05). Additionally, oxidative stress enhanced early postmortem muscle metabolism (P < 0.05). These effects were substantially weakened by U0126 treatment, which prevented oxidative stress-induced HIF-1α accumulation and glycolysis. Interestingly, this attenuation could be bypassed by DMOG (P < 0.05). Altogether, MAPK/ERK-dependent maintenance and enhancement of HIF-1α nuclear accumulation promotes postmortem metabolism during early postmortem under oxidative stress. These findings provide valuable information on postmortem metabolism that HIF-1α regulates glycolysis under oxidative stress and suggest that HIF-1α can serve as a target for controlling postmortem glycolysis.

Weighted Single-Step GWAS Identifies Genes Influencing Fillet Color in Rainbow Trout.

The visual appearance of the fish fillet is a significant determinant of consumers’ purchase decisions. Depending on the rainbow trout diet, a uniform bright white or reddish/pink fillet color is desirable. Factors affecting fillet color are complex, ranging from the ability of live fish to accumulate carotenoids in the muscle to preharvest environmental conditions, early postmortem muscle metabolism, and storage conditions. Identifying genetic markers of fillet color is a desirable goal but a challenging task for the aquaculture industry. This study used weighted, single-step GWAS to explore the genetic basis of fillet color variation in rainbow trout. We identified several SNP windows explaining up to 3.5%, 2.5%, and 1.6% of the additive genetic variance for fillet redness, yellowness, and whiteness, respectively. SNPs are located within genes implicated in carotenoid metabolism (β,β-carotene 15,15′-dioxygenase, retinol dehydrogenase) and myoglobin homeostasis (ATP synthase subunit β, mitochondrial (ATP5F1B)). These genes are involved in processes that influence muscle pigmentation and postmortem flesh coloration. Other identified genes are involved in the maintenance of muscle structural integrity (kelch protein 41b (klh41b), collagen α-1(XXVIII) chain (COL28A1), and cathepsin K (CTSK)) and protection against lipid oxidation (peroxiredoxin, superoxide dismutase 2 (SOD2), sestrin-1, Ubiquitin carboxyl-terminal hydrolase-10 (USP10)). A-to-G single-nucleotide polymorphism in β,β-carotene 15,15′-dioxygenase, and USP10 result in isoleucine-to-valine and proline-to-leucine non-synonymous amino acid substitutions, respectively. Our observation confirms that fillet color is a complex trait regulated by many genes involved in carotenoid metabolism, myoglobin homeostasis, protection against lipid oxidation, and maintenance of muscle structural integrity. The significant SNPs identified in this study could be prioritized via genomic selection in breeding programs to improve fillet color in rainbow trout.

Impact of Heatwaves on the Physiology and Retail Meat Quality of Lambs.

The experiment investigated the impact of heatwaves (HWs) on the physiology, postmortem muscle metabolism and meat quality of lambs. Seventy-two second-cross lambs (Poll Dorset × (Border Leicester × Merino)) were selected and exposed to either 1, 3 or 5 days of HWs or thermoneutal (TN) (28–38 °C and 40–60% relative humidity, RH; 18–21 °C, 40–55% RH) conditions in climate-controlled chambers. Lambs exposed to 1–5 days of a HW exhibited higher respiration rates (RRs), rectal temperatures (RTs), skin temperatures (STs) and heart rates (HRs) compared to lambs exposed to an equal duration of TN conditions. However, HWs had no significant effects on muscle metabolism (rate and extent of pH decline, muscle glycogen and lactate content) and meat quality (cooking loss and shear force). Similarly, there were limited impacts of 1–5 days of HW on the colour (L*, a*, b* and R630/580) and drip loss of the longissimus thoracis et lumborum (LTL) and semimembranosus (SM) muscles for 4 days’ overwrap retail display. Results suggest that short-duration HWs (1–5 days) had significant negative effects on animal physiology but had no effect on the muscle metabolism and meat quality.

Comparing Gas and Electrical Stunning: Effects on Meat Quality of Pigs when Pre-Stunning Physical Activity is Minimal.

A total of thirty pigs were experimentally slaughtered using gas (80% CO2 in air, 90 s; 30% CO2/70% N2O; 90 s) or electrical stunning (1.3 A, 10 s). Stunning may accelerate post-mortem muscle metabolism, due to psychological stress and/or muscle contractions. The specific effects of the stunning method were studied by limiting pre-stunning physical activity and stress: pigs were driven in a trolley from the rearing to the stunning site (6.5 m) and immediately slaughtered. Bleeding efficiency and carcass characteristics were similar and satisfactory for all stunning methods. Early post-mortem pH decline in the Longissimus lumborum was faster following gas compared to electrical stunning. The pH of other muscles was not influenced; color and drip loss showed minor effects. Hence, results are in contrast to current beliefs: compared to electrical stunning, following gas stunning, the stress and muscle contractions during the induction of unconsciousness have a slightly greater impact on Longissimus lumborum muscle metabolism; differences are minor and limited to certain muscles only.

Stress Associated with Simulated Transport, Changes Serum Biochemistry, Postmortem Muscle Metabolism, and Meat Quality of Broilers.

Simple SummaryThe objective of this study was to investigate the effects of the transportation on broilers through the use of a vibration and motion simulation machine. Short-term transport stress induced significant physiological changes in broiler chickens. Simulation of the vibration and motion associated transport for 2 h altered hormonal secretion and blood biochemical characteristics. However, after 4 h, the birds appear to regain homeostatic equilibrium. Despite this, the stress activated antioxidant defenses, acidified muscles and increased peroxidation, as well as decreasing the meat quality of broilers. This study supports and extends previous work that identified transportation as a major risk in relation to bird welfare and meat quality.Many factors contribute to the stress of transporting broilers from the farm to the processing plant. Using a motion simulation machine, a total of 144 male broilers were employed to determine the effect of motion, vibration, and feed withdrawal during transportation on serum biochemical parameters, postmortem muscle metabolism, and meat quality of broilers. The results indicated that transportation did not affect the activity of lactate dehydrogenase, γ-glutamyl transferase, aspartate aminotransferase, creatine kinase, and glucose in the serum, glutathione peroxidase in the breast and thigh muscle, nitric oxide synthase (NOS) in the breast, and heat stress protein 70 mRNA expression level in the liver (p > 0.05). Serum triiodothyronine, thyroxine, and insulin concentration declined with 2 h transportation (p < 0.05) and recovered with 4 h transportation (p < 0.05). NOS concentration in the thigh increased with 2 h transportation (p < 0.05) and recovered with 4 h transportation (p < 0.05). Two-hour and 4 h transportation increased the activity of superoxide dismutase in both muscles. Malondialdehyde, lactic acid, and drip loss24 h in both thigh and breast muscles increased, and glycogen in both muscles decreased with increasing transportation times (p < 0.05). Two-hour transportation did not influence pH45 min and pH24 h in the breast and thigh muscle, but these indexes decreased with 4 h transportation. This experiment supports and extends previous work that identified transportation as a major risk in relation to bird welfare and meat quality.

Relationship of glycogen and lactate concentrations as a pork quality indicator

Muscle metabolites greatly determine pork quality. However, precise threshold values which indicate its deterioration or improvement are not fully known. This study aimed to determine the influences of pork Longissimus lumborum (LL) glycogen and lactate concentrations measured at 45 min post mortem on pH, colour (L*a*b*) and drip loss (DL) measured during 144 hours post mortem in order to prescribe appropriate threshold values. The investigation used 30 gilts and 30 barrows being fattened for slaughter. After slaughter, the carcasses were assigned to groups based on the observed levels of glycogen and lactate: low GlyL with glycogen ≤35 μmol/g, GlyM with glycogen between 35 and 55 μmol/g, GlyH with glycogen &gt;55 μmol/g; LacL with lactate ≤40 μmol/g and LacH with lactate &gt;40 μmol/g. Lower muscle pH was noted up to 24 h post mortem in the LacH group compared to LacL (P ≤0.01). 24 h post mortem higher pH was found in GlyL than in GlyM and GlyH (P ≤0.01), which were similar. Similarly no statistical differences were noted between The GlyM and GlyH groups were also similar in L*, DL96 and DL144, with lower values found for GlyL (P ≤0.01). Compared to LacH, LacL had lower L*, DL48, DL96 and DL144 (P ≤0.01) and higher a* and b* values. Muscle pH, drip loss, L* and a* values were more affected by lactate concentration if the glycogen concentration ≥35 μmol/g muscle tissue. Thus, metabolite concentration may be a useful and valuable indicator of pork quality.&#x0D; Keywords: drip loss, glycolytic resources, pork colour, post-mortem muscle metabolism

What functional proteomic and biochemical analysis tell us about animal stress in beef?

Animal management practices may influence the animal's susceptibility to stress, with detrimental effects on the ultimate meat quality. In this field, proteomics is a promising tool that reveals the biological pathways underpinning the effect of animal's pre-slaughter stress (PSS) on the ultimate meat quality. The objective of this work was to study the effect of a pre-slaughter procedure that may promote stress, such as mixing unfamiliar animals during the transport and lairage period, on the post-mortem muscle proteome of young bulls reared under two different farm management systems (Intensive or Extensive). Comparative proteomics and biochemical analysis reveal the effect of PSS on biochemical pathways involved in the meat colour development, muscle redox status, energy metabolism and autophagy. This work highlights the potential of some muscle proteins such as Beclin-1 (autophagy marker), CKM (biomarker of energy transduction) and proteins of the energy metabolism (ALDOA, PYGM, PGM1, PKM, GPI) as potential biomarkers to discriminate beef samples according to the incidence of PSS. SignificanceMeat scientists are interested in the study of individual animal-based measurements that allow the detection of stress situations which could have negative effects on meat quality. In this context, the mechanisms underlying the adverse effects of pre-slaughter stress on the post-mortem muscle metabolism need to be elucidated in order to understand how animal stress may influence the conversion of muscle into meat. In this work, the study of proteome changes in the post-mortem muscle has allowed the identification of significant biomarkers of these processes that could be used as tools for detecting inappropriate strategies that may induce increased animal stress and, in consequence, may compromise the ultimate beef quality.

PH measured 24 hours post mortem should not be regarded as ultimate pH in pork meat quality evaluation

The aim of this study was to compare the diagnostic values of two methods in pork meat quality evaluation, that is, Method I: pH1 and pH24 and Method II: electrical conductivity (EC 2 ) and pH 24 , which included pH 24 , and their modifications, that is, Method III: pH1 and pH48 and Method IV: EC 2 and pH 48 , which included pH 48 measurement. Five meat quality classes, namely reddish-pink, firm and non-exudative (RFN), high quality (HQ), pale, soft and exudative (PSE), dark, firm and dry (DFD) and acid meat (AM) were assessed in four even-numbered genetic groups of 40 fatteners each, namely (L×Y)×D-A, (L×Y)×D-B, (L×Y)×H and (L×Y)×(D×P). The change of diagnostic method and therefore pH time measurement from 24 hours to 48 hours post mortem caused a major increase in the percentage of acid meat (AM) that was diagnosed. Most differences were observed in (L×Y)×H fatteners, namely 77.5% between Methods I and III and 75% between Methods II and IV. This increase in AM frequency indicates that as a result of significant changes in the post-mortem metabolism that occur in the meat ageing process pH 48 should be regarded as ultimate pH (pHu). Keywords : Acid meat, fatteners, post-mortem muscle metabolism

Effects of dietary energy sources on early postmortem muscle metabolism of finishing pigs.

ObjectiveThis study investigated the effects of different dietary energy sources on early postmortem muscle metabolism of finishing pigs.MethodsSeventy-two barrow (Duroc×Landrace×Yorkshire, DLY) pigs (65.0±2.0 kg) were allotted to three iso-energetic and iso-nitrogenous diets: A (44.1% starch, 5.9% crude fat, and 12.6% neutral detergent fibre [NDF]), B (37.6% starch, 9.5% crude fat, and 15.4% NDF) or C (30.9% starch, 14.3% crude fat, and 17.8% NDF). After the duration of 28-day feeding experiment, 24 pigs (eight per treatment) were slaughtered and the M. longissimus lumborum (LL) samples at 45 min postmortem were collected.ResultsCompared with diet A, diet C resulted in greater adenosine triphosphate and decreased phosphocreatine (PCr) concentrations, greater activity of creatine kinase and reduced percentage bound activities of hexokinase (HK), and pyruvate kinase (PK) in LL muscles (p<0.05). Moreover, diet C decreased the phosphor-AKT level and increased the hydroxy-hypoxia-inducible factor-1α (HIF-1α) level, as well as decreased the bound protein expressions of HK II, PKM2, and lactate dehydrogenase A (p<0.05).ConclusionDiet C with the lowest level of starch and the highest levels of fat and NDF could enhance the PCr utilization and attenuate glycolysis early postmortem in LL muscle of finishing pigs.

A mitochondrial protein increases glycolytic flux

The purpose of this study was to determine the role of mitochondria in postmortem muscle metabolism. Isolated mitochondria were incorporated into a reaction buffer that mimics postmortem glycolysis with or without mitochondrial electron transport chain inhibitors. Addition of mitochondria lowered pH values at 240 and 1440min regardless of inhibitors. Reduction in pH was accompanied by enhanced glycogen degradation and lactate accumulation. To explore the mechanism responsible for this exaggerated metabolism, mitochondrial preparations were mechanically disrupted and centrifuged. Resulting supernatants and pellets each were added to the in vitro model. Mitochondrial supernatants produced similar effects as those including intact mitochondria. To narrow further our target of investigation, mitochondrial supernatants were deproteinized with perchloric acid. The effect of mitochondrial supernatant was lost after perchloric acid treatment. These data indicate that a mitochondrial-based protein is capable of increasing glycolytic flux in an in vitro model and may partially explain acid meat development in highly oxidative AMPKγ3R200Q mutated pigs.

Pig cognitive bias affects the conversion of muscle into meat by antioxidant and autophagy mechanisms

Slaughter is a crucial step in the meat production chain that could induce psychological stress on each animal, resulting in a physiological response that can differ among individuals. The aim of this study was to investigate the relationship between an animal’s emotional state, the subsequent psychological stress at slaughter and the cellular damage as an effect. In all, 36 entire male pigs were reared at an experimental farm and a cognitive bias test was used to classify them into positive bias (PB) or negative bias (NB) groups depending on their decision-making capabilities. Half of the animals, slaughtered in the same batch, were used for a complete study of biomarkers of stress, including brain neurotransmitters and some muscle biomarkers of oxidative stress. After slaughter, specific brain areas were excised and the levels of catecholamines (noradrenaline (NA) and dopamine (DA)) and indoleamines (5-hydroxyindoleacetic acid and serotonin (5HT)) were analyzed. In addition, muscle proteasome activity (20S), antioxidant defence (total antioxidant activity (TAA)), oxidative damage (lipid peroxidation (LPO)) and autophagy biomarkers (Beclin-1, microtubule-associated protein I light chain 3 (LC3-I) and LC3-II) were monitored during early postmortem maturation (0 to 24 h). Compared with PB animals, NB pigs were more susceptible to stress, showing higher 5HT levels (P<0.01) in the hippocampus and lower DA (P<0.001) in the pre-frontal cortex. Furthermore, NB pigs had more intense proteolytic processes and triggered primary muscle cell survival mechanisms immediately after slaughter (0 h postmortem), thus showing higher TAA (P<0.001) and earlier proteasome activity (P<0.001) and autophagy (Beclin-1, P<0.05; LC3-II/LC3-I, P<0.001) than PB pigs, in order to counteract the induced increase in oxidative stress, that was significantly higher in the muscle of NB pigs at 0 h postmortem (LPO, P<0.001). Our study is the first to demonstrate that pig’s cognitive bias influences the animal’s susceptibility to stress and has important effects on the postmortem muscle metabolism, particularly on the cell antioxidant defences and the autophagy onset. These results expand the current knowledge regarding biomarkers of animal welfare and highlight the potential use of biomarkers of the proteasome, the autophagy (Beclin-1, LC3-II/LC3-I ratio) and the muscle antioxidant defence (TAA, LPO) for detection of peri-slaughter stress.

Mitochondria influence postmortem metabolism and pH in an in vitro model

Our objective was to determine the influence of mitochondria on metabolites and pH decline using an in vitro model of postmortem muscle metabolism. Mitochondria were isolated from porcine longissimus lumborum and added (0, 0.5, or 2.0mg) to powdered muscle in reaction media containing either a combination of inhibitors for mitochondria complexes (I, IV, and V) or diluent (without inhibitors). In the absence of inhibitors, adding mitochondria (0.5 and 2.0mg) reduced ATP loss from 30 to 120min, but did not alter glycogen or lactate during this time. In reactions with mitochondria, inhibitors decreased ATP levels by 30min and increased glycogen degradation by 60min. Regardless of mitochondria content, inhibitors enhanced lactate accumulation from 15 to 240min, and decreased pH from 15min to 1440min. In the in vitro model, mitochondria influence the maintenance of ATP, and inhibition of mitochondria enzyme activity contributes to accelerated metabolism and pH decline.

The Effect of Pre-Slaughter Resting Time on the Quality of Pork Meat

The quality of meat products strongly depends on fresh meat quality, which is the result of ante-mortem and post-mortem muscle metabolism, influenced by a series of factors. This study was conducted to investigate the influence on the final pork meat quality of different time periods spent by the living swine in the slaughterhouse prior to slaughtering. In the slaughterhouse, a total of 160 pigs were randomly chosen and divided into 2 mixed groups (males and females). The 83 animals in group A were slaughtered on arrival, while the 77 in group B had a period of 3 hours’ resting time. Fresh meat quality measurements (pH, L* value, drip loss) were performed on loins and hams for both groups. pH was measured on loin and ham muscles 45 minutes post mortem in-line at 360 C and in the cooling area 24 hours post mortem at 40C. Minolta colour L* value and drip loss for the loin muscles were measured 48 hours post mortem. A slice ca. 2 cm thick was taken from the Longissimus dorsi at the shoulder side and placed in consumer retail trays for the determination of drip loss and colour L* value. Parametric data were analyzed using ANOVA for both group A and B. There was a significant difference (p 0.05). According to the parameters investigated, the pigs with higher pre-slaughter resting time had a darker meat colour, a slower pH decline and a higher ultimate pH compared with the animals slaughter directly.

Effect of animal mixing as a stressor on biomarkers of autophagy and oxidative stress during pig muscle maturation

The objective of this work was to study the postmortem evolution of potential biomarkers of autophagy (Beclin 1, LC3-II/LC3-I ratio) and oxidative stress (total antioxidant activity, TAA; superoxide dismutase activity, SOD and catalase activity, CAT) in the Longissimus dorsi muscle of entire male ((Large White×Landrace)×Duroc) pigs subjected to different management treatments that may promote stress, such as mixing unfamiliar animals at the farm and/or during transport and lairage before slaughter. During the rearing period at the farm, five animals were never mixed after the initial formation of the experimental groups (unmixed group at the farm, UF), whereas 10 animals were subjected to a common routine of being mixed with unfamiliar animals (mixed group at the farm, MF). Furthermore, two different treatments were used during the transport and lairage before slaughter: 10 pigs were not mixed (unmixed group during transport and lairage, UTL), whereas five pigs were mixed with unfamiliar animals on the lorry and during lairage (mixed group during transport and lairage, MTL). These mixing treatments were then combined into three pre-slaughter treatments – namely, UF-UTL, MF-UTL and MF-MTL. The results show that MF-UTL and MF-MTL increased significantly the muscle antioxidant defense (TAA, SOD and CAT) at short postmortem times (4 and 8 h; P<0.001), followed by an earlier depletion of the antioxidant activity at 24 h postmortem (P<0.05). We also found that mixing unfamiliar animals, both at the farm and during transport and lairage, triggers postmortem muscle autophagy, which showed an earlier activation (higher expression of Beclin 1 and LC3-II/LC3-I ratio at 4 h postmortem followed by a decreasing pattern of this ratio along first 24 h postmortem) in the muscle tissues of animals from the MF-UTL and MF-MTL groups, as an adaptive strategy of the muscle cells for counteracting induced stress. From these results, we propose that monitoring the evolution of the main biomarkers of autophagy (Beclin 1, LC3-II/LC3-I ratio) and muscle antioxidant defense (TAA, SOD, CAT) in the muscle tissue within the first 24 h postmortem may help the detection of animal stress and its potential effect on the postmortem muscle metabolism.

Effect of two stunning methods on postmortem muscle pH and meat quality of common carp (Cyprinus carpio L.)

Percussive and electrical stunning are the most promising methods in terms of rendering fish unconscious prior to slaughter. The aim of this study was to determine the effect of these two stunning methods on postmortem muscle changes and meat quality of common carps. The experimental fish were stunned either by percussion (Group 1) or by electrical current application (Group 2), both followed by immediate decapitation. Muscle pH was measured at different time intervals to assess the postmortem metabolic changes, whereas meat colour, drip loss and water activity were used as quality parameters. The fish in Group 1 showed slightly accelerated postmortem muscle metabolism, higher redness (a*) and yellowness (b*) colour values and lower water activity. Percentage of drip loss after 4 days of storage at 4 °C did not differ significantly between the two groups. Based on the obtained results we concluded that both tested stunning methods were not associated with high levels of stress and significant detrimental effect on the meat quality of common carps.