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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 (P0.05) 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 (P0.05) relative abundance of proteins associated with carbohydrate metabolism and apoptosis, and a lower (P0.05) 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 (P0.05) 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 (P0.05) 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.

Two methods that the beef cattle industry can use to improve efficiency, sustainability, and economic viability are growth promotants and crossbreeding cattle of different breed types. In the United States, over 90% of cattle receive an anabolic implant at some point during production resulting in an overall increase in skeletal muscle growth. Recent research suggests that the two main cattle breed types, Bos indicus and Bos taurus, respond differently to anabolic implants. The objective of this study was to characterize changes that occur in skeletal muscle following implanting in Bos indicus influenced steers or Bos taurus steers. Twenty steers were stratified by initial weight in a 2 × 2 factorial design examining two different breeds: Angus (AN; n = 10) or Santa Gertrudis influenced (SG; n = 10), and two implant strategies: no implant (CON; n = 10) or a combined implant containing 120 mg TBA and 24 mg E2 (IMP; n = 10; Revalor-S, Merck Animal Health). Skeletal muscle biopsies were taken from the longissimus thoracis (LT) 2 and 10 d post-implantation. The mRNA abundance of 24 genes associated with skeletal muscle growth were examined, as well as the protein expression of µ-calpain and calpastatin. Succinate dehydrogenase mRNA abundance was impacted (P = 0.05) by a breed × treatment interaction 2 d post-implanting, with SG-CON having a greater increased abundance than all other steers. A tendency for a breed × treatment interaction was observed for calpain-6 mRNA (P = 0.07), with SG-CON having greater abundance than AN-CON and SG-IMP. Additionally, calpastatin protein expression was altered (P = 0.01) by a breed × treatment interaction, with SG-CON and SG-IMP steers having increased expression (P = 0.01) compared with AN-CON steers. At 2 d post-implanting, a breed × treatment interaction was observed with SG-CON steers having greater (P = 0.05) mRNA abundance of mitogen-activated protein kinase compared with AN-CON steers. Furthermore, breed affected (P = 0.05) calpastatin abundance with AN steers having increased (P = 0.05) abundance 2 d post-implanting compared with SG steers. Meanwhile, implants tended to affect (P = 0.09) muscle RING finger protein-1 mRNA abundance, with CON steers having increased (P = 0.09) abundance compared with that of IMP steers. These findings suggest that cattle breed type and anabolic implants impact calpastatin expression and mRNA abundance associated with protein turnover in the LT of feedlot steers 2 and 10 d post-implantation.Two methods that the beef cattle industry can use to potentially improve efficiency, sustainability, and economic viability are growth promotants and crossbreeding cattle of different breed types. In the United States, over 90% of cattle receive at least one anabolic implant during the production cycle resulting in improvements in production and overall economic and environmental sustainability. Research suggests that the two main cattle breed types, Bos indicus and Bos taurus, respond differently to different anabolic implant strategies. The objective of this study was to characterize changes that occur in the skeletal muscle following implanting in Bos indicus influenced animals and Bos taurus animals. This research measured mRNA abundance of 24 genes associated with skeletal muscle growth, and protein expression of calpain-1 and calpastatin. The findings of this research suggest that anabolic implants and cattle breed type interact to cause changes in mRNA abundance in the longissimus thoracis that are related to protein turnover of skeletal muscle. Furthermore, calpastatin protein abundance was also altered by this breed × treatment interaction. This research demonstrates that anabolic implants cause molecular changes in skeletal muscle of feedlot steers, with some of these changes being breed dependent.

The roles of energy pathways in postmortem muscles are still debated. In this study, the contributions of different pathways to ATP production and pH variations were analyzed by using a kinetic model based on data from beef longissimus lumborum. Phosphocreatine represents over 92% of the initial ATP production but, after 24 h, glycolysis, phosphocreatine, myokinase reaction, and aerobic respiration contribute, respectively, 89.44%, 5.26%, 4.44%, and 0.86% of the cumulative amount of ATP produced. ATP hydrolysis and glycolysis result in 0.52 and 0.6 units of pH decline, respectively, at 24 h with ATP hydrolysis accounting for most of the early decline. Phosphocreatine, myokinase reaction, and aerobic respiration lead to, respectively, 0.08, 0.07, and 0.004 units of pH increase after 24 h though phosphocreatine is depleted within the first 30 min. Furthermore, electrical stimulation affects pH primarily through ATP hydrolysis and glycolysis. The initial muscle oxygen saturation level and phosphocreatine content affect pH but the influences are small.

The objective of this study was to investigate if ultrasonication of bovine longissimus thoracis et lumborum (LTL) steaks increases calpain-1 and caspase-3 activities, and if so, to explore the underlying mechanisms that trigger their activation. Post-rigor bovine LTL steaks were subjected to ultrasonication at 40 kHz and 12 W/cm2 for 40 min and subsequently aged for 14 d at 4 °C. Ultrasonication improved beef tenderness (P 0.05). Improved tenderness in the ultrasonicated steaks was associated with greater degradation of titin, desmin, troponin-T, and calpastatin and increased calpain-1 autolysis and caspase-3 activity (P

A kinetic model structure was developed to describe the major variations in energy metabolism and to gain further understanding of pH changes in postmortem muscle experimentally observed with an in vitro glycolytic system. Comparison with experiments showed that the model could describe the kinetics of major metabolites and pH under varied conditions. Optimized model parameters definitively and consistently showed the observed effects of mitochondria, indicating a desirable level of model complexity. Simulation and analysis of pH variations based on the model suggested that phosphofructokinase activity has the strongest impact on the rate and extent of postmortem pH decline. Postmortem pH is also influenced by rates of ATP hydrolysis and glycolysis, and to a much lesser extent, pH buffering capacity. Other reactions, including those mediated by creatine kinase, adenylate kinase, and AMP deaminase, have minimal effects on postmortem pH decline.

Fresh meat quality is greatly determined through biochemical changes occurring in the muscle during its conversion to meat. These changes are key to imparting a unique set of characteristics on fresh meat, including its appearance, ability to retain moisture, and texture. Skeletal muscle is an extremely heterogeneous tissue composed of different types of fibers that have distinct contractile and metabolic properties. Fiber type composition determines the overall biochemical and functional properties of the muscle tissue and, subsequently, its quality as fresh meat. Therefore, changing muscle fiber profile in living animals through genetic selection or environmental factors has the potential to modulate fresh meat quality. We provide an overview of the biochemical processes responsible for the development of meat quality attributes and an overall understanding of the strong relationship between muscle fiber profile and meat quality in different meat species.

To address the rapidly growing use of probiotics in animal agriculture, this review discusses the effect of probiotics on animal growth and development, immune response, and productivity. Several benefits have been associated with the use of probiotics in farm animals, such as improved growth and feed efficiency, reduced mortality, and enhanced product quality. While the mechanisms through which probiotics induce their beneficial effects are not well understood, their role in modifying the gastrointestinal microbiota is believed to be the main mechanism. The use of probiotics in fresh and fermented meat products has been also shown to reduce pathogenic and spoilage microorganisms and improve sensory characteristics. Although many benefits have been associated with the use of probiotics, their effectiveness in improving animal performance and product quality is highly variable. Factors that dictate such variability are dependent on the probiotic strain being utilized and its stability during storage and administration/inoculation, frequency and dosage, nutritional and health status as well as age of the host animal. Therefore, future research should focus on finding more effective probiotic strains for the desired use and identifying the optimum dose, administration time, delivery method, and mechanism of action for each strain/host.

Anaerobic glycolysis dominates energy metabolism postmortem. Even so, however, recent studies suggest mitochondria can modify postmortem energy metabolism and may contribute to pH decline, possibly affecting the transformation of muscle to meat and fresh meat quality development. Because oxygen is a necessary component of mitochondrial function, oxygenation of porcine and bovine longissimus thoracis et lumborum was determined postmortem using NIR spectroscopy. The ratio of oxy- to deoxymyoglobin decreased with time postmortem in both species. Metabolic analyses of muscle samples collected over the same timeframe also revealed fluctuations in TCA intermediates. Finally, mitochondria collected from muscle of electrically stimulated carcasses differed from those of non-stimulated muscle. Collectively, these data support the thesis that muscle mitochondria function early postmortem and may play a more active part in pH decline and possibly meat quality development.

The experiment was conducted to identify the mitochondrial protein responsible for enhancing glycolytic flux. We hypothesized that mitochondrial F1-ATPase promotes ATP hydrolysis and thereby the flux through glycolysis. Porcine longissimus muscle mitochondria were incorporated into an in vitro system designed to recapitulate postmortem glycolysis with or without Na-azide to specifically inhibit the β-subunit of mitochondrial F1-ATPase that catalyzes ATP hydrolysis. Addition of mitochondria enhanced ATP hydrolysis, glycogen degradation, lactate accumulation, and pH decline in the in vitro system. However, the majority of mitochondria-mediated enhancement in glycolytic flux was abolished in the presence of Na-azide. To investigate further, myofibrillar and mitochondrial proteins were added to the in vitro system after 240min from the initiation of the reaction. Greater pH decline and lactate accumulation were observed in system containing mitochondrial protein compared to their myofibrillar counterpart. In conclusion, mitochondrial F1-ATPase is capable of increasing glycolytic flux through promoting greater ATP hydrolysis at lower pH.

Preservation of meat through freezing entails the use of low temperatures to extend a product’s shelf-life, mainly by reducing the rate of microbial spoilage and deterioration reactions. Characteristics of meat that are important to be preserve include tenderness, water holding capacity, color, and flavor. In general, freezing improves meat tenderness, but negatively impacts other quality attributes. The extent to which these attributes are affected depends on the ice crystalline size and distribution, which itself is governed by freezing rate and storage temperature and duration. Although novel technology has made it possible to mitigate the negative effects of freezing, the complex nature of muscle tissue makes it difficult to accurately and consistently predict outcome of meat quality following freezing. This review provides an overview of the current understanding of energy and heat transfer during freezing and its effect on meat quality. Furthermore, the review provides an overview of the current novel technologies utilized to improve the freezing process.

Acute activation of AMP-activated protein kinase (AMPK) increases monocarboxylate transporter (MCT) expression in skeletal muscle. However, the impact of chronic activation of AMPK on MCT expression in skeletal muscle is unknown. To investigate, MCT1, MCT2, and MCT4 mRNA expression and protein abundance were measured in the longissimus lumborum (glycolytic), masseter (oxidative), and heart from wild-type (control) and AMPK γ3 pigs. The AMPK γ3 gain in function mutation results in AMPK being constitutively active in glycolytic skeletal muscle and increases energy producing pathways. The MCT1 and MCT2 mRNA expression in muscle was lower ( < 0.05) from both wild-type and AMPK γ3 animals compared to other tissues. However, in both genotypes, MCT1 and MCT2 mRNA expression was greater ( < 0.05) in the masseter than the longissimus lumborum. The MCT1 protein was not detected in skeletal muscle, but MCT2 was greater ( < 0.05) in muscles with an oxidative muscle phenotype. Monocarboxylate transporter 2 was also detected in muscle mitochondria and may explain the differences between muscles. The MCT4 mRNA expression was intermediate among all tissues tested and greater ( < 0.05) in the longissimus lumborum than the masseter. Furthermore, MCT4 protein expression in the longissimus lumborum from AMPK γ3 animals was greater ( < 0.05) than in the longissimus lumborum from wild-type animals. In totality, these data indicate that chronic AMPK activation simultaneously increases MCT2 and MCT4 expression in skeletal muscle.

Fresh hams display significant lean color variation that persists through further processing and contributes to a less desirable cured product. In an attempt to understand the underlying cause of this color disparity, we evaluated the differences in muscle characteristics and energy metabolites across semimembranosus (SM) muscles differing in color variation. The L* (lightness) and a* (redness) values were highest and lowest (P

Fresh turkey meat color is determined by many factors that include muscle fiber type composition and heme protein concentrations. These factors either are affected by or influence biochemical events occurring postmortem. Deviations in the processing environment also can result in aberrant fresh meat quality and may ultimately change the quality characteristics of further processed products. Our objective was to describe the underlying cause and significance of the two-toning color defect in fresh turkey breast. In the first experiment, pectoralis major muscles were collected, classified as single- or two-toned, and analyzed using image processing to characterize fresh turkey color. Samples from the large and small lobes of the pectoralis major muscle were collected for pH, glycolytic intermediates, protein abundance, mRNA expression, and quality characteristics. In the second experiment, time from stun to exsanguination was tested as a promoter of fresh turkey color. Results from the first experiment showed that the turkey breast possesses two distinct lobes. The large lobe had greater (P 0.05) glycolytic potential, lactate content, lactate dehydrogenase (LDH) abundance, and centrifugal drip loss, while pH, myoglobin mRNA expression, and soluble protein levels were lower (P 0.05) compared to the small lobe. Results from the second experiment showed that reducing time from stun to exsanguination enhanced (P 0.05) fresh turkey color by mitigating the differences between the two lobes. Our results also showed that birds exsanguinated first had greater (P 0.05) muscle pH values and body temperatures. These results show inherent differences in breast muscle and processing conditions interact to establish variations in fresh turkey color.

Insufficient acidification results in dark, firm, and dry beef. While this defect is often indicative of a stress event antemortem, muscle tissue may change in response to feeding regime. Longissimus dorsi muscle samples from 10 grain-fed and 10 grass-fed market weight, angus-crossbred beef cattle were collected postmortem. Lower (P

Our objective was to evaluate the efficacy of Color Muse and Nix Pro 2 colorimeters in measuring food color. To that end, measured color coordinates (L*, a*, b*, C*, and h*) of vegetables, fruits, cheeses, and meats by Color Muse and Nix Pro 2 were compared to values obtained with a Minolta CR-400 colorimeter. In general, color space values obtained with Color Muse were greater than those of CR-400 and Nix Pro 2 (P 90%). Taken together, our data suggest that Color Muse and Nix Pro 2 are reliable instruments that can be utilized as alternatives to high-cost colorimeters in food color research.

The purpose of this study was to test mitochondrial functionality under conditions simulating postmortem metabolism. Isolated mitochondria from porcine longissimus lumborum (LLM) and masseter (MM) muscles were incorporated into an in vitro model that mimics postmortem metabolism. pH and 13C-enrichment of glycolytic and tricarboxylic acid (TCA) cycle intermediates were evaluated at 0, 15, 30, 120, 240, and 1440 min. Addition of mitochondria to the in vitro model lowered its pH at 240 min compared with control. Reactions containing mitochondria had lower pyruvate and lactate [M + 2] and [M + 3] isotopomers at 240 and 1440 min than controls. Furthermore, LLM lowered the enrichment of [M + 2], [M + 3], and [M + 4]α-ketoglutarate at 1440 min compared with MM and control. Succinate [M + 2] and [M + 3] were greater in MM than the control and LLM. [M + 3]fumarate was greater in control at 240 and 1440 min than LLM and MM treatments. Our data indicated that mitochondria are capable of mobilizing pyruvate generated though glycolysis under conditions simulating muscle postmortem metabolism.

Animal selection based on growth rate has received greater attention as a selection index. While many have evaluated the effect of growth rate on muscle characteristics and meat quality, few studies have attempted to evaluate how selection based on growth rate alters muscle fiber characteristics and influences postmortem metabolism and subsequent meat quality. Therefore, the objective of this study was to evaluate muscle fiber type, postmortem metabolism and meat quality of Nellore cattle selected for different growth rates. Two-hundred and fifty non-castrated Nellore males differing in post-weaning growth potentials were used. Muscle from 10 high growth potential animals (EPDH) and 10 low growth potential animals (EPDL) were analyzed for muscle morphometric profile, postmortem metabolism, and meat quality. EPDH animals were heavier and had higher hot carcass weight and larger diameter and cross-sectional area of fast oxidative-glycolytic fibers, while EPDL animals had higher area percentage of slow oxidative fibers. Moreover, EPDH presented higher glycogen concentrations than EPDL cattle. Glucose concentrations were higher at 240, 720, and 1440 min postmortem, while G6P was higher from 30 to 1440 min postmortem in EPDL animals. Finally, EPDH animals produced less tender meat when compared to that of EPDL cattle. In conclusion, genetic selection based on growth potential is associate with a shift in fiber type towards a more glycolytic type of muscle that is associated with changes in meat tenderness.

Skeletal muscle glycogen content can impact the extent of postmortem pH decline. Compared to glycolytic muscles, oxidative muscles contain lower glycogen levels antemortem which may contribute to the higher ultimate pH. In an effort to explore further the participation of glycogen in postmortem metabolism, we postulated that increasing the availability of glycogen would drive additional pH decline in oxidative muscles to equivalent pH values similar to the ultimate pH of glycolytic muscles. Glycolysis and pH declines were compared in porcine longissimus lumborum (glycolytic) and masseter (oxidative) muscles using an in vitro system in the presence of excess glycogen. The ultimate pH of the system containing longissimus lumborum reached a value similar to that observed in intact muscle. The pH decline of the system containing masseter samples stopped prematurely resulting in a higher ultimate pH which was similar to that of intact masseter muscle. To investigate further, we titrated powdered longissimus lumborum and masseter samples in the reaction buffer. As the percentage of glycolytic sample increased, the ultimate pH decreased. These data show that oxidative muscle produces meat with a high ultimate pH regardless of glycogen content and suggest that inherent muscle factors associated with glycolytic muscle control the extent of pH decline in pig muscles.

The purpose of this study was to examine the role of mitochondria in postmortem calcium homeostasis and its effect on proteolysis and tenderness. We hypothesized that mitochondria buffer cytosolic calcium levels and delay the activation of calpain-1 and subsequently the development of meat tenderness. To test this hypothesis, pre-rigor bovine longissimus thoracis et lumborum muscle samples were injected with DS16570511 to inhibit mitochondrial calcium uptake. Free calcium, tenderness, texture profile analysis (TPA), calpain-1 activity, and proteolysis were evaluated over a 336 h aging period. Inhibition of mitochondrial calcium uptake increased (P

Postmortem lactate accumulation in skeletal muscle is linearly associated with the extent of pH decline. Yet, pigs harboring the AMPKγ3(R200Q) mutation produce meat with similar lactate levels to that of wild-type pigs but have a lower ultimate pH. We hypothesized that lower initial lactate levels and (or) lower buffering capacity in muscle of these pigs may help explain this discrepancy. Longissimus lumborum muscle samples were harvested at 0 and 1440 min postmortem from AMPKγ3(R200Q) and wild-type pigs. As expected, AMPKγ3(R200Q) muscle exhibited a lower ultimate pH but similar lactate levels to that of wild-type pigs at 1440 min postmortem. However, the total net lactate produced postmortem was greater in the AMPKγ3(R200Q) muscle due to lower initial lactate levels at 0 min postmortem. Buffering capacity measured over the pH range of 5.5-7.0 was also lower in AMPKγ3(R200Q) muscle. Greater net lactate accumulation postmortem (i.e., glycolytic flux) coupled with a lower buffering capacity explains the lower ultimate pH of meat from AMPKγ3(R200Q) pigs.

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 2.0 mg) 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 2.0 mg) reduced ATP loss from 30 to 120 min, but did not alter glycogen or lactate during this time. In reactions with mitochondria, inhibitors decreased ATP levels by 30 min and increased glycogen degradation by 60 min. Regardless of mitochondria content, inhibitors enhanced lactate accumulation from 15 to 240 min, and decreased pH from 15 min to 1440 min. In the in vitro model, mitochondria influence the maintenance of ATP, and inhibition of mitochondria enzyme activity contributes to accelerated metabolism and pH decline.

During postmortem metabolism, muscle pH gradually declines to reach an ultimate pH near 5.6 across most meat species. Yet, broiler pectoralis major (P. major) muscle generates meat with high ultimate pH (pH ∼ 5.9). For better understanding of the underlying mechanism responsible for this phenomenon, we evaluated the involvement of breast muscle chilling on the extent of postmortem metabolism. Broiler breast muscles were either subjected to chilling treatment (control) or left at room temperature (RT) for 120 min. P. major muscle from the RT treatment had lower ultimate pH, greater glycogen degradation and lactate accumulation. While these findings suggest that carcass chilling can contribute to the premature termination of postmortem metabolism, chilling did not fully explain the high ultimate pH of P. major muscle. Our results also revealed that glucose-6-phosphate (G6P) was very low at 24 h, and therefore we hypothesized that G6P was limiting. To test this hypothesis, muscle samples from P. major and porcine longissimus lumborum (LL) muscle were homogenized into a reaction buffer that mimics postmortem glycolysis with or without 0.5 mg/mL isolated mitochondria. While samples containing porcine LL muscle reached the normal level of ultimate pH, P. major muscle samples reached a value similar to that observed in vivo even in the presence of excess G6P, indicating that G6P was not limiting. Mitochondria enhanced the glycolytic flux and pH decline in systems containing muscle from both species. More importantly, however, was that in vitro system containing chicken with mitochondria reached pH value similar to that of samples containing LL muscle without mitochondria. To investigate further, phosphofructokinase (PFK) activity was compared in broiler P. major and porcine LL muscle at different pH values. PFK activity was lower in P. major muscle at pH 7, 6.5, and 6.2 than LL muscle. In conclusion, carcass chilling can partially contribute to the high ultimate pH of broiler P. major muscle, while low PFK activity and mitochondria content limit the flux through glycolysis.

The experiment was conducted to identify the mitochondrial protein responsible for enhancing glycolytic flux. We hypothesized that mitochondrial F

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.

Fresh meat quality development is influenced by pH decline that results from muscle glycolyzing energy substrates postmortem. The exact reason why glycolysis stops in the presence of residual glycogen remains unclear. We hypothesized that a critical glycolytic enzyme loses activity near the ultimate pH of meat. Porcine longissimus muscle samples were subjected to an in vitro system that mimics postmortem anaerobic metabolism at buffered pH values (7.0, 6.5, 6.0, 5.5 or 5.0). At pH7.0, 6.5, and 6.0, glycogenolysis and glycolysis proceeded normally while pH5.5 stopped lactate formation. Additional experimentation indicated that phosphofructokinase lost activity at pH5.5 while all other glycolytic enzymes remained active. A similar inactivation of phosphofructokinase was observed when using chicken and beef muscle. Elevated temperature hastened pH decline and phosphofructokinase activity loss. Thus, pH inactivates phosphofructokinase and arrests postmortem glycolysis, which may explain the similar ultimate pH across meat of different species.

Meat quality development, or the transformation of muscle to meat, involves a myriad of biochemical pathways that are largely well-studied in living muscle tissue. However, these pathways are less predictable when homeostatic ranges are violated. In addition, there is far less known about how various management or environmental stimuli impact these pathways, either by substrate load or altered cellular environment. Likewise, it is largely accepted that oxygen plays little to no role in the conversion of muscle to meat, as anaerobic metabolism predominates in the muscle tissue. Even so, the oxygen tension within the tissues does not fall precipitously at exsanguination. Therefore, transition to an anaerobic environment may impact energy metabolism postmortem. Antemortem handling, on the other hand, clearly impacts meat quality development, yet the exact mechanisms remain a mystery. In this paper, we will attempt to review those factors known to affect postmortem energy metabolism in muscle and explore those areas where additional work may be fruitful.

Postmortem changes that occur during the process of converting muscle to meat play a critical role in the development of quality traits and the overall acceptance of the fresh product. After an animal is harvested, muscle glycogen along with high-energy phosphate compounds is anaerobically mobilized in an effort to maintain adenosine triphosphate (ATP) homeostasis. As a consequence of postmortem glycolysis, lactate and H+ accumulate in the muscle and cause the drop in pH. Ultimately postmortem metabolism is arrested due to substrate depletion or the inactivation of the glycolytic enzyme phosphofructokinase-1, resulting in ATP depletion and the development of rigor mortis. The muscle subsequently undergoes proteolytic disruption of structural proteins, leading to an improvement of meat tenderness and flavor. Factors such as genetics, nutrition, environmental conditions, and pre- and postmortem handling can drastically influence the conversion of muscle to meat.

Muscle tissue experiences profound changes during its conversion to meat. Indeed, these changes are necessary and requisite for meat to assume those unique properties are keenly coveted by consumers of this highly nutritious and palatable food source. However, when this process is perturbed, the resulting quality is dramatically impacted. Therefore, understanding those reactions forming the basis of postmortem metabolism is incumbent to those interested in meat animal production. Initially, the biochemistry responsible for postmortem metabolism is simply an extension of those processes responsible for supplying energy to functioning skeletal muscle, responsible for locomotion. However, at some yet-to-be defined point, muscle tissues broach the physiological threshold where they begin to die and at this juncture, biochemical reactions dysregulate according to physiological normalcy. Even with the seemingly dearth of information available on the topic, our intent is to outline the biochemical processes responsible for postmortem metabolism and the conversion of muscle to meat as currently known.

Finding alternative feeds, such as sesame hulls and Prosopis juliflora species can attenuate difficulties of feed shortage and reduce the cost of animal feed in arid and semi-arid countries. Thirty-two Black male kids with similar initial weights (BW = 16.7±0.80 kg) and 120±5 d of age, were used to evaluate the effect of replacing barley grains and soybean meal with Prosopis juliflora pods (PJP) and sesame hulls (SH) on growth performance, digestibility and carcass and meat characteristics. Kids were equally divided into four dietary treatment groups for an 84-d fattening period. Treatment diets had similar crude protein (CP) and metabolizable energy (ME). The treatment groups were: (T1) no PJP nor SH, (T2) 10% PJP and 20% SH, (T3) 15% PJP and 15% SH, and (T4) 20% PJP and 10% SH. A tendency was detected (p

A 70-d experiment was conducted to evaluate the effect of feeding poultry broiler litter (BL) at levels 0 (BL0; n = 10), 100 (BL100; n = 10), and 200 g/kg (BL200; n = 10) on performance and carcass characteristics Awassi lambs. Nutrient intakes [i.e., dry matter (DM), organic matter (OM), crude protein (CP), neutral detergent fiber (aNDF), acid detergent fiber (ADF), and copper] were similar (P>0.05) between all diets except for ether extract (EE) intake which tended to be lower (P≤0.10) for the BL20 diet than the BL0 diet whereas BL100 not different from the other two diets. Dry matter, OM, CP, aNDF, and ADF digestibility was lower (P 0.05) average daily gain (ADG) and dry matter intake (DMI):ADG. For dissected loin, intermuscular fat content was lower (P

This study was conducted to investigate the effects of strain on broiler performance, and age at slaughter and post- chilling (PC) aging time on meat quality traits. A total of 500 one-day-old chicks (250 Hubbard classic and 250 Lohman) were reared under commercial conditions. Half of the broiler birds from each strain were slaughtered at 32 days and the other half at 42 days old. At each processing day, 168 carcasses were randomly selected (84 Hubbard and 84 Lohman) and divided into groups of 28 carcasses within each strain, and aged for 0, 4 and 24 h after chilling. Average weekly body weight was comparable between strains. Feed conversion ratio was higher (p

SUMMARY The influence of carcass weight, bird sex, and carcass aging time on meat quality traits of pectoralis major muscles was studied in broiler birds. A total of 800 birds were used. After processing, carcasses were graded into 3 categories: 1,500 to 1,600 g, 1,600 to 1,700 g, and greater than 1,700 g. Forty-two carcasses from broilers of each sex were randomly selected from each carcass weight category. Seven carcasses of broilers from each sex within the same carcass weight category were aged for 0, 2, 4, 6, 8, and 24 h postchilling. The ADG and FCR increased (P 0.05) by any of the factors. Cooking loss was affected only by bird sex. Lighter carcasses had a higher (P

Postmortem energy metabolism drives hydrogen accumulation in muscle and results in a fairly constant ultimate pH. Extended glycolysis results in adverse pork quality and may be possible with greater adenonucleotide availability postmortem. We hypothesized that slowing adenonucleotide removal by reducing AMP deaminase activity would extend glycolysis and lower the ultimate pH of muscle. Longissimus muscle samples were incorporated into an in vitro system that mimics postmortem glycolysis with or without pentostatin, an AMP deaminase inhibitor. Pentostatin lowered ultimate pH and increased lactate and glucose 6-phosphate with time. Based on these results and that AMPK γ3 R200Q mutated pigs (RN − ) produce low ultimate pH pork, we hypothesized AMP deaminase abundance and activity would be lower in RN − muscle than wild-type. RN − muscle contained lower AMP deaminase abundance and activity. These data show that altering adenonucleotide availability postmortem can extend postmortem pH decline and suggest that AMP deaminase activity may, in part, contribute to the low ultimate pH observed in RN − pork.

Background: Evidence indicates that the pathophysiological process of cardiovascular (CV) disease begins at early age, though the manifestations of the disease do not appear until middle age adulthood. Risk factors for CV disease, particularly lipoprotein profiles, are affected by physiological abnormalities, and lifestyle related issues. To evaluate prevalence of CV diseases risk factors among university students and to investigate relation between number of risk factors and body anthropometric, hematological and biochemical indices parameters. Methods: In this cross sectional study, 348 students were randomly recruited. Blood glucose, cholesterol profile (total, HDL, and LDL cholesterol), and triglyceride were measured using standard protocols. Physical activity (PA) level was assessed using the short-form Arabic version of the International Physical Activity Questionnaires (IPAQ). Results: The most commonly encountered CV disease risk factor was low levels of HDL-C, followed by physical inactivity, high levels TG, and obese BMI. When stratified by gender, females were less likely to have low HDL-C, and high TG, whereas, males were more likely to have overweight or obese BMI (P < 0.001). About 49% of the participants had at least one CV disease risk factor, where as the prevalence of having one, two and three or more CV disease risk factors were 35.7%, 9.3% and 4%, respectively. Additionally, the number of CV disease risk factors showed strong positive correlation with increases in body fat and bone percentages, glucose, total cholesterol, TG, LDL-C, BMI, and WHR (range of R2: 0.17 to 0.603). On the other hand, physical activity, percentages of body water and muscle, HDL-C showed inverse strong correlation with cardiovascular risk factors (range of R2: -0.239 to -0.412). Conclusions: Results indicate the high prevalence of CV disease risk factors among university students, and stress the need for early intervention programs to counteract these risks. Cardiol Res. 2012;3(4):172-179 doi: https://doi.org/10.4021/cr198e