Red and white muscle

Mitochondrial function in skeletal muscle contributes to reproductive endothermy in tegu lizards (Salvator merianae)

AIM

In cyclic climate variations, including seasonal changes, many animals regulate their energy demands to overcome critical transitory moments, restricting their high-demand activities to phases of resource abundance, enabling rapid growth and reproduction. Tegu lizards (Salvator merianae) are ectotherms with a robust annual cycle, being active during summer, hibernating during winter, and presenting a remarkable endothermy during reproduction in spring. Here, we evaluated whether changes in mitochondrial respiratory physiology in skeletal muscle could serve as a mechanism for the increased thermogenesis observed during the tegu's reproductive endothermy.

METHODS

We performed high-resolution respirometry and calorimetry in permeabilized red and white muscle fibers, sampled during summer (activity) and spring (high activity and reproduction), in association with citrate synthase measurements.

RESULTS

During spring, the muscle fibers exhibited increased oxidative phosphorylation. They also enhanced uncoupled respiration and heat production via adenine nucleotide translocase (ANT), but not via uncoupling proteins (UCP). Citrate synthase activity was higher during the spring, suggesting greater mitochondrial density compared to the summer. These findings were consistent across both sexes and muscle types (red and white).

CONCLUSION

The current results highlight potential cellular thermogenic mechanisms in an ectothermic reptile that contribute to transient endothermy. Our study indicates that the unique feature of transitioning to endothermy through nonshivering thermogenesis during the reproductive phase may be facilitated by higher mitochondrial density, function, and uncoupling within the skeletal muscle. This knowledge contributes significant elements to the broader picture of models for the evolution of endothermy, particularly in relation to the enhancement of aerobic capacity.

Chronic Thermal Acclimation Effects on Critical Thermal Maxima (CTmax) and Oxidative Stress Differences in White Epaxial Muscle between Surface and Cave Morphotypes of the Mexican Cavefish (Astyanax mexicanus)

AbstractIn the face of increasing environmental temperatures, operative differences between mitochondrial function and whole-animal phenotypic response to the environment are underrepresented in research, especially in subtemperate ectothermic vertebrates. A novel approach to exploring this connection is to examine model species that are genetically similar but that have different whole-animal phenotypes, each of which inhabits different environments. The blind Mexican cavefish (Astyanax mexicanus) has the following two morphotypes: a surface form found in aboveground rivers and an obligate cave-dwelling form. Each morphotype inhabits vastly different thermal and oxygen environments. Whole-animal and mitochondrial responses to thermal acclimation and oxidative stress, with respect to increasing temperatures, have not been previously determined in either morphotype of this species. Here, we chronically acclimated both morphotypes to three temperatures (14°C, 25°C, and 31°C) to establish potential for acclimation and critical thermal maxima (CTmax) for each morphotype of this species. After measuring CTmax in six cohorts, we additionally measured enzymatic antioxidant capacity (catalase, superoxide dismutase, and glutathione peroxidase activities), peroxyl scavenging capacity, and lipid peroxidation damage in white epaxial muscle for each individual. We found a significant effect of acclimation temperature on CTmax (F = 29.57 , P < 0.001 ) but no effect of morphotype on CTmax (F = 2.092 , P = 0.162 ). Additionally, we found that morphotype had a significant effect on glutathione peroxidase activity, with the surface morphotype having increased glutathione peroxidase activity compared with the cave morphotype (F = 6.270 , P = 0.020 ). No other oxidative stress variable demonstrated significant differences. Increases in CTmax with chronic thermal acclimation to higher temperatures suggests that there is some degree of phenotypic plasticity in this species that nominally occupies thermally stable environments. The decreased glutathione peroxidase activity in the cave morphotype may be related to decreased environmental oxygen concentration and decreased metabolic rate in this environmentally constrained morphotype compared to in its surface-living counterparts.

Influence of Intramuscular Injection Sites on Pharmacokinetics of Amoxicillin in Olive Flounder (Paralichthys olivaceus) and Its Implication for Antibacterial Efficacy

This study aimed to investigate the effects of different injection sites, including dorsal, cheek, and pectoral fin muscles, on the pharmacological properties of amoxicillin (AMOX) in olive flounder (Paralichthys olivaceus) after a single intramuscular (IM) injection of 40 mg/kg. The AMOX concentration was measured using high-performance liquid chromatography-tandem mass spectrometry, followed by a non-compartmental model analysis. The peak serum concentrations (C_max) achieved 3 h after dorsal, cheek, and pectoral fin IM injections were 202.79, 203.96, and 229.59 μg/mL, respectively. The area under the concentration-time curve (AUC) was 1697.23, 2006.71, and 1846.61 µg/mL·h, respectively. The terminal half-life (t_1/2λ_Z) was prolonged for cheek and pectoral fin IM injections (10.12 and 10.33 h, respectively) compared to dorsal IM injection (8.89 h). In the pharmacokinetic-pharmacodynamic analysis, a higher T > minimum inhibitory concentration (MIC) and AUC/MIC values were observed after AMOX was injected into the cheek and pectoral fin muscles compared to the dorsal muscle. Muscle residue depletion was below the maximum residue level from day 7 after IM injection at all three sites. These findings suggest that the cheek and pectoral fin sites provide advantages regarding systemic drug exposure and prolonged action compared with the dorsal site.

Impact of feeding cover crop forage containing brassicas to steers during backgrounding on live animal performance, carcass characteristics, and meat color1

Brassica cover crops are an option for producers to incorporate into their cropping system to improve soil health and also provide a feed resource for cattle. While brassica cover crops have been widely used for grazing cows, their use as a backgrounding feedstuff is relatively unknown. The objective of this study was to determine the impact of feeding a brassica cover crop mixture during backgrounding on live animal performance and carcass characteristics. A total of 30 Angus-based steers were assigned to one of two dietary treatments during backgrounding 1) ad libitum access to a diet containing freshly cut brassica cover crop forage (CC) containing radish, turnip, rapeseed, rye grass, and a liquid supplement or 2) common Midwestern dry lot growing diet containing silage, soybean meal, grass hay, and a liquid supplement (CON). Steers were assigned to electronic feed bunks (Insentec RIC, Hokofarm Group; Marknesse, the Netherlands) for collection of individual feed intake. Diets were formulated to be nutritionally similar on a dry matter basis. Steers were paired by weight across treatments and pair fed. Dry matter intake (DMI) was calculated daily for steers in the CC treatment and the following day, CON steers were allowed access to an equal amount of dry matter using the Insentec RIC system. Steers were weighed weekly and backgrounded for 44 days before transitioning to a common finishing diet and weighed every 28 days. Steers were harvested at an estimated average backfat thickness of 1 cm. Standard carcass data were measured and strip loins and shoulder clods were collected. Instrumental and subjective color were measured on ground beef for 8 days and instrumental color was measured on strip steaks for 11 days. Treatment did not influence carcass characteristics, average daily gain, and DMI (P > 0.17). However, CON steers exhibited increased gain to feed ratio (P = 0.02). Additionally, a treatment by day interaction was observed for ground beef discoloration as the CC treatment displayed increased discoloration on days 4, 6, and 7 of case life (P < 0.01). These data indicate that brassicas may be utilized in a backgrounding diet without negatively impacting carcass characteristics but may decrease case life of ground beef.

An index to measure the activity attitude of broilers in extensive system

In organic poultry production it is important to rear animals with a dynamic attitude to take advantage of outdoor areas. Farmers are reluctant to use such strains due to their lower productivity and older slaughtering age. However, fast growing lines grown in organic system often suffer poor health and welfare conditions. The kinetic metabolism of chickens is correlated with different types of muscle fiber: type I (in red muscles or oxidative) for prolonged and moderate movement and type II (in white muscles or glycogenic) for fast movements. Red muscle metabolism produces energy mainly by β-oxidation of Highly Unsaturated n-3 Fatty Acids (HUFA). Accordingly, kinetic activity causes higher consume of HUFA in red muscles than in white muscles, so the ratio between n-3 HUFA and their precursor C18:3 n-3 (ALA) is likely to be smaller in red than in white muscles. However, these ratios are highly affected by the environment. To reduce the effect of environmental variables, we propose an "Activity index" as the difference between n-3 HUFA/ALA in white and red muscle within the same bird. This index, measured after slaughtering, should represent the activity performed by the chicken during its life. Given that birds in good health had the possibility of moving, the "Activity index" would measure the activity actually performed by the animals. Should birds of a given strain show a higher activity level, this would be an indication of the suitability of that strain to outdoor systems. This work verified the application of this "Activity index" on 90 birds from 6 genetic strains with known kinetic behavior reared in an experimental farm. The "Activity index" was also tested on chicken strains collected form commercial organic farms. The results confirmed that strains recognized for higher kinetic attitude actually walked more and their behavior was clearly detected by the "Activity index" estimated from their muscles.

Muscle Fiber Characteristics on Chop Surface of Pork Loin (M. longissimus thoracis et lumborum) Associated with Muscle Fiber Pennation Angle and Their Relationships with Pork Loin Quality

The influence of muscle architecture on muscle fiber characteristics and meat quality has not been fully elucidated. In the present study, muscle fiber characteristics on the chop surface of pork loin (M. longissimus thoracis et lumborum, LTL), pennation angle degree, and meat quality were evaluated to understand the pork LTL architecture and its relationship with the loin chop quality. Muscle fiber pennation degree ranged from 51.33° to 69.00°, resulting in an ellipse-shaped muscle fiber on the surface of pork loin chop. The cross-sectional area (CSA) on the sections cut vertical to the muscle length (M-Vertical) was considerably larger (p<0.05) than that on the sections cut vertical to the muscle fiber orientation (F-Vertical) regardless of the fiber type. Pennation angle is positively correlated with CSAs of F-Vertical (p<0.05) and with Warner-Bratzler shear force (r=0.53, p<0.01). Besides the shear force, lightness and pH were positively correlated with the fiber composition and CSA of IIX fiber (p<0.05); however, the redness, yellowness, drip loss, and cooking loss were not correlated with the pennation angle and muscle fiber characteristics on the chop surface (p>0.05). These observations might help us in better understanding pork loin architecture and the relationship between the pennation angle, muscle fiber characteristics, and meat quality of pork loin chop.

Ractopamine-induced fiber type-specific gene expression in porcine skeletal muscles is independent of growth

Feeding ractopamine (RAC), a β-adrenergic agonist (BAA), to pigs increases type IIB muscle fiber type-specific protein and mRNA expression. However, increases in the abundance of these fast-twitch fiber types occur with other forms of muscle hypertrophy and thus BAA-induced changes in myosin heavy chain (MyHC) composition may simply be associated with increased muscle growth known to occur in response to BAA feeding. The objective of this study was to determine whether RAC feeding could change the MyHC gene expression in the absence of maximal muscle growth. Pigs were fed either an adequate diet that supported maximal muscle hypertrophy or a low nutrient diet that limited muscle growth. RAC was included in diets at 0 or 20 mg/kg for 1, 2, or 4 wk. Backfat depth was less (P < 0.05) in pigs fed the low nutrient diet compared with the adequate diet but was not affected by RAC. Loin eye area was greater (P < 0.05) in pigs fed an adequate diet plus RAC at 1 wk but did not differ among remaining pigs. At 2 and 4 wk, however, pigs fed the adequate diet had greater loin eye areas (P < 0.05) than pigs fed the low nutrient diet regardless of RAC feeding. Gene expression of the MyHC isoforms, I, IIA, IIX, and IIB, as well as glycogen synthase, citrate synthase, β 1-adrenergic receptor (AR), and β 2-AR were determined in longissimus dorsi (LD) and red (RST) and white (WST) portions of the semitendinosus muscles. MyHC type I gene expression was not altered by RAC or diet. Feeding RAC decreased (P < 0.01) MyHC type IIA gene expression in all muscles, but to a greater extent in WST and LD. MyHC type IIX gene expression was lower (P < 0.05) in WST and LD muscles in response to RAC but was not altered in RST muscles. RAC increased (P < 0.05) MyHC type IIB gene expression in all muscles, but to a greater extent in RST. β 1-AR gene expression was unaffected by RAC or diet, whereas the expression of the β 2-AR gene was decreased (P < 0.001) by RAC. No significant RAC * diet interactions were observed in gene expression in this study, indicating that RAC altered MyHC and β 2-AR gene expression in porcine skeletal muscles independent of growth.

Contents and composition of individual phospholipid classes from biceps femoris related to the rearing system in Iberian pig

During dry-cured ham processing, phospholipids (PL) are the main substrates of lipolysis and oxidation. However, the published data on individual PL classes in the pig muscle are inconsistent. This study determined the PL class contents and composition in biceps femoris of Iberian pigs according to the rearing system (Montanera vs Pienso). Phosphatidylcholine (PC), phosphatidylethanolamine (PE), cardiolipin (CL) and sphingomyelin contents were higher in the Montanera pigs than in the Pienso pigs. Total PL and PC, PE, phosphatidylinositol + phosphatidylserine and CL contained higher levels of oleic acid and slightly higher levels of n-3 polyunsaturated fatty acids (PUFA) but lower levels of n-6 PUFA in the Montanera pigs than in the Pienso pigs. The rearing system had no effect on the plasmalogen content but influenced aldehyde composition, mainly in PE and in total PL. These results can partially explain the differences in sensory properties of dry-cured ham between the Montanera and Pienso systems.

Thermal stability vs. variability: Insights in oxidative stress from a eurytolerant fish

Climate change will increase the frequency, intensity, and duration of heatwaves. This thermal volatility will challenge to the oxidative homeostasis of aquatic ectotherms through many temperature-dependent environmental factors. In this study, we examined the effects of chronic exposure of sheepshead minnows (Cyprinodon variegatus) to multiple thermal regimes on the oxidative physiology of white muscle in these eurytolerant fish. The thermal treatments included stable (15 °C and 30 °C) and cycling regimes (between 21 and 29 °C at 6, 8 and 10-h intervals). The effect of these thermal treatments on oxidative stress during an acute thermal challenge (12 h at 32 °C) was also examined. Enzymatic activity of catalase (CAT), superoxide dismutase (SOD), and glutathione peroxidase (GPx), scavenging capacities of hydroxyl and peroxyl radicals, and lipid peroxidation (LPO) damage were quantified. We found no differences between or across treatments in any of the enzymatic antioxidants or LPO damage. We found that peroxyl radical scavenging was greatest at the peak of the 8- and 10-h thermal cycles. Peroxyl scavenging after an acute thermal challenge was greater than before the challenge for the steady 15 °C and 8-h cycle treatments, greater before the acute challenge for the steady 30 °C and 6-h cycle, and equivalent in the 10-h cycle. These findings demonstrate that even the most tolerant of marine ectotherms must engage oxidative defenses when presented with thermal variability and heighten concerns about the impact of climate change on less tolerant species.

Effect of gender on breast and thigh turkey meat quality

1. The influence of gender on chemical composition, physicochemical parameters, fatty acid profile, amino acid and mineral composition of turkey breast and thigh meat was studied in order to assess nutrient requirements. 2. Chemical composition showed that only intramuscular fat in breast meat was significantly affected by gender (p < 0.05). The results showed a higher percentage of intramuscular fat in male samples, almost double the amount found in females (0.73% vs. 0.38%). 3.For meat colour parameters, only a* showed different results between sexes, with male samples (breast: p < 0.01; thigh: p < 0.001) having the highest values. 4. Fatty acid profiles showed that medium chain unsaturated fatty acids were the most abundant. The significant differences (p < 0.05) found in both breast and thigh muscle could be linked to a difference in metabolism between males and females. 5.There were higher levels of C16:1n-7 in females (breast: p < 0.001; thigh: p < 0.01) compared with male muscle sample (5.05 vs. 2.67 g/100 g in breast and 4.95 vs. 3.27 g/100 g in thigh). Nutritional indices (n-6/n-3 and thrombogenic index) were more favourable in female samples demonstrating that female turkeys had better fatty acid profile than the others. 6. Turkey meat is an important source of dietary amino acids, and female samples had the highest contents both of essential and non-essential amino acids. Furthermore, gender had a numeric effect (p > 0.05) on amino acid composition. 7. Mineral composition showed that Na, Zn and Fe were the minerals most affected by turkey gender.

Fatty acid composition of several muscles and adipose tissues of pigs fed n-3 PUFA rich diets

During two months, sixty Pietrain×(Landrace×Large White) finishing pigs (50.7 to 115.2kg live weight) received diets containing various levels of C18:3n-3 from linseed and C22:6n-3 from Schizochytrium microalgae to increase the content of these fatty acids (FA) in their lean and fat tissues. Samples of tissues have been extracted from the carcass at the slaughterhouse. Tissues of pigs fed linseed had the highest C18:3n-3 and C20:3n-3 contents, while the C20:4, C20:5 and C22:6n-3 contents increased in tissues with microalgae diets. Diaphragm was fatter, but contained less monounsaturated FA, total n-6 and n-3 polyunsaturated FA (PUFA) than longissimus thoracis et lumborum and semimembranosus muscles due to their different roles. The leaf fat was the most saturated and monounsaturated tissue, regardless of the diet. Adipose tissues located in extremities contained more n-3 and n-6 PUFA than adipose tissues located in the middle of the carcass. This study showed the existence of a PUFA gradient depending on tissue location.

Meeting the meat: delineating the molecular machinery of muscle development

Muscle, studied mostly with respect to meat production, represents one of the largest protein reservoirs of the body. As gene expression profiling holds credibility to deal with the increasing demand of food from animal sources, excessive loss due to myopathies and other muscular dystrophies was found detrimental as it aggravates diseases that result in increased morbidity and mortality. Holding key point towards improving the developmental program of muscle in meat producing animals, elucidating the underlying mechanisms of the associated pathways in livestock animals is believed to open up new avenues towards enhancing the lean tissue deposition. To this end, identification of vital candidate genes having no known function in myogenesis, is believed to increase the current understanding of the physiological processes going on in the skeletal muscle tissue. Taking consequences of gene expression changes into account, knowledge of the pathways associated with their activation and as such up-regulation seems critical for the overall muscle homeostasis. Having important implications on livestock production, a thorough understanding of postnatal muscle development seems a timely step to fulfil the growing need of ever increasing populations of the world.

Proteome basis for intramuscular variation in color stability of beef semimembranosus

The objective of the present study was to characterize the proteome basis for intramuscular color stability variations in beef semimembranosus. Semimembranosus muscles from eight carcasses (n=8) were fabricated into 2.54-cm thick color-labile inside (ISM) and color-stable outside (OSM) steaks. One steak for sarcoplasmic proteome analysis was immediately frozen, whereas other steaks were allotted to retail display under aerobic packaging. Color attributes were evaluated instrumentally and biochemically on 0, 2, and 4days. Sarcoplasmic proteome was analyzed using two-dimensional electrophoresis and tandem mass spectrometry. ISM steaks demonstrated greater (P<0.01) abundance of glycolytic enzymes (fructose-bisphosphate aldolase A, phosphoglycerate mutase 2, and beta-enolase) and phosphatidylethanolamine-binding protein 1 than their OSM counterparts. Possible rapid post-mortem glycolysis in ISM, insinuated by over-abundance of glycolytic enzymes, could lead to rapid pH decline during early post-mortem, which in turn could potentially compromise its color stability. These results indicated that differential abundance of sarcoplasmic proteome contributes to intramuscular variations in beef color stability.

Hot-boning enhances cook yield of boneless skinless chicken thighs

Three experiments were conducted to evaluate the effects of postmortem deboning time on cook yield of boneless skinless chicken thighs. In experiment 1, chicken thigh meat was deboned at 0.75 (hot-bone), 2, and 24 h postmortem (PM) and trimmed to obtain mainly iliotibialis muscle. Samples were cooked directly from a frozen state. Cook yield of the muscle was significantly influenced by PM deboning time. Hot-boned thighs exhibited a 7% greater cook yield than the samples deboned at 24 h. In experiment 2, boneless skinless chicken thighs were deboned at 0.3, 2, and 24 h PM and cooked directly from a fresh, never-frozen state at 24 h PM. Cook yield of the hot-boned thighs was significantly higher than those of the 2 and 24 h deboned samples, which did not differ from each other. In experiment 3, whole legs (thigh + drumstick) were cut from the carcass backbone at 0.3 (hot-cut), 2, and 24 h PM. Thighs were separated from the legs (drumsticks) at either the same time the whole legs were removed from the carcasses or at 24 h PM. Intact thighs (bone in) were cooked fresh at 24 h PM. Color of fresh thigh muscles, cook yield, and Warner-Bratzler shear force of cooked samples were measured. Cook yield of the thighs cut from the backbone before chilling was significantly higher than those cut from the carcasses at 2 and 24 h PM, which did not differ from each other. The PM time at which intact thighs were separated from the leg (drumstick) did not influence cook yield. These results demonstrate that postmortem deboning time can significantly affect cook yield of boneless skinless chicken thigh products. Deboning chicken thighs after chilling reduces the cook yield. Differences in the cook yield of thighs may also result from the removal of whole chicken legs from the carcass backbone.

Impact of season on the chemical composition of male and female blesbok (Damaliscus pygargus phillipsi) muscles

BACKGROUND

The harvesting and consumption of game meat in South Africa is not limited to season. The study was thus aimed at investigating the seasonal impact on the chemical composition (moisture, protein, fat and ash contents) of male and female blesbok muscles (N = 32; longissimus dorsi, biceps femoris, semimembranosus, semitendinosus, infraspinatus and supraspinatus).

RESULTS

A significant interaction (P ≤ 0.01) existed between season and muscle type. Selected muscles had higher (P ≤ 0.01) mean protein contents with a higher plane of nutrition (spring of 2009), while longissimus dorsi muscles had the highest (P ≤ 0.01) mean intramuscular fat content (33.52 g kg⁻¹). A strong negative correlation (r = -0.82; P ≤ 0.01) existed between the muscles' moisture and protein content. The chemical composition of blesbok semimembranosus muscles was significantly different between seasons, while the other muscles were least affected by seasonal differences in blesbok plane of nutrition and activity levels.

CONCLUSION

The seasonal and muscle differences were statistically significant, but numerically small. It is therefore debatable whether this is of biological relevance relating to human nutrition.

Histochemical properties of fibre types in muscles of wild and domestic pigs and the effect of growth rate on muscle fibre properties

This study reports the results of a comparison of the histochemical properties of various types of porcine muscles in wild and domestic pigs. In domestic pigs, the influence of growth rates on these properties were studied in five muscles: longissimus dorsi (LD), semimembranosus (SM), gluteus superficialis (GS), infra spinam (IS) and masseter (MAS). The growth rate was expressed as: (i) live weight (LW) at 165±2 days and (ii) daily LW gain from day 88 to day 165 (DG) on the experimental diet. LD, SM, GS and IS of wild pigs were found to contain a higher area percentage of oxidative type IIA fibres (type IIA%(area)) and a lower percentage area of glycolytic type IIB fibres (type IIB%(area)) than the same muscles of domestic pigs. The capillary density in the light muscles (LD, SM, GS) of wild pigs was twice that of domestic pigs, indicating higher oxidative capacity. In domestic pigs the cross sectional area of type IIB fibres (CSA(IIB)) was markedly larger than the cross sectional area of type I (CSA(I)) and IIA (CSA(IIA)) fibres. The average fibre cross sectional area (CSA(fibre)) was about the same in the muscles of wild and domestic pigs except in LD and SM, where the average fibre cross sectional area was approximately 25% smaller in wild pigs than in domestic pigs. This difference was caused by the large cross sectional area of type IIB fibres in the light muscles of domestic pigs. In the light muscles of domestic pigs, the cross sectional area of type IIA fibres increased most with increasing growth rate. Growth rate influences muscle fibre properties only in light muscles, not in dark muscles.

Characterization of Longissimus thoracis, Semitendinosus and Masseter muscles and relationships with technological quality in pigs. 1. Microscopic analysis of muscles

Three porcine muscles (Longissimus thoracis, Semitendinosus, Masseter), known to have large differences in biochemical and histological traits, were fully characterized and the link between muscle structure and quality evaluated. The oxidative Masseter had more pigment, higher content of metmyoglobin, haem iron, protein and collagen, and was redder with higher fibre numbers, fibre circularity, pH and water holding capacity than the glycolytic Longissimus. Fibre type distribution showed predominance of type IIB in Longissimus and Semitendinosus white, type I in Semitendinosus red and IIA in Masseter. Type I fibres were larger than type IIB and IIA in Semitendinosus and Masseter, respectively, but not in the Longissimus, indicating that fibre size is muscle dependent. Muscle redness was positively correlated with type I fibre traits, haem iron and metmyoglobin, and negatively associated with type II fibre characteristics, non-haem iron and oxymyoglobin. Expressible juice had positive correlation with fibre size and negative with fibre number and connective tissue.

The influence of fiber size distribution of type IIB on carcass traits and meat quality in pigs

The effects of detailed characteristics such as the size and proportion of type IIB fibers in longissimus thoracis muscle on carcass traits and pork quality were investigated. A total of 96 pigs were classified into four groups by the proportion of different IIB fiber sizes. Group NS (high proportion of both small- and normal-sized IIB fibers) had a higher total number (136.4) and density (231.31) of type IIB fibers, backfat thickness (37.20 mm) and intramuscular fat content (4.77%) than the other groups (P<0.05), whereas Group NS had the lowest values of cross-sectional area (3413.85 μm2) and diameter (60.15 μm) of type IIB fiber among the groups (P<0.05). Pig muscles with higher percentage of large IIB fibers exhibit tougher, lighter and more exudative meat than pig muscles with a higher proportion of small- or normal-sized IIB fibers. Therefore, an increase in the proportion of large IIB fibers causes poor quality of pork.

Lipids in muscles and adipose tissues, changes during processing and sensory properties of meat products

Dry-cured meat products represent a large part of the meat products on the European market. The technologies develop for these products lead to the production of a large scale of meat products with typical sensory traits. Numerous studies have been devoted to optimise the quality traits of these products which are considered as traditional products by the consumer and provide a high added value to the producer. Among the components of the raw material, lipids play a key role in the final quality of these products. Many sensory traits of dry-cured meat products depend on lipid traits of muscle and adipose tissues of fresh meat and on their degradation through a complex set of lipolytic and oxidative reactions during processing. Lipid traits of both muscle and adipose tissues of fresh meat are strongly related to pig rearing conditions, mainly genotype and feeding strategy. During processing, lipids undergo intense lipid hydrolysis controlled by both lipases and phospholipases, which remain active all along the process. Lipids are also subjected to oxidation, which generates numerous volatile compounds. These volatiles contribute to some typical aroma notes of dry-cured meat products such as rancid, aged ham and dry-cured odours. This paper reviews the recent knowledge on the influence of lipid traits of fresh meat, lipid hydrolysis and oxidation on the development of sensory traits of dry-cured meat products.

The relationship between muscle fiber characteristics and meat quality traits of highly marbled Hanwoo (Korean native cattle) steers

To investigate the relationships between muscle fiber characteristics and meat quality traits of Korean native cattle, Hanwoo, Longissimus dorsi (LD), Psoas major (PM) and Semimembranosus (SM) muscles obtained from 18 Hanwoo steers and the muscle fiber characteristics were measured by histochemical analysis. Fiber number, area percentages and density of type IIA and IIB were lower in SM muscle, but higher in PM muscle than other muscles. LD muscle had higher pH(24h), L* value and fat content whereas SM muscle had lower L* value and fat content. The lowest WBSF with longer sarcomere length was observed in PM muscle, while SM muscle showed the highest WBSF with shorter sarcomere length. Consequently, the percentage of type I and IIB were highly correlated with meat quality traits and inversely correlated with fat content, L* value and WBSF. Fiber number and area percentage of type I had a positive correlation with fat content and L* value and a negative correlation with WBSF. These results suggest that Hanwoo steers had high marbling, more lightness and tenderness when the percentage of type I was high and the percentage of type IIB was low in muscle.

The prevalence of PSE characteristics in pork and cooked ham--effects of season and lairage time

A total of 180 pigs was slaughtered in the same slaughterhouse, but divided in six different trials distributed over Winter (December-March) and Summer (April-September). Meat quality measurements (pH, electrical conductivity, color and/or water-holding capacity) were carried out 30 min, 24 and/or 35h after slaughter in three different muscles: M. gracilis, M. semimembranosus and M. longissimus dorsi. A tendency towards a higher proportion of PSE meat during Summer was found in the examined muscles. Moreover a higher protein, higher dry matter content, a lower water/protein ratio and a lower slicing yield were found for the cooked hams suggesting a higher PSE prevalence in the Summer. A lairage time between 2 and 4h during Summer and less than 2h during Winter was related to a lower proportion of PSE meat. The correlation coefficients between the individual meat quality variables were moderate, but showed the predictive power of the pH measured 24h post-mortem in the M. gracilis for meat quality.

Fiber-type composition of muscles of the beef chuck and round

Thirty-eight muscles of the beef chuck and round were histochemically stained to characterize fiber-type composition in order to facilitate optimal muscle use in value-added products. Select-grade chucks and rounds (n = 4 each) were chosen to represent two carcass weight classes (250 to 295 kg and 363 to 410 kg) and two yield grades (1 and 3). Muscles were sectioned and stained with a procedure that included a succinate dehydrogenase and an adenosine triphosphatase staining technique. Number and diameter of beta-red, alpha-red, and alpha-white muscle fibers were used to determine muscle fiber percentage, muscle fiber area, and percent area in each muscle. Weight did not significantly (P > 0.05) affect these muscle fiber-type characteristics, probably because of limited sample numbers. Muscles containing greater than 40% beta-red fibers were classified as red; greater than 40% alpha-white fibers were classified as white. All other muscles were classified as intermediate. Nine of 12 round muscles were white, including semitendinosus, biceps femoris, rectus femoris, adductor, and semimembranosus. The chuck muscles were red (10 of 26), intermediate (9 of 26), and white (7 of 26). These data indicate variable fiber-type composition of most of the muscles of the beef chuck and round. Functional and biochemical traits of each muscle fiber class would be expected to create different processing characteristics, which would influence optimal muscle use in value-added products.

Denaturation of myofibrillar proteins from chickens as affected by pH, temperature, and adenosine triphosphate concentration

The susceptibility to denaturation of myofibrillar protein from chicken muscles was investigated and compared with denaturation of myofibrillar protein from pork. Immediately postmortem, the Pectoralis profundus (white muscle) and the Pubo-ishio femorale (red muscle) of six Arbor Acres chickens were collected. The Semimembranosus (white muscle) and Psoas major (red muscle) of three Yorkshire x Landrace and three Yorkshire x Landrace x Duroc pigs were collected at 45 min postmortem. Protein denaturation was prevented by keeping the muscles at 0 to 2 C in a buffer (pH 7.2) containing ethylene glycol-bis (beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA) (to sequester Ca ions). After purification, myofibrils were incubated at 25 or 40 C, pH 5.4 or 6.5, with 0, 0.68, or 3.4 mM adenosine triphosphate (ATP). Protein solubility, an indicator of denaturation, was assessed after 0, 10, 20, and 60 min incubation. Protein solubility of chicken pectoralis myofibrils was not affected by any of the conditions. In the other myofibrils, pH 5.4 caused significantly (P < 0.05) more protein denaturation than pH 6.5, and incubation at 40 C resulted in significantly more protein denaturation than incubation at 25 C. The presence of ATP (tested at pH 6.5) affected denaturation; higher ATP concentrations resulted in increased loss of solubility. We concluded that chicken red myofibrillar proteins are equally susceptible to denaturation as are pork red and white myofibrils. Chicken pectoralis (white) muscle fibers are least susceptible to denaturation. The results of this study indicate that factors other than protein denaturation are responsible for the low water-holding capacity of pale, soft, exudative chicken breast muscle.

Spatial distribution of myosin heavy chain isoforms and lactate dehydrogenase M4 in the limb musculature of two crossbred lambs

Sixteen different skeletal muscle samples were distributed in the cross-section of eight hip and thigh muscles. Contractile characteristics were assessed by measuring myosin heavy chain (MHCI, MHCIIa, MHCIIb) composition by electrophoresis. Glycolytic capacity was estimated by immunochemical quantitation of the LDH-M4. Histochemistry was used as a reference. The MHC isoform composition of most of the muscles in this study was heterogeneous. When an intramuscular transversal regionality was observed (semitendinosus, vastus lateralis, vastus medialis and rectus femoris muscles), MHCI percentage increased toward deeper layers, while MHCIIb and LDH-M4 decreased. The pattern of MHCIIa isoform distribution was less evident. Within semimembranosus and gluteus medius muscles, proportions of MHC isoforms were constant. Gradients of variation of MHCI and MHCIIb isoforms across rectus femoris and vastus medialis muscles were sharper than those of semitendinosus and vastus lateralis muscles. For the vastus lateralis muscle, these gradients may also be modified according to the breed. Breed effect was mainly shown by MHCIIb and MHCI isoforms and was not observed at all the sampling points of the muscles. These observations show that breed effect on muscle contractile and metabolic characteristics is not uniformly expressed throughout the muscle. Results of a comparison may differ according to the muscle and sampling location.