Occurrence of giant fibers in muscles from wild pigs native to the United States

The semimembranosus (SM) and triceps brachii (TB) muscles from wild pigs native to Florida. USA, were evaluated for histological characteristics. All three fiber types were present in both muscles in varying proportions, reflecting differences between tonic and phasic functioning muscles. Typical fiber arrangements were observed with red fibers grouped in clumps and surrounded by white fibers. The triceps brachii muscle contained a greater percentage of βR and αR fibers and possessed more giant fibers than the SM muscle which contained more αW fibers. The giant fibers observed resembled βR or αR fibers. The presence of hypertrophied fibers in the muscles from these wild pigs suggests that the 'giant fiber syndrome' is an intrinsic susceptibility for muscle fiber enlargement in these animals and not necessarily associated with breeding for muscularity since the carcasses from these pigs contained very small muscles and very little fat.     

The characteristics of muscle fiber types of longissimus thoracis muscle and their influences on the quantity and quality of meat from Japanese Black steers

Forty-four Japanese Black fattening steers from four groups, produced in four districts and consisting of differing genetic backgrounds were slaughtered to examine the characteristic differences in muscle fiber types at the 6th thoracic vertebra of the M. longissimus thoracis (LT). The influence of percentage, diameter, and relative area of each muscle fiber type on the carcass characteristics and some quantity and quality traits of beef taken from LT, were also investigated. Significant differences in the characteristics of the muscle fiber types were observed among the four groups, except for muscle fiber diameter in the αR fiber, and the relative area of each αW fiber. For all steers, the average percentages and diameters of each muscle fiber type, βR, αR and αW were 26.8, 18.5 and 54.7% and 51.4, 50.6 and 52.4 μm, respectively. The relative area of each fiber type was similar to those of muscle fiber composition. αR Fiber content had significant negative correlations with marbling score (p<0.05), intramuscular fat content (p<0.05) and ultimate pH value (p<0.05). Significant correlations between the diameter of each fiber type, and the quantity or quality traits of the meat were not found, with the exception of red fiber types (βR and αR) and meat color a(?) values (p<0.05) which were positively correlated.     

不同部位猪肉肌纤维类型组成与品质特性比较研究

为比较不同部位猪肉肌纤维类型组成与品质特性的差异,选取9头6月龄杜长大三元杂交猪背最长肌(Longissimus dorsi)、半膜肌(Semimembranosus)和半腱肌(Semitendinosus)3个部位猪肉作为研究对象,通过烟酰胺腺嘌呤二核苷酸四唑氧化还原酶(nicotinamide adenine dinucleotide-tetrazolium reductase,NADH-TR)染色法研究不同部位猪肉的肌纤维类型组成,并分析肌纤维类型数量比例、平均直径、横截面积、密度等肌纤维特性;测定不同部位猪肉的品质特性(p H值、色泽、蒸煮损失率、剪切力以及质构特性)。结果表明,背最长肌和半膜肌中主要为ⅡB型肌纤维(P<0.05),数量比例分别为82.03%和53.22%,半腱肌则主要由Ⅰ型(45.44%)和ⅡB型(39.01%)肌纤维组成。半膜肌中各类型肌纤维的平均直径和横截面积较大,总肌纤维密度最小(P<0.05),为42.15根/mm2。背最长肌的亮度值和蒸煮损失率最高(P<0.05),pH值和红度值最低(P<0.05);半膜肌的剪切力最高(P&l...     

Relationship of Fiber Type Composition to Marbling and Tenderness of Bovine Muscle

Beef carcasses (n = 65) were selected to range widely in marbling (moderately abundan: to practically devoid) and maturity (A, n = 25; B, n = 19; C, n = 6; D, n = 8; E, n = 7). Number, percent, area and mean diameter of β-red (βR), α-white (αW) and α-red (αR) muscle fibers were determined. Warner-Bratzler shear force values and taste panel tenderness ratings were also obtained. αW muscle fiber parameters were negatively correlated (P < 0.05) to marbling and tenderness ratings while αR and βR parameters were positively correlated (P < 0.05) to these quality attributes. The ratio of αW fiber area to βR and/or αR fiber area was correlated (P < 0.05) with marbling and tenderness. Regression analyses indicate that muscle fiber type composition is more highly related to marbling (marb) than it is to shear force value (SFV) or tenderness rating (TR) although all relationships were significant (P < 0.10). The relationship of these quality indicators to fiber type is greater within A maturity [marb, coefficient of determination (C.D.) = 65.09; SFV, C.D. = 65.09; SFV, C.D. = 28.85; TR, C.D. = 62.94] than for the entire population (murb, C.D. = 49.16; SFV, C.D. = 18.71; TR, C.D. = 30.47). It appears that the oxidative capacity of a muscle is related to marbling and tenderness and that muscle fiber type composition could possibly be used as a predictor of marbling potential.     

Effects of dietary α-lipoic acid on glycolysis of postmortem muscle

The effects of dietary α-lipoic acid (α-LA) on the pH value, AMP-activated protein kinase (AMPK) activation, and the activities of glycogen phosphorylase and pyruvate kinase in postmortem muscle were investigated. Eighteen C57BL/6J mice were fed diets containing 0%, 0.5%, and 1.0% α-LA. At the end of 2-week feeding trial, the mice were killed and longissimus muscles were sampled at 0-, 1-, and 24-h postmortem for pH determination and enzyme assay. The results showed that dietary α-LA treatment significantly slowed down the decrease of pH values in postmortem muscle. The ultimate pH values in postmortem muscle of mice receiving 0.5% and 1.0% α-LA treatments were 6.40 and 6.63, respectively, significantly higher than that (6.21) of no α-LA treatment (p<0.05). AMPK was activated at the early postmortem stage. Dietary α-LA can suppress the activation of AMPK in postmortem muscle. At 1- and 24-h postmortem, activities of AMPK were much lower in postmortem muscle of mice receiving 0.5% and 1.0% α-LA treatments than that with no α-LA treatment. Between these two dietary α-LA treatments, however, no difference in AMPK activity was observed, indicating that 0.5% dietary α-LA is enough to suppress AMPK in postmortem muscle. Similar to AMPK, glycogen phosphorylase activity was higher in the treatment without dietary α-LA than those with 0.5% and 1.0% dietary α-LA supplements. No difference in the activity of glycogen phosphorylase was observed between the 0.5% and 1.0% dietary α-LA treatments. Dietary α-LA had no significant influence on the activity of pyruvate kinase in postmortem muscle. All these results indicate that AMPK plays a role in glycolysis in postmortem muscle. Dietary α-LA supplementation can suppress the activation of AMPK in postmortem muscle, down-regulate the activity of glycogen phosphorylase, resulting in a higher ultimate pH values in postmortem muscle. Therefore, dietary α-LA supplementation is a potential way to reduce the incidence of pale, soft, exudative (PSE) meat.     

Profile of fiber types in muscles from wild pigs native to the United States

Histochemical and histological parameters of the longissimus (LD) and semitendinosus (dark and light portions) muscles from wild pigs native to Florida, USA, were investigated. All three fiber types were present in both muscles at varying proportions with typical (red fibers grouped in clumps and surrounded by white fibers) fiber arrangements for domestic porcine muscles (Cassens, 1971), contrary to the findings by Rahelic & Puac (1981), who examined the LD muscle of wild pigs native to Yugoslavia. These authors foud only βR fibers present in the LD muscle. In five of the six pigs in the present study, extremely and abnormally large fibers (giant fibers), possessing βR fiber characteristics, were observed. These giant fibers were found in both the LD and the semitendinosus (dark and light portions) and were not restricted to the periphery of the fasiculi. The presence of these giant fibers suggests some type of muscle myopathy syndrome in these pigs.     

Lessons to learn about postmortem metabolism using the AMPKγ3(R200Q) mutation in the pig

The development of pork quality attributes - including color, water holding capacity, and texture - are controlled largely by the rate and extent of postmortem pH decline. In turn, pH decline is thought to follow the anaerobic degradation of glycogen to "lactic acid". The "Hampshire effect" or Rendement Napole (RN(-)) pig, which has elevated muscle glycogen, propagated the widespread use of "glycolytic potential" to describe muscle's capacity for postmortem glycolysis. Since the evolution of glycolytic potential, there have been great strides in molecular and technical capabilities. Hence, it must be appreciated that the RN(-) pig possesses a mutation in the gene encoding the AMP-activated protein kinase (AMPK) γ3 subunit, which results in a non-conservative amino acid substitution (R200Q). AMPK, a major energy sensor in skeletal muscle, influences enzyme activity, gene and protein expression, fiber type, and mitochondrial biogenesis. The utility of glycolytic potential as indicator of ultimate pH should be reevaluated in the context of the metabolic differences between AMPKγ3 mutated and normal muscle. Understanding the metabolism and energetics in AMPKγ3 mutated muscle may provide insight into the mechanisms influencing the rate and extent of postmortem metabolism.     

Influence of breed and muscle metabolic type on muscle glycolytic potential and meat pH in pigs

Glycolytic potential and activities of myofibrillar ATPase, lactate dehydrogenase, citrate synthase, glycogen synthetases and glycogen phosphorylases were measured in five muscles from five Large White, eight Pietrain, seven Belgian Landrace and eight Penshire pigs (Penshire is a composite line including 50% Hampshire, 35% Duroc and 15% Large White blood). Additionally, ultimate pH was measured on the loin and four ham muscles. Muscles could be classified as follows on the basis of enzyme activities: Longissimus dorsi and Semimembranosus as 'fast white', Rectus abdominis as 'intermediate'. Trapezius and Masseter as 'slow red'. Small breed differences were observed in enzyme activities except for citrate synthase activity and degree of activation of glycogen phosphorylase in the 'fast white' muscles. Large Whites, Pietrains and Belgian Landraces did not differ in glycolytic potential whatever the muscle involved. Compared with these three breeds, Penshires had much higher glycolytic potential values in the 'fast white' muscles (+51 to 75%) and in the 'intermediate' muscle (+29 to 56%). However, in the 'slow red' muscles, there was almost no difference in this trait between the four breeds. The Penshire pigs showed lower ultimate pH than the pigs from the other breeds in three of the four ham muscles studied. It is concluded that muscle metabolic type must be considered when assessing breed variation in glycolytic potential, and that the high muscle glycolytic potential characterizing the Hampshire could be inherited as a dominant trait in Hampshire crosses.     

Post-natal changes in some histochemical and enzymatic characteristics of three pig muscles

Post-natal changes in histoenzymatic and enzymatic characteristics were studied in porcine longissimus, psoas major and tibialis cranialis muscles. The experiment was carried out on thirty-five female large White pigs: fifteen were slaughtered between birth and 120 kg body weight (BW) and twenty at the market liveweight of 100 kg. The relative growth of each of the three muscles in relation to BW appeared to be monophasic, the allometric growth rates differed significantly between muscles: 1·21, 1·08 and 0·97, respectively. Myofibers were classified according to their contractile and metabolic properties as βR, αR and αW fibers. In the three muscles, the percentage of β fibers increased from birth up to 2 months of age and little change occurred thereafter. Glycolytic fibers were detectable only from about one month onwards. Their percentage then increased rapidly up to 30-50 kg BW to reach 60%, 30% and 12% in longissimus, psoas major and tibialis cranialis muscles, respectively. Thereafter, these values only changed slightly. This histoenzymatic differentiation led to the typical type grouping found in pigs. Throughout the period studied, the cross-sectional area of the myofibers increased with some differences according to fiber type and muscle. Lactate dehydrogenase (LDH) specific activity was similar in the three muscles at birth and then increased rapidly up to 4-5kg BW (15-20 days of age), although to a greater extent in the future glycolytic muscle (longissimus) This increase then abruptly slowed down. The period between 15 and 20 days of age corresponds to a critical stage already known in the rearing of pigs, i.e. growth rate, body composition and food intake. Changes in isocitrate dehydrogenase (ICDH) specific activity were much slighter and differed according to the muscle. There were close correlations between percentages of αW fibers and enzymatic kinetic measurements from one month onwards.     

Muscle fiber type characterization and myosin heavy chain (MyHC) isoform expression in Mediterranean buffaloes

This study aimed to evaluate myosin heavy chain (MyHC) isoform expression and muscle fiber types of Longissimus dorsi (LD) and Semitendinosus (ST) in Mediterranean buffaloes and possible fibers muscles modulation according to different slaughter weights. The presence of MyHC IIb isoforms was not found. Only three isoforms of MyHC (IIa, IIx/d and I) were observed and their percentages did not vary significantly among slaughter weights. The confirmation of the presence of hybrid muscles fibers (IIA/X) in LD and ST muscles necessitated classifying the fiber types into fast and slow according to their contractile activity, by m-ATPase assay. For both muscles, the muscle fiber frequency was higher for fast than for slow fibers in all weight groups. There was a difference (P<0.05) in the frequency of LD and ST muscle fiber types according to slaughter weights, which demonstrate that the slaughter weight influences the profile of muscle fibers from buffaloes.     

A method for early determination of meat ultimate pH

A patented method of rapidly determining the ultimate pH from approximate glycolytic potential of muscles of slaughtered animals has been devised. The method is based on the rapid hydrolysis of muscle glycogen to glucose by the enzyme amyloglucosidase and subsequent measurement of the liberated glucose. In acetate buffer at pH 4.5, glucose concentration can be determined in 30 s with domestic meters for diabetes control. The meter response differed from that of glucose in blood, but was linear with concentration. In slurries comprising homogenised meat in acetate buffer and added glucose, a similar linear response was obtained. Amyloglucosidase was capable of rapidly hydrolysing glycogen to glucose in such slurries. In the 24 h following slaughter, a decrease in glycogen, as determined by glucose, occurred in parallel with the decline in pH. At the same time, lactate progressively accumulated as expected. Values for the approximate glycolytic potential and (by calibration) ultimate pH, were obtained on prerigor muscle within 7 min of muscle sampling in an industrial environment. The method is suitable for on-line application in beef abattoirs particularly those employing hot boning where ultimate must be known at the grading point.     

Fiber types in the longissimus muscle from water buffalo and selected domestic beef breeds

The distribution and area of longissimus muscle fiber types from two intact male water buffaloes, one Angus bull and one Charolais bull were evaluated. Only fibers of aerobic-oxidative capacity were present in the muscles of the water buffalo examined. The absence of αW fibers may imply some significant and distinct differences in muscle metabolic and functional characteristics. All three fibers types were present in the muscles from the Angus and Charolais bulls. These findings may implicate distinct and unique differences in meat characteristics from water buffalo, such as in organoleptic and/or processing traits.     

Green hams electrical impedance spectroscopy (EIS) measures and pastiness prediction of dry cured hams

The objective of this study was to assess the value of electrical impedance spectroscopy (EIS) as a predictor of certain dry-cured ham sensory properties in green hams of different technological meat qualities and processed commercially. Measurements of technological meat quality (weight, ham conformation, subcutaneous fat thickness, pH(45) and pH(u)) and some sensory properties (adhesiveness, hardness, crumbliness, pastiness, fibrousness and saltiness) were carried out on the Biceps femoris (BF) and Semimembranosus (SM) muscles. The electrical parameters, R(o), R(inf), ratio (R(inf)/R(o)), F(c) and α, were obtained with EIS equipment applied to two different regions of the ham at 36 h post mortem (BF and SM). Principal component (PC) analysis was used to describe the relationship between sensory properties and electrical parameters. For BF muscle there were no clear relationships between the electrical parameters and the sensory properties. However, for SM muscle, pastiness was correlated positively with the ratio and F(c) obtained by EIS. None of the electrical parameters obtained by EIS were able to differentiate between groups of hams classified according to their level of pastiness in the BF muscle. However, in the SM muscle, the origin of the pastiness was related to the use of PSE meat and was predicted by the electrical impedance measurements. The EIS prototype correctly detected 69.2 and 56.0% (for SM and BF muscles, respectively) of the problem hams in terms of pastiness. These results could be of use in the selection of the raw material to reduce the incidence of dry-cured hams with defective texture.     

不同部位牦牛肉肌纤维特性与肉品质差异

为从肌纤维特性方面探究牦牛3 个部位肌肉品质的差异,本研究以牦牛背最长肌、腰大肌和半膜肌为研究对象,比较了其剪切力、肌节长度、肉色、蒸煮损失率和pH值的差异,采用酶组织化学染色和实时荧光定量聚合酶链式反应法表征了其肌纤维特性,并分析了每个品质指标与肌纤维之间的相关性。结果表明：3 个部位肌肉的品质指标差异明显,其中腰大肌有较高的pH值和a*值,嫩度较好,而背最长肌保水性较好;3 个部位的肌纤维特性差异显著（P＜0.05）,腰大肌具有较高比例的I型肌纤维（50.8%）和较高的MYH7 mRNA相对表达量,肌纤维直径显著低于背最长肌和半膜肌（P＜0.05）;I型肌纤维数目比和肉品质密切相关,其与剪切力呈负相关,与肌节长度和蒸煮损失率呈正相关;I型肌纤维面积比与L*值呈显著负相关（P＜0.05）。结论：可以通过提高肌肉中I型肌纤维的比例来改善牦牛肉品质。     

棉秆皮的生物脱胶工艺因素分析

针对传统化学蒸煮为主的棉秆皮脱胶方法提取棉秆皮纤维时易产生碱废水污染环境的缺点,采用生物脱胶工艺提取棉秆皮纤维。运用正交试验对棉秆皮的果胶酶脱胶工艺进行了优化,分析了果胶酶制剂的浓度、处理时间、温度、处理的pH值四个因素对生物脱胶的影响。对正交实验的结果进行分析后得出棉秆皮纤维脱胶优化工艺条件是酶制剂浓度12%(owf),温度40℃,时间30h,pH值4.4,浴比1∶30。在优化工艺条件下对棉秆皮纤维的性能进行了测试,结果表明其性能优良。     

Thermal denaturation of proteins in Post rigor muscle tissue as studied by differential scanning calorimetry

Post rigor bovine M. semimembranosus was analysed by differential scanning calorimetry (d.s.c.). After extractive removal of sarcoplasmic proteins, subsequent pH adjustment and manual connective tissue removal, d.s.c. yielded reproducible thermograms which permitted investigation of the individual major myofibrillar proteins in various pH and salt environments without prior isolation. The positions of two major peaks, interpreted as myosin transitions, proved to be strongly pH dependent. At pH 5.4, the peak maxima occurred at 58 and 65°C, respectively, at a heating rate of 10°C min-¹. Above pH 6.5 their order of denaturation was reversed. In the pH range 5.4–6.5 the peak ascribed to actin had its maximum near 80°C in intact muscle. Above this pH range it was displaced to lower temperature. The thermal stability of actin was studied after treatment of the muscle tissue with different salt solutions. At equal ionic strengths (μ = 0.15) at pH 5.5, calcium chloride and sodium chloride caused 6.5°C and 4°C displacement to lower temperature, respectively. The thermograms of bovine semimembranosus muscle were compared to those of two red and two white muscle types (bovine cardiac and rabbit soleus muscles, chicken breast and rabbit semimembranosus muscles, respectively) at two pH levels. Greater myosin differences were found between red and white muscles than between muscles from different animal species. All muscles gave similar actin transitions, with exception of the heart muscle where the actin peak appeared at 3 °C lower temperature. The necessity of a strict pH control in order to obtain reproducible muscle thermograms is demonstrated.     

Glutathione Peroxidase in Post-Rigor Bovine Semitendinosus Muscle

Glutathione peroxidase (GSH-Px) activity was measured and selenium (Se) values obtained on beef semitendinosus muscles. TBA numbers were determined on stored, ground beef patties prepared from the same samples. Factors affecting the assay and the stability of the enzyme in post-rigor beef were examined. According to these studies, GSH-Px activity could be assayed directly from the muscle extract. The enzyme was viable throughout the rigor process and exhibited activity within the expected meat pH range. A statistically significant correlation between GSH-Px and muscle Se was obtained. The correlation coefficient was only moderately high (0.65). Comparison of the muscle Se values obtained in this study to a suggested minimum for nutritional adequacy in cattle indicated that values for several of the muscles in the present study were similar to or below this minimum value. Studies encompassing the total GSH-Px system are needed to determine if this system can serve to protect raw beef from oxidative deterioration during storage.     

Comparison of histochemical properties of different pig breeds

The study involved 158 pigs: 51 Hampshire (H), 54 Landrace (L) and 53 Yorkshire (Y). The aim of the study was to compare muscle histochemical properties of M. longissimus dorsi and adductor between muscles from pigs of purebred Hampshire, Landrace and Yorkshire lineages. The following histochemical properties were determined: 1) the percentage of type I, IIA and IIB fibers in number (calculated on the basis of the number of different fiber types) and area (calculated on the basis of the area of different fiber types) as analyzed with the myosin ATPase method using an acid preincubation solution of pH 4.6; 2) the cross sectional area of each fiber type; 3) the percentage of oxidative fibers on the basis of the NADH-TR method; and 4) the capillary density of the muscles. The cross-sectional area of type IIB fibers was the largest in Landrace. The highest capillary density (capillaries per mm(2)), 254 ± 38, was in longissimus of Hampshire. A positive correlation between M. longissimus dorsi and M. adductor was found in the percentage of type I, IIA and IIB fibers in number and area, cross-sectional area of each fiber type, and capillary density. The differences in histochemical properties between breeds were, however, smaller in M. adductor than in longissimus dorsi muscle. In addition, the variation in muscle fiber composition in pigs within the breeds was larger than the average variation between the breeds.     

Determination of Metmyoglobin Reductase Activity in Bovine Skeletal Muscles

A novel technique was used to obtain an isolate of skeletal muscle containing MetMb reductase. The isolate was then used as the enzyme source in an assay procedure to measure specific MetMb reductase activity. Enzyme activity was highest at pH 6.4 as compared to 5.8 or 7.0 and at 30°C compared to 4°C. Significant differences in enzyme activity were found among beef muscles from the same animal. The order of muscles, when enzyme activity was expressed on the basis of muscle myoglobin content, was: tensor faciae latae > longissimus dorsi > gluteus medius > diaphragma medialis > semimembranosus = psoas major (p = 0.01).     

PROPERTIES OF DRY-CURED HAM: TEMPERATURE AND pH INFLUENCE DURING SALTING STAGE

The influence of pH and temperature upon color properties, during the salting stage of 11 days for the dry-cured ham process was studied. Semimembranosus, Semitendinosus and Biceps femoris muscles were studied and each muscle was divided in three sections (outer, middle and inner). The parameters under study were: moisture, salt concentration, residual nitrite level, CIELAB and reflectance ratio (R650/R570). Neither temperature nor pH affected any parameter analyzed (P>0.05). Only Semimembranosus (and its outer zone) showed differences (P < 0.05) for moisture and salt concentration. A concentration gradient between muscles and Semimembranosus zones was found for residual nitrite level. Lightness, yellowness and chroma showed differences (P<0.01) for Semimembranosus muscle and its outer zone. Redness and reflectance ratio R650/R570 were not different (P>0.05) between muscles and zones. Only the Semimembranosus muscle was different (P<0.01) for hue. Semimembranosus and Biceps femoris zones were different (P<0.01 and P<0.05 respectively) for this parameter.