Relationship among collagen amount, distribution and architecture in the M. longissimus thoracis and M. pectoralis profundus from pigs

The relative distribution of types I and III collagens and collagen fibre architecture in the perimysium and endomysium were compared to the longissimus thoracis (LT) and pectoralis profundus (PP) muscles in pigs. The LT muscle was composed of type I myofibres 16.8%, IIA 12.9% and IIB 70.2%, and the PP muscle was 25.4, 23.1 and 51.5%, respectively. The total collagen amount differed significantly between the LT (2.66 mg/g) and PP (4.13 mg/g) muscle (P<0.001). On image analysis of the immunohistochemical preparations for types I and III collagens, the percentage area of the perimysium to the total collagen area showed significant differences between the muscles, where perimysial type I collagen occupied 25.4% of the total area in the LT muscle and 45.7% in the PP and perimysial type III 37.6 and 54.5%, respectively (P<0.001). In scanning electron microscopic photographs of the macerated preparation, very thick collagen layers composed of several fibre bands were observed in the perimysia of the PP muscle and appeared differently from the thinner perimysia with a few bands in the LT. Similar architecture of endomysial collagen fibres were observed around every myofibre type in the PP muscle and also in the LT. The fine surface cover of reticular collagen fibres around an adipocyte was shown as a global cast. These results suggested that the total collagen amount of the PP muscle was related mainly to the well developed perimysia composed of several collagen bands, indicating tougher meat compared with the LT muscle.     

Effects of carcass weight and muscle on texture, structure and myofibre characteristics of wild boar meat

Texture, histology and muscle fibre characteristic of selected muscles: m. quadriceps femoris (QF), m. biceps femoris (BF), and m. semimembranosus (SM) of wild boars of different carcass weight (20±2 and 60±3kgSD) were compared. Muscle texture (hardness, cohesiveness, springiness, chewiness) was determined with the double penetration test performed with the Instron 1140 apparatus. Structural elements (muscle fibre cross-section area, perimysium and endomysium thickness) and percentage of myofibres of each type: I (slow oxidative), IIA (fast oxidative-glycolytic) and IIB (fast glycolytic) per muscle fibre bundle, were measured in muscle samples using a computer image analysis program. The young wild boar muscles showed significantly lower values for the textural parameters (p<0.05). The muscle fibre cross-sectional areas of the juvenile wild boar muscles were significantly lower and the perimysium and endomysium thinner (p<0.05) than those in the old wild boar meat, while the percentage of type IIB fibres was higher. Of all the wild boar muscles tested, the highest hardness and chewiness values were found in BF which, at the same time, showed the highest fibre cross-sectional area and the thickest perimysium and endomysium. The highest percentage of I and IIA fibre types was typical of BF and SM either in young or in old wild boars with the lowest percentage of type I and the highest percentage of type IIB fibres being found in the QF. The results suggest that a higher hardness of wild boar muscles can be connected with a thicker perimysium and endomysium, fibres of higher cross-sectional area and probably a higher content of red fibres (type I).     

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.     

Intramuscular fat and muscle fibre lipid contents in halothane-gene-free pigs fed high or low protein diets and its relation to meat quality

Immediately after exsanguination, samples were taken from M. longissimus dorsi (LD) and M. biceps fermorsi (BF) of halothane-gene-free Swedish Yorkshire pigs (entire males and gilts) fed a high-protein (18·5% crude protein, 0·96% lysine; n = 20) or a low-protein diet (13·1% crude protein, 0·64% lysine; n = 20). The lipid content, measured as triglyceride (TG), was analysed after the samples had been freeze-dried and dissected free from blood, fat and connective tissue. Fibre type composition (type I, IIA, IIB, IIC) was analysed by histochemical staining on all samples. In 14 samples of LD, representing the entire variation of the intramuscular fat content (IMF) among the 40 animals, fibre areas, lipid content and oxidative capacity within the fibre types were evaluated. IMF, meat colour and drip loss were measured in both muscles. Shear force was measured on cooked meat samples from LD. IMF was higher in both LD (2·5%) and BF (2·0%) from pigs on the low-protein diet compared with LD (1·5%) and BF (1·3%) from pigs on the high-protein diet. TG content did not differ between diets in BF but was higher in LD from pigs on low- vis-à-vis high protein diet. A significant correlation was seen in LD between IMF and TG content (r = 0·57; P < 0·001). Fibre type composition did not differ between pigs on the two diets. BF had a higher proportion of type I and IIA fibres and a lower proportion of IIB fibres, compared with LD. TG content in muscle was not correlated with fibre type composition or staining intensity for lipids and oxidative capacity. High staining intensity for lipid in LD was seen in all type I fibres and in some type IIA fibres. Meat quality parameters did not differ between groups except shear force, which was higher in pigs fed the high- vis-à-vis low-protein diet (4·7 and 4·0 kg/cm(2), respectively). Shear force was correlated significantly with TG content (r = -0·42; P < 0·01) and IMF (r = -0·43; P < 0·01) in LD. The results of this study show that lipids are stored mainly in type I fibres and in some type IIA fibres. Intracellular triglycerides account for only a small fraction of IMF. The results indicate that IMF and TG content in muscle fibres may be related to shear force.     

Meat from wild boar (Sus scrofa L.): A review

Wild boar is a species that is utilised for food and sport hunting throughout the world. Recent increases in natural populations and the potential of farming wild boars have stimulated interest in this species as a meat producer. Compared to domestic pigs, wild boars present a higher degree of carcass fatness and larger loin areas, more slow-twitch oxidative (I) and fast-twitch oxidative glycolytic (IIA) and less fast-twitch glycolytic (IIB) muscle fibres, and darker, less tender and leaner meat. Differences in diets might contribute to differences in cooked meat flavour and fatty acid composition between wild boars and domestic pigs. Higher α-tocopherol concentrations in wild boar might extend its meat shelf-life. Mechanical massaging of muscles, vacuum package ageing and addition of marinates have been attempted to tenderise wild boar meat. Further research on hunting protocols for wild boar, and value-added products from its meat, are needed.     

Effects of massaging on hardness, rheological properties, and structure of four wild boar muscles of different fibre type content and age

Histochemistry (percentage number of three type fibres and their cross-sectional area) and changes in hardness, rheological properties (elastic and viscous moduli), and structural elements (mean fibre cross-sectional area and thickness of endomysium) of four wild boar muscles of different ages: biceps femoris (BF), semimembranosus (SM), quadriceps femoris (QF), and longissimus (L) subjected to effective massaging for 1, 2, 3, and 4 h were evaluated.

BF, with the high percentage of type I fibres, higher mean fibre cross-sectional area, thicker endomysium as compared with QF, SM and L, was harder, more elastic, and more viscous than the other three muscles. Muscles of older boars were found to contain higher percentages of type I fibres, lower percentages of type IIB fibres, bigger muscle fibre cross-sectional areas, thicker endomysium and higher values of hardness than the same muscles of young boars, whereas the percentage of type IIA fibres was about the same in the muscles of both groups. No effect of age on rheological properties was found. Muscle massaging resulted in an increase in the mean fibre cross-sectional area, changes in thickness of the endomysium, reduction in hardness and viscous moduli as well as in the elastic moduli of the muscles studied.

The lower the initial values of textural and structural parameters and percentage of type I fibres of a muscle were, the higher was the muscles susceptibility to massage. BF compared to SM, QF and L, of all the older boar muscles tested compared to those obtained from young boars were less susceptible to mechanical tenderization.     

Development of meat and carcass quality characteristics in Iberian pigs reared outdoors

A study of age-related changes in carcass traits and meat quality characteristics of Longissimus dorsi (LD) and Biceps femoris (BF) of free-ranged Iberian pigs was carried out to check whether the slaughter age used in the traditional management system of Iberian pigs is adequate. There was a great increase in live and carcass weight during fattening, principally due to an increase in fat deposition, as could be deduced from the percentage of dissectible fat and the backfat thickness. However, intramuscular fat in LD and BF showed only slight changes during the fattening. Myoglobin content tended to increase throughout lifetime in both muscles, whereas water-holding capacity decreased in intermediate ages and showed the highest values in the oldest animals. Total collagen content did not vary during lifetime; on the other hand, insoluble collagen increased from 7 to 77% of total collagen. It can be concluded that the traditional management system of Iberian pigs can be improved by fattening the pigs at a younger age, without negative consequences on the meat quality.     

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.     

Chemical composition,quality and histochemical characteristics of individual dromedary camel (Camelus dromedarius) muscles

This study characterized the chemical composition, quality and histological traits of six muscles from 10 dromedary carcasses. There were significant differences in moisture, fat, protein, mineral, saturated and unsaturated fatty acid contents between muscles. The longissimus thoracis (LT) had the highest cooking loss (33.5%) and triceps brachii (TB) the lowest (29.2%). The shear force value of semitendinosus (ST), semimembranosus (SM) and biceps femoris (BF) were significantly higher than infraspinatus (IS), TB and LT. The LT had significantly higher values for L*, a*, b* than ST. The SM had the lowest MFI (65.3), while IS had the highest value (75.8). The ST significantly had the highest and lowest proportions of Type I and Type IIA muscle fibers, respectively than other muscles. This study indicated that composition, quality, and histochemical parameters varied among camel muscles and the knowledge of this variation allows for better marketing and processing of camel meat.     

COLLAGEN CHARACTERISTICS AND MEAT TEXTURE OF PIGS EXPOSED TO DIFFERENT LEVELS OF PHYSICAL ACTIVITY

Intramuscular collagen and meat texture were measured in 23 female and 23 entire male pigs, subjected to one of three treatments: individual housing in pens of 2.5 m² (confined; C), individual housing and regular treadmill training (trained; T) and group housing equal to 0.9 m²/animal (free; F).
Treatment T tended (P = 0.13) to increase the activity of citrate synthase (CS) in M. biceps femoris (BF) from female pigs. Moreover, the heat stability of collagen and the mechanical resistance to 60 and 80% compression were increased (P<0.03) in BF from female pigs in treatments T and F as compared to C. In BF from male pigs, treatment T decreased (P = 0.03) the heat stability of collagen when compared to C and F. Sensory tenderness was not affected (P>0.05) by physical activity, however. In BF from female pigs, CS activity, collagen content and resistance to compression were lower (P<0.01) than in male pigs. In M. longissimus thoracis et lumborum, there was no effect of either physical activity or sex. Depending on muscle type and sex, physical activity affects meat texture.     

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.     

Effect of long-term betaine supplementation on chemical and physical characteristics of three muscles from the Alentejano pig

BACKGROUND: The use of betaine as a dietary supplement to reduce fat deposition and increase lean muscle mass in pigs is increasing. However, there is no available information on its effect on the physical and chemical (i.e. fatty acid (FA) profile) characteristics of pork. RESULTS: The effects of long‐term betaine intake (1 g betaine kg^?1 diet for 20 weeks) on the chemical and physical characteristics of Musculus longissimus dorsi, M. biceps femoris and M. semimembranosus from the Alentejano pig were investigated. The contents of total protein, intramuscular lipids (neutral and polar), myoglobin and total collagen as well as the water‐holding capacity, physical colour characteristics and FA profile of the three muscles were determined. With the exception of a significant increase in the intramuscular lipid content of M. longissimus dorsi and M. biceps femoris, betaine supplementation did not influence muscle chemical and colour characteristics or body fat deposition. CONCLUSION: These data suggest that long‐term betaine supplementation selectively increases intramuscular lipid deposition (a trait related to meat quality) while not affecting other chemical (including the atheroprotective FA profile) and physical characteristics of the Alentejano pig muscles studied. Copyright © 2012 Society of Chemical Industry     

Relation between muscular development and muscle collagen content in pigs

The relationship between muscle collagen content and muscular development was investigated in the pig using eight Large Whites, eight halothane-negative (HN) and eight halothane-positive (HP) Pietrain pigs. Three muscles varying in the degree of hypertrophy in Pietrain pigs as compared to Large White pigs were studied. Pietrain pigs had higher loin and ham percentages, as well as higher muscle to bone ratio in the ham than Large White pigs. A trend to lower collagen contents in Pietrain pigs as compared to Large White pigs was observed in biceps femoris and longissimus dorsi muscles, although the differences were not significant. On the whole, there does not seem to be any clear relationship between muscle collagen content and muscular development in the porcine species.     

Shear values of raw samples of 14 bovine muscles and their relation to muscle collagen characteristics

Raw samples of 14 muscles: Mm. biceps femoris (BF), quadriceps femoris (CF), diaphragm (DI), flexor digitorum (FD), gluteus medius (GM), infraspinatus (IE), longissimus lumborum (LL), longissimus thoracis (LT), psoas major (PM), pectoralis profundus (PP), semimembranosus (SM), semitendinosus (ST), sternomandibularis (STER) and triceps brachii (TB) from four Swiss Brown (485±15 days old) young bull carcasses and weighing approximately 300 kg were evaluated for some chemical and physical properties. PM (2.11 kg) and DI (2.24 kg) were the muscles which had the lowest Warner-Bratzler shear force values, while PP (6.66 kg) had the greatest shear force (P<0.05). FD and IE muscles had the highest concentration of total collagen content while PM and DI had the lowest (P<0.05) contents, TB and IE muscles presented the highest insoluble collagen concentration while PM and LT had the lowest (P<0.05) contents. High positive correlation between total collagen content and Warner-Bratzler shear force of raw samples was found (r=0.723; P<0.01) and between insoluble collagen content and Warner-Bratzler shear force was (r=0.661; P<0.01). Significant differences (P<0.05) were observed among muscles for differential scanning calorimetry, sarcomere length, pH and colour parameters.     

Thermal transition of collagen in ovine connective tissues

The thermal transition temperature (T(m)) of collagen in a range of muscle and non-muscle connective tissues from lambs, hoggets and mature sheep was measured by differential scanning calorimetry. The muscles selected were: semimembranosus (SM), semitendinosus (ST), biceps femoris (BF), Longissimus dorsi (LD) and psoas major (PM). Although the T(m) of intramuscular SM collagen from an aged ewe underwent no significant change with time post mortem, that of a 5-months-old lamb had dropped by 0·9°C after 2 days at 19°C. The epimysium of each muscle exhibited a higher T(m) than the corresponding intramuscular connective tissue. The LD and BF tendons each had a lower T(m) than corresponding intramuscular connective tissue but this was not true for the PM. Furthermore, the PM tendon generated an isometric tension more than five times that of the LD, BF or psoas minor tendons. This indicates that the PM tendon is richer in heatstable crosslinks than any of the other tendons investigated. In all tissues, except the liver capsule, there was an increase in T(m) with animal age. However, the rate of change T(m) varied from one tissue to another. For example, the SM intramuscular collagen matured at an earlier age than that of other muscles, the PM being slowest to mature. In keeping with the changes in T(m) values, the Warner-Bratzler peak force of ST muscles increased markedly in older sheep, but there was no significant difference in peak force of SM muscles between lambs, hoggets and mature sheep.     

The effect of handling pre-slaughter and carcass processing rate post-slaughter on pork quality

Forty-eight male crossbred (Large White—Landrace) pigs were used in a 2×2 factorial design to determine the effect of pre-slaughter handling (minimal and negative handling prior to slaughter) and the rate of carcass processing post-slaughter [normal rate (45 min) and delayed rate (70 min) from time of exsanguination to carcass entering the chiller] on muscle glycolysis and pork quality. Pigs negatively (using an electric goad) handled at the abattoir just prior to slaughter had lower muscle glycogen concentrations in the Longissimus thoracis (LT) and the Biceps femoris (BF) at all times post-slaughter and lower lactic acid at 5, 45 and 70 min post-slaughter compared to pigs minimally (no use of electric goads) handled prior to slaughter. Negative handling of pigs just prior to slaughter also resulted in pork which had higher surface exudate and a higher incidence of PSE compared with pigs minimally handled prior to slaughter. A prolonged rate of carcass processing resulted in reduced muscle glycogen in the LT and BF at all times post-slaughter. Delays in carcass processing rate also affected pork quality, as the meat was paler in comparison with pig carcasses that were processed without any delays. The results from this experiment have indicated that the use of electric goads to move pigs at the abattoir, and delays in carcass processing post-slaughter, can have a detrimental influence on ultimate pork quality.     

Performance of Cinta Senese pigs and their crosses with Large White 2. Physical, chemical and technological traits of Tuscan dry-cured ham

Technological, chemical and physical traits of cured ham from Cinta Senese and Large White pigs, and their crosses were investigated. Hams were obtained from 29 Cinta Senese (CS), 29 Large White × Cinta Senese (LW × CS) and 12 Large White (LW) pigs, fed a commercial mixture. Sensory and chemical–physical analysis was performed on a sample-slice and on muscles (Biceps femoris – BF; Semimembranosus – SM; Semitendinosus – ST) and subcutaneous fat. CS showed the highest trimming loss and the lowest salting loss. Hams of CS pigs scored higher for fatness than those of LW pigs, LW × CS showing intermediate values. On sample-slice, CS exhibited higher firmness, redness and marbling of lean, and greater fat extension than LW, with crosses having intermediate scores. Muscle moisture was lowest in CS, while both SM and BF from LW had the highest percentage of protein and the lowest of ash. CS showed higher intramuscular fat content than LW × CS and LW. Shear force of BF was higher in CS than in LW × CS and LW. With respect to LW, CS had lower values of L^* in muscles, and higher values of a^* in subcutaneous fat. Subcutaneous fat of CS contained less SFA and more MUFA than LW × CS and LW.     

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.     

Muscle metabolic traits, post mortem-pH-decline and meat quality in pigs subjected to regular physical training and spontaneous activity

Ninety-six female and male pigs were assigned to one of three treatments, 'confined' (C),'trained'(T) or 'free' (F) allowing for different levels of physical activity during the growth interval from 30 to 100kg. Treatment C consisted of individual housing in pens of 2.5 m(2); treatment T of individual housing and regular treadmill training and treatment F of housing in pens of 36 m(2) (40 pigs/pen). In m. biceps femoris (BF), the activity of lactate dehydrogenase (LDH) was decreased between 9 and 12% by training (treatment T vs C). Likewise, in BF from female pigs, training increased the activity of citrate synthase (CS) and of 3-OH-acyl-CoA-dehydrogenase (HAD) by 18 and 21%, respectively. Spontaneous activity (treatment F) reduced the activity of LDH for five muscles between 10 and 16% when compared with treatment C. Around the time of slaughter, glycogenolysis of BF was less for treatment F (6-17%) than for C and T (33-38%). Moreover, in BF from female pigs in treatment F, the initial but not the ultimate pH was increased when compared with treatment C. In comparison to C and T, treatment F improved juiciness in BF from male pigs and increased the amount of salt soluble protein in m. longissimus dorsi.     

Comparative lipid composition of porcine muscles at different anatomical locations

The influence of anatomical location on the intramuscular lipids was studied in Large White pigs. The amount of total, neutral and polar lipids and the composition of fatty acids of the above three fractions were determined for Longissimus dorsi (LD) at two points and Transversus abdominis (TA) and Biceps femoris (BF) taken from the two half carcasses of an animal. The symmetrical samples from the same animal had identical intramuscular lipid characteristics. The three muscles did not show significant differences in their total (2·8 to 2·4g/100g) and neutral (2·1 to 1·4g/100g) lipid contents. The amount of polar lipids was characteristic of every muscle (0·65 g, 0·84 g and 0·97 g per 100 g, respectively, in LD, BF and TA). The fatty acid composition of neutral lipids was influenced by the type of muscle. Polar lipid had similar fatty acid composition in the three muscles. The intramuscular lipids contained appreciable amounts of essential fatty acids of the family n-6; interestingly, a part of which (25% of EFA) was the long chain fatty acid (C20 and C22) located in the polar lipids.