De electricitatis catholici musculari - Concerning the electrical properties of muscles, with emphasis on meat quality

This study aims to explore the potential of evoked non-invasive surface electromyography (SEMG) analysis, in predicting meat quality traits in livestock. Evoked SEMG is a system that records, transdermally, electrical signals generated in muscle fibres upon external stimulation. These signals are reported as compound muscle action potentials (CMAP). CMAP parameters of LD correlated negatively and significantly to ultimate pH (pH 24 h) at day 61, but not at day 153 after birth, and a similar albeit positive correlation was observed for muscle glycogen content. Muscle glycogen content and pH 24 h correlated negatively in LD and BF. Negative significant correlations between CMAP parameters and shear force were found in LD at day 153 after birth, which might, in the range of the recording electrodes, reflect the combined effect of large cross-sectional area fibres and reduced perimysium content per unit volume of muscle. The fact that correlations between CMAP characteristics and quality traits of both metabolic and non metabolic origin could be established, warrants a fuller investigation of this method in terms of its potential as a predictive tool for meat quality traits in live animals.     

The effect of dietary CLA supplementation on meat and eating quality, and the histochemical profile of the m. longissimus dorsi from stress susceptible fatteners slaughtered at heavier weights

The influence of adding 2% CLA to the morning feed of a group of 20 crossbred fatteners from 70 to 130 kg on meat quality, eating quality and dietetic value of m. longissimus dorsi was evaluated compared with a group of 20 controls. Addition of 2% CLA in feed did not influence fattening and slaughter results and also some traits of meat and eating quality. The only significant differences were observed in dry matter content, in meat flavour and L^*, b^*, and hue angle value. Meat from fatteners from the experimental group had a statistically significant higher content of CLA (P0.01) and lower content of unsaturated fatty acids especially C18: 2, C18: 1 and C20: 4, PUFA fatty acids (P0.01) and a reduction in the ratio of n-6: n-3 PUFA (P0.01). No statistically significant influence of CLA on the content of cholesterol was observed. The results of the current histochemical study showed that dietary CLA supplementation significantly increased both the number and diameter of white fibres, and correspondingly reduced the number and diameter of red fibres. The percentage and diameter of intermediate fibres was unaffected by CLA.     

Kinetics of protein physicochemical changes induced by heating in meat using mimetic models: (2) Effects of fibre type,peroxides and antioxidants

Heating-induced changes in meat proteins were investigated using models made of aqueous suspensions of myofibrils according to muscle fibre types and cellular compounds (oxidants and antioxidants). These changes were evaluated by measurements of carbonyl groups and protein surface hydrophobicity. Model results were compared to trial results obtained on pork meat (M. Longissimus dorsi) heated under the same conditions (45 and 75 °C, from 5 to 120 min). Myofibrillar proteins from α-white fibres were more sensitive to oxidation and thermal denaturation than those from β-red fibres. At 45 °C, there were negligible differences due to peroxide or antioxidant types. At 75 °C, organic peroxides (ROOH) were less oxidative than hydrogen peroxide (H₂O₂), and antioxidant enzymes were less efficient than vitamin E and carnosine at protecting proteins against oxidation. Protein oxidation observed in meat is lower than in the mimetic models and the increase in hydrophobicity remained limited in meat.     

Characteristics of low‐fat beefburgers as influenced by various types of wheat fibres

Hydrated wheat fibres (bran and white and red beeswings) were added at three levels (50, 100 and 150 g kg⁻¹ ) to beefburger as replacement for fat and evaluated for chemical and physical properties, energy content and sensory traits. Uncooked and cooked beefburgers formulated with wheat fibres had higher (P⩽0.05) moisture, protein and carbohydrate contents and lower (P⩽0.05) fat contents than that of the control. However, ash content was increased (P>0.05) by the addition of wheat fibres. The cholesterol content of uncooked and cooked beefburgers decreased as level of wheat fibres increased or fat content decreased. The addition of wheat fibres reduced the cholesterol content from 6 to 45% for uncooked and cooked beefburgers. The energy content of uncooked and cooked beefburgers was lower (P ⩽0.05) than that of control by between and 6 and 41%. The cooking yield and reduction in diameter of beefburgers were significantly (P⩽0.05) improved by the addition of wheat fibres. The addition of red and white beeswings showed an improvement in the texture trait. Colour traits, tenderness, juiciness, connective tissue amount, beef flavour intensity and overall palatability were not affected by the addition of wheat fibres to beefburgers. Hydrated wheat fibres can be used successfully as a fat substitute in ground meat products. © 1999 Society of Chemical Industry     

Elastin in bovine Semitendinosus and Longissimus dorsi muscles

The structural organization of elastin present in bovine semitendinosus and longissimus dorsi muscles was examined using light and scanning electron microscopy. Qualitatively, both muscles were found to have the same organization of the two structural forms of elastin present.

Coarse elastin fibres (5–10 μm diameter) were found in the epimysium and perimysium, aligned with the long axis of the muscle fibres. In addition, finer elastin fibres (1–2 μm diameter) were found in the epimysial and perimysial sheets of collagen. These finer elastin fibres approximated the course of the collagen fibres, i.e. at an angle to the muscle fibre long axis.

Quantitatively, the semitendinosus muscle epimysium and perimysium contained very heavy deposits of the coarse elastin fibres and nearly every sheet of perimysium, even the thinest, contained the fine elastin fibres. By comparison, less of the coarse elastin was present in the longissimus dorsi epimysium and it was quite rare in the perimysium. The finer elastin fibres were, however, reasonably common.

The significance of this structural arrangement is discussed in relation to muscle function and to meat toughness assessment.     

Muscle glycogen depletion pattern in halothane-gene-free pigs at slaughter and its relation to meat quality

Muscle fibre type composition and glycogen depletion pattern at slaughter as related to meat quality, were studied in M. longissimus dorsi of halothane-gene-free Swedish Yorkshire pigs fed a high (n=19; 10 entire males and 9 gilts) or a low (n=18; 10 entire males and 8 gilts) protein diet. The muscle consisted of, on average, 8% type I, 9% type IIA and 83% type IIB fibres. Muscle fibre areas were significantly smaller in entire male pigs than in gilts irrespective of fibre type. There were no marked differences in muscle characteristics between pigs fed the low and high protein diets. Low glycogen concentrations were found in most type I and type IIA muscle fibres, while a greater variation in glycogen content was evident in type IIB fibres. The pigs were divided into two groups according to the proportion of glycogen depleted IIB fibres (more or less than 30% depleted IIB fibres). In the group where 30% or more of the type IIB fibres were glycogen depleted, a tendency toward DFD meat (dry, firm, dark) was seen, as the meat had higher ultimate pH (5·62 vs 5·52; p=0·02), lower drip loss (2·7% vs 4·4%; p=0·007) and lower reflectance value (darker meat; 16·5 vs 20·6 EEL units; p=0·0005), compared with the group with less than 30% depleted IIB fibres. No difference in total glycogen content was found between these two groups. This indicates that the distribution of glycogen in different fibre types seems to be of importance for the ultimate meat quality.     

Beef sausage structure affected by sodium chloride and potassium lactate

A histological and ultrastructural study was conducted to characterize changes in the muscle fibre structure of three fresh sausage preparations, depending on meat composition, sodium chloride (NaCl) and potassium lactate (K-lactate) contents. After addition of 0.8% and 1.6% NaCl, 65% and 51%, respectively, of the area observed showed well preserved fibres (histological data). The altered regions presented a large disorganization of the myofilaments and a solubilization of the sarcolemma and of the Z lines. K-lactate addition had no marked effects on meat structure. The preparation containing some sheep meat was more sensitive to salt than the others containing only bovine meat. The level of alteration was much lower than those obtained in pork meat in another study. Technological conditions used to modify the internal muscle fibre structure during sausage processing depend on the species used. Therefore, the classification of the sausage preparation to “meat preparation” or “meat product” under the EU regulation (EC) No. 853/2004 (which assign meat preparations to meat if the product has undergone a process insufficient to modify the internal muscle fibre structure of the meat) must be systematically controlled when changing the meat sausage composition.     

A comparison between tensile and shear adhesive strength of meat-myosin junctions

A model meat-myosin gel junction was used to compare the adhesive strength of binding junctions when subject to tensile or shear forces. This comparison was made on junctions cooked to 80°C with three different alignments of muscle fibres with respect to the junction plane. Tensile adhesive strength (TAS) and shear adhesive strength (SAS) did not differ significantly when fibres in both of the bound pieces of meat were perpendicular to the plane of the myosin gel function (90°/90° junction). However, SAS was higher than TAS if the muscle fibres in one or both of the meat pieces were parallel to the plane of the junction. This suggests that tensile failure of binding junctions is the more likely mode of failure. Differences between SAS and TAS in any one junction orientation were small compared to the effect of muscle fibre orientation with respect to the junction; both TAS and SAS were highest for 90°/90° junctions and lowest when muscle fibres in both meat pieces were parallel to the junction (0°/0° junctions).     

Comparison of carcase yield, carcase composition and quality characteristics of buffalo meat and beef

The yield of carcase and by-products was found to be only slightly different between buffaloes and non-improved (Busha) cattle of comparable age, feeding treatment and sex. The percentage of separable fat was slightly higher, and that of bone slightly lower, in the buffaloes. In comparing the meat from buffalo and Simmental cattle of the same age and finish, a rather higher protein content was found in the former, but this reflected a somewhat higher concentration of connective tissue in the buffalo meat. The diameter of muscle fibres in buffalo tended to be less than that of corresponding muscle in Simmental cattle (except in M. Supraspinatus of cows). These findings suggest that buffalo meat is no coarser than beef when valid comparisons are made.     

The effect of pre-rigor stretch and contraction on the post-rigor geometry of meat samples in relation to meat toughness

The geometry of the muscle fibre and perimysial collagen components of meat subjected to pre-rigor stretch and contraction were examined. The changes in the configurations of these two components accompanying length changes in the muscle were used to explain the reported relationship between raw meat toughness and contraction state. The theory put forward proposes that in raw meat samples the muscle fibre component plays virtually no role in modifying the toughness of the meat sample with contraction state. This theory of the collagen component playing the major role is the same as that reported elsewhere. It is capable of explaining a reverse relationship between meat toughness and contraction state such as is found in cooked meat simply by invoking a firmer consistency for the muscle fibres which then act as fill between the collagen network fibres and hold them at an angle relative to the line of applied force.     

Tenderization effect of cold-adapted collagenolytic protease MCP-01 on beef meat at low temperature and its mechanism

The enzymes currently used to increase meat tenderness are all mesophilic or thermophilic proteases. This study provides insight into the tenderization effect and the mechanism of a cold-adapted collagenolytic enzyme MCP-01 on beef meat at low temperatures. MCP-01 (10 U of caseinolytic activity) reduced the meat shear force by 23% and increased the relative myofibrillar fragmentation index of the meat by 91.7% at 4 °C, and it also kept the fresh colour and moisture of the meat. Compared to the commercially used tenderizers papain and bromelain, MCP-01 showed a unique tenderization mechanism. MCP-01 had a strong selectivity for degrading collagen at 4 °C, showed a distinct digestion pattern on the myofibrillar proteins, and had a different disruption pattern on the muscle fibres under scanning electron micrograph. These results suggest that the cold-adapted collagenolytic protease MCP-01 may be promising for use as a meat tenderizer at low and moderate temperatures.     

Effect of high-oxygen atmosphere packaging on mechanical properties of single muscle fibres from bovine and porcine <Emphasis Type="Italic">longissimus dorsi</Emphasis>

The effect of storage in high-oxygen atmosphere packaging for 48 h at 4 °C on the myofibrillar component of meat toughness was studied performing tensile tests on single muscle fibres, isolated from beef and pork longissimus dorsi (LD). Storage of bovine LD for 48 h in the presence of oxygen significantly increased the breaking strength of single muscle fibres when compared with storage in a 100% nitrogen atmosphere. In contrast, the breaking strength of porcine LD stored for 2 days post-mortem in the presence of oxygen in the packages was not influenced.     

Effect of slaughter weight and/or age on histological characteristics of pig longissimus dorsi muscle as related to meat quality

The effect of increasing both weight and age or age alone through feed restriction on muscle longissimus dorsi histological characteristics were studied in relation to fresh and cooked meat quality. Starting at 83 days (32 kg) 80 crossbred Duroc × (Large White×Landrace) barrows were allotted within litter to 4 experimental groups (A100, R100, A130, R130). Pigs were fed either ad libitum (A) or were restricted 30% (R) and slaughtered either at 100 kg or 130 kg. Muscle fibres were classified as βR, αR or αW according to Ashmore and Doerr (1971)(Ashmore, C.R., &; Doerr, L. (1971). Comparative aspects of muscle fibre types in different species. Experimental Neurology, 31, 408–418.). Percentages (PC), cross-sectional areas (CSA) and relative areas (RA) of each fibre type were evaluated. Phenotypic correlations between histological traits showed that RA of a particular fibre type depends essentially on its numerical abundance. Increasing weight together with age led to enlargement of βR and αW muscle fibres, without changing muscle histochemical profile. When age was increased at the same weight (restriction), higher RA of βR fibres was observed. Low, but significant correlation between loin eye area and CSA was observed, but not within experimental group. The phenotypic correlations between histological and meat quality traits were generally low. This material showed some significant correlations suggesting that increasing PC or CSA of overall αW fibres can be beneficial for water holding capacity of fresh meat and juiciness of cooked meat. ©     

Specificity of different anti-myosin heavy chain antibodies in bovine muscle

Muscle fibre types play an important role in bovine meat tenderness, and conditions the speed of ageing. Two generations of myotubes appear during foetal life. Their differentiation results in several types of fibres differing in their contractile and metabolic properties, namely type I fibres and type II fibres (IIA and IIB). Fibre types were identified using antibodies by immunohistochemistry and western-blotting techniques. The aim was to test different antibodies on foetal and adult muscles by these two techniques. Ten monoclonal antibodies reported to be specific to different myosin heavy chain (MHC) isoforms in other species were tested. Only three antibodies were selected: BF.35, specific for I and IIa MHCs, F1.652 specific for foetal MHC and SC.71 an anti II MHCs (IIa and IIb) antibody. The use of these antibodies will enable a more precise characterisation of muscle fibres and will have applications in the study of bovine muscle ontogenesis.     

Meat quality and muscle fibre type characteristics of Southdown Rams from high and low backfat selection lines

Characteristics of the meat of 15-18-month Southdown rams from lines selected for high or low backfat depths (assessed ultrasonically at position C over the last rib) were compared. Half of the carcasses were electrically stimulated (ES) and within each carcass post-mortem treatments chosen to produce effects on meat tenderness were ageing periods of 1 or 15 days (Semimembranosus), early or delayed chilling (Biceps femoris), and trimming of the s.c. fat cover (Longissimus dorsi). These treatments had the expected effects on shear values, but the sizes of the effects were little affected by selection line or ES treatment. Selection line did not have any direct effects on shear values, reflectance values at several wavelengths, waterholding capacity, cooking loss or sarcomere length. The Semitendinosus muscle had a higher proportion of predominantly oxidative fibres for the high-backfat line, based on succinic dehydrogenase activity (P < 0·05), but there was no line difference in alkaline-stable ATPase activity in the same muscle. Muscle fibre diameter was similar for the two lines.     

Degradation of inosine-5′-monophosphate (IMP) in aqueous and in layering chicken muscle fibre systems: Effect of pH and temperature

Studies were carried out to assess the effect of pH and temperature on the degradation of major meat flavour precursor inosine mono-phosphate (IMP) in model systems. Breast and leg muscles from Indian domesticated layer chicken (Gallus gallus) were washed repeatedly with 0.1 M phosphate buffer of pH 6 to obtain pigment-free muscle fibres. Degradation of IMP in water and in muscle fibre-IMP systems were studied at 80, 100, and 120 °C under three pH (2, 7 and 11) conditions. The pH of muscle fibres was 6.2-6.4. The IMP content (mg/100 g) of fresh breast muscle (188.5) and its fibre (7.9) were higher (P?0.05) than fresh leg muscle (135.2) and its fibre (1.9). Inosine and hypoxanthine contents were also higher in breast than in leg muscles and their fibres. Degradation of IMP in both model systems was significantly influenced by pH and thermal treatment. In water systems, the degradation of IMP increased with temperature. Acidic pH caused greater degree of degradation than neutral or alkaline pH.     

The influence of post-mortem ageing and roasting on the microstructure, texture and collagen solubility of bovine semitendinosus muscle

Bovine semitendinosus (ST) muscles aged for 5 and 12 days at 4?°C were roasted at 170?°C to internal temperatures of 50, 60, 70, 80 and 90?°C. Microstructural changes in meat were evaluated using a scanning electron microscope (SEM). Texture profile analysis (TPA) and measurements of the shear force values of samples were conducted using a texture analyser. The cooking losses and quantity of total and soluble collagen were also estimated. The structure of intramuscular connective tissue and myofibrillar structure of meat after 5 days of ageing was very regular. In 12-day-aged samples fibrous and myofibrillar structures were less distinct, damages of endomysium tubes appeared and fibres of perimysium were swelled. Ageing of ST muscle for 12 days caused a two-fold increase in the quantity of soluble collagen and a two-fold decrease in the value of TPA parameters-hardness and chewiness, as compared to 5-day-aged samples. The decrease in fibre diameter and sarcomere length during roasting started at 60?°C in 5-day-aged meat and at 50?°C in 12-day-aged samples. The shear force values measured after roasting were lower for 12-day-aged meat than for 5-day-aged samples. The quantity of soluble collagen in roasted meat increased at an internal temperature of 80?°C. At a higher temperature of meat this variable depended on the degree of meat ageing. The cooking losses during roasting of meat were about 3% lower for 12-day-aged than for 5-day-aged samples. In the examined range of internal temperature of meat the cooking losses and the sarcomere length were negatively correlated.     

Relationship between histochemical, structural characteristics and oxidative stability of rhea limb muscles

Histochemical and structural characteristics were investigated in Gastrocnemius pars interna (GN) and Iliofiburalis (IF) limb muscles of Rhea americana. The average myofibre area cross-section was greater in GN than IF muscle (p < 0.001), whereas the fibre density per section was higher in IF than GN muscle. The only type of myofibre found in both the rhea limb muscles analysed in this study was fast-twitch oxidative-glycolytic fibres (FOG). Immunolabelling analysis and ultrastructural observation of myofibres confirmed the contractile and metabolic characteristics of rhea myofibres, revealing the absolute fast isoform of myosin heavy chain and the abundance of glycogen and mitochondria inside the cells, mainly in IF muscle. These findings converged with previous results on the biochemical and physicochemical characteristics of rhea meat to provide further evidence that myofibre composition substantially influences the oxidative reactions of the muscle and therefore the meat quality, but more in-depth examination is needed to establish the links between myofibre characteristics, myofibre glycogen concentration and meat stability during storage.     

Theoretical strain ranges in raw meat

Rheological data obtained in a compression test of raw meat samples are expressed on the basis of actual meat length ratio which takes into account pre-rigor strains, during contraction or stretching, and post-rigor strains occurring during post-rigor contraction or during the compression test. The relationship between the deformation of collagenous fibres and that of meat sample gives the critical compression ratio at which the collagenous fibres undergo tension. A theoretical curve is given to explain the variation in the critical compression ratio with initial state of sample. The curve is used to define theoretical strain ranges in which predominantly one structure (muscle fibres, elastin fibres or collagenous fibres) is involved and consequently can be analysed.     

Meat quality and carcass traits in relation to HGD-BstXI and HGD-HaeIII PCR–RFLP polymorphism in Chinese red cattle

We investigated the effect of homogentisate 1, 2 dioxygenase (HGD) gene on meat quality and carcass traits in 287 Chinese red cattle. The PCR–SSCP method was used to identify polymorphism of the HGD gene in the exon 1 and intron 1. Two polymorphisms were detected in intron 1 and two restriction sites for endonuclease HGD-BstXI and HGD-HaeIII have also been found. The HGD-BstXI genotypes showed significant effects on cooking loss, drip loss, net meat weight, carcass weight, and eye muscle area (P < 0.05). The HGD-HaeIII genotypes significant affected cooking loss, muscle fibre diameter, shear force, drip loss, and carcass yield ratio (P < 0.05). Moreover, we found significant effects of diplotypes on cooking loss, muscle fibre diameter, shear force, drip loss, net meat weight, carcass weight, and eye muscle area (P < 0.05).