Philippe Berge

Relationships between muscle characteristics and meat quality traits of young Charolais bulls

Charolais bull calves (106) were used to study the variability in meat quality attributes in relation to the variability in muscle characteristics in the Longissimus thoracis (LT) muscle. The variability in traits was adjusted either to constant age or constant weight at slaughter and thus originated only from differences between animals born, reared and fattened in the same location. The following meat quality attributes were measured: the strength of the myofibrillar resistance to a 20% compression strain measured on the raw meat 2, 7 and 21 days post mortem; and taste panel scores of tenderness (initial and overall), flavour and juiciness of steaks grilled to a 55°C core temperature 6 or 15 days post-mortem. The following muscle characteristics were measured 24 h after slaughter: pH, dry matter, protein, lipid, heme iron and collagen contents, collagen solubility, LDH and ICDH activity, the proportion of slow twitch myosin heavy chain, the mean muscle fibre area and the mean sarcomere length. One fourth to one third of the variability of 2 day mechanical strength and 15 day tenderness or flavour scores were related to the variability in muscle characteristics. Tenderness and strength measurements were predominantly related to the muscle fibre area, collagen characteristics and energetic metabolic activity. Dry matter content was the principal muscle characteristic related to flavour.

Effects of high-intensity high-frequency ultrasound on ageing rate, ultrastructure and some physico-chemical properties of beef

High-intensity and high-frequency ultrasound was tested for its ability to accelerate meat ageing and increase beef tenderness. Samples (≈50g) of semimembranosus muscles from 8 cull cows were assigned to ultrasonic treatment (2.6MHz; 10W/cm(2); 2 ×15s) either pre-rigor (day 0, pH 6.2) or post-rigor (day 1, pH 5.4). When applied pre-rigor, ultrasound induced a slight delay in rigor mortis onset, a stretching (12-15%) of the sarcomeres (p<0.05), an ultrastructural alteration in the Z-line region and an immediate increase (around 30%) in the release of calcium in the cytosol (p<0.05). However, no conclusive effect on meat ageing rate was observed. Post-rigor ultrasonic treatment did not induce any structural modification but slightly improved the ageing index after 6 days (p<0.05). However, no improvement in the final (day 14) ageing index was observed compared to the controls. As ultrasound had also no effect on the thermal stability of collagen, at both postmortem times, no improvement in meat tenderness can be expected under the conditions used.

Tenderization of beef by lactic acid injected at different times post mortem

The potential to tenderize beef muscles by the injection of lactic acid (0.5 M, 10% w/w) was studied using the pectoralis profundus muscle from cull cows. The injection was performed either 1 h (pre rigor) or 24 h (post rigor) post mortem, and the meat was stored for 2 or 14 days post mortem. Both treatments caused a rapid pH drop to around 5.0 within 4 h of injection. Other effects were: (1) an accelerated release of lysosomal enzymes into the cytosol; (2) a greater degradation of myosin heavy chains; (3) ultrastructural alterations of the myofibrils which included a general weakening or rupture in the M-lines and, to a lesser extent, in the I-bands; (4) a decreased heat stability of perimysial collagen indicated by a lower insoluble collagen content, lower differential scanning calorimetry transition temperature, and lower transition temperatures in isometric tension tests on muscle strips. The lactic acid injections improved significantly the textural traits of the meat (shear value, tensile strength, sensory scores) at 2 days post mortem with little further improvement when storage was extended to 14 days post mortem. Changes in texture were of similar amplitude at both post mortem injection times. The tenderization mechanisms of lactic acid injection are discussed.

Perimysial collagen crosslinking and meat tenderness in Belgian Blue double-muscled cattle

The relationship between intramuscular collagen and five collagen crosslink concentrations, and the tenderness of meat from Belgian Blue normal, heterozygous double-muscled (DM) and homozygous DM cattle was investigated using M. semitendinosus (St) and M. gluteobiceps (Gb). The histidinohydroxymerodesmosine (HHMD) concentration (per mol collagen) in St was less in DM animals than normal animals. Concentrations (per gram of wet meat) of HHMD and Erlich chromogen (EC) in Gb, and HHMD, EC, dihydroxylysinorleucine (DHLNL) and hydroxylysinorleucine (HLNL) in St were also lower in DM animals than normal animals. Shear force of raw meat was significantly greater in normal animals than DM for both muscles; cooked meat shear force was greater in the normal animals for the Gb muscles only, showing a good correlation with sarcomere length. Most correlations between shear force and collagen or crosslink concentrations were not significant and those that were highly significant were generally weak.

Meat texture of lambs from different European production systems

Measurements of meat texture (Warner-Bratzler shear force, WBSF), compression stress at 20% (S20) and 80% (S80) of initial sample thickness, sarcomere length, pH, and sensory tenderness score were determined on the longissimus muscle from lambs from 22 diverse European lamb types from 6 countries. Carcasses chilled to minimise cold shortening. The types ranged from 1-month-old milk-fed lambs to 1-year-old heavy wether lambs reared on the transhumance system (extensive system based on moving animals from valleys to high mountains in search of seasonal resources). Overall, it seems that breed was more important in influencing meat toughness than age or gender. Within breed, there was some evidence of an age effect (the older the animal the tougher the meat), and nutritional handling was, in some cases, significant. The lowest WBSF values were for meat from 16-kg carcasses of pasture-fed animals of the Icelandic breed (average 1.7 kg) and the highest were for meat from 19–20 kg carcasses of the Bergamasca breed (average 4.1 kg). The two youngest types had the highest values for S20 (10.5 and 11.8 N/cm2), the compression value related to myofibrillar component. There was a very good agreement between panels from the different countries in the ranking of tenderness; meat from the Icelandic breed was the most tender and that from the Bergamasca breed the least, in concurrence with the WBSF results, with a significant relationship between tenderness and WBSF values in all the lamb types studied.

Meat quality traits in the emu (Dromaius novaehollandiae) as affected by muscle type and animal age

Meat quality traits were determined in the major muscles of the emu (Dromaius novaehollandiae) at different slaughter ages (6, 10, 14, 17 or ≥20 months). A mean ultimate pH value of 5.5 was reached within around 3 h post mortem, but this value was 6.1 in animals that had suffered a preslaughter stress (transportation and fasting). The collagen and pigment contents varied widely among the muscles. The protein and pigment contents increased with animal age, but this effect was perceptible only between 6 and 14 months. The other chemical constituents were little affected by muscle type or animal age. The intense red colour of emu meat, due to a high pigment content, was very sensitive to oxidation, thus limiting the storage of fresh meat under aerobic conditions to short periods of time. Despite a rapid post-mortem tenderization (≤24 h), the residual myofibrillar strength obtained after extended ageing remained intermediate between those reported for chicken and beef. The tenderness of meat, cooked to 60 °C, differed between muscles and decreased with increasing age, thus reflecting the changes occuring in the concentration and in the heat stability of the intramuscular connective tissue.

Magnetic resonance imaging of connective tissue: a non‐destructive method for characterising muscle structure

A magnetic resonance imaging technique based on susceptibility-induced contrast was used to visualise the spatial distribution of connective tissue in meat. Magnetic resonance imaging of bovine meat samples was carried out with a high-field 4.7 T imager. Magnetic resonance images obtained with spin-echo and gradient-echo sequences were compared to elucidate the role of connective tissue in the additional signal losses observed in the gradient-echo images. maps were reconstructed from the multiple gradient-echo images, which provide quantitative information. Comparison with histological pictures indicates that these maps exhibit the overall organisation of the primary perimysium at the scale of the whole muscle. The distinct perimysial organisation shown between the Gluteo biceps and Pectoralis profundis muscles illustrates the potential of magnetic resonance imaging for characterising the muscle connective tissue structure. © 2000 Society of Chemical Industry

Effects of muscle texture on ultrasonic measurements

In this study bovine muscle samples were analysed using an ultrasonic method to investigate the influence of compositional and textural characteristics on ultrasonic measurements. The ultrasonic method was based on the measurement of acoustic parameters (velocity, attenuation and backscattering intensity) which are closely related to physical properties of the propagating medium. An examination of physical parameters was proposed by two types of representations: a mean profile and a parametric image. Two muscle types, which differ in composition and structure were studied. On the same samples additional measurements, mechanical resistance and chemical composition, were performed and used to show the influence of meat composition and texture on ultrasonic data.

Effect of feed protein on carcass composition and meat quality in steers

Forty-five Charolais steers were fed one of four experimental regimes containing maize silage and maize grain supplemented with either protected soyabean-rapessed meal or linseed meal. The first three regimes were formulated to supply the same energy and different protein levels with soyabean-rapessed meal: low (L-SRM), medium (M-SRM) and high (H-SRM). The fourth regime consisted in feeding the same amount (kg/day) of linseed meal as that of soyabean-rapessed meal in the H-SRM regime (LSM). As the protein level increased from L-SRM to H-SRM, the daily weight gain of steers increased and the carcass composition was changed towards higher muscle and lower fat proportions. Though the actual supply of feed protein by regime LSM was close to that achieved with M-SRM, the effect of linseed meal supplementation on weight gain and carcass composition was comparable to that obtained by feeding the high protein level (H-SRM). The dry matter content increased and the heme pigments and lipids contents decreased in longissimus thoracis muscle as the protein supply increased from the low to the high level. Again the amplitude of the differences in meat quality with L-SRM were similar in H-SRM and LSM. Muscle colour, connective tissue and mechanical strength remained practically unaffected by the protein treatments. However, meat was scored less tender in H-SRM and less juicy in treatment LSM than in treatment L-SRM. The results obtained with linseed meal suggest a specific effect of type of feed protein on beef carcass composition and meat quality.

A global unimodal thresholding based on probabilistic reference maps for the segmentation of muscle images

Abstract A global probabilistic maps thresholding (PMT) method was applied to characterise intramuscular connective tissue (IMCT) distribution on images of muscle histological sections exhibiting unimodal histograms. Probabilistic reference maps were defined and then used to set-up thresholding rules, derived from linear combinations of parameters calculated from the intensity histogram of the images. This PMT method was objectively compared to Rosins unimodal thresholding algorithm (RT) and validated by a histochemical quantification of IMCT collagen. Morphometrical parameters of the IMCT (area, length and thickness of the extracted network) were determined for different muscles and used to quantify IMCT distribution differences.