This study analyzed the abundance of 24 different proteins, tenderness biomarkers, and 11 phenotypic carcass characteristics and muscle properties. This was done on 111 samples of two muscles, Longissimus thoracis (LT) and Semitendinosus (ST) from the Charolais bovine breed. The strategy was to constitute three classes of tenderness on the two muscles separately on the shear-force data (Warner-Bratzler). Then we tested which proteins or phenotypic characteristics explained this classification. Results showed that tenderness classes of ST muscle were well-explained by 12 proteins and 6 phenotypic characteristics. However, for LT muscle the classification could only be explained by 7 phenotypic characteristics. This demonstrates that in ST and LT the variability of beef tenderness is explained by different factors. In ST muscle, the main results of this study demonstrated the importance of Heat Shock Proteins such as Hsp27 (P = 0.002) and the oxidative stress protein: PRDX6 (P = 0.003). We also confirmed the role of Enolase 3, involved in glycolytic metabolism (P = 0.003), and contractile protein such as MyHC IIx (P = 0.028).

The objectives of the study were to evaluate allelic frequencies and to test the association of polymorphisms in the calpastatin (CAST) and mu-calpain (CAPN1) genes with meat tenderness in 3 French beef breeds. A total of 1,114 Charolais, 1,254 Limousin, and 981 Blonde d'Aquitaine purebred young bulls were genotyped for 3 SNP in the CAST gene and 4 SNP in the CAPN1 gene. Two of these markers, 1 in each gene, can be found in Australian or American commercial genetic tests. Others have previously been reported in American studies or are newly evidenced SNP. The quantitative traits studied were Warner-Bratzler shear force and a tenderness score evaluated by trained sensory panels. All the SNP were informative in the 3 breeds. Associations of individual markers or haplotypes with traits were analyzed. The results differed in the 3 breeds. The G allele of a CAST marker (position 97574679 on Btau4.0) was found to exert a significant effect on the shear force (+0.18 phenotypic SD; RSD) and tenderness score (-0.22 RSD) in the Blonde d'Aquitaine breed. In the same breed, this marker was associated with another CAST SNP (position 97576054 on Btau4.0) such that the GA haplotype appeared to be associated with tougher meat. Two CAPN1 markers (positions 45221250 and 45241089 on Btau4.0) had a significant effect on both traits in the Charolais breed (from |0.11| to |0.25| RSD). In the same breed, these markers were associated with another CAPN1 SNP (position 45219395 on Btau4.0) such that the ACA and AGG haplotypes appeared to be associated with a tender meat and a tougher meat, respectively. Consequently, the present results indicate that the effects of the markers studied are breed-specific and cannot be extended to all Bos taurus breeds. Further studies are also required to identify other more appropriate markers for French beef breeds.

The availability of genetic tests to detect different mutations in the myostatin gene allows the identification of heterozygous animals and would warrant the superiority of these animals for slaughter performance if this superiority is confirmed. Thus, 2 mutations of this gene, Q204X and nt821, were studied in 3 French beef breeds in the program Qualvigène. This work was done with 1,114 Charolais, 1,254 Limousin, and 981 Blonde d'Aquitaine young bulls from, respectively, 48, 36, and 30 sires and slaughtered from 2004 to 2006. In addition to the usual carcass traits recorded at slaughter (e.g., carcass yield, muscle score), carcass composition was estimated by weighing internal fat and dissecting the 6th rib. The muscle characteristic traits analyzed were lipid and collagen contents, muscle fiber section area, and pH. Regarding meat quality, sensory qualities of meat samples were evaluated by a taste panel, and Warner-Bratzler shear force was measured. Deoxyribonucleic acid was extracted from the blood samples of all calves, the blood samples of 78% of the dams, and the blood or semen samples of all the sires. Genotypes were determined for 2 disruptive mutations, Q204X and nt821. Analyses were conducted by breed. The superiority of carcass traits of calves carrying one copy of the mutated allele (Q204X or nt821) over noncarrier animals was approximately +1 SD in the Charolais and Limousin breeds but was not significant in the Blonde d'Aquitaine. In the Charolais breed, for which the frequency was the greatest (7%), young bulls carrying the Q204X mutation presented a carcass with less fat, less intramuscular fat and collagen contents, and a clearer and more tender meat than those of homozygous-normal cattle. The meat of these animals also had slightly less flavor. Also in the Charolais breed, 13 of 48 sires were heterozygous. For each sire, the substitution effect of the wild allele by the mutant allele was approximately +1 SD for carcass conformation and yield, showing that the estimate of the substitution effect was independent of family structure, as it ought to be for a causal mutation. These results illustrate the challenge of using genetic tests to detect animals with the genetic potential for greater grades of carcasses and meat quality.

Potential of front-face fluorescence spectroscopy was evaluated to classify muscles according to their chemical and rheological characteristics. Seven bovine muscles (Semitendinosus, Semimembranosus, Tensor fasciae latae, Rectus abdominis, Longissimus thoracis et lumborum, Triceps branchii and Infraspinatus) were taken from 14 animals of the Charolais breed. Chemical characteristics and rheological properties of the meat were determined including dry matter, fat, collagen, protein, peak load, energy required to rupture and cooking loss. Emission spectra in the 305-400nm, 340-540nm and 410-700nm ranges were recorded using front-face fluorescence spectroscopy by fixing the excitation wavelengths at 290, 322 and 382nm, respectively. Analysis of variance (ANOVA) applied on chemical and rheological parameters showed that these muscles were significantly different (P<0.01) from each other. Chemical and rheological data were divided into low, medium and high range groups for each variable. The results of PLSDA showed that 305-400nm spectra were responsible for 67% (calibration), 53% (validation), 96% (calibration) and 55% (validation) of good classification for protein and cooking loss, respectively, while 340-540nm spectra allowed 75% of good classification (validation samples) for fat content.

The fluorescence anisotropy of a rigid medium is a consequence of photoselection of fluorophores and their orientations. This makes it possible to use polarized front-face fluorescence to provide structural information on biological tissues like muscle. Tryptophan is the major intrinsic fluorophore in muscle. It is embedded in proteins which act as building blocks for muscle structuration because of their preferential alignment. Our working hypothesis is that when the arrangement of the proteins changes, there are concomitant changes in fluorescence anisotropy parameters. Our research is directed toward evaluating muscle structure and its evolution post mortem. We report a theoretical simple model of tryptophan fluorescence and an experimental method to measure the fluorescence anisotropy of biological opaque tissues. Instrumental and optical considerations have to be taken into account in experiments on front-face polarization to make certain of measurement accuracy. Therefore, we present a detailed report on the adjustments and corrections made on a conventional L-spectrofluorimeter to adapt it to fluorescence anisotropy measurements on biological tissues. Data from several experiments demonstrate how the method is able to show muscle structure modifications. We show how it is possible to fit experimental data with the model developed in order to obtain structural information.

Tryptophan is the major intrinsic fluorophore in muscle and is a constituent of proteins that have two preferential alignments both parallel and perpendicular to muscle fibre direction. A simple theoretical model and an experimental method based on front-face fluorescence polarization technique for tryptophan fluorescence anisotropy measurements were used for the estimation of post-rigor sarcomere length in beef in the range 1.6-3.4μm. Fluorescence anisotropy and structure-related model variables displayed changes in cold-shortened samples compared with normal and stretched ones. The anisotropy of contracted samples was lowered by misalignment of fibres in the sample. This method can therefore be used for in-line detection of cold shortening which has meat toughness as a consequence.

A vegetal fiber extracted from the Rhectophyllum camerunense plant is presented in this paper. The method of extraction is described and the resulting fibers were uniform with almost circular cross-sections. The density of the new fiber was found to be very low and chemical analysis has revealed that cellulose content is 68.2%. Microscopy observation was used for the measurement of the thicknesses of layers and the microfibril angle of the S2 sub-layer. Tensile tests were performed to measure the mechanical properties of the fiber. The Young’s modulus is nearly the same as for sisal fiber and elongation at break is very high, up to 50%.

This work concerns the relationship between meat tenderness and the rubber-like properties, i.e. pressure and elastic modulus, that endomysium and perimysium connective tissues develop when meat has been heated to a temperature above which collagen contracts. For rest length meats with similar intramuscular connective tissue morphology, and which are at the same ageing state and pH, the elastic modulus of the collagenous fraction of connective tissues is approximately proportional to the total number of collagen cross-links present per volume of meat. Calculations from various published experiments concerned with the effect on tenderness of muscle type, animal age, type, and sex from different species show that this modulus follows most of the variations of meat toughness. Moreover, the proportionality between the increase in this elastic modulus and the increase in meat toughness approaches unity in situations where toughness mainly depends on connective tissues. This work demonstrates the decisive role of rubber-like properties of connective tissues in meat tenderness variations.

The aim of this work was to evaluate the mechanical, structural and geometrical changes caused by cold shortening in cooked meat. Non-contracted and contrac...

The aim of this work was to evaluate the mechanical, structural and geometrical changes caused by cold shortening in cooked meat. Non-contracted and contracted samples of Semimembranosus muscle from 4 animals (6 year old, cows) were used. These samples were cooked at temperatures of 50, 55, 60 and 70 degrees C for 90 min. Tensile tests indicated that at 50 degrees C, contracted meat was tougher than the non-contracted meat. At 55 degrees C a reduction in toughness was only observed in non-contracted meat. Above 60 degrees C, the contracted meat was significantly tougher than the non-contracted meat (p<0.05). Geometrical (surface and diameter) and structural (sarcomere length) characteristics decreased in both cases. Collagen solubility reduced in the case of contracted meat and this diminution explains partially the toughness differences observed in both samples.

Although beef consumption in France has recovered to the level before the 2 BSE crises, consumers remain unsatisfied with organoleptic quality, in particular with the large variability in the tenderness and flavour.This presents a major problem to the beef industry faced with competition from white meats offering a better retail quality/price ratio.Research in the last few years has shown that the variability is a consequence of animal factors (breed, sex, age), the production conditions (HOCQUETTE et al., 2005), and of the slaughtering and maturing conditions (CULIOLI, 1999).The organoleptic qualities depend on the composition and structural properties of the muscle, particularly the two main components: the connective tissue and myofibres.The connective tissue is composed essentially of collagen, and its content, nature and heat solubility in water determine meat tenderness (LEPETIT, 2004).These criteria are the basis for the three cooking classes of beef: stew, braise and roast/grill.The muscle fibres, that form most (≈85%) of the muscle volume, are classified on the basis of their contractile (fast or slow contracting) and metabolic properties (glycolytic that uses mainly carbohydrates as the source of energy and oxydative using mainly fatty acids).In adult cattle three types of fibres are present: SO (slow oxidative), FOG (fast oxido-glycolytic) and FG (fast glycolytic) (PICARD et al., 2003).These types are present in different proportions in different muscles.Meat tenderness depends not only on the muscle properties but also on the phase of maturation.Maturation is a complex multifactorial process that affects mainly the myofibrillar structure and depends on several ante-and post-mortem factors.It is essentially an enzymatic process (OUALI, 1992) in which endogenous proteases act on the contractile proteins and on the components of the cytoskeleton (HUFF-LONERGAN and LONERGAN, 1999).The proteolytic systems comprise the metallopeptidases (Matrix Metalopeptidases or MMPs), the calpains, the cathepsins, the proteasome and the serine peptidases (GOLL et al.,

This work provides an explanation of meat tenderness variations based on the rubber-like properties (pressure and elastic modulus) that endomysium and perimysium connective tissues develop above the temperature of collagen thermal contraction. Both pressure and elastic modulus are functions of the total number of collagen cross-links per volume unit of meat sample. The variations in pressure explain the relationships between meat tenderness and both muscle fibres diameter and muscle fibre bundles diameter and the inversion of these relationships according to meat type (beef, sheep, pork, poultry, fish). For rest length meats with no significant variations in the muscle fibres diameter, muscle fibre bundles diameter, pH, collagen fibres and collagen fibrils waviness and which are at the same ageing state, then the total number of collagen cross-links explains the variations in tenderness, observed after mild heating, and produced by muscle type, animal age, type and sex for any given species. This theory demonstrates the decisive role of rubber-like properties of connective tissues in meat tenderness variations.

For consumers, tenderness is the most important sensory attribute of beef meat and, though to a lesser extent, of pork. Tenderness is therefore by far the most common cause of its unacceptability. The major challenge for the beef industry is to evaluate the toughness of the meat as soon as possible after death. In this context, the aim of the present work was to develop an equation to predict the myofibrillar ultimate resistance of raw meat.The study was done on the Longissimus muscle from twenty three 19 months-old Charolais bulls grown in the same INRA farm. Muscles excised within 1 h post-mortem were vacuum packed and stored at 15 degrees C during 24 h and then transferred to 4 degrees C until used. The activities of lactate dehydrogenase, citrate synthase and myofibrillar Mg-Ca dependent ATPase, the levels of lactate dehydrogenase enzyme, myoglobin, myosin types 1, IIa and IIb, cysteine and serine peptidase inhibitors, the pH, the osmolarity, the expressible juice, mu-calpain, in-calpain and calpastatin and meat toughness were measured. According to the physical method used here, the force measured on raw meat represents the resistance of the myofibillar structure.Stepwise linear regression was used to determine the best equation (p < 0.05) for predicting toughness at 6 days post-mortem. A 6-variables predictive equation including serine peptidase inhibitors (partial R-2 = 0.4), the rate (partial R-2 = 0.25), and the extent of pH decline (partial R-2 = 0.03), the at death LDH activity (partial R-2 = 0.24), the extent of increase in osmotic pressure (partial R-2 = 0.13), and the rate of mu-calpain activity loss (partial R-2 = 0.09), explained 70% of the variability in meat toughness at 6 days post-mortem. This equation was developed from 20 animals and the other 3 animals, chosen randomly, were used to validate it. The absolute need for a predictive model of meat toughness and the nature of the serine peptidase inhibitors together with their potential target enzymes are discussed. (C) 2005 Elsevier Ltd. All rights reserved.