Muscle and meat characteristics from the main beef breeds of the Massif Central
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., 1999; BALCERZAK et al., 2001). Two of them, the calpains and cathepsins, have been studied extensively (OUALI, 1992) and a significant contribution of the 20S proteasome has been shown recently (DUTAUD et al., 2006). Results also indicate that the level of specific inhibitors of those enzymes offer a better indicator of the tenderisation process than the level of the enzymes themselves (OUALI and TALMANT, 1990). The maturation phase depends on the physicochemical factors such as the concentration of cacium ions in the muscle, the osmotic pressure, the processes of peroxidation that are linked to the contractile and metabolic properties of the muscle fibres. It has also been shown that the maturation process is faster in rapid glycolytic fibres than in oxidative fibres (OUALI, 1992). So, because of its multifactorial origin that has not been totally established, it is difficult to control meat tenderness. It was within this context that a 5-year trial was set-up in 1996 and was financed by the Commissariat au Développement Economique and in the Aménagement du Massif Central as part of the XIe Contrat de Plan État-Région. The main aim was to establish the contribution of each muscle component in determining the tenderness of beef. The trial was carried out on young bulls and cull cows from the 4 main breeds of suckler breeds in the Massif Central, namely Aubrac, Charolaise, Limousine and Salers, and provides information on the effects of age, sex and breed on the muscle properties and on the organoleptic quality of the meat.
B PICARD, C JURIE, D. BAUCHART, E. DRANSFIELD, A OUALI, J.-F. MARTIN, R. JAILLER, J. LEPETIT, J. CULIOLI