A la recherche de marqueurs biologiques de la qualité de la viande

Abstract

Among the sensory qualities of meat, tenderness still the most quality searched by consumers. To achieve this goal, it should put in place all the necessary tools for the assessment of meat quality. It is of course obvious that the first quality to establish is the hygienic one, which today mainly suffers from the lack of a reliable cold chain between the cutter and the consumer. Concerning the meat tenderness, the main problem depends on its strong variability, which is in relation to several factors related or no to the animal. The first part of this thesis focused on sheep. Two batches of lambs were used. The first, consisting of 6 animals was used to search for a relationship between sensory and instrumental measures of tenderness. The second, consisting of 10 animals in order to search the relationships between physicochemical properties and tenderness. The muscles studied were: Semimembranosus, Semitendinosus, Biceps femoris, and Rectus femoris. The kinetic characteristics measured, selected on the basis of their contribution to the definition of meat tenderness are: pH, osmolarity, water holding capacity and the degree of proteolysis. The meat tenderness was measured by penetrometry. The results obtained show clearly that the method of estimating the toughness of the lamb by penetrometer gives values highly correlated with tenderness scores estimated by a sensory panel. In addition, three variables are highly interdependent as pH; osmotic pressure and water holding capacity, all have a discontinuous pattern of change that cannot be explained by current theories advanced to explain the acidification of postmortem muscle. The second part of the thesis is related to the programmed cell death or apoptosis. This process highlighted in 1995, is now relatively well known. The analysis of the consequences of the apoptotic process in relation to the knowledge we obtained in vivo, provide answers to many questions, since a long time, still unclear for all scientists involved in the study of the meat tenderizing process, specifically the step of the maturation. While the involvement of these peptidases does not explain everything, it is likely that its very early intervention is essential to facilitate the action of other proteolytic systems. The investigations of the survey revealed that butchers meat industry is characterized by the search of profitability at all levels. There is a lack of professionalism and training among butchers. In additions, an almost total ignorance of the hygienic quality and taste of the meat is found. The slaughter outside of the slaughterhouse is commonly operated. The ante mortem inspection is very low. The postmortem control concerns 65% only of the carcasses. The low sanitary control is due perhaps for fear of an increase in costs and the risk of seizure or set of carcasses by the veterinarian. In the end, the meat industry requires more sanitary control at all the levels and upgrade training of butchers who seem to be unable to appreciate the quality of the meat