Post mortem metabolism and meat qualities : how proteomics can bring new information
Muscle post mortem metabolism may be defined as the whole set of biochemical processes occurring between animal death and the final processing of meat before consumption. The most documented post mortem events are glycolysis, leading to lactate accumulation and pH decline, lipid oxidation and modifications of proteins, namely denaturation, proteolysis and oxidation. Numerous factors influence the nature and/or extent of post mortem metabolism, depending on the animal (genetics, rearing conditions and feeds, reactivity to slaughter stress etc.) or on the technology used: stunning method, chilling of carcases, packaging etc. (LEBRET et al., 2002, TERLOUW et al., 2005). Studies on post mortem metabolism classically focus on one type of reaction, and are based on the quantification of one or a few effectors or products of that reaction. For example, glycolysis is studied by quantifying selected enzymes in the pathway, or by measuring a resulting characteristics (pH, lactate concentration...). Proteolysis is investigated by quantifying proteases and their inhibitors, or by observation of proteolytic profiles. However, all events interact with each other, and it is the result of the interaction that determines technological (e.g. water-holding capacity), sensory (flavour, tenderness, juiciness) or nutritional properties of meat. This justifies the use of global methods such as proteomics or metabolomics. Proteins are key elements in post mortem metabolism, firstly because they constitute a target of chemical (proteolysis, oxidation) or structural (denaturation) modifications but also because they are the mediators of all biochemical reactions, may they be enzymes, inhibitors of regulatory proteins. Thus, in this communication, we will present the influence of the muscle cell protein content at the time of slaughter and the influence of protein post mortem modifications, on the quality of raw meat. We will provide illustrations based on recent studies performed in our research group, using proteomics.
M. MORZEL, C. TERLOUW, E LAVILLE