Although the improvement in tenderness resulting from post mortem refrigerated storage of carcasses is of considerable commercial importance, the mechanism(s) by which this process occurs is unknown, although it has been suggested that intramuscular protein catabolizing proteolytic enzymes may play a key role (Etherington, 1984). In order to develop a clearer understanding of the biochemical mechanisms underlying meat tenderization, the objective of this work was therefore to compare the proteolytic capacity of muscle from species known to differ markedly in rate of meat tenderization (approximate time shown in parenthesis): chicken (2days), lamb (4 days), pig (5 days) and rabbit (8 days).

Two methods were used to quantify muscle proteolytic capacity: (i) at point of slaughter, a comprehensive range of cytoplasmic and lysosomal protease types were determined using specific fluorimetric procedures; (ii) in vitro, using tissue homogenate based time course assays to measure (via analytical electrophoresis) the rate of structural protein degradation by endogenous or lysosomal proteases.