Calpain and cathepsin activities, and protein extractability during ageing of longissimus porcine muscle from normal and PSE meat

Proteolytic activity on commercial substrates and protein extractability in solutions of different ionic strength were compared for normal and exudative longissimus porcine muscles during ageing at 4 °C. No effect of meat quality on calpain and cathepsin activities was observed, whereas ageing time had a statistically significant effect on calpain activity and cathepsin B + L activity. Protein extractability depended on meat quality and it was higher in normal meat than in exudative meat. Differences in accessibility of the myofibrils, according to meat quality, can determine the differences in the action of proteolytic enzymes and in protein extractability. It is suggested that myofibrillar protein extractability could be a suitable meat quality indicator.