EFFECTS OF EXOGENOUS PROTEASE EFFECTORS ON BEEF TENDERNESS DEVELOPMENT AND MYOFIBRILLAR DEGRADATION AND SOLUBILITY

The effects of in situ postrigor injection (24 h postmortem) of exogen ous aspartic, serine, and cysteine proteinase effecters into cylindric al beef longissimus samples on tenderness and myofibrillar protein deg radation and integrity were studied. Injection of phenylmethanesulphon ylfluoride (PMSF) and pepstatin did not influence shear force or prote in degradation measured 8 d postmortem, confirming that neither serine nor aspartic proteinases affect tenderization. Injection of leupeptin , an epoxysuccinyl peptide (E-64), or N-acetyl-Leu-Leu-norleucinal (ca lpain inhibitor I) blocked tenderization completely, as observed by hi gher (P < .05) shear force values. A causal relationship between incre ased toughness and prevented action of the cysteine proteinases was su ggested by a concomitant reduction of myofibrillar