INFLUENCE OF PRE- AND POST-RIGOR MUSCLE CHANGES ON INTRINSIC TOUGHNESS OF BEEF MUSCLE

Abstract

Longissimus dorsi muscle from 108 beef carcasses of uniform pre-slaughter history were used to examine textural variations and causes of initial toughness. Muscle identified as tough at 24 h post-mortem had significantly toughened from the pre-rigor condition whereas muscle which was tender at 24 h had become significantly more tender than in the pre-rigor condition. A strong relationship was also identified between initial toughness and subsequent response to cooler aging at 2 C. Pre-rigor release of muscle tension by severing the muscle did not affect 24-h shear values of muscle classed as tender, but resulted in a 14% increased toughness in muscle classed as tough. Tender muscle was characterized by lower early postmortem pH values. Plasma creatine phosphokinase (CPK) levels were related in a non-linear fashion to muscle color and tenderness. Interrelationships between pre-rigor phenomena such as animal stress, glycolytic rate, cold-shortening and textural variations were discussed and related to commercial merchandising of beef carcasses.