FIBER FRACTURE OF BOVINE MUSCULUS-PECTORALIS-PROFUNDUS MUSCLE COOKED PRERIGOR AND POSTRIGOR

The ultimate tensile strength and extensibility in the direction of the muscle fibres of cooked meat decreased exponentially during storage of the raw meat for up to 3 days at 15C. The mode of fracture was examined by light microscopy of longitudinal sections taken after testing to break. In meat cooked soon after stunning, 'brittle' fracture had been induced across the fibres and the high extensibility was proposed to be due to sequential fibre fracture. At 1 day postmortem, the fractures crossed several fibres occurring in a repetitive fashion every 30 mu m along the fibres. This was thought to be due to a stiff fibre embedded in an extensible surface matrix connecting the fibres. In aged meat, discontinuous fractures were prominent within each fibre and which stopped at the surface of each fibre showing further weakening of the fibre and the composite matrix. All the myofibrils remained in register. These changes are consistent with a gradual reduction in cohesion within the meat and indicates that the weakening of the focal adhesions is primarily responsible for postmortem tenderisation.