Abstract
To clarify the mechanism of pressure-induced meat tenderization or acceleration of meat conditioning, the pressure-induced morphological and biochemical changes in sarcoplasmic reticulum (SR), and Ca2+ release from SR in the rabbit skeletal muscle treated with high pressure (100-300 MPa, 5min) were investigated in comparison with those of the SR from conditioned muscle. The destruction of the membrane structure of the SR expanded with increasing pressure applied to the muscle. Significant changes in the SDS-PAGE profile were not observed in the SR from the pressurized muscle up to 200MPa, but a marked decrease of the ATPase protein and high-affinity Ca2+-binding protein were observed in the SR from the pressurized muscle at 300MPa. The ATPase activities increased in the SR isolated from the muscle exposed to high pressure up to 200MPa. When the muscle was pressurized at 300MPa, the ATPase activity dropped to the same level with that of the SR from the untreated muscle. Ca2+ uptake ability of the SR vesicles measured using a fluorescent chelating reagent decreased with increasing pressure applied to the muscle. Ultrastructural studies showed that Ca2+, which was mainly localized in the SR region of the untreated fiber bundles, was translocated into myofibrillar space in the pressurized muscle. It is clear that a brief exposure of the muscle to high pressure causes considerable changes in membrane structure and biochemical function of SR as compared with those of SR in the muscle induced by conditioning. The pressure-induced Ca2+ release and loss of the structural regularity of myofibrils may be one of the causes for meat tenderization and acceleration of meat conditioning induced by high-pressure treatment.
