Modifications of Ultrastructure and Myofibrillar Proteins of Post-rigor Beef Treated by High Pressure

This study was conducted in order to determine the effects of high pressure treatment on several parameters that contribute to beef tenderness. Isolated myofibrils and post-rigor steaks of Biceps femoris muscles (2 d post-mortem) were pressurized from 100 to 600 MPa for 260 s at 10 °C. Electron micrographs showed modifications on both cross and longitudinal sections depending on the intensity of pressure applied. After treatment at 130 MPa, the ultrastructure of longitudinal and cross sections was similar to the control. The changes occurred from 325 MPa pressure. Ultrastructural changes included a heterogeneous aspect on the intermyofibrillar space attributed to the aggregation or coagulation of proteins, and the disappearance of the M-line in the H-zone and loss of integrity of I-band filament. The intensification of costameres and intermediate filament bundles could also be observed. A significant increase in the area of myofibrils and in myofibrillar solubility was observed in pressurized samples. Moreover, electrophoretic analysis revealed increased solubilization of two myosin light chains (LC1 and LC2) after treatment at 300, 400 and 600 MPa.