The objective of this study was to identify by electrophoresis the changes in the fractions of muscle proteins during the post mortem period of different genetic groups and analyse the tenderness of meat samples refrigerated for 24 hours (not aged) and aged for 7 days. Were used forty-eight samples of Longissimus muscle from bovines of 4 genetic groups: 12 Nelore; 12 crossed ½ Aberdeen-Angus ½ Nelore x Brahman; 12 Brangus; 12 crossed ½ Aberdeen-Angus ½ Nelore x Pardo submitted to superprecoce biological model. From each sample two slices was retired, one of them was not aged and the other was aged for 7 days at 2ºC. In the analysis of shear force, both the non-aged samples, as those subjected to seven days of maturation did not differ on meat tenderness, but all of them showed acceptable tenderness, which can be explained by the low age at slaughter, which was provided by the fattening system that these animals were submitted. In the eletrophoretic analysis of bands of protein was noted degradation of myosin heavy chain and Troponin-T and the appearance of the 30 kDa fragment for all genetic groups after the 7 days period of aging. All the genetic groups showed good meat tenderness, regardless the ageing time.
superprecoce cattle; SDS-Page electrophoresis; shear force; genetic group; myofibrillar proteolysis