The objective of the research study was to determine the changes in the content of proteins in centrifugal drip obtained from meat of young bulls of four breeds: Polish Holstein-Friesian (PHF) of Black and White variety, Polish Red (PC), Limousine (L), and Hereford (H), all of them slaughtered at the age of 6, 9, and 12 months during a 10-day period of chilled beef aging. A SDS-PAGE technique was applied to perform an electrophoretic analysis of proteins derived from centrifugal drip of muscle tissue 45 min, 48, 96, and 240 h after slaughter. The occurrence of titin, desmin and troponin T in the centrifugal drip was confirmed by a western blotting method using monoclonal antibodies to specifically identify definite proteins. The aging time was found to be the most important factor that impacted the proteolysis of proteins in meat. The greatest changes in the content of high-molecular proteins (2400 ÷ 3700 kDa and >160 kDa) were reported on the 10^th day of meat ageing. In the case of proteins with a lower molecular weight (160 kDa and 90 ÷ 95 kDa), such changes occurred already during the first two days post mortem. All the variability factors analyzed (i.e. breed and age of cattle, and aging time of beef meat) significantly affected (p 0.05) only the content of proteins with a molecular weight of 90 ÷ 95 kDa. The most advanced process of proteolysis of high molecular weight proteins was reported in the centrifugal drip from meat of bulls of PHF breed.