The aim of the study was the evaluation of the effect of ageing on the extent of myofibrillar proteins degradation and tenderness of beef in different crossbreeds, BB × HF and SM × HF, from which the musculus semitendinosus was obtained. The pH value, basic composition of meat, and colour parameters were determined on the 3rd d post mortem. The Warner Bratzler shear force and the extent of protein degradation were evaluated in regard to the effect of ageing time. Meat of BB × HF crossbreed had a lower amount of intramuscular fat and higher protein content (P ≤ 0.05). The shear force decreased with ageing time in the case of both crossbreeds. However, the highest values were noted in SM × HF crossbreed on days 3 and 7 of ageing. The differences in proteolysis of myofibrillar proteins and polypeptides, determined by SDS-PAGE electrophoresis, were observed between crossbreeds and the ageing time. A significant decrease in desmin and increased levels of 49-46 kDa and 32-27 kDa polypeptides (products of proteolytic degradation) were observed with an increasing ageing time. In addition, the rate of increase in the amount of 32-27 kDa polypeptides was more significant in BB × HF crossbreed. The data obtained showed that tenderness and the extent of protein degradation are associated with ageing process and animals’ genotype.
