AGING OF BEEF - INFLUENCE OF 2 AGING METHODS ON SENSORY PROPERTIES AND MYOFIBRILLAR PROTEINS

The influence of ageing on the hook (OH) and deboned vacuum packaged ( VP) ageing on sensory evaluation, shear force, myofibrillar fragmentat ion index (MFI) and myofibrillar protein concentrations was studied. F orty-eight hours post mortem the left hind quarters of Simmental heife r carcasses were divided into wholesale cuts and deboned. Samples were taken from the Mm. longissimus thoracis et lumborum (LTL), M. gluteus medius (GM) and M. psoas major (PM) for determination of MFI and for SDS-PAGE electrophoresis. The remaining muscle portions were VP aged a long with the intact right hind quarter at 0-degree-C for a further 12 days. Fourteen days post mortem samples of the LTL, GM and PM were ta ken for evaluation. In general, 14 days post mortem the OH aged sample s were more tender and flavoursome. Sarcomere lengths did not differ b etween treatments or ageing period. MFI-values did not differ between treatments. SDS-PAGE showed an increased level of proteolysis during V P ageing regarding the lower molecular weight myofibrillar proteins, s uch as troponin-I, and an increase in 30, 27 and 22 kD components. MFI -values increased during ageing, and indicated a higher degree of tend erisation in the LTL and GM. Sensory evaluation and shear force showed that a higher level of tenderisation was achieved with OH ageing. Hen ce, proteolysis of the lower molecular myofibrillar proteins does not have a direct response on tenderness.