Titin content of beef in relation to tenderness

Steaks obtained from the longissimus dorsi muscle of 24 crossbred steers were subjected to four treatments (unaged raw, aged raw, unaged cooked, aged cooked) and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Titin migrated primarily as a single protein band in unaged raw samples (48 h post mortem), as a doublet in aged (16 days) raw samples, and as a triplet in unaged and aged cooked samples. Total titin band density remained constant among steaks that varied widely in Warner-Bratzler shear value, suggesting that beef steaks varying in tenderness contain the same amount of titin. It is concluded that titin content, as determined by gel electrophoresis, does not distinguish 'tough' from 'tender' beef.