Myosin light chain 1 release from myofibrillar fraction during postmortem aging is a potential indicator of proteolysis and tenderness of beef.

The objective of this study was to identify proteins in bovine longissimus dorsi muscle that are related to tenderness. Two dimensional difference in gel electrophoresis (2D-DIGE) was used to compare the sarcoplasmic fractions from steaks that differed in star probe values at 14 days postmortem. The intensity of myosin light chain 1 (MLC1) was greater in the sarcoplasmic fraction prepared from steaks that had lower star probe values. It was hypothesized that μ-calpain catalyzes the release MLC1 into the sarcoplasmic fraction. Myofibrils from beef longissimus dorsi were purified and incubated with μ-calpain and the appropriate buffer controls. μ-Calpain was added at 1.23 μg (0.0875 U) of pure μ-calpain/mg myofibrillar protein. Incubations of one and 120 min had a greater abundance of MLC1 in the supernatants than the control incubations. As a consequence of μ-calpain proteolysis, MLC1 is rapidly released from the myofibril and is a potential indicator of proteolysis and improvement in beef tenderness.