Gel Electrophoretic Analysis of the Protein Changes in Ground Beef Stored at 2°C

Purified myofibrils and sarcoplasmic proteins were prepared from ground (GR) and intact (CON) beef semitendinosus muscle samples after 0, 1, 3, 6, and 10 days of storage at 2°C. SDS‐polyacrylamide gel electrophoresis analysis revealed the following major postmortem changes in GR samples: the gradual disappearance of nebulin and desmin, appearance of 110,000‐, 95,000‐ and 30,000‐dalton polypeptides, and an increased content of myosin light chain‐3 and 55,000‐dalton component in myofibrils. Also noted was emergence of 100,000‐ and −500,000‐dalton polypeptides and diminution of 300,000‐dalton protein in the sarcoplasmic fraction. Since GR samples showed proteolytic changes similar to those of CON samples, it was concluded that grinding had little effect on postmortem muscle protein degradation.