Modification of early-postmortem muscle pH and use of postmortem aging to improve beef tenderness

This study was conducted to determine whether modification of early-postmortem muscle pH and(or) control of postmortem aging time could be used to improve tenderness of strip loin (longissimus, LM), top sirloin (GM), and top round (SM) steaks. Muscle pH, at 1.5 and 3 h postmortem, was modified using three 60-Hz electrical stimulation (ES) treatments (240 V, 35 V, or combined use of 240 and 35 V). Vacuum-packaged sections of the LM, GM, and SM were aged for 6, 12, 18, or 24 d postmortem. Use of ES increased rate of postmortem muscle pH decline and decreased shear force of LM steaks but had no effect on tenderness of GM or SM steaks. Reducing 3-h pH of the LM reduced variability in LM shear force but had little effect on tenderness of GM or SM steaks. However, lower values for 24-h pH of the LM were associated with increased tenderness of all three cuts. Tenderness of all cuts also improved as length of the postmortem aging period was increased. For LM and SM steaks, the greatest improvements in tenderness were achieved by 12 d; however, tenderness of GM steaks continued to increase up to 24 d postmortem.