Effects of early post-mortem pH and temperature on beef tenderness.

The tenderness of loin steaks, prepared from beef sides after chilling, is strongly influenced by muscle temperature in the first 3 h after slaughter. Maintenance of about 37°C within the Longissimus muscle during this time, whether by heavy fat cover or by ambient-temperature manipulation, results in appreciable tenderness enhancement. Early post-mortem muscle pH (which varies over a wide range) also affects tenderness significantly; provided early and exceptionally fast chilling does not induce cold shortening, slow glycolysis promotes tenderness. Low-frequency (2 Hz) electrical stimulation, which accelerates glycolysis but causes negligible tissue disruption, significantly toughens the loin; in its normal mode (50-60 Hz), therefore, stimulation produces its desirable tenderising effect mainly-and perhaps solely-by fibre fracture.