Effects of electrical stimulation and pre-rigor conditioning temperature on ageing potential of hot-boned beef muscle

The objective of this study was to determine the impact of 3 hrs pre-rigor holding temperatures and low voltage electrical stimulation (ES), on the activities of small heat shock proteins (sHSP) and µ-calpain and tenderness of bull beef. Paired loins (M. longissimus lumborum) from 13 bulls were hot-boned within 40 min of slaughter, immediately electrically stimulated and subjected to various holding temperatures (5°C, 15°C, 25°C and 35°C) for 3 hrs and the rate of muscle pH decline, sarcomere length, shear force, and proteolysis of muscle proteins were measured. ES-35°C and ES-25°C samples had lower shear force value at 14 days of ageing when compared to other samples. The combination of ES and pre-rigor holding temperature (25°C) resulted in longer sarcomere length compared to non-ES. µ-Calpain activity – as indicated by autolysis – was highest in ES-35°C samples. Desmin, troponin-T and sHSP degradation were highest for ES-35°C samples. The results of this study show that the combination of ES with 3 hrs pre-rigor holding temperature at 35°C improved the tenderness of bull beef.