Effects of 2-Hz and 60-Hz electrical stimulation on the microstructure of beef

A comparative electron-microscope study was made of the structural changes brought about in bovine longissimus dorsi muscle by 2-Hz and 60-Hz electrical stimulation. Apart from the frequency difference, the two treatments were identical: 500V AC, 600 pulses (2Hz × 300s and 60 Hz × 10 s), and a time of application of about 40 min post mortem. The low-frequency current produced no detectable tissue disruption or irregularity in sarcomere length, whereas the 60-Hz treatment caused widespread supercontraction and the formation of contraction nodes; many sarcomeres in the internodal zones were stretched or fractured. The observations confirm and extend those of our earlier light-microscope study, and support the view that fiber disruption contributes significantly to the tenderizing effect of high-voltage electrical stimulation.