Does high voltage electrical stimulation of sheep affect rate of tenderisation?

Abstract

Romney-cross sheep (n = 24) were shot with a captive bolt, slaughtered, and dressed and suspended by the Achilles tendons. Half of each group of carcasses did not have any electrical input. The remaining carcasses were electrically stimulated at 30 min post mortem for 90 s using 1130 V peak (current 2 A) pulses (half sine wave, 10 ms duration) at an alternating pulse frequency of 14.28 pulses s-1. All carcasses were placed into a room at 10°C with an air velocity of 1-1.5 m s-1. At rigor mortis (ultimate pH) the m. longissimus thoracis et lumborum was removed and cut into four portions to age for 0, 9, 30, and 57 hours at 10°C then frozen at -20°C, cooked from the frozen state, and 1 cm × 1 cm samples sheared using a MIRINZ tenderometer. The sarcomere length of small fibre bundles was measured by laser diffraction and showed no difference between the treatment groups but became longer from rump to head. By chilling and ensuring both electrically stimulated and non-stimulated muscle enters rigor mortis at temperatures from 10 to 17°C, and indexing the start of ageing to rigor mortis, the rate of tenderisation was the same. Stimulation therefore exerts its main effects through early rigor mortis and ageing at higher temperatures.