Electrical stunning of cattle.

Cattle are normally stunned electrically by three sequential cycles, first a three-second head-only cycle, to stun the animal, secondly a 15-second cardiac cycle, to induce ventricular fibrillation (cardiac arrest), and thirdly a four-second discharge cycle, to reduce convulsions after death. An effective and immediate stun was produced when > or =1.15 amps sinusoidal AC at 50 Hz was applied between the nose and neck electrodes for less than one second. However, when applied for three seconds, head-only currents of >0.46 amp sinusoidal AC at 50 Hz were sufficient to induce epileptiform activity in the brain, identified as high amplitude low frequency activity in the electroencephalogram. The induction of effective head-only electrical stunning resulted in an average interval of 50 seconds before the return of rhythmic breathing movements, and positive corneal and palpebral reflexes. The cardiac arrest cycle successfully induced ventricular fibrillation when >1.51 amps sinusoidal AC at 50 Hz was applied for five seconds between the nose and brisket electrodes.

Effectiveness of electrical stunning applied using a variety of waveform-frequency combinations and consequences for carcase quality in broiler chickens.

1. The effectiveness of electrical stunning of poultry was assessed where the recommended current of 105 mA per bird was applied using a range of waveform-frequency combinations. In addition the effect of the treatments on subsequent carcase quality was investigated. 2. The use of frequencies greater than 50 Hz was associated with a failure to induce ventricular fibrillation. 3. All waveform-frequency combinations were equally effective in producing a stunned state; the time to recovery was not affected by stunning treatment but was significantly longer in heavier birds. 4. The use of high frequency (500 Hz and 1500 Hz) stunning currents resulted in a decrease in carcase downgrading and a marked reduction in the occurrence of breast muscle haemorrhages, which represent significant commercial benefits to be gained by their use.

Modelling post-mortem tenderisation-I: Texture of electrically stimulated and non-stimulated beef.

Texture in electrically stimulated and non-stimulated beef M Pectoralis profundus, stored under a range of temperatures from 0 to 30°C, while avoiding muscle shortening, was measured from 1 to 21 days after stunning. The pre-rigor temperature (from 0 to 30°C), maintained until the pH had fallen to 6·4 and then held at 15°C, had no effect on the toughness nor on the rate of tenderisation after rigor. Modelling toughness prior to 24 h suggested that toughness of all muscles could be rationalised and that first-order tenderisation began when the muscles reached pH 6·1 when the toughness of all the muscles was projected to be 12·5 kg. After pH 6·1, the rate of tenderisation at 30°C was 10-fold higher than at 1°C and was not affected by variations in pH from 6·1 to 5·5. At the higher temperatures, the ultimate toughness of aged meat was slightly higher than at the lower temperatures.