LPT 321: Meat Science (1+1)

ELECTRICAL STIMULATION

• Electrical stimulation refers to the passing of high voltage electricity through the carcass immediately after slaughter, the current causing the muscles to contract and thereby use up glycogen, ATP and creatine phosphate.
• A number of muscle contractions are made to occur in a short time, thereby accelerating the onset of rigor.
• The process of rigor mortis is advanced and the pH is brought down to less than 6.0 within 2-3 hours of slaughter.
• Hence rigor passes off and thus cold shortening does not occur even when the temperature of the carcass is brought down to less than 10 ⁰C within 10 hours of slaughter.
• High voltages have been found to be more effective especially if electrical stimulation is delayed. But electrical stimulation must be carried out within half an hour of slaughter for best results.
• Electrical stimulationis also said to improve muscle colour and brightness.

Mechanism of action of electrical stimulation

• Two theories have been proposed as putative mechanisms for the effectiveness of electrical stimulation to hasten the onset of rigor and thus prevent cold shortening.
• The first theory suggests that electrical stimulation results in the conversion of the inactive form of the enzyme phosphorylase (phosphorylase a) to the active from of the enzyme phosphorylase (phosphorylase b), which stimulates the breakdown of glycogen (glycolysis), which results in the drop in pH.
• It was further suggested that the enzyme involved in the conversion of phosphorylase, phosphorylase kinase is stimulated by an increase in myofibrillar ATP ase activity, which takes place as a consequence of electrical stimulation.
• Subsequent studies clearly determined that the increase in the active from of the enzyme phosphorylase (phosphorylase b) was transient and lasted for just 35 minutes.
• The other theory suggested that the increase in Ca⁺⁺ caused a stimulation of glycolysis), which results in the drop in pH.