Factors affecting tenderness of electrically stimulated poultry

Effective electrical stimulation parameters for breast muscle of poultry de boned at the end of the processing line were determined. For experimental s tudies, 14.3 half sine-wave pulses per s, 80 V peak, 10 ms duration were ap plied for 60 s between head and cloaca of birds removed after stunning and bleeding and then returned to the processing line. Some birds were held at a constant temperature to determine rates of pH fall. Electrical stimulatio n caused a fall in pH of 0.26 pH units. The rate of pH fall was accelerated , so that at 20 degreesC, ultimate pH after stimulation was reached in 120 min versus 300 min for no stimulation and at 40 degreesC, ultimate pH after stimulation was reached in 220 min versus 80 min for no stimulation. Unres trained muscle entering rigor mortis at 40 degreesC shortened by 25.4% and when entering rigor mortis at 20 degreesC shortened by 7.6% with the mean s hear force being 13.42 and 8.13 kg F, respectively. The effectiveness of el ectrical stimulation was determined by comparing the shortening and tendern ess of breast muscles that were either left on the carcass or after cutting them from the breast bone and humerus 60 min post stimulation and aged at 0-3 degreesC for 72 h. For cut muscles, electrical stimulation reduced musc le shortening (P < 0.05). The greatest difference in tenderness occurred be tween stimulated intact breasts (mean 3.34 kg F) versus cut nonstimulated b reasts (mean 13.5 kg F) (P < 0.001), but there was still a significant diff erence in shear force between cut non-stimulated versus cut stimulated brea sts (P < 0.05). A commercial processing line using electrical stimulation ( 230 V, 14.3 half sine-wave pulses per s, 10 ms duration), via rubbing elect rodes to head/neck area and legs applied for 120s, in the post stunning and bleeding area was examined. When the breast was cut from non-stimulated mu scles at 65 min post slaughter (6.5-7 degreesC), the meat was tough with me an shear force of 8.7 kg F (maximum 15.5 kg F), and for stimulated cut musc les, the mean shear force value was significantly lower at 3.2 kg (P < 0.00 1). There was no significant difference between any of the stimulated muscl es cut at 65-80 min and nonstimulated intact muscles. With low rigor temper atures at 7 degreesC, electrical stimulation has no disadvantages and allow s early deboning without toughening.