Factors affecting tenderness of electrically stimulated poultry

Abstract

Effective electrical stimulation parameters for breast muscle of poultry deboned at the end of the processing line were determined. For experimental studies, 14.3 half sine‐wave pulses per s, 80 V peak, 10 ms duration were applied 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 stimulation caused a fall in pH of 0.26 pH units. The rate of pH fall was accelerated, so that at 20°C, ultimate pH after stimulation was reached in 120 min versus 300 min for no stimulation and at 40°C, ultimate pH after stimulation was reached in 220 min versus 80 min for no stimulation. Unrestrained muscle entering rigor mortis at 40°C shortened by 25.4% and when entering rigor mortis at 20°C shortened by 7.6% with the mean shear force being 13.42 and 8.13 kg F, respectively. The effectiveness of electrical stimulation was determined by comparing the shortening and tenderness 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°C for 72 h. For cut muscles, electrical stimulation reduced muscle shortening (P < 0.05). The greatest difference in tenderness occurred between stimulated intact breasts (mean 3.34 kg F) versus cut non‐stimulated breasts (mean 13.5 kg F) (P < 0.001), but there was still a significant difference in shear force between cut non‐stimulated versus cut stimulated breasts (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 electrodes to head/neck area and legs applied for 120 s, in the post stunning and bleeding area was examined. When the breast was cut from non‐stimulated muscles at 65 min post slaughter (6.5–7°C), the meat was tough with mean shear force of 8.7 kg F (maximum 15.5 kg F), and for stimulated cut muscles, the mean shear force value was significantly lower at 3.2 kg (P < 0.001). There was no significant difference between any of the stimulated muscles cut at 65–80 min and non‐stimulated intact muscles. With low rigor temperatures at 7°C, electrical stimulation has no disadvantages and allows early deboning without toughening.