The effects of stunning amperage and deboning time on early rigor development and breast meat quality of broilers

Two trials were conducted to determine the effects of stunning amperage on the early rigor development and quality of broiler breast meat. In each trial, 108 broilers were killed either without stunning or following constant amperage stunning at 50 or 125 mA. The breast muscles (Pectoralis major) were removed from the carcasses at 0.2, 1, 2, 4, 6, 8, 10, 12, or 24 h post-mortem. Breast muscle pH and R-value (inosine to adenosine nucleotide ratio) were determined immediately upon deboning on one side of each carcass. After aging the deboned breast fillets for 48 h, cook loss and Allo-Kramer shear values were determined on the opposite side. Stunning at 50 or 125 mA resulted in significantly higher muscle pH values up to 6 h post-mortem, after which there were no further significant differences. Stunning at 50 and 125 mA resulted in significantly lower R-values up to 6 h post-mortem. Stunning had no effect on cook loss. Stunning at 125 mA resulted in significantly tougher meat up to 10 h post-mortem than meat from unstunned birds or birds stunned at 50 mA. These results indicate that the delayed onset of rigor, as measured by muscle pH and R-value, noted in electrically stunned birds lasts for approximately 4 to 6 h, after which differences due to stunning disappear.