Effects of electrical stimulation on tenderness of chicken processed by the chill-pack method

Ninety chickens were assigned at random to 1 of 8 treatment groups or to a control group in each replication. The 8 treatment groups received electrical stimulation (ES) of 50 or 100 volts for a duration of 25 pulses (25p) or until no response (NS) was detected at a point in the slaughter sequence of either pre-stick (PS) or pre-chill (PC); the control group received no electrical stimulation other than stunning. The treatment groups were arranged in a 2 x 2 x 2 factorial design. Two hundred seventy-nine birds were analyzed in three replications to study the possibility of improving the tenderness, or at least preventing the toughening, of "chill-pack" processed chickens. Measurements made included Warner-Bratzler shear force, an objective measure of tenderness; sarcomere length; and expressible moisture index (EMI), an indication of water holding capacity (WHC) which is positively correlated with tenderness. Warner-Bratzler shear values were significantly different between replications (P<.01) and between the PS and PC treatments as groups (P<.05), although neither group was different from the control (P>.10). The interaction between replication and treatment was significant (P<.05). There was no difference in sarcomere lengths among any of the individual treatments or due to any of the factors studied. EMI was significantly different between replications (P<.01) and between PS and PC stimulation groups (P<.01), but neither group differed significantly from the control (P>.10). Results indicate that electrical stimulation applied prior to chilling may be a feasible way to reduce toughening in chill-pack chicken.