Gas composition in controlled atmosphere stunning affects turkey meat quality traits

1. Investigations were made into the breast and leg muscle energy metabolism, and the quality of breast meat of turkeys after controlled atmosphere stunning or stun-killing (CAS) with various gas mixtures. In addition, the effect on meat quality of an increase in the chilling rate of turkey breast meat after hypercapnic or anoxic stun-killing was studied. 2. A total of 35 turkey toms within two replicate pens were individually stunned during consecutive weeks using one of 4 CAS methods. The stunning gases tested were high CO2 concentration (60% CO2 in air), high N-2 concentration (98% N-2, <2% O-2), a mixture of 76% N-2 and 24% CO2, and a biphasic method (first minute in mixture containing 40% CO2, 30% N-2, and 30% O-2; followed by two minutes in a mixture containing 60% CO2 in air). 3. The birds stunned with N-2 displayed the highest initial reduction in muscle pH, but after 4 h post mortem there were no differences in pH values associated with the various CAS methods. 4. The CAS method alone had no statistically significant effect on the quality of turkey breast muscle when the chilling speed was rapid (0 degrees C for 4 h, followed by storage at 4 degrees C). When the chilling rate was slowed (20 degrees C for 4 h followed by storage at 4 degrees C), a significant decrease in cooking loss and in Warner-Bratzler shear force was recorded for birds stun-killed with CO2. 5. This study shows that anoxic stun-killing with N-2 had no adverse effects on meat quality despite the rapid post mortem pH decrease. The CAS with N-2 allows rapid cooling of carcases without the risk of cold shortening, whereas with CO2-stun-killing of turkeys, the rate of chilling should be slower. Concerning meat quality, all the CAS methods tested were suitable for stunning turkeys.