Effects of feed deprivation and electrical, gas, and captive needle stunning on early postmortem muscle metabolism and subsequent meat quality

The general method for stunning poultry before slaughter is by immersion of a chicken's head into an electrified waterbath. This method results in carcass and meat quality deficiencies. The major problems are hemorrhages and a delay in onset of rigor mortis, which increases the risk of cold shortening with early deboning. In two experiments, this study examines the early postmortem metabolism in the breast muscle and its effect on ultimate meat quality. The first experiment describes the effects of 5 h feed deprivation on the availability of glycogen from the liver and the breast muscle, of waterbath and head-only electrical stunning on pH and metabolite levels up to 6 h in unprocessed muscle, and the consequences on meat quality. The second experiment compares the same measurements after waterbath and head-only electrical stunning, CO2/O2/N2 and Ar/CO2 gases, and captive needle stunning. Metabolic degradation halted after 6 h without processing or after 4 h under conventional conditions after waterbath and CO2/O2/N2 stunning. With other stunning methods, this occurrence is at a faster rate, largely depending on muscle activity. Muscle glycogen does not need to be exhausted for energy generation to cease. If glycogen is a limiting factor, as found with head-only stunning, pH drops too rapidly and affects water-holding capacity and color. Hemorrhage scores were higher with electrical stunning than with other stunning methods. Gas stunning affected color and, to a lesser extent, water-holding capacity. Captive needle stunning scored between gas and electrical stunning on most measurements.