Muscle activity at slaughter: I. Changes in flesh colour and gaping in rainbow trout

High activity at slaughter is known to cause changes to the muscle biochemistry in terms of Ž . muscle pH and adenosine triphosphate ATP content. This experiment looked at how the muscle activity may affect the flesh quality of fish. Electro-stimulation of a carcass immediately after death can be used as a model for high levels of muscle activity prior to death. This experiment Ž . showed that electro-stimulation of 1.5 kg rainbow trout Oncorhynchus mykiss immediately after slaughter not only resulted in short times to rigor, but that the flesh colour was affected. The flesh Ž . Ž . Ž . became significantly lighter P-0.001 , less red P-0.001 and had higher chroma P-0.001 w as measured by the CIE CIE, 1976. 18th Session, London, U.K., Sept. 1975. CIE Publication 36, x U U U Ž . Paris, France. L a b system, and the Roche colour card score was lowered P-0.01 compared to flesh from fish that had shown very low levels of activity before slaughter and were not electro-stimulated after death. The fillets were also more susceptible to gaping following the Ž . post-mortem stimulation P-0.001 . This indicated that electro-stimulation after death reduces the quality of the flesh. q 2000 Elsevier Science B.V. All rights reserved.