The changes in the rigor mortis of fish body and the breaking strength of the muscle were com-pared using tilapia. During ice storage, the rigor index measured by the modified Cutting's method reached maximum 9h after death and the full rigor lasted for 4 days, while the breaking strength of the muscle became maximum 3h after death, then decreased continuously for 24h and then did not change. This result strongly suggested that both changes should be clearly distingu-ished. Therefore, we proposed that the change of the apparent rigor of fish body is expressed as “pre-, in and post-rigor” and that the change of the texture of fish muscle is expressed as “tough and weak”. The weakening of muscle may be explained not as a proteolytic breakdown of myofibrils but as a decomposition of the muscle structure, because no proteolytic reaction was detected by the examination of TCA-soluble material and by the analysis on SDS-PAGE.
