"Fresh live fish, killed and cooked on the spot." This is an alluring sign often displayed by restaurants. Many people believe that killing live fish and eating them immediately better ensures taste and nutrition. In reality, however, consuming fish right after it's been killed isn't scientific and could even result in ingesting toxins.
After a fresh live fish has just been killed, it enters a phase of rigor mortis. During this time, energy metabolism within the fish continues, and a series of biochemical changes occur. In this stage, small amounts of lactic acid and phosphoric acid are produced in the fish meat, which inhibit the proliferation and growth of putrefactive microorganisms. At this point, the fish meat is slightly acidic, the texture is tough, and the proteins in the fish tissue have not yet broken down to produce amino acids. Amino acids...