Changes in Free Amino Acids in Skeletal Muscle of Cod (Gadus morhua) Under Conditions Simulating Gillnet Fishing

The total amounts of free amino acids, comprising both the intracellular and plasmal pools, as well as the amino acids combined in small peptides were determined with an automatic amino acid analyser in muscular tissues of freshly killed cod and in cod suffocated in simulated gillnetting conditions. The total amount of the free amino acids in the musculature was 2.4% of the amino acids composing the proteins. More than 90% of the free amino acid pool was represented by histidine, taurine, glycine, alanine, lysine, and β-alanine. The amino acids that were not found in small peptides are taurine, alanine, threonine, lysine, tyrosine, cystine, and methionine. In the absence of flexion or handling of the suffocated fish there was no evidence of enzymatic processes up to 72 hr after death. There was a slight, continuous loss of the free amino acids from the intact body of the fish during the prerigor and rigor periods. No evidence of deaminase activity affecting the amino acids was detected. Histidine, with its methyl homologues, was the major free amino acid.