Distribution of nitrogenous constituents in the muscle extracts of eight species of fish

In order to determine the distribution of nitrogenous constituents in the fish muscle extracts as completely as possible, free and combined amino acids, trimethylamine oxide (TMAO), trimethylamine, creatine, creatinine, and nucleotides were analyzed in 8 species of fish, red sea bream, stone flounder, flathead flounder, flounder, puffer, angler, common mackerel, and jack mackerel. In all species tested, the sum of the nitrogen in these constituents amounted to nearly 90% or more of the total extractive nitrogen. The distribution pattern of nitrogen among these constituents, however, varied considerably from species to species, except for nucleotides which were fairly constant. Free amino acid-N was 7-45% of the total extractive nitrogen, creatine-N 29-58%, and TMAO-N 2-23%. These results are discussed in reference to those reported previously by other authors.