Characterisation of non-protein nitrogen in the Cephalopods volador (Illex coindetii), pota (Todaropsis eblanae) and octopus (Eledone cirrhosa)

A characterisation of non-protein nitrogen (NPN) was carried out in the muscle of three species of cephalopods: volador (Illex coindetii), pota (Todaropsis eblanae) and octopus (Eledone cirrhosa). These species were classified according to sex, sexual development (immature, mature) and anatomical zone (mantle, arms). There were no major differences in the NPN contents of the three species studied. The anatomical zone clearly marks the difference in NPN content, with the content being greater in the mantle than in the arms for all the species. The trimethylamine oxide–nitrogen levels in volador were greater in the mantle than in the arms and these differences were not observed in the other two species. In pota and octopus, however, it is the stage of sexual development that exhibited differences, with a greater quantity of trimethylamine oxide–nitrogen in the immature specimens than the mature ones. The trimethlyl and total volatile basic nitrogen behaviour had no clear trend, the TVB-N levels were probably so low that these differences were not important. The same thing occurred with the pH, where the lowest values were recorded in octopus and the highest in pota. The free amino acid (FAA) compositions varied to a great extent, depending on the species and, to a less extent, depending on the sex, stage of sexual development and anatomical zone. The total FAA content was virtually the same in volador and pota, while it was about 75% lower in octopus. The highest concentrations of FAA in the three species were for proline, arginine and alanine, but in different proportions.