Non-protein nitrogenous compounds in muscle extract of oceanic cephalopods

Abstract

Chemical compositions, especially non-protein nitrogenous constituents of extractives from 14 kinds of squid and octopus caught in far seas, were analyzed to research the possibility of utilization as human food. The constituent of the extractive nitrogenous compounds was markedly different depending on the species. The ammonia content in muscle varied widely depending on the kind of squid. The highest value, 756mg-N/100g, was found in muchi-ika Mastigoteuthis sp., followed by yurei-ika Chiroteuthis imperator and yatsude-ika Octopoteuthis sp., which can be called true ammoniaic squid. In addition to ammonia, large amounts of TMA-N and DMA-N were deter-mined in several kinds of squid such as hotaru-ika-modoki Enoploteuthis chunu, suji-ika Eucleo-teuthis luminosa, and muchi-ika. In very large squid, giant squid Architeuthis japonica and nyudo-ika Moroteuthis robusta, extremely high moisture of around 90% was found and a very high level of ammonia was also detected. It is confirmed that the ammonia in squid muscle exists as ammonium chloride, because the concentration of chloride ion was almost equivalent to that of ammonium ion in all spec-imens analyzed. Composition and concentration of free amino acids varied also depending on the species. Generally, the concentration of free amino acids in oceanic squid was lower than that in normal squid. Considering the chemical characteristics of ammoniaic squid, it may be difficult to use them as human food.