Total volatile basic nitrogen and trimethylamine nitrogen levels during ice storage of European hake (Merluccius merluccius): A seasonal and size differentiation

Whole ungutted European hake (Merluccius merluccius) caught by trawling off the Central Tyrrhenian coast of Italy in winter and in summer were stored in ice. The dynamics of changes of total volatile basic nitrogen (TVB-N) and trimethylamine-nitrogen (TMA-N) levels during ice storage of small- (20 ± 3 cm length) and large-sized (37 ± 6 cm length) hake caught in either season were studied. The TVB-N and TMA-N levels of hake caught in winter remained low (below 20 mg and 3 mg/100 g, respectively) throughout the experiment regardless of the body size. In summer TVB-N and TMA-N levels increased sharply (P < 0.05) during ice storage and at a higher rate in small than in large fish, a fact ascribable to fish exposure to high temperatures first in the water, during trawling, and then in the fishing vessel before ice-boxing. On the basis of the results obtained in this work, it may be concluded that ungutted European hake show a clear seasonal and size differentiation of the evolution of TVB-N and TMA-N during ice storage.