CHANGES IN FREE AMINO ACIDS AND BIOGENIC AMINES DURING RIPENING OF FRESH AND FROZEN SARDINE

A study was carried out on the evolution of free amino acids and biogenic amines throughout the ripening process of fresh and frozen sardine. The effect of the level of fish gutting was also followed. During ripening a general increase of free amino acids content was observed in all samples. Histidine was the exception to this trend and decreased throughout the processing period. On the basis of the ratio of basic/acidic amino acids, as an indicative of the ripened state, the fresh nobbed sardine ripened faster than the gutted fish. During the course of ripening a considerable increase in biogenic amines and particularly histamine occurred until the 20th day in products from fresh fish. The maximum histamine content allowed in ripened fish products in the European Union (400 mg/Kg) was never attained in this period. A general decrease in most amines was observed by the 240th day of ripening. Tyramine behaves differently and increased in the same period. The samples prepared with frozen fish consistently showed the lowest amine values throughout the ripening period. It seems that freezing has a good effect on the final quality of ripened products as it could decrease the bacterial activity responsible for biogenic amine formation.