ELISA-based detection of mislabeled albacore (Thunnus alalunga) fresh and frozen fish fillets

Abstract

An indirect enzyme-linked immunosorbent assay (ELISA) has been developed for the identification of albacore (Thunnus alalunga) and its differentiation from other lessvalued scombrid species such as yellowfin tuna (Thunnus albacares), bullet tuna (Auxis rochei), atlantic bonito (Sarda sarda), bigeye tuna (Thunnus obesus), little tunny (Euthynnus alleteratus) and skipjack tuna (Katsuwonus pelamis). The assay uses polyclonal antibodies raised in rabbits against soluble muscle protein extract from fresh albacore. These polyclonal antibodies were rendered species-specific by blocking them with the heterologous soluble muscle proteins, allowing discrimination between fresh albacore and the rest of the scombrid species, except for yellowfin tuna. A total of 40 commercial albacore fresh and frozen fillets were analysed, revealing an incorrect labelling in 32.5% of the albacore samples. However, positive samples (67.5%) could be albacore or yellowfin tuna and should require a DNA assay as discriminatory technique.