Quality loss related to rancidity development during frozen storage of horse mackerel (Trachurus trachurus)

The development of rancidity and its effect on quality loss were studied in frozen horse mackerel (Trachurus trachurus). Two different kinds of fish products (whole fish and fillets) were stored at a commercial freezer temperature (-20degreesC) for up to 12 mon and were compared to samples stored at a much lower temperature (-80degreesC). Analyses included: lipid hydrolysis (FFA formation) and oxidation (PV, thiobarbituric acid index, fluorescent compound formation), loss of endogenous antioxidant (alpha-tocopherol), protein changes (electrophoretic analysis of sarcoplasmic and SDS-soluble fractions), and sensory analysis (skin, eyes, gills, flesh odor, consistency, flesh appearance). According to biochemical indices, fillets stored at -20degreesC showed susceptibility to rancidity development, leading to a shelf life of 1 mon, whereas whole fish at the same temperature were still edible at month 5. The use of a low temperature (-80degreesC) inhibited rancidity development, leading to good-quality (whole fish) and fair-quality (fillets) fish products at the end of the experiment. The application of protective treatments especially designed to prevent lipid oxidation is encouraged when commercializing this species in the frozen state.