Morphological, nutritional and safety traits of bluefin tuna (Thunnus thynnus) reared in floating cages

Abstract

To evaluate the influence of fattening on morphological, nutritional and safety characteristics, two lots of bluefin tuna were sampled before (November: 2 C, 4 ?) and after 5 months of fattening (April: 5 C, 5 ?). The specimens, after death, were refrigerated and analysed at different times over the period of a week for morphological and flesh physico-chemical parameters in six muscle sites. Tuna sampled in April had greater body weight (44.04 vs 36.41kg), trunk length (52.21 vs 48.22cm) and minimum and maximum circumferences (13.74 vs 12.77 and 94.90 vs 89.10cm). No differences in other linear measures or body components were found. Fattening did not influence flesh colour or total lipid content, producing small differences in its chemical composition: greater C18:0, C18:1n9 and PUFAn6 percentages; higher putrescine and histamine (0.489 vs 0.335 and 0.666 vs 0.370mg/kg) but lower spermine and spermidine (10.598 vs 17.387 and 2.420 vs 3.928mg/kg) levels. Large differences in physico-chemical parameters were found between muscle sites and a significant interaction between sampling date and muscle site indicated non homogeneous changes in chemical composition of dorsal, ventral and red muscle after fattening. Sex only influenced fat content in viscera (C 12.84 vs ? 9.84%).

Keywords

• Flesh colour, Fattening, Fatty acids, Thunnus thynnus.