Assessing freshness of European sea bass (Dicentrarchus labrax) from different farming systems

This study aimed to assess the evolution of freshness in 90 European sea bass (Dicentrarchus labrax) analyzed after 3, 6, 10, 13, and 17 days of storage in ice at 2°C. Sea bass were caught in three farms characterized by different rearing systems (extensive coastal lagoons, intensive inland basins, intensive sea cages). At each storage time, sensory analysis for freshness was performed on intact fish according to the Quality Index Method (QIM); skin colour and body firmness were measured on raw fish with a Minolta spectrophotometer and a dynamometer with a 20 mm diameter cylindrical probe, respectively; pH was recorded on the fillets. Data were submitted to analysis of variance using the GLM procedure with rearing system, storage time and their interaction as the variability factors. From the 3rd to the 17th day of storage, red and yellow indexes measured on skin decreased (P<0.01) as well as body firmness (from 28.9 to 23.4 N; P<0.01). Fillet pH remained stable (about 6.30) until the 13th day of storage and then increased up to 6.45 (P=0.10) at the 17th day. The total QIM score significantly increased with the days of storage and reached the maximum value (14.7 over a maximum of 22.0) after 17 days; skin appearance, body firmness, and gill traits showed some degradation soon after 3 days of storage. In contrast contrast, eye and abdomen traits showed some appreciable degradation only after 13 days of storage. All traits were affected by the rearing system (P<0.01). In particular, sea bass from the extensive system degraded to a slower extent compared with those from the intensive systems: total QIM scores (averages of all storage times) were 7.45 vs 8.83 and 9.33 (P<0.001) for sea bass caught in extensive coastal lagoons vs intensive inland basins and intensive sea cages. Moreover, in sea bass reared in sea cages, skin appearance, body firmness and eye traits degraded quicker and to a greater extent compared to fish from the other farming systems.