[Biochemical, physicochemical and functional characterization of turbot (Scophthalmus maximus). Study of the changes occurring during the 4 degrees C storage].

The turbot (Scophthalmus maximus) is a kind of flatfish that is well adapted to intensive farm culture. After the harvest it is necessary to know the physicochemical, biochemical and technological properties and if during the refrigerated storage, changes of these properties are developed. The main objective of the study was the assessment of the proximal composition, the biochemical, physicochemical and functional properties, and how they are influenced during the 16 days storage at 4 degrees C. Parameters such as centesimal composition, PAGE-SDS, and protein thermal stability through a DSC were carried out. pH, total volatile base-nitrogen (TVB-N) dripping, texture, holding water capacity (WHC), emulsification (EC) and gelification (GC) were also determined. Results for the proximal composition were: humidity 76.3%; fat content 2.71%; proteins 19.6%; and ashes 1.3%. Two different thermal transitions at 47.5 degrees C (myosin) and 76.9 degrees C (actin) were observed. The PAGE-SDS showed profiles corresponding to myofibrilars and sarcoplasmatic proteins, which presented no changes during the storage. pH experimented an increase from 5.9 to 6.6; TVB-N showed a variation from 20.0 to 39.5 mg TVB-N/100 g of muscle at the day 16. The WHC started with a 10.5% and ended in 58.1%; no GC was observed. The increase of the EC and WHC during the storage was due to conformational changes of proteins. The compression force presented a fluctuation between 111.2 and 106.0 N and the shear strain decreased during the storage from 148.6 to 95.2 N. The dripping showed a variation between 1.7% and 2.5%. According to the results of the storage during 16 days at 4 degrees C, the NBV-T content determined a shelf life of 14 days.