The subject of my PhD course regards two aspects of fish products quality and characterization. The first one deals with the evaluation of the effects of natural antioxidants (ellagic acid and L-ascorbic acid) in enhancing fresh sole (Solea solea) shelf life. Quality assurance in the fish sector involves monitoring and documenting defined quality criteria as required by regulations (European Community, 1996), product specifications and consumer demands. Fresh fish products are commonly sold at storage temperature. However, many undesirable changes can occur in the products during storage, due to microbial growth and fish spoilage, affording evident economic loss. From this point of view it is important to develop systems which help to prolong fish shelf life. In this perspective, we have studied the effects of ellagic acid (EA) and L-ascorbic acid (LAA)/ sodium ascorbate (SA), either alone or in combination, on the microbiological quality of fresh finfish Solea solea during storage at 0 Â°C. The results showed that addition of EA (0.03%) alone or in combination with L-AA (1.71%)/SA (1.98%) significantly delayed the proliferation of aerobic plate counts, psychrotrophic counts and Pseudomonas bacteria extending the product shelf life up to 10 days, versus 8 days for control. During the storage, the pH increase is slowed down when the fish samples are subjected to the treatment with preservative agents. The effect of lowering the pH increase is particularly pronounced when a combination of EA and L-AA/SA is used. Therefore, EA alone or in combination with L-AA and SA can be successfully utilized to reduce the microbial growth, extending the shelf life of fish during storage at 0 Â°C. The second aspect of fish products quality and characterization studied in this PhD course deals with the identification of ''species-specific genetic markers'' of red mullet (M. barbatus) as useful tools for ''the commercial designation of species''. Consumers demand for a deeper knowledge of the quality and the origin of food is increasing significantly. The UE with the adoption of Reg. (EC) 2065/2001, laying down detailed rules for the application of Reg. (EC) 104/2000, wanted to give a strong push to the " traceability of fish products" through the labelling systems. European Council Regulation (EC) 104/2000, on the common organization of the markets in fishery and aquaculture products, specifies that these products may not be offered for retail use unless they are labelled with ''the commercial name of the species'', ''the production method'' and ''the capture zone''. Particularly, in Italy "the commercial designation" must respect the list present in the enclosure A of the D.M. 27-03-02 and in the following modifications and integrations of the D.M. 25/07/2005. Therefore, the development of analytical methods for species identification is necessary to detect and avoid wilful, as well as unintentional substitution of different fish and shellfish species and to enforce labelling regulations (Mackie et al., 1999). The main aim of this study was the development of a PCR-based assay for the identification of red mullet (M. barbatus) and striped red mullet (M. surmuletus), and was projected on the locus 16S rDNA gene fragment of the 3 Mullid genera (Mullus, Upeneus and Pseudopeneus), widespread in the Mediterranean Sea. The second aim was the investigation of the possible polymorphisms able to detect different populations of red mullet (M. barbatus) in the Mediterranean Sea. The PCR-assay developed can be adequately used for ''species identification'' of red mullet (M. barbatus) and striped red mullet (M. surmuletus). This approach is rapid and offers the potential to detect fraudulent or unintentional mislabeling of seafood, but can be particularly indicated for application to ''processed products''. The randomness of genetic differences among samples indicated that the Adriatic red mullet stock probably belongs to single population unit, according to Garoia et. al., 2004.