Digital archive of theses discussed at the University of Pisa


Thesis etd-03162016-123144

Thesis type
Tesi di dottorato di ricerca
Thesis title
DNA-based methods for the control of seafood frauds in Italy and China
Academic discipline
Course of study
tutor Prof.ssa Guidi, Alessandra
  • FINS
  • BLAST analysis
  • DNA barcoding
  • PCR based methods
  • DNA
  • China
  • fraud
  • Seafood traceability
Graduation session start date
The globalization of the seafood supply chain, together with the difficulty in visual identification of prepared seafood products, makes quite easy to commit frauds by substituting high-value species with less expensive ones. The traceability systems implemented at international level should be the answer to solve this issue and the accurate labeling of seafood species throughout the supply chain has become quite important for the protection of the consumers. Currently, the European Union (EU) has established a legal framework for the management of seafood label (Reg. No. 1379/2013), while in China, despite its increasingly important role in the world's seafood market, a specific vertical regulation for fishery product traceability and an official system for the assignment of the trade names are still not available.
Meanwhile, it is also necessary to develop rapid, economic and highly sensitive methods for the identification of seafood species. DNA-based methods are the most applied for species identification due to the high resistance of nucleic acid to physical-chemical treatments that allow to recover diagnostic fragment of DNA even in processed products. However, the most appropriate DNA based method to be used should be selected according to the species and the kind of products to be analyzed.
In this perspective, the research activities were aimed: (I) to develop a simple and cost-effective bead-milling method for DNA extraction from fish muscles, (II) to develop a DNA-based method to verify the labeling accuracy in the light of the European provisions, (III-IV) to investigate the phenomenon of species substitution in China, (V) to assess the possible implementations of the Chinese labeling system through the introduction of official denominations, in light of EU.
The bead-based method developed in the first work allowed to obtain acceptable amounts of DNA, with good purity and amplificability. Although the salting-out method has been confirmed as the most effective protocol in terms of pure performances, the bead-milling procedure can be considered a valid alternative.
In the second work the analyisis of canned pet food commercialized on the EU market and claiming to contain high price ingredients was performed using Basic Local Alignment Search Tool (BLAST) and and Forensically Informative Nucleotide Sequencing (FINS). An impressive rate of mislabeling (100% for whole minnows and 40% for tuna fillets) was highlighted.
DNA and mini-DNA barcoding technique was applied for the identification of commercial products sold with the Chinese term 鳕(Xue, Cod) in supermarkets (Nanjing and Shanghai) and in the online market in China. The mislabeling rate was assessed according to three increasingly stringent definitions due to the lack of harmonization around the definition of Cod in China. A very high mislabeling rate, which exceeded 60% even with the less stringent definition, was highlighted. The same technique applied for the identification of fish products sold on the Chinese e-commerce market as Anoplopoma fimbria highlighted an alarming overall misrepresentation rate of 85,7%.
Finally, through the analysis of the commercial designations officially adopted by 5 European Member States (MSs) (Italy, France, United Kingdom (UK), Germany and Spain) and of those adopted on international lists of Chinese names such as the FAO Fisheries and Aquaculture Statistics and Information Service (ASFIS), FishBase and the Latin-Chinese Dictionary of Fish Names (LCDFN) for Cod, Salmon and Tuna species, possible implementations of the Chinese labeling system through the introduction of official denominations were suggested.