Species Identification by Means of Mitochondrial Cytochrome <i>b</i> DNA Sequencing in Processed Anchovy, Sardine and Tuna Products

Abstract

Identifying the contents of processed food products is essential to correct labelling. In processed foodstuffs, species identification through morphological analysis is difficult. Several factors hinder the identification of fish species in processed foods: proteins or other materials subjected to analysis may be denatured during heat treatments; the presence of other ingredients (e.g., olive and other vegetable oils) may interfere with the analysis. Consequently, possible frauds perpetrated by replacing valuable species with less precious ones may go undetected. In most processed samples (e.g. canned products), DNA is degraded into small fragments, which considerably reduces the sensitivity of molecular analysis. The main goal of our research was to develop an analytical method able to identify fish species in highly processed products, such as canned fish. The assay was developed by combining an effective method of DNA recovery from samples with the detection of small-sized sequences of the mitochondrial Cytb gene. This method appears particularly suitable when morphological characterization is difficult, to carry out such as in canned products where DNA is degraded or present in small quantities. We have analyzed 60 samples of seafood commercial products identifying 3 different genera and five different species. All analyzed samples revealed a correct species declaration, for one sample we highlighted important commercial fraud. We also used bio-informatic identification systems for the Sequence Alignment and the construction of phylogenetic tree to better confirm the revealed fraud.