Species Identification by Means of Mitochondrial Cytochrome &amp;lt;i&amp;gt;b&amp;lt;/i&amp;gt; DNA Sequencing in Processed Anchovy, Sardine and Tuna Products

Giorgio Galiero,Anna Cutarelli,Federico Capuano,Federica Corrado

doi:10.4236/fns.2018.94029

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.

Highlights

It is important to identify the fish species used in commercial products, in order to unmask possible frauds, which may be perpetrated by replacing valuable species with others of lower value or protected species, especially in elaborately processed foodstuffs [1]
Forensic genetic techniques for species identification provide an essential tool for the authentication of seafood in the marketplace, and should be more widely applied in order to maintain the credibility of certification by discouraging commercial fraud [4]
The species declared on the label was confirmed in all samples except two, which was labeled as Thunnus alalunga instead of Thunnus thynnus, as proved by our assays

Summary

Introduction

It is important to identify the fish species used in commercial products, in order to unmask possible frauds, which may be perpetrated by replacing valuable species with others of lower value or protected species, especially in elaborately processed foodstuffs (fish in oil and canned products) [1]. Precautionary measures are necessary, especially since substituted or mislabeled fish may contain unknown toxic or allergenic substances that are potentially dangerous [2]. For this reason, the demand for analytical tests by the authorities responsible for food monitoring is increasing worldwide [3]. Forensic genetic techniques for species identification provide an essential tool for the authentication of seafood in the marketplace, and should be more widely applied in order to maintain the credibility of certification by discouraging commercial fraud [4]. DNA barcoding is used for the rapid and accurate identification of animal or plant species not listed on the labels of processed foods [5]

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