Identification of Selected Tuna Species in Commercial Products.

Eliska Servusova,Zora Piskata

doi:10.3390/molecules26041137

Abstract

This study was conducted to develop systems for the identification of four tuna species (skipjack tuna Katsuwonus pelamis, yellowfin tuna Thunnus albacares, bullet tuna Auxis sp. and Atlantic bonito Sarda sp). At first, raw samples of these species and a mix intended as internal control were prepared for the authentication of fish muscle tissue of the genus Thunnus sp., Auxis sp. and Sarda sp. DNA from raw muscle tissue, the mix and samples was extracted with the DNeasy mericon Food Kit (Qiagen GmbH, Hilden, Germany). The concentration and purity of DNA in raw samples were evaluated using a spectrophotometer. Primers and probe sequences were specifically designed to identify the selected species. In addition, primers and a probe for the endogenous 12S rRNA gene were designed to determine the presence of amplifiable fish (especially tuna) DNA in samples. Furthermore, the species specificity of the designed primers and probes was verified in DNA samples of various tuna and bonito species. Limit of detection for the selected species was calculated as well as the coefficient of determination R2 and efficiency of real-time PCR testing was determined. To evaluate the developed real-time PCR methods, 70 commercial tuna products were analysed. The results show that mislabelling of fish products can still be encountered and, moreover, the presence of an additional species can be identified.

Highlights

The aim of this study was to develop a method for the identification of four tuna species: yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwonus pelamis), Atlantic bonito (Sarda sp.) and bullet tuna (Auxis sp.) in technologically modified products based on the amplification of species-specific mitochondrial DNA sequences using real-time PCR
The real-time PCR systems developed in this study allow us to identify four tuna species and simultaneously to avoid false-negative results
The identification of these species was based on the development of real-time PCR, the design of in-house made primers and probes for the given species, and the design of a primer and a probe for internal amplification control to confirm fish muscle tissue in samples

Summary

Introduction

Academic Editors: Clinio Locatelli, Dora Melucci and Marcello Locatelli. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Tuna are among the most popular fish species available on the food market, primarily sold as canned products. The principal species used for canning purposes are skipjack (Katsuwonus pelamis) and yellowfin tuna (Thunnus albacares). The market offers raw and frozen fillets, especially made from yellowfin tuna. Different quality and price of various tuna species may lead to a tendency to intentionally or unintentionally substitute different species. Council Regulation (EEC) No 1536/92 laying down common marketing standards for preserved tuna and bonito, specifies the conditions for tuna marketing. The tuna and bonito species are listed in the Annex to the Regulation.

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Results

Conclusion