Verification of authenticity: A rapid identification method for commercial scallop species through multiplex real-time PCR

Abstract

Seafood products are particularly vulnerable to food fraud and mislabelling, which may have negative implications on fisheries resources, economy, consumer health and trust. This is a considered problem for scallops, since these high-valued seafood products are usually sold without their morphologically characteristic shells. Scallop products differ in taste and value and usually species of the genus Pecten spp. are especially expensive in many European countries. The aim of the present study was the development of a multiplex TaqMan real-time PCR assay that allows a rapid and reliable authentication of the three commercially important species/genera Pecten spp. (usually King scallop P. maximus), Atlantic sea scallop Placopecten magellanicus, and Japanese scallop Mizuhopecten yessoensis. The design of primers and probes was based on mitochondrial 16S rRNA gene amplifying fragments of 138–198 bp. Following the optimization of the multiplex real-time PCR assay, analyses on efficiency, limit of detection, specificity, robustness, and crosstalk were conducted for validation purpose. Average Cq values of 20 ng DNA obtained for Pecten spp. were 17.64 ± 0.89, for P. magellanicus 18.42 ± 0.83, and for M. yessoensis 17.08 ± 0.79. Non-target species produced either no fluorescence signal or the Cq differed significantly from those of target species (p < 0.01). Finally, the newly developed real-time PCR assay was tested on commercial samples from German supermarkets and fishmongers accompanied by simultaneous verification through Sanger sequencing, which revealed a high mislabelling rate of 48%, especially for products purchased at fishmongers. The results emphasize the need of a control method that allows the rapid analysis of sufficient sample quantities. The study is one of the first which presents a multiplex TaqMan real-time PCR approach for the authentication of commercially important seafood species.