Identification and Authentication of Commercial Mi-iuy Croaker (Miichthys miiuy) Products by Two PCR-Based Methods

Mi-iuy croaker (Miichthys miiuy) is one of the most important ingredients of Korean cuisine and, thus, has a high economic value. However, the similar morphological traits among croaker fish belonging to family Sciaenidae are often exploited for seafood fraud. In this study, an M. miiuy-specific primer set was designed and further improved by the development of a rapid and cost-effective duplex PCR method. The specificity of M. miiuy-specific duplex PCR was tested using 22 seafood species, and no cross-reactivity was observed. The sensitivity of the PCR assay was found to be 0.1 ng/μL. For the first time, labeling compliance of 43 commercial mi-iuy croaker products was verified using both full DNA barcoding and M. miiuy-specific duplex PCR methods. For species identification, BOLDSYSTEMS and GenBank database were screened with the consensus sequences of each PCR product as a query. This identification result was further confirmed using the M. miiuy-specific duplex PCR method. The findings of this study revealed that principal species substituted were law croaker (Pseudotolithus senegallus, n = 4), bigeye croaker (Micropogonias megalops, n = 3), whitemouth croaker (Micropogonias furnieri, n = 1), and tigertoothed croaker (Otolithes ruber, n = 1). A significant percentage (21%) of mislabeling was present in commercial mi-iuy products sold on the South Korean market.