Development of a rapid method for codfish identification in processed fish products based on SYBR Green real-time PCR

Using species outside the order Gadiformes to prepare codfish products has been widely revealed as a new type of fraud in China, highlighting the necessity to establish proper methods for codfish species identification. This work aimed to develop a new SYBR Green real-time PCR assay for the detection of codfish ingredient (mainly the eight Gadiformes species, Gadus morhua, Gadus macrocephalus, Theragra chalcogramma, Pollachius virens, Melanogrammus aeglefinus, Merluccius merluccius, Merluccius australis and Albatrossia pectoralis) in processed fish products based on mitochondrial 12S rRNA gene. Results highlighted the positive Cq (cycle quantification value, average value 19.18 +/- 1.49) only from the eight Gadiformes species, with no fluorescent signal (Cq > 32) for the other sixty-seven non-Gadiformes species. The absolute limit of detection was 0.048 ng genomic DNA. Methodology validation succeeded in twenty-six commercial products. These results demonstrated that the newly developed method is suitable for the identification of codfish ingredient in processed fish products.