Application of a PCR-RFLP Method to Identify Salmon Species in US Commercial Products

A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for salmon species identification was optimized for use with U. S. commercial products. Reference specimens of six salmonid species were collected and morphologically verified. A 463- to 464-bp fragment of the mitochondrial tRNA(Glu)/cytochrome b gene was PCR-amplified, digested with two restriction enzymes (Sau3AI and NlaIII), and analyzed with agarose gel electrophoresis. All six species were successfully differentiated with this method and the restriction digest was shortened to 1 h rather than overnight. A decision-making flowchart was developed based on these results that allows for species diagnosis within two-three steps. After the method was optimized, it was tested with a variety of commercial salmon products (n = 29), including canned, smoked, jerky, and fresh fillet samples. Salmon species identification was successful for all 14 smoked and fresh/frozen fillet products, with the possibility of same-day species diagnosis. Species identification was also achieved for two out of three jerky products, but required overnight lysis. The remainder of the samples could not be diagnosed-including canned salmon, pouch-sterilized salmon, and canned pate. Overall, this method showed high potential for use in same-day species authentication with lightly processed seafood, but heavily processed products will require alternate methods.