FDA Steps Up DNA Testing for Fish Species Verification

Dec. 22, 2011 - PRLog -- The US Food and Drug Administration (FDA) has notified the US domestic seafood industry that agency and state regulators will be sampling and testing 100 high value species of fish over the next four months, to determine the accuracy of species labeling. The initiative grew out of concern that inexpensive species, or species with potential safety concerns, are being intentionally mislabeled for sale as a higher valued species or to avoid import restrictions. Mislabeled seafood is considered misbranded under the Food, Drug and Cosmetic Act, thus it violates the law.

According to the FDA the most commonly mislabeled seafood is shown in the following table.

Examples of commonly substituted seafood:

Premium fish -  Cheaper substitute

Red snapper - Rockfish
Mahi mahi - Yellowtail (Seriola lalandi)
Swordfish - Mako Shark
Orange roughy - Oreo dory or john dory
Cod - Alaska pollock
Halibut - Sea bass
Dover Sole - Arrowtooth flounder
Red drum - Black drum
Snapper (Lutjanus sp.) - Tilapia
Grouper - Basa or tra
Lake or yellow perch - White perch or zander
Caviar (sturgeon species) - Paddlefish or other fish roe
Walleye - Sauger or Alaska pollock
Chum salmon - Pink salmon
Salmon - Steelhead trout
Pacific salmon - Atlantic salmon
Blue crabmeat - Imported crabmeat
Wild-caught salmon - Farmed-raised salmon

The FDA lists fish under the Fish and Fishery Product Hazards and Controls Guidance which, when labeled as a different fish species, can create a food safety hazard.

The subtle differences in taste and texture between fish species make identifying the species particularly difficult once the fish has been filleted or processed. For this reason identification of fish species normally requires DNA testing. Fish identification is now performed by the FDA using a system that is based on research by the University of Guelph’s Barcode of Life (BOL) and the Smithsonian Natural History Museum’s library of authenticated samples. The Fish Barcode of Life campaign (Fish-BOL), is an international research collaboration to assemble a standardized reference DNA sequence library for all species of fish.

The FISH-BOL project (http://www.fishbol.org/) uses a DNA-based identification system, based on the mitochondrial gene, cytochrome c oxidase subunit 1. As demonstrated in several studies, this gene permits the diagnosis of species throughout the animal kingdom. Furthermore, their results show that sequence divergences at this specific gene routinely enable discrimination of even closely allied species in nearly all animal phyla.

As a part of the BOL project, DNA sequences have been identified for 172 authenticated fish, representing 72 species and 27 families. In animals overall, a fragment of only 655 base pairs of amino acids, starting near the 5’ end of the cytochrome c oxidase subunit 1 mitochondrial gene, has been shown in the majority of cases to be reliable enough for species identification.

In their identification project, the FDA utilizes Polymerase Chain Reaction (PCR) followed by DNA sequencing to generate the DNA barcodes for fish species identification. They have already established a reference standard sequence library for seafood identification by using this methodology.

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SGS offers services in the PCR testing field for species identification and a broad range of food-related services (www.foodsafety.sgs.com) through its global network of laboratories. In addition, SGS is committed to keeping interested parties informed of developments on regulatory activity and new methodology development.

Please contact SGS for further information.

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