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article imageRestaurants look to DNA barcoding to identify seafood

By Albert Baer     Nov 29, 2011 in Science
In an effort to combat mislabeled seafood, restaurants are looking at a new genetic technique called barcoding to ensure the identity of their food.
Recent studies have shown that mislabeled seafood is disturbingly common, with industry watchdogs finding widespread misidentification of fish at stores and restaurants. A Consumer Reports study found that nearly one-fifth of samples they tested were incorrectly labeled, usually with common and cheaper species swapped out for more expensive kinds. In an effort to combat these mistakes and fraud, the Food and Drug Administration has recently approved the process of DNA barcoding to identify seafood samples.
DNA barcoding makes use of mitochondrial DNA (mtDNA), a type of DNA found in the mitochondria of cells. Mitochondria are structures which provide energy to cells, and contain distinct DNA which is separate from the main genomic DNA in the cell. This mtDNA has a high rate of mutation, which means that it is unique in nearly every species, unlike other regions of DNA which can be shared between species. By selecting a specific short region of mtDNA and determining its sequence, testers can find a “fingerprint” that is unique to a particular species, and is also quick and relatively easy to sequence.
Sequencing DNA involves taking a small sample from the specimen, isolating the DNA from the other cellular material, and using a special reaction to multiply the copies of DNA present. Those DNA segments are then run through a sequencing machine which identifies the nucleotides present at each location in the DNA strand, and presents this string of nucleotides to the tester. The new availability of this technology to the food industry is mainly due to the streamlining of sequencing techniques, and the increased availability of sequencing technologies. According to the Consortium for the Barcode of Life, barcode sequencing can now be done in small commercial labs in just a few hours for around $5 per sample.
Once a sequence is obtained from a test sample, it is then compared with a database of known species. The current universal database contains over 167,000 species. For its own regulatory purposes, the FDA maintains an independent database of over 250 samples of common seafood species.
For restaurant purposes, testing will likely be done on lots of seafood as they are brought off of trawlers and shipped to the restaurant. It will not be possible to test every individual piece of seafood, but independent testers will take representative samples from each lot they order, and test those to ensure the identity of the whole lot. The FDA currently plans to increase its own testing of seafood samples for regulatory reasons, but the markets and restaurateurs are also looking at contracting with independent labs to perform their own testing, responding to consumer concerns about the identity of the food they purchase.
More about Food, Fda, Seafood, Dna testing
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