DNA testing uncovers suspect sushi
Story
Highlights
* Two teenage girls decided to test 60 samples of seafood
* They used a genetic fingerprinting technique to see if the
fish were labeled correctly
* Samples were collected from four restaurants and 10 grocery
stores
* The results showed 25 percent of the girls' samples were mislabeled
* Next
Article in Technology
From
Christina Chinnici / CNN
NEW
YORK (CNN) -- Two teenage girls used DNA bar coding
to determine that some sushi on New York dinner plates was mislabeled
with cheaper fish being passed off as a more expensive species.Results
show that half of the restaurants and six of 10 grocery stores
sold items that were mislabeled.Kate Stoeckle and Louisa Strauss
were not science majors or even college students when they decided
to take 60 samples of seafood and use a genetic fingerprinting
technique to see whether the fish were labeled correctly.
The
graduates of Manhattan's Trinity School in New York were inspired
by Kate Stoeckle's father, Mark, a scientist and proponent of
the use of DNA bar coding, a technique that greatly simplifies
the process of identifying a species.
"Growing
up, bar coding was dinner conversation, so I was familiar with
it," Stoeckle said. "And then one night, while out
to dinner, I asked, could we barcode sushi? Louisa and I love
sushi, and we thought, why not apply the bar coding technology
to see what food we're eating?"
After
collecting samples from four restaurants and 10 grocery stores,
spending about $300, the teens sent them to the University of
Guelph in Ontario, Canada, where the Barcode of Life project
began and where a graduate student had agreed to conduct the
genetic analysis.
The
girls' samples were compared with the global library of 30,562
bar codes representing nearly 5,500 fish
species.
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According
to Mark Stoeckle, DNA is extracted chemically. The bar code
gene, a chemical code, is amplified in a process called Polymerase
Chain Reaction.
A
machine examines the DNA sequences called bases, which are a
series of letters, A, G, C and T, and then digitally matches
them with a library of DNA bar codes or other series of letters.
The bar code itself is very long, with 648 letters.
The
results showed that 25 percent of the girls' samples were mislabeled:
half of the restaurant samples and six out of 10 grocery store
samples.
In
every case, less desirable or cheaper fish was substituted for
its more expensive counterpart, Stoeckle said. She and her father
would not divulge the names of vendors, citing a fear of lawsuits.
"It's
not the fishermen, and it might not even be the restaurants,"
she said. "Most likely, the mislabeling is occurring somewhere
at the distribution level."
For example, fish sold as white tuna turned out to be cheaper
Mozambique tilapia, flying roe fish was replaced with smelt,
and red snapper was mislabeled as Atlantic cod and Acadian redfish,
an endangered species.
"They
are the first to do it," Mark Stoeckle said of the girls.
"It's like 'CSI' for fish."
He said the process could become as common as GPS.
"Many people are working on miniaturizing it, bring the
cost down and the speed to process up," he said.
"Sequencing
is a chemical process. There is no reason why we can't check
the food on our plate [and] send the signal out to a database
electronically. GPS used to be as big as refrigerators and only
used by the government. Now it's a common application in a phone."
The
students worked under Jesse H. Asusubel of Rockefeller University,
a champion of DNA bar coding.
They
say the project wasn't work. "It didn't feel like a chore.
It wasn't time-consuming at all," Stoeckle said. "I'm
hoping to get more public interest so it can become cheaper
and more common."
Asked
whether she's less inclined to eat sushi, she said, "I've
eaten it, like, 50 times since, so I don't think so."