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DNA Barcoding Proves Sardines Kosher

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DNA Barcoding Proves Sardines Kosher
A petri dish with capelin eggs and nematodes in various larval stages. © AMNH/M. Siddall

Scientists at the Museum recently helped a group of rabbis answer a culturally significant dietary question: can canned fish products containing parasitic worms still be considered kosher?

The study began last spring, when rabbinical experts from the Orthodox Union, the largest organization that certifies food products for the Jewish community, brought a variety of kosher-certified sardines and capelin eggs to the Museum. The presence of worms could have been a sign that, during the preparation of the canned food, muscle from the fish had been improperly handled and allowed to mix with intestinal contents, potentially violating Jewish dietary laws.

The key to determining whether the canned food was improperly handled is in the worms’ life cycles, said Curator Mark Siddall, who conducted the study. “Some species of worms live in the muscles of fish when they’re in the larval stage,” he said. “Other species live in the fish’s intestines when they’re adults. We already know the life cycles for these parasites, so all we have to do is figure out what species were present in the canned food.”

To do this, the researchers used a technique called “DNA barcoding,” technology based on a relatively short region of a gene in the mitochondrion, an energy-producing structure located outside of the cell’s nucleus, that allows researchers to efficiently identify the species from which a piece of meat—or even a leather handbag—came from.

The scientists identified a handful of different nematode species, none of which are known to live in the guts of fish during their life cycles. This means there’s no evidence of intestinal worms co-mingling with the fish meat or eggs.

The results, which were recently published online in the Journal of Parasitology, prompted the Orthodox Union to declare that the food remains kosher.

For more information about this study, see the Museum press release.