DNA Results Are In: Canned Sardines Are Kosher

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sardinesGlenn Collins reports in the New York Times:

Just so you know: Canned sardines are kosher.

This judgment would appear to be definitive, based on DNA evidence. Genetic testing by a parasitologist at the American Museum of Natural History has confirmed that the recent discovery of small worms in canned sardines does not render them treyf, or unkosher. It may render them unappetizing, but that judgment is up to the consumer (more on that later).

The museum got involved last March when rabbis from the Orthodox Union, which certifies as kosher hundreds of thousands of products across the world, sought scientific help in resolving a question that arose when they began finding the worms, or nematodes, in cans of sardines.

Talmudic debates can turn on fine distinctions, but this was relatively straightforward. The presence of worms could have been a sign that, during the preparation of the canned sardines, muscle from the fish had been improperly handled and allowed to mix with intestinal contents of the sardines, rendering them unkosher.

The issue was important because it “could have led to sardines losing certification as kosher,” said Dr. Mark Siddall, a curator and professor in the invertebrate department of the museum, who conducted the testing. Many consumers, including non-Jews, look for the certification label as a sign of quality assurance in food preparation.

The rabbis brought their samples of sardina pilchardus – the Mediterranean sardine – to the museum, where Dr. Siddell conducted so-called “DNA bar-coding” to analyze the species of the worms. Their DNA was isolated and two variants of the cytochrome oxidase gene – which is different for every animal species, as unique as a fingerprint, Dr. Siddell said – revealed that the type of worms in the samples reside only in the flesh of sardines. “This meant that there was no evidence that the intestines and the flesh had been commingled,” Dr. Siddell said.

The Orthodox Union also discovered evidence of worms in cans of orange capelin roe, and Dr. Siddall’s testing confirmed that the worms, as well, were not intestine-dwellers. The analysis of Dr. Siddall and his colleagues has been published in The Journal of Parasitology, and the union has formally ruled that both the sardines, and the capelin roe, are kosher. (The entire paper can be read below.)

In 2004, a similar Talmudic tempest involved a tiny crustacean known as a copepod, which was discovered swimming in New York City’s tap water, spurring debate among the observant about whether it rendered city water unkosher. Many contended that the crustacean was a distant relative of shrimp and lobster, shellfish that cannot be consumed because they lack fins and scales. The Orthodox Union recommended that city water be filtered before using it for drinking and cooking. That prompted restaurants to install filters, some costing more than $1,000, to remove the interlopers.

As for worms in sardines or in any fish, Article 81 of the New York City Department of Health Code has long required that “aquatic animals, fish or molluscan shellfish” be cooked, rendering such parasites harmless – unless customers assume some risk by asking for raw fish, as in sushi. The best sushi masters constantly examine the fish for evidence of parasites.

“The notion that there are worms in fish flesh is not new,” Dr. Siddall said. “As long as they’re cooked, or frozen first, they’re perfectly safe.”

Yes, but if the sardines are both safe and kosher, are the worms themselves – which are barely visible and look like thin whitish threads – disgusting?

“It is up to the individual’s aesthetic as to whether that is ‘yucky,’ ” Dr. Siddall said. “I’ve eaten worse. Curdled goose blood. Rhino beetle larvae. Both yummy. But that’s another story.”

{The New York Times/Matzav.com Newscenter}


  1. Thanks to the rabbis and to the professors. However I will not eat. I think I remember that it is forbidden to eat a food that, while otherwise permissible, is disgusting. I think it is further clarified that, should a particular individual find some among such food appetizing, we don’t rely upon that, but rather we go by the majority in the city.

  2. To the Litvak: and To all the FEINSHMECKERS that grew up in homes, who thank G-D their parents were born before them: Sardines in our home and homes of our friends, was a staple as was jam: and to my father who who was at work already already, while you were still turning over in bed, that was his lunch and breakfast. It was used for Shalosh Seudos, and in some parts where dips and other fancy items like guacamole and sun dried kreplech, that you all get from your places like Schwartzes and Pomeganite< sardines are still used, and it was kosher then in the 40’s 50’s and the 60’s

  3. Can someone please explain this gem to me?

    ” muscle from the fish had been improperly handled and allowed to mix with intestinal contents of the sardines, rendering them unkosher.”

    What is the problem with mingling muscle and innards. The question the Rabbonim were dealing with was the origin of the parasites

  4. #8 the innards contain the undigested food eaten by the fish before death, which is small crustaceans and thus is unkosher (and gross).

  5. Had read a while back in Kosher Korner (if I remember correctly) that the cleanest and best sardines, and to be sure of its kashrut in regard to worms is to buy the ones from Morocco. ‘Season’, I think, uses sardines from there and Grandiasa too.


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