Lab test finds no tuna in Subway’s tuna sandwich—experts say it’s because it was already cooked

In January of 2021, a lawsuit was filed against the fast food chain Subway by Karen Dhanowa and Nilima Amin of Alameda County, California (NY Times).

The lawsuit alleged that the fish was made from “a mixture of various concoctions.” As a result, The New York Times tested sixty inches of Subway tuna sandwiches from three different Los Angeles locations. The tuna was frozen and sent to a lab, which determined that there is “”no amplifiable tuna DNA … present in the sample and so we obtained no amplification products from the DNA. Therefore, we cannot identify the species” (KTVU).

The US Food and Drug Administration’s Seafood List labels only fifteen species of fish that can be labeled tuna, so the lab conducted a PCR test to see if Subway’s tuna featured one of the varying tuna species. The lab determined two potential reasons for why no tuna was detected. “One is it’s so heavily processed that whatever we could pull out, we couldn’t make an identification … Or we got some and there’s just nothing there that’s tuna.”

However, experts told the New York TImes that when tuna is cooked, its protein breaks down making it hard to identify, which could mean that the lab results are not accurate. In a statement to Business Insider, Subway stated, “A recent New York Times report indicates that DNA testing is an unreliable methodology for identifying processed tuna. This report supports and reflects the position that Subway has taken in relation to a meritless lawsuit filed in California and with respect to DNA testing as a means to identify cooked proteins. DNA testing is simply not a reliable way to identify denatured proteins, like Subway’s tuna, which was cooked before it was tested” (USA Today).



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