Update, March 6: Subway has released the lab reports of both independent tests. Both Maxxam Analytics in Ontario, Canada and Elisa Technologies, Inc. in Florida used enzyme-linked immunosorbent assays (ELISA) designed for foods to quantify soy in the chicken. ELISAs are a standard type of assay that generally detect and quantify substances based on binding by an antibody. In the assay, antibody binding initiates a detectable chemical reaction, which usually results in a color change. In the case of Elisa Technologies, the lab used an antibody that binds to soy meal proteins and used known concentrations of those soy proteins for comparison to determine the amount of soy protein in Subway’s chicken samples.
In all samples, Elisa detected 3 parts per million or less of soy protein, which is much less than one percent of chicken. Maxxam discovered 5.3 ppm of soy protein in the chicken, which is still well below one percent.
Original story from March 3
Earlier this week, Ars reported that a study by the Canadian Broadcasting Corporation’s Marketplace found that Subway chicken should contain only 50 percent chicken and the rest mostly soy. But in the wake of the news, food scientists are scratching their heads over the CBC’s testing methods and interpretation.
“The CBC story wouldn’t stop me from getting a chicken sandwich at Subway if I wanted to,” Mary Ellen Camire told Ars. Camire, who says she generally likes meatballs more, is a professor of food science and human nutrition at the University of Maine and a past president of the Institute of Food Technologists, a nonprofit scientific association of food scientists.
Central to its skepticism is the CBC’s choice to use a DNA test from a lab that doesn’t specialize in nutritional science. (The CBC study used a wildlife research center at Trent University.) DNA testing is useful if, for example, you want to know if the fish you buy at the store is the kind of fish the store says it is, she explains. from. But food scientists usually don’t use DNA tests to look for proportions of the content.
Joseph Marcy, the chief of the division of nutritional science and technology at Virginia Polytechnic Institute and State University, agreed. “It seems like an unusual way to do that.”
For starters, plant and animal cells vary in size and the amount of DNA content they carry. So DNA content alone would not be a good indicator of a substance’s composition without some additional calculations and tests. It is conceivable that such cellular variation could be controlled, given standardized substances to compare against, and the results could be accurate after careful analysis. However, the CBC has not released the methods and calculations it used to analyze the raw DNA data.
Additionally, Camire says, Subway likely adds a highly concentrated, yeast-flavored soy protein to its processed chicken. This is a common binding and flavoring ingredient, and the manufacturer that makes Subway’s chicken supplies similar chicken to other restaurants. With such an artificial soy protein product, Camire wasn’t sure how much DNA would be in it.
Finally, if the chicken really was 50 percent soy protein, it would probably be very noticeable to those eating it. Soy protein would be much spongier, and the chicken wouldn’t have much protein fiber, Camire added. “I just don’t have a lot of confidence in the way the tests were done,” she said.
Meanwhile, Subway has gone on the defensive, calling the tests “stunningly flawed” and releasing the results of independent analysis indicating that the chicken at its restaurants contains only 1 percent soy or less, as the restaurant has always claimed. “Subway sent samples of the Canadian products Marketplace claimed to contain 50 percent soy protein to Maxxam Analytics of Canada and Elisa Technologies, Inc., of Florida,” a Subway spokesperson said in a statement. “Results from both labs found soy protein below 10 ppm, or less than 1%, in all samples tested. These findings are consistent with the low levels of soy protein we add to the spices and marinade to keep the products moist and keep it tasteful.”
Subway president and CEO Suzanne Greco was quoted as saying:
Marketplace’s staggeringly flawed test is a huge disservice to our customers. The safety, quality and integrity of our food are the foundation of our business. That’s why we took extra care when testing and retesting the chicken. Our customers can rely on our food. The claim that our chicken is only 50% chicken is 100% incorrect.
Subway did not respond to Ars’ request for more information about their testing methods and results.
The CBC stands by its results—largely. In a report late Wednesday, the outlet released more of its data, but not the methods or calculations it used for its interpretation. Curiously, the outlet also wrote, “While many media outlets take the results to mean the chicken is only half a chicken, the reality of DNA testing is a bit more nuanced.”
However, when the CBC first reported the results of its investigation, the outlet’s headline was (and still is): “What’s in Your Chicken Sandwich?” DNA test shows Subway sandwiches can contain as little as 50% chicken. The story also contained no nuanced description or limitations of the study’s findings.
The CBC did not respond to Ars’ request for comment on the testing or how it should be interpreted.
Ultimately, says Camire, when you go to a fast food restaurant, expect some added ingredients. For large-scale production and standardization, manufacturers use spices and extra protein to enhance the flavor. And, she said, keep in mind that they are often high in salt.
(3/3/2017) This post has been updated and corrected. The article previously stated that the chicken may contain yeast-flavored soy protein, but should have stated that the chicken may contain yeast-flavored soy protein.