How do you know that the piece of fish you're buying is Albacore tuna and not tilapia? How do you know the veggie burger is really vegetarian, or that the calorie count is accurate? You don't. A new company is trying to change that using DNA analysis to identify exactly what is in various foods, rather than relying on the label. This week, burgers have been under the company's microscope.

Clear Labs, a Silicon Valley start-up launched in 2014, works with food retailers and manufacturers to make sure that their products are safe and that their supply chains are secure. They do this with genomic analysis. Essentially, the technology can scan a food and say exactly what species are in it—from cow to E. coli. It can also calculate exact calorie counts.

Recently, the company gathered 258 burger products (both meat and vegetarian) from grocery stores and fast food spots in Northern California, and analyzed them. The good news is that, despite some pretty eye-catching (and gross) anomalies—rat DNA in three products; human DNA in one product; two veggie burgers that contained beef—the burgers were overwhelmingly safe to eat. The bad news is that if a calorie count seems too good to be true, well, it probably is: 46% of the samples contained more calories than the label or menu stated.

The overall picture shows that the burger industry has really cleaned itself up since the 1993 E. coli outbreak at Jack in the Box. "The low incidence of hygienic issues surfaced by our study is a testament to the burger industry as a whole and the stringent protocols for safe food handling," the report said. Only 1.6% of the samples had hygienic issues and 4.3% contained pathogens. (And pathogens are often killed by cooking.) As for the rat and human DNA, it's not quite as bad as it sounds. The human DNA probably came from a piece of hair or fingernail—gross but not necessarily dangerous. And the rat DNA likely came from rat feces, which is both gross and potentially hazardous.

But another important takeaway is that calorie counts are consistently underreported. "Fast food menus were especially egregious in misrepresenting caloric values. 38 of the 47 samples we tested had more calories than reported on fast food menus. In 12 of these 38 samples, actual caloric values surpassed reported values by at least 100 calories per serving," the report said.

This is all consistent with a big picture of American food: Our food is generally (slowly, steadily) getting safer. But mislabeling and ingredient fraud is a problem. One in three fish in markets is mislabeled (usually a cheap and/or unsustainable fish is labelled as a more expensive fish). Some Parmesan isn't Parmesan. Some olive oil isn't olive oil. There's very little the average grocery store consumer can do to combat this kind of fraud. But as sophisticated DNA testing like the kind practiced by Clear Labs gets cheaper and more accessible, it will become more difficult to pull off.

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