Food Dye Used in Doritos Offers a 'Jaw-Dropping' Perk

To many consumers, "Yellow No. 5" is best known as the food dye that adds an orange-yellow tinge to snacks and drinks like Doritos, Gatorade, and M&Ms. To a team from Stanford, however, tartrazine, the chemical found in that dye, recently served as a window into living creatures' bodies, effectively making the skin of mice transparent.

• The experiment: For their study published Friday in the journal Science, the researchers rubbed a tartrazine solution onto various parts of lab mice, including their stomachs, scalps, and hind legs, reports the Washington Post. In just minutes, the mice's skin turned "temporarily into a living window, revealing branching blood vessels, muscle fibers, and contractions of the gut," per the Post. "You could see through the mouse," says Adam Wax of the National Science Foundation, which helped fund the study. "I've been working in optics for 30 years, and I thought that result was jaw-dropping."

• The science behind it: The paper notes that the process behind the seeming "magic" of the researchers' experiment is similar to that used in HG Wells' Invisible Man, in which a scientist creates a serum that shifts how the body's cells refract light. In this case, the Stanford researchers discovered that a piece of raw chicken soaked in the light-absorbing food dye solution started turning clear, and that transparency increased the more tartrazine was added.
• Trying it on the mice: That's when they began applying the solution to the mice's skin, at which point "the tartrazine reduced the amount of refraction, the light scattered less, and the tissue appeared clear," offering a view of the rodents' internal organs, per the Post. After the experiment was through, the tartrazine dye was cleaned off the mice, with "minimal systemic toxicity" left behind.
• Applications: So how can this technique be tapped in more helpful ways? Study co-author Guosong Hong says it can be used for everything from nonintrusively diagnosing tumors and observing brain activity to helping expedite tattoo removal, per the Post. The technique has yet to be tested on humans, with certain ethical hurdles to overcome before that can happen. The Economist notes that human skin is also 10 times as thick as that of mice, which adds another challenge.

(More food dye stories.)