Would you rather eat bugs or plants?
If you picked the latter, you're in luck: Researchers are developing better vegetable-based alternatives to cochineal, a commonly used red food coloring made from crushed insects. One of the most promising candidates is the purple sweet potato.
Purple sweet potatoes can be used to produce a range of colors, from light pink to deep purple, says Stephen Talcott, an associate professor of food chemistry at Texas A&M University.
Demand for natural food colorings has risen in recent years, as consumers are shying away from artificial food dyes, which have been linked to allergies and behavioral problems such as hyperactivity in children.
The pigments in purple sweet potato, called anthocyanins, are "among the most desirable for their superior color and stability," says Talcott, who presented his work at the American Chemical Society's annual meeting in Indianapolis earlier this month.
While colorings made from purple sweet potatoes are already on the market, extracting the pigments is difficult and inefficient, and much of the color can be lost to oxidation during processing, says Talcott.
Purple sweet potatoes are rich in pigments that offer an alternative to cochineal, a red food dye made from crushed insects.
Photograph from Studio Eye/Corbis
"We are working on extraction and processing methods that dramatically increase the color and yield of the anthocyanins," he says. "I certainly hope to see a majority of foods colored with 'natural colors' in the near future."
Purple carrots and red grapes also yield red-hued dyes that can be used in food, although the tannin content of grapes imparts a slightly bitter flavor.
A Colorful History
One common source of natural food coloring is cochineal, also called carmine, carminic acid, or Natural Red 4. The dye is made from Dactylopius coccus, commonly called a cochineal bug. It's a type of scale insect—tiny parasites that latch onto plants to drink their sap—that lives on cactus.
"They kind of look like plant pimples," says entomologist Gwen Pearson, author of Bug Girl's Blog. "They don't have wings or visible legs; they're basically just little sacks of juice. Which means they need a powerful defense."
That defense, in the cochineal bug's case, is a crimson-hued substance called carminic acid that tastes unpleasant to would-be predators such as ants. Humans have used this as a dye for centuries; the Aztecs put it in medicine, cosmetics, textiles, and even tamales, says Amy Butler Greenfield, author of the book A Perfect Red, about the history of cochineal.
"It's the most intense natural red dye in the world, and it helped people and cultures in southern Mexico survive the devastation of the [Spanish] Conquest," says Butler Greenfield. "Nowadays it continues to be a key export for poor farmers in a number of disadvantaged regions. Big producers include Peru and the Canary Islands."
Cochineal has been used in U.S. food and drug products for decades, but it was often hidden under umbrella terms like "natural colors" or "color added" on ingredient lists. In 2009, the FDA revised its regulations to require manufacturers to specifically list cochineal and carmine.
Since then, increasing public awareness of cochineal's source is making some consumers squeamish and putting pressure on the food industry to find alternatives.
Lipstick requires red dye, which may be sourced from purple sweet potatoes.
Photograph by Rebecca Hale, National Geographic
The Center for Science in the Public Interest recently launched a petition aimed at yogurt maker Dannon, which uses carmine in some of its yogurts.
"I have nothing against people who eat insects, but when I buy strawberry yogurt I'm expecting yogurt and strawberries, not red dye made from bugs," CSPI executive director Michael F. Jacobsen said in a press release. (See how the "Bug Chef" cooks up insects.)
It's not just about the ick factor, CSPI argues. Cochineal can cause rare but life-threatening allergic reactions, according to a 2007 study by University of Michigan allergist James Baldwin.
But entomologist Pearson says she doesn't see what all the fuss is about.
"I agree that it should be labeled, but the research that CSPI cites is talking about three allergic reactions reported in ten years," she said. "In terms of U.S. food safety, we have much larger issues in front of us right now. Why worry about this?"
Besides, says Pearson, most of us probably eat bugs whether we know it or not. Shellac, used to coat candy and produce, is made from the waxy secretions of another type of scale insect. And the FDA permits low levels of "insect filth" in chocolate, coffee, spices, dates, figs, and several other food products.
Does that mean there might even be bugs in … purple sweet potatoes?
"Sure," says Pearson. "In biology, there's never an empty niche. If there's an edible thing, something, somewhere, is going to be eating it."