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Researchers at the University of Missouri say purple corn could offer a natural alternative to artificial food dyes and new opportunities for farmers in the region.
Their latest study comes as food and drug manufacturers face mounting pressure from consumers and state and federal agencies to phase out petroleum-based dyes. Previous research suggests these synthetic color additives can increase risks for certain cancers, allergies and behavioral changes in children.
The Trump administration last year asked food manufacturers to voluntarily phase out six dyes and requested they remove another — FD&C Red No. 3 — from products before Jan. 15, 2027. FD&C Red No. 3, also called Red 3, gives maraschino cherries and many candies and popsicles their bright color.
One of the industry’s challenges with switching to plant-derived food dyes is that they tend to break down and lose color when exposed to heat, ultraviolet light, oxygen or acidic conditions.
But Pavel Somavat and the other University of Missouri researchers found promising results with shades of red extracted from a dark plum-colored corn variety native to South America. It’s called “maiz morado,” which translates to “purple corn.”
“We show that the colorants sourced from [purple] corn are very, very thermally stable. That’s a good thing,” Somavat said. “We cook these natural pigments at 250 Fahrenheit for more than one hour, and still, most of the colorants remain intact.”
They also found colors from purple corn held up well across a seven-week study period in both low- and high-acidic beverages stored at different temperatures.
Terri Boylston, associate chair of food science and human nutrition at Iowa State University, sees potential with the scientists’ test results. She’s not involved with the research.
“We're in a position now that anything that has a potential for being used as a natural colorant in food products, we really need to … fully investigate and determine if it is going to be a viable option or not,” Boylston said. “And if it is, that's a great opportunity for the food industry overall.”
She emphasized food manufacturers have sought alternatives to synthetic dyes for decades.
But producing and using natural options that are shelf stable and economically feasible to mass produce is no easy feat.
Potential benefits for health — and farmers
Beyond the visual component, Somavat and the other researchers are exploring the potential health benefits from consuming foods and beverages with colors derived from purple corn.
Like blueberries and cherries, purple corn gets its color from anthocyanins, a group of red, purple and blue pigments with antioxidant and anti-inflammatory properties. Research indicates eating foods rich in anthocyanins can help reduce risks for diabetes, cancer, obesity and cardiovascular disease.
Somavat said one of the advantages of purple corn is that these pigments are concentrated in the thin, exterior layer around the kernel, called the pericarp.
“If you think of blueberries or if you think of other natural sources of [anthocyanins], like grapes, you have to work with an expensive material, and you have to work with the whole thing,” Somavat said. “Once you extract the pigments, the processing residue has no economic value.”
With purple corn, the pericarp could be used for natural food dyes while the other 90% of the kernel could be sold for livestock feed or ethanol, Somavat said.
“There are many advantages of taking this approach to extract natural red colorants, and farmers, processing industry – they all get value-added alternatives with this work,” he said.
Somavat and his team have worked closely with Sherry Flint-Garcia, a research geneticist with the U.S. Department of Agriculture's Agricultural Research Service, to analyze dozens of varieties of corn.
“We're looking for other sources of these pigments that are from all over the U.S. and other places in Mexico and South America,” Flint-Garcia said. “Maiz morado is by far the best at this point in time.”
But there’s a hitch. Maiz morado does not grow well in the U.S.
Over a Zoom video, Flint-Garcia held up several dark purple ears of the South American variety harvested in Missouri. They were thin and shorter than hotdogs.
“If you planted 1,000 seeds of maiz morado, you might be lucky and get 1,000 seeds back,” she said.
The primary barrier is the length of sunlight hours during the growing season, Flint-Garcia said. On the summer solstice, Missouri receives roughly 15 hours of daylight. But maiz morado and other varieties adapted to environments closer to the equator need long nights to develop tassels and silks for pollination.
That’s why Flint-Garcia and her team are developing hybrid purple corn varieties that thrive in the Midwest. To explain the process, she used the analogy of dog breeding.
“If you have a pug and a beagle, those are different breeds and pure breeds. If you cross them together, then you make a crossbreed like a puggle,” Flint-Garcia. “We have the same thing in corn.”
But the process of combining traits in corn to have high yields and high concentrations of anthocyanins takes years. After the initial crosses between maiz morado and yellow dent corn, the most widely planted corn in the U.S., Flint-Garcia and her team selected the offspring with purple pigment to breed again with yellow corn. They’ve repeated that process across more generations.
“We're kind of at the proof of concept phase with these initial ones,” Flint-Garcia said, holding up a dark purple ear of corn that was the same size as the yellow corn. “They're not the perfect ones yet. I think I have about two more years left before I can start to make hybrids.”
Along with the natural food dye project, Flint-Garcia is developing pigmented corn varieties that grow well in the Midwest to produce red, pink and blue tortillas.
“I think this is a niche environment that can provide a lot of opportunities for local economies,” Flint-Garcia said. “Maybe some of the smaller farmers can grow these varieties and have a little bit more of a better profit margin.”
Bringing natural dyes to market
For food manufacturers to shift to natural dyes, Boylston at Iowa State University said they need consistency in the quality and supply of ingredients.
“With the natural colorants, you're relying on nature,” Boylston said. “You're going to have more variability, due to weather, its variety, growing conditions — all those factors that are going to affect not only the color but also the availability.”
Natural food dyes also tend to be more expensive than synthetic options. Even if the cost difference seems small, Boylston said it can have a significant economic impact, given the scale of the food industry.
And food manufacturers can run into unexpected and costly technical challenges. Boylston gave the example of M&M’s. The candy’s manufacturer is releasing a version with natural dyes on Amazon this month, The Wall Street Journal reports.
But the initial roll-out won’t include blue and brown coated candies. One of the key ingredients for replacing the two colors left a sticky film in the manufacturers’ equipment, which has been “gumming up” the process and will require upgrades.
However, Boylston said the future of natural and plant-based food colors does not rely on manufacturers, researchers and farmers alone.
“I think it's also on the consumers to think about — how important is the color of the food to the overall quality of the food,” she said. “Is it okay that it's the color it is as long as it's got good flavor and good nutritional value and is safe?”
This story was produced in partnership with Harvest Public Media, a collaboration of public media newsrooms in the Midwest and Great Plains. It reports on food systems, agriculture and rural issues.
