Purple sweet potatoes turn pie into possible cancer fighter
Wednesday, December 1, 2010
Nutrition scientists at Kansas State University could be accused of carrying Purple Pride to extremes. But the purple sweet potato pies they created for Thanksgiving were a practical application of research.
The story of Purple Pride Sweet Potato Pie starts with a sweet potato breeder named Ted Carey.
Carey was a horticulture professor at K-State before he moved to Ghana to work with the International Potato Center.
At K-State, Carey got seeds from purple sweet potato parent plants from the potato center's germplasma bank in Peru. He stuck the seeds in fertile Kansas soil. When they grew, he cloned the most colorful ones.
Enter scientist George Wang
George Wang is a research scientist in K-State's department of human nutrition.
The bright purple color meant the potatoes were loaded with anthocyanin, a pigment associated with reduced risk of cancer. Cancer preventative nutrition is Wang's specialty. Did the potatoes have anticancer abilities? He decided to find out.
His research attracted Soyoung Lim, doctoral candidate in human nutrition from Korea, and Tzu-Yu Chen, master's student in human nutrition from Taiwan.
They found that purple sweet potatoes have a significantly higher anthocyanin content and more antiaging and antioxidant components than other sweet potatoes.
Lim also found that two anthocyanin derivatives -- cyanidin and peonidin -- inhibit human colon cancer cell growth in the cultured human colorectal cancer cells.
A bounty of purple potatoes
The purple sweet potato harvest in Kansas was a good one this year. Jason Griffin at the K-State John C. Pair Horticultural Center near Wichita sent 400 pounds of the special spuds to Wang's lab.
The team decided to turn the bumper crop into people food. Could purple sweet potato pie become the next big functional food?
The team traded test tubes for pie pans for a day.
"Our research is focused on cancer prevention," Wang said. "We hope to translate our discovery from lab to humans. The pies could be used to test bioavailablity of anthocyanins in humans.
"I hope we can promote a health food for functional cancer prevention."
The test pies, made using recipes formulated with the help of Delores Chambers, associate professor of human nutrition, were a success with taste-testers around the College of Human Ecology.
"They were impressed by the unique color as well as the great taste. Some even suggested we sell the pies at football games since the color represents K-State," Lim said.
Healthy and loyal royal
The naturally bright purple pie is healthier than regular sweet potato or pumpkin pie.
"Pumpkins and orange-fleshed sweet potatoes are high in carotenoids -- vitamin A precursors. But the purple potatoes have higher levels of anthocyanins, dietary fiber and vitamins. And they are naturally sweeter, so we can cut down on the sugar content," Lim said.
After testing pies, the lab still had 395 pounds of potatoes. So Lim took orders. Then she assembled her research team -- Linette Ngaba, senior in dietetics, Junction City; Tzu-Yu Chen, master's student in human nutrition, Taiwan; and Jaeyong Kim, visiting scholar in human nutrition -- and baked more than 40 pies.
Purple Pride Sweet Potato Pies sold for $10 each. Profits will go into a Kansas State University Foundation fund to support student travel and research.
In the future Chambers will lead sensory tests on the pies at the Sensory Analysis Center
Purple sweet potatoes are not on the market yet, so Purple Pride Sweet Potato Pies aren't on grocery stores shelves. But the potential is there, and Wang, Lim and the research team are confident they can prove the power of the purple pies.
Watch a segment about the purple sweet potato pie featured on K-State's Wildcat Watch.