Sweet possibilities

November 20, 2011

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Some like their sweet potatoes mashed, some french-fried, and still others prefer them topped with pecan, brown sugar and marshmallows.

Researchers at NC State have more exotic tastes for the Thanksgiving staple. They favor sweet potatoes seasoned with deep-sea bacteria and converted into ethanol, used as safe starches for diabetics, or ground into flour and made into dog treats.

It’s a new world for sweet potatoes, and a promising one for North Carolina, which produces more of them than any other state.

Go fetch – a sweet potato?

A new NC State research project seeks to bring sweet potatoes to an unexpected member of the family: the dog. Dr. Mike Boyette, a professor of agricultural engineering is working with farmers to dry sweet potatoes in tobacco barns and later turn them into dog treats.

Once sweet potato farmers sort out those spuds rated U.S. Number One — the most popular and profitable ones — they’re left with thousands of pounds a day of less marketable tubers, Boyette said. These typically go to processors for other uses.

Boyette and colleagues are investigating whether the pet food market may be a better destination for these potatoes. Once dried and ground into flour, gluten-free sweet potatoes are ideal ingredients for dog treats, since many dogs are gluten-intolerant. If drying and processing can be done cheaply, North Carolina sweet potato flour could be a viable alternative to foreign flour.

“The idea was, let’s chip and dry some domestic sweet potatoes,” Boyette said. “We can guarantee a better quality, we can guarantee a better sanitation and all that sort of thing — and hopefully we can do it at a profit.”

Safe starch for diabetics

For people with diabetes, a carbohydrate-rich food that doesn’t drive up blood sugar is a rare find. Research by Dr. Jonathan Allen, a professor of food science, has uncovered the sweet potato as a viable food for diabetics.

“It doesn’t really spike glucose the way some other carbohydrate-rich foods do,” Allen said.

Allen initially suspected that protein in the sweet potato limited its glycemic index. Subsequent research indicates that protein is not the limiting factor. Allen now suggests that fiber content plays a role. Further study is necessary, but sweet potato extracts and diets rich in sweet potatoes could someday help diabetics manage their disease.

Fuel of the future?

For several years, Dr. Craig Yencho, a professor of horticultural sciences, has been investigating the sweet potato’s potential as a sustainable fuel source. He and colleagues have worked to develop a hybrid, super-starchy sweet potato with white skin and flesh. Cultivation with deep sea-bacteria could enable these sweet potatoes to convert all their starch into simple sugars ripe for processing into ethanol.

At this point, Yencho said, cost is the chief barrier to widespread use of sweet potatoes in biofuels. The sweet potato holds potential, he said, but it still appears most often on a dinner plate.

And its popularity there is growing, Yencho said.

“The options for sweet potatoes as a food source are increasing significantly, and our farmers are taking good advantage of this opportunity,” he said. “The processing of sweet potatoes into french fries has been increasing significantly as of late, and it is now almost common for sweet potato fries to be offered as a menu option in restaurants. This represents a big change and sales are increasing quickly.”