Orange Gold

CALS technology adds value to the sweet potato

The once-humble sweet potato, for centuries fed mostly to barnyard animals and consumed in the United States only as a holiday treat, is enjoying a new popularity, thanks to N.C. State University researchers and their commodities and industry partners.         

“It used to be said that sweet potatoes were grown by poor folks and eaten by poor folks,” said Dr. Michael Boyette, a sweet potato researcher in N.C. State’s College of Agriculture and Life Sciences.          

In the long run, however, sweet potatoes have proven to be a popular crop, with a value that keeps growing. That’s due in large part to three decades of research by Boyette, his team and his collaborators. Their efforts soon will yield a huge financial harvest for growers and processors of the orange vegetable.           

Boyette, Phillip Morris Professor in CALS’ Department of Biological and Agricultural Engineering, spoke Aug. 12 at a groundbreaking ceremony near a future $20 million sweet potato processing facility in eastern North Carolina.         

That’s where, as of next spring, Carolina Innovative Food Ingredients Inc. (CIFI) — a new subsidiary of giant Richmond, Va.-based international tobacco supplier Universal Corporation — initially will help provide a new market for sweet potatoes. The crop will be supplied mostly by North Carolina farmers.          

Boyette speaks at the Aug 12 groundbreaking ceremony.
Boyette speaks at the Aug 12 groundbreaking ceremony.

CIFI’s new operation will rise on rolling, rural countryside north of Nashville, almost next door to a complex of its sister company, Universal Leaf North America U.S. Inc. The new company, expected to create about 64 jobs, later will process other vegetable and fruit products.           

Using an innovative procedure developed by Boyette and his N. C. State research team in collaboration with Universal Corporation consultants, CIFI initially will focus on processing sweet potatoes that are sound and wholesome but currently have been unused due to surface defects and less desirable shapes and sizes (that do not affect the sweet potato’s high nutritional assets). These sweet potatoes are processed into value-added, high-quality, food-grade dehydrated and juiced ingredients for human and pet consumption.          

Clay Frazier, ULNA president, pointed out CIFI’s potential benefit to the state. “Sweet potatoes are an important rotational crop and an alternative source of income for tobacco farmers,” he told the more than 150 local producers and federal, state and county elected officials and other dignitaries at the groundbreaking.          

Jim Nagy, CIFI president, said the operation “will target markets for the health and wellness beverage market, a growing $60 billion global industry; healthy foods, a diverse $143 billion U.S. market; and the global pet food business.”           

Sue Langdon (right) of the N.C. SweetPotato Commission and USDA researcher Van-Den Truong participated in the groundbreaking.
Sue Langdon (right) of the N.C. SweetPotato Commission and USDA researcher Van-Den Truong participated in the groundbreaking.

Sue Langdon, North Carolina SweetPotato Commission Inc. executive director, who has cheer-led the state’s sweet potato industry’s growth in recent years, summed up the day’s prevalent zeitgeist: “We’re living our dream,” she said.         

It is a dream that took several decades to develop, however.

“When I came to N.C. State in the mid-1980s, the sweet potato was a niche industry that seemed to be hanging on by its fingernails,” Boyette said. “Producers were slow to market to restaurants and create packaged sweet potato goods for grocery stores. At about the same time, our friends in Louisiana came out with the new variety: Beauregard. Some said it shined like a new penny compared to the dull, pitiful and often grossly elongated roots from North Carolina. It appeared that North Carolina was at a real disadvantage as we fought other states over a piece of a shrinking pie. The sweet potato industry in North Carolina clearly had many problems.           

“We had been growing sweet potatoes in North Carolina for well over 300 years,” Boyette added, “and had been selling them pretty much as they did in the beginning – out of a bucket, box or basket – saying, ‘Here are your sweet potatoes, now you go figure out how to cook them.’           

“But we live in the age of fast food, microwaves and nine-minute meals” he said. “We needed to modernize. To their great credit, the North Carolina SweetPotato Commission, N.C. State University and the N.C. Department of Agriculture and Consumer Services and others tackled this problem with now-spectacular results.”           

And thanks to product development and research, consumption continues to rise each year.         

Today, more than 300 North Carolina growers, on more than 66,000 acres mostly in the eastern part of the state, produce more than half of the total U.S. crop. In 2012, the state produced 1.24 billion pounds of sweet potatoes, a nearly 68 percent increase in harvested acreage since 2002.           

A sweet potato slicing process at work.
A sweet potato slicing process at work. New sweet potato products have contributed to increased U.S. demand.

New products – most notably the sweet potato French fry and pet foods – and an increased awareness of the vegetable’s nutrients contributed to increasing U.S. demand.          

“Sweet potatoes are gluten free, non-GMO, and are a source of resistant starch and fiber, resulting in a low glycemic food index — and have high beta-carotene and vitamin C levels,” notes John Kimber, CIFI’s CEO and project director for the N.C. SweetPotato Commission Foundation.           

Researchers were challenged early on to extend the sweet potato’s shelf life. To that end, Boyette’s main work has been on developing computer-controlled storage facilities that extend a once-seasonal product to a year-round item. His recent work centers on finding the best methods to dry sweet potatoes for animal and human consumption.           

“Properly drying sweet potatoes can present some significant problems,” Boyette said in an earlier interview in his Weaver Labs office. “Primarily, the problem was getting the air through them. We tried drying slices in the sun – didn’t work with our humidity – and in a small experimental tobacco barn that did work. We made dried material for feeding tests and collected a lot of very useful data, and knew then we were on to something. But for one reason or another, it was an example of a good idea without legs.           

“We talked to a feed broker who told us that U.S. pet food makers were concerned about the quality and traceability of the five million pounds of sun-dried sweet potato chips imported from China each year,” Boyette said. “Buyers were willing to pay a premium for U.S.-produced chips.”             

John Kimber, who’d been collaborating with Boyette’s team in his capacity of project director for the North Carolina SweetPotato Commission guided the researchers to a Rural Advancement Foundation International grant. With that grant from RAFI’s Tobacco Communities Reinvestment Fund, supported by the N.C. Tobacco Trust Fund Commission, in June 2011, the researchers conducted an on-farm chipping and drying test at Barnes Farming near Spring Hope.           

Boyette credits Justin Macialek, a BAE research engineer, with coming up with metal drying boxes similar to the ones used for tobacco.          

“We would stack the potatoes like they stack tobacco leaves – horizontally – then turn the boxes on their side so the sweet potato slices were vertical with room for air to circulate vertically,” he said. “The test was successful with much of the dried material made during that test shipped off to potential customers for their evaluations. The most common comment was, ‘Give us more!’ ”           

Shredded sweet potato product.
Shredded sweet potato product.

Once Boyette and his team had successfully dried sweet potato slices, it was important to make the process more efficient.          

Boyette reasoned that since the sweet potato is 80 percent moisture, mechanically squeezing out the water would more efficient.        

“Using a large commercial juicer, we separated the pulp from the juice,” he said. “To our delight, we discovered that the juice was a very desirable product in its own right, as was the dried pulp. When these materials were displayed at food ingredients shows, they drew the attention of several big food and dry cereal manufacturers.”           

To their surprise, there seemed to be a bigger demand for juice than for pulp.          

Boyette reflected on one aspect of the nature of research: Like the sweet potato, it can be more valuable with an extended shelf life.           

“The success of the sweet potato illustrates how sometimes research just sits on the shelf for years. Then the time is right and it’s found to be extremely valuable,” he said.          

“Land-grant universities do practical research on practical problems, and people benefit from that. That’s what N.C. State University is really good at.          

The ground is broken for the future $20-million sweet potato processing facility in eastern North Carolina.
The ground is broken for the future $20-million sweet potato processing facility in eastern North Carolina.

“Due to accumulated research, in the last two years, my little group has been slicing, dicing, grating, mashing, steaming, cooking, stewing, juicing, squeezing, extruding, drying, grinding, sifting and packing deconstructed sweet potatoes into every product imaginable,” Boyette said.

“It seems that no matter what we have done to the sweet potato, someone likes it and wants more” he said. “We’ve taken a quantum leap. A generation from now, they’ll wonder what took us so long to discover the great potential of that lowly root.” – Art Latham     


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