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FALL 2007

Vol. 08, No. 1


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Flawless french fry

Engineering a flawless french fry

Asunta Thompson was just a sprout of a girl with a very grown-up name. Her parents named her after an Italian friend, but that handle seemed awfully big for such a little thing. Everyone called her Susie instead, and it suited her. She was tomboyish and spirited and brown-skinned from playing outdoors all summer long.

Susie Thompson grew up on a seed potato farm near Barnesville, Minn. When she was 5, she begged her father to let her help with the potato harvest. She wanted to work with the hired women who stood on the potato harvester as it scooped up potatoes from the field, moved the spuds through a series of conveyer belts, then dumped them into the box of a truck driving alongside. The women stood along one of the conveyer belts and plucked out dead vines, rocks, dirt clods and rotted potatoes as the rest of the harvest rolled through to the truck box. It looked like the greatest job in the world.

Susie's dad agreed to let her help. When the big day came, she clambered up the dark green Lockwood harvester to join the other workers. She had to stand on a 5-gallon pail to reach the conveyer belt and she wore brown cotton-knit work gloves to protect her little hands. It was hard, boring work, but Susie was in heaven. She felt the warm sun on her back and breathed in the good smells around her. The comforting aroma of tilled soil. Diesel exhaust from the John Deere tractor pulling the harvester. The slightly sweet odor of dead vines. On that day she knew she wanted to be a farmer when she grew up.

Forty years have passed and Thompson's favorite spot is still the potato field. Thompson is the state's only potato breeder and one of only 11 potato breeders nationwide. Now she's zeroed in on a discovery that could make a difference to thousands of potato farmers across the country.

Thompson is developing two selections of russet potatoes that show promising resistance to sugar ends. Sugar ends. The term sounds so harmless - like a folksy nickname or grandma's home remedy. In fact it's a complex condition that costs American farmers and processors millions of dollars a year. When the potato plant is deprived of cool weather and rain, it can deposit too much sugar on one end of the potato. When that potato is fried, the sugary end will turn dark as if burnt. Now imagine what happens when thousands of potatoes with sugar ends are sliced and cooked into millions of fast-food french fries. Customers don't want fries with burnt-looking ends. They want long, crisp, uniformly golden french fries, just like they see in TV commercials.

Two-tone fries can dent the potato producer's wallet. When the Red River Valley was pounded by heat and drought in the 1980s, the area's potatoes suffered with sugar ends. The Valley's potatoes were so affected that the big potato processors like Simplot pulled their contracts. Many processors moved their business to the "irrigated sands" of west-central Minnesota. The sands are a veritable Garden of Tater Eden. These areas have a light, loamy soil potatoes love. They also have been outfitted with irrigation, which keeps the fledgling "tubers" - the enlarged stems that will grow into potatoes - from getting too warm or too dry.

Even so, sugar ends remained a problem on both irrigated and non-irrigated land. Part of the issue is that an ever-growing chunk of the potato industry is devoted to producing frozen french fries for our fast-food nation. And the industry standard for french-fry potatoes is the Russet Burbank, which is highly susceptible to sugar ends. Potato scientists all over the United States have spent a couple of decades scratching their heads over sugar ends. They've tried, with some success, to find better ways to raise the persnickety Russet Burbank. But the real answer could lie in building a better potato, which is where Thompson comes in.

Thompson uses the word "beautiful" a lot. Mostly to describe potatoes ("it has a beautiful, red skin"), but also to describe good research, nice-looking potato fields and even certain potato diseases. "Sometimes diseases are beautiful," she says, tooling an SUV down state Highway 17 in northeastern North Dakota. "I tell that to my students. Sometimes diseases show the magic of nature."

She is on her way to a potato test plot north of Hoople, N.D. Hoople bills itself as "Tater Town U.S.A." It's located in Walsh County, the No. 1 potato-producing county in North Dakota. Thompson drives by impromptu roadside stands with signs advertising "Fresh new potatoes" and potato warehouses and implement dealerships and neat-as-a-pin farmsteads.

She seems perfectly at home here. She gives color commentary on the farm fields she drives by: "Look, there's water standing in the ditches. That never happens up here." She points out spotty growth in a nearby cornfield. She turns up the car radio to listen to the farm reports. In a typical summer, Thompson logs thousands of miles driving between test plots here and in Larimore, Tappen and Park Rapids, Minn. She oversees planting, checks plant progress and logs data like potato flower color or tuber growth. She also helps out with harvest. "The days I really enjoy are being out in the field," she says. "When those little potatoes come up over the digger, it's like opening Christmas presents."

Out here in the field, you see traces of the enthusiastic little girl who longed to be a farmer. Her memories of those early days remain remarkably clear. She recalls wearing a green shirt for that very first potato harvest. She talks of tying a bandana "like a bandit" around her face when the wind whipped the fine, loamy soil around. She speaks of envying how her father could hoist a 100-pound potato sack onto his shoulder. She wanted to do that too, but even in high school she weighed just 10 pounds more than a full potato sack

Thompson chose to study agronomy when she enrolled at NDSU the fall of 1979. She'd already picked up a lot about farming from her dad and FFA. Now she wanted to learn the science behind everything farmers did

On NDSU's campus, Thompson made an impression. She was one of the few women in her agronomy classes, yet she didn't try to be one of the boys. She wore a dress to class every day of her first freshman quarter. She still likes to dress up. Her chic pencil skirts and stylish pumps make her look more like a corporate executive than a potato breeder. When she heads to the potato fields, she wears perfectly pressed blue jeans and a trendy little top. Pink glittery toenail polish peeks out from strappy sandals. "It's OK to be a girly girl and be in ag," Thompson says. "I march to my own drum. I am a maverick. I don't necessarily do what people expect. I believe people should be hired based on their knowledge, skills and passion, not on their gender."

Unfortunately no amount of knowledge, skills or passion could make Thompson a farmer. By her junior year in college, she faced a hard truth. She would not take over her dad's farm. He was too young to retire and there was little land available nearby to purchase. She would have to find something else to do. Something that still allowed her to work alongside farmers.

She got her first taste of plant breeding when she took a job at Pioneer Hybrid International's spring wheat-breeding station in Glyndon. She was just a plebe, taking field notes and helping with harvest, but she loved the work. Thompson then landed a job alongside legendary NDSU potato breeder Bob Johansen. Johansen had developed popular potatoes with lyrical names like the Norgold, the Norland and the Norkotah. Everyone in the potato industry knew Bob Johansen. He was the ideal mentor. As Thompson worked full time for him, she also pursued a master's degree. By the time she completed graduate school, she faced three job offers. One was at the University of Maine. One was with a Carnation plant in Washington. Another was with the University of Idaho's off-campus potato research center.

She chose Idaho. "I took the lowest-paying job in the smallest community," she says, grinning. "After so many drought years, I'd sensed the potato industry would be changing, and I knew Idaho had a lot of experience with irrigation. Also, I really wanted to earn a Ph.D., so Idaho was the perfect fit."

The state was potato Mecca. The Aberdeen-based research station was in Bingham County, the top spud-producing county in the United States. The region exposed Thompson to potato varieties she'd never worked with before. And Thompson would work among some major potato farmers.

By 1998 Thompson had earned her Ph.D. in plant sciences and gained valuable knowledge about russet potatoes and irrigation farming. Her dissertation was on sugar ends. Three years later she'd come full circle. She applied for an assistant professor job at NDSU. The position also meant taking on Bob Johansen's former job as a potato breeder. And just in time. Sugar ends had again reared its ugly head in Minnesota and North Dakota.

As far back as 1929, an Australian researcher known only as "F. Penman" published the first journal article on sugar ends. He called the condition "glassy end tissue" because a severe case of sugar ends can turn a potato's flesh translucent.

Sugar ends still didn't become a widespread problem until french fries became more common. During the second world war, a brilliant businessman named Jack Simplot revolutionized ways to bring convenient, non-perishable foods to the troops overseas. First he introduced dehydrated diced potatoes, which were handy for military cooks but not popular with the poor GIs who had to eat them. His next invention was far more successful: frozen french fries.

Frozen potatoes remained popular after the war. The frozen fry market really took off in the '70s and '80s, as time-strapped families ate more meals at fast food restaurants, where they ordered their Big Macs with side orders of fries. This pumped up the demand for "processing potatoes," or potatoes that are made into french fries.

The kingpin of processing potatoes is the Russet Burbank. The Burbank helped to secure Idaho's place as the No. 1 potato-producing state in the nation. The mighty russet has become such an industry standard that potato-processing equipment is built to fit the Burbank's dimensions. It is known for great yields and its ability to be grown in a wide range of environments. Its long, blocky shape allows processors to get the maximum number of long fries out of one spud.

But the Burbank has a few chinks in its armor. It's finicky about moisture. It needs a long growing season. And it is highly susceptible to lots of diseases, pests and disorders like sugar ends.

To be fair to the Burbank, many potato varieties can develop sugar ends if conditions are bad enough. Most potato scientists believe the one-two punch of heat and dryness will do the damage. Thompson, however, believes heat alone can do the trick. She bases this on "beautiful research" done by a group of German scientists. They put copper boxes around different stolons (underground stems) of the same potato plant in a hydroponic system, then heated the boxes to different temperatures to induce stress. The stolons zapped by the most heat developed tubers with sugar ends.

Now translate those unfavorable conditions to a potato field in North Dakota. In order to thrive, a potato needs warm sunny days, cool nights and moisture. But if the region is hit by a late June-early July heat wave, temperatures won't drop at night. So at a critical time in the tuber's growth cycle - when the fledgling potatoes are the size of a nickel - the soil 6 to 8 inches below ground can climb to more than 65 degrees. This overly toasty environment can damage the plant. It begins depositing sugar, rather than the desired starch, in the cells on the stem end of the tuber.

Unless the sugar ends are extremely bad, you won't see any visible signs of damage. That is, until you slice up the spud and fry it in hot oil. Then the sweet ends fry much darker than the rest of the french fry. Thompson calls this phenomenon the Maillard reaction. Even if you've never heard the term, you've seen it. It's what causes bread to toast. Potatoes with sugar ends contain a lot of simple sugars. When those simple sugars come in contact with heat (as in hot oil), the sugars break apart and react with amino acids in the tuber. The result is a browning reaction, similar to caramelization.

The processors, who buy potatoes from farmers and sell the processed potatoes to fast food restaurants, are seriously concerned about sugar ends. So serious they'll pay potato farmers incentives for potatoes without it. "The competition increases every day," says Gregg Halverson, a 1971 NDSU graduate and president of Black Gold Farms, one of the largest chip potato operations in the United States. "If my neighbor has perfect potatoes and I don't, guess which ones the processors want?"

In a room off NDSU's West Dining Center, a panel of somber taste-testers sample french fries. Thompson and a group of NDSU staff have gathered to taste, judge and compare several new varieties of fries.

This isn't recreational french fry eating. It's work. You can't douse a batch in ketchup because you feel like it. All fries are cooked and salted uniformly, and each batch is served on an anemic-looking paper plate. Taste-testers are NDSU volunteers who are trained in what to look for in a french fry. They are instructed to not eat, smoke, brush their teeth or drink anything but water for a couple of hours beforehand. And when it comes time to taste, they must concentrate on the color, texture, taste and appearance of each fry. They aren't allowed to discuss results among themselves, even when a batch of fries taste nasty. And some do. The adjectives used on the taste-test scorecards sound like the unsavory cousins of the seven dwarves. Blotchy. Lumpy. Greasy. Mealy. Pasty. Slimy. You get the picture.

Thompson is developing several potatoes with great potential, but her star pupil - a sugar end-resistant russet - is in the taste trial today. It's known only as the AOND95249-1RUSS. The 1RUSS seems to have everything going for it. Less sugar overall, so it fries nice and light. A high percentage of dry matter. (If a potato contains too much water, that water will be displaced by oil in the frying process, creating a greasier fry.) A uniform shape and the length to produce lean, lanky fries. Most importantly, a resistance to sugar ends.

"I'm really proud of what we're doing in breeding," Thompson says. "It takes forever, but our efforts are really starting to take hold."

The 1RUSS has scored high in earlier taste tests. But it doesn't do well in today's test. Neither do two other widely grown russets, the Ranger Russet and the Umatilla. Even the venerable Russet Burbank tanks. "Maybe we just didn't grow it well," says Thompson of the 1RUSS.

She's not discouraged. She knows there will be many more taste-tests down the line. The average new selection gets more scrutiny than a presidential candidate. It will be grown in different conditions, subjected to endless taste-tests, sent to tissue-culture labs to have any potential diseases removed. The average time for a selection to hit the market is 10 to 16 years.

And then the hard work really starts. The potato needs to gain wide acceptance from the fast food giants. The executives of the QSRs - that's industry-speak for "quick service restaurants" - are so concerned about consistent, high-quality fries that they won't change their most important ingredient easily. "They need to know they can tell their people in Helsinki and their people in Denver that they need to cook their frozen fries for x number of minutes and at x temperature, and that they're going to have the same quality product," Thompson says. "So they're very concerned about changing varieties because that might mean they have to change a protocol. It has to work out economically for them."

Even so, potato breeders have made a dent in the Russet Burbank monopoly. At one time 99 percent of all french fries came from Russet Burbanks. Today that number has fallen to 65 percent. Someday Thompson's 1RUSS could join the Burbank's contenders. The officials at the processing plants have already shown a lot of interest in Thompson's selection, as have many potato farmers. It could be NDSU's first successful, highly resistant russet for french fry processing. (NDSU's breeding program has released several russets, but none have been widely used to make french fries.)

"If someone could breed for (sugar-end) resistance, that would be huge," says Duane Maatz, president of the Northern Plains Potato Growers. "Susie has already done a lot for the potato industry in North Dakota. One of the really great things about her is she is very good at being the field person. She likes being in the field; she likes talking to growers. She has that practical side of a researcher you don't always get. I'm very happy she's that type of researcher. I would hate having her lost in a laboratory."

Thompson finally reaches the test plot by Hoople. The field is in full bloom - a mass of white, lavender and deep purple potato flowers. Their surprisingly strong, sweet fragrance hits you the minute you open the car door. Thompson climbs out of the SUV and roots around in the back seat for a clipboard and gloves. She replaces her strappy sandals with farm-friendly socks and running shoes. Goodbye, pink toenails.

Thompson's job today is to chart colors of potato flowers. She walks so quickly through the soft fields that it's hard to keep up with her. It's a bordering-on-hot July day, and a warm wind whips her brown hair into her face. Absent-mindedly she pulls off the long-sleeve shirt over her spaghetti-strap top and ties it around her waist. She steps easily over the hilled rows where the potatoes are planted. She stoops to examine blossoms, stops to snap photos of certain flowers, squints slightly, jots notes on her clipboard. Two different colors of flowers in one section are a bad thing, she explains. That means two different types of seed were accidentally mixed.

This is just one day in a potato breeder's life. In her quest, Thompson will spend many more days peering at flowers, digging up tubers, participating in french fry taste-tests and crossing plants in the greenhouse, bumping along North Dakota back roads to reach remote test plots, organizing field days to show farmers the latest developments, and giving out quirky awards to motivate her research assistants during the hard work of potato farming. All in the hopes of one day producing a perfect french fry.

--T. Swift

Student Focused. Land Grant. Research University.