Let’s Talk Food: Sweet potato research at the University of Hawaii at Manoa

Sweet potatoes are one of the most important agricultural crops in Hawaii at the present time as it was in ancient Hawaii. The earliest archaeological record of sweet potato dates back to the fourteenth century C.E. in the Kohala Field System.

During peak growing season, sweet potatoes generated $7.3 million. Molokai, with its drier climate, produces a sweet potato industry as well as the high-rainfall areas on the Big Island, however the breeding lines need to be selected.

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Elizabeth Winnicki, Aurora Kagawa-Viviani, Kauahi Perez, Theodore Radovich and Michael Kantar of the University of Hawaii at Manoa conducted studies on and discovered two new Hawaiian sweet potato varieties that outperformed the purple Okinawan sweet potato, presently a very important agricultural crop, especially on the Big Island.

“Our findings call attention to the value of a set of Hawaiian sweet potatoes as “heirloom.” These genetically distinct traditional cultivars have unique value in local markets and present an opportunity to increase cultivar diversity in the markets and fields, farmer income and diversified agriculture, all while contributing to reinvigoration of Hawaiian cultural heritage.”

The researchers noticed that the mohihi variety yielded 50 seedlings. So decided to conduct a research study to yield more and create economic value for the farmers.

Starting in 2018 and working on this project for a year, these researchers selected 12 of the 50 varieties and planted them in different climates: fall in Waimanalo in 2018 and spring in Poamoho and Waimanalo in 2019.

After harvest, they collected information needed to check yield, metrics, root shapes, damage susceptibility, color and sucrose content. One variety outperformed and another matched the favorable qualities of the Okinawan sweet potatoes.

“Elevated sucrose content in sweet potatoes is associated with improved taste and increases their market value.”

However, the sweet potato weevil (Cylas formicarius) a common sweet potato pest in Hawaii, was an issue, especially in areas with “high rainfall, heavy clay soils, and a recent history of sweet potato cultivation.”

There is a preferred shape for the market as well as color. The purple flesh of the Okinawan sweet potato was desired so HM 34 and HM 26 came out as the best. “From this study, we identified commercially viable lines from the ‘Hawaiian Heritage’ breeding material. Lines HM 34 and HM 26 have the most potential for fresh market production, whereas HM 26 and HM 34, respectively, are excellent candidates for fresh market production in Hawaii.”

Although the sweet potato research is not complete, the researchers are now using what data they have already gathered to support the local organic farmers, collaborate with the community, and bring the Hawaiian sweet potato ownership back to the Hawaiian people.

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The beautiful color of the Okinawan purple sweet potatoes has many applications in cooking and is similar to the popular ube, which is a purple yam, and the Okinawan variety has light-colored skin and the ube has a darker skin.

Haupia and the Okinawan sweet potato go well together in a dessert, either as a cheese cake or a bar. This recipe for purple sweet potato cheesecake was printed by KTA Super Stores but given to them courtesy of Hilo Hawaiian Hotel, who could probably be credited for making this dessert very popular.

Purple Sweet Potato Cheesecake

One 9-inch cheesecake

Prepare crust:

Preheat oven to 350 degrees. Mix together

3/4 cup macadamia nuts (finely chopped)

3/4 cup graham cracker crumbs

1 stick melted butter

Pat the crust into a 9-inch springform pan. Bake for 10 minutes in 350-degree oven. Remove the pan from the oven, but leave the oven on.

Place in bowl of mixer and beat until well blended, pour batter over crust in the springform pan:

1-1/2 cups Okinawan purple sweet potatoes (approximately 2 potatoes, steamed and mashed)

1 pound cream cheese

3 large eggs

3/4 cup sugar

1 teaspoon vanilla extract

Mix together in a saucepan, cover over low heat, stirring constantly until haupia is thickened and there are no bubbles:

2 cups coconut milk

1/4 cup sugar

2 cups water

1/2 cup cornstarch

Spread the warm haupia evenly over the top of the cheesecake.

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Hawaii Community College’s Culinary Program’s Cafeteria and Da Ohana Corner Cafe is open from 10:30 am till 12:30 pm Tuesdays through Thursday. For take-out orders call 808-934-2559 for the Cafeteria and 808-934-2591 for Da Ohana Corner Cafe during business hours. Please provide your name, phone number, and pick up time.

Observe the one-way signs in the cafeteria and cafe. Face masks are required.

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Da Ohana Corner Cafe has breakfast selections, salads, burgers, bentos and musubi while the Cafeteria offers hot plate lunches which include rice, vegetables, a fresh baked bread roll and soup.

Email Audrey Wilson at audrey wilson808@gmail.com.

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