Winegrape pomace—the material left after pressing the grapes—used to be dumped in vineyards or composted for soil amendments.
But at least one Washington company is looking at the waste product as a source of healthful cooking ingredients, according to a news release.
Gena McKahan, a Washington State University food science undergraduate, looked at how different amounts of merlot grape-seed flour would affect a granola bar's antioxidant content when baked with other ingredients.
Grape-seed flour is made by separating out seeds in the pomace to press for oil.
The remaining press cake—compressed seed solids left over after pressing—are milled into the flour.
McKahan made granola bars with 0 percent 5 percent, 10 percent and 15 percent grape-seed flour.
The bars were gluten free and also included buckwheat, rice, teff seed and potato starch flavor.
A consumer panel of 60 people tasted the bars and said they preferred those containing 0 percent and 5 percent grape-seed flour.
Because grape-seed pomace is astringent or bitter, bars with the higher content were not as palatable.
The research also confirms previous work by WSU sensory analyst Carolyn Ross and researcher Maria Rosales that suggests that even bars with lower amounts of grape-seed flour still had more than zero antioxidant content.
The merlot grape-seed flour used in McKahan's research was donated by Eric Leber, co-owner and president of AprèsVin of Yakima.
Leber is a strong proponent of using the entire grape, including the material left after pressing for win.
About 8 million tons of grape pomace are produced worldwide each year, according to the release.