Taking The Green Out of Sunflower Flour

A student in Lilian Senger’s food chemistry lab at Chapman University’s Schmid College of Science and Technology had a problem: Her vegan cookies had turned green. Thinking mold was the culprit, the student threw them out.

But Senger, director of Chapman’s food science program, knew the cookies were too fresh for mold to take hold, and she figured out that the culprit was the sunflower flour the student had subbed in for wheat flour. “Sunflower has a higher phenolic chlorogenic acid content compared to other oil seeds,” explains Senger.

Sunflower meal, or flour, is a byproduct of sunflower oil pressing, and most of it is thrown away, although some is used for animal feed. It is high in protein and fiber, and it also contains antioxidants, mostly in the form of chlorogenic acid. Yet it’s not often used by the food industry, says Senger. One reason is the high fiber content, which can make substituting it for other ingredients difficult. But the main reason is the chlorogenic acid.

Getting the most protein from oil seeds like sunflower requires a high pH process, which increases the protein’s solubility. But with sunflower, it also causes the green color. One way to avoid this coloration is by using an acid extraction process. However, that produces less meal.

But Senger had an idea. “If we break down the chlorogenic acid to caffeic acid and quinic acid, that will probably solve the problem,” she says. With seed funding from the U.S. Department of Agriculture, Senger and biochemist colleague Cedric Owens engineered an enzyme that would separate the chlorogenic assay. They found that the enzyme, from Lactobacillus helveticus, hydrolyzes the chlorogenic acid so when an alkaline extraction is used, the meal is brown instead of green.

The engineered enzyme worked surprisingly well, says Senger. The next step was assessing how consumers feel about enzyme-treated baked products, and how much of an impact the color really made in their buying decisions.

Putting It to the Test

The researchers put together a panel of 153 untrained tasters who were presented with a concept card and two rounds of cookies made with sunflower flour, one treated with the enzyme. To prepare the treated cookie dough, they added the enzyme to the dry ingredients and waited 30 minutes for it to react.

The concept card detailed advantages of sunflower flour, like its nutritional profile, upcycling value, and the fact that it’s free of allergens, to see how important those attributes were to consumers and if that information informed their purchasing intent, says Senger. 

The first set of cookies was comprised of four samples under a green light that masked the cookies’ color. The panelists were directed to sort them into two groups based on similarities but without tasting them. Almost half of the panelists sorted the cookies into treated and untreated.

For the hedonic test, they sampled a second set of cookies. Sometimes the chlorogenic acid imparts a bitter flavor, explains Senger. “We wanted to see when we changed from chlorogenic acid to caffeic acid, are there any flavor and aroma differences between the two,” she says. There were differences, but they were not significant, she adds.

The tasters were then shown photos of the cookies and asked about desire to purchase. The green cookies lost out—the greener the cookies, the less likely the tasters were to say they would buy them. That differed from the ratings given during the concept card stage, when 41% said they would likely buy a cookie made from sunflower flour.

“That supported our hypothesis that appearance definitely does matter in terms of purchasing intent,” she says. “We all know we eat with our eyes first, but I wanted to see exactly how big a deal that was.” 

Because sunflower flour isn’t as soluble as soy flour, it is unlikely to be the first choice for liquid products like protein shakes, but it holds promise for baked goods. Senger cautions that a 30% flour substitution is probably the limit because otherwise the products would be too dense and low in volume. Senger and her colleagues have a provisional patent on the enzyme, and she continues to investigate the phenolic interactions, particularly related to nutrition.ft