Chlorogenic Acid Oxidation and Its Reaction with Sunflower Proteins to Form Green-Colored Complexes

Sunflower seeds are used to produce oil for human consumption, but its protein meal by-product has long been used as animal feed. Formation of green-colored complexes through oxidized chlorogenic acid(CGA)-protein interactions is a primary reason why defatted sunflower protein has not been widely utilized by the food industry. Sunflower protein possesses many properties that make it an appealing alternative protein source from both a marketing and formulation perspective, including its low cost, absence of major allergens, low antitrypsin inhibitors, and its status as both vegan and "clean" label friendly. With the global demand for sunflower oil and novel protein sources expected to increase and waste recovery a concern for many, providing uses for the sunflower meal and its fiber and polyphenol components would provide added value to by-products from sunflower oil processing. This review addresses the unique green pigmentation associated with the interaction of sunflower protein and oxidized CGA by outlining the sunflower oil and protein meal market, CGA reactions contributing to greening, methods for CGA extraction, and the effect of processing on sunflower protein quality and the greening reaction. This review also addresses potential food applications of sunflower protein-based ingredients, such as addition of texturized protein to food products; a microencapsulation matrix for antioxidants; edible, flexible biodegradable films; and even use of sunflower butter as an alternative to peanut butter where the green color is not considered undesirable. Continued studies are needed to make sunflower-based products and CGA-extraction processes available across the global marketplace.