Efficient sorption of polyphenols to soybean flour enables natural fortification of foods

The present study demonstrated that defatted soybean flour (DSF) can sorb polyphenols from blueberry and cranberry juices while separating them from sugars. Depending on DSF concentration and juice dilution, the concentration of blueberry anthocyanins and total polyphenols sorbed to DSF ranged from 2–22 mg/g and 10–95 mg/g, respectively while the concentration of anthocyanins and proanthocyanidins in cranberry polyphenol-enriched DSF ranged from 2.5–17 mg/g and 21–101 mg/g, respectively. Blueberry polyphenols present in one serving of fresh blueberries (73 g) were delivered in just 1.4 g of blueberry polyphenol-enriched DSF. Similarly, one gram of cranberry polyphenol-enriched DSF delivered the amount of proanthocyanidins available in three 240 ml servings of cranberry juice cocktail. The concentration of blueberry anthocyanins and total polyphenols eluted from DSF remained constant after 22 weeks of incubation at 37 °C, demonstrating the high stability of the polyphenol–DSF matrix. LC–MS analysis of eluates confirmed that DSF retained major cranberry and blueberry polyphenols intact. Blueberry polyphenol-enriched DSF exhibited significant hypoglycaemic activities in C57bl/6J mice, and cranberry polyphenol-enriched DSF showed antimicrobial and anti-UTI activities in vitro, confirming its efficacy. The described sorption process provides a means to create protein-rich food ingredients containing concentrated plant bioactives without excess sugars, fats and water that can be incorporated in a variety of scientifically validated functional foods and dietary supplements.