Fabrication of rutin-protein complexes to form and stabilize bilayer emulsions: Impact of concentration and pretreatment

In present study, the impact of rutin concentration and pretreatment (direct mixing versus pH-driven) of rutin-protein complexes to form and stabilize bilayer emulsions was examined. Bilayer emulsions prepared using the pH-driven method contained smaller oil droplets and had a higher resistance to aggregation and creaming than those prepared using the direct method. The concentration of whey protein isolate at the oil droplet surfaces decreased as the rutin concentration was increased. The oil-water interfacial tension decreased as the rutin concentration in the rutin-whey protein isolate complexes increased, reaching a value of 10.4 mN/m at 0.6 mg/mL rutin. Fluorescence spectroscopy suggested that rutin interacted with the whey protein isolate surfaces mainly through hydrophobic interactions. Moreover, there appeared to be more binding sites and stronger binding interactions when the pH-driven method was used to form the complexes, rather than the direct mixing method. This study suggests that rutin may be used to improve the functional performance of whey protein isolate as emulsifiers in bilayer emulsions.