Stable nano-sized emulsions produced from soy protein and soy polysaccharide complexes

[Display omitted] ► Soy protein and soy polysaccharide form dispersible complexes in aqueous phase. ► Emulsion produced from the complexes having a droplet size about 250nm. ► Irreversible oil–water interfacial films formed by denatured protein after heating. ► Fixed polysaccharide on the surface stabilizes the oil droplets in aqueous phase. ► Emulsions are stable after long-term storage in pH 2–8 and 0.2M NaCl media. In this research, a simple, green and effective strategy was developed to produce long-term stable oil in water emulsion from soy protein and soy polysaccharide. Soy protein and soy polysaccharide formed dispersible complexes at pH around 3.25 aqueous solution through electrostatic and hydrophobic interactions. A high pressure homogenization produced the protein/polysaccharide complex emulsion having a droplet size about 250nm. A heat treatment of the emulsion resulted in the protein denaturation, forming irreversible oil–water interfacial films composed of soy protein/soy polysaccharide complexes. The droplets of the emulsion were characterized by dynamic light scattering, ζ-potential, transmission electron microscopy, polysaccharide digestion via pectinase, and confocal laser scanning microscopy observation via dual fluorescence probes. As a result of the polysaccharide being fixed on the droplet surface, the emulsions exhibited long-term stability in the media containing pH values of 2–8 and 0.2mol/L NaCl. The stable soy protein/soy polysaccharide complex emulsion is a suitable food-grade delivery system in which lipophilic bioactive compounds can be encapsulated.