Stabilization of Pickering emulsions by oxidized starch/zein nanoparticle complexes

Abstract

In this study, oxidized starch (OS)/zein nanoparticles (ZNP) complexes were prepared and used to stabilize Pickering emulsions. The effect of starch oxidation using three levels of sodium hypochlorite (2.0%, 3.0%, 4.0% active chlorine, dry basis) on the properties of OS/ZNP complexes and complex-stabilized Pickering emulsions were evaluated. The interaction between oxidized starch and zein nanoparticles was confirmed by X-ray diffractometry (XRD) and Fourier transform infrared (FT-IR) spectrometry. The presence of oxidized starch improved the wettability of OS/ZNP complexes. The optimum contact angle (θ) of OS/ZNP complexes was 90.88°, when starch was oxidized with 3.0% active chlorine (3.0% OS). The appearance, micromorphology and oil droplet-size distribution suggested that OS/ZNP complex-stabilized Pickering emulsions were formed. Rheological measurements indicated that Pickering emulsions showed shear-thinning behavior. Furthermore, the viscoelasticity of Pickering emulsions was dependent on the oxidized starch and oil fractions. Stability test showed that the stability of Pickering emulsion can be improved by increasing the oil fraction from 20% to 50%, and Pickering emulsion stabilized by 3.0% OS/ZNP complexes had the highest stability. This work provides information on OS/ZNP complex-stabilized Pickering emulsions.