Influence of nanocomplexation with curcumin on emulsifying properties and emulsion oxidative stability of soy protein isolate at pH 3.0 and 7.0

Although the complexation between proteins and phenol compounds has been widely investigated for improved stability and delivery of those compounds, especially those with low solubility and bioavailability, few works are available addressing the influence on the functional properties of the proteins. The work investigated the influence of complexation with curcumin at pH 3.0 and 7.0 on the emulsifying properties and emulsion oxidative stability of soy protein isolate (SPI). At both test pH values, most of proteins in SPI were present in the nanoparticle form, with larger sizes, higher surface hydrophobicity and better emulsifying properties of these nanoparticles observed at pH 3.0. However, the emulsions at pH 3.0 were much more susceptible to lipid oxidation. The SPI at both pH values easily interacted with curcumin to form complexes at nanoscale, through hydrophobic interactions. The complexation at both pH values slightly changed the particle size, the absolute xi-potential and emulsifying properties of the protein, but remarkably decreased their surface hydrophobicity. Furthermore, the complexation distinctly accelerated the lipid oxidation of the emulsions at both pH values. The results would be of importance for the development of functional soy protein ingredients enriched with some bioactive compounds. (C) 2016 Elsevier Ltd. All rights reserved.