Soy glycinin as food-grade Pickering stabilizers: Part. I. Structural characteristics, emulsifying properties and adsorption/arrangement at interface

The development of food-grade Pickering stabilizers has recently attracted growing interests, due to their potential applications in food and pharmaceutical formulations. We report that glycinin (SG), one of major globulins in soy proteins, exhibits a very promising potential to perform as a kind of novel food-grade Pickering stabilizers for oil-in-water emulsions. The unheated SG at pH 7.0 was mainly present in the nanoparticle form (with a z-average diameter of 57 nm), and the heating at 90 or 100 degrees C considerably increased the particle size and surface hydrophobicity (by 5-6 fold) of the nanoparticles. The heating also remarkably changed the pattern of intra-particle interactive forces, and for the heated SG nanoparticles, their internal structure was mainly maintained by both hydrophobic interactions and disulfide bonds. The heating greatly improved the emulsification performance of the nanoparticles, especially at high concentrations (e.g. >0.5%, w/v), as well as the stability of the corresponding emulsions against coalescence and creaming. As compared with the SG preparation heated at 90 degrees C, that at 100 degrees C exhibited a higher effectiveness to pack at the interface. The better emulsification performance for the heated SG preparations was closely associated with their more efficient packing and higher diffusion (or initial adsorption) at the interface. The results indicated that SG nanoparticles, unheated or heated, could be applied as a kind of Pickering stabilizers for oil-in-water emulsions; as compared to the unheated SG, the heated SG nanoparticles exhibited much better interfacial and emulsifying properties, thus imparting a better Pickering stabilization for the emulsions. (C) 2015 Elsevier Ltd. All rights reserved.