Preparation of Zein-Nicandra physaloides Gum Binary Complex and Its Application in Pickering Emulsions

Zein is widely used in loading and delivery of food functional components due to its unique self-assembly properties. However, due to the strong hydrophobicity, the interface stability of the pure Zein-based Pickering emulsion is difficult to meet the needs of practical applications, and the construction of a composite system with appropriate polysaccharides is an effective strategy to improve the stability of its emulsion. On account of this, composite particles (NZPs) using Zein and Nicandra physaloides gum (NPG) with different protein-polysaccharide compounding ratios were prepared in this work by complex coacervation method. The physicochemical properties, structure and emulsion properties of NZPs were characterized. The results showed that the surface wettability of NZPs increased with the increasing addition of NPG, and meanwhile the formed composite particles became smaller with better dispersity, caused by the specific electrostatic force between protein and polysaccharide. The endogenous fluorescence spectrum of NZPs showed that the peak intensity of the corresponding characteristic peaks was proportional to the content of Zein and NPG, respectively, and the introduction of NPG affected the microenvironment polarity of tyrosine residues in Zein molecules. The shift of the absorption peak in Fourier transform infrared spectroscopy (FT-IR) indicated the enhanced hydrogen bond interaction and the generation of new peaks indicated the formation of new chemical bonds in NZPs. The storage modulus (G') of NZPs-based Pickering emulsions was higher than the loss modulus (G"). When the compounding ratio was 1:1 (Zein:NPG), both G' and G" of emulsions reached the maximum, obtaining the optimum emulsion system structure. The creaming index (CI) results showed that the stability of NZPs-based Pickering emulsions was generally higher than that of the pure Zein or NPG emulsions under different pH and heating treatments. This study provides a theoretical reference for the development of new Zein-polysaccharide composite system and its highly efficient and stable Pickering emulsions.