Study on the interaction between succinylated soy protein isolate and chitosan and its utilization in the development of oil-in-water bilayer emulsions

Electrostatic interactions between proteins and polysaccharides can be used to form oil-in-water bilayer emulsions. The strength of this electrostatic force influences the properties of the emulsions. In this study, the interaction between succinylated soy protein isolate (SSPI) and chitosan (CS) was investigated and exploited to develop oil-in-water bilayer emulsions. The oil phase was corn oil, and the bilayer emulsion was assembled via layer-by-layer (LBL) electrostatic deposition. The isoelectric point (pI) of SPI was reduced by succinylation. Spectral analysis indicated that succinylation unfolded the spatial structure of SPI. The interaction between SPI or SSPI and CS was dominated by electrostatic force. Succinylation increased the binding sites between SSPI and CS and enhanced the electrostatic force between them. Microstructure observation revealed that bilayer emulsion-based SSPI had a tighter network structure than bilayer emulsion-based SPI. A bridge-like 3D network structure formed between the primary emulsion droplets and CS. The results of this study demonstrated that SSPI is more suitable than SPI for bilayer emulsion preparation. These findings have important implications for protein- and polysaccharide-stabilized, emulsion-based LBL models. This study also provides a new material for the preparation of delivery systems that protect biologically active compounds. Bilayer emulsions are promising for applications in traditional and manufactured food products.