Fabrication and characterization of high internal phase pickering emulsions using soy protein isolate and chitooligosaccharide complexes in acidic conditions

Currently, significant challenges remain in the development of natural protein-stabilized emulsions. Soy protein isolate (SPI) has poor emulsifying property compared to relatively flexible proteins. This study investigated the use of chitooligosaccharide (COS) to enhance the emulsifying properties of SPI for the preparation of high internal phase Pickering emulsions (HIPPEs) at pH 3, while systematically analyzing the underlying mechanism. The results demonstrated that COS supplementation effectively improved the emulsification characteristics of SPI, leading to COS-SPI-based HIPPEs with superior emulsion performance. Optimal emulsion stability and microstructure were achieved at a COS:SPI ratio of 1:5, yielding HIPPEs with the most stable network structure and smallest droplet size. Mechanistic studies revealed that COS facilitated the formation of a thicker interfacial layer and enhanced SPI adsorption at the oil-water interface, thereby creating a more densely packed emulsion structure. The resulting COS-SPI-based HIPPEs exhibited remarkable thermal and centrifugal stability. Further investigation of the COS-SPI interaction mechanism identified non-covalent binding as the predominant mode of molecular interaction. This research establishes an effective strategy for developing compound emulsifiers capable of stabilizing HIPPEs under acidic conditions, offering valuable insights for food application. • COS improved the emulsification of SPI under acidic conditions. •COS-SPI -based HIPPEs exhibited excellent thermal and centrifugal stabilities at pH3. •COS-SPI -based HIPPEs possessed solid-like gel properties. •Electrostatic and hydrophobic forces are the main forces between COS and SPI.