Oxidation-driven structural reconfiguration and dynamic covalent assembly behavior of soy protein-oxidized alginate complexes: Tailored engineering for tunable stability of emulsions

Abstract

The objective of this investigation was to explore the structural properties of oxidized sodium alginate (OSA) based on oxidation degree modulation as well as to evaluate the interaction mechanism and emulsification characteristics of soy protein (SPI) and OSA complexes. The results indicated that the degree of oxidation was a critical factor in regulating the structural and functional properties of the SPI-OSA complex. The oxidation degree reached up to 82.08 % at SA:NaIO₄ of 5:5 (w/w). With abundant CO in the sodium alginate (SA) system, the entangled irregular polysaccharide chains degrade into short segments, and the crystallinity decreases. At this point, the incorporation of OSA reduced the free amino acid content in SPI to 77.2 mmol/L, and the system particle size was 214.9 nm. In focus, there was a disruption of the original ordered structure of the SPI by OSA, which contributed to the addition of disordered β-turns and randomly coiled structures. Based on the dynamic Schiff base imine bond, it was possible to form complexes with greater stability and processing properties with SPI and OSA. In particular, the more flexible structure of SPI-OSA showed 76.5 % protein adsorption at the oil-water interface, and the emulsion formed demonstrated smaller droplets and higher stability. This study provided novel thoughts for the construction and exploitation of green and steady emulsion systems.