A novel method for interfacial protein extraction with enhanced emulsification characteristics: Soybean oil bodies...

This study systematically investigated the impact of various salt ions (Na⁺ and Mg²⁺) on the extraction efficiency of soybean oil bodies (OBs), as well as on the structure and function of their interfacial proteins. The extraction rates, determined by aqueous extraction combined with salt-ion-assisted grinding: the highest extraction rate (56.73%) was achieved with 0.5 mol/L Na⁺, while a similarly elevated rate (46.45%) was obtained with 0.5 mol/L Mg²⁺ compared to the ion-free control. Structural analyses employing circular dichroism and Fourier-transform infrared spectroscopy demonstrated that salt ions modulated protein conformation through electrostatic shielding: Na⁺ promoted a transition from α-helix to β-sheet, whereas Mg²⁺ strengthened hydrophobic interactions and induced protein aggregation. Furthermore, emulsification properties assessed via emulsification activity index (EAI) and emulsion stability index (ESI) showed a concentration-dependent behavior: low concentrations of Na⁺ (≤0.5 mol/L) and Mg²⁺ (≤0.1 mol/L) improved both EAI and ESI by neutralizing surface charges, while higher ion concentrations reduced emulsification performance due to salting-out effects. Collectively, these findings establish a clear structure-function relationship: salt ion-assisted grinding enhances oil body extraction yields and induces conformational changes in interfacial proteins that regulate the stability of the resulting emulsions. Thus, this study provides a mechanistic foundation for the efficient extraction and functional application of plant-derived OBs.