Soybean 7S and 11S globulins respond differently to ohmic heating: Linking structural unfolding and oil-water interfaces

Emerging technologies have been widely applied to modify complex protein systems; however, their effects are generally evaluated at the whole-protein level, limiting the understanding of the mechanisms governing individual protein fractions. Soy protein functionality is primarily determined by the β-conglycinin (7S) and glycinin (11S) fractions, yet their distinct responses to ohmic heating and consequent interfacial performance remain poorly understood. In this study, isolated 7S and 11S fractions were subjected to ohmic heating under different electric field strengths (control, 35, 40, 45, and 50 V∙cm −1 ) and evaluated for electrothermal properties, secondary structure, free sulfhydryl groups, surface hydrophobicity, ζ-potential, particle size, solubility, interfacial adsorption, and emulsion stability using 1-octanol, medium-chain triglycerides (MCT), and n-octane as oil phases. Ohmic heating induced fraction-dependent structural changes by modulating protein unfolding and aggregation. The 7S fraction showed greater conformational sensitivity, with increased free sulfhydryl content, α-helix to β-sheet conversion, and particle growth from approximately 0.4 to 2.7 μm, whereas 11S maintained comparatively stable soluble protein levels across most ohmic-heating conditions. These structural changes translated into distinct interfacial behaviors depending on the oil phase. MCT provided the most favorable balance between adsorption kinetics, emulsion stability, and rheological structuring, particularly for the 11S fraction treated at intermediate electric field strengths, whereas n-octane promoted stronger hydrophobic interactions and flocculation, and 1-octanol produced less structured emulsions. These findings demonstrate that ohmic heating can selectively tailor the structural and interfacial functionality of soybean protein fractions, providing new insights for designing protein ingredients with targeted emulsifying properties.