Probing soy protein-aldehyde binding by inverse liquid chromatography on protein-packed columns

Protein-flavor interactions strongly influence the sensory quality of plant-based foods. However, rapid methods for comparing binding behavior under controlled dynamic conditions remain limited. In this study, an inverse liquid chromatography (ILC) method was developed to investigate interactions between six aldehydes (pentanal to decanal) and soy protein isolate (SPI). An SPI-based stationary phase was prepared by physically mixing SPI with diol-functionalized silica to provide mechanical bed stability. Flavor retention provided insights into binding percentages, thermodynamic parameters, and adsorption mechanisms. Binding increased with aldehyde chain length, reaching up to 96%. The ΔG for pentanal to octanal ranged from -17.0 to -26.0 kJ·mol^-1, indicating spontaneous and chain-length-dependent interactions. Thermodynamic analysis revealed a shift from enthalpy-driven binding for short-chain aldehydes to entropy-driven binding for longer chains, highlighting the contribution of hydrophobic effects. Adsorption followed a Henry type isotherm. ILC provides a rapid and complementary approach for probing protein-flavor adsorption behavior in plant-based protein systems.