Dynamic Regulation of Beany Off‐Aroma Adsorption by Protein Concentration: Mechanistic Insights From Soy Protein‐Hexanal Interactions

Interactions between proteins and flavor compounds are essential for the perception of flavor in foods and the regulation of food quality. In this work, headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS), coupled with relative odor activity value (ROAV) analysis, identified hexanal as a major volatile compound with the highest ROAV, suggesting its potential as a key contributor to the beany off-flavor in soymilk. Circular dichroism, particle size, tertiary structure, and molecular docking were used to reveal the adsorption behavior of different soy protein isolate (SPI) concentrations on hexanal, the key beany flavor substance in soymilk. The results show that at an SPI-hexanal ratio of 20:2, the adsorption rate was maximal, accompanied by maximal SPI particle size, greatest degree of secondary structure extension, and exposure of hydrophobic groups. Analysis of tertiary structure dynamics revealed concentration-dependent conformational changes during adsorption. Molecular docking analysis identified three distinct binding modes: the hydrophobic cavity, the groove located between the α-helix and β-sheet, and surface-exposed sites. Of these, the hydrophobic cavity emerged as the most favorable binding mode, demonstrating the lowest binding energy at -4.5 kcal/mol. Hydrogen bonding and hydrophobic interactions significantly enhanced SPI stability post-adsorption. This work elucidate the dynamic regulatory mechanism of protein concentration on flavor adsorption, providing theoretical guidance for flavor improvement in soy products.