Insoluble soybean polysaccharides as emulsifiers: Impact of sonication and acidic <scp>pH</scp> on interfacial behaviour and emulsifying properties

BACKGROUND: This study sought to obtain and assess different insoluble soybean polysaccharide (ISPS) fractions from defatted soybean flour for their use as oil-in-water emulsifiers. The primary focus was to examine the influence of specific processing conditions - particularly the timing of sonication - on the physicochemical properties of these fractions and their subsequent ability to stabilise emulsions, elucidating the underlying mechanisms through protein-polysaccharide interactions. RESULTS: ) and enhanced protein solubility compared to ISPS and ISPS-S fractions. Structural changes induced by sonication, such as acid hydrolysis and deamidation, critically improved interfacial activity, significantly reducing interfacial tension even at low concentrations. Consequently, S-ISPS consistently produced emulsions with the smallest average droplet diameters. Conversely, ISPS and ISPS-S formed larger droplets and displayed a higher bulk complex viscosity, indicating the presence of a more robust and compact floc network. All ISPS fractions demonstrated excellent stability against droplet coalescence over 28 days at acidic pH. CONCLUSION: This research highlights that while all fractions are high-potential emulsifiers, the specific processing, particularly the timing of sonication, significantly alters the physicochemical properties of the ISPS fractions and their performance as emulsifying agents. The findings underscore the increased added value of this soybean by-product via synergistic protein-polysaccharide interactions. © 2026 Society of Chemical Industry.