Impact of extraction methods on soybean hull polysaccharides: structure and functional properties analysis

Soybean hull polysaccharides (SHP) exhibit diverse functional properties, yet the influence of extraction methods on their structure-function relationships remains unclear. This study investigated microwave-assisted extraction (M), extractant-assisted (citric acid, MC; sodium citrate, MS), and extractant-enzyme (cellulase/pectinase)-assisted (MCC, MCP, MSC, MSP). The results show that the M have a relatively high extraction yield (3.39 %) and carbohydrate content (92.64 %) compared with others. MS have the highest glucuronic acid content (41.60 %). Structural analysis revealed that M, MC, MCC, and MCP produced RG-I-type pectins with high branching degrees (12.85-16.71), whereas MS, MSP, and MSC generated predominantly linear homogalacturonan (HG) domains (linearity: 1.51-1.81). Moreover, Na⁺ combined with higher HG domains reduced electrostatic repulsion and promoted polysaccharide alignment at the oil-water interface, leading to superior emulsifying activity (277.48 m²/g) and stability (6232.07 min) in MS. These findings clarify SHP structure-function relationships and provide guidance for tailoring polysaccharide properties through optimized extraction strategies.