Hierarchical assembly and digestive resistance of starch-unsaturated fatty acid complexes regulated by ultrasound-assisted high-pressure microfluidization

This study elucidates how dynamic high-pressure microfluidization (DHPM) synergistically combined with ultrasound (US) pretreatment regulates the molecular assembly, hierarchical structure, and in vitro digestive behaviors of starch-unsaturated fatty acid (UFA) complexes. Fully gelatinized wheat starch (WS) was complexed with trans-oleic acid (EA)/linoleic acid (LA) and processed by US-assisted DHPM. Distinct digestion behaviors were observed, with WS-LA complexes exhibiting a significantly higher resistant starch (RS) content up to 21% than the EA counterparts. Structural analyses revealed that US pretreatment enhanced amylose chain mobility and promoted the formation of single-helical inclusion structures, while subsequent DHPM intensified starch-lipid interactions and drove the self-assembly of compact supramolecular domains. Owing to its near-linear conformation, EA favored deeper helix insertion and higher V -type crystallinity, whereas LA was associated with fewer but potentially more densely organized nanostructures. Correlation analysis demonstrated that digestive resistance and release rate was governed not only by the extent of inclusion complexation, but more critically by the hierarchical organization of assemblies. These findings provide mechanistic insights into structure-digestibility relationships and offer guidance for designing starch-based systems with tailored digestion properties.