Effect of fatty acid chain length on the structure and digestibility of high-amylose starch-fatty acid and high-amylose starch-fatty acid-whey protein isolate complexes

This study explored the effects of fatty acids with varying chain lengths—lauric acid (LA), palmitic acid (PA), and stearic acid (SA)—on the structure, thermal properties, and digestibility of high-amylose wheat starch (HWS) and HWS-whey protein isolate (WPI) complexes. The aim was to understand the interaction mechanisms and evaluate the potential of HWS-WPI-fatty acid complexes for nanoparticle preparation. Results revealed that fatty acids formed V-type crystalline structures with HWS, weakened its microstructural continuity, and reduced starch digestibility, with differences depending on chain length. LA formed thermally stable II-type complexes with amylopectin's double-helix structure, while SA formed I-type complexes with amylose's single-helix structure, leading to higher resistant starch (RS) content (31.22 %). The addition of WPI promoted the formation of both I-type and II-type complexes, improving crystalline structure, digestion resistance, and RS content. The HWS-WPI-LA complex, with its ordered structure and reduced continuity, produced nanoparticles with smaller size (277.97 nm), narrower distribution (polydispersity 0.241), better dispersibility, and regular morphology compared to other complexes. These nanoparticles also exhibited low cytotoxicity and good biocompatibility. These findings underscore the role of fatty acids in starch-protein interaction and the potential of ternary complexes for developing food-grade nanoparticles with small size and narrow distribution.