Microwave-mediated formation of lotus-seed starch-palmitic acid complexes and their multi-scale structural changes

Recent studies have revealed that starch-lipid complexation can significantly impact gut health via the formation of V-type resistant starch. This study used varying microwave (MW) power levels (600, 700, 800, 900, 1000 W) to prepare V-type lotus-seed starch (LS)-palmitic acid (PA) complexes and investigates their multi-scale structural and thermal properties. The results indicate that MWs promote hydrophobic LS-PA complexation to form a B + V_6II-type crystalline structure, with the V-type complexation rate found to positively correlate with MW power. Specifically, a higher MW power is more conducive to guiding the evolution of the disordered structure in the complex system back to the ordered arrangement and enhancing the crystallinity and stability of the system. The evolution of this V-type crystallization process peaks at an MW power of 1000 W MW to afford a complexing index of 55.409 %. Further thermal-property analyses reveal that the V-type complexed starch is mainly arranged as highly thermally stable accumulated single-helix structures that dissociate at 100-105 °C. These findings provide valuable data for regulating V-type complex formation through MW treatment and establish a theoretical foundation for precisely designing healthy starch-based foods.