Structural Factors That Determine the Amylolytic Properties of Starch-Lipid Complexes

Structural factors that determine the amylolysis of starch-lipid complexes have remained unclear. Understanding the relationship between the structure and amylolysis of starch-lipid complexes is important for the design and preparation of complexes with predictable digestibility. In this study, the multiscale structures and amylolytic properties of complexes formed under different conditions between debranched high-amylose starch (DHAMS) and lauric, myristic, palmitic, and stearic acids were investigated. Higher complexing temperatures facilitated the formation of DHAMS-fatty acid (FA) complexes, especially the more stable type II crystallites. Longer complexing times also promoted the formation of complexes and the type II crystallites, except for DHAMS-lauric acid (LA). Molecular dynamics simulations showed that the binding free energy for the formation of DHAMS-LA complexes (10 kJ/mol) was lower than those for the other three DHAMS-FA complexes (20-50 kJ/mol), accounting for the lower stability of DHAMS-LA complexes at longer complexing times. The rate and extent of enzymatic digestion of the DHAMS-FA complexes were much lower in comparison to those of gelatinized HAMS. Correlation analyses showed that the rate and extent of enzymic digestion of DHAMS-FA complexes were mainly determined by the degree of crystallite perfection of the complexes.