Modulating the assembly of starch-lecithin inclusion complexes and its underlying mechanism for controlling starch digestibility under the dense system

Starch-lipid inclusion complexes were used to regulate starch digestibility by changing the binding affinity of digestive enzymes such as α-amylase and α-glucosidase. However, when above a critical aggregation concentration (CAC) of starch and lipid molecules, they tended to self-assemble into double helices or normal micelles respectively, rather than interacting with each other to form starch-lipid complexes. Thus, how to enhance the complexation efficiency under a dense system is the key approach for the improvement of starch bioaccessibility and nutritional function. Herein, based on the dimethyl sulfoxide (DMSO) reverse solvent method, the effect of water/DMSO ratios and starch chain structures on the interaction and assembly behaviors between starch and lecithin molecules in high concentrations were systematically investigated. The results revealed that water/DMSO in a ratio of 1.5:1 promoted the interactions between cavities of starch helices and long alkyl chains of lecithin molecules, with higher level of complexed lecithin content, relative crystallinity (RC), enthalpy (ΔH) (T p ＞100 °C), ordered-aggregation structures and resistant starch (RS) content. In this kind of solvent, starch samples with higher content of amylose and longer chains (degree of polymerization (DP) of B 2 chains and B 3+ chains) is advantageous to the formation of VII-type inclusion starch-lecithin complexes, with a rise in RS from 14.17% to 43.64%. It provided an effective method to modulate starch digestibility under the dense system of starch and lecithin via modulating the water/DMSO ratios and starch fine structures and lay the foundation for the large-scale preparation and application of starch-lecithin complexes.