Effect of debranching on the formation and in vitro digestibility of high amylose maize starch-C18 unsaturated fatty acid complexes

There is a big challenge in the efficient preparation of starch-unsaturated fatty acid (FA) complexes due to the steric hindrance of unsaturated FAs. This study aimed to understand the effects of debranching of high-amylose maize starch (HAMS) on the formation, structure and in vitro enzymic digestibility of complexes prepared with C18 unsaturated FAs. Debranching treatment of HAMS generated linear glucan chains and enhanced the encapsulation efficiency and loading capacity of FAs, particularly for the treatment of 12 h. Meanwhile, debranching treatment, especially for 12 h, greatly enhanced the long- and short-range ordered structure as well as the thermal stability of complexes, and decreased the in vitro enzymic digestibility. Molecular dynamics simulations showed that the van der Waals forces between amylose (AM) and stearic acid (SA) was stronger than those between AM and three unsaturated FAs, which may account for the higher degree of crystallite perfection of starch-SA complexes. Correlation analyses showed that the degree of crystallite perfection of the complexes was the main determinant for the rate and extent of complex digestion. Our study shows clearly that a certain degree of debranching can significantly promote the formation of starch-unsaturated FA complexes with higher degree of structural order and lower enzymic digestibility, which may be of interest for the efficient preparation of starch-unsaturated FA complexes to deliver health benefits.