Association of Natural Amylose into Different Forms of Aggregates: Structure and Potential Mechanisms

The aggregated structure of natural amylose (AM) plays an important role in the functionality of starch. However, the formation and structure of such AM aggregates remain to be elucidated. In this study, four forms of AM (amorphous AM, retrograded AM, ethanol-precipitated crystalline AM, and AM-lauric acid (LA) complexes) were characterized to distinguish differences in their structures. Amorphous AM was characterized as having no short- and long-range molecular order, whereas retrograded AM contained imperfect B-type crystalline structures made up of some stacked double helical segments of AM chains. Both ethanol-precipitated crystalline AM and AM-LA complexes showed a V-type crystalline structure, which was formed by the arrangement of AM single helices that were empty or had encapsulated LA, respectively. This study provides fresh insights into the formation and structure of four forms of AM aggregates, which have significance for a better understanding of the role of AM aggregates in starch functionality for applications.