Structure-digestibility relationship of starch inclusion complex with salicylic acid

Amylose, the linear component of starch, can complex with small molecules to form single helical inclusion complexes of 6, 7, or 8 glucosyl units per helical turn, known as V6, V7, and V8. In this study, starch-salicylic acid (SA) inclusion complexes with different amounts of residual SA were obtained. Their structural characteristics and digestibility profiles were obtained with complementary techniques and an in vitro digestion assay. Upon complexation with excess SA, V8 type starch inclusion complex was formed. When excess SA crystals were removed, the V8 polymorphic structure could remain, while further removing intra-helical SA converted the V8 conformation to V7. Furthermore, the digestion rate of the resulted V7 was lowered as indicated by increased resistant starch (RS) content, which could be due to its tight helical structure, whereas the two V8 complexes were highly digestible. Such findings could have practical implications for novel food product development and nanoencapsulation technology.