High-amylose starch with uniquely low retrogradation: The key role of altered protein-starch interface

The high retrogradation properties of high amylose starch (HAS) have restricted its use in food applications, as it negatively affects product attributes such as staling and short shelf life. This study proposed the hypothesis that reduced retrogradation and higher resistant starch content in HAS can be obtained by modifying the starch granular surface (starch-protein interface) through four distinct approaches: Ca²⁺/Mg²⁺-induced protein aggregation, polysaccharide complexation, pH-driven hydrophobic interactions of proteins and enzymatically-catalyzed covalent bonding. The results showed that the modification with CaSO₄ and soy protein isolate (β-conglycinin and glycinin) effectively optimizes the protein-starch interface in HAS to simultaneously reduce retrogradation and improve enzymatic resistance. The modification resulted in a 17.3 % increase of resistant starch content from the initial value of HAS, and reduced V_max. The results emphasize that the types and components of starch-protein interface play a critical role in regulating the retrogradation properties and enzymatic resistance of HAS, in addition to granular protein content. The findings enable the design of low-glycemic starch ingredients with uniquely low retrogradation.