Digestibility properties and supramolecular structure of starch prepared by high hydrostatic pressure and α-amylase treatment

Abstract

Riceberry starch, a promising ingredient for functional foods, has limited digestibility and functionality in its native form. While high hydrostatic pressure (HHP) and enzymatic treatment are known to modify starch properties, their combined effects on Riceberry starch remain underexplored. This study investigated the synergistic impact of HHP (200–600 MPa) and α-amylase treatment on the in vitro digestibility, morphostructural, thermal, and rheological properties of riceberry starch, aiming to identify optimal processing conditions for tailored starch functionality. Starch was treated at 200 MPa (α200), 400 MPa (α400), and 600 MPa (α600) for 10 min, followed by α-amylase hydrolysis (30 U mg⁻¹) for 360 min. Compared to enzyme-only control (RBα), HHP above 200 MPa significantly reduced starch content and long-chain amylopectin branching. Digestibility varied with pressure: α200 showed higher rapidly digestible starch (RDS: 30.16%) and slowly digestible starch (SDS: 54.19%), whereas α600 yielded more resistant starch (RS: 38.22%). Microstructural analysis revealed larger clusters (112.69 µm) and lower specific surface area (0.25 m² g⁻¹) for α600, explaining its reduced digestibility. Although the crystalline structure (type A) was retained, relative crystallinity declined (α600: 24.88%). Higher HHP intensities (α600) increased thermal resistance to gelatinization and viscosity, demonstrating pressure-dependent rheological modifications. HHP at 200–400 MPa combined with α-amylase optimally balanced digestibility and functional properties, offering a targeted approach to tailor riceberry starch for food applications requiring specific thermal, rheological, or digestive profiles.