Effects of inulin with different polymerization degrees on rice starch digestibility under extrusion with the...

Inulin effectively modulated starch digestibility, though its functional performance varies depending on preparation methods and starch matrices. In this study, rice starch-protein-inulin complexes were prepared by extrusion to investigate the effect of inulin with different degrees of polymerization on the digestibility of rice starch in the presence of protein. In vitro digestion results indicate that adding 6 % short-chain inulin and 9 % long-chain inulin increased the resistant starch content in the complex from 20.69 % to 25.23 % and 26.35 %, respectively. The stronger physical encapsulation of long-chain inulin reduced the estimated glycemic index from 77.17 to 70.61. Scanning electron microscopy and molecular docking studies indicated that inulin forms hydrogen-bonded aggregates with starch, reducing enzyme accessibility. The maximum complexation indices for short-chain and long-chain inulin with starch reached approximately 55.06 % and 52.60 %, respectively. Rheological, hydration, and thermodynamic properties indicate that inulin reduces the viscoelasticity and solubility of the composite while increasing the gelatinization temperature and decreasing the enthalpy value. XRD, FTIR, and LC-Raman spectroscopy results indicate that inulin addition disrupts the ordered arrangement of starch chains, inhibits the rearrangement process of starch chains, and reduces the structural order of starch. Overall, incorporating inulin, especially long-chain types, effectively inhibits starch digestibility by altering its molecular interactions and structure, providing a potential strategy for developing low-glycemic rice-based foods.