In Vitro Digestibility and Predicted Glycemic Index of Chemically Modified Rice Starch by One‐Step Reactive Extrusion

Abstract

Abstract The in vitro digestibility of chemically modified rice starch by one‐step reactive extrusion (REX) via esterification, acetylation, hydroxypropylation, and cross‐linking or dual‐modification (hydroxypropylation‐cross‐linking and acetylation‐cross‐linking) is investigated. After REX processing, pasting viscosity is decreased, while the viscosity of esterification samples is lower than that of cross‐linking samples. Molecular structure analysis suggests that the degradation of starch molecules is retarded by esterification whereas enhanced by cross‐linking. Dual modification (hydroxypropylation and phosphorylation, hydroxypropylation‐cross‐linking (HP‐CL) sample) involving hydroxypropylation and phosphorylation (HP‐CL sample) is more conducive to preventing enzyme hydrolysis than the other modifications. HP‐CL sample achieves the lowest predicted glycemic index (pGI) value (88.1) and the highest RS content (15.3%). Thus, the one‐step REX is a useful method for reducing rice starch digestibility or pGI value.