Formulating white rice with low-glycemic index potential: The effect of low-acyl gellan gum on textural properties...

White rice is a staple food worldwide, yet its high glycemic index (GI), driven by rapidly digestible starch, raises significant public health concerns. This study explores the application of low-acyl gellan gum (LAGG) as a bio-macromolecular strategy to modulate starch digestibility while preserving desirable textural properties in cooked rice. Two rice types, jasmine rice (JR, high-GI) and parboiled rice (PR, low-GI), were cooked with 0-3% LAGG and systematically analyzed using a multi-scale approach, including thermal properties at grain and starch levels, microstructural features in raw and cooked forms, and texture and digestibility at the whole grain level, reflecting typical consumption conditions. Microstructural evaluation of cooked rice revealed that LAGG formed a hydrogel coating on rice grains, enhanced β-sheet protein structures and promoted the formation of starch-LAGG complexes. These structural modifications strengthened the protein-starch matrix, particularly in JR. As a result, hardness (8-26%) and chewiness (1.4-2.3×) increased in JR, while minimal effects were observed in PR. In-vitro starch digestibility analysis showed that LAGG addition reduced starch hydrolysis, shifting digestion toward slower and resistant fractions and lowering predicted GI by 10-22% across LAGG levels (1-3%), with JR showing a stronger response. When integrated with microstructural and thermal observations, these results are consistent with reduced enzymatic accessibility to starch. Collectively, these findings offer mechanistic insights into LAGG as a distinct hydrocolloid capable of reinforcing rice structure and lowering glycemic impact through multi-scale interactions, supporting its practical and scalable application in the development of healthier rice-based foods.