Impact of rutin-protein nanoparticles on extruded recombinant rice: structure, digestibility and in vitro fermentation.

Abstract

Background: Rutin, a flavonol polyphenol, inhibits α-glucosidase activity and reduces starch digestibility, yet its application is limited by poor aqueous solubility, poor thermal stability, and low bioaccessibility. Rutin-protein nanoparticles have been shown to improve rutin stability. This study aimed to investigate how rutin-protein nanoparticles modulate the digestibility of extruded recombinant rice through multi-scale structural characterization, in vitro digestibility analysis, and in vitro fermentation evaluation.

Results: Multi-scale structural analysis revealed that rutin was successfully incorporated into the recombinant rice matrix, interacting with starch chains through hydrogen bonding. This interaction promoted the transformation of starch crystallinity from A-type to A- + V-type. Additionally, the short-range order and the content of single and double helices increased. In vitro digestion experiments demonstrated that the bioaccessibility of rutin in the recombinant rice reached 92.49% after co-extrusion with rutin nanoparticles. The resistant starch content was significantly increased, while C_∞ (final digestion extent) and eGI (estimated glycemic index) value were significantly reduced. Moreover, in vitro fermentation results indicated that the recombinant rice with rutin nanoparticles contributed to reducing gas production and increasing the yields of propionate and butyrate.

Conclusion: Rutin nanoparticles modulate starch digestibility through a dual mechanism involving the modification of starch structural domains and rutin bioaccessibility. This study provides a novel strategy and technical support for the development of low-glycemic-index functional staple foods. © 2026 Society of Chemical Industry.