Physicochemical characterization and in-vitro digestibility of extruded rice noodles with different amylose contents based on rheological approaches

• Extruded rice noodles with different amylose levels were rheologically investigated.
• High amylose rice (HAR) flour exhibited higher mixing stability and elastic nature.
• HAR noodles exhibited a firmer texture that contributed to their reduced cooking loss.
• HAR noodles showed greater viscosities throughout in-vitro simulated digestion steps.
• Flow curves of noodle digesta consisted of Power-law area and infinite shear plateau.

The physicochemical properties and in-vitro digestibility of extruded rice noodles with different amylose contents were characterized from a rheological point of view. Thermo-mechanical measurements showed that the rice flour with higher amylose contents exhibited greater stability to dual-mixing and higher degrees of starch gelatinization and retrogradation. In addition, greater elastic properties were clearly observed in the high amylose rice samples. The use of high amylose rice flour produced noodles with a harder texture, consequently contributing to reduced cooking loss. Furthermore, the rheological changes of extruded rice noodles were monitored in real time during the in-vitro starch digestion. The rice noodle digesta with higher amylose contents exhibited greater viscosities throughout the simulated oral-gastric-intestinal digestion steps. The flow behaviors of the rice noodle digesta consisted of the Power-law region and infinite shear plateau that were satisfactorily characterized by the Sisko model (R2 > 0.99).