Effects of Euryale ferox dietary fiber on the rheological, thermal, and digestive properties of its starch

Euryale ferox (Qian Shi) is a dual-purpose botanical resource with both medicinal and nutritional value. This study investigated the effects of Euryale ferox dietary fiber (EDF), including its soluble fraction (ESDF) and insoluble fraction (EIDF), on the structural, rheological, thermal, and digestive properties of Euryale ferox starch (EFS). FTIR results showed that EDF addition enhanced the short-range molecular order of starch, whereas X-ray diffraction indicated that the crystalline structure remained largely unchanged. These results suggest that hydrogen bonding and physical association may contribute to starch–fiber interactions without markedly disrupting the long-range crystalline architecture, although direct molecular-level validation is still required. Rheological analysis demonstrated that both ESDF and EIDF reduced the apparent viscosity and viscoelastic moduli of starch paste. In addition, EDF altered the thermal behavior of EFS, with gelatinization temperatures showing a concentration-dependent trend. More importantly, EDF decreased the rapidly digestible starch fraction while increasing the slowly digestible and resistant starch fractions, indicating improved digestion resistance. These findings provide a basis for the development and value-added utilization of Euryale ferox -based functional foods with potential low-glycemic properties.