An investigation into the structure and digestibility of starch-oleic acid complexes prepared under various...

In the present study, we investigated the effects of complexing temperatures (75 °C and 95 °C) and oleic acid (OA) content (2%, 6%, 10% and 14%, w/w, dry basis of starch) on the structure and in vitro digestibility of maize starch-OA complexes. The resistant starch content, complexing index, thermal transition temperatures, enthalpy change and relative crystallinity of the complexes prepared at 75 °C were higher than those of corresponding complexes prepared at 95 °C. Additionally, starch-10% OA complexes prepared at 75 °C had the highest resistant starch content (18.82%), complexing index (78.83%) and relative crystallinity (14.62%). Fourier transform infrared spectroscopy revealed that the intermolecular interactions between starch and OA were affected by the complexing temperatures and OA content. Raman spectroscopy indicated that the starch-10% OA complexes prepared at 75 °С had a greater short-range molecular order than other complexes. The V-type complexes were further confirmed as V_6III polymorph structures according to the spectra obtained by nuclear magnetic resonance spectroscopy. Therefore, we conclude that complexing temperatures and OA content greatly changed the fine structure of the complexes, which further affected their digestibility.