Influences of feed moisture on the structure and physicochemical properties of high amylose corn starch-flax oil complexes during extrusion

Starch-lipid complexes were prepared by using high amylose corn starch (HACS) and flax oil (FL) via the extrusion process, and the effects of feed moisture on the structure and physicochemical properties of HACS-FL complexes were investigated. Fourier transform infrared spectroscopy and morphology observation identified that the complexes were successfully prepared. The complex index (CI) revealed that the feed moisture possessed a significant effect ( P < 0.05) on the complexation of the starch and flax oil, with the highest CI value (59.96%) when the moisture content was at 40%. X-ray diffraction results suggested that the complexes exhibited V-type crystalline and their relative crystallinity was dependent on the feed moisture. Additionally, the feed moisture played a decisive role in the type of complexes, consequently regulating their digestibility properties. In summary, this study facilitates the application of extrusion in the preparation of starch-lipid complexes, which can be further used to design anti-digestion starchy foods. • High amylose corn starch-flax oil complexes were produced by the extrusion process. • Feed moisture affected complex index by regulating the amylose content in complexes. • Lower feed moisture favored the formation of the type I complex in the complexes. • I n vitro digestibility of complexes were dependent on the feed moisture content.